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Design of Heat Exchanger Engr. Rey F. Fiedacan, MEP - ME

DEVELOPED IN EXCEL BY: REY FIEDACAN - MECHANICAL ENGINEER ,11.07.2010

ENGINEERING CALCULATIONTHERMAL DESIGN OF HEAT EXCHANGER

APPLIED LIMITATION: SENSIBLE COOLING or SENSIBLE HEATING ONLY

Project Title : HEAT EXCHANGER FOR CHILLED WATERPart : Horizontal ShellPrepared by : Rey FiedacanDate : 11.07.2010Doc. No. : HX - 01 -09Revision No. : 1Key in value in blue color only

TUBE SIDE: HOT SIDE SHELL SIDE: OLD SID[Fluid medium] WATER [Fluid medium] WATER[Mass flowrate] 150 Kg/s [Mass flowrate] 50 Kg/s[Inlet temperature] 20 C [Inlet temperature] 32 C[Density] 998.2 kg/m3 [Density] 996.4 kg/m3

[Specific heat] 4181.6 J/Kg-K [Specific heat] 4178.7 J/Kg-K [Thermal conductivit 0.6 W/m-K [Thermal conductivit 0.61 W/m-K [Dynamic Viscosity] 0 N.s/m2 , kg/m-s [Dynamic Viscosity] 0 N.s/m2 , kg/

FLOW CONDITION[Type of flow] Counter flow

[Design Fouling Factor] 0 m2- K/W

ESSENTIAL VARIABLES[Tube materials] WATER

[Velocity of fluid inside Tubes] 2 m/s

[Tube Outside Diameter] 19 mm

[Tube Inside Diameter] 16 mm

[Thermal Conductivity of Tube 42.3 W/m-K TUBE ORIENTATION & GEOMETRY

[Number of Passes] 3

[Tube Pitch] 0.03 mm

[Tube layout] Square Layout

[Tube Count Layout] 45 deg.

[Baffle Spacing - baffle cut at 2 0.5 m

FINAL DECIDING VALUES BASED ON CORRELATED INPUTS ABOVEStep #1: Evaluate the LMTD correction factor given the value of P and R ( Computed )

P = 0.19

R = 3From this set of conditions, See Table on LMTD correction factor to determine the factor F corresponding to type of flow ( Parallel or counterflow) and number of passes

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ENGINEERING CALCULATION Designed by Rey Fiedacan

THERMAL CALCULATION OF HEAT EXCHANGER Date 11.07.2010

TYPE: SHELL & TUBES Doc. No. HX - 01 -09

DEVELOPED USING EXCEL BY REY FIEDACAN,MECHANICAL ENGINEER, 11.07.2010 [email protected] Revision 1

Project Title : HEAT EXCHANGER FOR CHILLED WATER

Part : Horizontal Shell

H E A T E X C H A N G E

R T H E R M A L C A L C U L A T I O N B Y R E Y F I E D

A C A N

, M E P -

M E

Sketch :

I.HEAT & MASS BALANCE

1.0 Temperature of outlet fluid - Cold fluid ( Predicted from energy and mass balance)

= = ### K

2.0 Log mean temperature difference across the heat exchanger (LMTD)

LMTD = = 7.1 K where:

lnLMT = ### for parallel flowLMT = ### for counterflow

P = 0.19R = 3

F = 0.9400

3.0 LMTD Calculation ( Corrected )where :

= ### K for Counter flowheat transfer between shell & tubes

4.0 HEAT DUTY OF HEAT EXCHA based on the temperature difference between hot fluids inletand outlet condition.

= ### KW

5.0 NUMBER OF TUBE - based on the mass flowrate of cold fluid inside the tubes and recommendedvelocity on the specified number of passes.

= ### tubes374 per passII. TUBE SIDE CALCULATION:

1.0 TUBE SIDE HEAT TRANSFER

= where:= Nusselt number of fluid inside the tubes= Thermal conductivity of fluid inside the tubes= Inside diameter of tubes

2.0 NUSSELT NUMBER ( CORRELATION FROM Petukhov - Kirililov for Turbulent flows )

=

T s2

m s p s s1 - s2m tCp ct

max - min

max

min

m =

= m sc ps s1 - s2

Nt

= 4mtN

p/ρ

tv

tπd

i

2

h t

Nu tk t

d i Nu tK t

i

which predicts results in the range of 10 4< Ret < 5 x10 6 and 0.5 < Pr t < 200

Nu t

e t r t

1.07+12.7(f/2) 1/2 (Prt 2/3 -1)

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2.1 Prandtl number = 6.8

2.2 Reynold number at tube s = = ### the flow is turbulent

2.3 Friction factor at given Re = = 0.01

= = 225.72

= = ###( This correlated heat transfer coefficient acondition of flow )

