Download - 128252036-Xfh-on-Line-Help
August 2006
Heat Transfer Research, Inc. 150 Venture Drive College Station, Texas 77845 USA © Heat Transfer Research, Inc.
Xfh® 5.0 Online Help
printed version
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Fired Heater (Xfh) Online Help Table of Contents
August 2006 © Heat Transfer Research, Inc. All rights reserved. Page iii Confidential: For HTRI member use only.
Table of Contents
Overview .......................................................................................................................................................1
Before You Get Started ............................................................................................................................. 1
Special Cases............................................................................................................................................ 3
Buried Tubes in Firebox......................................................................................................................... 3
Arbor or U-Tubes ................................................................................................................................... 3
Boilers .................................................................................................................................................... 4
Sloped or Hip Roof................................................................................................................................. 5
Case Configuration Panel ......................................................................................................................... 5
Case type............................................................................................................................................... 5
Radiant section type .............................................................................................................................. 6
Convection section................................................................................................................................. 6
Case....................................................................................................................................................... 6
Problem.................................................................................................................................................. 6
Name Panel............................................................................................................................................... 7
Case description .................................................................................................................................... 7
Problem description ............................................................................................................................... 7
Job number ............................................................................................................................................ 8
Item number........................................................................................................................................... 8
Reference number ................................................................................................................................. 8
Proposal number.................................................................................................................................... 8
Revision ................................................................................................................................................. 9
Service ................................................................................................................................................... 9
Customer ............................................................................................................................................... 9
Plant location ......................................................................................................................................... 9
Remarks............................................................................................................................................... 10
Ambient Air Conditions Panel.................................................................................................................. 10
Ambient air pressure............................................................................................................................ 10
Ambient air temperature ...................................................................................................................... 11
Ambient air moisture............................................................................................................................ 11
Clear Selected Property....................................................................................................................... 11
Clear All Properties.............................................................................................................................. 11
Clear All Heat Release Data................................................................................................................ 11
Clear All Temperature Data ................................................................................................................. 11
Insulation specification......................................................................................................................... 12
Heat release entry type........................................................................................................................ 12
Table of Contents Fired Heater (Xfh) Online Help
Page iv © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.
Flow basis for heat release curve........................................................................................................ 12
API530 Module............................................................................................................................................13
API530 Summary Panel .......................................................................................................................... 15
Tube Design option.............................................................................................................................. 15
Tube life evaluation.............................................................................................................................. 15
Tube type (for tube design).................................................................................................................. 16
Tube outside diameter ......................................................................................................................... 16
Tube inside diameter ........................................................................................................................... 16
Tube wall thickness.............................................................................................................................. 17
Tube metallurgy ................................................................................................................................... 17
Rupture stress curve............................................................................................................................ 18
Print metal properties for inspection .................................................................................................... 19
Physical Properties for User-Specified Metallurgy Panel........................................................................ 20
Metal identification ............................................................................................................................... 20
Type of material ................................................................................................................................... 21
Poisson's ratio...................................................................................................................................... 21
Specific gravity..................................................................................................................................... 21
Limiting design metal temperature....................................................................................................... 22
Lower critical temperature ................................................................................................................... 22
Material constant A per Table 2........................................................................................................... 22
L-M constant C per Appendix A.3........................................................................................................ 23
Yield stress .......................................................................................................................................... 23
Modulus of elasticity............................................................................................................................. 23
Thermal expansion .............................................................................................................................. 24
Thermal conductivity ............................................................................................................................ 24
Rupture stress...................................................................................................................................... 24
Inside Heat Transfer Coefficient Panel.................................................................................................... 25
Tube length between return bends...................................................................................................... 25
Total mass flow rate for all passes ...................................................................................................... 26
Number of tubepasses......................................................................................................................... 26
Fluid pressure ...................................................................................................................................... 26
Weight fraction vapor........................................................................................................................... 26
TEMA fouling factor ............................................................................................................................. 27
Specific heat ........................................................................................................................................ 27
Thermal conductivity ............................................................................................................................ 27
Density ................................................................................................................................................. 27
Viscosity............................................................................................................................................... 28
Temperature ........................................................................................................................................ 28
Specific heat ........................................................................................................................................ 28
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Thermal conductivity ............................................................................................................................ 28
Density ................................................................................................................................................. 29
Viscosity............................................................................................................................................... 29
Metal Temperature Parameters Panel .................................................................................................... 30
Fluid bulk temperature ......................................................................................................................... 30
Inside heat transfer coefficient............................................................................................................. 30
Coke thickness..................................................................................................................................... 31
Coke thermal conductivity.................................................................................................................... 31
Heat Flux Parameters Panel ................................................................................................................... 32
Tube Flux Type .................................................................................................................................... 33
Center-to-center spacing ..................................................................................................................... 33
Average heat flux around tube............................................................................................................. 33
Fraction transferred by convection ...................................................................................................... 34
Planar peak-to-average factor ............................................................................................................. 34
Operating Conditions Panel .................................................................................................................... 35
Tube identification................................................................................................................................ 35
Maximum design pressure (elastic) ..................................................................................................... 35
Maximum operating pressure at Start of Run...................................................................................... 36
Maximum operating pressure at End of Run ....................................................................................... 36
Metal temperature at Start of Run ....................................................................................................... 36
Metal temperature at End of Run......................................................................................................... 37
Maximum local peak flux ..................................................................................................................... 37
Design life for stress ............................................................................................................................ 37
Corrosion allowance ............................................................................................................................ 37
Run length between SOR and EOR .................................................................................................... 38
Tube Life Evaluation Panel ..................................................................................................................... 39
Tube life evaluation.............................................................................................................................. 39
Initial tube life....................................................................................................................................... 40
On-stream time .................................................................................................................................... 40
Operating pressure (Start of Run) ....................................................................................................... 40
Operating pressure (End of Run)......................................................................................................... 40
Metal temperature (Start of Run)......................................................................................................... 41
Metal temperature (End of Run) .......................................................................................................... 41
Corrosion rate ...................................................................................................................................... 41
Required tube life................................................................................................................................. 41
On-stream time per period................................................................................................................... 42
Box Heater Module .....................................................................................................................................43
Box Heater Summary Panel.................................................................................................................... 45
Box Heater Type Selection .................................................................................................................. 45
Table of Contents Fired Heater (Xfh) Online Help
Page vi © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.
Height (H)............................................................................................................................................. 46
Width (W) ............................................................................................................................................. 46
Depth (D) ............................................................................................................................................. 46
Flue Gas Opening Dimension A .......................................................................................................... 47
Flue Gas Opening Dimension B .......................................................................................................... 47
Height (T) ............................................................................................................................................. 47
Width (U).............................................................................................................................................. 47
Width (V) .............................................................................................................................................. 48
Gas Configuration Panel ......................................................................................................................... 50
Gas Space Configuration ID ................................................................................................................ 51
w1, w2, w3 ........................................................................................................................................... 51
Gas Space Definitions ......................................................................................................................... 51
Configurations with Identical Gas Spaces ........................................................................................... 52
Burner Locations Panel ........................................................................................................................... 55
Burner location/firing direction ............................................................................................................. 55
Number of symmetric sections ............................................................................................................ 56
Number of Burners in Each Gas Space .............................................................................................. 56
Local Coordinate X/Y/Z........................................................................................................................ 56
Space from Last Burner....................................................................................................................... 57
Along Axis ............................................................................................................................................ 57
Valid Burner Coordinates..................................................................................................................... 57
Burner Parameters Panel........................................................................................................................ 58
Effective Flame Length ........................................................................................................................ 58
Minimum Jet Opening.......................................................................................................................... 58
Entrance Gas Velocity ......................................................................................................................... 59
Planar Half Jet Angle ........................................................................................................................... 59
Heat Release Factor/Burner ................................................................................................................ 59
Nominal Pressure Drop ....................................................................................................................... 59
F........................................................................................................................................................... 60
A........................................................................................................................................................... 60
B........................................................................................................................................................... 60
K........................................................................................................................................................... 61
Burner Group ....................................................................................................................................... 61
Burner Code List button....................................................................................................................... 61
Burner Code Panel .................................................................................................................................. 62
Tube Locations Panel.............................................................................................................................. 63
Tube Coil Exists ................................................................................................................................... 63
Number of Tube Sections .................................................................................................................... 63
Tube Orientation .................................................................................................................................. 64
Inside Return Bend .............................................................................................................................. 64
Fired Heater (Xfh) Online Help Table of Contents
August 2006 © Heat Transfer Research, Inc. All rights reserved. Page vii Confidential: For HTRI member use only.
Tube Section Geometry Panel ................................................................................................................ 65
Figure button........................................................................................................................................ 65
DX, DY, DZ .......................................................................................................................................... 66
Tube Outside Diameter........................................................................................................................ 66
Tube Wall Thickness ........................................................................................................................... 67
Tube Ctr-Ctr Spacing........................................................................................................................... 67
Tube Length......................................................................................................................................... 67
Tube Metallurgy ................................................................................................................................... 67
Tube Thermal Conductivity.................................................................................................................. 67
Number of Tubes ................................................................................................................................. 68
Maximum Tube Length ........................................................................................................................ 68
Wall Size (Available) ............................................................................................................................ 68
Wall Size (Required)............................................................................................................................ 68
Box Heater Tube Coil Geometry.......................................................................................................... 69
Tubepass Sequence Panel ..................................................................................................................... 71
Number of process passes .................................................................................................................. 71
Set process pass ................................................................................................................................. 72
Set tube number .................................................................................................................................. 72
Clear Current Pass .............................................................................................................................. 72
Clear All Passes................................................................................................................................... 72
Tube Flow Direction Panel ...................................................................................................................... 73
Gas Space ........................................................................................................................................... 73
Gas Space Wall ................................................................................................................................... 74
Wall Tube Section................................................................................................................................ 74
Process Pass....................................................................................................................................... 74
Pass Sequence.................................................................................................................................... 74
1st Tube Flow Direction ....................................................................................................................... 74
Process Methods Panel........................................................................................................................... 75
Heat Transfer Coefficient Method........................................................................................................ 75
Pure Component.................................................................................................................................. 76
Film Boiling Check ............................................................................................................................... 76
Critical heat flux ................................................................................................................................... 76
Fraction of critical flux for film boiling................................................................................................... 77
Sensible liquid coefficient .................................................................................................................... 77
Sensible vapor coefficient.................................................................................................................... 77
Boiling coefficient................................................................................................................................. 77
Process fluid coefficient multiplier........................................................................................................ 78
Tubeside friction factor ........................................................................................................................ 78
Process fluid friction factor multiplier ................................................................................................... 78
Surface roughness............................................................................................................................... 78
Table of Contents Fired Heater (Xfh) Online Help
Page viii © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.
Insulation Specification Panel ................................................................................................................. 79
Number of Layers ................................................................................................................................ 79
Same as Front End.............................................................................................................................. 80
Same as Left Side................................................................................................................................ 80
Minimum/maximum temperature ......................................................................................................... 80
Maximum outside wall temperature..................................................................................................... 80
Average wind velocity .......................................................................................................................... 80
Material Thickness............................................................................................................................... 81
Material Code....................................................................................................................................... 81
User Defined Materials... ..................................................................................................................... 82
Optional Panel ......................................................................................................................................... 85
Pressure in heater................................................................................................................................ 85
Flue gas soot extinction coefficient...................................................................................................... 86
Mean beam length ............................................................................................................................... 86
Process tube emissivity ....................................................................................................................... 87
Refractory surface emissivity............................................................................................................... 87
Convection weighting factors............................................................................................................... 87
Momentum width factor for gas flow.................................................................................................... 88
Initial gas zone temperature estimate.................................................................................................. 88
Initial refractory temperature estimate ................................................................................................. 88
Stack Panel ............................................................................................................................................. 90
Available Stack Items .......................................................................................................................... 90
Stack Items List.................................................................................................................................... 90
Add New Stack Item ............................................................................................................................ 90
Insert New Stack Item.......................................................................................................................... 91
Delete Stack Items............................................................................................................................... 91
Reorder Stack Items ............................................................................................................................ 91
Soot extinction coefficient .................................................................................................................... 91
Distance to first tuberow ...................................................................................................................... 91
Bridgewall temperature estimate ......................................................................................................... 92
Stack Inlet Geometry - Shape.............................................................................................................. 92
Stack Inlet Geometry - Width............................................................................................................... 92
Stack Inlet Geometry - Depth .............................................................................................................. 92
Feed Stream to Radiant Section.......................................................................................................... 92
Bundle Panel ........................................................................................................................................... 93
Bundle layout type ............................................................................................................................... 93
Heated tube length............................................................................................................................... 94
Parallel passes (Convection) ............................................................................................................... 94
Parallel elements (Stack)..................................................................................................................... 94
Tubepasses ......................................................................................................................................... 95
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Bundle width ........................................................................................................................................ 96
Tube layout .......................................................................................................................................... 96
Reverse staggered rows...................................................................................................................... 96
Process inlet ........................................................................................................................................ 96
Corbels................................................................................................................................................. 97
Use ESCOA outside methods ............................................................................................................. 97
Bundle Layout Panel ............................................................................................................................... 98
User-defined tubepass layout .............................................................................................................. 98
Number of tuberows............................................................................................................................. 99
Number of tubes in each row / Number of tubes per row.................................................................... 99
Left wall clearance / Clearance, wall to first tube ................................................................................ 99
Stack Element Panels ............................................................................................................................. 99
Stack element height ......................................................................................................................... 100
Stack element length ......................................................................................................................... 100
Stack element orientation .................................................................................................................. 100
Stack element flow direction .............................................................................................................. 101
Stack element fitting loss coefficient.................................................................................................. 101
Stack element pressure drop............................................................................................................. 102
Stack element relative roughness...................................................................................................... 102
Stack element miter pieces................................................................................................................ 103
Stack element friction factor .............................................................................................................. 103
Stack element outlet geometry - shape ............................................................................................. 103
Stack element outlet geometry - depth.............................................................................................. 104
Stack element outlet geometry - width .............................................................................................. 104
Stack element outlet geometry - diameter......................................................................................... 104
Stack element bend radius ................................................................................................................ 104
Stack element take-off angle ............................................................................................................. 105
Tube Types Panel ................................................................................................................................. 106
Tube name......................................................................................................................................... 106
Tube internal ...................................................................................................................................... 106
Add tube type..................................................................................................................................... 107
Delete tube type................................................................................................................................. 107
Tubes page ........................................................................................................................................ 107
FJ Curves page.................................................................................................................................. 114
Outside/airside f- and j-factors........................................................................................................... 115
Tubeside f- and j-factors .................................................................................................................... 115
Low Fins page.................................................................................................................................... 117
Fin material ........................................................................................................................................ 117
High Fins page................................................................................................................................... 118
Stud Fins page................................................................................................................................... 119
Table of Contents Fired Heater (Xfh) Online Help
Page x © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.
Fin bond resistance............................................................................................................................ 119
Fin efficiency...................................................................................................................................... 120
Number of stud rings ......................................................................................................................... 120
Number of studs in each ring............................................................................................................. 120
Stud length......................................................................................................................................... 120
Stud diameter..................................................................................................................................... 121
Twisted Tape page ............................................................................................................................ 121
Thickness........................................................................................................................................... 121
L/D 360-degree twist.......................................................................................................................... 122
Width.................................................................................................................................................. 122
Tube Sink Definition Panel .................................................................................................................... 123
Fraction sink....................................................................................................................................... 123
Emissivity of sink................................................................................................................................ 124
Fraction open..................................................................................................................................... 124
Convective weight factor.................................................................................................................... 124
Sink temperature................................................................................................................................ 124
Enter data for wall .............................................................................................................................. 124
Reset Current Wall............................................................................................................................. 125
Reset All Walls................................................................................................................................... 125
Radiant Box Panel................................................................................................................................. 125
Heater type ........................................................................................................................................ 125
Number of tubepasses....................................................................................................................... 126
Number of radiant tubes .................................................................................................................... 126
Height................................................................................................................................................. 126
Width.................................................................................................................................................. 126
Depth ................................................................................................................................................. 126
Diameter ............................................................................................................................................ 127
Specified ............................................................................................................................................ 127
Heat loss ............................................................................................................................................ 128
Outside convective heat transfer coefficient...................................................................................... 128
Tube Zones Panel ................................................................................................................................. 128
First tube in zone ............................................................................................................................... 129
Tube position ..................................................................................................................................... 129
Tube firing .......................................................................................................................................... 129
Tube outside diameter ....................................................................................................................... 131
Tube inside diameter ......................................................................................................................... 131
Center-to-center spacing ................................................................................................................... 131
Heated lengths................................................................................................................................... 131
Tube thermal conductivity.................................................................................................................. 131
Tube emissivity .................................................................................................................................. 131
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Coke thickness................................................................................................................................... 132
Coke thermal conductivity.................................................................................................................. 132
Process fouling factor ........................................................................................................................ 132
Longitudinal max/avg flux ratio .......................................................................................................... 132
Radiant Box Process Conditions Panel................................................................................................. 133
Fluid name ......................................................................................................................................... 133
Process flow rate ............................................................................................................................... 133
Pressure............................................................................................................................................. 133
Bulk temperature................................................................................................................................ 134
Bulk temperature at wall .................................................................................................................... 134
Weight fraction vapor......................................................................................................................... 134
Thermal conductivity .......................................................................................................................... 134
Viscosity............................................................................................................................................. 134
Viscosity at wall.................................................................................................................................. 135
Specific heat ...................................................................................................................................... 135
Combustion Module ..................................................................................................................................137
Combustion Panel ................................................................................................................................. 139
Number of fuels.................................................................................................................................. 139
Oxidant type....................................................................................................................................... 139
Diluent type ........................................................................................................................................ 140
Fuel type ............................................................................................................................................ 140
Fuel Gas Calculation Options............................................................................................................ 140
Flue gas temperature......................................................................................................................... 141
Radiant duty....................................................................................................................................... 141
Heat loss ............................................................................................................................................ 141
Fuel Oil Panel ........................................................................................................................................ 142
Pressure............................................................................................................................................. 142
Flow ................................................................................................................................................... 143
Temperature ...................................................................................................................................... 143
Lower heating value........................................................................................................................... 143
Characterization factor....................................................................................................................... 143
Higher heating value.......................................................................................................................... 144
Ultimate Analysis by Mass %............................................................................................................. 144
Normalize........................................................................................................................................... 144
API - Degree API ............................................................................................................................... 144
GR - Grade ........................................................................................................................................ 145
SG - Specific gravity .......................................................................................................................... 145
Oxidant Air Panel................................................................................................................................... 146
Oxidant flow ....................................................................................................................................... 146
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Oxidant flow rate................................................................................................................................ 146
Oxidant flow units............................................................................................................................... 147
Excess oxidant................................................................................................................................... 147
Incomplete Combustion ..................................................................................................................... 147
Oxidant pressure................................................................................................................................ 148
Oxidant temperature .......................................................................................................................... 148
Oxidant moisture................................................................................................................................ 148
Oxidant Gas Panel ................................................................................................................................ 149
Oxidant composition units.................................................................................................................. 149
Oxidant composition .......................................................................................................................... 150
Add..................................................................................................................................................... 150
Delete................................................................................................................................................. 150
Order.................................................................................................................................................. 150
Normalize........................................................................................................................................... 150
Diluent Panel ......................................................................................................................................... 150
Diluent pressure................................................................................................................................. 150
Diluent temperature ........................................................................................................................... 151
Diluent flow units................................................................................................................................ 151
Diluent flow rate ................................................................................................................................. 151
Diluent weight fraction liquid .............................................................................................................. 152
Gas Panel.............................................................................................................................................. 152
Fuel composition units ....................................................................................................................... 153
Fuel composition................................................................................................................................ 153
Normalize........................................................................................................................................... 153
Liquid/Solid Panel.................................................................................................................................. 154
Pressure............................................................................................................................................. 154
Temperature ...................................................................................................................................... 154
Flow ................................................................................................................................................... 155
Lower heating value........................................................................................................................... 155
Higher heating value.......................................................................................................................... 155
Characterization factor....................................................................................................................... 155
Ultimate Analysis by Mass %............................................................................................................. 156
Normalize........................................................................................................................................... 156
Convection Module ...................................................................................................................................157
Distance from heater roof to center of first tuberow .......................................................................... 157
Left wall clearance ............................................................................................................................. 158
Transverse pitch ................................................................................................................................ 158
Longitudinal pitch............................................................................................................................... 158
Tube outside diameter ....................................................................................................................... 158
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Tube wall thickness............................................................................................................................ 159
Tube type ........................................................................................................................................... 159
Tube material code ............................................................................................................................ 159
Tube thermal conductivity.................................................................................................................. 159
Heated tube length............................................................................................................................. 160
Unheated length/row.......................................................................................................................... 160
Unheated length between rows ......................................................................................................... 160
Tube emissivity .................................................................................................................................. 160
Fins Panels............................................................................................................................................ 161
More Information on Fins Panels....................................................................................................... 161
Load from Databank .......................................................................................................................... 163
Databank type.................................................................................................................................... 163
Tube dimensions................................................................................................................................ 164
Fins/length ......................................................................................................................................... 164
Fin root diameter................................................................................................................................ 164
Fin height ........................................................................................................................................... 165
Fin thickness...................................................................................................................................... 165
Outside area/length ........................................................................................................................... 165
Wall thickness under fins ................................................................................................................... 165
Fin material ........................................................................................................................................ 166
Setting loss ........................................................................................................................................ 166
Process Conditions Panel ..................................................................................................................... 166
Flow rate ............................................................................................................................................ 167
Phase condition ................................................................................................................................. 167
Inlet temperature................................................................................................................................ 168
Outlet temperature............................................................................................................................. 168
Inlet fraction vapor ............................................................................................................................. 168
Outlet fraction vapor .......................................................................................................................... 168
Process duty ...................................................................................................................................... 169
Inlet pressure ..................................................................................................................................... 169
Allowable pressure drop .................................................................................................................... 169
Process fouling layer thickness ......................................................................................................... 169
Process fouling factor ........................................................................................................................ 170
Flue gas fouling factor ....................................................................................................................... 170
Stream name ..................................................................................................................................... 170
Estimated inlet fraction vapor ............................................................................................................ 170
Estimated inlet temperature............................................................................................................... 171
Estimated inlet pressure .................................................................................................................... 171
Unset Bank Fin .................................................................................................................................. 171
Bank fin code ..................................................................................................................................... 172
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Fin type .............................................................................................................................................. 172
Fin density.......................................................................................................................................... 173
Over fin diameter ............................................................................................................................... 174
Thermal conductivity .......................................................................................................................... 174
Fin bond resistance............................................................................................................................ 174
Fin efficiency...................................................................................................................................... 175
Split segment height .......................................................................................................................... 175
Split segment width............................................................................................................................ 175
Length ................................................................................................................................................ 175
Width.................................................................................................................................................. 176
Fin base thickness ............................................................................................................................. 176
Fin tip thickness ................................................................................................................................. 176
Cylindrical Module.....................................................................................................................................179
Cylindrical Heater Panel........................................................................................................................ 180
Outside diameter................................................................................................................................ 180
Wall thickness .................................................................................................................................... 181
Roof thickness ................................................................................................................................... 181
Height................................................................................................................................................. 181
Floor thickness................................................................................................................................... 181
Type of roof opening.......................................................................................................................... 182
Roof opening length........................................................................................................................... 182
Roof opening width ............................................................................................................................ 182
Roof opening diameter ...................................................................................................................... 182
Roof opening inside diameter ............................................................................................................ 183
Roof opening outside diameter.......................................................................................................... 183
Configuration Panel ............................................................................................................................... 184
Tube circle diameter .......................................................................................................................... 184
Number of parallel passes ................................................................................................................. 185
Process outlet location....................................................................................................................... 185
Burner circle diameter........................................................................................................................ 185
Number of burners............................................................................................................................. 185
Burner nozzle diameter...................................................................................................................... 185
Burner flue gas velocity ..................................................................................................................... 186
Location of burner center from X-axis................................................................................................ 186
Flame length ...................................................................................................................................... 186
Half jet angle from vertical ................................................................................................................. 187
Tube Geometry Panel ........................................................................................................................... 187
Number of different tube sizes and/or C-C spacing per pass............................................................ 187
Outside diameter................................................................................................................................ 188
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Nominal outside diameter .................................................................................................................. 188
Wall thickness .................................................................................................................................... 188
Tube wall thickness schedule ............................................................................................................ 189
Tube metallurgy ................................................................................................................................. 189
Number of tubes in 1 pass................................................................................................................. 190
Center-center spacing ....................................................................................................................... 190
Effective tube length .......................................................................................................................... 190
Thermal conductivity .......................................................................................................................... 191
Duty basis .......................................................................................................................................... 191
Specified duty .................................................................................................................................... 191
Average radiant flux........................................................................................................................... 192
Number of convection fluids included in specified duty ..................................................................... 192
Insulation Loss Coefficient Panel .......................................................................................................... 193
Insulation heat loss coefficients ......................................................................................................... 194
Emissivities Panel.................................................................................................................................. 194
Flue gas extinction coefficient............................................................................................................ 195
Mean beam length ............................................................................................................................. 195
Process tube emissivity ..................................................................................................................... 195
Refractory surface emissivity............................................................................................................. 196
Roof sink surface emissivity .............................................................................................................. 196
Roof sink surface temperature........................................................................................................... 196
Flue Gas Circulation Panel.................................................................................................................... 197
Induced flow factor............................................................................................................................. 197
Maximum recirculation factor............................................................................................................. 198
Burner throat pressure drop constant................................................................................................ 198
Pressure in heater.............................................................................................................................. 199
Weighting factors for convective heat transfer .................................................................................. 200
Output Reports..........................................................................................................................................201
Output Summary ................................................................................................................................... 202
Run Log ................................................................................................................................................. 203
Data Check Messages .......................................................................................................................... 204
Runtime Messages................................................................................................................................ 205
Input Reprint .......................................................................................................................................... 206
Combustion Diagram............................................................................................................................. 207
Combustion Stream Properties ............................................................................................................. 208
Flue Gas Heat Release ......................................................................................................................... 209
Process Heat Transfer Coefficient ........................................................................................................ 210
Metal Temperature ................................................................................................................................ 211
Thickness Design .................................................................................................................................. 212
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Life Evaluation ....................................................................................................................................... 214
Metal Properties .................................................................................................................................... 217
Convection Summary ............................................................................................................................ 219
Convection Flue Gas Monitor................................................................................................................ 220
Convection Process Monitor ................................................................................................................. 220
Heater Temperature Profile................................................................................................................... 221
Cylindrical Firebox Monitor .................................................................................................................... 222
API560 Specification Sheet................................................................................................................... 223
Gas Space Energy Balance .................................................................................................................. 224
Flue Gas Flow Monitor .......................................................................................................................... 225
Box Heater Firebox Monitor .................................................................................................................. 226
Burner Monitor....................................................................................................................................... 228
Flow Distribution Monitor ....................................................................................................................... 229
Gas Temperature Monitor ..................................................................................................................... 230
Tube Flux Monitor.................................................................................................................................. 231
Cylindrical Heater Profile....................................................................................................................... 232
NOx Conversion Factors ................................................................................................................... 234
Box Heater Firebox Tables.................................................................................................................... 235
Cylindrical Firebox Tables ..................................................................................................................... 236
Stack Monitor......................................................................................................................................... 236
Property Monitor .................................................................................................................................... 237
No Tube Flux Monitor ............................................................................................................................ 238
Single-Zone Firebox Monitor ................................................................................................................. 240
Stream Properties.................................................................................................................................. 241
Box Tube Numbers................................................................................................................................ 244
Cylindrical Radiant Section Energy Balance......................................................................................... 246
Test Cases ................................................................................................................................................247
Test Case 1 ........................................................................................................................................... 249
Results ............................................................................................................................................... 250
Output ................................................................................................................................................ 251
Test Case 2 ........................................................................................................................................... 252
Results ............................................................................................................................................... 253
Output ................................................................................................................................................ 253
Test Case 3 ........................................................................................................................................... 254
Output ................................................................................................................................................ 255
Test Case 4 ........................................................................................................................................... 265
Results ............................................................................................................................................... 266
Output ................................................................................................................................................ 267
Test Case 5 ........................................................................................................................................... 268
Fired Heater (Xfh) Online Help Table of Contents
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Results ............................................................................................................................................... 269
Output ................................................................................................................................................ 270
Test Case 6 ........................................................................................................................................... 271
Results ............................................................................................................................................... 272
Output ................................................................................................................................................ 273
Test Case 7 ........................................................................................................................................... 274
Results ............................................................................................................................................... 282
Output ................................................................................................................................................ 283
Frequently Asked Questions.....................................................................................................................285
About This Version....................................................................................................................................291
Boiling Methods..................................................................................................................................... 293
Version 5.0......................................................................................................................................... 293
Calculation Procedures ......................................................................................................................... 293
Version 5.0......................................................................................................................................... 293
Version 4.0 Service Pack 3................................................................................................................ 294
Version 4.0 Service Pack 2................................................................................................................ 295
Version 4.0 Service Pack 1................................................................................................................ 296
Version 4.0......................................................................................................................................... 296
Version 3.0 Service Pack 2................................................................................................................ 299
Version 3.0 Service Pack 1................................................................................................................ 299
Version 3.0......................................................................................................................................... 301
Version 2.0 Service Pack 2................................................................................................................ 303
Version 2.0 Service Pack 1................................................................................................................ 305
Version 2.0......................................................................................................................................... 306
Data Input and Data Check ................................................................................................................... 308
Version 5.0......................................................................................................................................... 308
Version 4.0 Service Pack 3................................................................................................................ 308
Version 4.0 Service Pack 1................................................................................................................ 309
Version 3.0......................................................................................................................................... 309
External Interfaces................................................................................................................................. 310
Version 5.0......................................................................................................................................... 310
Graphical Interface ................................................................................................................................ 311
Version 5.0......................................................................................................................................... 311
Version 4.0 Service Pack 1................................................................................................................ 312
Version 4.0......................................................................................................................................... 312
Version 3.0 Service Pack 3................................................................................................................ 314
Version 3.0 Service Pack 2................................................................................................................ 314
Version 3.0 Service Pack 1................................................................................................................ 316
Version 3.0......................................................................................................................................... 316
Table of Contents Fired Heater (Xfh) Online Help
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Version 2.0 Service Pack 2................................................................................................................ 318
Version 2.0 Service Pack 1................................................................................................................ 320
Version 2.0......................................................................................................................................... 322
Miscellaneous........................................................................................................................................ 324
Version 5.0......................................................................................................................................... 324
Version 4.0......................................................................................................................................... 325
Version 3.0 Service Pack 1................................................................................................................ 325
Version 3.0......................................................................................................................................... 325
Program Outputs ................................................................................................................................... 327
Version 5.0......................................................................................................................................... 327
Version 4.0 Service Pack 1................................................................................................................ 329
Version 4.0......................................................................................................................................... 329
Version 3.0 Service Pack 3................................................................................................................ 331
Version 3.0 Service Pack 1................................................................................................................ 331
Version 3.0......................................................................................................................................... 331
Version 2.0 Service Pack 2................................................................................................................ 333
Radiation Methods................................................................................................................................. 333
Version 5.0......................................................................................................................................... 333
Version 4.0 Service Pack 1................................................................................................................ 334
Glossary ....................................................................................................................................................335
Index..........................................................................................................................................................339
Fired Heaters (Xfh) Online Help Overview
August 2006 © Heat Transfer Research, Inc. All rights reserved. Page 1 Confidential: For HTRI member use only.
Overview
Xfh simulates the behavior of fired heaters. The program calculates the performance of the radiant
section for cylindrical and box (cabin) heaters and the convection section of fired heaters. It also designs
process heater tubes using API 530 and performs combustion calculations.
You can use Xfh to
troubleshoot plant problems
evaluate competing vendor designs
evaluate proposed changes to revamp old heaters for a new service
evaluate the addition of an economizer and/or air preheater to improve plant energy efficiency
evaluate the effect of proposed changes in plant operating conditions on furnace operation, including
the retirement life of tubes based on past and projected operations
Xfh contains different calculation modules to simulate the different parts of a fired heater. You can run
these modules separately or in combination to model part or all of a fired heater.
Note
Xfh is installed with a Program Control Language (PCL) Command Reference Guide (PCL.pdf),
located in the same directory as other help files. You can use PCL to specify any geometric
configuration not currently supported in the Xfh graphical user interface.
Before You Get Started
Before running Xfh, collect the input data you’ll need to run the case. Check the lists below for the
information you’ll need for each module type.
API530
Tube dimensions and material
Operating pressure
Process fluid temperature
One of
– Maximum tube wall temperature
– Process fluid properties
– Process heat transfer coefficient
Circumferential average or maximum heat flux
Overview Fired Heaters (Xfh) Online Help
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Box/Cylindrical
Conceptually, the box and cylindrical heaters require the same type of input. However, the tube coil
geometry is more complex in the box heater because the process path can flow from one wall to the
other and between gas spaces. This increased complexity requires you to map the process flow path
through the physical tube layout.
Heater geometry
Tube coil geometry
Burner throat size, jet angle, and flame length
Process condition of process fluid
Physical properties or composition of process fluid
Combustion
Composition (gas) or properties (liquid/solid) of fuels
Percent excess oxidant
Amount of diluent if present
Flow rate or desired heat release of fuel
Convection
Geometry of convection bundles
Geometry of stack ducting (if stack draft calculation is desired)
Physical properties or composition of process fluids
Process conditions of process fluids
Note
To model a standalone convection section, you also need
flue gas temperature, pressure, and flow rate
flue gas composition or physical properties
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Special Cases
Most cases modeled using the Xfh interface are straightforward. However, a number of heaters/geometry
types require additional explanation.
Buried Tubes in Firebox
Simulating buried tubes (e.g., water tubes located on the floor of a boiler) involves specifying the
appropriate heat loss coefficients on the appropriate firebox wall. In the graphical interface (GUI), these
coefficients are located on the Heat Loss Coefficients panel. When using PCL, you enter the values on
the INSR 1 record. See PCL.pdf for details on calculating these coefficients.
The heat to the buried tubes would then be the heat loss reported through the wall with the buried tubes.
Note
If you are running this case in the GUI, no process-side calculations are performed on the buried
tubes.
Arbor or U-Tubes
Xfh can model arbor or U-tube heaters. The approach used depends upon whether there are burners
outside the vertical U-tube legs.
Burners Between and Outside Vertical U-Tube Legs
In this case, burners are present on both sides of the vertical U-tube legs on the front wall. To
create this type of geometry, select Arbor, U-tube, or inverted U-tube on the initial Box Heater
Type panel. Then input the case as if only a single gas space is present.
Internally, Xfh divides the heater into three gas spaces as shown here.
Overview Fired Heaters (Xfh) Online Help
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Floor Firing or Burners Only Between Vertical U-Tube Legs
If the box heater is floor-firing or does not have burners in the areas labeled GS1 and GS3, do not
use the U-tube option. Instead, model the box heater as a single-cell top opening heater. Treat
the legs of the U-tube as tubes on the left, right, and top (or bottom) as shown here.
Specify the lengths of the horizontal and vertical legs so that the total tube area is the same as
the actual U-tube.
Limitations
The current program version is limited to a maximum of 100 tubepasses. For typical flow
arrangements, you are limited to a maximum of 100 U-tubes in a single run. You can model box
heaters with more tubes by taking advantage of symmetry and modeling only part of the heater.
Xfh issues a warning message if you attempt to specify U-tubes and firing from both end-walls.
The calculation engine does not allow this configuration; you must model it using symmetry.
Boilers
You can perform an approximate model of a boiler using the No tubes option on the Box Heater summary
panel.
The main difference in modeling a boiler and process heater is that you do not define the individual tubes
in the boiler but rather assign a fraction of radiant sink area on each wall of the boiler. This is termed a
“no-tubes layout.” See the No Tube Flux Monitor section in Output Reports for diagrams.
Routines have been added to simulate essentially right-angled radiant chambers, e.g., O and D package
boilers. Field erected boilers are not included because the chamber envelope is made of eight rather than
six planes. Special studies are possible.
Surface zones may be exposed tubes, refractory covered tubes, or refractory. The output is similar to the
process fired heater evaluation with the exception that exposed projected surface fluxes are printed
instead of tube fluxes.
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Sloped or Hip Roof
Prior to developing an input data set, user must re-dimension it to a right angle roof. Do not place a tube
at the intersection of the side wall and roof tubes. Allow a full tube spacing.
The radiant view factors for the roof tubes will not be quite right, but the important consideration is to
specify a tube coil geometry that contains the correct radiant heat transfer surface.
Case Configuration Panel
Case type
Specifies the type of fired heater case as combustion, convection, radiant, or API530.
Required: Yes
Units: None
Default: Depends on the type of case created
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Radiant section type
If you specify a radiant fired heater, you must specify the type of radiant section: cylindrical, box, or single
zone.
Required: Yes (for radiant fired heaters)
Units: None
Default: Cylindrical
Convection section
Check to specify a convection section for a radiant fired heater.
Required: No
Units: None
Default: Unchecked
Case
Specifies a character string (up to 72 characters) that is used to describe the case. This string appears on
the header page of all output reports.
Required: No
Units: None
Default: Blank
Note
The Problem field can be used to specify additional information about the case.
Problem
Specifies a character string (up to 72 characters) that is used to describe the case. This string appears on
the header page of all output reports.
Required: No
Units: None
Default: Blank
Note
The Case field can be used to specify additional information about the case.
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Name Panel
Items on this panel appear in headers of all output reports. All fields are optional.
Case description
Specifies additional descriptive information for current input case. Use up to 72 alphanumeric characters
in this field.
Required: No
Units: None
Default: None
Note
This label appears in header lines of all output report pages.
Problem description
Specifies descriptive title for current input case. Use up to 72 alphanumeric characters in this field.
Required: No
Units: None
Default: None
Overview Fired Heaters (Xfh) Online Help
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Note
This label appears in header lines of all output report pages.
Job number
Specifies job number to appear on the specification sheet.
Required: No
Units: None
Default: None
Note
Although you can enter any length character string, only the first 39 characters appear on the
specification sheet.
Item number
Specifies item number to appear on the specification sheet.
Required: No
Units: None
Default: None
Note
Although you can enter any length character string, only the first 39 characters appear on the
specification sheet.
Reference number
Specifies a reference number to appear on the specification sheet.
Required: No
Units: None
Default: None
Note
Although you can enter any length character string, only the first 39 characters appear on the
specification sheet.
Proposal number
Specifies proposal number to appear on the specification sheet.
Required: No
Units: None
Default: None
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Note
Although you can enter any length character string, only the first 39 characters appear on the
specification sheet.
Revision
Specifies revision to appear on the specification sheet.
Required: No
Units: None
Default: None
Note
Although you can enter any length character string, only the first 15 characters appear on the
specification sheet.
Service
Specifies Service of Unit that appears on the specification sheet.
Required: No
Units: None
Default: None
Note
Although you can enter any length character string, only the first 44 characters appear on the
specification sheet.
Customer
Specifies customer name to appear on the specification sheet.
Required: No
Units: None
Default: None
Note
Although you can enter any length character string, only the first 44 characters appear on the
specification sheet.
Plant location
Specifies location of plant to appear on the specification sheet.
Required: No
Units: None
Default: None
Overview Fired Heaters (Xfh) Online Help
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Note
Although you can enter any length character string, only the first 44 characters appear on the
specification sheet.
Remarks
Specifies remarks to appear on the specification sheet.
Required: No
Units: None
Default: None
Note
Although you can enter any length character string, only the first 90 characters appear on the
specification sheet. The program respects the hard returns you enter, which means that you can
separate text into more than one line. The TEMA Specification Sheet allows 3 lines of text.
Ambient Air Conditions Panel
This panel is used to provide temperature, pressure, and moisture content of the ambient air. Ambient air
conditions are used to calculate draft in the firebox and to determine oxidant air properties.
Ambient air pressure
Specifies the pressure of the ambient air.
Required: Yes
Units: kPa (SI), psia (US), Kgf/cm²A (MKH)
Default: 101.32 kPa (14.7 psia)
Note
This field is used to calculate the air density, which is used to calculate the draft inside the firebox.
Fired Heaters (Xfh) Online Help Overview
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Ambient air temperature
Specifies the temperature of the ambient air.
Required: Yes
Units: °C (SI), °F (US), °C (MKH)
Default: 26.67 °C (80 °F)
Note
This field is used to calculate the air density, which is used to calculate the draft inside the firebox.
Ambient air moisture
Specifies the amount of water in the ambient air. You may specify the water content in one of four ways.
Relative humidity % (SI), % (US), % (MKH)
Weight/weight kg/kg (SI), lb/lb (US), kg/kg (MKH)
Volume/weight m³/kg (SI), ft³/lb (US), m³/kg (MKH)
Volume/volume m³/m³ (SI), ft³/ft³ (US), m³/m³ (MKH)
Required: Yes
Units: Depends upon selection (see above)
Default: None
Note
The volumes in the moisture specification are calculated at standard conditions (e.g. 1 atmosphere
and 15.6 °C (60 °F).
Clear Selected Property
Clears the property values selected on the property grid.
Clear All Properties
Clears all properties specified on the property grid.
Clear All Heat Release Data
When you click this button, all heat release data are cleared from the Heat Release Curve panel.
Clear All Temperature Data
When you click this button, you clear all reference temperatures and pressures on the T&P panel. Heat
release and property grid data are not cleared but remain hidden until you specify new reference
temperatures and pressures.
