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Project Title : HEAT EXCHANGER FOR CHILLED WATER
Part : Horizontal Shell
Prepared by : Rey Fiedacan
Date : 11.07.2010
Doc. No. : HX - 01 -09
Revision No. : 1
Key in value in blue color only
TUBE SIDE: HOT SIDE SHELL SIDE:COLD SIDE
[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 conductivity] 0.6 W/m-K [Thermal conductivity]0.61 W/m-K [Dynamic Viscosity] 0 N.s/m2 , kg/m-s[Dynamic Viscosity] 0 N.s/m2 , kg/m-s
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 Tubes] 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 25%]0.5 m
FINAL DECIDING VALUES BASED ON CORRELATED INPUTS ABOVE
Step #1: Evaluate the LMTD correction factor given the value of P and R ( Computed ) P = 0.19
R = 3
From 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
Enter correction Factor, F 0.94
Step #2: Check the value of overall conductance, U against the recommend values Computed value of U = 1,869.27 Based on the correlation of Reynolds number, flow condition and thermal conductivity, Check this value against permissible range from table
of overall conductance U,
Enter value of U if the computed value is within the range 2263.20
Step #3: Check the % surface design of heat exchanger due to fouling effects Computed value of = 61%
If the value is too high , Set value for desired surface design then enter 30%
Step #4: Evaluate computed length of tube of heat exchanger, Note that standard length is in 20 ft and it is recommended to use it out of the its length
Computed Length = 1.89 m
Enter, the effective length of tubes should not < computed length 4.00
Step #5: Evaluate the re-calculated shell diameter on the new length of HX, Inside diameter should referred to available shell to be used ( can be pipe or rolled plate)
Computed Shell ID = 0.68 m
Enter new shell ID,must be available size 0.80
Step #6: Enter the absolute viscosity at wall temperature, Evaluate at reference temperature T Reference Temp. =24.83
Enter absolute viscosity,kg/m - s at reference Temp. 0
Check the result in the next sheet, Carefully evaluate and proceed next iteration if needed. The areas for iteration will be size, tube layout, flow conditions, geometry
length of tubes ,baffle spacing and tube materials.
DEVELOPED IN EXCEL BY: REY FIEDACAN - MECHANICAL ENGINEER ,11.07.2010
W/m2-K
oC
ENGINEERING CALCULATION
Designed by Rey FiedacanTHERMAL 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 -fiedrey@yahoo.com Revision 1
Project Title : HEAT EXCHANGER FOR CHILLED WATER
Part : Horizontal Shell
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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:
ln LMTD= ### for parallel flowLMTD= ### for counterflow
P = 0.19
R = 3
F = 0.9400 3.0 LMTD Calculation ( Corrected )
where :
= ### K for Counter flowheat transfer between shell & tubes
4.0 HEAT DUTY OF HEAT EXCHANGERbased on the temperature difference between hot fluids inlet
and outlet condition.
= ### KW
5.0 NUMBER OF TUBES- based on the mass flowrate of cold fluid inside the tubes and recommended velocity on the specified number of passes.
= ### tubes
374 per pass II. 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 )
= Ts2 msCps(Ts1-Ts2) mtCpct Δtmax - Δtmin Δtmax Δtmin ΔTm = F(LMTD) Q =(mscps)(Ts1 -Ts2) Nt = 4mtNp/ρtvtπdi2 ht Nutkt di Nut Kt di
which predicts results in the range of 104< Ret < 5 x106 and 0.5 < Pr
t < 200
Nut (f/2)RetPrt
ENGINEERING CALCULATION
Designed by Rey FiedacanTHERMAL 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 -fiedrey@yahoo.com Revision 1
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-2.1 Prandtl number = 6.8
2.2 Reynold number at tube side = = ### the flow is turbulent
2.3 Friction factor at given Re = = 0.01
= = 225.72
= = ###