III.SHELL SIDE CALCULATION1.0 SHELL SIDE HEAT TRANSFER BY KERN CORRELATION

= where:= Nusselt number of fluid outsidethe tubes= Thermal conductivity of fluid outside the t= Equivalent diameter of shell= Reynold number flow outside the tubes= Prandtl number of flow outside the tunes

2.1 Reynolds Number = = ### the flow is turbulent

2.2 Equivalent Diameter = f(Square,Triangular layout)

Flow

== ###

S s

Flow

= = ###0 s

Use: Square Pitch ; De =0.024234

2.3 Bundle Crossflow = f(Clearance, Baffle spacing)

= = ###0 s

2.4 Total flow area of tubes = f(Clearance, Baffle spacing)

= = ###4 0 s

2.5 Estimated Shell Diameter = f(Clearance, Baffle spacing)

= = 0.996 m0 s

2.6 Tube Pitch Ratio PR = f(Clearance, Baffle spacing)= = 1.337 m

2.7 Tube Layout Constant = f(Clearance, Baffle spacing)CL = 1CL = 0.87

one tube pass CTP = 0.93

r t

e t ρ tv t i µ t

F t (1.58lnRe t - 3.28) -2

Nu t

/2 Re tPr t

1.07+12.7(f/2) 1/2 (Prt 2/3 -1)

h t

Nu tk t W/m 2 -K d i

which predicts results in the range of 2x10 3< Res = G sDe /µ< 1 x106

ht

0.36k s Re s0.55 Pr s

1/3

e u s

s

eRes

r s

Re s (m s /As)(D e /µ s)

D e

d o

e o square p c n u e ayouP T

D eΠ

4(P T2-πdo 2 /4) m 2

e

D e o tr angu ar p tc n tu e ayou P T

d o

D eΔ4(P T

2(3) 1/2 /4-πdo 2 /8) m 2

π o

As

DsCB m 2

T

As

πd iNt m 2

D s

0.637(CL/CTP)(πdo 2PR2N t)1

P T/d o

for 90 o and 45 o

for 30 o and 60 o

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two tube pass CTP = 0.9three tube pass CTP = 0.85Use: CL = 1.0 CTP 0.930

= = ###( This correlated heat transfer coefficient at shel condition of flow )

IV. OVERALL HEAT TRANSFER COEFFICIENT1.0 Outer surface area - Clean heat transfer coefficient

-1

=ln( )

=1

+1

+ ###ho 2

1.1

= Q = 97.11

Use: = 2263.22.0 Outer surface area - Fouled heat transfer coefficient

=ln( )

-11

+1

+ + = ###ho 2

2.1

= Q = 156.25

2.2 Check for % surface design

=Af

= 61%AcUse: = ###

2.3 Surface design area of heat exchanger at ### more allowance for fouling effectA' = 126.24

2.4 Effective length of tube for area in heat transfer

L = = 1.89 m

Use: L = ### m

2.5 New Shell Diameter = f(Clearance, Baffle spacing)== 0.68 m corrected shell diameter at the given length

however, the actual diameter shall be the nearestavailable size either seamless pipe or fabricated as rolledplate

Use: = ### m

V. PRESSURE DRO - This is used to determined the pumping power required to handle the fluid in tubes an1.0 TUBE SIDE PRESSURE DROP

h t0.36k s Re s

0.55 Pr s1/3 W/m 2 -K

e

o

U co o i W/m 2-K i i t

Surface area of heat exchanger for clean condition ( No fouling Effect )

Ac m 2

c m

c

o

U f o o i Rft W/m 2-K i i t

Surface area of heat exchanger for clean condition ( with fouling Effect )

Af m 2

Uf ΔTm

O s

O s

m 2

A'

Ntπ o

D s '

0.637(CL/CTP) 1/2 (A 'PR 2d o/L) 1/2

Ds '

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1.1 Tube side friction factor = = ###

1.2 Tube side friction factor= +

2= 58.68 Kpa , head required to pump the fluid into the tube

= 8.5 psi

2.0 SHELL PRESSURE DRO The shell-side fluid experiences a pressure drop as it passes through the exover the tubes, and around the baffles.

=

2.1 Shell side friction factor = = 0.300

2.2 Bundle crossflow area = = ###

clearance of tubes and baffle spacin

2.3 Wall temperature= +

1

2 2 2

= ### K , average temperature between cold and hot fluid acthe tube length

therefore:the absolute viscosity and wall temperatu 24.8

= 0 kg/m - s

2.4 Correction Factor=

0.14= 0.989

2.5 Number of Baffles = L-1 = 7

B

2.6 Number of Baffles= = ###

therefore: =

= 6.4 Kpa , head required to pump the fluid into the shell= 0.9 psi

f t (1.5ln(Re t) - 3.28) -

µc2

ΔP t

f tLNp 4N p ρ cd i

ΔP s

f sG2

s(N b+1)D' sρ s e s

f s exp(0.576 -0.19ln(Re s))