Overview Fired Heaters (Xfh) Online Help
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Insulation specification
Select how you want to define the insulation in the heater.
Specified heat loss coefficients
Define the heat loss through the walls as a function of temperature by entering heat loss coefficients
Specified insulation material/thickness
Define the composition and thickness of the refractory on each wall; specify user-defined materials
Adiabatic/no heat loss
Specify if you want to model the heater without any heat loss through the refractory walls
Required: Yes
Units: n/a
Default: Specified heat loss coefficients
Heat release entry type
Specifies the type of entry for the heat release curve.
Specific enthalpy
Specific enthalpy of the fluid at each temperature point
Total duty from inlet
Change in total enthalpy of the fluid from the inlet to the current temperature
Required: Yes (for two-phase fluids)
Units: None
Default: Specific enthalpy
Flow basis for heat release curve
Specifies the fluid flow rate on which the heat release duty is based.
Required: Yes
Units: kg/sec (SI), 1000 lb/hr (US), 1000 kg/hr (MKH)
Default: None
Note
This field is visible only if you specify Total Duty from Inlet as the Heat Release Entry Type.
Fired Heaters (Xfh) Online Help API530 Module
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API530 Module
The API530 module can be used to perform several calculations relative to the tubes in the firebox. These
calculations include
Inside heat transfer coefficient
Tube metal temperature
Required tube metal thickness
Tube life evaluation
The program guides the user through a series of panels based on which items are selected for
calculation.
The API530 tube module includes the following panels:
API530 Summary Panel
Heat Flux Parameters Panel
Inside Heat Transfer Coefficient Panel
Metal Temperature Parameters Panel
Operating Conditions Panel
Physical Properties for User-Specified Metallurgy Panel
Tube Life Evaluation Panel
API 530 Calculations
Tube thickness design calculations are performed according to the API 530 standard.
Heat transfer coefficient
Metal temperature
Maximum flux
Required tube thickness
Tube retirement tables
– Past history considered
– Predicted life based on operating conditions
– Maximum temperature based on required life
API530 Module Fired Heaters (Xfh) Online Help
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Rupture and Elastic Designs Considered
Metal Databank
Built-in properties for all API530 tube materials
Allows for user-defined materials
Fired Heaters (Xfh) Online Help API530 Module
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API530 Summary Panel
This panel is used to define the process tube geometry and material for all API530 calculations. Values
on this panel are required for all API530 calculation options.
Tube Design option
Check this option to enable the input for API530 tube design calculations.
Required: No
Units: None
Default: Unchecked
Tube life evaluation
Xfh calculates past and/or future tube damage according to the methods presented in Appendix E of
API530.
Required: No
Units: None
Default: Not selected
API530 Module Fired Heaters (Xfh) Online Help
Page 16 © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.
Note
This option requires no additional information other than the required tube geometry and metallurgy.
Tube type (for tube design)
Select how the program handles the specified pipe dimensions. The choices are
Tubing
Piping
Required: Yes
Units: None
Default: Tubing
Note
This field only has an effect on the calculated minimum thickness requirement. If piping is specified,
the program will assume a 12.5% mill tolerance (i.e., a divided minimum thickness by 0.875) and then
round up to the next standard pipe schedule.
Tube outside diameter
Specify the outside diameter of the tube used in the API530 calculations.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: N5
Note
Specify the actual outside diameter of the tube or select the nominal outside diameter of the tube from
the drop-down list.
Tube inside diameter
Specify the inside diameter of the tube used in the API530 calculations. If the program is calculating the
required wall thickness, then this value is an initial estimate.
Required: Yes (alternatively, wall thickness can be specified)
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
Specify the actual inside diameter of the tube or select the nominal inside diameter of the tube from
the drop-down list. The program will calculate tube thickness from outside and inside diameter values.
Fired Heaters (Xfh) Online Help API530 Module
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Tube wall thickness
Specify the average wall thickness of the tube used in the API530 calculations. If the program is
calculating the required wall thickness, then this value is an initial estimate.
Required: Yes (alternatively, tube inside diameter can be specified)
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
Specify the actual wall thickness or select a pipe schedule from the drop-down list. The program will
calculate tube inside diameter from outside diameter and wall thickness values.
Tube metallurgy
Specify the tube material of the tube used in the API530 calculations. You may select from a built-in
databank or define your own material.
LOW-CS
MED-CS
C.5MO
1.25CR
2.25CR
3CR
5CR
5CR-SI
7CR
9CR
9CR-VA
T304&H
T316&H
T316L
T321
T321H
T347H
800H
HK40
T410
OTHER
Required: Yes
Units: None
Default: 9CR
Note
If OTHER is selected, the program will display the Physical Properties for User-Defined Metallurgy
panel. This panel allows specification of properties for materials not in the databank.
API530 Module Fired Heaters (Xfh) Online Help
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Tube Metal Databank
Internally, the program contains a databank of tube materials. If the desired material is selected from the
databank, the program can automatically calculate required material properties such as yield stress and
modulus of elasticity.
Synonym Material
LOW-CS Low-carbon steel, ASTM A 161, A192
MED-CS Medium-carbon steel, ASTM A53 Grade B (Seamless), A106 Grade B, A210 Grade A-1
C.5MO C-0.5 Mo Steel, ASTM A 161 T1, A209 T1, A 335 P1
1.25CR 1.25 Cr – 0.5 Mo Steel, ASTM A 213 T11, A 335 P11, A 200 T11
2.25CR 2.25 Cr – 1 Mo Steel, ASTM A 213 T22, A 335 P22, A 200 T22
3CR 3 Cr – 1 Mo Steel, ASTM A 213 T21, A 335 P21, A 200 T21
5CR 5 Cr – 0.5 Mo Steel, ASTM A 213 T5, A 335 P5, A 200 T5
5CR-SI 5 Cr – 0.5 Mo Si Steel, ASTM A 213 T5b, A 335 P5b
7CR 7 Cr – 0.5 Mo Steel, ASTM A 213 T7, A 335 P7, A 200 T7
9CR 9 Cr – 1 Mo Steel, ASTM A 213 T9, A 335 P9, A 200 T9
9CR-VA 9 Cr – 1 Mo-Va Steel, ASTM A 213 T91, A 335 P91, A 200 T91
T304&H 304 and 304H Stainless, ASTM A 213, A 271, A 312, A 376
T316&H 316 and 316H Stainless, ASTM A 213, A 271, A 312, A 376
T316L 316L Stainless
T321 321 Stainless, ASTM A 213, A 271, A 312, A 376
T321H 321H Stainless, ASTM A 213, A 271, A 312, A 376
T347H 347 and 347H Stainless, ASTM A 213, A 271, A 312, A 376
800H Alloy 800H, ASTM B 407 UNS N08810
HK40 HK-40, ASTM A 608 Grade HK-40
T410 T410, ASTM A 268 Type TP410
OTHER User-defined material
Rupture stress curve
Specify which rupture stress curve to use in performing API530 required wall thickness calculations.
There are two options.
1 Use the minimum rupture curve. Select the MIN radio button for this option. No value is needed in the
"Rupture stress curve to be used" field.
2 Use a fraction of the average rupture curve. Select the Fraction radio button for this option. Enter the
desired fraction of the average rupture curve (1.0 to use the average) in the field labeled "Rupture
stress curve to be used."
Required: Yes
Units: None
Default: MIN (Use minimum rupture curve)
Note
You can use a value larger than the average rupture curve by specifying a fraction greater than 1.0.
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Print metal properties for inspection
Specify whether the program should print a table of tube metal properties in the output. The program
provides two options for the property tables.
The short option allows the user to specify three values of temperature and three values of the
Larson-Miller parameter. Properties are printed at the specified values.
The detailed option allows the user to specify a beginning and ending temperature and Larson-Miller
parameter. A step size is also specified for both.
The program prints metal properties at all points between the beginning and ending values using the
specified step size.
Required: Yes
Units: None
Default: No
Note
The program prints yield stress, modulus of elasticity, thermal expansion, and thermal conductivity at
the specified temperatures. The minimum rupture strength is printed at the specified Larson-Miller
parameters.
API530 Module Fired Heaters (Xfh) Online Help
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Physical Properties for User-Specified Metallurgy Panel
This panel is used to provide metal properties for materials that are not in the internal databank. This
panel appears only if you specify OTHER for the tube metallurgy on the Tube Dimension and Metallurgy
panel.
Metal identification
Provide a descriptive tag for a user-defined tube material. This value can be any alphanumeric string up
to 8 characters long.
Required: No
Units: None
Default: None
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Type of material
Define the type of material for a user-defined tube material. The choices are
FERR – Ferritic
AUST – Austenitic
Required: Yes
Units: None
Default: FERR – Ferritic
Note
The value chosen will determine the minimum acceptable tube thickness for new tubes. The values
used are given in Table 1 in Section 2.6 of API530. This value is also used in calculation of thermal
stresses. See Section D.2 of API530.
Poisson's ratio
Specify the value of Poisson’s ratio for the material being defined. Poisson’s ratio is the ratio of lateral
strain to axial strain. The values for most metals fall between 0.25 and 0.35.
Required: Yes (for a user-defined material)
Units: None
Default: 0.3
Note
The value of Poisson’s ratio should be specified at the mean temperature of the tube wall. The value
is used to calculate thermal stresses according to Section D.2 of API530.
Specific gravity
Specify the value of specific gravity for the material being defined.
Required: Yes (for a user-defined material)
Units: None
Default: 7.86
Note
This value is used to calculate the tube weight and should be specified at the mean temperature of the
tube wall.
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Limiting design metal temperature
Specify the limiting design metal temperature for a user-defined material. The limiting design metal
temperature is the upper limit of the reliability of the rupture strength data.
Required: Yes (for a user-defined material)
Units: °C (SI), °F (US), °C (MKH)
Default: 537.78 °C (1000 °F)
Note
The program will issue a warning message if the tube metal temperatures exceed the specified value.
See Table 4 in Section 3 of API530 for values for common tube materials.
Lower critical temperature
Specify the lower critical temperature for a user-defined material. The lower critical temperature for a steel
alloy is the temperature below which, under equilibrium conditions, all austenite has transformed to ferrite
and cementite phases.
Required: Yes (for a user-defined material)
Units: °C (SI), °F (US), °C (MKH)
Default: 718.33 °C (1325 °F)
Note
This value is currently not used by the program. This temperature is important since operation at
higher temperatures may result in changes in the alloy’s microstructure.
Material constant A per Table 2
Specify a material constant characteristic of the user-defined tube material. See Equation B-11 of API530
Appendix B for the definition of this constant.
Required: Yes (for a user-defined material)
Units: MPa MMpsi kg/mm²
Default: 2.88E+05 MPa (41.7 MMpsi)
Note
Table 3 in Section 2 of API530 lists values for common tube materials.
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L-M constant C per Appendix A.3
Define the empirical constant C in the definition of the Larson-Miller parameter for a user-defined
material. See Section A.3 in Appendix A of API530 for a definition of this constant.
Required: Yes (for a user-defined material)
Units: hr (SI), hr(US), hr (MKH)
Default: 20
Note
The generally accepted empirical values for this constant are 20 for ferritic steels and 15 for austenitic
steels. A value of 30 is used for T91 or P91, 9Cr-1Mo-Va steel.
Yield stress
Specify a yield stress correlation for a user-defined tube material. The form of the equation is
)(5)(4)(3)(2)(10)( 5432 TYTYTYTYTYYYLn
where Ln is the natural logarithm, Y is the yield stress, and T is the temperature. The user must specify
values for Y0 – Y5.
Required: Yes (for a user-defined material)
Units: MPa (SI), 1000 psi (US), kg/mm² (MKH)
Default: Values for medium carbon steel
Note
By default, the correlation is in terms of temperature in °F. If your correlation is in other temperature
units, this can be changed by clicking on the label "As a function of temperature in ___."
Modulus of elasticity
Specify a modulus of elasticity correlation for a user-defined tube material. The form of the equation is
)(4)(3)(2)(10 432 TETETETEEE
where E is the modulus of elasticity and T is the temperature. The user must specify values for E0 – E4.
Required: Yes (for a user-defined material)
Units: MPa (SI), MMpsi (US), kg/mm² (MKH)
Default: Values for medium carbon steel
Note
By default, the correlation is in terms of temperature in °F. If your correlation is in other temperature
units, this can be changed by clicking on the label "As a function of temperature in ___."
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Thermal expansion
Specify a thermal expansion correlation for a user-defined tube material. The form of the equation is
)(2)(10 2TATAAA
where A is the thermal expansion and T is the temperature. The user must specify values for A0 – A2.
Required: Yes (for a user-defined material)
Units: mm/mm °C (SI), micro in./in. °F (US), mm/mm °C (MKH)
Default: Values for medium carbon steel
Note
By default, the correlation is in terms of temperature in °F. If your correlation is in other temperature
units, this can be changed by clicking on the label "As a function of temperature in ___."
Thermal conductivity
Specify a thermal conductivity correlation for a user-defined tube material. The form of the equation is
)(2)(10 2TKTKKK
where K is the thermal conductivity and T is the temperature. The user must specify values for K0 – K2.
Required: Yes (for a user-defined material)
Units: W/m °C (SI), Btu/hr ft °F (US), Kcal/hr m °C (MKH)
Default: Values for medium carbon steel
Note
By default, the correlation is in terms of temperature in °F. If your correlation is in other temperature
units, this can be changed by clicking on the label "As a function of temperature in ___."
Rupture stress
Specify a rupture stress correlation for a user-defined tube material. The form of the equation is
)(5)(4)(3)(2)(10)( 5432 LMSLMSLMSLMSLMSSSLn
where Ln is the natural logarithm, S is the rupture stress, and LM is the Larson-Miller parameter.
Required: Yes (for a user-defined material)
Units: MPa (SI), 1000 psi (US), kg/mm² (MKH)
Default: Values for medium carbon steel
Note
The Larson-Miller parameter must be defined in terms of °F and hours regardless of the units
specified for rupture stress.
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Inside Heat Transfer Coefficient Panel
This panel is used to specify the process information required to calculate the process heat transfer
coefficient. This panel appears only if you specify the Calc option for the inside heat transfer coefficient on
the Metal Radial Temperature Profile panel. If you have selected the Required Tube Metal Thickness
calculation option, the program will display this panel for both Start of Run and End of Run.
Tube length between return bends
Specify the straight length of pipe between U-bends in the tube coil.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
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Total mass flow rate for all passes
Specify the total process flow rate (for all passes) in the radiant section of the heater.
Required: Yes
Units: kg/hr (SI), lb/hr (US), kg/hr (MKH)
Default: None
Note
The program divides this flow rate by the number of passes to determine the flow rate through a single
tube in the radiant tube coil.
Number of tubepasses
Specify the number of tubepasses in the radiant tube coil. For a fired heater, the number of passes is
defined as the number of separate flow paths through the coil. The flow rate through each pass is the
total flow/number of passes.
Required: Yes
Units: None
Default: 1
Note
This definition differs from that used by shell-and-tube exchangers.
Fluid pressure
Specify the pressure of the fluid inside the process tube being designed.
Required: Yes
Units: kPaG (SI), psig (US), kg/cm²G (MKH)
Default: 0
Weight fraction vapor
Specify the weight fraction vapor of the fluid inside the process tube being designed.
Required: Yes
Units: None
Default: 1.0
Note
This value must be between 0.0 and 1.0.
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TEMA fouling factor
Specify the fouling factor (resistance) on the inside of the process tube being designed.
Required: No
Units: m² K/W (SI), ft² hr °F/Btu (US), m² hr °C/kcal (MKH)
Default: 0.0
Specific heat
Specify the liquid heat capacity of the process fluid in the tube being designed. The value should be
specified at the temperature and pressure specified for the bulk fluid on the Inside Heat Transfer
Coefficient panel.
Required: Yes (if liquid phase is present)
Units: kJ/kg °C (SI), Btu/lb °F (US), kcal/kg °C (MKH)
Default: None
Note
This field will be disabled if the weight fraction liquid is specified as zero (0) on the Inside Heat
Transfer Coefficient panel.
Thermal conductivity
Specify the liquid thermal conductivity of the process fluid in the tube being designed. The value should
be specified at the temperature and pressure specified for the bulk fluid on the Inside Heat Transfer
Coefficient panel.
Required: Yes (if liquid phase is present)
Units: W/m °C (SI), Btu/hr ft °F (US), kcal/hr m °C (MKH)
Default: None
Note
This field will be disabled if the weight fraction liquid is specified as zero (0) on the Inside Heat
Transfer Coefficient panel.
Density
Specify the liquid density of the process fluid in the tube being designed. The value should be specified at
the temperature and pressure specified for the bulk fluid on the Inside Heat Transfer Coefficient panel.
Required: Yes (if liquid phase is present)
Units: kg/m³ (SI), lb/ft³ (US), kg/m³ (MKH)
Default: None
Note
This field will be disabled if the weight fraction liquid is specified as zero (0) on the Inside Heat
Transfer Coefficient panel.
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Viscosity
Specify liquid viscosity of the process fluid in the tube being designed at one or more temperatures. For
each viscosity specified, you must enter the corresponding temperature.
Required: Yes (if liquid phase is present)
Units: mN s/m² (SI), centiPoise (US), centipoises (MKH)
Default: None
Note
If a single viscosity is given, the liquid viscosity is assumed to be constant at the value specified. If two
points are provided, then the log of the viscosity is fit to a straight line through the specified points. If
three or more points are specified, a least squares regression is performed to fit the data to the
Antoine equation.
This field will be disabled if the weight fraction liquid is specified as zero (0) on the Inside Heat
Transfer Coefficient panel.
Temperature
Specify a range of temperatures for the bulk liquid stream. This range of temperatures is used to
determine the liquid viscosity.
Required: No
Units: °C (SI), °F (US), °C (MKH)
Default: None
Specific heat
Specify the vapor heat capacity of the process fluid in the tube being designed. The value should be
specified at the temperature and pressure specified for the bulk fluid on the Inside Heat Transfer
Coefficient panel.
Required: Yes (if vapor phase is present)
Units: kJ/kg °C (SI), Btu/lb °F (US), kcal/kg °C (MKH)
Default: None
Note
This field will be disabled if the weight fraction vapor is specified as zero (0) on the Inside Heat
Transfer Coefficient panel.
Thermal conductivity
Specify the vapor thermal conductivity of the process fluid in the tube being designed. The value should
be specified at the temperature and pressure specified for the bulk fluid on the Inside Heat Transfer
Coefficient panel.
Required: Yes (if vapor phase is present)
Units: W/m °C (SI), Btu/hr ft °F (US), kcal/hr m °C (MKH)
Default: None
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Note
This field will be disabled if the weight fraction vapor is specified as zero (0) on the Inside Heat
Transfer Coefficient panel.
Density
Specify the vapor density of the process fluid in the tube being designed. The value should be specified at
the temperature and pressure specified for the bulk fluid on the Inside Heat Transfer Coefficient panel.
Required: Yes (if vapor phase is present)
Units: kg/m³ (SI), lb/ft³ (US), kg/m³ (MKH)
Default: None
Note
This field will be disabled if the weight fraction vapor is specified as zero (0) on the Inside Heat
Transfer Coefficient panel.
Viscosity
Specify the vapor viscosity of the process fluid in the tube being designed at one or more temperatures.
Required: Yes (if vapor phase is present)
Units: mN s/m² (SI), centiPoise (US), centipoises (MKH)
Default: None
Note
This field will be disabled if the weight fraction vapor is specified as zero (0) on the Inside Heat
Transfer Coefficient panel.
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Metal Temperature Parameters Panel
This panel contains options relative to calculating the temperature profile through the tube metal. If you
perform the required tube metal thickness calculation, there are two copies of this panel, one for start of
run conditions and one for end of run.
Fluid bulk temperature
Specify the maximum process bulk temperature inside the tube.
Required: Yes
Units: °C (SI), °F (US), °C (MKH)
Default: None
Note
This field appears on both the Start of Run and End of Run versions of this panel.
Inside heat transfer coefficient
Specify (or request calculation of) the process heat transfer coefficient inside the tube.
Required: Yes (If not specified then Calc option must be selected)
Units: W/m² °C (SI), Btu/hr ft² °F (US), kcal/hr m² °C (MKH)
Default: None
Note
If you choose the option to calculate the heat transfer coefficient (Calc radio button), the program will
subsequently display panels requesting the physical property and process information required to
calculate the heat transfer coefficient. The methods used to calculate the heat transfer coefficient are
given in Section C.2 of API530. This field appears on both the Start of Run and End of Run versions of
this panel.
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Coke thickness
Specify the coke thickness on the inside of the process tube.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: 0.0
Note
If you specify a coke thickness, you must also specify the coke thermal conductivity to allow
calculation of the resistance across the coke layer. This field appears on both the Start of Run and
End of Run versions of this panel.
Coke thermal conductivity
Define the thermal conductivity of the coke layer inside the tube.
Temperature
Required: Yes (if coke thickness is > 0.0)
Units: °C (SI), °F (US), °C (MKH)
Default: None
Thermal Conductivity
Required: No
Units: W/m °C (SI), Btu in./hr ft °F (US), kcal/hr m °C (MKH)
Default: None
Note
You must specify at least one temperature and one thermal conductivity. With one temperature, the
program will assume a constant thermal conductivity. With two values, the program will assume a
linear variation between the specified temperatures. This field appears on both the Start of Run and
End of Run versions of this panel.
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Heat Flux Parameters Panel
This panel is used to specify parameters that are used to calculate the maximum local heat flux on the
process tube being designed. The maximum heat flux is used to calculate the maximum outside tube wall
temperature. The methods used to calculate the maximum local heat flux are given in Section C.3 of
API530.
If you have selected the Required Tube Metal Thickness calculation option, then this panel will appear
twice, for Start of Run and End of Run conditions.
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Tube Flux Type
Presents a series of drawings that lets you specify the configuration of the tube being designed. Select
the drawing that best represents the process tube being designed.
Required: Yes
Units: None
Default: Single row adjacent to a nearly adiabatic wall
Note
The choice on this field is used to calculate the circumferential heat flux variation. The value specified
will determine which curve is used on Figure C-1 in API530.
Center-to-center spacing
Specify the distance between tubes in the tube coil (center-to-center).
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: 203.2 mm (8 in.)
Note
The distance between tubes may vary in different parts of the heater. Specify the value for the
particular tube in the coil being designed.
Average heat flux around tube
Specify the average flux around the circumference of the tube.
Required: Yes
Units: W/m² (SI), Btu/hr ft² (US), kcal/hr m² (MKH)
Default: None
Note
Based on the methods in Section C.3 of API530, the program will calculate the maximum local flux
based on the average flux.
This field will not be displayed if you have specified the maximum local flux on a previous panel.
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Fraction transferred by convection
Specify the fraction of the total flux transferred by convection.
Required: Yes
Units: None
Default: None
Note
This value must be between 0 and 1. Typically, the fraction transferred by convection is less than that
transferred by radiation.
This field will not be displayed if you have specified the maximum heat flux on a previous panel.
Planar peak-to-average factor
Specify a correction factor to indicate the uniformity (of lack) of the heat flux distribution along the length
of the process tube being designed. A value of 1.0 would indicate that the local heat flux does not vary
along the length of the tube.
Required: Yes
Units: None
Default: None
Note
A typical value for this field is 1.25. This value is not the same as FL in Equation C-6 of API530.
This field will not be displayed if you have specified the maximum heat flux on a previous panel.
More information on Planar Peak-to-Average Factor
In calculating the maximum local flux along the length of a tube, the API530 procedure uses a parameter
(FL) in Equation C-6 of API530. This parameter defines the variation of the radiant flux along the length of
the tube.
The program uses a slightly different approach. Its correction factor (FLRC) defines the variation of the
total flux (radiant + convective) along the length of the tube. This parameter is obviously a function of box
geometry, burner spacing, flame length, etc. Assuming that the burner spacing and flame shape are
"reasonable," we can define typical values of this parameter based on box geometry. Defining a
parameter H/W as the height-to-width ratio for box heaters or the height-to-diameter ratio for cylindrical
heaters, the recommended values for this parameter appear below.
H/W FLRC
<= 2.5 1.25
3.0 1.875
>=3.5 2.5
For values between 2.5 and 3.0 and between 3.0 and 3.5, you can linearly interpolate the values in the
table.
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Operating Conditions Panel
This panel is used to specify options in the API530 minimum tube wall thickness calculations. This panel
is displayed only if you select Required Tube Metal Thickness on the API530 Calculation Options panel.
Tube identification
Supply a descriptive tag to the tube being designed. This value can be any alphanumeric string up to 8
characters long.
Required: No
Units: None
Default: None
Maximum design pressure (elastic)
Specify the maximum pressure that the heater coil will sustain for short periods of time. This pressure is
usually related to relief valve settings, pump shut-in pressure, etc.
Required: No
Units: kPaG (SI), psig (US), kmf/cm²G (MKH)
Default: See note below
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Note
You may either specify this value or let the program select a value using the Specify or Calc buttons
to the right of this field. If you select Calc, the program will set the value to 10% or 172.4 kPa (25 psi),
whichever is greater, above the maximum specified operating pressure (at start or end of run). This
value is the elastic design pressure defined in Section 1.4.3 of API 530.
Maximum operating pressure at Start of Run
Specify the maximum process pressure in the tube coil at the beginning of the time period being used for
design.
Required: Yes
Units: kPaG (SI), psig (US), kmf/cm²G (MKH)
Default: None
Note
This value is used for the rupture design calculations and is the same as the rupture design pressure
defined in Section 1.4.4 of API 530. Start of Run panels appear if you select CALC.
Maximum operating pressure at End of Run
Specify the maximum process pressure in the tube coil at the end of the time period being used for
design.
Required: Yes
Units: kPaG (SI), psig (US), kmf/cm²G (MKH)
Default: None
Note
You may specify this value directly (Specify radio button) or tell the program to use the same
pressure as Start of Run (SOR radio button). This value is used for the rupture design calculations
and is the same as the rupture design pressure defined in Section 1.4.4 of API 530.
Metal temperature at Start of Run
Specify the maximum metal temperature on the outside of the tube coil at the beginning of the time period
being used for design.
Required: Yes (or choose CALC option)
Units: °C (SI), °F (US), °C (MKH)
Default: None
Note
If CALC option is chosen, you must specify either the process heat transfer coefficient or enter
sufficient process properties to calculate the process heat transfer coefficient. Start of Run panels
appear if you select CALC.
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Metal temperature at End of Run
Specify the maximum metal temperature on the outside of the tube coil at the end of the time period being
used for design.
Required: Yes (or choose CALC or SOR option)
Units: °C (SI), °F (US), °C (MKH)
Default: None
Note
If CALC option is chosen, you must specify either the process heat transfer coefficient or enter
sufficient process properties to calculate the process heat transfer coefficient. If SOR option is chosen,
this value will be set to the metal temperature specified at the start of run.
Maximum local peak flux
Specify the maximum local heat flux through the process tube coil. This value is then used to calculate
the maximum tube wall temperature.
Required: No
Units: W/m² (SI), Btu/hr ft² (US), kcal/hr m² (MKH)
Default: None
Note
If a value is specified here, it is used for both start of run and end of run conditions. This value will be
overridden if maximum fluxes are specified on the Metal Radial Temperature Profile panels for Start of
Run and End of Run.
Design life for stress
Specify the operating time used as a basis for tube design. The design life is not necessarily the same as
the retirement or replacement life.
Required: No
Units: hr (SI), hr (US), hr (MKH)
Default: 100000 hr
Note
The curves used from the API530 standard may give inaccurate rupture allowable stresses for times
less than 20000 hours or greater than 200000 hours.
Corrosion allowance
Specify the part of the tube thickness that is included for corrosion.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: 3.175 mm (0.125 in.)
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Note
The corrosion allowance does not simply get added to the minimum design thickness. The API530
procedure recognizes that stress changes as the tube thickness changes. The procedure for
calculating the fraction of the corrosion allowance used during design is given in Appendix B of
API530.
Run length between SOR and EOR
Set the duration of the period between Start of Run (SOR) and End of Run (EOR). The procedure in
API530 takes account of the fact that the operating pressure and temperature may vary during the
operating period.
Required: Yes
Units: years (SI), years (US), years (MKH)
Default: 2 years
Note
To account for the effect of varying temperature and pressure, the API530 procedure uses the
concept of an equivalent tube metal temperature. This is defined in Section 2.8 of API530 and derived
in Appendix Section B.5.
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Tube Life Evaluation Panel
The fields on this panel are used to set options for the tube life evaluation procedure from API530. The
tube life evaluation procedure can perform three different estimates.
1 Fraction of tube life used based on past operating history
2 Predicted tube life remaining based on expected operating conditions
3 Maximum operable temperature to achieve a desired remaining tube life
The procedure used by the program is contained in Appendix E of API530.
Tube life evaluation
Select whether to calculate past damage, future damage or both. Depending upon which choice you
make, different fields will appear on the Tube Life Evaluation panel.
Required: Yes
Units: None
Default: Past and future damage
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Initial tube life
Set the fraction of tube life used before the periods specified in the past history table.
Required: Yes
Units: None
Default: 0
Note
This value must be between 0.0 and 1.0.
On-stream time
Specify the length of time over which the specified operating conditions occurred. You may specify up to
5 different periods for the past damage evaluation.
Required: Yes (for any period to be evaluated)
Units: years (SI), years (US), years (MKH)
Default: 5 (for period 1 only)
Note
The operating conditions are assumed to change linearly over the time period specified.
Operating pressure (Start of Run)
Specify the operating tube process pressure at the start of the time period.
Required: Yes (for any period to be evaluated)
Units: kPaG (SI), psig (US), kmf/cm²G (MKH)
Default: 3447.38 kPaG (500 psig) (for period 1 only)
Note
The operating conditions are assumed to change linearly over the time period specified.
Operating pressure (End of Run)
Specify the operating tube process pressure at the end of the time period.
Required: Yes (for any period to be evaluated)
Units: kPaG (SI), psig (US), kmf/cm²G (MKH)
Default: 3447.38 kPaG (500 psig) (for period 1 only)
Note
The operating conditions are assumed to change linearly over the time period specified.
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Metal temperature (Start of Run)
Specify the maximum outside metal temperature of the tube at the beginning of the time period.
Required: Yes (for any period to be evaluated)
Units: °C (SI), °F (US), °C (MKH)
Default: 426.67 °C (800 °F) (for period 1 only)
Note
The operating conditions are assumed to change linearly over the time period specified.
Metal temperature (End of Run)
Specify the maximum outside metal temperature of the tube at the end of the time period.
Required: Yes (for any period to be evaluated)
Units: °C (SI), °F (US), °C (MKH)
Default: 537.78 °C (1000 °F) (for period 1 only)
Note
The operating conditions are assumed to change linearly over the time period specified.
Corrosion rate
Specify the rate of sound metal thickness loss due to corrosion during the time period.
Required: Yes (for any period to be evaluated)
Units: mm/year (SI), in./year (US), mm/year (MKH)
Default: 0.25 mm/year (0.01 in./year) (for period 1 only)
Required tube life
Specify the desired future tube life. Based on the specified value, the program will predict the maximum
temperature at which the tube can be continuously operated and achieve the desired life.
Required: Yes
Units: years (SI), years (US), years (MKH)
Default: 11.4 years (approximately 100000 hours)
Note
The program will also report the maximum final operating wall temperature, assuming the specified
tube life and the user-specified starting wall temperature. This maximum wall temperature assumes
that the wall temperature increases linearly over the specified tube life.
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On-stream time per period
Specify the reporting period desired for damage evaluation. The program will report the remaining life
fraction, sound metal thickness, etc. after each specified time interval up to the expected tube life.
Required: Yes
Units: years (SI), years (US), years (MKH)
Default: 1 year
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Box Heater Module
The box heater module models the radiant- and process-side performance of a box (cabin) heater. The
heater may have 1 to 3 gas spaces, and tube coils may exist on any of the six faces of a gas space. On
the radiant side, Xfh
tube flux calculations at increments along the length of the tube coil
gas temperature calculations in a three-dimensional 4 x 4 x 3 grid within the each gas space
process heat transfer and pressure drop calculations along the full path length of the process fluid for
each tubepass
You provide the geometry of the heater enclosure and the tube coil, the process conditions and physical
properties of the process fluid, and the process conditions and composition of the combustion fuels.
The process-side calculations can accommodate both single-phase and boiling fluids.
The box heater module contains the following panels:
Box Heater Summary Panel
Box Geometry Panel
Gas Space Configuration Panel
Burner Locations Panel
Burner Code Panel
Tube Locations Panel
Tube Section Geometry Panel
Tubepass Sequence Panel
Tube Flow Direction Panel
Process Methods Panel
Insulation Specification Panel
Heat Loss Coefficients Panel
Optional Panel
Stack Panel
Bundle Panel
Bundle Layout Panel
Tube Types Panel
Tube Sink Definition Panel
Radiant Box Panel
Tube Zones Panel
Radiant Box Process Conditions Panel
The box module calculates the performance of a box (cabin) heater.
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Geometry
Single/double cell heaters
1 – 3 gas spaces
Arbor or U-tubes
Horizontal or vertical tubes
Floor- or end-wall-fired
Process Calculations
Tubeside heat transfer and pressure drop using HTRI proprietary methods
Optional API530 method for heat transfer
Radiant Calculations
Three-dimensional incrementation using Hottel Zoning method
Local radiant and convective fluxes to the tube coil
Local wall temperatures of tube coil
Gas temperature distribution within firebox
Flue gas circulation using Jet Similarity
Single-zone calculation option
Duty Specification
Specified fuel flow rate
User-specified firebox duty
User-specified convection + firebox duty
Heat Loss Calculations
Specified heat loss equations
Insulating materials from internal databank
User-defined materials
Limitations
Maximum of six (6) burners in a gas space
Maximum of 200 tubes in the firebox
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Box Heater Summary Panel
In this panel, you specify the heater type, duty, and insulation. Based on your selections, subsequent
panels request appropriate dimensions for your selected heater type.
Box Heater Type Selection
Xfh models several different types of box or cabin heaters. The table below lists some considerations
relative to each type.
Single-cell top opening Most common configuration; the
default type in Xfh.
Single-cell side opening
Single-cell double roof
opening
Xfh models any convection section
present using a mixed flue-gas
stream.
Double-cell or single-cell
with radiant wall
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Arbor, U-tube, or inverted
U-tube
Xfh models this type as three gas
spaces (left, right, and center of U-
tube). Use this selection only if the
heater has burners on both sides of
the vertical U-tube legs.
No tubes This option allows you to model
heaters (e.g., boilers) where the tube
geometry cannot be directly specified
in Xfh.
Height (H)
Specify the inside height (from floor to roof) of the radiant section of a box heater.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Width (W)
Specify the inside width (from refractory to refractory) of the radiant section of a box heater. For end-fired
heaters, the inside width is the dimension of the wall containing the burners.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
For multi-gas space heaters, this dimension includes all gas spaces.
Depth (D)
Specify the inside depth (distance between end walls) of the radiant section of a box heater. For end-fired
heaters, the depth is the dimension between the walls containing the burners.
Required: Yes
Units: m ft mm
Default: None
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Flue Gas Opening Dimension A
Specify the width of the flue gas opening to the convection section or stack.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
Xfh assumes that all openings for double flue gas openings are the same dimension.
Flue Gas Opening Dimension B
Specify the distance from the edge (inside wall) of the box heater to the beginning of the flue gas
opening.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
Xfh assumes that all openings for double flue gas openings are symmetrically located.
Height (T)
Specify the height of the radiant wall (or opening between cells) for a double-cell box heater.
Required: Yes (for a double-cell heater)
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
This field appears only when you select a double-cell box heater type.
Width (U)
Specify the width of the radiant wall (or opening between cells) for a double-cell box heater.
Required: Yes (for a double-cell heater)
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
This field appears only when you select a double-cell box heater type.
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Width (V)
Specify the inside width of each cell in a double-cell box heater.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
This field appears only when you select a double-cell box heater type.
Modeling Box Heaters
Due to the current size of the 3D grid used to model box heaters, Xfh is currently limited to a maximum of
six burners in a gas space. Attempting to use more than six burners prevents Xfh from resolving
individual burners.
Quite commonly, of course, box heaters have many more than six burners. You have several options to
simulate modeling such heaters:
1 Use the Y-multiplier option if your box heater is floor-fired and contains only horizontal tubes on the
side walls.
2 If your geometry does not permit use of Option 1, model your box heater in slices and then manually
combine the results. Because you will be breaking the radiant process fluid flow path into multiple
pieces in this procedure, you must build your input using PCL for this option.
3 Combine multiple burners into a single "virtual" burner. This option is relatively easy but compromises
the accuracy of the solution. In order to get the burner throat velocity correct, create a burner diameter
that is larger than any single burner. This affects the flue gas recirculation calculations and the
location of the burner flame in the 3D grid.
Box Geometry - Single-Cell Top Opening
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Box Geometry - Single-Cell Side Opening
Box Geometry - Single-Cell Double-Roof Opening
Box Geometry - Double- or Single-Cell with Radiant Wall
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Box Geometry - Arbor, U-Tube, or Inverted U-Tube
Box Geometry - No Tubes
Gas Configuration Panel
Specify the number and size of the gas spaces inside a box heater. Depending on which style of box
heater you have selected (indicated by the value in parentheses on the title bar), this panel displays a
different list of choices.
Select one of the box heater types below to view the valid gas space configurations for each:
Single-Cell Top Opening
Single-Cell Side Opening
Single-Cell Double Roof Opening
Double-Cell or Single-Cell with Radiant Wall
Arbor, U-Tube, or Inverted U-Tube
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Gas Space Configuration ID
Specify the arrangement of gas spaces within the box heater. The panel displays the valid choices, and
the drop-down list contains the IDs for all valid choices.
Required: Yes
Units: None
Default: Based on box heater type
More Information
Gas Space Definitions
Configuration with Identical Gas Spaces
w1, w2, w3
Specify the width of the individual gas spaces within the box heater. Depending on which gas space
configuration ID is chosen, Xfh enables one or more of these width fields.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
The sum of all required widths must equal the maximum width indicated.
Gas Space Definitions
Displays a dialog box that provides the definition of a gas space as used by Xfh.
A gas space is considered bounded by a row (or double row) of tubes, a wall, or row(s) of tubes next to a
wall. The entire radiant chamber of a box heater is divided into one or more gas spaces.
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Configurations with Identical Gas Spaces
In the list of box heater configurations, some indicate identical gas spaces. For example, consider the two
configurations below:
ID = 2 shows two identical gas spaces, and ID = 3 shows two gas spaces which may or may not be
identical. Gas spaces considered to be identical meet the following conditions:
1 Identical gas space dimensions
2 Identical burner locations, types, and firing rates
3 Identical tube coils
4 Identical process fluid profiles
The last item prevents the process flow path from flowing between the identical gas spaces. For example,
the tube coil geometry may be identical, but if the process fluid enters in one gas space and then travels
to the next gas space, the tubeside temperature profiles (and therefore tube wall temperatures) will not be
identical. To model such a system, select a configuration (e.g., ID = 3) that does not have identical gas
spaces.
You must also specify input geometry according to the following rules:
1 Specify the dimensions of the entire box. For example, for ID = 2, you would specify the total width of
the heater (the width from refractory face to refractory face).
2 Specify the tube geometry and passes for only the symmetric half of the heater.
3 Specify the total process flow rate to the entire heater.
4 Specify the total fuel flow rate to the entire heater.
The output reports will reflect the duty and flow rates of the entire heater and not just the symmetric half.
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Single-Cell, Top Opening Gas Space
Single-Cell, Side Opening Gas Space
Single-Cell, Double Roof Opening Gas Space
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Double-Cell or Single-Cell with Radiant Wall Gas Space
Arbor, U-tube, or Inverted U-Tube Gas Space
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Burner Locations Panel
This panel indicates the type of firing (floor or end wall) and the number of burners in each gas space. It
also allows you to specify the locations of the burners within the heater. You must specify the location of
all burners.
Burner location/firing direction
Specify the location of the burners within the box heater. The choices include
Floor/Firing upwards
End wall/Firing toward opposite end
Both end walls/Firing toward each other
Required: Yes
Units: None
Default: Both end walls/Firing toward each other
Note
When firing from both end walls, Xfh assumes an equal number of burners, equal firing rates, etc. on
both ends of the heater.
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Number of symmetric sections
Specify the number of symmetric gas space sections along the y-axis. This option is used for floor firing
with horizontal tubes only. Symmetry should be used as much as practical to increase the accuracy of the
program, which divides each gas space into 48 zones (3 x 4 x 4).
The number of symmetric sections does not have to be an integer. The program can simulate more than
six burners in each gas space using this input item.
Number of Burners in Each Gas Space
Sets the number of burners per gas space. The maximum number of burners that Xfh can simulate in a
single gas space is six (6). If the gas space contains more than six burners, the burners must be grouped
together into no more than six simulated burners.
In the Actual number of burners field, enter the number of actual burners in the gas space.
Required: Yes for simulated burners (optional for actual burners)
Units: None
Default: 3 simulated, 3 actual per gas space
Note
When you must group burners to stay within the maximum of six, use the following rules:
1 If you specify the jet opening in the burners, set the value to the total of the grouped burners so Xfh
calculates the correct throat velocity.
2 If you specify flame length indirectly through the flame length correlation, note that Xfh calculates the
flame length from the total duty of the grouped burners.
