introduction to shell and tube heat exchangers.pdf
TRANSCRIPT
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 1/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-1
Introduction to Shell and TubeHeat Exchangers
Introduction
General Description
Identifying Major Components
TEMA Standards Vibration
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 2/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-2
Shell and Tube Heat Exchangers
Tubeside flow (four passes)
Typical Major Components
Floating head
Stationary head
Pass partitions
Pass partitionShellside flow,
one pass
Tubesheet
Baffle
Tube
Shell
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 3/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-3
General Description
The variety of designs and configurationsare almost limitless
Common features: – A collection of tubes manifolded together to
form a “tube bundle”
– A chamber formed around the outside of thetube bundle, the “shell”
One stream flows inside the tube bundle,the other outside the tube bundle,contained by the shell
Identifying Major Components
Tubesheets
Channels
Fixed and floating heads Shell covers
Bundle
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 4/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-4
Tubesheets
Within the scope of TEMA, tubes aremanifolded together with tubesheets orU-bends
A tubesheet is a flat, circular plate drilledto allow the tubes to be inserted
U-bends are used to connect pairs oftubes together to remove the need for atubesheet at one end of the exchanger
Tubesheets / U-bends
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 5/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-5
Straight Tube / U-tube
An exchanger in which two tubesheetsare used is called a straight tubeexchanger
An exchanger with one tubesheet and U-bend returns is called a U-tubeexchanger
Channels
In order to direct the tubeside flow in andout of the tubes, a chamber is attachedto the tubesheet, called a channel
Depending on the design this may alsobe called a bonnet or waterbox
Selection of channel type is based onbalancing access requirements formaintenance against cost
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 6/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-6
Fixed / Floating Heads
Tubesheet may be fastened to the shell,or free to move relative to the shell – A tubesheet which is fastened is called a
fixed head
– A tubesheet which is free to move is called afloating head
A fixed-tubesheet exchanger has bothtubesheets fixed
A floating-head exchanger has one fixedhead and one floating
Shell Cover
In a floating head heat exchanger, aremovable cover may be incorporatedinto the shell at the floating end
Allows access to the floating headwithout disturbing the fixed head
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 7/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-7
Bundles
The tube bundle comprises:
– tubesheets / tubes / U-tubes
– baffles / support plates
– tie-rods / spacers
The tubes may be arranged for singlepass or multi-pass, using pass partition
plates in the channel(s)
Bundle Fabrication
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 8/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-8
TEMA Size and Type
TEMA Designations
The TEMA standard contains a codingsystem to allow the size andconfiguration of a heat exchanger to be
expressed in a concise manner
This description system is widelyaccepted and understood
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 9/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-9
TEMA Type Code
A three letter code is used to describethe configuration:
B E MB E M
Front head
Shell type
Rear head
TEMA Shell Types
Selection of shell type is primarily aprocess/thermal design decision
Different types create different flow pathsthrough the shell
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 10/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-10
TEMA Shell Types
Divided flow
One-pass shell Two-pass shell,longitudinal baffle
E F
J
TEMA Shell Types
Double-split flowSplit flow
Crossflow
X
H
Kettle reboiler
K
G
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 11/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-11
TEMA Front Head Types
Selection of front head type is primarily amechanical design decision
Different types provide various levels ofaccess for maintenance
Cost and pressure-integrity become
factors at higher pressure
TEMA A Type
Channel and
removable cover
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 12/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-12
TEMA B Type
Bonnet (integral cover)
TEMA C Type
Channel integral with tubesheet and removable cover
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 13/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-13
TEMA N Type
Channel integral with tubesheet and removable cover
TEMA D Type
Special High Pressure Closure
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 14/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-14
TEMA Rear Head Types
Selection of rear head type is primarily amechanical design decision
Different types provide various levels ofaccess for maintenance
Types L, M and N imply a fixed-tubesheet construction
Types P, S, T, U and W are floating headtypes (bundle free to expand relative toshell)
TEMA L, M and N Type
L M
N
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 15/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-15
TEMA U Type
TEMA P, S, T and W TypesML
P
S T
W
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 16/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-16
TEMA Size Code
A two-number code
First number is the shell id to the nearestwhole inch
Second number is the tube length to thenearest whole inch
Example: TEMA size 31-240(31” ID shell with 240” (20’) tubes)
TEMA Size Code
For U-tube exchangers, the tube length isthe length of the straight leg
For kettle reboilers, the shell diameter is
expressed as two numbers, the port IDthen the shell ID:
Length
Port IDShell ID
E.g. Size 17/43 - 192
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 17/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-17
Tube Bundle Construction
Heat Exchanger Tubes
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 18/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-18
Heat Exchanger Tubing
Welded vs Seamless Tube
Average vs Minimum Wall
U-tube bending
Tube pitches
Seamless vs Welded
Drawn from a solidbillet or forged
cylinder
Rolled from a flat stripand welded alonglongitudinal seam
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 19/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-19
Which to use?