As DsCB m 2 , based on corrected shell Φ,P T

Tw

T t1 +T t2 T s1 +T s2

oC

Φ s

µs

µw

N b

G s

Ms kg/m 2-sAs

ΔP s

f sG2

s(N b+1)D' s2ρ sDe Φs

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Summary of THERMAL DESIGN OF HEAT EXCHANGER

TUBE SID HOT SIDE1 Inlet temperature 202 Mass flowrate 150 kg/s3 Density 998.24 Thermal Conductivity 0.6 W/m - K 5 Dynamic viscocity 0

6 Specific Heat 4181.6 J/kg - K 7 Prandtl number 6.88 Velocity of fluid inside the tubes 2 m/s9 Total fouling factor 0

SHELL SI COLD SIDE1 Inlet temperature 322 Outlet temperature 253 Average temperature 28.54 Mass flowrate 50 kg/s5 Density 996.46 Thermal Conductivity 0.61 W/m - K 7

Dynamic viscocity 09 Specific Heat 4178.7 J/kg - K

10 Prandtl number 5.64CONSTRUCTIONAL DATA OF THE PROPOSED SHELL AND TUBE HX

1 Shell diameter 0.800 m2 Number of tubes 1121.073 Length of tubes(Allowancefor tubesheet not inclu 4.000 m4 Tube outside diameter 0.019 m5 Tube inside diameter 0.016 m6 Baffle spacing ( baffle cut at 25%) 0.500 m7 Tube pitch 0.0258 Number of passes 3.0009 Thermal Conductivity of tubes 42.300

10 Tube side heat transfer coefficient 8526.6611 Shell side heat transfer coefficient 2800.3212 Clean overall heat transfer coefficient 1869.2713 Fouled overall heat transfer coefficient 1406.5414 Tube side pressure drop 58.68 Kpa15 Shell side pressure drop 6.40 Kpa

oC

kg/m 3

N.s/m 2

m 2 - K/W

oCoCoC

kg/m 3

N.s/m2

W/m - K W/m 2 - K W/m 2 - K W/m 2 - K W/m 2 - K

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OIL COOLER DESIGN

Shell Side Tube Side

Fluid Hot Water Fluid ColdMass Flow Rate Kg/h 180000 Mass Flow Rate Kg/hInlet Temp Th1 © 32 Inlet Temp Tc1 ©Outlet Temp Th2 © 25 Outlet Temp Tc2 ©Temp Diff 7 Temp Diff Avg Temp © 28.5 Avg Temp ©Specific Heat Kcal/Kg C 1 Specific Heat Kcal/Kg CDensity Kg/m3 996.4 Density Kg/m3Viscosity Kg/m.s 0Thermal Conductivity Kcal/m.h.C 0.53 Thermal Conductivity Kcal/m.h.C

Heat Duty 1257858 Kcal/h Tc1 Tc2Assume 1 1 Pass Counter Current Th2 Th1

Del T1 © 5 Del T2 © 9.67LMTD © 7.08Let Correction Factor Ft 0.98MTD 6.94

Assume 1462539.45Uo 241 Kcal/h m CSo Ao 752.3 m2

Let for tubeID 0.02 m

OD 0.03 mt 0 mL 12 mSo no of tubes Nt 798.61 tubes

Inside Heat Transfrer Coefficient hi

Inside area of one tube 0 m2Volumetric Flow in 1 tube 0 m3/sVelocity in tube 2.81 m/s

Reynolds no Re 45606.15 L/di 750

jH 62 from graphPrandtl no Pr 6.8hi 3816.51 Kcal/h m2 C

Outside Heat Transfrer Coefficient ho`Triangular Pitch ln 0.03 mClearance c 0.01 m

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Inside Dia of shell Ds 0.98 mBaffle spacing B 0.84 mNb 14.37 12Flow area as 0.2 m2Mass Flow rate of oil Gs 907368.94 Kg/m2.hEq.Dia for triangular pitch Dh 0.02 m

Eq.Dia for square pitch Dh 0.06 mReynolds no Rs 6899.25

jH 52 from graphPrandtl no Pr 5.64ho 2154.8 Kcal/h m2 C

Overall Heat Transfrer Coefficient UoUc 1377.22

Rdo 0 h m2 C/KcalRdi 0 h m2 C/Kcal Rd 0Uo 526.74 Kcal/h m2 C

Area Required 131.64 m2

Tube Side Pressure Drop

Flow area / pass at 0.16 m2Mass flow rate of water 934.17 Kg/m2 .sfriction factor f 4.50E-03 from graphDel Pt(tube side loss) 150.54 Kg/m2

0.01 atmDel Pr(Return loss) 3211.49

0.31 atmDel Pts 0.33 atm

Shell Side Pressure Drop

friction factor f 3.60E-02 from graphDel Pss 65.73 Kg/m2

0.01 atm

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WATER540000

2022.33

2.3321.17

1998.2

00.52

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