Local Coordinate X/Y/Z
Sets the local (relative to edge of gas space) coordinates of a burner. If the heater is floor-fired, you must
set the X (width) and Y (depth) coordinates. If end-fired, set the X (width) and Z (height) coordinates.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
You must directly specify the coordinates of the first burner in a gas space. For all other burners, you
can specify the location using a distance from the last burner along the X, Y, or Z axis.
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Space from Last Burner
Specifies the distance along the X, Y, or Z axis from the previous burner in this gas space. You must
specify the actual coordinates of the first burner in each gas space, but for all other burners, this field is
optional.
Required: No (unless actual burner coordinates are not specified)
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
If you specify a value in this field, you must also specify the axis that the value represents.
Along Axis
Designates the coordinate axis for the value you specify in the Space from Last Burner field. If the
heater is floor-fired, the value must relate to either the X (width) or Y (depth) axis. If end-fired, to the X
(width) or Z (height) axis.
Required: Yes (if Space from Last Burner is specified)
Units: None
Default: None
Valid Burner Coordinates...
Display the valid range of values for these coordinates. The figure automatically updates to match the
data input.
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Burner Parameters Panel
You use this panel to specify the necessary parameters for the burners on a burner-by-burner basis. On a
gas-space-by-gas-space basis, you may specify pressure drop and flame length parameters for the
burners. You also use this panel to access the internal burner databanks.
Effective Flame Length
Sets the flame length for an individual burner. The flame length may be specified directly or calculated by
the software.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
To have Xfh calculate the flame length, leave this field blank, and specify the A and B columns.
Minimum Jet Opening
Specifies the flow area of the burner throat. Xfh uses this value to calculate the gas velocity in to the
firebox.
Required: Yes (or specify Entrance Gas Velocity)
Units: m² (SI), ft² (US), m² (MKH)
Default: None
Note
Instead of specifying minimum jet opening, you can specify the entrance gas velocity.
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Entrance Gas Velocity
Specifies the gas velocity exiting the burner throat. Xfh uses this value in the flue gas circulation
calculations.
Required: Yes (or specify Minimum Jet Opening)
Units: m/s (SI), ft/sec (US), m/s (MKH)
Default: None
Planar Half Jet Angle
Specifies the angle (from centerline of the burner throat) of the flue gas cone leaving the burner. An angle
of 0 implies that flue gas flows straight up from the burner throat with no widening as the combustion
products flow into the firebox.
Required: Yes
Units: degrees (SI), degrees (US), degrees (MKH)
Default: None
Note
Xfh uses this parameter to calculate flue gas circulation in the firebox. The actual value depends on
the burner geometry, but 20° is a reasonable value.
Heat Release Factor/Burner
Specifies burners firing at different rates within the same gas space. For example, if Burner 2 fires at
twice the rate of Burners 1 and 3, specify 1, 2, 1 for the three burners, respectively.
Required: Yes
Units: None
Default: None
Note
Because the values are normalized, only the ratio between values matter. For example, a ratio of 1, 2,
1 for three burners is equivalent to actual values of 0.5, 1, 0.5.
Nominal Pressure Drop
This field represents an apparent or nominal pressure drop across the burner throat. This field is currently
not used by the calculation engine.
Required: No
Units: Pa (SI), in. H2O (US), mm H2O (MKH)
Default: 74.7 Pa (0.3 in H2O)
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F
Specifies a constant in the flame length equation. If you do not specify the flame length, Xfh calculates it
using the following:
BAF Duty)Burner(LengthFlame
Required: Yes (unless you specify flame length)
Units: None
Default: 1.0
Note
If you specify flame length, then Xfh calculates an apparent F.
A
Specifies a constant in the flame length equation. If you do not specify the flame length, Xfh calculates it
using the following:
BAF Duty)Burner(LengthFlame
Required: Yes (unless you specify flame length)
Units: m/MW (SI), ft hr/MM Btu (US), mm hr/MM kcal (MKH)
Default: 3.642 (3.5 US; 4232.8 MKH)
Note
If you select a burner from the internal databank, Xfh automatically enters the value in this field.
B
Specifies a constant in the flame length equation. If you do not specify the flame length, Xfh calculates it
using the following:
BAF Duty)Burner(LengthFlame
Required: Yes (unless you specify flame length)
Units: None
Default: None
Note
If you select a burner from the internal databank, Xfh automatically enters a value in this field.
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K
Specifies a constant in the burner throat pressure drop equation. The pressure drop across the burner
throat is calculated using
SI— 2VelocityDensity5021.0DropPressure K
US— 2locityDensity Ve003.0DropPressure K
MKH— 2locityDensity Ve0512.0DropPressure K
Required: Yes
Units: None
Default: None
Note
If you select a burner from the internal databank, Xfh automatically enters a value in this field.
Burner Group
Provides access to an internal databank of burner parameters. You may specify burner parameters
directly or select a specific burner from the internal tables. Choices include
User-defined
Axial air
Swirl air
Required: Yes
Units: None
Default: User-defined
Note
If you select Axial air or Swirl air, the Burner Code List button becomes active. Click this button to
select a burner from the internal databank.
Burner Code List button
Allows selection from the internal databank. To activate this button, select either Axial air or Swirl air in
the Burner Group field. Click to display a table of burner parameters; Xfh displays information appropriate
to the type of burner you select.
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Burner Code Panel
Allows selection of a burner from the internal databank. Select either Axial air or Swirl air in the Burner
Group field, and click the Burner Code List button on the Burner Parameters panel.
When the Burner Code panel appears, select the desired burner from the drop-down list below the burner
table.
Axial Air Burners
Swirl Air Burners
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Tube Locations Panel
This panel specifies the location and orientation of the tube coil within the box heater. You specify tube
coil parameters for each face (e.g., floor, left side) in each gas space.
Tube Coil Exists
Check the box to specify radiant tubes on a given wall of the box heater.
Required: Yes
Units: None
Default: Unchecked (tube coil does not exist)
Note
If you check this box for a given wall, you must complete the remaining fields for that wall.
Number of Tube Sections
Specifies the number of tube geometries on a given wall of the heater. Xfh can identify up to six different
geometries (e.g., tube outside diameters) on each wall that contains a tube coil.
Required: Yes (if tube coil exists on a wall)
Units: None
Default: 0
Note
If the outside diameter, wall thickness, center-to-center spacing, or length changes, you must specify
a different tube section.
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Tube Orientation
Specifies the tube coil orientation to the heater floor. You must specify the orientation for each wall
containing a tube coil.
Horizontal
Parallel to heater floor
Vertical
Perpendicular to heater floor
Side-to-Side
Between left/right walls on floor/roof
Front-to-Back
Between front/back walls on floor/roof)
Required: Yes (if tube coil exists on a wall)
Units: None
Default: None
Inside Return Bend
Sets the location of the U-bend inside or outside the firebox. You must specify the location for each wall
containing a tube coil. Check the box if the tube bend is inside the firebox. Xfh considers it heat transfer
area.
Required: Yes (if tube coil exists on a wall)
Units: None
Default: None
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Tube Section Geometry Panel
This panel specifies the geometry (e.g., tube outside diameter) of the tube coil on each wall of the firebox.
For each wall containing a tube coil, you must complete at least one row; if a wall contains multiple tube
sections, you must complete a row for each tube section.
Figure button
Display a context-sensitive graphic defining many of the geometry elements from the Tube Section
Geometry panel for box heaters. The drawing is specific to the box wall (e.g., side or roof) as well as the
tube orientation (e.g., horizontal or vertical). Items defined on this panel include
DX(1), DY(1), DZ(1)
Distance from the box wall to the first tube centerline along the X, Y, or Z axis
DX(2), DY(2), DZ(2)
Center-to-center distance between first and second tube sections
CC(1)
Center-to-center tube spacing for first tube section
CC(2)
Center-to-center tube spacing for second tube section
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Below is an example for horizontal tubes on a side wall.
DX, DY, DZ
Specify the distance to the center of the first tube in a section along the X (width), Y (depth), or Z (height)
axis. For Tube Section 1, the value represents the distance between the firebox wall and the centerline of
the first tube. For Sections 2 and beyond, the value represents the center-to-center distance between the
last tube of the previous section and the first tube of the current section.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
If you click the Figure button on the desired row, Xfh displays an illustration providing item definitions.
These values are relative to the endpoints of the straight length section of the tube.
Tube Outside Diameter
Specify the outside diameter for the current tube section.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
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Tube Wall Thickness
Specify the tube wall thickness for the tubes in an individual tube section. Enter the average wall
thickness.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Tube Ctr-Ctr Spacing
Specify the center-to-center distance between adjacent tubes in an individual tube section.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Tube Length
Specify the straight heated tube length for tubes in an individual tube section.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Tube Metallurgy
Specify the tube material for the box heater tube coil. Xfh uses this information to calculate the tube
thermal conductivity. Xfh allows you to select only one material for the firebox.
Required: Yes
Units: None
Default: MED-CS (Medium carbon steel)
Note
If the desired material is not listed, select OTHER, and specify the tube material thermal conductivity.
Tube Thermal Conductivity
Specify the thermal conductivity of the tube material for the box heater tube coil. Xfh uses this value to
calculate the outside metal temperatures from the bulk process temperatures inside the tube.
Required: No (unless you choose OTHER for tube metallurgy)
Units: W/m °C (SI), Btu/hr ft °F (US), kcal/hr m °C (MKH)
Default: None
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Number of Tubes
Specify the number of tubes in a tube section.
Required: Yes
Units: n/a
Default: None
Maximum Tube Length
Display the maximum value of the tube length input.
Required: n/a
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
The value entered for tube length cannot be longer than the value displayed in this field.
Wall Size (Available)
Display the available wall size for the tube coil layout. This value represents the distance available for
center-center placement of tubes.
Required: n/a
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
If the required wall size exceeds the available wall size, the Wall Size (Required) field turns red,
indicating that the tube coil arrangement is too large for the specified wall.
Wall Size (Required)
Display the required wall size for the tube coil layout. This value represents the amount of space required
the for specified center-center spacing of tubes.
Required: n/a
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
If the required wall size exceeds the available wall size, the Wall Size (Required) field turns red,
indicating that the tube coil arrangement is too large for the specified wall.
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Box Heater Tube Coil Geometry
Tube coil geometry varies according to the wall configurations:
Horizontal Tubes
On end walls
On the side
On the floor
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On the roof
Vertical Tubes
On end walls
On side walls
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Tubepass Sequence Panel
This panel allows you to specify the process flow path through each tubepass in the tube coil
arrangement using an interactive drawing.
Number of process passes
Select from this drop-down list box the number of process passes in the tube coil arrangement.
Required: Yes
Units: n/a
Default: None
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Set process pass
Select the active process pass and switch between passes.
Required: Yes
Units: n/a
Default: Pass 1
Note
After you select a process pass, click a tube in the drawing to put the tube in the selected pass.
Set tube number
In a process pass, set the tube number to indicate the order in which the process fluid flows through the
tube coil arrangement. Tube Number 1 is the process inlet.
Required: Yes
Units: n/a
Default: Pass 1
Note
After you select a process pass, click a tube in the drawing to change the tube number to the selected
tube number.
Clear Current Pass
Click to set all of the tubes in the selected pass (the pass number indicated in the Set Process Pass field)
to unassigned status.
Clear All Passes
Click to set all of the tubes to unassigned status.
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Tube Flow Direction Panel
This panel allows you to specify the flow directions of the process fluid for the inlet tube in each tube coil.
Each row in the table describes a tube segment: a group of contiguous tubes in the same gas space, on
the same wall, in the same tube section, and in the same process pass.
You see the results in the interactive drawing. When you select the 1st tube flow direction, the
corresponding tube number is highlighted.
Gas Space
Identifies the gas space in which the tube segment is located.
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Gas Space Wall
Identifies the surface in the gas space where the tube segment is located.
LS – Left Side
RS – Right Side
FE – Front End
BE – Back End
RF – Roof
FL – Floor
Wall Tube Section
Specifies the section in which the tube segment is located.
Process Pass
Sets the process pass for the tube segment.
Pass Sequence
Identifies the starting number of the pass sequence (the order that the process fluid winds through the
tube coil) for the tube segment.
1st Tube Flow Direction
Specify the flow direction of the process fluid in the first tube of a tube segment.
Required: Yes
Units: n/a
Default: Up, Right, Backward (depending upon tube orientation)
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Process Methods Panel
This panel provides input that allows you to adjust the methods used for process side (tubeside)
calculations.
Heat Transfer Coefficient Method
Pick the method used to calculate the heat transfer coefficient. The choices are
HTRI
Use proprietary HTRI methods for calculating process heat transfer coefficient
API530
Use method documented in API 530 to calculate process heat transfer coefficient
Required: Yes
Units: n/a
Default: HTRI
Note
The API 530 method for boiling is a proration of a sensible liquid and a sensible vapor coefficient.
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Pure Component
Select to use pure component methods.
Required: Yes
Units: n/a
Default: No (fluid is multi-component)
Note
If this field is set to Yes, the program does not include any mass transfer resistance in the calculation
of the heat transfer coefficient. This field has no effect for a sensible fluid.
Film Boiling Check
Choose whether or not the program checks for the presence of film boiling.
Required: Yes
Units: n/a
Default: Yes
Note
If you select Yes, Xfh will calculate film boiling heat transfer coefficients in regions where it determines
film boiling exists.
Because the film boiling mechanism involves the formation of an insulating film between the tube wall
and the bulk process fluid, film boiling coefficients can be significantly lower than normal boiling
coefficients.
Sometimes a case may have difficulty converging because Xfh predicts film boiling in only a few
increments. If you suspect film boiling calculations are causing convergence issues and that film
boiling is not a boiling mechanism for your case, try selecting No for this input.
Critical heat flux
Specify the critical heat flux.
Required: No
Units: W/m² (SI), Btu/hr ft² (US), kcal/hr m² (MKH)
Default: None
Note
This value overrides any program-calculated value for critical heat flux.
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Fraction of critical flux for film boiling
Specify the fraction of critical flux at which the program uses film boiling coefficient.
Required: No
Units: n/a
Default: None
Note
This value is used to set at what fraction of the calculated/specified critical flux the program assumes
film boiling is in effect. The default fraction is 1.0. A lower value is more conservative.
Sensible liquid coefficient
Specify the sensible liquid coefficient.
Required: No
Units: W/m² K (SI), Btu/hr ft² °F (US), kcal/hr m² °C (MKH)
Default: None
Note
This value overrides the program-calculated value for sensible liquid heat transfer coefficient.
Sensible vapor coefficient
Specify the sensible vapor coefficient.
Required: No
Units: W/m² K (SI), Btu/hr ft² °F (US), kcal/hr m² °C (MKH)
Default: None
Note
This value overrides the program-calculated value for sensible vapor heat transfer coefficient.
Boiling coefficient
Specify the boiling coefficient.
Required: No
Units: W/m² K (SI), Btu/hr ft² °F (US), kcal/hr m² °C (MKH)
Default: None
Note
This value overrides the program-calculated value for boiling heat transfer coefficient.
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Process fluid coefficient multiplier
Specify the process fluid heat transfer coefficient multiplier coefficient.
Required: No
Units: n/a
Default: 1.0
Note
The process fluid coefficient multiplier can be used to mimic tube internals that might enhance heat
transfer.
Tubeside friction factor
Choose the friction factor method to be used in pressure drop calculations. The available choices are
Commercial
Smooth
Large Pipe
Required: Yes
Units: n/a
Default: Commercial
Note
The large pipe method is the Chenowith-Martin method with the Colebrooke-White friction factor. The
method predicts a lower pressure drop than the commercial method for large pipes and high Reynolds
numbers. The method is documented in HTRI Report FH-3.
Process fluid friction factor multiplier
Specify a multiplier to the friction factor.
Required: Yes
Units: n/a
Default: 1.0
Note
This value multiples the program-calculated isothermal friction factor. It affects the pressure drop for
both single- and two-phase cases. Note that this value is not a direct multiplier on the pressure drop.
Surface roughness
Specifies an absolute surface roughness for the inside of the process piping.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: 0.02 mm (0.0007374 in.)
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Insulation Specification Panel
The heat loss in a box heater can be estimated by specifying insulating material definitions on this panel
or by specifying heat loss coefficients on the Heat Loss Coefficient panel.
Number of Layers
Specify the number of different layers of insulating materials present on each wall in the box heater.
Required: Yes
Units: None
Default: 1
Note
If insulation is identical on both end walls, Xfh uses the same number of layers on the front and back
ends. If insulation is identical on both side walls, Xfh uses the same number of layers on the left and
right sides.
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Same as Front End
Click to specify that the back end of a box heater has the same insulation as the front end.
Same as Left Side
Click to specify that the right side of a box heater has the same insulation as the left side.
Minimum/maximum temperature
Specify the range of inside refractory wall temperatures that Xfh uses in performing the heat loss
calculations. Unfortunately, Xfh does not yet print this information on reports.
Required: No
Units: °C (SI), °F (US), °C (MKH)
Default: 648.9 – 1260 °C (1200 – 2300 °F)
Note
Xfh generates a warning message if the temperature limits are exceeded.
Maximum outside wall temperature
Specify the maximum allowable outside wall temperature. Xfh calculates the expected outside wall
temperature for each wall as a function of the inside refractory wall temperature.
Required: No
Units: °C (SI), °F (US), °C (MKH)
Default: 93.3 °C (200 °F)
Note
The maximum inside refractory wall temperature will be limited either by exceeding the operating
range of the refractory or by exceeding the specified maximum outside wall temperature. Xfh prints
the minimum of these two values.
Average wind velocity
Specify the expected wind velocity on each vertical wall. Xfh calculates the outside convective heat
transfer coefficient (and expected heat loss) for each heater wall.
Required: No
Units: km/hr (SI), mi/hr (US), km/hr (MKH)
Default: 16.09 km/hr (10 mi/hr)
Note
The roof and floor surfaces use a separate convective heat transfer correlation that is not a function of
wind velocity.
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Material Thickness
Specify the thickness of the insulation material used in each layer on each wall. The first layer is the
material closest to the radiant gas space.
Required: Yes (for full insulation option)
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
Xfh issues a warning message if the total thickness on any wall is less than 38.1 mm (1.5 in.).
Material Code
Specify the insulation material used in each layer on each wall. The first layer is the material closest to
the radiant gas space.
Required: Yes (for full insulation option)
Units: None
Default: None
Note
Click the … button for a list of currently defined materials.
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User Defined Materials...
Click to access a dialog box that allows you to create user-defined insulation materials.
Select Insulation Material
When you click in the Insulation Material and Thickness table, you access the Select Insulation
Material dialog box, in which you can select an insulation material from a list of pre-defined materials. The
dialog also lists any user-defined materials you have created.
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User-Defined Insulation Materials
Specify up to four thermal conductivities to define an insulation/refractory material.
Material Name
Specify the name of the insulation material.
Required: Yes
Units: n/a
Default: None
Material Type
Specify the type of insulation material.
Required: Yes
Units: n/a
Default: None
Max. Service Temperature
Specify the maximum service temperature of the user-defined insulation material.
Required: Yes
Units: °C (SI), °F (US), °C (MKH)
Default: None
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Bulk Density
Set the bulk density for user-defined insulation material.
Required: Yes
Units: kg/m³ (SI), lb/ft³ (US), kg/m³ (MKH)
Default: None
Temperature
Specify the temperatures at which material thermal conductivities are provided.
Required: Yes
Units: °C (SI), °F (US), °C (MKH)
Default: None
Note
You may enter up to four temperature values. The input temperature points are used during the
calculation procedure in conjunction with the input thermal conductivities to interpolate thermal
conductivities.
Thermal Conductivity
Specify the thermal conductivity of any user-defined insulation material at a specified temperature.
Required: Yes
Units: W/m °C (SI), Btu/hr ft °F (US), kcal/hr m °C (MKH)
Default: None
Note
You may enter up to four thermal conductivity values. The input thermal conductivity data are used
during the calculation procedure in conjunction with the input temperatures to interpolate thermal
conductivities.
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Optional Panel
The Optional Panel provides additional flexibility in the way your heater is modeled. On this panel you can
adjust flue gas conditions, surface emissivities, convective weighting factors, and initial temperature
estimates.
Pressure in heater
Specify the pressure in a box heater.
Required: No
Units: kPa (SI), psia (US), kgf/(cm²) absolute (MKH)
Default: None
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Flue gas soot extinction coefficient
Specify the extinction coefficient for the flue gas.
Required: No
Units: 1/m (SI), 1/ft (US), 1/m (MKH)
Default: 0.0
Note
For gas fired heaters, set this value to 0.0.
For oil or mixed firing, set this value to 10% of the volume fraction of the firebox occupied by the
burner flames. For example, if the burner flames occupy 15% of the volume, set the extinction
coefficient to 0.10 (0.15) = 0.015.
Mean beam length
Specify the mean beam length for the firebox geometry.
Required: No
Units: m (SI), ft (US), m (MKH)
Default: 0.914 m (30 ft)
Note
Since Xfh uses a zoning method, the mean beam length used by the software (or specified by the
user) is not intended to represent the mean beam length of the actual heater. It is simply a starting
point that allows Xfh to fit gas emissivity as a function of KL (absorbtivity * path length).
Xfh takes the starting value and divides it several times to produce a range of beam lengths. Then
when calculating the exchange areas (effectively view factors for the individual zones), it bases actual
lengths between zones on the correlation previously developed. Thus, the value entered in Xfh needs
to provide for a proper range of values needed to develop the gas emissivity correlation.
The path length specified should be close to the maximum path length (typically, the diagonal) present
in the system. Unless the maximum beam length is significantly larger (several times), the default
value should be acceptable because zones that are far apart have smaller and smaller exchanger
areas.
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Process tube emissivity
Specify the emissivity factor to use in calculating the radiation heat transfer to the process tubes in the
firebox.
Required: No
Units: None
Default: 0.94 (Cylindrical), 0.60 (Box)
Note
Typical values are 0.94 for carbon steel and 0.60 for stainless steel. See Chapter 4 Appendix of
Radiative Transfer by H. C. Hottle and A. F. Sarofim for a compilation of additional emissivity values.
Refractory surface emissivity
Specify the emissivity factor for calculating the radiation heat transfer to/from the refractory surfaces in the
firebox.
Required: No
Units: None
Default: 0.60
Note
See Chapter 4 Appendix of Radiative Transfer by H. C. Hottle and A. F. Sarofim for a compilation of
additional emissivity values.
Convection weighting factors
Specify the weighting factors for free and forced convective heat transfer to the radiant tubes. These
factors are used as
Convective coefficient = (FFree x NuFree + FForced x NuForced)(TC/DT)
where
FFree = weighting factor for free convection
NuFree = Nusselt number for free convection
FForced = weighting factor for forced convection
NuForced = Nusselt number for forced convection
TC = thermal conductivity
DT = tube diameter
Required: No
Units: None
Default: Forced – 2.0
Free – 1.0
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Note
Default values are for horizontal tubes. For vertical tubes, a forced weighting factor of 1.5 is
recommended.
When using the No tubes option, the default forced convection factor is 0.25; the default free
convection factor, 0.20.
Momentum width factor for gas flow
This field specifies the point at which maximum flue gas recirculation occurs in the firebox. Xfh uses this
value to calculate the flue gas circulation profiles. Field data established the default value.
Required: No
Units: None
Default: 0.5
Note
Do not override this value unless you are trying to match plant data.
Initial gas zone temperature estimate
This field provides an estimated firebox gas temperature. Xfh uses this estimated value to start the firebox
convergence.
Required: No
Units: °C (SI), °F (US), °C (MKH)
Default: 1093 °C (2000 °F)
Note
Do not change this value unless the firebox calculations are not converging.
Initial refractory temperature estimate
This field provides an estimated refractory surface temperature. Xfh uses this initial value to start the
firebox convergence.
Required: No
Units: °C (SI), °F (US), °C (MKH)
Default: 816 °C (1500 °F)
Note
Do not change this value unless the firebox calculations are not converging.
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More information on Flow Field Simulation in Box Heaters
A simplified similarity of jet theory is used to calculate the flue gas flow field. In this model, there are three
axial regions in the jet direction and a fourth to account for exit locations as well as for flue gases entering
from other gas spaces. These regions are
1 Conservation of Momentum
2 Dissipation of Momentum
3 Plug Flow
4 Dissipation Flow
The maximum flue gas recirculation occurs at the plane that separates flow regimes 1 and 2. This
typically occurs when the radius of the expanding jet from the burner is about half the distance to the
nearest surface. This establishes the default for the momentum width factor for gas flow.
Once the maximum recirculation plane is crossed, momentum dissipates until the expanding jet occupies
the entire volume and the plug flow regime begins.
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Stack Panel
Use this panel to build the model of the stack by piecing together various stack elements. As stack
elements are added to the stack, input panels for each stack element appear under the Stack group.
Available Stack Items
Select from a list of available stack elements that can be modeled by the stack calculations.
Required: No
Units: n/a
Default: Unchecked
Stack Items List
View the selected stack elements that the stack calculations will model when you run the case.
Add New Stack Item
Click to add the stack item selected in the Available Stack Items list to the end of the Stack Items List.
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Insert New Stack Item
Click to insert the stack item selected in the Available Stack Items list to the Stack Items list. This button
allows you to choose where in the stack to insert a new stack item, inserting it above the item selected
(outlined) in the Stack Items list.
Delete Stack Items
Click to view dialog box that allows you to select the stack components that need to be deleted.
Reorder Stack Items
Click to view a dialog box that allows you to reorganize the stack components in the Stack Items list.
Soot extinction coefficient
Define the soot extinction coefficient for the flue gas in the convection section. This field is used for
radiant heat transfer calculations in the convection section.
Required: No
Units: 1/m (SI), 1/ft (US), 1/m (MKH)
Default: None
Note
In a fired heater where excess air is sufficient for essentially complete combustion, this value is less
than 0.01 and may be neglected. For large sooty flames, you may use the value of 0.0604 1/m
(0.0184 1/ft) [cited by A.M. Godridge and G.E. Hammond, Emissivity of a very large residual oil flame,
12th Sym. (Intl) on Combustion, 1219 (1968)].
Distance to first tuberow
Define the distance between the flue gas opening and the first row of convection tubes.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
If you enter a value in this field, Xfh calculates the amount of radiant energy from the firebox to the
convection section (shock duty) for cylindrical and box heater cases. If no value is entered, no shock
duty is calculated.
For cases with a convection section, the program calculates an effective roof sink surface emissivity to
mimic the shock tubes by using the distance to the first tuberow.
For cylindrical heater cases, when you specify both roof sink surface emissivity and the distance to the
first tuberow, Xfh uses the input value for the roof sink emissivity, overriding the calculated value of
the shock tube effective emissivity.
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Bridgewall temperature estimate
You may select to specify an initial guess for the bridgewall temperature. A good guess can improve the
speed of convergence as the case runs.
Required: No
Units: °C (SI), °F (US), °C (MKH)
Default: None
Stack Inlet Geometry - Shape
From this drop-down list box, specify the shape of the stack inlet geometry. Choices are
Rectangular
Round
Required: Yes
Units: n/a
Default: Rectangular
Stack Inlet Geometry - Width
Specify the width of the stack inlet geometry.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Stack Inlet Geometry - Depth
Specify the depth of the stack inlet geometry.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Feed Stream to Radiant Section
Specify which convection process stream enters the radiant section as the radiant process fluid.
Required: Yes
Units: n/a
Default: Inlet
Note
To have a separate process fluid in the radiant section, use the default value of Inlet for the feed
stream to radiant section.
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Bundle Panel
This panel contains overall geometry input and method options for bundle stack elements. A bundle
element represents contiguous rows of convection tubes containing the same process fluid.
Bundle layout type
This drop down list allows you to specify different layout types of the convection section bundle.
Required: Yes
Units: n/a
Default: Convection
Note
Different layout types are available.
Convection
Xfh sets up the bundle as parallel serpentine tube coils, typical in fired heater convection section
configurations.
Rows
Xfh sets up bundle using whole rows in each tubepass.
Fewer tubepasses than tuberows: first tubepass must be set up with more rows than other passes
Number of tubepasses evenly divisible into number of tuberows: all tubepasses have same number of
rows
Side-by-Side
Xfh sets up bundle with all tubepasses side by side in the bundle which can result in a non-standard
layout that could not be manufactured. Modify the layout on the Bundle Layout panel if necessary.
Rows/Side-by-Side
Xfh sets all rows except the last to be in the first tubepass. All other tubepasses are set up side by
side in last (bottom) tuberow.
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Equal Count
Xfh sets up the bundle so that the number of tubes in each tubepass is approximately the same.
Heated tube length
Specify the heated tube length for a bundle stack element.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
Because unheated lengths can be different depending on the type of tube used, they must be
specified in the tube type group.
Parallel passes (Convection)
Specifies the number of parallel flow paths for the process fluid in a convection section bundle.
Required: Yes
Units: None
Default: None
Note
Unlike parallel passes in shell-and-tube heat exchangers, this term does NOT indicate the number of
times the tubeside fluid passes back and forth across the convection section.
If you model twelve (12) tubes across a convection section and four (4) parallel passes, the program
assumes that the process fluid is divided four (4) ways. The first pass goes through Tube 1, then 2,
and then 3. The second pass goes through Tube 4, then 5, and then 6. The third pass uses Tubes 7,
8, and 9 while the fourth pass uses Tubes 10, 11, and 12.
Parallel elements (Stack)
Specifies the number of parallel copies of the current stack element. You can use this field to create
parallel stacks or sections of stacks. See Effect of Parallel Stack Elements for an example.
Required: No
Units: None
Default: 1
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Effect of Parallel Stack Elements
The flue gas flow entering each stack element is the total flue gas flow divided by the number of parallel
elements for each stack element. Total flue gas flow = 100 lb/hr.
Label Stack Element Type Number of
Parallel Elements
Flue Gas Flow, lb/hr
A Straight Duct 2 50
B Elbow 2 50
C Tee 1 100
D Straight Duct 1 100
Tubepasses
Specify the number of tubepasses for a bundle stack element.
Required: Yes
Units: n/a
Default: None
Note
The number of tubepasses is meant to indicate how many times the process fluid traverses from one
side of the bundle stack element to the other.
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Bundle width
Specify the inside width of a bundle stack element.
Required: No
Units: m (SI), ft (US), mm (MKH)
Default: None
Tube layout
Using this drop-down list box, specify the tubes in the bundle stack element as staggered or inline.
Required: Yes
Units: n/a
Default: None
Reverse staggered rows
Check this box if the stagger in the tuberows of a bundle stack element starts on the second row.
Required: Yes
Units: n/a
Default: Unchecked
Note
If this box is left unchecked, the stagger will begin on the first tuberow.
Process inlet
Specify where the process fluid enters a bundle stack element. Choice are
At flue gas exit
At flue gas inlet
Required: Yes
Units: n/a
Default: At flue gas inlet
Note
Essentially, this input determines if the process stream in a bundle stack element is cocurrent (at flue
gas inlet) or countercurrent (at flue gas outlet) with the flue gas stream.
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Corbels
Specify the presence of corbels in a bundle stack element.
Required: Yes
Units: n/a
Default: Yes
Use ESCOA outside methods
Specify whether the ESCOA methods should be used to calculate the heat transfer and pressure drop on
the flue gas side.
Required: Yes
Units: None
Default: No (Use HTRI methods)
Note
These ESCOA methods are taken from the ESCOA Engineering Manual.
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Bundle Layout Panel
This panel shows a graphical representation of a bundle stack element defined on the bundle panel. This
panel may also be used to edit the automatic bundle layout (e.g., change tube types used in bundle
rows).
User-defined tubepass layout
Indicates if the bundle layout has been modified from the automatically generated layout.
Required: No
Units: n/a
Default: Unchecked
Note
If you right-click on the bundle layout and edit it, this box is automatically checked.
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Number of tuberows
Specify the number of tuberows in a bundle stack element.
Required: Yes
Units: n/a
Default: None
Number of tubes in each row / Number of tubes per row
Specify the number of tubes in each row of a bundle stack element.
Required: Yes
Units: n/a
Default: None
Left wall clearance / Clearance, wall to first tube
Specify the distance from the left wall to the first tube in a bundle stack element.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Stack Element Panels
Depending on which stack elements are selected, stack element panels will appear and require input.
The possible stack element panels are
Convection bundle
Damper
Straight duct
Sudden contraction
Gradual contraction
Sudden enlargement
Gradual enlargement
Sudden exit
User-defined fitting
90-degree elbow
45-degree elbow
90-degree mitered elbow
Tee
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Stack element height
Specify the height of the following stack elements:
Damper
Straight duct
Gradual contraction
Gradual enlargement
User-defined fitting
90-degree elbow
45-degree elbow
90-degree mitered elbow
Tee
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: n/a
Note
Only vertical elements affect the stack draft calculations.
Stack element length
Specify the length of the following stack elements:
Damper
Straight duct
Gradual contraction
Gradual enlargement
User-defined fitting
90-degree elbow
45-degree elbow
90-degree mitered elbow
Tee
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: n/a
Stack element orientation
Select the orientation of the following stack elements:
Damper
Straight duct
Sudden contraction
Gradual contraction
Sudden enlargement
Gradual enlargement
Sudden exit
User-defined fitting
90-degree elbow
45-degree elbow
90-degree mitered elbow
Tee
Choices
Horizontal
Vertical
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Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: Vertical
Stack element flow direction
Specify the flow direction within the following stack elements:
Damper
Straight duct
Sudden contraction
Gradual contraction
Sudden enlargement
Gradual enlargement
Sudden exit
User-defined fitting
90-degree elbow
45-degree elbow
90-degree mitered elbow
Tee
Choices
Upflow
Downflow
Required: Yes
Units: n/a
Default: Upflow
Stack element fitting loss coefficient
Define the fitting loss coefficient for the following stack elements:
Damper
Sudden contraction
Gradual contraction
Sudden enlargement
Gradual enlargement
Sudden exit
User-defined fitting
90-degree elbow
45-degree elbow
90-degree mitered elbow
Tee
Required: Yes (if pressure drop is unspecified)
Units: n/a
Default: None
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Note
Stack element pressure drop is calculated for a fitting or cross-section change using
23)10(989.2 vCP
where
C = fitting loss coefficient
p = flue gas density (lb/ft³)
v = flue gas velocity (ft/s)
Stack element pressure drop
Specify the pressure drop over a stack element. This input applies to
Damper
Straight duct
Sudden contraction
Gradual contraction
Sudden enlargement
Gradual enlargement
Sudden exit
User-defined fitting
90-degree elbow
45-degree elbow
90-degree mitered elbow
Tee
Required: No
Units: kPa (SI), psi (US), kgf/cm² (MKH)
Default: None
Note
This pressure drop overrides any value calculated by the program.
Stack element relative roughness
Specify the relative roughness of the stack element material.
Required: No
Units: n/a
Default: None
Note
The relative roughness ( /D) is a dimensionless quantity that is defined as the absolute roughness of a
material divided by the hydraulic diameter of the conduit. Using a table of the absolute roughness of
some common surfaces, you can obtain an appropriate absolute roughness and then divide it by the
hydraulic diameter of the stack element to determine the relative roughness.
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Stack element miter pieces
Specify the number of miter pieces in a 90-degree mitered elbow.
Required: Yes
Units: n/a
Default: 2
Note
A 90-degree mitered elbow may have 2 to 5 miter pieces in the stack element.
Stack element friction factor
Set the friction factor for a Straight duct.
Required: No
Units: n/a
Default: Unchecked
Note
This value overrides the value calculated from the Colebrooke-White equation.
Stack element outlet geometry - shape
From this drop-down list box, select the shape of the following stack elements:
Sudden contraction
Gradual contraction
Sudden enlargement
Gradual enlargement
User-defined fitting
Tee
Choices
Rectangular
Round
Required: Yes
Units: n/a
Default: Rectangular
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Stack element outlet geometry - depth
Specify the outlet geometry depth of the following stack elements:
Sudden contraction
Gradual contraction
Sudden enlargement
Gradual enlargement
User-defined fitting
Tee
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
This field is used only for rectangular elements.
Stack element outlet geometry - width
Specify the outlet geometry width of the following stack elements:
Sudden contraction
Gradual contraction
Sudden enlargement
Gradual enlargement
User-defined fitting
Tee
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
This field is used only for rectangular elements.
Stack element outlet geometry - diameter
Set the outlet geometry diameter of the following stack elements:
Sudden contraction
Gradual contraction
Sudden enlargement
Gradual enlargement
User-defined fitting
Tee
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Stack element bend radius
Specify the bend radius of the following stack elements:
90-degree elbow 45-degree elbow 90-degree mitered elbow
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
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Stack element take-off angle
From this drop-down list box, select the take-off angle of a Tee:
Required: Yes
Units: degrees (SI), degrees (US), degrees (MKH)
Default: 90 degrees
Absolute Roughness of Common Surfaces
Source: R. Darby, Chemical Engineering Fluid Mechanics, 151 (1996).
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Tube Types Panel
This introductory panel allows you to choose tube types. Each tube type has different geometry and f-and
j-curve input pages; high-finned, low-finned, stud-finned tubes and twisted tape inserts have further input
pages.
Tube name
Designates tube type plus number, i.e., TubeType1 is the first type of tube.
Required: Yes
Units: None
Default: TubeTypen where n is 1, 2, 3, 4, up to 9
Tube internal
Defines geometry of tube internal devices (e.g., inserts).
Twisted tape
None
Required: No
Units: None
Default: None
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Notes
Xfh supports twisted tapes for single-phase and boiling fluids only.
Add tube type
Adds another tube type to list.
Delete tube type
Deletes highlighted tube from list. To select a tube type, click number in first column.
Tubes page
Fields on this page define tube geometry of your heat exchanger. Enter Tube OD, Wall thickness, and
Transverse pitch; all other fields are optional. This page repeats for each tube type.
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Tube type
Specifies type of tube used in exchanger bundle: Plain, low-finned, high-finned, or stud-finned (available
only with economizers).
Plain Tube
Low-Finned Tube
Stud-Finned Tube
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High-Finned Tube
Required: No
Units: None
Default: Plain
Note
If you specify other than Plain, you must furnish additional information on a subsequent panel.
Databank Type
When you select fin geometry in this field, you must also select an available tube size from Tube
dimensions list.
After you select a databank type, Tube dimensions list displays tube sizes for which that fin geometry
is available.
Xfh automatically enters all geometry fields on panel when you select from Tube dimensions list.
Select Not in Databank if you do not find fin geometry or tube dimension you want, and then
manually enter fin geometry values in geometry fields on Fins panel.
You can override individual geometry items after you select a databank type.
Tube internals
Defines geometry of tube internal devices (e.g., inserts):
twisted tape
micro-fin
none
Required: No
Units: None
Default: None
Tube material code
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Specifies material from which tube is made. Select from built-in list of materials. If you select <Not in
databank>, you must specify Tube thermal conductivity.
Required: No
Units: None
Default: Carbon steel
Tubes and Fin Materials and Dimensions
Tube materials
Selecting tube material for air coolers, unlike the tube selection process for shell-and-tube or bare-
tube designs, depends more on stress and corrosion resistance than on the effects of heat transfer.
Tube material generally has little effect on overall weighted fin and tube efficiency, whether the tube is
a high conductivity material like copper, about 391 W/m K (226 Btu/hr ft °F), or most stainless steel
materials, 17.3 W/m K (10 Btu/hr ft °F). Consequently, fin material and dimensions are more critical
design factors.
Fin materials
Stainless steel or carbon steel fins, conductivity about 43.3 W/m K (25 Btu hr ft °F), can make fin
efficiency (or total metal resistance) the dominant design factor. Conversely, using copper fins versus
aluminum fins, conductivity about 207.6 W/m K (120 Btu/hr ft °F), does not affect overall design
significantly, because the effect on fin efficiency becomes more or less asymptotic for most fin-side
conditions.
Fin dimensions
In most cases, designing a finned tube to maintain fin efficiency above 80% offers a better design and
a more economical selection. Changing fin height is the most suitable approach for this improvement.
Tube thermal conductivity
Specifies thermal conductivity of tube material. Use this field when your tube material is not in the Tube
Material Databank.
Required: No
Units: W/m °C (SI), Btu/hr ft °F (US), kcal/hr m °C (MKH)
Default: The program uses the Tube Material Code in its thermal conductivity calculations and
provides a default value unless you select Not in Databank.
Tube emissivity
Define the emissivity of tubes in the convection section.
Required: No
Units: None
Default: Emissivity of tubes in radiant section
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Note
This field is used to calculate the radiant heat transfer between the radiant section and the shock
tubes in the convection section.
Wall thickness
Specifies average wall thickness of tube directly or in terms of BWG (Birmingham Wire Gage) value. For
low-finned tubes and tubes with embedded fins, this value is the plain end wall thickness.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
The entered value must be less than half the tube diameter. This value affects tubeside flow area. The
button to right of this field displays a worksheet that allows you to specify wall thickness in terms of
BWG.
Standard Wall Thicknesses
BWG mm in.
10 3.4036 0.134
11 3.0480 0.120
12 2.7686 0.109
13 2.4130 0.095
14 2.1082 0.083
15 1.8288 0.072
16 1.6510 0.065
17 1.4732 0.058
18 1.2446 0.049
19 1.0668 0.042
20 0.8890 0.035
21 0.8128 0.032
22 0.7112 0.028
23 0.6350 0.025
24 0.5588 0.022
25 0.5080 0.020
Tube OD
Specifies the outside diameter of the tubes. For low-finned tubes, enter the plain end diameter. The drop-
down list contains various standard tube diameters.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: 25.4 mm (1.0 in.)