Welded tube is cheaper and more readilyavailable
Quality of welded tube can be very high:
– continuous testing of weld
– Individual tube pressure testing
– heat treatment of weld
– no significant weld bead outside tube section
Use seamless only for lethal service, veryhigh integrity, or very high pressure
Wall Thickness Tolerance
Important to understand the differencebetween minimum wall and average walltubes
Tolerances are controlled by the ASTMmaterial spec. (e.g. SA-213 is a minimumwall spec., SA-249 is an average wallspec.)
Min. wall usually -0% +20% thickness
Av. wall usually -10% +10% thickness
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 20/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-20
U-tube Bending
The process of forming a U-bend from astraight tube will:
– thin the wall on the outside of the bend
– tend to flatten the tube on the outside of thebend
– tend to crimp the inside of the bend
– work-harden the tube material
These effects limit the diameter of thebend to a minimum value (typically 3Do)
Heat treatment may be required
U-Bend Forming
TEMA limits wall thinning to 17% for non-work hardening materials (equivalent toR = 1.5Do)
Crimping
Flattening
Thinning
R
Do
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 21/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-21
Tube Pitches
60° layout
Pt
30° layout
Pt
90° layout
Pt
45°
layout
Pt
Tube Pitch
A minimum value of Pt must bemaintained:
– To retain mechanical strength in tubesheet
– To allow any welding of tube end
– To allow cleaning outside tubes
Typical: Pt = 1.25 x Dt
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 22/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-22
Tube-to-Tubesheet Attachment
Tubes need to be attached to: – prevent interstream leakage
– transmit mechanical loads
Attachment may be by welding,expansion or both
Type of attachment affects tube pitch
requirement Attachment type has impact on ease of
re-tubing
Types of Attachment
Expansion: – Used as an attachment process providing
both sealing and strength functions
– Light expansion used to remove crevice atback face of tubesheet
Welding: – Seal weld creates a better seal than
expansion, especially at high temperatures
– Strength weld (weld strength ≥ tube strength)provides both sealing and strength
Explosive expansion and welding arealso used
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 23/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-23
Welded Only
Tubesheet
Tube
Weld
Expanded Only
Tubesheet
Tube
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 24/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-24
Welded and Expanded
Tubesheet
Tube
Weld
Back-Face Welding
Tubesheet
Tube
Weld
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 25/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-25
Tube Passes
Tubepasses
Multiple passes are used to:
– increase tubeside velocity
– reduce overall length
– allow U-tube/floating head designs
Single pass designs used to retaincounter-current flow
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 26/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-26
Pass Partitions
Pass partition
2-Pass, B-Type Head
Tubesheet
Drain hole
Weld
Gasket
Pass Lane
Pass Arrangements
4-Passquadrant
6-Passribbon-banded
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 27/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-27
Pass Arrangements
Quadrant(good for U-tubes)
Ribbon-banded(good pass lane
orientation)
1 2
4 3 1
2
3
4
5
6
1
2 3
45
6
H-banded(good tube count
distribution)
Pass Considerations
Number of passes and arrangement ismainly driven by thermal design
Limitations:
– construction of pass partitions
– thermal gradients
– effect on tubecount (total and pass-to-pass)
– gasket seating
– shellside bypassing
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 28/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-28
Baffles
Shellside Baffles
Baffles have two main purposes:
– To direct the shellside fluid in crossflow, toimprove heat transfer
– To support the tubes against sagging andvibration
Described by type, cut and pitch
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 29/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-29
Baffle Types
SingleSegmental
DoubleSegmental
Baffle Pitch and Cut
Pitch
hCut % = (h/Ds) x 100
End Space(often greater than pitch) Ds
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 30/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-30
No-Tubes-in-Window
Standard Single Segmental
No-Tubes-in-Window
Baffle Construction
Triple Segmental
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 31/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-31
Tie-Rod / Spacer
This system allows accurate alignment ofthe baffles during construction
Tie-rod Spacer tube
Baffle
Permits condenserdrainage
Better end zonedistribution
Prevents separationor stratification
Baffle Orientation
Perpendicular cut(perpendicular to nozzle centreline)
Nozzle
Baffle cut
Parallel cut(parallel to nozzle centreline)
Baffle cut
Nozzle
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 32/33
TEMA Shell and Tube Heat Exchangers
© Copyright Progressive Thermal Engineering All rights reserved.Page 1-1-32
Baffle Selection
Selection depends on
– Pressure drop requirements
– Tube support requirements
– Heat transfer requirements
Typical Tubesheet Layout
7/23/2019 Introduction to Shell and Tube Heat Exchangers.pdf
http://slidepdf.com/reader/full/introduction-to-shell-and-tube-heat-exchangerspdf 33/33
TEMA Shell and Tube Heat Exchangers
Tubesheet Layout