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Note
You may select a value from the list or enter another value. The entered value must be larger than
twice the tube wall thickness.
Left wall clearance
Define the clearance between the tube wall and the inside of the left refractory wall for the first tuberow in
the current tube section.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
For a staggered layout, this field specifies the closest distance between the tube wall and the
refractory wall. Alternate rows have a larger clearance.
Unheated length/row
Specify the unheated length per row of tubes. Typically, this value equals the distance inside the
convection section walls.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
This distance is used to calculate the proper process tubeside pressure drop.
Unheated length between rows
Specify the extra length of piping used to connect the process tuberows in the convection section.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
This distance is used to calculate the proper process tubeside pressure drop.
Equilateral layout
When you select this option, the program disables the longitudinal pitch entry, forcing equilateral tube
pitch layout and calculating the value from the transverse pitch (longitudinal pitch = 0.866 • transverse
pitch).
Required: No
Units: None
Default: Unchecked
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Longitudinal pitch
Define the center-to-center spacing between rows of tubes in the direction of flue gas flow.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
For a staggered layout, this field specifies the closest distance between the tube wall and the
refractory wall. Alternate rows have a larger clearance.
Tube Layout Types
Transverse pitch
Define the center-to-center spacing between tubes in a row across the convection section bundle.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
For a staggered layout, this field specifies the closest distance between the tube wall and the
refractory wall. Alternate rows have a larger clearance.
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FJ Curves page
Items on this page allow you to override internal heat transfer and pressure drop correlations. If you have
more than one tube type in bundle, additional f- and j-curves pages appear for each tube type.
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Outside/airside f- and j-factors
Overrides internal outside/airside heat transfer (j-factor) and pressure drop (f-factor) correlations. If you
specify values, Xfh calculates f- and/or j-factors using supplied values. Use this option to enter
experimental data directly into program.
Enter f- and j-factors in one of 2 ways:
Specify values at 2 or 3 Reynolds numbers.
OR
Enter a and b constants as a function of Reynolds numbers.
Required: No
Units: None
Default: Use internal correlations
Tubeside f- and j-factors
Overrides internal tubeside heat transfer (j-factor) and pressure drop (f-factor) correlations. If you specify
values, Xfh calculates f- and/or j-factors using supplied values. Use this option to enter experimental data
directly into program.
Enter f- and j-factors in one of 2 ways:
Specify values at 2 or 3 Reynolds numbers.
OR
Enter a and b constants as a function of Reynolds numbers.
Required: No
Units: None
Default: Use internal correlations
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More Information on f- and j-Curves
Outside f and j-Factors
The f- and j-factors are geometry-dependent. Take care to assure that values you enter are for tube and
tube pattern specified.
Equation Forms
The equation forms that Xfh uses when you input outside f- and j-factors appear below:
24
2
x
c
rx G
g
N
Pf
hxp
o
GC
hj
32Pr
where
Cp Fluid heat capacity
gc Gravitational constant
Gx Mass velocity
ho Heat transfer coefficient
Nrx Number of tuberows crossed
P Pressure drop
Pr Prandtl number
Fluid density
Tube row correction factor
h Physical property correction factor
Tubeside f- and j-Factors
When you enter tubeside f- and j-factors, Xfh uses a Reynolds number based on plain inside diameter.
Convert any values you enter to that basis.
Equation Forms
The equation forms that Xfh uses when you input tubeside f- and j-factors appear below:
D
LG
Pgf c
24
2
hxp
o
GC
hj
32Pr
where
Cp Fluid heat capacity
D Tube inside diameter
gc Gravitational constant
G Mass velocity
h Heat transfer coefficient
k Thermal conductivity
L Length
Pr Prandtl number
P Pressure drop
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Fluid density
h Physical property correction factor
For more information on f- and j-factors, consult sections Single-Phase Pressure Drop and Single-Phase
Heat Transfer in Design Manual.
Low Fins page
Use items on this page to define low-finned tube geometry. This page appears only when you choose
Low-finned on Tube Types panel.
Fin material
Specifies material from which fins are made. Select from a list of built-in materials, or specify fin material
thermal conductivity.
Required: No
Units: None
Default: Aluminum 1060-H14
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High Fins page
Use items on this page to define high-finned tube geometry. This page appears only when you choose
High-finned on the Tube Types panel.
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Stud Fins page
Use items on this page to define stud-finned tube geometry. This page appears only when you select
Stud-finned for Tube Type on the Tube Types panel.
Fin bond resistance
Specifies fin bond resistance. If you do not enter a value, the program assumes no bond resistance.
Required: No
Units: m² K/W (SI), ft² hr °F/Btu (US), m² hr °C/kcal (MKH)
Default: None
Note
– Integral finned tubes
These tubes have zero bond resistance.
– Imbedded finned tubes
These tubes have zero bond resistance.
– Tension-wound tubes
At elevated temperatures (typically above 176 °C (350 °F)), fin can separate from tube, resulting
in marked decrease in heat transfer.
– Bimetallic tubes
Any value you enter for fin bond resistance can be considered to be resistance between tube and
sleeve. New bimetallic tubes have no bond resistance.
The program adds entered value directly as resistance in overall heat transfer coefficient calculations.
It is not added to calculated outside heat transfer coefficient and is not corrected for area ratio.
Therefore, the value you enter must be based on extended surface area of tube and not actual bond
area.
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Fin efficiency
Specifies fin efficiency. Usually you should not enter a value because the program calculates it. However,
if you input j-curves on f- and j-Curves panel and have already included efficiency in given j-factors, enter
an efficiency of 100%.
Required: No
Units: percent
Default: None
Note
Do not enter efficiency values as a fraction.
Number of stud rings
Specifies number of stud rings per unit length of tube.
Required: For stud-finned tubes
Units: stud/m (SI), stud/ft (US), stud/m (MKH)
Default: None
Number of studs in each ring
Indicates number of studs per ring.
Required: For stud-finned tubes
Units: None
Default: None
Stud length
Specifies length of studs welded to tube.
Required: For stud-finned tubes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Typical Stud-Finned Tube Geometry
Typical Range Most Common Value Item
SI US SI US
Tube diameter 63.5 – 222 mm 2.5 – 8.75 in. 114.3 mm 4.5 in.
Stud diameter 6.35 – 12.7 mm 0.25 – 0.5 in. 12.7 mm 0.5 in.
Stud length 12.7 – 57.15 mm 0.5 – 2.25 in. 25.4 mm 1.0 in.
Fin material Carbon steel, stainless Carbon steel
Tube material Carbon steel, stainless Carbon steel
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Typical Maximum Stud Density
Tube Diameter Maximum Studs per Row for Stud Diameters, mm (in.)
mm in. .0 (0.24) 0.0 (0.4) 12.0 (0.47) 12.5 (0.49)
219.0 8.625 51 38 34 32
168.3 6.625 39 29 26 24
141.3 5.563 33 25 22 20
114.3 4.5 26 20 18 16
101.6 4.0 23 16 16 15
88.9 3.5 22 14 14 12
73.0 2.875 17 12 11 10
60.3 2.375 14 10 9 8
50.8 2.0 12 8 7 7
Stud diameter
Specifies diameter of stud.
Required: For stud-finned tubes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Twisted Tape page
Use this panel to define the geometry of twisted tapes. Xfh supports twisted tapes for boiling, condensing,
and single-phase fluids.
Thickness
Specifies thickness of a twisted tape insert.
Required: Yes (for twisted tape inserts)
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
To specify twisted tape inserts, you must enter values in all fields on this page.
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L/D 360-degree twist
Specifies longitudinal length for one complete rotation of twisted tape divided by width of the tape (L/D).
Required: Yes (for twisted tape inserts)
Units: None
Default: None
Note
To specify twisted tape inserts, you must enter values in all fields on this page. Correlations are based
on HTRI and industrial data for twisted tapes with an L/D from 8 through 16.
Width
Specifies the width of a twisted tape insert.
Required: Yes (for twisted tape inserts)
Units: mm (SI), in. (US), mm (MKH)
Default: Tube inside diameter
Note
To specify twisted tape inserts, you must enter values in all fields on this page.
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Tube Sink Definition Panel
Using this panel, you specify the tube sink properties in each zone along each wall.
Note
The Tube Sink Definition panel is available when you select the No Tubes option button on the Box
Heater summary panel. This option directly sets the surface zone properties (e.g., fraction sink) that
are normally calculated from specified tube geometry.
Fraction sink
With the input grid, specify how much of the surface zone is covered by a heat sink.
Required: Yes
Units: n/a
Default: 0.0
Note
The default corresponds to all refractory in the surface zone.
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Emissivity of sink
Specify the emissivity of the heat sink in each zone.
Required: Yes
Units: n/a
Default: 0.7
Note
The default corresponds to all refractory in the surface zone.
Fraction open
Specify how much of the zone is neither covered by refractory or heat sink area.
Required: Yes
Units: n/a
Default: 0.0
Note
The default corresponds to a solid refractory wall in the surface zone.
Convective weight factor
Specify how much weight to place on convective heat transfer.
Required: Yes
Units: n/a
Default: 1.0
Sink temperature
Identify the temperature of the sink in each zone along each wall.
Required: No (unless fraction sink is not zero)
Units: °C (SI), °F (US), °C (MKH)
Default: None
Note
This value corresponds to the tube front wall temperature in a defined tube geometry case.
Enter data for wall
From the drop-down list, select the wall for which you want to specify radiative properties.
Required: n/a
Units: n/a
Default: Front End
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Note
When you select a wall, the values in the grid change to those specified for that wall.
Reset Current Wall
Reset the radiative properties on the currently selected wall to the default values.
Reset All Walls
Reset the radiative properties on all walls to the default values.
Radiant Box Panel
Using this panel, you identify the geometry and heater specifications of a single-zone heater.
Note
The Radiant Box panel is available when you select Single Zone as the radiant section type on the
Case Configuration panel.
Heater type
From this drop-down list box, select the geometry type for a single-zone heater.
Available Geometries
Box
Cylindrical
Required: Yes
Units: n/a
Default: Box
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Number of tubepasses
Specify the number of tubepasses in a single-zone heater.
Required: Yes
Units: n/a
Default: None
Number of radiant tubes
Specify the number of tubes in the radiant section of a single-zone heater.
Required: Yes
Units: n/a
Default: None
Height
Set the height of a single-zone heater.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Width
Specify the width of a single-zone heater.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
This input field appears for a box heater type.
Depth
Specify the depth of a single-zone heater.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
This input field appears for a box heater type.
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Diameter
Set the diameter of a single-zone heater.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
This input field appears for a cylindrical heater type.
Specified
Select a heater specification to define as input for a single-zone heater. An accompanying input field lets
you set the magnitude of the heater specification. Xfh calculates the other items in the list when the case
is run.
Heater Specifications
Outlet flue gas temperature
Radiant section duty
Thermal stirring factor (see note below)
Required: Yes
Units: Outlet flue gas temperature—°C (SI), °F (US), °C (MKH)
Radiant section duty—MW (SI), MM Btu/hr (US), MM kcal/hr (MKH)
Thermal stirring factor—none
Default: Radiant section duty
Note
The thermal stirring factor thermF is defined as
)()(4444
ksineffksinouttherm TTTTF
where outT is the outlet flue gas temperature, ksinT is the effective cold sink temperature, and effT is
the effective gas radiating temperature.
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Heat loss
Choose from this drop-down list box a method for specifying the heat loss in a single-zone heater. Then
specify the magnitude of the heat loss in the accompanying input field.
Heat Loss Options
Absolute loss
Fraction of heat input
Required: Yes
Units: Absolute loss—MW (SI), MM Btu/hr (US), MM kcal/hr (MKH)
Fraction of heat input—n/a
Default: Fraction of heat input
Outside convective heat transfer coefficient
Specify the outside heat transfer coefficient for a single-zone heater.
Required: Yes
Units: W/m² K (SI), Btu/ft² hr °F (US), kcal/m² hr °C (MKH)
Default: None
Tube Zones Panel
Specify a tube zone for each set of tube geometry present in a heater.
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First tube in zone
Specify the location of the first tube in each tube zone.
Required: Yes
Units: n/a
Default: 1
Tube position
Describe the position of the tubes in the tube zone.
Positions
Inner
Outer
Required: Yes
Units: n/a
Default: Inner
Tube firing
Specify how the tubes see the flame.
Options
Single
Sng/Dbl
Double
Dbl/Dbl
Three Cnv
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Sgl
Single row adjacent to wall, fired from one side
Dbl
Two rows adjacent to wall, fired from one side
Sgl/Dbl
Single row, fired from both sides
Dbl/Dbl
Two rows fired from both sides
Three Cnv
Three rows of bare convection tubes
Required: Yes
Units: n/a
Default: Single
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Tube outside diameter
Define the tube outside diameter
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Tube inside diameter
Define the tube inside diameter.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Center-to-center spacing
Specify the center-to-center spacing of the tubes in a tube zone.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Heated lengths
Specify the heated lengths of the tubes in a tube zone.
Required: Yes
Units: m (SI), in. (US), mm (MKH)
Default: None
Tube thermal conductivity
Set the thermal conductivity of the tubes in a tube zone.
Required: Yes
Units: m (SI), in. (US), mm (MKH)
Default: None
Tube emissivity
Define the emissivity of the tube surface in a tube zone.
Required: No
Units: n/a
Default: 0.94
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Coke thickness
Specify the thickness of the coke layer on the outside of the tubes in a tube zone.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: 0.0
Coke thermal conductivity
Define the thermal conductivity of the coke layer on the outside of the tubes in a tube zone.
Required: No
Units: W/m °C (SI), Btu/hr ft °F (US), kcal/hr m °C
Default: None
Process fouling factor
Specify the fouling factor inside the tubes in a tube zone.
Required: No
Units: m² K/W (SI), ft² hr °F/Btu (US), m² hr °C/kcal (MKH)
Default: None
Longitudinal max/avg flux ratio
Specify the longitudinal variation in the maximum/average flux ratio.
Required: Yes
Units: m² K/W (SI), ft² hr °F/Btu (US), m² hr °C/kcal (MKH)
Default: None
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Radiant Box Process Conditions Panel
On this panel, you define the process fluid for a single-zone heater.
Fluid name
Assign a name to the process fluid.
Required: No
Units: n/a
Default: n/a
Process flow rate
Define the flow rate of the process fluid.
Required: Yes
Units: kg/s (SI), lb/hr (US), kg/hr (MKH)
Default: None
Pressure
Specify the inlet and outlet pressures of the process fluid.
Required: Yes
Units: kPa (SI), psia (US), kgf/cm² (MKH)
Default: None
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Bulk temperature
Specify the inlet and outlet temperatures of the bulk process fluid.
Required: Yes
Units: °C (SI), °F (US), °C (MKH)
Default: None
Bulk temperature at wall
Define the inlet and outlet wall temperatures of the bulk process fluid.
Required: Yes
Units: °C (SI), °F (US), °C (MKH)
Default: None
Weight fraction vapor
Specify the inlet and outlet weight fraction vapor of the bulk process fluid.
Required: Yes
Units: n/a
Default: 0.0
Note
A weight fraction that equals 0.0 indicates the fluid is all liquid—you can specify only liquid physical
properties. A weight fraction of 1.0 indicates all vapor—you can specify only vapor physical properties.
If the weight fraction vapor is greater than 0.0 but less than 1.0, a two-phase fluid is indicated—you
must specify vapor and liquid properties.
Thermal conductivity
Specify the inlet, outlet, liquid, and vapor thermal conductivities of the fluid in a single-zone heater.
Required: Yes
Units: W/m °C (SI), Btu/hr ft °F (US), kcal/kg °C (MKH)
Default: None
Viscosity
Specify the inlet, outlet, liquid, and vapor viscosities of the fluid in a single-zone heater.
Required: Yes
Units: mN s/m² (SI), cP (US), cP (MKH)
Default: None
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Note
A weight fraction that equals 0.0 indicates the fluid is all liquid—you can specify only liquid physical
properties. A weight fraction of 1.0 indicates all vapor—you can specify only vapor physical properties.
If the weight fraction vapor is greater than 0.0 but less than 1.0, a two-phase fluid is indicated—you
must specify vapor and liquid properties.
Viscosity at wall
Specify the inlet, outlet, and liquid wall viscosities of the fluid in a single-zone heater.
Required: Yes
Units: mN s/m² (SI), cP (US), cP (MKH)
Default: None
Note
Wall viscosity is applicable only when a liquid phase is present in the fluid.
Specific heat
Define the inlet, outlet, liquid, and vapor viscosities of the fluid in a single-zone heater.
Required: Yes
Units: kJ/kg °C (SI), Btu/lb °F (US), kcal/kg °C (MKH)
Default: None
Note
A weight fraction that equals 0.0 indicates the fluid is all liquid—you can specify only liquid physical
properties. A weight fraction of 1.0 indicates all vapor—you can specify only vapor physical properties.
If the weight fraction vapor is greater than 0.0 but less than 1.0, a two-phase fluid is indicated—you
must specify vapor and liquid properties.
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Combustion Module
A combustion calculation involves burning a fuel in the presence of an oxidant. Optionally steam may be
added as a diluent. There are multiple options for specifying the type and composition of each stream in
the combustion process. This calculation can be run independently or as part of a complete fired heater
simulation.
The program allows specification of either one or two fuels to burn each with its own oxidant and diluent
streams. When run, the combustion calculation produces the outlet temperature of the combustion
process as well as compositions and properties of the inlet and outlet streams.
The combustion group contains the following panels:
Combustion panel
Oxidant Air panel
Oxidant Gas panel
Diluent panel
Gas panel
Fuel Oil panel
Liquid/Solid panel
Combustion Calculations
Combustion calculations are performed on defined fuels. Typically, you’ll use this module in conjunction
with the Cylindrical or Box module, but you can also run it by itself.
Multiple Fuel Types
Defined gas composition (1 – 10 components from a list of 19)
Fuel oil (Ultimate analysis or API Gravity/Grade/Specific gravity)
Liquid (Ultimate analysis)
Solid (Ultimate analysis)
Oxidant Types
Ambient air
Preheated air
Defined gas composition
Diluent Stream
None
Steam
Flow Rate Specification
Fuel by mass, volume, or heat release
Oxidant by mass, volume, % excess, % O2 after combustion, or fraction of fuel
Diluent by mass, volume or wt/wt of fuel
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1 or 2 Fuels in Combustion Calculations
Temperature
Composition of combustion stream
Heat release
Physical properties of combustion stream
Limitations
No NOx prediction
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Combustion Panel
This panel lets you specify the number and properties of the fuel, oxidant, and diluent streams to be
combusted. You may also specify any duty losses associated with the combustion process.
Number of fuels
Select number of fuels mixed in the combustion process. You may select 1 or 2 fuels.
Required: Yes
Units: None
Default: 1
Oxidant type
Select the type of oxidant stream used in the combustion process. The oxidant stream mixes with the fuel
to initiate and maintain ignition and to provide stable flame shape for effective heat transfer. From the
drop-down list, select gas, ambient air, or preheat air.
Required: Yes
Units: None
Default: Ambient air
Note
Specify properties for the oxidant stream by clicking on the corresponding Properties button.
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Diluent type
Select whether steam will be used as a diluent in the combustion process. Steam is typically used to
atomize the fuel oil before burning and to control the NOX emission when fuel gas is used in the main fuel
stream. From the drop-down list, select steam or none if the burner does not use a diluent stream.
Required: Yes
Units: None
Default: Steam
Note
Specify properties for the diluent stream by clicking on the corresponding Properties button.
Fuel type
Select the type of fuel used in the combustion process. From the drop-down list, select gas, fuel oil,
liquid, or solid.
Required: Yes
Units: None
Default: Fuel oil
Note
Specify properties for the fuel stream by clicking on the corresponding Properties button.
Fuel Gas Calculation Options
Specify several options available for the combustion calculation. The choices are
Generate flue gas as combusted — flue gas temperature is predicted based on burning fuel
as entered with no losses.
Specify flue gas temperature — program calculates duty added or removed to achieve
specified flue gas temperature
Specify duty and losses to be subtracted — program calculates flue gas temperature after
adding or removing specified losses.
Required: Yes
Units: None
Default: Generate flue gas as combusted
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Flue gas temperature
Specify the desired flue gas temperature.
Required: Yes (If Specify flue gas temperature option selected)
Units: C (SI), F (US), C (MKH)
Default: None
Note
Program will add or subtract duty (and report the amount) to the combustion process to achieve the
desired flue gas temperature.
Radiant duty
Specify the duty that should be removed from the combustion process in calculating the flue gas
temperature. This can be used to simulate the process duty that would be removed in a radiant firebox.
Required: No
Units: Megawatts (SI), MM Btu/hr (US), MM kCal/hr (MKH)
Default: 0.0 (Adiabatic)
Heat loss
Specify the percentage of the combustion duty that should be removed before calculating the flue gas
temperature. This option can be used to model losses in a radiant firebox.
Required: No
Units: Percent of duty
Default: 0.0
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Fuel Oil Panel
This panel describes the flow rate, properties, and compositions of a fuel oil stream used in a combustion
calculation.
Pressure
Specify the pressure of the fuel stream used in the combustion process.
Required: No
Units: kPa (SI), psia (US), kgf/cm² (MKH)
Default: 0.0
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Flow
Specify the flow rate of the fuel stream. The units of this property will depend upon the selection made for
the Fuel Flow Units field.
Required: Yes
Units: SI US MKH
Mass kg/hr lb/hr kg/hr
Volume m³/hr ft³/hr m³/hr
Mole kg-mol/hr lb-mol/hr kg-mol/hr
Duty Megawatts MM BTU/hr MM Kcal/hr
Default: None
Temperature
Specify the temperature of the fuel stream used in the combustion process.
Required: No
Units: C (SI), F (US), C (MKH)
Default: 80 °F (26.67 C)
Lower heating value
Specify the higher heating value minus the latent heat of vaporization of the water formed by combustion
of hydrogen in the fuel. It is sometimes called the net or useful heating value. For fired heaters, use lower
values.
Required: No
Units: kJ/kg (SI), Btu/lb (US), kCal/kg (MKH)
Default: None
Characterization factor
This is an optional input item. However, the Watson Characterization factor for the fuel oil should be
specified; otherwise, the program computes this value. Based on degree API and Watson
characterization factor, the program computes the average and the ASTM 50% boiling points, the
molecular weight, and the thermal conductivity of the fuel oil.
Required: No
Units: None
Default: Program calculated
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Higher heating value
Specify the total heat obtained from the combustion of a specified fuel at 60 F.
Required: No
Units: kJ/kg (SI), Btu/lb (US), kCal/kg (MKH)
Default: None
Ultimate Analysis by Mass %
Specify the mass percent of each component (e.g. carbon, ash) in a liquid or solid fuel. For a fuel oil, you
must specify either the fuel ultimate analysis or one of the items listed in the Special Properties section.
For a generic liquid or solid fuel, you must specify the ultimate analysis.
Required: No
Units: Mass percent
Default: None
Note
You can specify values that do not sum to 100 percent and use the Normalize button to force the
entered values to add up to 100 percent.
Normalize
Click to normalize the entered composition to 100 percent. This allows the composition to be entered in
absolute amounts and then normalized to percentage values.
API - Degree API
Specify degree API of the fuel oil. This is one of the items in the Special Properties option that is used to
characterize a fuel oil. You must specify either the Ultimate Analysis for the fuel oil or one of the items in
the Special Properties option. You can (and should) specify more than one of the Special Property items
if they are known.
Required: No
Units: degree API
Default: None
Note
The program inserts missing ultimate analysis components and heating values from a data set based
on the API Technical Data Book for 0.7 specific gravity 1.3 (0.0001 degrees API 35).
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GR - Grade
Specify fuel oil grade. This is one of the items in the Special Properties option that is used to characterize
a fuel oil. You must specify either the Ultimate Analysis for the fuel oil or one of the items in the Special
Properties option. You can (and should) specify more than one of the Special Property items if they are
known.
Required: No
Units: None
Default: None
Note
The program inserts missing ultimate analysis components and heating values from a data set based
on the API Technical Data Book for 0.7 specific gravity 1.3 (0.0001 degrees API 35).
SG - Specific gravity
Specify specific gravity of a solid or liquid fuel. When specifying a fuel oil, you use this item in the Special
Properties option to characterize a fuel oil. You must specify either the Ultimate Analysis for the fuel oil or
one of the items in the Special Properties option. You can (and should) specify more than one of the
Special Property items if they are known. For a generic solid or liquid fuel, you must specify the Ultimate
Analysis, and the specific gravity is optional.
Required: No
Units: None
Default: None
Note
For a fuel oil, the software inserts missing ultimate analysis components and heating values from a
data set based on the API Technical Data Book for 0.7 specific gravity 1.3 (0.0001 degrees API
35).
Typical Values for Medium Grade No. 6 Fuel Oil
Grade 6.5
API 11.4
Specific gravity 0.990
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Oxidant Air Panel
This panel is used to specify the flow rate, properties, and composition for air when used as an oxidant
stream for a burner. This panel is used whenever Preheat air or Ambient air is selected as an oxidant
stream on the System Fuels panel.
Oxidant flow
Specifies the units in which the oxidant flow rate will be specified. Choose Mass, Volume, Mole, or Duty.
Required: Yes
Units: None
Default: Mass
Note
When a value for this field is selected, the units for the Oxidant Flow Rate field will change
accordingly.
Oxidant flow rate
Specify the flow rate of the oxidant stream. The units of this property will depend upon the selection made
for the Oxidant Flow Units field.
Required: Yes
Units: SI US MKH
Mass kg/hr lb/hr kg/hr
Volume m³/hr ft³/hr m³/hr
Mole kg-mol/hr lb-mol/hr kg-mol/hr
Duty Megawatts MM BTU/hr MM Kcal/hr
Default: None
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Oxidant flow units
Specify the units in which the fuel flow rate will be specified. Choose Mass, Volume, Mole, or Duty.
Required: Yes
Units: None
Default: Mass
Note
When a value for this field is selected, the units for the Oxidant Flow Rate field will change
accordingly. The Duty specification will burn the amount of fuel needed to produce the specified duty.
Excess oxidant
Specify the amount of excess oxidant (beyond what is necessary to burn the fuel). This is an alternate
means of specifying the oxidant flow rate. The amount of excess oxidant may be specified in five ways.
% Excess air
Mole % O2 in dry flue gas
Mole % O2 in wet flue gas
Wet air/fuel gas
Standard volume wet air/Standard volume fuel gas
Wet air/fuel
Standard volume wet air/Mass fuel
Required: No
Units: SI US MKH
%Excess % % %
%O2 in Dry % % %
%O2 in Wet % % %
Vol. air/Vol. fuel m³/m³ ft³/ft³ m³/m³
Vol. air/Mass fuel m³/kg ft³/lb m³/kg
Default: 0.0
Incomplete Combustion
You may select to specify an incomplete combustion process. The amount of incomplete combustion is
specified as a ratio between the mole percent of carbon monoxide and carbon in the burned flue gas.
Required: No
Units: % CO/C (SI), % CO/C (US), % CO/C (MKH)
Default: 0.0 (Complete combustion)
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Oxidant pressure
Specify the pressure of the oxidant stream used in the combustion process.
Required: No
Units: kPa (SI), psig (US), kg/cm²G (MKH)
Default: 0.0
Oxidant temperature
Specify the temperature of the oxidant stream used in the combustion process.
Required: No
Units: C (SI), F (US), C (MKH)
Default: 80 F (26.7 C)
Oxidant moisture
Specify the amount of water present in the oxidant stream. The amount of water may be specified in four
ways:
%RH Percent relative humidity
LWLD Mass water/Mass dry air
SWLD Standard volume water/Mass dry air
SWSD Standard volume water/Standard volume air
Required: No
Units: SI US MKH
%RH % % %
LWLD kg/kg lb/lb kg/kg
SWLD m³/kg ft³/lb m³/kg
SWSD m³/m³ ft³/ft³ m³/m³
Default: 0.0
Note
This field is present only when air is used as an oxidant. If the air temperature is above 65.56 °C (150
°F), Xfh assumes that the air is preheated. Xfh calculates water content based on a relative humidity
specification at a temperature of 15.56 °C (60 °F). If this assumption is invalid for your case, use one
of the other water content specification options.
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Oxidant Gas Panel
This panel is used to specify the flow rate, properties, and composition for a user-defined gas stream
when used as an oxidant stream for a burner. This panel is used whenever Gas is selected as an oxidant
stream on the System Fuels panel.
Oxidant composition units
Specify the units to be used in specifying the oxidant gas composition. The choices are Volume or
Weight.
Required: Yes
Units: None
Default: Volume
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Oxidant composition
Specify the composition of the oxidant stream used for a combustion process. Enter the amount of each
component in these fields. You may select up to 10 of the listed components to define your oxidant
composition.
Required: Yes
Units: Volume % or mole %, depending upon choice of composition units
Default: None
Note
You may enter values that do not sum up to 100% and use the Normalize button to force the
compositions to add up to 100.
Add
Click this button to add a selected gas component to the list of components in the gas mixture.
Delete
Click this button for a dialog box in which you can select gas components to remove from the gas mixture.
Order...
Click this button for a dialog box in which you can reorder the components in the gas or fuel gas mixture.
Normalize
Click to normalize the entered composition to 100 percent. This allows the composition to be entered in
absolute amounts and then normalized to percentage values.
Diluent Panel
This panel describes the flow rate and properties of steam when used as a diluent for a combustion
calculation.
Diluent pressure
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Specify the pressure of the diluent stream used in the combustion process.
Required: Yes
Units: kPa (SI), psig (US), kg/cm²G (MKH)
Default: None
Note
You must specify either the diluent pressure or the diluent temperature.
Diluent temperature
Specify the temperature of the diluent stream used in the combustion process.
Required: Yes
Units: C (SI), F (US), C (MKH)
Default: None
Note
You must specify either the diluent pressure or the diluent temperature.
Diluent flow units
Specify the units in which the diluent flow rate will be specified. Choose Mass, Volume, Mole, Duty, or
Wt/Wt.
Required: Yes
Units: None
Default: Mass
Note
When a value for this field is selected, the units for the Diluent Flow Rate field change accordingly.
Diluent flow rate
Specifies the flow rate of the diluent stream. The units of this property will depend upon the selection
made for the Diluent Flow Units field.
Required: Yes
Units: SI US MKH
Mass kg/hr lb/hr kg/hr
Volume m³/hr ft³/hr m³/hr
Mole kg-mol/hr lb-mol/hr kg-mol/hr
Duty Megawatts MM BTU/hr MM Kcal/hr
Wt/Wt kg/kg lb/lb kg/kg Mass steam/Mass fuel
Default: None
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Diluent weight fraction liquid
Specify the weight fraction liquid of the water used as a diluent stream.
Required: No
Units: Weight fraction liquid
Default: 0.0
Note
Value must be between 0.0 (Saturated or superheated steam) and 1.0 (Saturated or subcooled liquid)
Gas Panel
This panel describes the flow rate, properties, and compositions of a gas stream used in a combustion
calculation.
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Fuel composition units
Specify the units to be used in specifying the fuel gas composition. The choices are Volume or Weight.
Required: Yes
Units: None
Default: Volume
Fuel composition
Specify the composition of the fuel gas stream used for a combustion process. Enter the amount of each
component in these fields. You may select up to 10 of the listed components to define your fuel
composition.
Required: Yes
Units: Volume % or Mole % depending upon choice of composition units
Default: None
Note
You may enter values that do not sum up to 100% and use the Normalize button to force the
compositions to add up to 100.
Normalize
Click to normalize the entered composition to 100 percent. This allows the composition to be entered in
absolute amounts and then normalized to percentage values.
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Liquid/Solid Panel
This panel describes the flow rate, properties, and compositions of a liquid or solid fuel used in a
combustion calculation.
Pressure
Specify the pressure of the fuel stream used in the combustion process.
Required: No
Units: kPa (SI), psia (US), kgf/cm² (MKH)
Default: 0.0
Temperature
Specify the temperature of the fuel stream used in the combustion process.
Required: No
Units: °C (SI), °F (US), °C (MKH)
Default: 80 °F (26.67 °C)
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Flow
Specify the flow rate of the fuel stream. The units of this property will depend upon the selection made for
the Fuel Flow Units field.
Required: Yes
Units: SI US MKH
Mass kg/hr lb/hr kg/hr
Volume m³/hr ft³/hr m³/hr
Mole kg-mol/hr lb-mol/hr kg-mol/hr
Duty Megawatts MM BTU/hr MM Kcal/hr
Default: None
Lower heating value
Specify the higher heating value minus the latent heat of vaporization of the water formed by combustion
of hydrogen in the fuel. It is sometimes called the net or useful heating value. For fired heaters, use lower
values.
Required: No
Units: kJ/kg (SI), Btu/lb (US), kCal/kg (MKH)
Default: None
Higher heating value
Specify the total heat obtained from the combustion of a specified fuel at 60 °F.
Required: No
Units: kJ/kg (SI), Btu/lb (US), kCal/kg (MKH)
Default: None
Characterization factor
This is an optional input item. However, the Watson Characterization factor for the fuel oil should be
specified; otherwise, the program computes this value. Based on degree API and Watson
characterization factor, the program computes the average and the ASTM 50% boiling points, the
molecular weight, and the thermal conductivity of the fuel oil.
Required: No
Units: None
Default: Program calculated
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Ultimate Analysis by Mass %
Specify the mass percent of each component (e.g. carbon, ash) in a liquid or solid fuel. For a fuel oil, you
must specify either the fuel ultimate analysis or one of the items listed in the Special Properties section.
For a generic liquid or solid fuel, you must specify the ultimate analysis.
Required: No
Units: Mass percent
Default: None
Note
You can specify values that do not sum to 100 percent and use the Normalize button to force the
entered values to add up to 100 percent.
Normalize
Click to normalize the entered composition to 100 percent. This allows the composition to be entered in
absolute amounts and then normalized to percentage values.
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Convection Module
The convection module performs local heat transfer and pressure drop calculations for the convection
section of a fired heater. The calculations are performed incrementally down the flow length of each tube
on a row-by-row basis. The heat transfer and pressure drop calculations use the latest HTRI proprietary
methods.
You provide the geometric specification of the convection bundle geometry as well as the process
conditions and physical properties of the process fluids. Specify the flue gas composition directly for a
standalone convection calculation, or include a radiant firebox calculation, and Xfh calculates it.
The process side calculations can accommodate both single-phase and boiling fluids. On the flue-gas
side, the calculations include both convective and gray gas radiation components. For cylindrical heaters,
you can also include the effect of direct firebox radiation on the shock tubes.
Additionally, the convection section can perform stack draft calculations. By defining a stack from pre-
defined stack duct elements (e.g., damper), Xfh can calculate the pressure profile through the stack.
The convection module contains the following panels:
Stack Panel
Stack Element Panels
Bundle Panel
Bundle Layout Panel
Process Conditions Panel
Tube Type Panel
See the section Box Heater Module for general information about these panels.
Distance from heater roof to center of first tuberow
Specify the vertical distance between the inside roof of the radiant section and the centerline of the first
row of convection tubes.
Required: No
Units: m (SI), ft (US), mm (MKH)
Default: 0.0
Note
This field is used to calculate the amount of radiant energy that leaves the firebox and transfers to the
convection section shock tubes. A value of zero (0.0) for this field bypasses the shock tube radiation
calculation.
The method has been implemented only for cylindrical heaters, and the field is active only for
cylindrical heaters with a convection section. The method does not handle annular roof openings.
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Left wall clearance
Define the clearance between the tube wall and the inside of the left refractory wall for the first tuberow in
the current tube section.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
For a staggered layout, this field specifies the closest distance between the tube wall and the
refractory wall. Alternate rows have a larger clearance.
Transverse pitch
Define the center-to-center spacing between tubes in a row across the convection section bundle.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
For a staggered layout, this field specifies the closest distance between the tube wall and the
refractory wall. Alternate rows have a larger clearance.
Longitudinal pitch
Define the center-to-center spacing between rows of tubes in the direction of flue gas flow.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
For a staggered layout, this field specifies the closest distance between the tube wall and the
refractory wall. Alternate rows have a larger clearance.
Tube outside diameter
Specify the outside diameter of a tube in the convection section. For finned tubes, this value is the plain
end diameter.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
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Tube wall thickness
Define the average wall thickness of a tube in the convection section.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Tube type
Defines the type of tubes present in the convection section. Create additional tube types as needed to
define the convection bundle. The choices are
Plain
High-Fin
Low-Fin
Stud-Fin
Required: Yes
Units: None
Default: Plain
Note
If you select High-Fin, Low-Fin, or Stud-Fin for any tube sections, you may define the extended
surface geometry in subsequent data panels
Tube material code
Define the tube material for tubes in the current convection section. Choose from any material in the drop-
down list.
Required: Yes
Units: None
Default: MES-CS (Medium carbon steel)
Note
If you select a material, you do not have to provide the tube thermal conductivity. If you select
OTHER, then you must specify tube thermal conductivity.
Tube thermal conductivity
Specify the thermal conductivity of the tube material.
Required: No
Units: W/m °C (SI), Btu/hr ft °F (US), kcal/hr m °C (MKH)
Default: None
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Note
If specified, the value should be at the average tube metal temperature. This field is required if you
select OTHER in the Tube Metallurgy field.
Heated tube length
Specify the length per row of heated tube surface. Typically, this value would equal the distance between
refractory walls.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Unheated length/row
Specify the unheated length per row of tubes. Typically, this value equals the distance inside the
convection section walls.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
This distance is used to calculate the proper process tubeside pressure drop.
Unheated length between rows
Specify the extra length of piping used to connect the process tuberows in the convection section.
Required: Yes
Units: m (SI), ft (US), mm (MKH)
Default: None
Note
This distance is used to calculate the proper process tubeside pressure drop.
Tube emissivity
Define the emissivity of tubes in the convection section.
Required: No
Units: None
Default: Emissivity of tubes in radiant section
Note
This field is used to calculate the radiant heat transfer between the radiant section and the shock
tubes in the convection section.
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Fins Panels
Use items on these panels to define high-finned, low-finned, or stud-finned tube geometry. One of these
panels is enabled when you select High fin, Low fin, or Stud fin for Type on the Tubes panel.
Below is the panel for high-fin tube geometry. Click any item below to learn more about it.
More Information on Fins Panels
One of these panels is enabled only when you select high-finned, low-finned, or stud-finned tube type on
the Tubes panel.
For low-finned or high-finned tubes, select a tube from the internal databank OR enter tube geometry
directly
For stud-finned tubes, define the tube geometry directly
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To use Xfh's internal databank:
1 Click Load from Databank. A dialog box appears.
2 Select fin geometry from the drop-down list.
3 Select tube dimensions from the drop-down list.
Note
When you select fin geometry in Databank type, you must also select an available tube size from
Tube dimensions list.
After you select a databank type, the Tube dimensions list displays tube sizes for which that fin
geometry is available.
Xfh automatically enters all geometry fields on the panel when you select from Tube dimensions
list. You can override individual geometry fields as necessary.
Select Not in Databank if you do not find fin geometry or tube dimension you want, and then
manually enter fin geometry values in geometry fields on Fins panel.
Click here to see tables of finned tube geometry dimensions.
To specify low-finned geometry:
Enter values for
Fins/unit length
Fin root diameter
Fin height
Fin thickness
Outside area/length
Wall thickness under fins
Fins per Unit Length
The value you select for this field can have a significant effect on your exchanger’s performance. Xfh
checks for condensate retention in fin valleys because this condition can negate the enhancement
provided by additional surface area.
If you receive a retention warning message, adjust fin geometry.
Decreasing fin density reduces amount of condensate retention.
Increasing fin density can also help, if increased surface area on upper tube surface overcomes
condensate retention on bottom surface of tube.
HTRI research indicates that for single-phase shellside laminar flow, 433 fins/m (11 fins/in.) can be
effective.
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Load from Databank
When you click Load from Databank, the following dialog box appears:
1. Select fin geometry from the drop-down list.
2. Select tube dimensions from the drop-down list.
After you select fin geometry and tube dimensions, Xfh automatically enters values into fin geometry
fields from an internal databank. You can override individual geometry fields as necessary.
Databank type
Sets fin density and height for low-finned tubes from Xfh's internal databank, which contains actual fin
dimensions from various tube manufacturers.
Select a databank type and tube dimensions. You can override any values that Xfh inserts as a result
of your selection.
OR
Enter all fin geometry values.
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Required: No
Units: None
Default: None
Note
Not all tube types are available in all tube materials. If you do not find the fin geometry you want,
manually enter fin geometry values.
Tube dimensions
Sets tube dimensions for low-finned tubes.
After you select from the Databank type list, choose a set of tube OD, plain end wall thickness, and fin
root diameter dimensions from the drop-down list for that fin geometry.
Required: If Databank type is selected
Units: None
Default: None
Note
If you do not find the fin geometry or tube dimensions you want, manually enter fin geometry values.
Fins/length
Defines number of fins per unit length.
Required: For low-finned tubes
Units: fins/m (SI), fins/in. (US), fins/m (MKH)
Default: None
Note
If you select a Databank type and Tube dimensions, Xfh automatically supplies a value for this field.
Fin root diameter
Sets diameter of fin root, sum of Tube inside diameter and Wall thickness under fins.
Required: For low-finned tubes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
If you select a Databank type and Tube dimension, Xfh automatically supplies a value for this field.
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Fin height
Sets height of fin, measured from Fin root diameter to Overfin diameter.
Required: For low-finned tubes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
If you select a Databank type and Tube dimension, Xfh automatically supplies a value for this field.
Fin thickness
Sets average thickness of fins.
Required: For low-finned tubes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
If you select a Databank type and Tube dimension, Xfh automatically supplies a value for this field.
Outside area/length
Sets total outside finned surface area per unit length of tube.
Required: For low-finned tubes
Units: m²/m (SI), ft²/ft (US), m²/m (MKH)
Default: None
Note
If you select a Databank type and Tube dimension, Xfh automatically supplies a value for this field.
Wall thickness under fins
Sets the wall thickness of the tube under the finned section.
Required: For low-finned tubes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
If you select a Databank type and Tube dimension, Xfh automatically supplies a value for this field.
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Fin material
Specifies material from which the fin is made. Select from a list of built-in materials.
Required: No
Units: None
Default: Aluminum 1100
Note
Xfh supplies properties as a function of temperature for each built-in material and calculates properties
at average hot and cold inlet temperatures.
Setting loss
Specify a heat duty loss in the convection section to allow specification to losses to the ambient. The loss
is specified as a percentage of the process duty.
Required: Yes
Units: Percent
Default: 2%
Process Conditions Panel
This panel is used to set process conditions and physical properties for the convection section process
fluids and the flue gas if a standalone convection section is being simulated. This panel contains one
column for each process fluid in the convection bundle.
When running a standalone convection section (flue gas must be specified)
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When running a convection section with a radiant firebox (no need to specify flue gas)
Flow rate
Specifies the flow rate of a process fluid in the convection bundle.
Required: Yes
Units: kg/sec (SI), lb/hr (US), kg/hr (MKH)
Default: None
Phase condition
Specifies the phase condition of the process fluid in the radiant and convection sections. The choices are
All vapor
All liquid
Boiling
Required: Yes
Units: None
Default: Boiling
Note
If you specify All vapor or All liquid, the program automatically sets the corresponding weight fraction
vapor entries.
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Inlet temperature
Specifies the temperature of a process fluid entering the convection bundle.
Required: Yes (or specify outlet temperature)
Units: °C (SI), °F (US), °C (MKH)
Default: None
Note
You must specify either the inlet or outlet temperature of each process fluid in the convection section.
You may also specify both temperatures.
Outlet temperature
Specifies the temperature of a process fluid leaving the convection bundle.
Required: Yes (or specify inlet temperature)
Units: °C (SI), °F (US), °C (MKH)
Default: None
Note
You must specify either the inlet or outlet temperature of each process fluid in the convection section.
You may also specify both temperatures.
Inlet fraction vapor
Specifies the weight fraction vapor of a process fluid entering the convection section.
Required: Yes (see note below)
Units: weight fraction vapor (SI), weight fraction vapor (US), weight fraction vapor (MKH)
Default: None
Note
For two-phase fluids, the weight fraction vapor is an alternate specification to the corresponding
temperature. For example, you can specify either the inlet temperature or the inlet weight fraction
vapor. The program calculates the missing entry based on the fluid property information. If you specify
both values, the program respects the temperature value and recalculates the weight fraction vapor if
necessary.
Outlet fraction vapor
Specifies the weight fraction vapor of a process fluid leaving the convection section.
Required: Yes (see note below)
Units: weight fraction vapor (SI), weight fraction vapor (US), weight fraction vapor (MKH)
Default: None
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Note
For two-phase fluids, the weight fraction vapor is an alternate specification to the corresponding
temperature. For example, you can specify either the inlet temperature or the inlet weight fraction
vapor. The program calculates the missing entry based on the fluid property information. If you specify
both values, the program respects the temperature value and recalculates the weight fraction vapor if
necessary.
Process duty
Specifies the process duty of a single process fluid in the convection section.
Required: No
Units: megawatts (SI), MM Btu/hr (US), MM kcal/hr (MKH)
Default: None
Note
The program uses the process duty (if specified) to calculate any missing process conditions.
Inlet pressure
Specifies the entering pressure of a process fluid in the convection section.
Required: Yes
Units: kPa (SI), psia (US), kmf/cm² (MKH)
Default: None
Allowable pressure drop
Specifies the allowable pressure drop for a process fluid in the convection section.
Required: No
Units: kPa (SI), psi (US), mf/cm² (MKH)
Default: 0.0
Note
Although not currently used in the calculations, this value is reported on the output.
Process fouling layer thickness
Sets fouling layer thickness for the process fluids. Any value that you enter must be greater than or equal
to zero.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: 0.0
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Note
Fouling layer thickness decreases available flow area, which usually increases pressure drop. Errors
in calculated pressure drop can result if you enter a large fouling resistance but omit fouling layer
thickness.
Process fouling factor
Specifies the fouling resistance on the tubeside for a process fluid in the convection section.
Required: No
Units: m² K/W (SI), ft² hr °F/Btu (US), m² hr °C/kcal (MKH)
Default: 0.0
Flue gas fouling factor
Specifies the fouling resistance on the flue gas side for a process fluid in the convection section.
Required: No
Units: m² K/W (SI), ft² hr °F/Btu (US), m² hr °C/kcal (MKH)
Default: 0.0
Note
Xfh allows you to specify a flue gas fouling factor on a process fluid basis rather than across the entire
convection section.
Stream name
Identifies the column of process conditions.
Required: Yes
Units: degrees (SI), degrees (US), degrees (MKH)
Default: n/a
Estimated inlet fraction vapor
Specifies an initial guess of the inlet fraction vapor.
Required: No
Units: None
Default: None
Note
A good guess may speed the convergence of the case.
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Estimated inlet temperature
Specify an initial guess of the inlet fraction temperature.
Required: No
Units: °C (SI), °F (US), °C (MKH)
Default: None
Note
A good guess may speed the convergence of the case.
Estimated inlet pressure
Specify an initial guess of the inlet pressure.
Required: No
Units: kPa (SI), psia (US), kgf/cm² (MKH)
Default: None
Note
A good guess may speed the convergence of the case.
Convection Section Process Specifications
In general, you should specify the process flow rate and either the inlet or outlet temperature for a
convection section process fluid. The duty and other process temperatures should remain unspecified.
Using the specifications, each section of convection tubes containing a process fluid will be run in
simulation (unknown duty) mode. The program predicts the missing process specifications and the
estimated duty based on the calculated process and flue gas heat transfer coefficients.
You can specify the duty of a process fluid by entering the flow rate and both process temperatures, or a
single temperature and the process duty. In this case, the program respects the entered duty and reports
an overdesign for the section containing this process fluid. Multiple process fluids may result in different
overdesigns in different portions of the convection section, making output interpretation more difficult.
Unset Bank Fin
Clears the Bank fin code field.
Each high-finned type in the databank file has a range of valid geometry parameters. You can set specific
high fin parameters outside prescribed limits in the databank by using the dialog box accessible from the
Load from Databank button.
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Bank fin code
Sets fin geometric input for high-finned tubes from the internal databank, which contains actual fin
dimensions from various tube manufacturers.
Select a databank type and tube dimensions.
OR
Enter all fin geometry values. You can override any values that the program inserts as a result of your
fin selection.
Required: No
Units: None
Default: None
Note
High Accuracy Automatic High-Finned Tube Geometry: If you enter an Automatic Tube Code for a
high-finned tube, Xfh supplies specific correlations based on HTRI research data.
Fin type
Sets relevant parameters that you can enter for a given fin type. Entries on panel are activated according
to type of high fin you select here.
Circular fin
Serrated fin
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Rectangular and plate (continuous) fin
Rectangular L-Foot Rectangular I-Foot
Continuous (Plate–fin) Sections
Required: Yes
Units: None
Default: Circular
Note
Not all tube types are available in all tube materials. If you do not find fin geometry you want, manually
enter fin geometry values.
Fin density
Defines number of fins per unit length. The value you select for this field can have a significant effect on
your exchanger’s performance.
Required: Yes
Units: fins/m (SI), fins/in. (US), fins/m (MKH)
Default: None
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Note
If you select Auto code, Xfh automatically supplies values for this field.
Over fin diameter
Specifies over-fin diameter.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
Use this field for circular and segmented fins only.
Thermal conductivity
Specifies thermal conductivity of fin material. Use this field when your tube material is not in Xfh’s Fin
Material Databank.
Required: No
Units: W/m °C (SI), Btu/hr ft °F (US), kcal/hr m °C (MKH)
Default: Xfh uses Fin Material Code in its thermal conductivity calculations and provides default
value unless you select Not in Databank.
Fin bond resistance
Specifies fin bond resistance. If you do not enter a value, Xfh assumes no bond resistance.
Integral finned tubes
These tubes have zero bond resistance.
Imbedded finned tubes
These tubes have zero bond resistance.
Tension-wound tubes
At elevated temperatures (typically above 176 °C (350 °F)), fin can separate from tube, resulting in
marked decrease in heat transfer.
Bimetallic tubes
Any value you enter for fin bond resistance can be considered to be resistance between tube and
sleeve. New bimetallic tubes have no bond resistance.
Xfh adds entered value directly as resistance in overall heat transfer coefficient calculations. It is not
added to calculated outside heat transfer coefficient and is not corrected for area ratio. Therefore, the
value you enter must be based on extended surface area of tube and not actual bond area.
Required: No
Units: m² K/W (SI), ft² hr °F/Btu (US), m² hr °C/kcal (MKH)
Default: None
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Note
Rate continuous fin (plate-fin) units by specifying rectangular finned tubes with zero fin-tip clearance.
Fin efficiency
Specifies fin efficiency. Usually you should not enter a value because Xfh calculates it. However, if you
input j-curves on f- and j-Curves panel and have already included efficiency in given j-factors, enter an
efficiency of 100%.
Required: No
Units: percent
Default: None
Note
Do not enter efficiency values as a fraction.
Split segment height
Specifies cut segment height.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
Enter 0 (zero) for non-serrated tubes.
Split segment width
Specifies split segment width.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
Enter 0 (zero) for non-serrated tubes.
Length
Specifies length perpendicular to direction of airflow.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
Rate continuous fin (plate-fin) units by specifying rectangular finned tubes with zero fin-tip clearance.
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Width
Specifies length in direction of airflow.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
Rate continuous fin (plate-fin) units by specifying rectangular finned tubes with zero fin-tip clearance.
Fin base thickness
Specifies fin base thickness. If fins have uniform thickness or if you know only average thickness, enter
that value.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: None
Fin tip thickness
Specifies fin tip thickness. If fins have uniform thickness or if you know only average thickness, enter that
value.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: None
Effects of Fin Thickness and Height
Economics and heat transfer usually dictate that the fin be as thin as possible. Fin efficiency is not
affected by the usual limits of fin thicknesses, as chosen by the limits of finning machines used by air-
cooled exchanger manufacturers. Tubes with 25.4-mm(1-in.) OD and 15.9-mm (5/8-in.) or 12.7-mm (1/2-
in.) high fins are current standards. The minimum fin thickness is based on stock strip 0.42 mm (0.016 in.)
and 0.30 mm (0.012 in.) thick. After finning, tubes with a base thickness of 0.42 mm (0.016 in.) and 0.30
mm (0.012 in.) have a fin tip thickness of 0.20 mm (0.008 in.) and 0.15 mm (0.006 in.), usually 1/2 the
base strip thickness. Some machines can maintain thickness for the full height of the fin, but because this
thickness has little effect on the overall heat transfer, the obvious choice is the thinner materials because
of their lower cost.
Because of work hardening, stainless and carbon steel must be thicker than aluminum or copper to keep
the ribbon from breaking during finning. Reducing fin height makes finning easier (and may be required
on some machines), and tends to increase fin efficiency because of lower conductivities of these
materials. Other advantages/disadvantages of materials used for fins follow.
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Material Advantages Disadvantages
stainless steel Expensive
Difficult to fin
Not sufficiently conductive
carbon steel In some applications, such as
caustic atmospheres, more
corrosion-resistant than other
materials
Can be useful because it now
can be handled economically
Can be galvanized
aluminum
copper
Increasing fin thickness improves efficiency up to a point. The standard fin analysis assumes one-
dimensional heat flow. Two-dimensional heat flow (across the thickness as well as the height) comes into
effect (to the detriment of the fin efficiency) when the fin height to fin thickness ratio is smaller than a
value of about eight. Xace assumes one-dimensional heat flow, so use caution if the fin height to
thickness ratio is less than eight.
Fin height is limited not only by the effect of increasing fin height on fin efficiency, but also by the limits of
machines used to fabricate fins.
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Cylindrical Module
The cylindrical module models the radiant- and process-side performance of a vertical cylindrical heater.
On the radiant side, Xfh performs
tube flux calculations at ten increments along the length of the tube coil
gas temperature calculations in a two-dimensional 5 x 10 grid within the cylindrical heater
process heat transfer and pressure drop calculations along the full path length of the process fluid
You provide the geometry of the heater enclosure and the tube coil, the process conditions and physical
properties of the process fluid, and the process conditions and composition of the combustion fuels.
The process-side calculations can accommodate both single-phase and boiling fluids.
The cylindrical module contains the following panels:
Cylindrical Heater Panel
Configuration Panel
Emissivities Panel
Flue Gas Circulation Panel
Insulation Loss Coefficient Panel
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Cylindrical Heater Panel
This panel, used to specify the overall geometry of a cylindrical heater, appears when you select the
Cylindrical module icon.
Select any field on the figure below to learn more about it.
Outside diameter
Specifies the outer diameter of the firebox for a cylindrical heater.
Required: Yes
Units: m (SI), ft (US), m (MKH)
Default: None
Note
The software calculates the inside diameter by subtracting twice the wall thickness. If you do not
specify a wall thickness, use this field to specify the inside diameter of the firebox.
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Wall thickness
Specifies the wall thickness of the firebox for a cylindrical heater.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
This field is used to calculate the inside diameter from the specified outside diameter. If you do not
specify a value for this field, specify the inside diameter in the Outside Diameter field.
Roof thickness
Specifies the roof thickness of the firebox for a cylindrical heater.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
This field is used to calculate the inside height based on the specified cylinder height. If you do not
specify a value for the roof and floor thickness, specify the inside height in the Height field.
Height
Specifies the distance from the top plate to the bottom plate for a cylindrical heater. This dimension
includes the thickness of the top and bottom plate.
Required: Yes
Units: m (SI), ft (US), m (MKH)
Default: None
Note
The inside height is calculated by subtracting the roof and floor thickness from this value. If you do not
specify a value for the roof and floor thickness, specify the inside height in this field.
Floor thickness
Specifies the thickness of the bottom plate of the firebox for a cylindrical heater.
Required: No
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
This field is used to calculate the inside height based on the specified cylinder height. If you do not
specify a value for the roof and floor thickness, specify the inside height in the Height field.
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Type of roof opening
Specifies the shape of the roof opening at the top of the firebox for a cylindrical heater. The choices are
Center rectangular
Center circular
Annular circles
Required: Yes
Units: None
Default: Center rectangular
Roof opening length
Specifies the length of the firebox roof opening for a cylindrical heater.
Required: No
Units: m (SI), ft (US), m (MKH)
Default: None
Note
This field appears only if you select Center rectangular for the type of roof opening.
Roof opening width
Specifies the width of the firebox roof opening for a cylindrical heater.
Required: No
Units: m (SI), ft (US), m (MKH)
Default: None
Note
This field appears only if you select Center rectangular for the type of roof opening.
Roof opening diameter
Specifies the diameter of the firebox roof opening for a cylindrical heater.
Required: No
Units: m (SI), ft (US), m (MKH)
Default: None
Note
This field appears only if you select Center circular for the type of roof opening.
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Roof opening inside diameter
Specifies the diameter of the inner annulus of the firebox roof opening for a cylindrical heater.
Required: No
Units: m (SI), ft (US), m (MKH)
Default: None
Note
This field appears only if you select Annular circular for the type of roof opening.
Roof opening outside diameter
Specifies the diameter of the outer annulus of the firebox roof opening for a cylindrical heater.
Required: No
Units: m (SI), ft (US), m (MKH)
Default: None
Note
This field appears only if you select Annular circular for the type of roof opening.
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Configuration Panel
This panel is used to specify the number, dimensions, and location of the burners for a cylindrical heater.
The program assumes that multiple burners are arranged in an equally spaced circle centered in the
bottom of the heater.
Select any of the fields on the figure below to learn more about it
Tube circle diameter
Specifies the diameter of the circle of process tubes in a cylindrical heater.
Required: Yes
Units: m (SI), ft (US), m (MKH)
Default: 5.49 m (18 ft)
Note
This value is measured from tube center to tube center.
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Number of parallel passes
Specifies the number of parallel process flow paths in the firebox of a cylindrical heater. For example, if
this value is set to 4, the process fluid enters four tubes in the firebox and traverses four identical flow
paths.
Required: Yes
Units: None
Default: 4
Process outlet location
Specifies whether the process fluid leaves the firebox at the top or the bottom.
Required: Yes
Units: None
Default: Bottom
Burner circle diameter
Specifies the diameter of a circle in the bottom of a cylindrical heater that identifies the location of the
burners. For cylindrical heaters, multiple burners are assumed to be arranged in a circular pattern
centered in the bottom of the firebox.
Required: Yes
Units: m (SI), ft (US), m (MKH)
Default: 2.59 m (8.50 ft)
Note
For a single burner, specify 0.0 for this field.
Number of burners
Specifies the number of burners present in a cylindrical heater.
Required: Yes
Units: None
Default: 8
Note
If a single burner is entered, the program assumes it to be in the center of the firebox, and the burner
circle diameter entry is ignored.
Burner nozzle diameter
Specifies the diameter of a burner nozzle for a cylindrical heater.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: 609.6 mm (24.0 in.)
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Note
Instead of specifying the burner nozzle diameter, you may enter the burner flue gas velocity. To
activate the burner flue gas velocity field, remove the entry from the burner nozzle diameter field.
Burner flue gas velocity
Specifies the velocity of the flue gas from a burner in a cylindrical heater.
Required: Yes
Units: m/sec (SI), ft/sec (US), m/sec (MKH)
Default: None
Note
Instead of specifying the burner flue gas velocity, you may enter the burner nozzle diameter. To
activate the burner nozzle diameter field, remove the entry from the burner flue gas velocity field.
Location of burner center from X-axis
Specifies the location of the first burner in a circle of burners present in a cylindrical heater. The location
is specified as the number of degrees counterclockwise from the X-axis.
Required: Yes
Units: degrees (SI), degrees (US), degrees (MKH)
Default: 22.5 degrees
Note
This field is not used if a single burner is specified.
Flame length
Specifies the length of the burner flame for a cylindrical heater. Enter the value as either a constant or a
function of the heat released. To specify the flame length, enter a value for A and B in this equation:
BA ReleaseHeatLengthFlame
Required: Yes
Units: SI US MKH
A m ft m
B None None None
Default: A = 5.49 m (18 ft)
B = 0.0
Note
To enter a constant flame length, specify the flame length in field A and enter 0.0 for B.
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Half jet angle from vertical
Specifies the shape of the burner flame for a cylindrical heater.
Required: Yes
Units: degrees (SI), degrees (US), degrees (MKH)
Default: 20 degrees
Note
The units for this field are relative to vertical.
Tube Geometry Panel
This panel allows you to set tube geometry by section for cylindrical heaters.
Number of different tube sizes and/or C-C spacing per pass
Specifies the number of tube outside diameter and/or center-to-center spacing in a single parallel flow
path. The minimum value is 1, and the maximum value is 5.
Required: Yes
Units: n/a
Default: 1
Note
As you change this value, the rows on the Outlet Set table change accordingly.
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Outside diameter
Specifies the outside diameter of the tubes in the process coil for a cylindrical heater. You can specify this
value for up to 5 different sets in a single parallel flow path.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
You can alternattely specify the tube nominal outside diameter by using the OD (N) field. If the
nominal diameter is selected, the program automatically enters the appropriate value for this field.
Nominal outside diameter
Specifies the nominal outside diameter of the tubes in the process coil for a cylindrical heater. The
nominal diameter is the average of the inside and outside diameters of the tube. You can specify this
value for up to 5 different sets in a single parallel flow path.
Choices
*** – No nominal diameter
selected
N2 – Nominal 2 in.
N3 – Nominal 3 in.
N4 – Nominal 4 in.
N5 – Nominal 5 in.
N6 – Nominal 6 in.
N8 – Nominal 8 in.
N10 – Nominal 10 in.
N12 – Nominal 12 in.
Required: No
Units: n/a
Default: ***
Note
When you select a value for this field, the actual diameter is automatically entered in the Outside
diameter field. The nominal value is always specified in inches, but the actual diameter is converted to
the current unit set.
Wall thickness
Specifies the average tube wall thickness for tubes in the process coil of a cylindrical heater. You can
specify this value for up to 5 different sets in a single parallel flow path.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
You can alternately specify a schedule tube wall thickness using the Thickness (S) field. If the
schedule value is selected, the program automatically enters the appropriate value for this field.
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Tube wall thickness schedule
Specifies the average tube wall thickness in terms of a schedule value for tubes in the process coil of a
cylindrical heater. You can specify this value for up to 5 different sets in a single parallel flow path.
Choices
*** – no schedule selected
S40 – Schedule 40
S80 – Schedule 80
S160 – Schedule 160
Required: No
Units: n/a
Default: ***
Note
When you select a value for this field, the actual wall thickness is automatically entered in the
Thickness field.
Tube metallurgy
Specifies the construction material for the tubes in the process coil of a cylindrical heater. You can specify
this value for up to 5 different sets in a single parallel flow path.
Required: Yes
Units: n/a
Default: MED-CS
Materials Table
Name ASTM specification
LOW-CS A161, A192
MED-CS A53Gr B(S), A106 Gr B, A210 Gr A-1
C.5MO A161 T1, A209 T1, A335 P1
1.25CR A213 T11, A335 P11, (A200 T11 not included)
2.25CR A213 T22, A335 P22, (A200 T22 not included)
3CR A213 T21, A335 P21, (A200 T21 not included)
5CR A213 T5, A335 P5, (A200 P5 not included)
5CR SI A213 T5b, A335 T5b
7CR A213 T7, A335 P7, (A200 T7 not included)
9CR A213 T9, A335 P9, (A200 T9 not included)
T304 and H A213, A271, A312, A376; All types 304 and 304 H, C >
0.4%
T316 and H A213, A271, A312, A376; All types 304 and 304 H, C >
0.4%
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Name ASTM specification
T321 A213, A271, A312, A376, C > 0.4%
T321H A213, A271, A312, A376; All types 321H
T347H A213, A271, A312, A376; All types 347 and 347 H, C >
0.4%
800H B407 alloy – avg. grain size ASTM #5/coarser
HK40 A608 GR HK-40
T410 11 CR (for fin tube material only)
OTHER User-defined material
Number of tubes in 1 pass
Specifies the number of tubes of this geometry present in one parallel flow path for a cylindrical heater.
You can specify this value for up to 5 different sets in a single parallel flow path.
Required: Yes
Units: n/a
Default: None
Note
The sum of this field for all outlet sets must equal the value entered for the number of tubes per pass.
Center-center spacing
Specifies the distance between tubes (tube center to tube center) in one parallel flow path in the process
coil of a cylindrical heater. You can specify this value for up to 5 different sets in a single parallel flow
path.
Required: Yes
Units: mm (SI), in. (US), mm (MKH)
Default: None
Note
This value must be larger than the tube outside diameter in the same outlet set.
Effective tube length
Specifies the straight length of tubes in one parallel flow path in the process coil of a cylindrical heater.
You can specify this value for up to 5 different sets in a single parallel flow path.
Required: Yes
Units: m (SI), ft (US), m (MKH)
Default: None
Note
Do not include any bend allowance in this value.
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Thermal conductivity
Specifies the conductivity of the tube material in the radiant coil.
Required: No
Units: W/m °C (SI), Btu/hr ft °F (US), kCal/hr m °C (MKH)
Default: None
Note
This field is required only if you select OTHER for the tube metallurgy.
Duty basis
Specifies what duty is to be matched by the program. The choices are
Fuel
Duty is calculated based on combustion of fuel as specified
Radiant
Xfh adjusts flow rate of fuel to achieve specified duty in the radiant section
Radiant + convective
Xfh adjusts flow rate of fuel to achieve specified duty in the radiant and convective sections
Required: Yes
Units: None
Default: Fuel
Note
If you select either of the two specified duty options, you must also specify the radiant section duty or
the average flux in the radiant section. If you select the specified total duty (radiant + convective), you
must also specify the number of convection section process fluids (counted from the bottom of the
convection section) to be included in the specified duty.
Specified duty
Specifies the desired duty in the radiant section. The fuel flow rate is adjusted to achieve the desired duty.
Required: Yes (if Specified radiant duty option is selected)
Units: megawatts MM Btu/hr MM kcal/hr
Default: None
Note
You may specify either this field of the average radiant flux value.
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Average radiant flux
Specifies the average flux in the radiant section. The fuel flow rate is adjusted to achieve the desired flux.
Required: Yes (if Specified radiant duty option is selected)
Units: W/m² (SI), Btu/ hr ft² (US), kcal/hr m² (MKH)
Default: None
Note
You may specify either this field or the radiant section duty value.
Number of convection fluids included in specified duty
Specifies the number of convection section fluids (counted from bottom) to include in the specified duty.
Required: Yes (if Specified radiant + convective duty option is selected)
Units: None
Default: None
Note
Use this field to exclude some convection section fluids from the specified duty. For example, you may
have a duty requirement on the process fluid, but the convection section also includes steam
generation bundles in addition to the process fluids. By specifying the number of process fluids, you
exclude the steam generation from the specified duty. In the current program, there is no way to
exclude a fluid from the specified duty if it is not at the top of the convection section.
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Insulation Loss Coefficient Panel
This panel allows specification of heat loss correlations for the insulation in various parts of a cylindrical
heater firebox. The heat loss is expressed in terms of a correlation as a function of the insulation inside
surface temperature. The form of the correlation is
2TCTBALossHeat
where T is the insulation inside surface temperature. Separate correlations can be specified for the
firebox wall, roof, and floor.
Select any of the fields below to learn more about it.
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Insulation heat loss coefficients
Specifies coefficients in a correlation for heat loss through the firebox walls in a cylindrical heater.
Separate correlational constants are used for the walls, roof, and floor.
Required: No
Units: SI US MKH
A Watt/m² Btu/hr ft² Kcal/hr m²
B Watt/m² K Btu/hr ft² R Kcal/hr m² K
C Watt/m² K² Btu/hr ft² R² Kcal/hr m² K²
Default:
A 0.0
B 1.135 Watt/m² K (0.2 Btu/hr ft² R (0.977 Kcal/hr m² K))
C 0.0
Emissivities Panel
This panel allows specification of optional parameters related to the emissive characteristics of
components in the firebox.
Select any of the fields below to learn more about it.
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Flue gas extinction coefficient
Specifies the extinction coefficient for the flue gas.
Required: No
Units: 1/m (SI), 1/ft (US), 1/m (MKH)
Default: 0.0
Note
For gas fired heaters, this value should be set to 0.0. For oil or mixed firing, this value should be set to
10% of the volume fraction of the firebox occupied by the burner flames. For example, if the burner
flames occupy 15% of the volume, the extinction coefficient should be set to 0.10 (0.15) = 0.015.
Mean beam length
Specifies the mean beam length for your firebox geometry. To the right of this field are two radio buttons
that let you choose whether the beam length is program-calculated or user-specified.
Required: Yes (if you select the user-specified option)
Units: m (SI), ft (US), m (MKH)
Default: Program-calculated
Note
Because Xfh uses a zoning method, the mean beam length used by the software (or specified by the
user) is not intended to represent the mean beam length of the actual heater. It is simply a starting
point that allows Xfh to fit gas emissivity as a function of KL (absorbtivity * path length).
Xfh takes the starting value and divides it several times to produce a range of beam lengths. Then
when calculating the exchange areas (effectively view factors for the individual zones), it bases actual
lengths between zones on the correlation previously developed. Thus, the value entered in Xfh needs
to provide for a proper range of values needed to develop the gas emissivity correlation.
The path length specified should be close to the maximum path length (typically, the diagonal) present
in the system. Unless the maximum beam length is significantly larger (several times), the default
value should be acceptable because zones that are far apart have smaller and smaller exchanger
areas.
Process tube emissivity
Specifies the emissivity factor to use in calculating the radiation heat transfer to the process tubes in the
firebox.
Required: No
Units: None
Default: 0.94 (Cylindrical), 0.60 (Box)
Note
Typical values are 0.94 for carbon steel and 0.60 for stainless steel. See Chapter 4 Appendix of
Radiative Transfer by H. C. Hottel and A. F. Sarofim for a compilation of additional emissivity values.
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Refractory surface emissivity
Specifies the emissivity factor for calculating the radiation heat transfer to/from the refractory surfaces in
the firebox.
Required: No
Units: None
Default: 0.60
Note
See Chapter 4 Appendix of Radiative Transfer by H. C. Hottel and A. F. Sarofim for a compilation of
additional emissivity values.
Roof sink surface emissivity
Specifies the emissivity factor for calculating the radiation heat transfer to/from the roof surface in the
firebox.
Required: No
Units: None
Default: 1.00
Note
For cases with a convection section, Xfh calculates an effective surface emissivity for the roof sink; to
mimic the shock tubes, the program uses the input value of the distance to the first tuberow. If you
specify both the surface emissivity of the roof sink and the distance to the first tuberow, the program
uses the input value for the roof sink emissivity, overriding the calculated value of the shock tube
effective emissivity.
For cases without a convection section, specification of a roof sink surface emissivity means that
some heat is absorbed by the roof surface.
The roof sink duty appears as shock tube duty on the Output Summary and on the Cylindrical Radiant
Section Energy Balance report.
Roof sink surface temperature
Specifies the surface (sink) temperature of the firebox roof of a cylindrical heater. This optional parameter
is used to calculate the radiation transfer to the roof.
Required: No
Units: °C (SI), °F (US), °C (MKH)
Default: 482.2 °C (900 °F)
Note
For this value to be used, you must also set the roof emissivity to a value other than 0 or 1.
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Flue Gas Circulation Panel
This panel is used to specify optional items related to solving a cylindrical radiant section. Normally, the
items on this panel should be left at the default values.
Induced flow factor
Specifies the fraction of distance between the roof opening and the tube circle where the boundary for the
induced flow is connected on the roof plane.
Required: No
Units: None
Default: 0.25
Note
The default value is based on matching data from an actual vacuum heater. If you are trying to match
operating data, adjust this parameter to match the bridgewall (arch) temperature. This value must be
greater than 0 and less than 1.
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Maximum recirculation factor
Specifies an adjustment factor for the location of the maximum recirculation plane.
Required: No
Units: None
Default: 0.50
Note
The default value is based on matching data from an actual vacuum heater. If you are trying to match
operating data, adjust this parameter to match the bridgewall (arch) temperature. A larger value for
this field implies a larger conservation of momentum zone and tends to lower the bridgewall
temperature. This value must be greater than 0 and less than 1.
Burner throat pressure drop constant
Specifies a constant used in calculating the pressure drop across the burner throat. K is defined in the
following equation:
2)velocityair()densityair()(1droppressureBurner KC
where C1 is a constant that depends upon the units of density and velocity (e.g., 0.003 for US units).
Required: No
Units: None
Default: 4.50
Burner Parameters
The program contains parameters for many common burners. For box heaters, select these burner types
on the Burner Parameters panel. For cylindrical heaters, refer to the information below and enter the
desired parameters.
Vendor Burner Fuel Type Heat Release
(MM Btu/hr)
Excess Air
(%)
Head
(in. H2O)
Flame Length
(ft)
DELP
(K)
A B
JZ MA, DBA (50TIP) FO 3 – 20 15 0.25 2.700 0.5 4.511
JZ MA, DBA (40TIP) FO 3 – 20 15 0.25 1.780 0.6 4.511
JZ HEVD (SPIDER) GAS 4 – 18 15 0.25 1.600 0.7 3.639
JZ VYD (NO AIRPMX) GAS 3.5 – 20 15 0.25 1.950 0.61 5.874
CEA 60 F GAS/FO 5 – 15 5 2.00 5.500 0.340 1.995
CEA 600 F GAS/FO 5 – 15 5 2.00 5.030 0.340 1.995
CEA 60 F GAS/FO 5 – 15 5 4.00 3.840 0.340 1.995
CEA 600F GAS/FO 5 – 15 5 4.00 3.470 0.340 1.995
URQUHRT STCC GAS/FO 5 – 140 5 – 15 10.00 2.000 0.480 4.500
URQUHRT TUNNEL GAS/FO 5 – 140 5 – 15 10.00 3.500 0.4 4.500
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Vendor Burner Fuel Type Heat Release
(MM Btu/hr)
Excess Air
(%)
Head
(in. H2O)
Flame Length
(ft)
DELP
(K)
A B
DUIKER REG N, CUP GAS/FO 20 – 120 2 – 5 4.00 6.310 0.322 4.764
DUIKER REG N, CONE GAS/FO 20 – 120 2 – 5 8.00 4.210 0.322 4.764
DUIKER REG N, CUP GAS/FO 20 – 120 2 – 5 4.00 7.050 0.322 4.764
DUIKER REG N, CONE GAS/FO 20 – 120 2 – 5 8.00 4.530 0.322 4.764
COPPUS FANMIX GAS 4.5 – 75 10 0.10 1.000 0.462 4.5
COPPUS FANMIX FO 8 – 42 10 0.10 1.500 0.462 4.5
GULF VORTOMAX 5 – 200 3 6.00 0.865 0.540 4.5
GULF VRTMX+TUNNEL 5 – 200 3 8.00 1.700 0.532 4.5
N.AMER. INTEGRAL FO 4 – 30 20 0.30 2.000 0.634 4.5
Pressure in heater
Specifies the pressure inside the radiant heater.
Required: No
Units: kPa G (SI), psig (US), kgf/cm² G (MKH)
Default: Atmospheric pressure
Note
Normally, you should not specify this value for process heaters that operate at atmospheric pressure.
The value of pressure is used to calculate the flue gas properties inside the radiant section.
Flow Field Simulation in Cylindrical Heaters
The flow field algorithm for cylindrical heaters is based on a simplified jet flow theory with three flow
regimes.
Conservation of momentum
Dissipated momentum
Dissipation-induced flow
The flow field, tube layout, and heat transfer are assumed to be axi-symmetrical. The flow boundary is
defined by the burner nozzle diameter, the jet angle, the tube circle, and the roof opening. A rectangular
opening for flue gases exiting the radiant section is replaced by a circle of equivalent area.
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The induced flow factor (FIF) determines the position of the point (RIF) on the roof where the induced flow
line is connected to/from the tube circle on the induced flow plane (IF). IF is the plane where the upflow
flue gas from the burners hits the tube circle. The induced flow factor is defined as
RRO)(RTCRRO)(RIFIF
The value for IF is established by matching plant arch temperature data.
Weighting factors for convective heat transfer
Specify the weighting factors for free and forced convective heat transfer to the radiant tubes. These
factors are used as
)DTTC)(NuForcedFForcedNuFreeFFree(tcoefficienConvective
where
FFree = weighting factor for free convection
NuFree = Nusselt number for free convection
FForced = weighting factor for forced convection
NuForced = Nusselt number for forced convection
TC = thermal conductivity
DT = tube diameter
Required: No
Units: None
Default: Forced – 1.5
Free – 1.0
Note
Use the default values unless you are trying to match operating data.
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Output Reports
Xfh produces a number of spreadsheet-style output reports. To view any of these reports, simply click the
report name in the tree view on the left side of the interface window. Xfh automatically displays the
reports after you run a case. To view reports at other times, click the Reports button on the toolbar.
The list below includes all of the reports that Xfh produces. Some are generated by all of the calculation
modules while others are specific to a module.
Reports Produced for All Runs Combustion
Run Log Diagram
Data Check Messages Flue Gas Heat Release
Runtime Messages Combustion Stream Properties
Input Reprint Convection
Property Monitor Convection Summary
Stream Properties Convection Flue Gas Monitor
Convection Process Monitor
API 530 Stack Monitor
Process Heat Transfer Coefficient Cylindrical
Metal Temperature Output Summary
Thickness Design Temperature Profile
Life Evaluation Firebox Monitor
Metal Properties Firebox Tables
Single-Zone Heater Flow Distribution Monitor
Single-Zone Firebox Monitor Cylindrical Heater Profile
Cylindrical Radiant Section Energy Balance
API560 Specification Sheet
Box Heater
Output Summary Flow Distribution Monitor
Gas Space Energy Balance Gas Temperature Monitor
Flue Gas Flow Monitor Tube Flux Monitor
Firebox Monitor No Tube Flux Monitor
Firebox Tables API560 Specification Sheet
Burner Monitor Tube Numbers
NOTE: The API530 module lets you select which API 530 calculations Xfh performs. Only the
reports associated with the specified calculations are produced for a given run.
The Box Heater and Cylindrical modules can include integrated combustion and
convection sections; Xfh produces all associated reports.
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Output Summary
The Output Summary report, generated by the Box Heater and Cylindrical modules, presents a one-page
summary of the overall results.
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Run Log
Generated by all calculation modules, the Run Log report contains an audit trail of the calculations that
the Xfh engine performs. For example, when producing radiant calculations, the run log lists the iterations
performed between the process and radiant side calculations. If the calculations abort for any reason, the
log indicates how far the calculations progressed.
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Data Check Messages
Produced by all calculation modules, the Data Check Messages report contains diagnostics that the
program generates when reading input data. The messages are classified as Informative, Warning, and
Fatal.
Informative
Xfh has detected a condition that may be significant. The input data may appear unusual (for example,
the physical property slopes in a different direction than expected). Xfh continues calculations.
Warning
Xfh has detected a condition that is significant. The program may have detected inconsistent input that
it corrected. Xfh continues calculations.
Fatal
Unrecoverable input error. Xfh stops calculations at this point.
Xfh may produce multiple pages for the Data Check Messages report. Each page represents a separate
portion of the calculations. The radiant-side calculations appear on one page, the convection section
produces a separate page for each process fluid, and the firebox includes one page for cylindrical heater
process calculations and one page for each process pass in a box heater.
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Runtime Messages
The Runtime Messages report is generated by all calculation modules. It contains diagnostics that Xfh
produces when performing the process and radiant calculations. The messages generated are classified
as Informative, Warning, and Fatal.
Informative
Xfh has detected a condition that may be significant and generates full output results.
Warning
Xfh has detected a condition that is significant. The program may have detected an operating
condition outside of a normal range. Xfh generates full output results.
Fatal
Unrecoverable error. Xfh stops calculations at this point. Any results generated are untrustworthy.
Xfh may produce multiple pages for the Runtime Messages report. Each page represents a separate
portion of the calculations. The radiant-side calculations appear on one page, the convection section
produces a separate page for each process fluid, and the firebox includes one page for cylindrical heater
process calculations and one page for each process pass in a box heater.
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Input Reprint
Generated by all calculation modules, the Input Reprint report lists all the input that Xfh used to perform
calculations, either entered data or default values that you did not override.
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Combustion Diagram
When Xfh runs combustion calculations, it produces a Combustion Diagram report containing a diagram
of the streams in the combustion process. For each stream, Xfh reports the temperature and flow rate.
For fuel streams, the report includes the LHV (Lower Heating Value); for oxidant streams, it provides the
percent excess.
For each combustion process, the report details the adiabatic flame temperature, pressure, flue gas flow
rate, and heat release. The percent O2 on a dry basis is also indicated. For multiple fuels, the mixed
temperature is reported.
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Combustion Stream Properties
The Combustion Stream Properties report gives inlet and outlet calculated physical properties of each
stream. For fluids with multiple components, liquid and vapor compositions and vapor liquid equilibrium K-
values for each component are also printed.
Xfh prints properties at the inlet and outlet of each fired heater process pass and the flue gas path in the
stack. These values are taken from the property profiles, detailed in the Property Monitor report.
Four sets of data appear on the print-out: Pressure – Volume – Temperature physical properties, vapor
properties, liquid properties, and stream molar composition. Any fields that do not apply to the fluid
condition remain blank. For example, if the fluid stream is all vapor, then liquid properties remain blank.
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Flue Gas Heat Release
For combustion calculations, Xfh produces a Flue Gas Heat Release report, listing the physical properties
of the flue gas over a range of temperatures. Additionally, the report details the percent heat removed
from the flue gas at each temperature. This data proves useful if you want to determine the exit flue gas
temperature required to achieve a certain thermal efficiency.
If Xfh performs firebox calculations in the Box Heater or Cylindrical modules, this report provides the
weighting factors for calculating gas emissivity and absorptivity.
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Process Heat Transfer Coefficient
When Xfh runs the API530 module and you request calculation of the process heat transfer coefficient,
Xfh produces this report listing the calculated process heat transfer coefficient as well as some physical
properties and other values used in the calculation. Xfh uses methods from Section C.23 of API 530.
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Metal Temperature
When Xfh runs the API530 module and you request calculation of the metal temperature, Xfh produces
this report listing the temperatures from the inside process bulk temperature to the outside temperature of
the process tube. Xfh uses methods from Section C.4 of API 530.
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Thickness Design
When Xfh runs the API530 module and you request calculation of the required tube thickness, Xfh
produces this report containing the required tube metal temperature based on API530 methods. Both
elastic and rupture designs are considered and the limiting value chosen. Quantities used to calculate the
required tube thickness also appear in the report.
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Life Evaluation
When Xfh runs the API530 module and you select the tube life evaluation option, Xfh produces this three-
page report. If you enter past history operating conditions, Xfh generates a table indicating the fraction of
tube life consumed by previous tube operations as well as the expected tube life based on the specified
conditions and the maximum operating temperature allowed for a specified tube life.
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Metal Properties
When Xfh runs the API530 module and you choose to print the metal properties, Xfh produces this report.
Choose this option on the API530 Summary panel. The Metal Properties report displays several metal
properties over a range of temperatures and Larson-Miller parameters that you specify.
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Convection Summary
When a convection section is present, Xfh produces the Convection Summary report, containing overall
performance values for the entire convection section. The report also includes a section for flue gas
process conditions and for each process fluid in the convection bundle.
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Convection Flue Gas Monitor
When a convection section is present, Xfh generates a Convection Flue Gas Monitor report, displaying
flue gas conditions on a row-by-row basis. Row 1 is the row closest to the firebox.
Convection Process Monitor
When a convection section is present, Xfh generates the Convection Process Monitor report. It contains a
table following the process fluid through one complete process pass. At increments along the process
path, it also indicates local temperature, pressure, heat transfer coefficients, and other values.
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Heater Temperature Profile
When Xfh runs a cylindrical heater case, it produces this report, displaying the gas, tube, and refractory
temperatures on a local basis.
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Cylindrical Firebox Monitor
When Xfh runs a cylindrical heater case, it generates a Cylindrical Firebox Monitor report, containing a
table following the process fluid through one complete process pass. At increments along the process
path, it also indicates local temperature, pressure, heat transfer coefficients, and other values.
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API560 Specification Sheet
Generated for box heater and cylindrical calculation modules, the standard API560 specification sheet
includes all information that you enter or that Xfh calculates. Those values that are unknown remain
blank.
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Gas Space Energy Balance
When Xfh runs a box heater case, it generates a Gas Space Energy Balance report which provides an
overall energy balance for the firebox. The report displays items such as total energy available via the
burners, duty absorbed by the process coil, and setting losses through each wall.
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Flue Gas Flow Monitor
Generated for box heater cases, this report includes one page for each gas space in the heater. Each
page shows a mass balance indicating the flue gas flowing across the separate boundaries of each gas
space.
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Box Heater Firebox Monitor
When Xfh runs a box heater case, it produces this report, containing a table following the process fluid
through one complete process pass. At increments along the process path, it also indicates local
temperature, pressure, heat transfer coefficients, and other values. A separate report is generated for
each process pass in the firebox.
Use the Box Tube Numbers drawing to help you identify the tube associated with the output results.
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Burner Monitor
For a box heater case, Xfh generates this report that details burner parameters such as location, heat
generated, flame length, throat velocity, and other values. A separate page is produced for each gas
space.
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Flow Distribution Monitor
When Xfh runs a box heater case, it produces this report, displaying the local flows of flue gas within the
box heater. A separate report is generated for each gas space.
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Gas Temperature Monitor
For a box heater case, Xfh generates this report, displaying the gas temperature in each local zone within
the firebox. A separate report is produced for each gas space.
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Tube Flux Monitor
Generated for box heater cases, this report lists the average and maximum fluxes as well as the fraction
heat transferred by convection along the length of each tube. This same information is reported in the Box
Heater Firebox Monitor, but this report lists the information in physical tube order rather than process flow
order as in the Box Heater Firebox Monitor. This ordering makes it easier to determine the physical
location of tubes with flux problems.
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Cylindrical Heater Profile
1
These lines contain information about the inside roof of the cylindrical heater.
Sink temperature in this roof zone
If a value is blank (****** in previous versions), there is no radiant sink in this roof zone. A value on
this line indicates the presence of a convection section with radiant transfer between the firebox and
the shock tubes. The temperature represents the equivalent sink temperature of the shock tubes in
the convection section.
Refractory temperature in this roof zone
A blank value (****** in previous versions) indicates the presence of a convection section with radiant
transfer between the firebox and the shock tubes.
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Fraction sink in this roof zone
A value of zero (0) indicates no radiant heat transfer through this roof zone. A value of one (1)
indicates the presence of a convection section with radiant heat transfer between the firebox and the
shock tubes. A value between zero and one indicates that this zone is partially visible to the
convection section and partially refractory.
2
These three lines contain information about the flue gas in a zone.
Temperature of the flue gas flowing upwards in this zone
Temperature of the flue gas flowing downwards in this zone
A blank value (****** in previous versions) appears if there is no flow downwards in this zone.
Fraction of gas zone volume filled by upflow
A value of 1.0 indicates no downflow in this zone.
3
These three lines contain information related to the process tube.
Front and back sink temperature of the process tube
Refractory temperature not covered by tube
If the tube runs the entire length of this zone, this value will be blank (****** in previous versions).
Fraction of zone length covered by tube
4
Flue gas temperature behind tube
5
Temperature of refractory behind tube
6
These three lines contain information about the inside floor of the cylindrical heater.
Sink temperature in this floor zone
Since there are no radiant sinks on the floor of a cylindrical heater, this value is blank (****** in
previous versions).
Refractory temperature in this floor zone
Fraction of this zone covered by radiant sink
This value is zero (0) for a cylindrical heater.
7
Vertical zone number
The cylindrical heater is divided into 10 sections from the inside floor to the inside roof.
8
Radial zone number
Zone 1 starts at the centerline of the heater, and Zone 5 ends at the process tubes. Zone 6 is located
behind the process tubes.
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NOx Conversion Factors
Xfh does not calculate the amount of NOx produced during combustion. These values are very
dependent on the burner and firebox geometry. The best source of NOx emission information is the
burner manufacturer who can usually provide a range of PPMV NOx produced by the burner. Using this
information, Xfh calculates several conversion factors that allow you to convert the vendor numbers easily
into total NOx produced, as shown below:
NOx conversion (HHV) – Multiply the number on the output by PPMV NOx to calculate
lbs NOx / MMBtu (HHV)
NOx conversion (LHV) – Multiply the number on the output by PPMV NOx to calculate
lbs NOx / MMBtu (LHV)
NOx conversion (3% O2) – Multiply the number on the output by PPMV NOx @ Actual O2 to
calculate PPMV NOx @ 2%
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Box Heater Firebox Tables
When Xfh runs a box heater case, it produces this report containing multiple tables following the process
fluid through all process passes. Each table reports one process variable (e.g., process temperature) at
increments along the flow path. This information is also reported on the Box Heater Firebox Monitor.
The format of this report allows you to follow easily a single variable through the entire tubeside flow path.
Select the tables using the tabs at the bottom of the report.
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Cylindrical Firebox Tables
When Xfh runs a cylindrical heater case, it produces this report containing multiple tables following the
process fluid through one complete process pass. Each table reports one process variable (e.g., process
temperature) at increments along the flow path. This information is also reported on the Cylindrical
Firebox Monitor.
The format of this report allows you to follow easily a single variable through the entire tubeside flow path.
Select the tables using the tabs at the bottom of the report.
Stack Monitor
This output report details the properties of the flue gas leaving each stack element.
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Property Monitor
The Property Monitor report details the temperature and pressure property profiles of every stream in the
fired heater case.
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No Tube Flux Monitor
This report details the calculated fluxes, sources, and gas temperatures to every sink zone for the No
Tubes option in box heaters.
Every sink zone has a number. You can see the sink zones and their numbers in the Surface Zone
Numbering diagrams.
Surface Zone Numbering
Top, Bottom Front, Back, Left, Right
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Gas Zone Numbering
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Single-Zone Firebox Monitor
This report details radiant section output from a single-zone model.
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Stream Properties
The Stream Properties report gives information concerning calculated physical properties of hot and cold
fluids. For fluids with multiple components, liquid and vapor compositions and vapor liquid equilibrium K-
values for each component also print.
The report prints properties at inlet and outlet of the exchanger, taking the values from the property
profile, stored at three reference pressures. Reference pressures for the Component Physical Properties
printout appear in line 5 of the heading. The following four sets of physical property data appear on the
printout:
Lines Physical Property Data
1 – 4 Temperature, pressure, and weight fraction vapor
5 – 10 Mixture vapor local physical properties
11 – 18 Mixture liquid local physical properties
19 – 20 Composition and vapor-liquid equilibrium K-values
Any lines that do not apply to the fluid condition (for example, liquid properties when the fluid is a single-
phase vapor) remain blank.
Most items on Stream Properties are self-explanatory. However, two lines require additional explanation.
Line Printed Heading Comments
10 Molecular Wt. Values of vapor's molecular weight corresponding to mixture
reference temperatures (Line 30)
If you input properties on Hot (or Cold) Fluid Profile Properties Data
Form, this line remains blank because molecular weights have not
been input.
16 Molecular Wt. Values of liquid's molecular weight corresponding to mixture
reference temperatures (Line 30)
If you input properties on Hot (or Cold) Fluid Profile Properties Data
Form, this line remains blank because molecular weights have not
been input.
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Box Tube Numbers
The program assigns each tube a unique number, and this report shows the tube numbering sequence
used for box heaters.
The Box Tube Number report is especially useful when you interpret the location of locally calculated
values when you refer to other reports such as the process monitor. For example, look at the following
process monitor.
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To determine the physical locations of the first four increments in the heater, use the tube number (in this
case, 17) from the process monitor, and then refer to the Box Tube Numbers report. The first four
increments are located in the top left tube.
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Cylindrical Radiant Section Energy Balance
The Cylindrical Radiant Section Energy Balance report lists the duty absorbed by the process coil, the
duty lost through the refractory, and the duty absorbed by the roof sink/shock tubes, summing and
comparing them to the total duty entering the radiant section. Additionally, the report breaks down the
heat loss into two components: the heat lost in zones that contain sink (tube) area and the heat lost in
zones without sink (tube) area.
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Test Cases
This section describes the standard test cases for Xfh. These cases are provided as sample inputs to
help you get started in creating your own cases. You can also run these cases and review the output to
learn more about how Xfh works and what you can expect from the program.
These test cases show the type and variety of cases that Xfh can run. These cases are installed in the
Samples subdirectory in the Xchanger Suite application directory. By default, this directory is located at
C:\HTRI\XchangerSuite4\Samples.
The group of test cases is named Xfh_StandardCasex.htri where x is an integer from 1 to 12. You can
load and run these binary input files from the GUI. The first seven of these cases are described in more
detail in this section.
1: Two fuel combustion calculation
2: Combustion with specified duty and losses
3: API 530 tube design calculation
4: Standalone convection section calculation
5: Cylindrical firebox calculation
6: Cylindrical heater with convection section
7: Box heater with convection section
8: Box heater with multiple gas spaces and shared tubes
9: Double-cell box heater
10: Standalone cylindrical heater with a boiling process fluid
11: Three gas spaces with twice the burner heat release in the middle gas space
12: Multiple gas spaces with two tube rows between gas spaces
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Test Case 1
This input demonstrates how to set up a combustion calculation. Combustion calculations can be run by
themselves or in combination with a radiant firebox simulation. The input setup is the same in both cases.
This case illustrates mixed fuels used, for example, in a heater that is burning both oil and gas or just two
types of gaseous fuels. Case 1 also demonstrates the two different methods of specifying fuel properties.
The gaseous fuel is specified by defining the composition, while the liquid fuel is specified by providing
some overall properties. In this case, we have specified more than the minimum required information.
Liquid and solid fuels can be specified by providing the ultimate analysis for the fuel which has been done
in this case. We have also specified the API gravity of the fuel oil. Either one of these two specifications
would have been sufficient to define the fuel.
For both fuels, ambient air has been used as the oxidant. For the fuel oil, steam is specified as a diluent
stream.
Finally, a duty specification was used to specify the flow rate of both fuels. The program allows
specification of the fuel flow rate directly, but will also calculate the flow rate required to release the
desired amount of heat.
Gaseous Fuel
Flow rate (megawatts of duty) 11.63
Pressure (kPa) 206.81
Inlet temperature (°C) 26.67
Excess oxidant 20%
Composition (Volume %)
Methane 23
Propane 41
n-Pentane 8
Sulfur dioxide 10
Carbonyl sulfide 9
Methanol 9
Fuel Oil
Flow rate ( megawatts of duty) 11.63
Pressure (kPa) 308.17
Inlet temperature (°C) 100
Excess oxidant 20%
Ultimate analysis (%)
Carbon 87
Hydrogen 10
Sulfur 3
API gravity (Degrees API) 20.8
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Results
When the case is run, Xfh calculates the adiabatic flame temperature as well as the required amount of
fuel and oxidant. The combustion results are reported on three main reports.
Combustion Diagram – This report diagrammatically illustrates the combustion process specified,
showing the fuel, oxidant, and diluent rates for each fuel. The diagram also indicates the outlet
temperature, heat released, and flue gas flow rate for each fuel as well as the excess oxygen after
the combustion process.
Stream Properties – This report lists the composition and physical properties of each process
stream through the combustion process.
Flue Gas Heat Release – This report lists the physical properties and heat release of the
generated total flue gas from the adiabatic flame temperature to 15.56 °C (60 °F).
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Output
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Test Case 2
This case is another combustion problem demonstrating a feature of the combustion module that allows a
quick calculation of the flue gas outlet temperature for a radiant firebox. The same fuels as in Test Case 1
are used. On the Calculation Options panel, the desired duty of the firebox is specified along with
expected losses. Using the enthalpy of the combusted flue gas, the program calculates the flue gas outlet
temperature out of the firebox. The program also allows specification of the desired flue gas temperature
as an alternate specification.
Gaseous Fuel
Flow rate (megawatts of duty) 11.63
Pressure (kPa) 206.81
Inlet temperature (°C) 26.67
Excess oxidant 20%
Composition (Volume %)
Methane 23
Propane 41
n-Pentane 8
Sulfur dioxide 10
Carbonyl sulfide 9
Methanol 9
Fuel Oil
Flow rate (megawatts of duty) 11.63
Pressure (kPa) 308.17
Inlet temperature (°C) 100
Excess oxidant 20%
Ultimate analysis (%)
Carbon 87
Hydrogen 10
Sulfur 3
API gravity (Degrees API) 20.8
Operating Parameters
Firebox duty (megawatts) 13.1795
Losses (Percent of duty) 2
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Results
The results are very similar to those of Test Case 1 which is expected as the same fuels are being
combusted. If the Combustion Diagram report is examined, the main difference is the outlet temperature
of the combustion process. The outlet temperature is now much lower as the specified duty and losses
have been removed from the flue gas. The specified duty and losses are conveniently reported on the
Combustion Diagram report.
Output
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Test Case 3
This case demonstrates the API 530 calculation options of FH. API 530 is a standard for determining the
required wall thickness for tubes in the radiant section of a fired heater. API 530 also includes a
procedure for estimating the expected life of a radiant tube.
In addition to these two main calculations, there are also two supplementary calculations performed in
support of the main calculations. These are
1 Tubeside process heat transfer coefficient
2 Tube metal temperatures
In the example below, we have chosen to perform all of these calculations.
Tube Geometry
Tube outside diameter (mm) 141.3
Wall thickness (mm) 9.525
Tube material 9 Cr steel
Center-to-center tube spacing (mm) 254
Tube length (m) 19.81
Operating Conditions
Maximum design pressure (kPaG) 4136.85
Operating pressure at start of run (kPaG) 2757.9
Operating pressure at end of run (kPaG) 3447.38
Process fluid temperature (°C) 454.45
Process flow rate (kg/hr) 69953.7
Process fluid pressure (kPaG) 2757.9
Weight fraction vapor 0.27
TEMA fouling factor (m² K/W) 0.0
Average tube flux (W/m²) 25954.53
Design Parameters
Design life (hours) 100,000
Corrosion allowance (mm) 2.997
Run time (years) 2
Past Operating History
Onstream time (years) 5
Operating pressure at start of run (kPaG) 3447.38
Operating pressure at end of run (kPaG) 3447.38
Metal temperature at start of run (°C) 426.67
Metal temperature at end of run (°C) 537.78
Corrosion rate (mm/yr) 0.254
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Future Operating Conditions
Operating pressure at start of run (kPaG) 3447.375
Operating pressure at end of run (kPaG) 3447.375
Metal temperature at start of run (°C) 482.2
Metal temperature at end of run (°C) 593.3
Corrosion rate (mm/yr) 0.254
In addition to the above parameters the process fluid physical properties are specified at start of run and
end of run conditions. These properties are needed for heat transfer coefficient calculation.
Output
Because all API 530 calculation options were requested, the program generates several output reports.
API 530 Process Heat Transfer Coefficient
This report shows the calculated process heat transfer coefficient at the start of run (first column)
and end of run (second column) process conditions specified in the input. In addition to the two-
phase coefficient, the program reports a number of intermediate values and input used to calculate
the heat transfer coefficient.
API 530 Metal Temperature
The main results of this report are the temperatures starting from the inside bulk process
temperature to the outside tube wall temperature. These are reported for the start of run (first
column) and end of run (second column) process conditions specified in the input. In addition to
these temperatures, the report also displays the values used to calculate the temperatures.
Thickness Design
The main API 530 calculation is the prediction of the required tube wall thickness. This report
contains a lot more information than just the minimum required thickness. The top half of the first
page echoes the input specifications while the bottom half reports the design results. Besides the
minimum required thickness, the results include other important information such as maximum
allowed operating temperature and whether the design was limited by elastic or rupture stress. The
section page contains the results from the elastic and rupture analysis.
Life Evaluation
This report displays results on the past operating history (if specified) and the predicted future life
of the tube. The first page reports the fraction of the tube life used by the past operating history of
the tube. There may be up to five sets of past operating process conditions. The second page
reports the predicted tube life based on the specified operating process conditions. If the predicted
tube life is longer than the input design life, the third page reports the maximum allowed operating
temperature to achieve the input design life.
Metal Properties
If a metal properties table is requested on the tube metallurgy panel, this report will be produced.
This report contains a table of metal physical properties over a user-specified range of
temperatures and Larson-Miller parameters.
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API 530 Process Heat Transfer Coefficient
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API 530 Output Metal Temperature
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Thickness Design
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Life Evaluation
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Metal Properties
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Test Case 4
This test case is a standalone convection section. The convection section calculations are run without a
radiant firebox defined. Because of this, the flue gas process conditions and composition must be
defined. This configuration is useful if you want to determine the required geometry to achieve a certain
convection duty or outlet flue gas temperature. Running a convection section by itself is quicker than
running an entire fired heater calculation.
Convection Geometry
Total tuberows 10
Process fluids 2
Convection section height Unspecified
Convection section width Unspecified
Process Fluid 1
Flow rate (kg/sec) 50.4
Inlet temperature (°C) 204.45
Inlet pressure (kPa) 250
Phase Liquid
Tuberows 9 – 10
Tube layout Staggered
Tubepasses 4
Process Fluid 2
Flow rate (kg/sec) 37.8
Inlet temperature (°C) 148.89
Inlet pressure (kPa) 250
Phase Liquid
Tuberows 9 – 10
Tube layout Staggered
Tubepasses 4
Flue Gas Process Conditions
Flow rate (kg/sec) 10.0799
Temperature (°C) 1037.78
Pressure (kPa) 103.421
Composition (Mole %)
Carbon dioxide 10.487
Water 14.751
Nitrogen 70.215
Oxygen 3.148
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Sulfur dioxide 0.517
Argon 0.882
Tube Geometry (Section 1)
Tuberows 1 – 2
Tubes/row 8
Tube type Plain
Tube length (m) 6.1
Tube diameter (mm) 101.6
Transverse pitch (mm) 304.8
Longitudinal pitch (mm) 203.2
Tube Geometry (Section 2)
Tuberows 3 – 10
Tubes/row 12
Tube type High fin
Tube length (m) 6.1
Tube diameter (mm) 101.6
Transverse pitch (mm) 203.2
Longitudinal pitch (mm) 203.2
In addition to the above items, it was also necessary to specify the process fluid compositions. The
process fluid and flue gas physical properties are calculated using the HTRI internal property databank.
Results
The convection summary shows a total duty of about 10 MW with the bulk of this duty (96%) being
absorbed by the first process fluid. This is expected since this fluid has the most heat transfer surface
area and is in the hottest portion of the flue gas stream.
Looking at the process monitor, the first two tuberows (shock tubes) have a relatively high flue gas heat
transfer coefficient. In row three, the coefficient drops significantly. This drop is caused by two effects.
First, the shock tubes see the highest gray gas radiation coefficient since they are in the hottest flue gas.
Secondly, row three starts the high-fin section, and the coefficient is based on the total extended heat
transfer surface area.
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Test Case 5
This case is a standalone cylindrical heater. For this case we must provide three types of information:
fuel flow rate and composition
heater geometry
process fluid conditions and physical properties
The fuel and geometry, and process conditions are listed below.
Combustion Fuel
Fuel type Gas
Flow rate (kg/hr) 342.47
Pressure (kPa) 239.25
Inlet temperature (°C) 15.56
Excess oxidant 15%
Composition (Volume %)
Methane 96.25
Carbon dioxide 0.91
Ethylene 2.84
Heater Geometry
Heater type Cylindrical
Height (m) 7.25
Diameter (m) 4.05
Flue Gas Opening
Length (m) 3.05
Width (m) 1.31
Burner circle diameter (m) 1.01
Number of burners 3
Tube circle diameter (m) 3.51
Tubepasses 2
Tubes per pass 18
Tube OD (mm) 114.3
Center-center spacing (mm) 304.8
Tube length (m) 3.84
Tube Material 1.25 Cr
Process Fluid Conditions
Flow rate (kg/sec) 33.74
Inlet temperature (°C) 343.33
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Inlet pressure (kPa) 1378.95
Phase Liquid
Process fouling factor (m² K/W) 0.00088
In addition to the above items, the process fluid physical properties were specified by defining the liquid
physical properties at two temperatures. The program will use linear interpolation to find properties at
other temperatures.
Results
As expected, the thermal efficiency is low (about 51%). Without a convection section, the outlet flue gas
temperature is high and only about half of the thermal energy is recovered by the radiant section.
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Test Case 6
In this case a convection section is added to Test Case 5 to improve thermal geometry. The combustion
parameter and heater geometry are the same as in Test Case 5. The convection geometry and process
fluid conditions are listed in the table below. The process fluid conditions are different from Test Case 5 to
reflect the fact that the process fluid goes into the convection section at a lower temperature and higher
pressure than when it reaches the radiant firebox.
Convection Section Geometry
Total tuberows 8
Process fluids 1
Convection section height (m) Unspecified
Convection section width (m) 1.32
Distance from heater roof to first tuberow (m) 0.945
Process Fluid Conditions
Flow rate (kg/sec) 33.74
Inlet temperature (°C) 326.67
Inlet pressure (kPa) 1585.79
Phase Liquid
Process fouling factor (m² K/W) 0.00088
Tube Geometry (Section 1)
Tuberows 1 – 3
Tubes/row 6
Tube type Plain
Tube length (m) 3.0
Tube diameter (mm) 114.3
Transverse pitch (mm) 203.2
Longitudinal pitch (mm) 176.28
Tube Geometry (Section 2)
Tuberows 4
Tubes/row 6
Tube type High fin
Fin height (mm) 25.4
Tube length (m) 3.0
Tube diameter (mm) 114.3
Transverse pitch (mm) 203.2
Longitudinal pitch (mm) 176.28
Tube Geometry (Section 3)
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Tuberows 5 – 7
Tubes/row 6
Tube type High fin
Fin height (mm) 25.4
Tube length (m) 3.0
Tube diameter (mm) 114.3
Transverse pitch (mm) 203.2
Longitudinal pitch (mm) 176.28
In addition to the above items, the process fluid physical properties were specified by defining the liquid
physical properties at two temperatures. The program will use linear interpolation to find properties at
other temperatures.
There are a couple of items to note about this input. The item Distance from heater roof to first
tuberow is used to calculate the amount of direct radiation from the firebox to the bottom of the
convection section. This option is only available for cylindrical heaters and is activated by specifying the
distance to the first tuberow and a guess for the bridge wall temperature (on the process panel).
The second item to note is the presence of tube section 2 with a single tuberow. With staggered layouts,
the program assumes that the first row in a given section is the non-offset row with the tube closest to the
left wall. If a tube section begins on an offset row, you must create a one row section with the actual left
wall clearance of this row. The next section will begin on a non-offset tube and you should specify the left
wall clearance appropriately.
Results
As expected, the thermal efficiency with a convection section is significantly higher than without. The
same heater without a convection section (Test Case 5) had a thermal efficiency only slightly higher than
50%. With a convection section the thermal efficiency has risen to 78% with the convection section
recovering about a third of the total absorbed duty.
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Test Case 7
Test Case 7 is a box heater with a convection section. This is a single cell end-fired box heater with
horizontal tubes on the left and right walls. The heater geometry is listed in the Input Reprint pages below.
The box heater geometry input is more complex than that for cylindrical heaters. This is caused by the
increased geometric flexibility of a box heater. The location of the tube coils, process flow, and burners is
more complex. In a cylindrical heater the tube coil is always located around the circumference of the
heater. In a box heater, tube coils can exist on any of the six walls and must be specified individually.
There is no automatic assumption of symmetry in a box heater. In a cylindrical heater, the process flow
path is known by simply specifying whether the fluid enters at the top or bottom. In a box heater, you must
define the process fluid flow paths on a tube by tube basis. Finally, burner locations can be either on the
end walls or the floor and the locations must be specified individually.
To specify the process fluid physical properties, the vapor and liquid physical properties are defined at
two temperatures. Xfh uses linear interpolation (except for viscosity) between these two temperatures.
Because the process fluid is two-phase (boiling) in the radiant firebox, the dew point and bubble point of
the fluid are also specified.
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Results
Just as the input for box heaters is more complex than for cylindrical heaters, so is the output. For
example, every process pass in a cylindrical heater is assumed to be the same. Thus, only one process
fluid monitor is reported. For box heaters, the process information is reported for each tubepass.
Looking at the output summary, the same type of information is reported for both box and cylindrical
heaters. In this case, a very good thermal efficiency of 89% is achieved. This number may not practical. If
you examine the average and maximum flux values you will see that they are higher than is typically
used.
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Frequently Asked Questions
Which radiant section type do I use?
You may choose from three radiant section types: cylindrical, box, and single zone. If you need to
see local effects of radiant and convective heat transfer inside the radiant chamber, choose the
cylindrical or box type as best fits the model’s geometry. The two options use zone calculation
methods to predict local effects.
If you do not need to see local effects in the radiant chamber, you may select the single zone
option. This option uses a one-gas-zone model to solve the radiant section. However, it does not
integrate radiant calculations with local process tubeside conditions, so you must define the entire
process tubeside.
How do I use the stack panel to build a stack?
The main stack panel controls what stack elements are in the stack. To add elements, double-
click the desired element in the list or select it and click Add New Stack Item. Adding stack
elements this way places new items at the bottom of the stack.
To insert new stack elements anywhere in the stack, click Insert New Stack Item.
1 Select an item in the Stack Items list.
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2 Select a new stack item from the Available Stack Items list.
3 Click Insert New Stack Item.
The new stack item is placed before (or on top of) the stack element you selected in Step 1.
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How do I specify tube sinks instead of tubes?
For some cases (such as waterwall boilers), you may want to model the heat load inside the
radiant section as a series of tube sinks rather than as a tube coil. To model tube sinks, select the
No tube geometry or process fluid option on the Box Heater panel.
Xfh will then combine all of the tube geometry panels into a single Tube Sink Definition panel.
You simply specify the radiative properties and the sink temperatures in every zone along each
wall.
If you select the No tube geometry or process fluid option, radiant calculations will not be
integrated with any process tubeside calculations.
How do I specify return bends for symmetric heater parts in a box heater?
If you model floor-fired box heaters with horizontal tubes, you may simplify the heater into one
heater section that is repeated along the floor. You specify the number of symmetric sections
repeated along the floor on the Burner Locations panel.
Then on the Tube Locations panel, indicate with the Inside Return Bend? check box if the return
bend is inside the box. If cases use more than one symmetric section, be careful when choosing
inside or outside return bends. Your choice can maximize the number of accurately modeled
symmetric sections.
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When you specify inside return bends, gaps to allow for return bends are modeled between the
ends of the tube and the edges of the box.
If you model a heater with only one symmetric section, these gaps are accurate. However, the
same is not true when you model multiple symmetric heater sections. Because the Xfh algorithm
uses symmetric sections, gaps are modeled where you may not intend them.
In the illustration above, a model of six symmetric sections includes twelve gaps when there
should be only two. To achieve a more accurate model of the heater, you need to specify outside
return bends so that the Xfh model will not model any gaps.
Although neither of these models is entirely accurate, the second one (with outside return bends)
provides a better approximation for this particular case.
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How do I open or import an FH case into Xfh?
The binary file format for Xfh is different from that of its predecessors (FH 2.0 and FH 3.0). If you
use the File/Open command in Xchanger Suite with an FH file, the case shows only physical
properties of the streams, not any geometry information.
To use an FH case, you must first import it into Xchanger Suite so that Xfh can set up the new file
format for the case.
To import an FH case
1 Select File/New in Xfh to create a new case.
Any case type works. No matter what case type you create, importing the old FH case will
select the right case type automatically.
2 Select File/Import Case…
3 In the resulting dialog box, select the file you want to import.
4 Click Open.
The FH case is now an Xfh case. Be sure to save the case before you close it.
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Fired Heater (Xfh) Online Help About This Version
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About This Version
Xfh 5.0 replaces all previous versions of FH. Xfh 5.0 is a significant modification over the previous version
(4.**). Some of the more significant modifications/enhancements to Xfh 5.0 include the following:
More than 10 tube types in the convection section do not cause the program to crash.
Convergence was improved for the duty matching option.
The film boiling check logic was improved so that film boiling will be predicted less often.
New features are indicated by ; all other listed items are updates to existing features.
Boiling Methods
Calculation Procedures
Data Input and Data Check
Graphical Interface
Miscellaneous
Program Outputs
Radiation Methods
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Boiling Methods
Version 5.0
Film boiling criteria The criteria for determining tubeside film boiling were
modified for fired heaters. HTRI methods contain both a flux
and a delta-T criterion for determination of film boiling.
Conceptually, the two checks should predict film boiling at
the same point.
Xfh 5.0 was modified as follows:
The delta-T criterion was removed.
The correlation used for determining critical heat
flux was developed using data with L/D ratios up to
1000. For the long pipe runs used in fired heaters,
the correlation in Xfh limits the maximum L/D to
1500.
These two changes should make the prediction of film boiling
in fired heaters slightly less conservative. (CR 231)
Calculation Procedures
Version 5.0
Back wall temperature
convergence for cylindrical
heaters
For some cylindrical heater cases, the back wall
temperatures were reported to be lower than the bulk
process temperatures, a situation which does not occur.
Program convergence was improved to enforce back wall
temperatures higher than bulk process temperatures. This
change had a negligible effect on the overall results.
This modification corrects HCPA item Xfh 4.0-30. (CR 3372)
Duty matching option for
cases in non-US units
The program was modified to set correctly the radiant duty
(used for duty matching) when a case is not set in US units.
This modification corrects HCPA item Xfh 4.0-28.
(CR 2520)
Number of direct interchange
area calculations required for
shock tube emissivity
Because the program uses an average gas extinction
coefficient to calculate shock duty, the number of iterations
when determining the total view factor was reduced by 2/3.
This modification reduces the runtime but does not affect the
results. (CR 2414)
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Unexpected program
termination of box heater
cases with more than 20 tubes
in single zone
Previously, when the number of tubes in a single zone
exceeded 20, Xfh issued an informative message and
continued the calculations. However, the program still
encountered an "array out of bounds" error when the number
of tubes exceeded 20 in a single zone.
Xfh now issues a fatal runtime message if you specify more
that 20 tubes in a single zone.
This modification corrects HCPA item Xfh 4.0-20. (CR 1916)
No convergence of duty
matching cases
Xfh now uses the correct convection bundle duties when
duty matching. This modification allows cases that set duty
matching against only some of the convection bundles.
This update corrects HCPA Xfh 4.0-10. (CR 2569)
Unnecessary convection-
radiant recycle loops
Xfh was modified to prevent unnecessary re-execution of the
radiant section. Prior to this modification, if the convection
section (e.g., for interconnected convection bundles)
required recycle loops but the convection and radiant
sections were not connected by a process stream, the
radiant section would re-execute unnecessarily every time
the convection section loop was executed. The results were
not affected, but the runtimes increased. (CR 2630)
Corrected box heater
incrementation
The program was modified so that it uses the correct
incrementation for cases with process passes that switch
orientation.
This modification corrects HCPA Xfh 4.0-25. (CR 3035)
Version 4.0 Service Pack 3
Using fuel oil grade input If your case contains a fuel oil and you have specified the
density of the oil using the Grade option, you must also
specify the higher heating value or the lower heating value.
This problem was caused by a data type mismatch in an
argument list. The data types were modified to be consistent.
This modification corrects HCPA item Xfh 4.0-19. (CR 2652)
Non-convergence message in
radiant section
A logic error in the calculation of the radiant wall
temperatures could lead to a convergence failure. This
problem has been corrected, allowing a number of cases
that exhibited a convergence failure message to converge
correctly.
This modification corrects HCPA item Xfh 4.0-11. (CR 2715)
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Message when flue gas
temperature is too high
If Xfh calculates an unrealistically high flue gas temperature
in the radiant section, the program cannot calculate the
shock tube emissivity. Previously, Xfh would stall.
The program has been modified to print a runtime
information message—"Xfh could not calculate an emissivity
because the flue gas temperature is too high. Please check
the flue gas opening. The flue gas temperature is
[temperature] R."
Under these conditions, the case typically fails to execute.
This modification corrects HCPA item Xfh 4.0-17. (CR 2571)
Modeling of side-to-side floor
or roof tubes
Xfh was modified to model correctly floor or roof tubes
between the left and right furnace walls. Prior to this
modification, Xfh modeled such tubes as front wall to back
wall, regardless of the orientation you select in the input.
This problem meant that
input geometry checks could incorrectly refuse
valid input if the Xfh algorithms determine that the
specified tubes would not fit in the radiant box
the flux distribution for the tubes would be modeled
incorrectly
(CR 2920)
Increased array size Several array sizes were increased to accommodate more
than 16 process passes in the radiant section. This
modification corrects HCPA Xfh 4.0-13. (CR 2921)
Version 4.0 Service Pack 2
Convergence failure in
convection bundles feeding
each other
This modification corrected a logic problem that could cause
a convergence failure if the convection section of the
process outlet from one convection bundle was the process
inlet of another convection bundle. The logic has been
corrected so that this configuration now converges properly.
(CR 2583)
Dynamic setting of gas space
execution order
This modification corrects a problem that occurred when the
user selects a gas space configuration with the flue gas
opening in a specific location and then locates the flue gas
opening in a different gas space. The calculation logic was
changed to dynamically set the flue gas space execution
order to deal with this issue and assure a proper flue gas
mass balance. (CR 2711)
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Convergence problem for no-
tubes cases
Xfh calculated some temperatures that it needed for
convergence only at the end of the run. Xfh now calculates
average, maximum, and minimum temperatures of the gas,
refractory, and sinks during the iteration sequence so that
no-tubes cases converge properly. This corrects HCPA item
Xfh 4.0-9. (CR 2596)
Box heater mass imbalance for
multiple gas spaces
Xfh was modified to prevent a flue gas mass imbalance
between gas spaces. This problem occurred when users
specified the flue gas exit in a different location than that
indicated in the gas space configuration. This corrects HCPA
item Xfh 4.0-1. (CR 302)
Version 4.0 Service Pack 1
Error message "Tubepass at
left not found"
If tube sizes used in a single box heater tubepass were very
different, Xfh would generate a fatal runtime error. This
problem has been corrected. (CR 2568)
This corrects HCPA Xfh 4.0-6.
Version 4.0
Order of gas space solution Xfh was modified to consider the location of the flue gas
opening when users specify the order in which the gas
spaces are solved. Previously, FH assumed that the flue gas
opening was in the location determined by the gas space
configuration ID. If the user picked an ID and then specified
the flue gas opening in a different location, the flue gas mass
balance would be incorrect. (CR 1244)
Stack Draft calculations Xfh now includes a calculation module that performs stack
draft calculations. The user defines the configuration of the
stack in the user interface, and the new module calculates
the pressure drop and draft for all piping elements in the
stack. (CR 48)
Modified calculation engines The calculation engines used in Xfh (FHDLL.dll and
acerate.dll) were modified to reference the new Xfh object
model instead of the one used in FH 2.0 and FH 3.0. (CR
1257)
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Memory leak when running
box heaters
Xfh allocates system memory as needed to execute a case.
When the program is closed, this memory is returned to the
operating system. A logic error caused the program to retain
some memory after a user exits the program. This problem
could cause system instability after a sufficient number of
Xfh runs. The memory leak was corrected. (CR 1604)
Increased message buffer for
single-zone firebox
The message buffer used to store runtime messages for the
single-zone firebox option was increased from 128 to 256
characters. (CR 1673)
Flue gas stream for new stack
model
The procedure to set the properties of the flue gas stream to
the convection section was modified to allow for the new
stack model. Changes were required in Xfh because the first
element in the stack may not be a convection bundle. (CR
1676)
Xace incrementation for Xfh
bundles
Xace was modified to place fluxes in the correct increments
for Xfh cases with arbor tubes. (CR 1769)
Chenoweth-Martin pressure
drop method
Xace may now use the Chenoweth-Martin two-phase
pressure drop method when calculating process pressure
drops in Xfh. The Chenoweth-Martin method uses the
Colebrooke-White friction factor, especially suitable for large
pipe pressure drops. Users may select the new Large Pipe
friction factor method on the Process Methods panel. (CR
1780)
Working single-zone model for
Option 0
The single-zone radiant model in Xfh contains four input
options (0 – 3). Options 1 – 3 are available via the graphical
interface. Prior to this correction, selecting Option 0 would
result in a crash. This option now functions correctly. (CR
1671)
Shock tube duty for box
heaters
We added a method to calculate the direct radiant heat
transfer from the firebox to the convection section for box
(cabin) heaters. To activate this option, input a guess for the
flue gas temperature and a distance to the first convection
section tuberow.
(CR 1402)
Correct convection flue gas
emissivity calculation
The call to the gas emissivity routine was modified to use the
flue gas temperature instead of the surface temperature,
correcting the calculation of the flue gas emissivity in the
convection section. The previous version overpredicted the
flue gas emissivity in the convection section. This
modification closes HCPA 3.0- 27. (CR 1993)
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Correct calculation of
liquid/solid fuel heating value
The calculation of fuel heating values from ultimate analysis
values was corrected. Although the original correlation had
accounted for the amount of inerts (ash + moisture), Xfh
incorrectly prorated the calculated value by this amount,
resulting in a value that was too low. The increase in heating
value after this modification is directly proportional to the
amount of inerts present in the fuel.
This modification affects only liquid/solid fuels for which only
the ultimate analysis is specified. This corrects HCPA item
FH 3.0-29. (CR 2191)
Modification of radiant wall
temperature calculation
In FH 2.0 and 3.0, the radiant wall temperature was
calculated based on the assumptions that the process fluid
was well mixed and the inside process fluid temperature was
the same at the front and back wall. Xfh now calculates the
inside process temperatures at the wall based on the front
and back wall fluxes. This change causes the predicted front
wall temperatures to be somewhat higher and the predicted
back wall temperatures to be lower. This modification
corrects HCPA FH 3.0-26. (CR 1786)
Liquid and fuel oil stream
calculation for combustion
In the combustion calculation, Xfh calculated the liquid fuel
compositions incorrectly when it removed the ash
component from the combustion stream. This error was
corrected, and the ash is no longer removed for liquid fuels.
However, even if they have identical compositions, liquid fuel
and fuel oil cases still behave differently because the higher
and lower heating values are calculated differently.
The lower heating value (LHV) for liquid fuels is calculated
as
LHV = HHV – 9472 (WFhydrogen + 0.1119
WFwater)
where WFhydrogen is the weight fraction of hydrogen and
WFwater is the weight fraction water.
For fuel oil, WFwater is not included:
LHV = HHV – 9472 (WFhydrogen)
(CR 2037)
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Box heater with two gas
spaces and a side flue gas
opening
Box heater gas space configuration ID = 12 is a two-gas-
space heater with a side flue gas opening in the second gas
space. Because the flue gas flow configuration for this
geometry was incorrect, the case failed to converge. The
logic was corrected so that the case now operates correctly.
(CR 2361)
Version 3.0 Service Pack 2
Unexpected crash with GMY
option
An error introduced in FH 3.0 Service Pack 1 caused FH to
crash when users selected the symmetric section (GMY)
option for box heaters. This problem has been corrected.
This corrects HCPA item FH 3.0-11. (CR 1575)
Shock tube duty The shock tube duty (the direct radiation transferred to the
shock tubes in a convection section) was stored internally in
the wrong units. This error has been corrected. Although the
unit assignment would not cause reporting of incorrect
results, it may have caused problems for anyone accessing
the value programmatically using the automation server. (CR
1401)
Multiple tube materials in
cylindrical heater
If the user specified multiple tube materials, the FH interface
was passing incorrect multiple tube material codes to the
calculation engine. This problem has been corrected. This
corrects HCPA item FH 3.0-12. (CR 1517)
Ash and moisture content
reversed in fuel specification
When a user specified a fuel by ultimate analysis, FH was
reversing the amounts of ash and moisture in the
combustion calculations. This has been corrected. This
corrects HCPA item FH 3.0-18. (CR 1554)
Unexpected crash with large
fuel rates
FH was modified to prevent a program crash when users
specify an exceedingly large fuel rate. (CR 1608)
Version 3.0 Service Pack 1
Fluxes on Firebox Tables for
box heaters
The link between the radiant and process calculations was
modified to correct a reversal of heat fluxes that occurred on
alternate tubes for box heaters. The overall results changed
very little (< 5%), but the average and maximum fluxes
reported on the Firebox Tables are reversed down the length
for alternate tubes. This corrects HCPA item FH 3.0-3. (CR
1328)
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Incorrect process flow rate for
symmetric gas space
configurations
For symmetrical gas space configurations 2, 4, 5, 8, and 9,
FH did not properly handle the process flow rate and
process duty, using twice as much in its calculations. FH
now divides by 2 the total flow rate or duty for gas space
configurations 2, 4, 5, 8, and 9. This corrects HCPA item FH
3.0-5. (CR 1264)
Inside return bends in box
heaters
FH was modified to properly account in process calculations
for the area of U-bends inside the box. Prior to this
modification, this area was not accounted for, and the total
process duty was slightly less than the total radiant duty.
This corrects HCPA item FH 3.0-7. (CR1358)
Wall temperature for U-tubes FH was modified to use a more reasonable initial
temperature estimate for the horizontal section of a U-tube.
FH was using a value of 0 °F for the wall temperature which
slowed convergence and could cause convergence failures.
(CR 763)
Iterations for duty
convergence of box heaters
When running cases with duty matching specified, FH
occasionally issued an error message, stating that the duty
failed to converge. FH allowed only five (5) heat duty
iterations, not enough for convergence.
FH has been modified to allow more heat duty iterations.
The number of allowed iterations was increased to 15. This
corrects HCPA item FH 3.0-8. (CR 1335)
Correct flux and wall
temperature exchange
between radiant and process
calculations
FH was modified to correctly transfer fluxes and wall
temperatures between the radiant and process calculations.
The modification involved considering the location of the
process inlet to determine how fluxes and wall temperatures
are distributed along the tube length.
Prior to this modification, FH was incorrectly using the
number of process tubes as the criterion for determining how
fluxes and temperatures were transferred. The overall
results changed very little as a result of this modification.
The effect was to flip the flux profiles on alternate tubes in
certain cases. This corrects HCPA item FH 3.0-9. (CR 1283)
Crash when API530 routine
fails to converge
FH was modified to prevent a crash that occurred when an
API530 utility routine failed to converge. (CR 1425)
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Properties for 800H and T410
tube materials
Some properties for 800H and T410 tube materials were
missing from the internal databank. When you selected
these materials in an API530 calculation, FH crashed. The
missing properties have been added. This corrects HCPA
item FH 3.0-10. (CR 1321)
Version 3.0
Buffer overflow with duty
convergence failure
The message buffer for duty convergence failure in
cylindrical heaters was too small. If this loop failed to
converge, FH would crash trying to issue the message. The
message buffer has been increased. (CR 1007)
Updated loss coefficient for U-
bends
At the Reynolds numbers typical of process fired heaters,
the loss coefficient used for tubeside pressure drop was very
conservative. An updated (lower) value was applied. In
radiant sections, the process pressure drop can be up to
40% lower with this change. (CR 1146)
Downflow boiling static head The tubeside pressure drop routines were modified to
consider static head pressure gains in downflow boiling. This
can significantly reduce the predicted pressure drop in
heaters with boiling in vertical tubes. (CR 1175)
Number of tube sections in
box heaters
FH was modified to allow users to define up to 30 different
tube sections in the PCL input. Previously, only two tube
sections were permitted. Note that the GUI still supports a
maximum of two sections per heater wall. (CR 1057)
Radiant convergence in box
heaters
The relaxation factor used when the tube wall temperatures
are converged was changed from 0.5 to 0.33. This range
permits a wider set of cases to converge. Additionally, the
logic was modified to force the wall temperature
convergence to perform at least 5 loops, thus preventing FH
from reporting convergence before the wall temperatures
have stabilized. (CR 794)
High wall temperatures in
cylindrical heaters
FH was modified to increase the stability of the wall
temperature convergence loop. Prior to this change, cases
with high tube wall temperatures (e.g., high fouling factor)
sometimes failed to converge. This modification resolves
HCPA 2.0-21. (CR 54)
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Tube fluxes for box heaters
fired at both ends
A modification was made to handle correctly the prediction
of tube fluxes for certain box heaters. When box heaters are
fired from both end walls, the heater is assumed to be
symmetric, and the predicted tube flux profile should be
symmetric as well. Before this modification, the process
calculations were made using the flux profile for half of the
heater over the entire length of the tube. Now the flux profile
properly reflects both halves of the heater. This modification
resolves HCPA FH 2.0-3. (CR 58)
Multiple fuels in box heaters The logic to calculate burner momentum was modified to
correct a potential dependency on the order in which
multiple fuels are specified. Prior to correction, the
calculated burner momentum (and flue gas circulation) was
incorrect if the first fuel did not have a diluent stream
specified. This modification resolves HCPA FH 2.0-27. (CR
539)
Maximum number of radiant
loops
FH solves the radiant section by iterating between the
process- and radiant-side calculations. The maximum
number of iteration loops was increased from 10 to 15.
Several cases were identified that required 9 or 10 loops to
converge. The increase is intended to prevent unnecessary
convergence failures being reported. (CR 505)
Correct radiant wall
temperature calculation
A logic error caused FH to incorrectly include the wall and
fouling resistance in the calculation of the inside wall
temperature for cases with specified flux (e.g., FH radiant
bundles). This overestimated the inside wall temperature
and thus overestimated the outside wall temperature as well.
This modification resolves HCPA FH 2.0-30. (CR 534)
Runtime message for zero
burners
The calculation engine was modified to provide a fatal
runtime message if zero burners are specified in a gas
space (box heaters). This configuration is invalid. This
modification resolves HCPA FH 2.0-31. (CR 509)
Correct unheated tube lengths
in convection sections
FH was modified to correctly specify the unheated tube
lengths entered by the user for a convection section. Prior to
this modification, the unheated lengths were incorrectly
included in the area between the tubesheets, producing
incorrect Reynolds and mass velocity values. This
modification resolves HCPA FH 2.0-35. (CR 525, 526)
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Water content for preheated
air
FH was modified to calculate water content (if relative
humidity is specified) based on an air temperature of 15.56
°C (60 °F) if the specified air temperature is greater than
65.56 °C (150 °F). Prior to this modification, FH used the
specified air temperature, resulting in unreasonable amounts
of water for preheated air streams. This modification
resolves HCPA FH 2.0-1. (CR 56)
Crash prevention when wall
temperatures diverge
If an extremely large fouling factor is specified for the
process tubes, the wall temperature convergence loop can
diverge and generate unreasonable temperatures that cause
FH to crash. This modification checks for this condition,
issues a fatal runtime message, and stops the calculations
to prevent a crash. (CR 616)
Back wall temperature
calculation in cylindrical
heaters
The logic used to calculate the back tube wall temperature in
cylindrical heaters was modified. The previous program
version used an empirical equation based on the local
process and gas temperatures to estimate the back wall
temperature. The new method uses the local back wall flux
calculated by the zoning method. FH uses the flux and
various thermal resistances (e.g., fouling and wall) to
calculate the temperature rise above the inside film
temperature. (CR 567)
Version 2.0 Service Pack 2
Double tuberows between gas
spaces in a box heater
In a box heater, FH automatically set the tube sharing factor
to 0.5 (fired from both sides) whenever a tuberow was
between two gas spaces. The setting worked well for single
tuberows but caused double tuberows to be modeled
incorrectly, with a tube flux too high.
FH has been modified to set the tube sharing factor to 0.5
only when the user indicates that the tuberows are shared.
This resolves HCPA item FH 2.0-16. (CR 255)
Location of flue gas opening The logic that checks the specified size and location of the
flue gas opening for single cell box heaters was modified.
For box heaters with a top opening, FH was incorrectly
checking the location against the box height instead of the
box width. It also prevented the opening being to the right of
the box centerline. For box heaters with a side opening, the
check was correct, but the message indicating an invalid
opening location referred to the box width rather than the
box height. All of these issues have been corrected. This
resolves HCPA item FH 2.0-18. (CR 367)
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Modeling both halves of
double-celled box heaters
The logic for setting up double-celled box heaters was
modified to model both halves of the firebox. FH previously
modeled only the gas spaces in one-half of the firebox. This
resolves HCPA item FH 2.0-19. (CR 256)
Fuel composition on API560
specification sheet
FH was modified to print the correct fuel composition on
Page 2 of the API 560 Specification Sheet. Previously, the
list of component names was incorrect. This resolves HCPA
item FH 2.0-20. (CR 347)
Flue gas flow in box heaters
with three gas spaces and flue
gas opening on one end
The calculation engine was modified to correct the
calculation of flue gas flow between gas spaces. The
engine incorrectly balanced the flow of flue gas for box
heaters with three gas spaces and the flue gas opening in
Gas Space 1 or 3. This resolves HCPA FH 2.0-22. (CR
362)
Calculating heat transfer
coefficient in API530 module
FH was modified to properly send the bulk fluid temperature
to the FH calculation engine when using the Inside Heat
Transfer Coefficient option in the API530 module. Without
this modification, the FH input would be incorrect, and the
API530 calculations would fail and issue a message. This
resolves HCPA FH 2.0-23. (CR 441)
Calculating tube dimensions
in API530 module
The FH GUI allows specification of tube outside diameter,
inside diameter, and wall thickness. To prevent inconsistent
specifications, FH disables the wall thickness field if the
tube inside diameter is specified and vice versa. However,
FH was not calculating the value for the disabled field.
Some calculations required wall thickness while others
required inside diameter, so all values must be set.
This modification ensures that all tube geometry variables
are calculated regardless of how the input was specified.
This modification resolves HCPA FH 2.0-23. (CR 438)
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Version 2.0 Service Pack 1
Box heater run hangs while
running process calculations
in radiant section
When calculating the firebox, FH iterates between the flue-
gas flux calculations and the process-side calculations as
displayed in the run log. If the radiant-side calculations fail
to converge, the FH engine does not correctly write the
calculated local flux values, causing the process-side
calculations to "hang."
The FH engine has been modified to correctly report a
failure condition. The program will now stop the calculations
and report an error message. This resolves HCPA item FH
2.0-7. (CR 91)
Large numbers of tubes on a
box heater wall
FH 2.0 assigns tubes in the tube coil to zones within the
heater. Depending upon the tube orientation and the wall
surface (e.g., side wall or end wall), tubes are assigned to
either 3 or 4 zones. FH has a maximum of 14 tubes in a
single zone. For example, 56 equally spaced tubes would
contain 14 tubes per zone for 4 zones.
The FH calculation engine has been modified to allow up to
20 tubes in a single zone. This resolves HCPA item FH 2.0-
2. (CR 100)
Limit on tubes per pass in a
box heater
FH 2.0 has a limit of 20 tubes per pass in a box heater.
The FH calculation engine was modified to increase this
limit to 100 tubes. This resolves HCPA item FH 2.0-9. (CR
111)
Warning messages for full
insulation specification
When you select the full insulation specification option, FH
checks the user-specified input in several ways.
Specifically, FH checks for a minimum insulation thickness
of 38.1 mm (1.5 in.) and for specified values for the ambient
air and outer casing temperatures. Both of these messages
refer to internal Texaco standards.
The reference to internal standards has been removed from
both messages. Additionally, the check for specific ambient
air and outer casing temperatures was modified so that a
warning message appears only if the specified outer casing
temperature exceeds 93.3 °C (200 °F). This resolves HCPA
item FH 2.0-10. (CR 90)
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Service Pack level on report
headers
FH 2.0 displays the Service Pack level installed immediately
following the program version number. This information also
appears in report headers for both the GUI spreadsheet-
style reports and the DOS-based reports. (CR 161)
Version 2.0
FH Calculation Engine Modifications
Shock tube radiation For cylindrical heaters, FH calculates the amount of direct
radiation heat transfer between the firebox and the first few
rows of the convection section.
External wall temperatures The calculation engine reads local wall temperatures on an
increment-by-increment basis as calculated using Xace
methods.
NOx at 3% O2 FH now calculates and reports the conversion factor to
convert the NOx concentration from the calculated percent
oxygen in the flue gas to a standard 3% oxygen
concentration.
Maximum flux in box heaters FH calculates a local circumferential maximum tube flux
based on the API 530 methods. Previously, the software
calculated only an average flux at each point on the tube.
Warning message
consolidation
Calculation engine messages are consolidated in a single
location, allowing the software to report all messages from
both the radiant and convective calculations in a single set of
message reports.
Convective Section Method Modifications
ESCOA methods The ESCOA methods were implemented for use in the flue-
gas side heat transfer calculations in convection sections.
Gray gas radiation The software now calculates a radiation heat transfer
coefficient on the flue-gas side in convection sections. It
calculates the emissivity of the gas based on the amount of
gray gases present.
API 530 heat transfer methods The API 530 heat transfer methods were implemented as an
optional heat transfer method for the firebox calculations.
The default remains HTRI methods.
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Variable tube lengths and
orientation
To handle box heater tube coil geometries, the incremental
engine was enhanced to allow within the same bundle
different tube lengths
different tube orientations (e.g., horizontal or vertical)
Variable incrementation To match the zoning used by the FH calculation engine, the
incremental engine was enhanced to allow a varying number
of increments along the tube length.
Variable wall clearance and
tubes/row
To increase flexibility convection bundle specification, the
software was enhanced to allow within the same bundle
multiple left wall clearances
different numbers of tubes/row
Tube emissivity input For calculation of gray gas radiation heat transfer, you can
now specify tube emissivity.
Min/max fin tip temperatures The software calculates the minimum and maximum fin tip
temperatures on a row-by-row basis.
Setting loss A setting loss method was implemented for specification in
convection bundles.
Active return bends The heat transfer calculations were modified to allow
inclusion of return bends as effective heat transfer surface
area.
Flux specification The Xace calculation procedures were modified to solve only
the tubeside heat transfer and pressure drop for use in the
radiant process calculations. The outside calculations are
fixed by a local heat flux specification. In this type of run, the
Xace methods are used to calculate the local outside wall
temperatures and return the values to the FH engine for use
in the radiant side calculations.
API 530 heat transfer
coefficient
The procedure to calculate the process heat transfer
coefficient uses a Newton-Rhapson method to calculate the
process fluid temperature at the tube wall. If two successive
iterations produce the same change in estimated
temperature, FH would divide the result by zero, and the
iteration would fail. If this happens, FH has been modified to
use an arithmetic average temperature that continues the
iteration and successfully converges the desired
temperature.
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Small soot extinction
coefficients
As part of the Hottel zoning method, FH calculates quantities
called direct interchange areas. These can be considered
radiation view factors between zones in the firebox.
Theoretically, these exchanger areas must add up to the
total surface area. To ensure that the sums are correct, FH
contains correction logic modified to correct a program
failure that occurred when small soot extinction coefficients
were specified in cylindrical heaters.
Correct Y-multiplier option The calculation engine contains an option to model large box
heaters (those with more than six burners) by slicing the box
heater into multiple symmetric slices. The previous version
of FH used an incorrect flame length calculation.
High temperature gas
properties
To be suitable for a convection section, the vapor physical
properties of all components that can exist in the flue gas
were extended to higher temperatures.
API 530 metal properties The HTRI metal properties databank was enhanced in two
ways.
Additional metals were added to the internal databank to
cover all materials referenced in the API 530 standard.
The thermal conductivity of all API 530 metals was
extended to higher temperatures.
Data Input and Data Check
Version 5.0
PCL generation for gas
oxidants with specified excess
oxidant
The program was modified to correctly specify 1.0 lb/hr for
the mass flow of the oxidant stream if the oxidant is a non-air
gas. This change allows the program to calculate the oxidant
flow rate that achieves the desired amount of excess oxidant
in the flue gas.
This modification corrects HCPA item Xfh 4.0-26. (CR 3116)
Version 4.0 Service Pack 3
Warning message that oxidant
contains no oxygen
If you do not specify any oxygen in the oxidant stream, the
program now issues a fatal runtime message. Prior to
correction, specifying no oxygen would cause the case to
hang. (CR 2690)
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Induced flow plane height in
cylindrical heater cases
If the half-jet angle is too narrow, the flue gas flow field will
extend beyond the height of the heater. An array-out-of-
bounds failure will occur, and Xfh will stop running the case.
The program was modified so that the height where the
plane of induced flow starts can be greater than the height of
the heater. If this situation occurs, Xfh sets the induced flow
plane height equal to the heater height, and issues a
warning message. This modification corrects HCPA item Xfh
4.0-18. (CR 2746)
Data checks for single-phase
fluids
Xfh 4.0 Service Pack 1 relaxed restrictions for some data
checks for single-phase fluids so that heat release curves
over a broad pressure range would be accepted as valid.
However, this change sometimes allows invalid input. If you
specify a single-phase fluid in the process conditions and a
two-phase heat release curve at the inlet conditions, Xfh
accepts the input as valid but the case fails to converge.
The original data checks were restored and modified to
require that the check fail on all pressure profiles before Xfh
issues a fatal data check message. Because fired heaters
operate over a wide process pressure range, typical input
contains pressure profiles over a wide pressure range, and
all profiles may not be consistent with the specified process
conditions. This modification allows such cases to run unless
all profiles are inconsistent.
This update corrects HCPA Xfh 4.0-7. (CR 2629)
Version 4.0 Service Pack 1
Physical property data checks Several physical property input data checks were removed
for fired heaters. Due to the broad operating pressure range
of fired heaters, these input checks were overly restrictive
and prevented valid cases from running. (CR 2578)
Version 3.0
Save as 2.0 Option An option to save in FH 2.0 format was implemented. FH 3.0
can save .HTRI files in a format that FH 2.0 users can read.
(CR 531)
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Zero burners in a gas space The FH interface was modified to prevent users from
specifying zero burners in a gas space of a box heater. Prior
to this modification, FH checked only if the total number of
burners in all gas spaces were greater than zero. Since FH
can not handle gas spaces with zero burners, this
modification was required. (CR 513)
Crashing API530 single-phase
cases
The input conversion .dll that converts the FH GUI
information into PCL format included checks to skip the
printing of liquid or vapor properties if they were not present.
These checks were modified so that a blank line is printed,
making single-phase cases run correctly. This modification
resolves HCPA FH 2.0-37. (CR 617)
Incorrect data check for return
bends inside box heater
For box heater cases in which not all of the return bends are
either inside or outside the firebox, an incorrect data check
message appears, indicating that DY for the side with return
bends outside the box is not large enough for the return
bend to fit inside the box. This modification resolves HCPA
FH 2.0-38. (CR 652)
Validating data for API530
Tube Geometry
New data validation logic has been added for API530 tube
dimensions on the Tube Dimensions and Metallurgy panel.
FH now checks that a tube outside diameter is always
specified and that outside diameter, inside diameter, and
wall thickness (if all specified) use consistent values. If either
of these checks fails, an information dialog box displays. (CR
449)
External Interfaces
Version 5.0
Box heater cases run from
user applications
A problem was corrected that caused the Xfh calculation
engine to fail if run from a user-written Visual Basic
application (e.g., an Excel spreadsheet). The problem
occurred only with box heater cases. (CR2734)
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Graphical Interface
Version 5.0
Tube length for cylindrical
heaters
The specified tube length used in the radiant section of
cylindrical heaters is the straight tube length with no
modification for U-bend length. The misleading label
"Effective length" for the input field was changed to "Straight
length." (CR 3321)
Floor firing for arbor tube
configurations
The engine does not model floor firing for gas space
configurations (box IDs) 26 and 27 (arbor/U-tubes). The
option to allow floor firing for arbor/U-tube configurations was
removed from the interface.
This modification corrects HCPA item Xfh 4.0-29. (CR 3378)
Run Log text The Run Log was modified to indicate the radiant pass
number that the program is calculating. Specifically, log text
changed from "Xace process conditions" to "Radiant process
pass (pass number)." (CR 3332)
Increased number of tubes
and process passes allowed
for box heaters
The program has increased the limits applied to box heaters
for
the number of tubes allowed in the radiant section, from
200 to 1000
the number of tubes for U-tube/arbor tube cases, from 36
to 166
the number of allowed process passes, from 36 to 100
(CR 172)
More than 10 defined tube
types
The program logic was modified to correctly handle more
than 10 defined tube types. Although an individual bundle
can use no more than 9 types, you can define more than 9
active types for multiple convection bundles. This
discrepancy caused such cases to crash when run.
A change in the program logic means that this situation no
longer causes a problem. This modification corrects HCPA
item Xfh 4.0-14. (CR 3006)
Clarification of convection
bundles in stack
To clarify that connection bundles are part of a defined
stack, labels in the program interface were changed from
Stack to Convection/stack. (CR 2850)
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HtriView in Tools menu By selecting HtriView from the Tools menu, you can launch
the HTRI binary file viewer, HtriView, which opens the
currently selected case. (CR 2407)
Typo on Combustion panel A drop-down list on the Combustion panel specifies options
for generating the combustion flue gas, but the input field
was incorrectly labeled "Fuel” instead of “Flue.” This typo
has been corrected. (CR 3380)
Version 4.0 Service Pack 1
U-tubes with firing from both
ends
The Xfh interface issues a warning message if you attempt
to specify U-tubes and firing from both end-walls. The
calculation engine does not allow this configuration; instead,
you must model it using symmetry. (CR 2421)
User-defined tube materials for
Tube Life Evaluation
You can now specify a user-defined tube material for an
API530 case running only the tube life evaluation option.
(CR 2403)
This corrects HCPA Xfh 4.0-2.
Version 4.0
Xfh in HTRI Xchanger Suite The FH GUI was re-designed and implemented as the Xfh
module in HTRI Xchanger Suite. (CR 835)
Units for Material Constant
with user-defined materials
The API 530 module contains a panel to define material
constants for user-defined materials. The material constant
A per Table 2 of the API 530 standard was incorrectly
labeled with temperature units. This label has been replaced
with the proper pressure units. This corrects HCPA FH 3.0-
21. (CR 1703)
Corrected online help
reference for PCL PROCGAS
keyword
The online help section describing the PCL keyword
PROCGAS incorrectly referred to the MUBL sub-keyword.
This reference was changed to the correct sub-keyword of
MUBV. (CR 1670)
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Removed non-symmetric gas
configurations
Several of the box heater gas space configurations were
removed from the program. IDs 4 and 8 were removed from
the single-cell top opening type, and IDs 16 and 18 were
removed from the single-cell double roof opening type.
These types contain a single central gas space that cannot
be modeled using symmetry when the process flow path is
included. The current interface cannot support them. (CR
1767)
Additional sample description
in online help
A description of an additional test case (Standard Case 7)
was added to the Xfh online help. (CR 1254)
No Tubes option available The Xfh calculation engine now contains a no-tubes option
for the box heater so that users can run cases for which the
tube geometry cannot be specified on the current input
panels. For example, Xfh cannot currently handle the tube
geometry and total tube count for package boilers. A new
input panel for sink definition and a new output report (No
Tube Flux Monitor) were created for this option. (CR 1727)
Single-zone heater option The graphical interface now supports a radiant section using
a single zone. Additional input panels and output reports
were created for this option. (CR 1742)
More than two sections
allowed in tube geometry
FH was limited to no more than two different tube
geometries on a single wall in a box heater. This limit has
been increased in Xfh to six different tube geometries. (CR
51)
New graphical interface for Xfh The fired heater program (Xfh) is now a part of HTRI
Xchanger Suite. The interface was modified to be consistent
and compatible with other HTRI Xchanger Suite modules.
(CR 1263)
Point-and-click process flow
path specification
Xfh 4.0 includes a graphical point-and-click mechanism to
allow flexible and intuitive specification of the process flow
path through the radiant tubes in a box heater. (CR 28)
Tube location display in box
heaters
The new Xfh interface generates a 3D representation of the
box heater that indicates the location of all radiant tubes in
the radiant section. (CR 29)
Burner location display A new 3D representation of the box heater displays the
specified location of all burners. (CR 30)
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Corbel specification The presence or absence of corbels (bundle bypass
blockage) can now be specified for bundles in the convection
section. (CR 304)
Version 3.0 Service Pack 3
FH 3.0 and Xfh 4.0 run
simultaneously
The FH 3 graphical interface was modified to allow it to run
independently of Xfh 4.0 when the latter is installed on a PC
loaded with FH 3.0. (CR 1815)
Shared tube coils with more
than one tube may not
converge
The interface was modified to correctly handle shared tube
coils containing more than one tube section (geometry).
Prior to this correction, such cases typically failed to
converge. This corrects HCPA item FH 3.0-24. (CR 1887)
Version 3.0 Service Pack 2
Incorrect transfer of SI/MKH
units for high-fin tube
selection
This service pack corrects a unit conversion problem with
high-fin tube geometry specified from the internal databank.
If users selected SI or MKH units, FH incorrectly transferred
the fin height and thickness. This has been corrected. This
corrects HCPA item FH 3.0-13. (CR 1451)
Incorrect tube material thermal
conductivity
Instead of a user-specified tube material thermal
conductivity, FH was using the value from the internal
databank for the tube material selected. This has been
corrected. This corrects HCPA item FH 3.0-14. (CR 1516)
Specified average flux for
cylindrical heaters not used
FH was corrected to respect the average flux specified on
the Duty Requirement panel. Setting an average flux also
sets the equivalent total duty, and vice-versa. This corrects
HCPA item FH 3.0-15. (CR 1518)
Incorrect material selection for
cylindrical heaters
To correct a problem checking the selected material, the
variable containing the specified tube material was trimmed
of any leading/trailing blanks. Prior to this correction, the
string did not match any of the materials and instead always
indicated the default (medium carbon steel) material. This
corrects HCPA item FH 3.0-16. (CR 1524)
Typographical error in label for
Oxidant Flow Rate fields
Two oxidant flow rate fields incorrectly referred to %O2 in
the "fuel" gas. This was corrected to refer to %O2 in the
"flue" gas. This corrects HCPA item FH 3.0-17. (CR 1553)
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Correct user-defined materials
in cylindrical heaters
FH was modified to allow user-defined tube materials
(OTHER selection) in cylindrical heaters. Prior to this
modification, selecting a user-defined material would cause
the run to fail. This corrects HCPA item FH 3.0-19. (CR
1519)
Gas Space Configuration ID =
2 incorrectly handling gas
space width
For a gas space configuration ID = 2, a box heater contains
two identical gas spaces. However, instead of using a gas
space width one-half of the total heater width, FH was using
the entire heater width as the gas space width. Other IDs
that employ symmetry behave correctly.
FH was modified to calculate the gas space width by dividing
by 2 the total heater width entered on the Input Dimensions
for Box Heater panel. This corrects HCPA item FH 3.0-20.
(CR 1431)
Corrected API530 process
conditions
FH 3.0 Service Pack 2 corrects several problems with the
way the tube operating conditions pass to the calculation
engine for API530 tube design calculations:
If you specified multiple liquid viscosities at several
temperatures, FH sent only the first viscosity point to the
calculation engine, potentially resulting in an incorrect
viscosity in the heat transfer calculations.
If you specified the metal wall temperature, FH passed
extraneous fluid property information that was not used.
This problem did not cause any error in the calculations.
If you set the maximum elastic design pressure option to
CALC, FH incorrectly transferred the process
information, resulting in failure of the API530 calculations
and issuance of a warning message.
If you set the End of Run metal temperature to use the
same value as Start of Run, FH sent preceding End of
Run information (if any) to the calculation engine,
causing an incorrect ending temperature in the
calculations.
(CR 1596)
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Version 3.0 Service Pack 1
Burners displayed incorrectly
for cylindrical heaters
The scaled graphic for cylindrical heaters displayed burner
diameters that were twice as large as they should be. FH
was incorrectly using the diameter instead of the radius in
drawing the burner circles. This has been corrected. This
corrects HCPA item FH 3.0-1. (CR 1294)
Bypass film boiling check By default, FH always checks for the presence of film boiling.
If you want to see the results without film boiling, check this
box on the Radiant Section Process Conditions panel to
bypass the check for film boiling. (CR 540)
Comma as decimal digit If you use a comma (instead of a period) as the decimal
digit, the graphical interface was incorrectly saving some
values on the Process Condition and Convection Geometry
panels. This has been corrected. This corrects HCPA item
FH 3.0-4. (CR 1374)
Extended help for specifying
symmetric gas spaces
Online help information for specifying the geometry of
symmetric gas spaces in box heaters was extended. (CR
1450)
Corrected cylindrical heater
drawing title bar
The spelling of "cylindrical" was corrected on the title bar of
the interface graphic that displayed the scaled drawing of the
cylindrical heater geometry. (CR 1443)
Navigation tree for box heater
output reports
The navigation tree for box heater output reports contains a
series of three reports for each gas space. To access these
gas-space-specific reports, you clicked the plus (+) sign next
to the gas space number in the report navigation tree.
However, once the tree expanded to reveal the individual
reports, you could not collapse it. You can now expand and
collapse the gas space report list in the report navigation
tree. (CR 1245)
Service Pack level and release
date
The About dialog box (accessed from the Help menu) was
updated to indicate SP1 (for Service Pack 1). The release
date information was also updated. (CR 1315)
Version 3.0
Explanatory note for Input
Dimensions for Box Heaters
panel
An explanatory note was added to the Input Dimensions for
Box Heaters panel. The note states that all specified
dimensions are inside dimensions, that is, from refractory
surface to refractory surface. (CR 992)
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Tube orientation for cylindrical
heater cases
The FH GUI was modified to set the correct tube orientation
for cylindrical heater cases in the HTRI automation server.
(CR 964)
Disabled menu items when
backup files are loaded
The FH interface creates a Backup.HTRI file to prevent total
data loss if the interface crashes. A logic error caused the
Save commands in the File menu to become disabled if FH
loaded this backup when restarted. This problem has been
corrected. This resolves HCPA FH 2.0-40. (CR 693)
Tube material properties for
stainless 410 (T410)
The FH interface was modified to set the proper material
code when users select stainless 410 (T410). Previously, FH
selected properties for stainless 316. This resolves HCPA
FH 2.0-25. (CR 517)
Reducing the number of
convection process fluids
The FH interface (GUI) was modified to allow users to
reduce the number of convection section process fluids.
Prior to this modification, the interface would hang in an
infinite loop when the number of convection process fluids
was reduced. This modification resolves HCPA FH 2.0-24.
(CR 495)
Initial wall temperature
estimate for radiant section
The loop to converge the firebox wall temperature requires
an initial estimate for the wall temperatures. The box heater
and cylindrical heater modules were modified to use
consistent methods for estimating the wall temperatures
based on process temperatures. (CR 432)
More than 9 tube sections in
convection section
The FH interface was modified to properly set up convection
sections with more than 9 tube sections. Prior to this
correction, FH would crash when running convection
sections with more than 9 tube sections. This modification
resolves HCPA FH 2.0-28. (CR 474)
Location of default file name The FH interface was modified to correctly handle the
presence or absence of a closing "\" on the WorkingDir entry
in the Windows registry. The WorkingDir entry sets the
default location to read/write data files. Prior to this
modification, FH always added a closing "\" to the value set
in WorkingDir. If the value already contained a closing "\",
FH would generate an illegal pathname (e.g.,
C:\HTRI\DataFiles\\New.HTRI).
This became an issue only if you attempted to save to this
default name. (CR 489)
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Tube Life Evaluation option The FH interface was modified to save the Tube Life
Evaluation option setting. Prior to this modification, if you
selected "Past Damage Only" or "Future Damage Only" on
the Tube Life Evaluation panel (API530 module) for a case,
FH would not save the Tube Life Evaluation option selection
on the main API530 input panel. (CR 471)
Burner diameter as specified
in cylindrical heater drawing
The FH interface correctly scales the burner diameters
based on the user-specified value. Prior to this modification,
the drawing displayed burners at 25% of the burner circle
diameter regardless of the input diameter. This modification
affects only the displayed drawing. The input passed to the
calculation engine was correct. This modification resolves
HCPA FH 2.0-32. (CR 494)
Crash on displaying Gas
Space Configuration panel
The interface was modified to prevent a crash under the
following circumstances:
User saves case immediately after selecting a box heater
type other than single-cell top-opening
User loads the saved case and jumps to the Gas Space
Configuration panel
FH now correctly sets the default configuration information.
(CR 284)
Failure to converge of
cylindrical heater cases with
duty matching
The FH GUI was corrected so that unnecessary API530
records that cause this problem are not written to the PCL
file. This modification resolves HCPA FH 2.0-36. (CR 595)
Specified duties in combustion
calculations
The Combustion Diagram report was modified to display
specified (or calculated) duties and losses for a single fuel.
Prior to this modification, this information was displayed for
double-fuel but not single-fuel cases. (CR 452)
Version 2.0 Service Pack 2
Formatting problems on
output reports
The word Calculated was truncated on the Input Reprint
report for API530 runs, and the word Characterization was
misspelled on the Stream Properties report. Both of these
issues have been corrected. (CR 232)
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Check for proper gas space
widths
For box heaters with multiple gas spaces, the GUI verifies
that the sum of the gas space widths equals the total box
heater width. Because the tolerance was set as a low
absolute value, specifying acceptable gas widths was
sometimes very difficult. Changing units could also cause
the software not to accept values that were valid in another
unit set.
The tolerance was changed from an absolute tolerance of
0.0001 (which was independent of unit set) to a relative
tolerance of 0.0005. This resolves HCPA item FH 2.0-14.
(CR 192, 251)
Burner locations for double-
cell box heaters
Internally, the FH interface used an incorrect width for each
side of a double-cell box heater, preventing the user from
properly specifying multiple gas spaces on each side of a
double-cell heater. In addition, it set the valid burner
locations incorrectly, possibly keeping the user from
specifying burners in the desired locations.
This problem has been corrected. This resolves HCPA item
FH 2.0-15. (CR 218)
Zone numbering on cylindrical
heater firebox tables report
The number of zones (1 – 10) on the Firebox Tables report
was modified to be consistent with the zone numbers on the
Heater Temp Profile report. FH numbers zones from the
bottom (1) to the top (10) of the heater. The zone numbers
on the Firebox Tables report now follow this convention.
(CR 39)
Crash when using Previous
button
The GUI was modified to prevent a crash when user clicks
the Previous button in certain circumstances. If, in a new
case, the user skipped multiple input panels by jumping
directly to a panel using the Previous button, the software
would crash because some variables had not been
initialized. This has been corrected. (CR 171)
Display number of tubepasses
for U- and arbor tubes
The Output Summary report was modified to display the
number of tubepasses for U- and arbor tubes. Previously,
this field was blank. This resolves HCPA item FH 2.0-13.
(CR 187)
Duty matching for box heater The FH interface was modified to allow duty matching to be
turned off for box heaters. Prior to this change, duty
matching could not be disabled once it had been turned on.
This resolves HCPA item FH 2.0-17. (CR 211)
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SP2 in report headers The report headers were modified to indicate SP2 (Service
Pack 2). (CR 401)
Service pack level in About
dialog box
The About dialog box (displayed from the About item on the
Help menu) was updated to indicate Service Pack 2. (CR
402)
Data check for maximum flux In the Tube Design panel in the API530 module, you select
either to specify the tube maximum flux or for FH to
calculate it. If you requested to specify this value, FH did
not check to see that you actually entered a value. A
warning message was added so that FH now requests a
value when you attempt to leave the panel. (CR 437)
Tube dimension specification
for API530 tube thickness
design
The FH GUI was modified to prevent a crash when the user
tried to display the Maximum Local Heat Flux panel and had
not specified an inside diameter on the Tube Dimensions
and Metallurgy panel. (CR 447)
TEMA fouling factor in API530
module
The FH GUI was modified to set the TEMA fouling factor to
zero (0) if the user erases the default value of zero in the
data input field. (CR 448)
Data validation for API530
tube geometry
New data validation logic was added for API530 tube
dimensions on the Tube Dimensions and Metallurgy panel.
Specifically, FH now checks that a tube outside diameter is
always specified, and that outside diameter, inside
diameter, and wall thickness (if all specified) use consistent
values. If either of these checks fails, an information dialog
box is displayed. (CR 449)
Version 2.0 Service Pack 1
Surface area for cylindrical
heaters
FH 2.0 reports a radiant tube surface area on the Duty
Requirement panel for cylindrical heaters. The value does
not always agree with the surface area reported in the
output reports. When different, the value reported in the
interface was incorrect.
The interface code was modified to correct this problem.
This resolves HCPA item FH 2.0-4. (CR 12)
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Radiant tube locations in box
heaters
The Tube Section Data panel specifies the location and
number of tubes in the radiant coil for a box heater. The
parameters DX, DY, and DZ specify the distance from the
end of the tube to the heater wall in each coordinate axis. In
some cases (for example, when tubes are shared between
gas spaces), some of these values will be zero. The current
grid configuration allows entry of zero values but displays a
blank field. If you do not specify a value of zero for these
fields, FH may generate an error message when you exit
the panel.
The interface has been modified to correctly display zero
values for these fields. This resolves HCPA item FH 2.0-5.
(CR 19)
Flue gas fouling factors in
firebox
Specifying the flue-gas fouling factor in the radiant section
of a fired heater had no effect.
The interface has been modified to correctly pass the
specified fouling factor to the calculation engine. This
resolves HCPA item FH 2.0-6. (CR 57)
Subscript range error when
displaying reports
After running a box heater case, FH may report a subscript
range error when trying to display the reports. This most
commonly occurred with large numbers of tubes on a box
heater wall.
The array size was increased to prevent this error. (CR 102)
Warning dialogs when
displaying message reports
When displaying the Data Check or Runtime Message
reports, FH may generate one or more warning messages,
indicating that a sheet name is already in use.
The FH interface was modified to always generate unique
worksheet names. This resolves HCPA item FH 2.0-8. (CR
117)
Increased flow rate display Although FH would use flow rates above 6 digits (e.g.,
999,999) as entered for calculations, the FH interface would
display them as .
The FH interface has been modified to display correctly flow
rates that use up to 7 digits (e.g., 9,999,999). (CR 110)
Service Pack level in About
dialog box
The About dialog box, accessed through the About FH
command in the Help menu, now indicates the Service
Pack level immediately after the program version number.
The release date is also updated. (CR 168)
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Duplicate insulation layers in
box heaters
The full insulation option for box heaters allows you to
indicate that the left and right side walls have identical
refractory and that the front and back walls have identical
refractory. If you use this option and specify multiple
materials on the left and front sides, FH copes only the first
material layer to the right and back sides.
This problem has been corrected and resolves HCPA item
FH 2.0-11. (CR 90)
Loss label setting for floor-
fired heaters
The wall labels for setting losses on the Gas Space Energy
Balance report are intended for end-wall fired box heaters.
If you run a floor-fired heater, FH does not label some walls
properly.
Both DOS-based and GUI spreadsheet reports have been
modified to display a set of labels to use with a floor-fired
box heater. This resolves HCPA item FH 2.0-12. (CR 177)
Version 2.0
.HTRI file implementation FH now saves cases using the .HTRI file format. The input
now contains values needed for both the FH and Xace
calculation methods. The .HTRI format stores all output
results, which means you don’t have to re-run a case to
display output reports once a file is loaded. FH 2.0 still
supports Input files from previous versions of FH (*.FH).
Radiant/convection
convergence methods
Algorithms were implemented to converge the interaction
between the radiant and convection sections. The flue gas
and convection process streams set up a recycle between
the radiant and convection sections. The algorithm iterates
until these streams have converged. The algorithm also
accounts for the convergence of the direct radiant to the
convection shock tubes in the case of a cylindrical heater.
Process specification panels Several process specification panels were added to allow
you to specify the conditions of the process fluids in the
convection and radiant sections.
HTRI Xchanger Suite®
interface
The graphical interface now incorporates the HTRI Xchanger
Suite graphical interface to allow you to specify the physical
properties for all process fluids. You can thus take
advantage of all the HTRI options for specifying fluid
physical properties, including the Property Generator.
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Resizable panels The input panels fill the entire area of the main interface
frame and now resize as you resize the main window frame.
Multiple unit sets Enter input and display output in multiple unit sets. You can
dynamically switch between US, SI, and MKH unit sets.
High-fin geometry databank The graphical interface now includes access to the HTRI
high-fin databank through the High-Fin Definition panel, on
which you can select tube geometry.
Output display on load If you load an .HTRI file that has previously been run, select
the report icon on the toolbar to display the output reports
(without running the case).
Regional settings FH now correctly handles Microsoft® Windows® regional
settings. For example, if you set the decimal point to the
command (,) character, you can use it when specifying input
values.
Selection of
convection/radiant process
fluid
FH supports a process stream passing from the convection
section to the radiant section. Previously, there was no
connection between the two sections; you had to specify
process conditions, physical properties, etc. separately in the
convection and radiant sections.
Stud-fin tube support FH supports specification and use of stud-fin tubes in
convection bundles.
Box heater tube metallurgy You can now specify the tube coil material and/or the tube
metal thermal conductivity for a box heater tube coil.
Log display During case execution, FH displays a resizable window
indicating current run status.
Cancel button Stop any case run using the button on the run log display.
Spreadsheet-style reports The output results are now presented using a spreadsheet-
style format to improve the appearance and readability of the
reports. The reports are automatically scaled to fit the paper
size you choose for printing.
Microsoft® Excel® export You can now export output reports to Microsoft Excel.
API 560 specification sheet FH now produces an API 560 specification sheet. Many
items (e.g., duty, temperatures) are populated with the
calculation results. To populate the remaining items, export
the case to Microsoft Excel.
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Context-sensitive help Access the complete FH manual in online help by pressing
F1 on any input field. You may also browse and search the
entire manual.
All API 530 options The API 530 calculation module now lets you run all API 530
calculations simultaneously. Previously, separate runs were
required to perform the tube thickness design and tube life
evaluation calculations.
Modified convection tube
section definition
The data entry panels for specifying the tube section
geometry in the convection bundles were modified to take
advantage of the increased flexibility that the Xace methods
allow. For example, the previous version required you to
specify staggered layouts by entering each row with a
different left wall clearance. You can now specify staggered
layouts directly with a single entry.
60-row convection limit A logic error in FH 1.01 limited the maximum number of rows
in a convection section to 10. The maximum is now 60 rows
per process fluid.
Case type selection The new case toolbar button prompts for the type of case
(e.g., cylindrical or combustion) you want to create. The
modified file menu offers different selections for each type of
case.
Miscellaneous
Version 5.0
Arbor/U-tube gas space
configurations
Because the arbor/U-tube configuration for box heaters
implies a specific arrangement of burners, this configuration
should be used only with this burner arrangement. The
online help clarifies this issue, informing users when this
configuration is appropriate. (CR 2972)
Surface roughness table in
online help
The program allows selection of the Chenoweth-Martin
pressure drop method (i.e., the large pipe friction factor).
This method requires specification of a surface roughness.
The online help now includes a table for the surface
roughness of common materials. (CR 2849)
Firing limitation on U-tubes Xfh does not allow arbor or U-tube cases to fire from both
end-walls, issuing a message if this design is attempted. The
online help was updated to indicate this limitation. (CR 2650)
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Version 4.0
List of items for predefined
input
HTRI Xchanger Suite contains a feature that allows users to
create a predefined table of exchanger geometry in an
external text file. The user may then select from this list, and
all input defined in the table will be loaded. This modification
creates the possible predefined input values for the Xfh
module. (CR 1894)
Increased error message
buffer
The buffer for error messages in the main cylindrical heater
control routine was increased in size. Some messages were
larger than the buffer size and caused a program crash
when the message was activated. (CR 1525)
Renamed sample input files
for PCL
Xfh is distributed with several PCL sample input files. To
prevent confusion with other HTRI text-based input files, we
renamed the PCL test cases using a file suffix of .PCL rather
than the original .DAT suffix.
(CR 784)
Version 3.0 Service Pack 1
Incorrect version reference in
online help
The online help section on PCL input format incorrectly
referred to FH 2.0. The reference was modified to indicate
FH without a version reference. (CR 1265)
Version 3.0
Additional sample problems Several sample problems have been added to those
installed with FH:
FH_StandardCase_9.HTRI – Double-cell box heater
FH_StandardCase_10.HTRI – Cylindrical heater with
boiling process fluid
FH_StandardCase_11.HTRI – 3 gas space box heater
with double burner heat release in middle space
FH_StandardCase_12.HTRI – 2 gas space box heater
with double tuberow between gas spaces
(CR 359)
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Online help for specifying
insulation input with floor-fired
heaters
The online help was modified to indicate the proper side
(e.g., floor or front) designations to use when specifying
insulation characteristics for floor-fired box heaters. This
update applies only to PCL input. The graphical user
interface (GUI) automatically handles the side ordering. (CR
176)
FH interface registry entries The FH interface uses the Windows registry to store
configuration information (e.g., the level of messages to
view). If the Windows registry is edited incorrectly, the FH
interface can fail to start. A protection code was created to
allow the interface to recover from improper entries in the
registry. (CR 491)
Help topic for U-tubes A new online help topic was created in the Special Cases
section to discuss how U-tube cases should be modeled.
(CR 512)
Obsolete code for box heaters Obsolete message generation code was removed from the
box heater module. This code, if executed during the gas
space mass balance check, would cause a program crash.
This change has no effect on the results or messages
generated. (CR 473)
Xace version run from FH The version of Xace that FH runs to perform process
calculations was changed from 2.0 to 3.0. (CR 646)
Program version The program version number in the FH calculation engine
was changed from 2.0 to 3.0. (CR 645)
Program version in FH GUI The version number and date that appear in the About dialog
box was modified to reflect the new program version. (CR
647)
Incorrect oxidant flow rate
calculation (combustion)
FH was modified to prevent an incorrect oxidant flow rate
calculation when the normalized composition did not sum
exactly to 1.0. The program logic was incorrectly counting on
more precision than was available. The calculations were
modified to allow a small tolerance in the program logic. This
modification resolves HCPA FH 2.0-39. (CR 591)
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Program Outputs
Version 5.0
Reporting of tubes and areas
for convection sections
The program was modified to correctly print the extended
and bare areas for cases that previously printed incorrect
values. Incorrect bare and extended area were reported if
the convection bundles had different heated tube lengths or
if a convection bundle used a tube type that had a number
higher than the number of rows in the convection bundle. For
example, the program did not report the correct area for a
convection bundle that had 3 rows of tubes and used Tube
Type 6 for some of the tubes.
This modification corrects HCPA item Xfh 4.0-32. (CR 3098)
Incorrect fuel oil temperature
on Combustion Diagram report
When the density for a fuel oil was not specified, the
program printed an incorrect fuel oil temperature on the
Combustion Diagram report. Xfh now prints the correct fuel
oil temperature. If you cannot enter the known density of the
fuel oil, we recommend that you use the Liquid Fuel option
instead of the Fuel Oil option.
This modification corrects HCPA item Xfh 4.0-31. (CR 2353)
Multiple printings of flue gas
heat release table
For cylindrical heater cases, the flue gas heat release table
was printed multiple times on the output report. This problem
was corrected, and now the program prints the table only
once. (CR 3249)
Reporting of number of tubes
in convection section
The program was modified to report correctly the number
tubes in the convection section as well as the extended and
bare areas for cases that previously printed incorrect values.
The tube count of the convection section was not reported
correctly if
a convection section bundle in the case had only one row
or
a bundle layout had been modified to have a different
number of tubes per row
This modification corrects HCPA item Xfh 4.0-27.
(CR 3138)
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Invalid cylindrical heater
geometry
Xfh cannot properly zone a cylindrical heater with a height
less than the diameter of the radiant tube circle. Prior to this
modification, the program would fail and issue a message
that the interchange area was negative.
The logic was modified to produce a more meaningful
message that explains the actual cause of failure. This
modification corrects HCPA item Xfh 4.0-16. (CR 2511)
Incorrect reporting of flue gas
properties
Xfh displayed incorrect flue gas physical properties in the
convection section if the stack contained non-bundle
elements (e.g., a straight duct) upstream of the first bundle.
This display issue has been corrected.
This modification corrects HCPA item Xfh 4.0-15. (CR 2938)
Average gas temperature for
cylindrical heaters
The average gas temperature value as reported on the
Cylindrical Heater Output Summary was actually based on
only the recirculating gas, not on all of the gas in the radiant
section volume. The program was corrected to report the
average gas temperature of all the gas zones in the radiant
section volume.
This modification corrects HCPA item Xfh 4.0-23. (CR 3220)
New Cylindrical Radiant
Section Energy Balance report
The program now includes a Cylindrical Radiant Section
Energy Balance report. This output shows the duty
absorbed, the duty lost through the refractory, and the duty
absorbed by the roof sink/shock tubes. The program adds
these values and compares them to the total duty entering
the radiant section.
Additionally, the report breaks down the heat loss through
the refractory (the setting losses) into two components: the
heat lost in zones that contain sink (tube) area, and the heat
lost in zones without sink (tube) area.
This modification corrects HCPA item Xfh 4.0-24. (CR 3198)
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Version 4.0 Service Pack 1
No results on API530 Tube
Thickness Report
Xfh was modifed to print calculated API530 results on the
Tube Thickness Report. For cases in which fluid physical
properties were not specified, the results were not printed to
the output report. This corrects HCPA Xfh-5. (CR 2367)
Missing back refractory
temperatures in Cylindrical
Temperature Profile Report
When verifying that the back refractory temperature exists,
Xfh incorrectly checks roof and floor axial zones instead of
the wall vertical zones. This problem causes the refractory
temperature behind the tubes (values on far right) for some
zones to be missing. Xfh was modified to check the vertical
zones instead of the axial zones. There is no impact on
calculations with this change. (CR 2397)
Version 4.0
Consistent coordinate system
in Box Heater Flow
Distribution and Gas
Temperature Monitors
In previous versions, the displayed Flow Distribution and
Gas Temperature Monitors used the internal coordinate
system. The internal system always treats the Z coordinate
as the direction of firing. However, on these reports, floor
and wall-fired heaters used a different coordinate system.
The report generation logic was modified to always use the
interface coordinate system (e.g., X = Width, Y = depth, Z =
height) when displaying these reports. (CR 1719 and 1721)
Compressed Cylindrical
Heater Temperature Profile
Monitor
Extraneous white space was removed from the Cylindrical
Heater Temperature Profile Monitor, reducing the entire
report from two pages to a single page. (CR 1725)
New Cylindrical Flow
Distribution Monitor
Xfh includes a new output report for cylindrical heater cases.
The Cylindrical Flow Distribution Monitor displays the
distribution of flue gas flows within the cylindrical heater. (CR
1726)
Obsolete "write" statements Xfh now relies completely on a fired heater object model to
store all input and output data. FH used scratch files to hold
data needed to generate the output reports. These
unneeded scratch files have been eliminated. (CR 1741)
Output reports using radiant
tube numbers
The output reports for the box heater were modified to be
consistent in their usage of tube numbers. In FH, some
reports would use the process flow order number while other
reports would use the radiant tube number (a unique number
for each physical tube). In Xfh, all reports consistently use
the radiant tube number. (CR 1297)
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Combustion report templates The combustion output reports were modified to read values
from the new fired heater object model. As part of this
modification, the calculation engine writes all combustion
results to the new fired heater object model. (CR 1329)
Report and plots for
convection section
For Xfh, the convection section has a new stack profile
report as well as several plots that display the flue gas and
process side profiles. (CR 1564)
Check for valid stack
configuration
The program now checks for a valid stack configuration. If
the user creates a stack that has an element after a sudden
exit element, the program issues a fatal message and stops
execution. (CR 1573)
API530 results written to new
fired heater object model
The API530 calculation routines were modified to write the
tube design results to the new fired heater object model
developed for Xfh. (CR 1660)
Heat loss values for floor-fired
box heaters using symmetric
section option
The program was modified to report the correct wall heat
loss values for floor-fired box heaters when the symmetric
section option is used. Previously, such cases reported loss
values too high for the front and back walls and too low for
the roof and floor. (CR 1709)
Fuel pressure on API 560
specification sheet
The API 560 specification sheet was modified to report the
correct fuel pressure. Previously, the value (labeled gauge
pressure) was reported in absolute units. (CR 1844)
Convergence failure message
for gas temperature
calculation
The iteration loop to converge on gas temperatures in a box
heater could fail without issuing any kind of warning to the
user. This modification adds a fatal runtime message if this
iteration fails to converge. This problem had been noticed
only in cases using the No Tubes option. (CR 1850)
Boiling regime on Process
Monitors
The process monitors for the box and cylindrical heater
radiant sections now report the boiling regime. (CR 230)
Fired Heater (Xfh) Online Help About This Version
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Incorrect handling of
incrementation for heaters
fired from both ends
In FH 3.0 Service Pack 2, KXINCR was replaced with the
actual increments used, thus eliminating the need to halve
the incrementation; however, the halving function was not
removed. When the incrementation was halved, only two of
the fraction convection values were read. The middle four
increments were then recorded as 0.0 for fraction
convection. (The fraction convection for these increments
always has an initialized value of 0.0.)
The incrementation is no longer halved. This corrects HCPA
item FH 3.0-30.
Version 3.0 Service Pack 3
GUI crash with API 560
specification sheet report
If a case contained a solid fuel, the FH GUI would crash
when users attempted to view the API 560 specification
sheet report. This problem has been corrected. This corrects
HCPA FH 3.0-22. (CR 1781)
Program version updated to
SP3
The program version number was modified to reflect SP3
(Service Pack 3) in the interface About dialog box and in the
output report headers. (CR 1900)
Version 3.0 Service Pack 1
Service Pack level in report
headers
The FH version displayed on the output report headers was
modified to display "SP1" after the version number to
indicate Service Pack 1. (CR1314)
Version 3.0
Typo in Burner Monitor report The string "Actual numer" was corrected to "Actual number."
(CR 793)
Calculated thermal efficiency The label for thermal efficiency on the Output Summary
report now displays "(LHV)" to indicate that the thermal
efficiency is based on the lower heating value (LHV) of the
fuel. (CR990)
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Incorrect format on Flue Gas
Flow Monitor
Formatting problems on the Flue Gas Flow Monitor report
(for box heaters) were corrected:
– When there were three gas spaces, some of the Gas
Space Total section printed past the end of the sheet.
– Inconsistent font sizes and alignment were used in the Gas
Space header lines.
– Unnecessary rows appeared in various sections.
(CR797)
Crash with very high adiabatic
flames temperatures
The FH interface was modified to allow additional points in
the Flue Gas Heat Release report. The maximum number of
points was increased from 80 to 200. This modification was
necessary to prevent a crash when FH generates this report
and the adiabatic flame temperature exceeded 4315 °C
(7800 °F). This can occur if pure oxygen is used as an
oxidant. The increase allows adiabatic flame temperatures
up to 10538 °C (19000 °F). This modification resolves HCPA
FH 2.0-29. (CR 493)
Number of convection passes
on Output Summary
The output summary report was modified to display the
number of parallel convection passes. If there are multiple
convection fluids, the number of passes is displayed only if
all fluids contain the same number of passes. (CR 470)
API530 tube dimensions on
Input Reprint report
The Input Reprint report was modified for the API530 module
to display the tube dimensions in the current unit set. Prior to
this modification, FH displayed the tube dimensions in U.S.
units regardless of the current unit set. This modification
resolves HCPA FH 2.0-33. (CR 518)
Fatal runtime errors in report
generation
The calculation engine writes results to a memory file which
the FH GUI then parses to generate some output reports. If
the FH engine encounters fatal runtime information while it
writes the memory file, the GUI can crash trying to parse the
incomplete information. The modification improves the
parsing logic in the GUI to gracefully handle this situation.
(CR 507)
Multi-page Flue Gas Heat
Release report
The Flue Gas Heat Release report was modified to allow
multiple pages, required for cases with very high adiabatic
flame temperatures (e.g., O2 as oxidant). (CR 553)
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Previous results in cylindrical
heaters
An array containing results from previous runs in now
initialized at the beginning of a cylindrical heater run. The
initialization was not necessary if the previous runs were
also cylindrical heaters because the results were always
overwritten. If any of the previous runs were box heaters,
then the gas space values on the output summary report
would appear in the cylindrical heater results. This
modification resolves HCPA FH 2.0-26. (CR 524)
Maximum wall temperature for
box heaters
FH was modified to report the true local maximum wall
temperature in the radiant section on the Output Summary
reports. The FH engine stores only a single wall temperature
for each radiant tube. The maximum reported value was the
maximum of these average wall temperatures. With this
modification, the Output Summary now reports the true local
maximum wall temperature in the radiant section. This
modification resolves HCPA FH 2.0-34. (CR 532)
Service pack level on output
reports
The HTRI automation server was modified to clear the
service pack level string for all FH runs. Prior to this
modification, the service pack level string (e.g., SP1) would
appear in the reports if a previous run was re-run using a
base release version. For example, if a case was run and
saved using FH 2.0 SP2, output reports would retain the
SP2 designation even if the case was later run on an FH 2.0
installation that had no service packs installed. (CR 692)
Version 2.0 Service Pack 2
Specified duties in
combustion calculations
The Combustion Diagram report has been modified to
display specified (or calculated) duties and losses for a
single fuel. Prior to this modification, this information was
displayed for double-fuel but not single-fuel cases. (CR 452)
Radiation Methods
Version 5.0
Radiation calculations for all
cases with water or carbon
dioxide on shell side
The radiation calculations now work for all cases with water
or carbon dioxide outside the tubes (e.g., in a convection
bundle). Previously, the program calculated the radiation
coefficient only if the case had both water and carbon
dioxide outside the tubes. (CR 2775)
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Dimensionless direct
interchange areas calculated
for arch volume
The program had been calculating dimensionless direct
interchange areas for the arch volume. The code was
changed to calculate only areas with dimensions. Cases that
did not converge because of shock tube radiation before this
change will now converge. (CR 2436)
Version 4.0 Service Pack 1
Flue gas composition in
standalone convection runs
Xfh was modified to print a warning message specifying the
reason that no gray gas radiation is calculated when
the user does not specify the flue gas composition
OR
the flue gas contains no gray gas components
This corrects HCPA Xfh 4.0-4. (CR 2479)
Fired Heater (Xfh) Online Help Glossary
August 2006 © Heat Transfer Research, Inc. All rights reserved. Page 335 Confidential: For HTRI member use only.
Glossary
A
annular distributor: A cylinder of diameter larger than the shell, used to help distribute fluid into shell side of exchanger. Fluid enters larger cylinder through a nozzle, flows around outside shell, and enters shell through evenly distributed slots cut
into shell well. Sometimes called a vapor belt.
auto straight-line: The ability to generate a straight-line heat release curve when you specify inlet and outlet temperatures and fraction vapors for a fluid. Both fraction vapors must be between 0.001 and 0.999.
B
baffle-to-shell clearance: Diametric distance between baffle outside diameter and shell inside diameter.
baffle cut: For single-segmental baffles, segment opening height expressed as percentage of shell inside diameter. For double- and
triple-segmental baffles, defined as segment height of innermost (center) baffle as percent of shell inside diameter.
baffle cut orientation: Relationship of baffle cut to centerline of inlet nozzle, can be parallel or perpendicular to centerline. Used to
provide orientation description that is independent of shell orientation. For horizontal shell with inlet nozzle on top or bottom of shell, perpendicular is the same as horizontal cut baffles and parallel is the same as vertical cut baffles.
baffle type: Common baffle types are single-segmental, double-segmental, triple-segmental, and rod.
bundle: Tube bundle of exchanger, consists of tubes, baffles, supports, tie rods, spacers, and tubesheets.
bundle-to-shell clearance: Diametric distance between outer tube limit and shell inside diameter.
C
central baffle spacing: Distance from center of one baffle to center of next baffle.
clean heat transfer coefficient: Predicted overall rate at which heat is transferred from hot fluid on one side of exchanger to cold fluid on other side, with zero fouling resistance.
corbel: A projection from the refractory wall that prevents flue gas from bypassing convection section tubes.
cross baffle: Metal plate placed in bundle to alter flow pattern of shellside fluid flow.
D
detuning plate: Metal plate attached to bundle to change acoustic resonance frequencies within bundle.
dirty heat transfer coefficient: Predicted overall rate at which heat is transferred from hot fluid on one side of exchanger to cold fluid on other side, with specified fouling.
dry weight: Weight of heat exchanger when empty.
E
effective area: Total tube outside surface area (including finned area) available for heat transfer. Surface area covered by
tubesheets is not included in this area.
effective mean temperature difference: Average temperature difference between shellside and tubeside fluids. This value is a measure of average driving force for heat transfer.
effective tube length: Effective heat transfer length of heat exchanger's tubes; does not include tube length projecting from tubesheet(s) or tube length contained inside tubesheet(s).
emissivity: A hypothetical black body emits radiation at a rate proportional to the fourth power of the absolute temperature of the body. Actual surfaces emit radiation at a somewhat lesser rate. The emissivity is the ratio of the actual emissivity to that of a black body.
end partition plate: Metal plate in front and/or rear heads used to partition heads for multiple tubepasses.
expansion joint: Cylindrical device located in shell cylinder of fixed tubesheet exchangers; designed to relieve stress caused by difference in expansion or contraction of tube and shell materials resulting from temperature or pressure.
extinction coefficient: A measure of the ability of particles or gases to absorb and scatter photons from a beam of light; a number that is proportional to the number of photons removed from the sight path per unit length.
Glossary Fired Heater (Xfh) Online Help
Page 336 © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.
F
fin area per unit length: Finned tube surface area per unit length of heat exchanger tube.
fin pitch: Distance between adjacent fins, center to center.
H
height under nozzle: Distance between shell inside diameters and edge of first tuberow beneath nozzle.
hot fluid allocation: Location of hot fluid, shell side or tube side.
I
impingement protection: Flow distribution device used to protect tube bundle from damage due to excessive velocities or two-phase flow in the nozzles.
impingement rods: Rods placed below the shell inlet nozzle to prevent impingement of fluid directly onto tubes. Typically, rods are of same size and layout as bundle tubes.
inclination angle: Departure of exchanger shell from horizontal, measured in degrees. Vertical shell has inclination angle of 90°.
Shells are sometimes inclined slightly to promote condensate drainage.
inlet baffle spacing: Distance between tubesheet (or support plate) and first baffle where shellside flow enters exchanger.
L
layout angle: Layout of tubes in relation to direction of shell side crossflow. Given in degrees. Commonly used layout angles are 30°, 45°. 60°, and 90°.
longitudinal baffle: Metal plates within a heat exchanger that are parallel to the tubes. Used to direct fluid flow in desired flow pattern. Longitudinal baffles are present in TEMA F, G, and H shells.
longitudinal tube pitch: Tube center-to-center distance between adjacent tuberows in the direction of shellside flow.
M
mean beam length: The length of a beam that, if directed at right angles to the walls of the firebox, would have the same effect as the average of all beams directed to the walls at their respective angles.
N
no-tubes-in-window: Exchanger with all tubes removed from baffle windows. This type of exchanger is commonly used to prevent flow-induced tube vibration problems.
nozzle: Physical opening for fluid to enter or exit heat exchanger.
nozzle dome: Enlarged nozzle neck used to reduce velocity of fluid entering exchanger and to aid distribution of fluid inside heat exchanger.
number of shell passes: Number of times shellside flow travels all or part of shell longitudinally. For example, TEMA types F and G shells have 2 passes, and TEMA type H has 4 passes.
O
outer tube limit: Diameter of circle beyond which no tubes can be placed in the tubesheet.
outlet baffle spacing: Distance between tubesheet and last baffle at point where shellside flow exits exchanger.
outside area per unit length: Actual outside area of tube plus external fin surface area per unit length of tube.
outside/inside area ratio: Ratio of outside surface area to inside surface area of tube.
overdesign: A theoretical indication of the feasibility of the exchanger design, given in percent. It indicates the amount of extra area the design has for indicated process conditions. A negative value for overdesign indicates that the exchanger is too small for the specified process. A value near zero indicates a close match of process conditions and exchanger area design.
P
partition seal rod: Rod connecting two baffles, located in the pass partition lane to decrease the shellside fluid flowing through the pass partition lane.
passlane: An opening lane between tubepasses.
Fired Heater (Xfh) Online Help Glossary
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R
root diameter: Outside diameter of tube at base of the fin for external finned tube.
S
seal strips: Devices (typically rectangular strips) placed in the circumferential bypass space between tube bundle and shell. Seal strips force fluid from the bypass (C) stream back into the bundle.
shell: That portion of the exchanger (typically from tubesheet to tubesheet) that encloses the tube bundle.
skid bars: Guide bars attached to bundle to assist insertion of bundle into shell.
slot area: The total cross-sectional area of all slots cut in the shell wall for an annular distributor.
T
TEMA shell type: The three-letter designation (e.g., AES) that describes the front head, shell style, and rear head, respectively, of a shell-and-tube heat exchanger.
thermal resistance: Measure of material's ability to prevent heat from flowing through it, equal to difference between temperatures
of opposite faces of body divided by rate of heat flow.
thermosiphon piping: All inlet and outlet piping pertaining to thermosiphon reboiler system.
tie rod: Device used to hold baffles in place during construction. One of several rods located at various points around periphery of bundle that run from front tubesheet to last baffle.
tie rod spacers: Tube or pipe material with inside diameter greater than tie rod diameter and outside diameter greater than baffle
tie rod holes. Spacers slide over tie rods.
transverse tube pitch: Distance between tube row centerlines perpendicular to shellside fluid flow.
tube-to-baffle clearance: Diametric distance between hole in baffle for tube and tube outside diameter.
tubepass layout type: For bundles with more than 1 tubepass, specifies arrangement of tubepasses within bundle. Xist allows 1, 2, 3, 4, 6, 8, 10, 12, 14, or 16 tubepasses in the exchanger bundle. Common types are quadrant, boxed or h-bonded, and
ribbon.
tubesheet: Sheet of metal located between heads and shell to maintain separation of shellside and tubeside fluids. Perforated with tubes to permit tubeside fluid passage through shell.
U
U-bend support: Full baffle placed at or before the tangent to support the bundle. Also, straps of metal inserted in the bundle to support the U-bend region.
W
wall temperature: Temperature at interface between fluid and tube or surface of fouling layer, if present.
wet weight: Weight of heat exchanger when full of water.
Glossary Fired Heater (Xfh) Online Help
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Fired Heater (Xfh) Online Help Index
August 2006 © Heat Transfer Research, Inc. All rights reserved. Page 339 Confidential: For HTRI member use only.
Index
1st Tube Flow Direction 74
A 60
About This Version 291
Absolute Roughness of Common Surfaces
105
Add 150
Add new stack item 90
Add tube type 107
Allowable pressure drop 169
Ambient Air Conditions Panel 10
Ambient air moisture 11
Ambient air pressure 10
Ambient air temperature 11
API - degree API 144
API 530 Calculations 13
API530 Module 13
API530 Summary Panel 15
API560 Specification Sheet 223
Arbor, U-tube, or Inverted U-Tube Gas Space 54
Available Stack Items 90
Average heat flux around tube 33
Average radiant flux 192
Average wind velocity 80
B 60
Bank fin code 172
Before You Get Started 1
Boiling coefficient 77
Boiling Methods 293
Box Geometry - Arbor U-Tube or Inverted U-
Tube 50
Box Geometry - Double- or Single-Cell with
Radiant Wall 49
Box Geometry - No Tubes 50
Box Geometry - Single-Cell Double-Roof
Opening 49
Box Geometry - Single-Cell Side Opening 49
Box Geometry - Single-Cell Top Opening 48
Box Heater 43
Box Heater Firebox Monitor 226
Box Heater Firebox Tables 235
Box Heater Summary Panel 45
Box Heater Tube Coil Geometry 69
Box Heater Type Selection 45
Box Tube Numbers 244
Bridgewall temperature estimate 92
Bulk Density 84
Bulk temperature 134
Bulk temperature at wall 134
Bundle Layout Panel 98
Bundle layout type 93
Bundle Panel 93
Bundle width 96
Burner circle diameter 185
Burner Code List button 61
Burner Code Panel 62
Burner flue gas velocity 186
Burner Group 61
Burner location/firing direction 55
Burner Locations Panel 55
Burner Monitor 228
Burner nozzle diameter 185
Burner Parameters 198
Burner Parameters Panel 58
Burner throat pressure drop constant 198
Calculation Procedures 293
Case 6
Case Configuration Panel 5
Case description 7
Case type 5
Index Fired Heater (Xfh) Online Help
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Center-center spacing 190
Center-to-center spacing 33, 131
Characterization factor 143
Check Film Boiling 76
Circular Fin 172
Clear All Heat Release Data 11
Clear All Passes 72
Clear All Properties 11
Clear All Temperature Data 11
Clear Current Pass 72
Clear Selected Property 11
Coke thermal conductivity 31, 132
Coke thickness 31, 132
Combustion 137
Combustion Calculations 137
Combustion Diagram 207
Combustion Panel 139
Combustion Stream Properties 208
Configuration Panel 184
Configurations with Identical Gas Spaces 52
Convection 157
Convection Flue Gas Monitor 220
Convection Process Monitor 220
Convection section 6
Convection Section Process Specifications171
Convection Summary 219
Convection weighting factors 87
Convective weight factor 124
Corbels 97
Corrosion allowance 37
Corrosion rate 41
Critical heat flux 76
Ctr-to-Ctr 67
Customer 9
Cylindrical Firebox Monitor 222
Cylindrical Firebox Tables 236
Cylindrical Heater Panel 180
Cylindrical Heater Profile 232
Cylindrical Module 179
Cylindrical Radiant Section Energy Balance246
Data Check Messages 204
Data Input and Data Check 308
Databank type 163
Databank Type 109
Delete 150
Delete Stack Items 91
Delete tube type 107
Density 27, 29
Depth 126
Depth D 46
Design life for stress 37
Diameter 127
Diluent flow rate 151
Diluent flow units 151
Diluent Panel 150
Diluent pressure 150
Diluent temperature 151
Diluent type 140
Diluent weight fraction liquid 152
Distance along Axis 57
Distance from heater roof to center of first
tuberow 157
Distance to first tuberow 91
Double-Cell or Single-Cell with Radiant Wall
Gas Space 54
Duty basis 191
DX DY DZ 66
Effect of Parallel Stack Elements 95
Effective Flame Length 58
Effective tube length 190
Effects of Fin Thickness and Height 176
Emissivities Panel 194
Emissivity of sink 124
Enter data for wall 124
Entrance Gas Velocity 59
Equilateral layout 112
Estimated inlet fraction vapor 170
Estimated inlet pressure 171
Estimated inlet temperature 171
Excess oxidant 147
Fired Heater (Xfh) Online Help Index
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External Interfaces 310
F 60
f- and j-Curves 116
Feed Stream to Radiant Section 92
Figure button 65
Fin base thickness 176
Fin bond resistance 119, 174
Fin density 173
Fin efficiency 120, 175
Fin height 165
Fin material 117, 166
Fin root diameter 164
Fin thickness 165
Fin tip thickness 176
Fin type 172
Fins Panels 161
Fins per unit length 164
First tube in zone 129
FJ Curves 114
Flame length 186
Floor thickness 181
Flow 143
Flow basis for heat release curve 12
Flow Distribution Monitor 229
Flow Field Simulation in Box Heaters 89
Flow Field Simulation in Cylindrical Heaters
199
Flow rate 167
Flue Gas Circulation Panel 197
Flue gas extinction coefficient 195
Flue Gas Flow Monitor 225
Flue gas fouling factor 170
Flue Gas Heat Release 209
Flue Gas Opening Dimension A 47
Flue Gas Opening Dimension B 47
Flue gas soot extinction coefficient 86
Flue gas temperature 141
Fluid bulk temperature 30
Fluid name 133
Fluid pressure 26
Flux-to-tube location 33
Fraction of critical flux for film boiling 77
Fraction open 124
Fraction sink 123
Fraction transferred by convection 34
Frequently Asked Questions 285
Fuel composition 153
Fuel composition units 153
Fuel Gas Calculation Options 140
Fuel Oil Panel 142
Fuel type 140
Gas Configuration Panel 50
Gas Panel 152
Gas Space 73
Gas Space Configuration ID 51
Gas Space Definitions 51
Gas Space Energy Balance 224
Gas Space Wall 74
Gas Temperature Monitor 230
Gas Zone Numbering 12, 239
GR - Grade 145
Graphical Interface 311
Half jet angle from vertical 187
Heat Flux Parameters Panel 32
Heat loss 128, 141
Heat release entry type 12
Heat Release Factor/Burner 59
Heat Transfer Coefficient Method 75
Heat Transfer Coefficient Panel 25
Heated lengths 131
Heated tube length 94, 160
Heater Temperature Profile 221
Heater type 125
Height 126, 181
Height H 46
Height T 47
High Fin page 118
Higher heating value 144
High-Finned Tube 109
Incomplete combustion 147
Index Fired Heater (Xfh) Online Help
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Induced flow factor 197
Initial gas zone temperature estimate 88
Initial refractory temperature estimate 88
Initial tube life 40
Inlet fraction vapor 168
Inlet pressure 169
Inlet temperature 168
Input Reprint 206
Insert new stack item 91
Inside heat transfer coefficient 30
Inside Return Bend 64
Insulation heat loss coefficients 194
Insulation Loss Coefficient Panel 193
Insulation specification 12
Insulation Specification Panel 79
Item number 8
Job number 8
K 61
L/D 360-degree twist 122
Left wall clearance 112, 158
Left wall clearance / Clearance wall to first tube
99
Length 175
Life Evaluation 214
Limiting design metal temperature 22
Liquid/Solid Panel 154
L-M constant C per Appendix A.3 23
Load from Databank 163
Load from Databank button 163
Local Coordinate X/Y/Z 56
Location of burner center from X-axis 186
Longitudinal max/avg flux ratio 132
Longitudinal pitch 113, 158
Low Fin page 117
Lower critical temperature 22
Lower heating value 143
Low-Finned Tube 108
Material Code 81
Material constant A per Table 2 22
Material Name 83
Material Thickness 81
Material Type 83
Materials Table 189
Max. Service Temperature 83
Maximum design pressure elastic 35
Maximum local peak flux 37
Maximum operating pressure at End of Run
36
Maximum operating pressure at Start of Run
36
Maximum outside wall temperature 80
Maximum recirculation factor 198
Maximum Tube Length 68
Mean beam length 86, 195
Metal identification 20
Metal Properties 217
Metal Temperature 211
Metal temperature at End of Run 37
Metal temperature at Start of Run 36
Metal temperature End of Run 41
Metal Temperature Parameters Panel 30
Metal temperature Start of Run 41
Minimum Jet Opening 58
Minimum/maximum temperature 80
Miscellaneous 324
Modeling Box Heaters 48
Modulus of elasticity 23
Momentum width factor for gas flow 88
Name Panel 7
No Tube Flux Monitor 238
Nominal outside diameter 188
Nominal Pressure Drop 59
Normalize 144, 150, 153, 156
NOx Conversion Factors 234
Number of burners 185
Number of Burners in Each Gas Space 56
Number of convection fluids included in
specified duty 192
Number of different tube sizes and/or C-C
distance per pass 187
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August 2006 © Heat Transfer Research, Inc. All rights reserved. Page 343 Confidential: For HTRI member use only.
Number of fuels 139
Number of Layers 79
Number of parallel passes 185
Number of process passes 71
Number of radiant tubes 126
Number of stud rings 120
Number of studs in each ring 120
Number of symmetric sections 56
Number of Tube Sections 63
Number of tubepasses 26, 126
Number of tuberows 99
Number of Tubes 68
Number of tubes in 1 pass 190
Number of tubes in each row / Number of tubes
per row 99
On-stream time 40
On-stream time per period 42
Operating Conditions Panel 35
Operating pressure End of Run 40
Operating pressure Start of Run 40
Optional Panel 85
Order... 150
Outlet fraction vapor 168
Outlet temperature 168
Output Reports 201
Output Summary 202
Outside area/length 165
Outside convective heat transfer coefficient128
Outside diameter 180, 188
Outside Diameter 66
Outside/airside f- and j-factors 115
Over fin diameter 174
Overview 1
Oxidant Air Panel 146
Oxidant composition 150
Oxidant composition units 149
Oxidant flow 146
Oxidant flow rate 146
Oxidant flow units 147
Oxidant Gas Panel 149
Oxidant moisture 148
Oxidant pressure 148
Oxidant temperature 148
Oxidant type 139
Parallel elements 94
Parallel passes 94
Pass Sequence 74
Physical Properties for User-Specified
Metallurgy Panel 20
Plain Tube 108
Planar Half Jet Angle 59
Planar peak-to-average factor 34
Planar Peak-to-Average Factor 34
Plant location 9
Poisson s ratio 21
Pressure 133, 142
Pressure in heater 85, 199
Print metal properties for inspection 19
Problem 6
Problem description 7
Process condition 167
Process Conditions Panel 166
Process duty 169
Process flow rate 133
Process fluid coefficient multiplier 78
Process fluid friction factor multiplier 78
Process fouling factor 132, 170
Process fouling layer thickness 169
Process Heat Transfer Coefficient 210
Process inlet 96
Process Methods Panel 75
Process outlet location 185
Process Pass 74
Process tube emissivity 87, 195
Program Outputs 327
Property Monitor 237
Proposal number 8
Pure Component 76
Radiant Box Panel 125
Radiant Box Process Conditions Panel 133
Index Fired Heater (Xfh) Online Help
Page 344 © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.
Radiant duty 141
Radiant section type 6
Radiation Methods 333
Rectangular and Plate Continuous Fin 173
Reference number 8
Refractory surface emissivity 87, 196
Remarks 10
Reorder Stack Items 91
Required tube life 41
Reset All Walls 125
Reset Current Wall 125
Reverse staggered rows 96
Revision 9
Roof opening diameter 182
Roof opening inside diameter 183
Roof opening length 182
Roof opening outside diameter 183
Roof opening width 182
Roof sink surface emissivity 196
Roof sink surface temperature 196
Roof thickness 181
Run length between SOR and EOR 38
Run Log 203
Runtime Messages 205
Rupture stress 24
Rupture stress curve 18
Same as Front End 80
Same as Left Side 80
Select Insulation Material 82
Sensible liquid coefficient 77
Sensible vapor coefficient 77
Serrated Fin 172
Service 9
Set process pass 72
Set tube number 72
Setting loss 166
SG - Specific Gravity 145
Single-Cell, Double Roof Opening Gas Space 53
Single-Cell, Side Opening Gas Space 53
Single-Cell, Top Opening Gas Space 53
Single-Zone Firebox Monitor 240
Sink temperature 124
Soot extinction coefficient 91
Space from Last Burner 57
Special Cases 3
Arbor or U-Tubes 3
Boilers 4
Buried Tubes in Firebox 3
Sloped or Hip Roof 5
Specific gravity 21
Specific heat 27, 28, 135
Specified 127
Specified duty 191
Split segment height 175
Split segment width 175
Stack element bend radius 104
Stack element fitting loss coefficient 101
Stack element flow direction 101
Stack element friction factor 103
Stack element height 100
Stack element length 100
Stack element miter pieces 103
Stack element orientation 100
Stack element outlet geometry - depth 104
Stack element outlet geometry - diameter104
Stack element outlet geometry - shape 103
Stack element outlet geometry - width 104
Stack Element Panels 99
Stack element pressure drop 102
Stack element relative roughness 102
Stack element take-off angle 105
Stack Inlet Geometry - Depth 92
Stack Inlet Geometry - Shape 92
Stack Inlet Geometry - Width 92
Stack Items List 90
Stack Monitor 236
Stack Panel 90
Standard Wall Thicknesses 111
Stream name 170
Stream Properties 241
Fired Heater (Xfh) Online Help Index
August 2006 © Heat Transfer Research, Inc. All rights reserved. Page 345 Confidential: For HTRI member use only.
Stud diameter 121
Stud Fin page 119
Stud length 120
Stud-Finned Tube 108
Surface roughness 78
Surface Zone Numbering 238
TEMA fouling factor 27
Temperature 28, 84, 143
Test Cases 247
Thermal conductivity24, 27, 28, 134, 174, 191
Thermal Conductivity 84
Thermal expansion 24
Thickness 67, 121
Thickness Design 212
Title identification 35
Total mass flow rate for all passes 26
Transverse pitch 113, 158
Tube circle diameter 184
Tube Coil Exists 63
Tube Design option 16
Tube dimensions 164
Tube emissivity 110, 131, 160
Tube firing 129
Tube Flow Direction Panel 73
Tube Flux Monitor 231
Tube Geometry Panel 187
Tube inside diameter 16, 131
Tube internal 106
Tube internals 109
Tube layout 96
Tube Layout Types 113
Tube Length 67
Tube length between return bends 25
Tube Length Orientation 64
Tube life evaluation 15, 39
Tube Life Evaluation Panel 39
Tube Locations Panel 63
Tube material code 109, 159
Tube Metal Databank 18
Tube metallurgy 17, 189
Tube Metallurgy 67
Tube name 106
Tube OD 111
Tube outside diameter 16, 131, 158
Tube position 129
Tube Section Geometry Panel 65
Tube Sink Definition Panel 123
Tube thermal conductivity 110, 131, 159
Tube Thermal Conductivity 67
Tube type 108, 159
Tube type for tube design 16
Tube Types Panel 106
Tube wall thickness 17, 159
Tube wall thickness schedule 189
Tube Zones Panel 128
Tubepass Sequence Panel 71
Tubepasses 95
Tubes and Fin Materials and Dimensions110
Tubes page 107
Tubeside f- and j-factors 115
Tubeside friction factor 78
Twisted Tape page 121
Type of material 21
Type of roof opening 182
Typical Maximum Stud Density 121
Typical Stud-Finned Tube Geometry 120
Typical Values for Medium Grade No. 6 Fuel Oil
145
Ultimate Analysis by Mass % 144
Unheated length between rows 112, 160
Unheated length/row 112, 160
Unset Bank Fin 171
Use ESCOA outside methods 97
User Defined Insulation Materials 83
User Defined Materials... 82
User-defined tubepass layout 98
Valid Burner Coordinates... 57
Viscosity 28, 29, 134
Viscosity at wall 135
w1 w2 w3 51
Index Fired Heater (Xfh) Online Help
Page 346 © Heat Transfer Research, Inc. All rights reserved. August 2006 Confidential: For HTRI member use only.
Wall Size Available 68
Wall Size Required 68
Wall thickness 111, 181, 188
Wall thickness under fins 165
Wall Tube Section 74
Weight fraction vapor 26, 134
Weighting factors for convective heat transfer
200
Width 122, 126, 176
Width U 47
Width V 48
Width W 46
Yield stress 23