( This correlated heat transfer coefficient at tube side condition of flow )
III.SHELL SIDE CALCULATION
1.0 SHELL SIDE HEAT TRANSFER BY KERN CORRELATION
= where:
= Nusselt number of fluid outsidethe tubes = Thermal conductivity of fluid outside the tubes = 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 m
0 s
2.6 Tube Pitch Ratio PR = f(Clearance, Baffle spacing)
= = 1.337 m
2.7 Tube Layout Constant = f(Clearance, Baffle spacing)
CL = 1
CL = 0.87
one tube pass CTP = 0.93
Prt Ret ρtvtdi/µt Ft (1.58lnRet - 3.28)-2 Nut (f/2)RetPrt 1.07+12.7(f/2)1/2(Prt2/3 -1) ht Nutkt W/m2-K di
which predicts results in the range of 2x103< Res = G
sDe/µ< 1 x106 ht 0.36ks Res0.55Prs1/3 De Nus Ks de Res Prs Res (ms/As)(De/µs) De do
De of square pitch in tube layout
PT
DeΠ 4(PT2-πdo2/4) m2
De
De of triangular pitch in tube layout PT
do DeΔ 4(PT2(3)1/2/4-πdo2/8) m2 πdo/2 As DsCB m2 PT As πdiNt m2 Ds 0.637(CL/CTP)(πdo2PR2Nt)1/2 PT/do for 90o and 45o for 30o and 60o
ENGINEERING CALCULATION
Designed by Rey FiedacanTHERMAL 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 -fiedrey@yahoo.com Revision 1
two tube pass CTP = 0.9
three tube pass CTP = 0.85
Use: CL = 1.0 CTP =0.930
= = ###
( This correlated heat transfer coefficient at shell side condition of flow )
IV. OVERALL HEAT TRANSFER COEFFICIENT
1.0 Outer surface area - Clean heat transfer coefficient -1 = ln( ) = 1 + 1 + ### ho 2 1.1 = Q = 97.11 Use: = 2263.2
2.0 Outer surface area - Fouled heat transfer coefficient
= ln( ) -1 1 + 1 + + = ### ho 2 2.1 = Q = 156.25
2.2 Check for % surface design
= AcAf = 61%
Use: = ###
2.3 Surface design area of heat exchanger at certain ### more allowance for fouling effect A' = 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 nearest available size either seamless pipe or fabricated as rolled plate
Use: = ### m
V. PRESSURE DROP- This is used to determined the pumping power required to handle the fluid in tubes and shell. 1.0 TUBE SIDE PRESSURE DROP
ht 0.36ks Res0.55Prs1/3 W/m2-K De do Uc do do di W/m2-K di hi kt
Surface area of heat exchanger for clean condition ( No fouling Effect )
Ac m2 UcΔTm Uc do Uf do do di R ft W/m2-K di hi kt
Surface area of heat exchanger for clean condition ( with fouling Effect )
Af m2 UfΔTm Os Os m2 A' Ntπdo Ds' 0.637(CL/CTP)1/2(A'PR2d o/L)1/2 Ds'
Revision
1.1 Tube side friction factor = = ###
1.2 Tube side friction factor
= +
2
= 58.68 Kpa , head required to pump the fluid into the tubes
= 8.5 psi
2.0 SHELL PRESSURE DROPThe shell-side fluid experiences a pressure drop as it passes through the exchanger, over the tubes, and around the baffles.
=
2.1 Shell side friction factor = = 0.300
2.2 Bundle crossflow area = = ###
clearance of tubes and baffle spacing.
2.3 Wall temperature
= + 1
2 2 2
= ###K , average temperature between cold and hot fluid across
the tube length therefore:
the absolute viscosity and wall temperature of24.8
= 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 ft (1.5ln(Ret) - 3.28)-2 µc2 ΔPt ftLNp 4N p ρc di ΔPs fsG2s(Nb+1)D's 2ρsDeΦs fs exp(0.576 -0.19ln(Res))
As DsCB m2, based on corrected shell Φ,
PT Tw Tt1+Tt2 Ts1+Ts2 oC Φs µs µw Nb Gs Ms kg/m2-s As ΔPs fsG2s(Nb+1)D's 2ρsDeΦs
ENGINEERING CALCULATION
Designed by Rey FiedacanTHERMAL 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 -fiedrey@yahoo.com Revision 1
Summary of THERMAL DESIGN OF HEAT EXCHANGER
TUBE SIDE : HOT SIDE
1 Inlet temperature 20 2 Mass flowrate 150 kg/s 3 Density 998.2 4 Thermal Conductivity 0.6 W/m - K 5 Dynamic viscocity 0 6 Specific Heat 4181.6 J/kg - K 7 Prandtl number 6.8
8 Velocity of fluid inside the tubes 2 m/s
9 Total fouling factor 0
SHELL SIDE:COLD SIDE
1 Inlet temperature 32 2 Outlet temperature 25 3 Average temperature 28.5 4 Mass flowrate 50 kg/s 5 Density 996.4 6 Thermal Conductivity 0.61 W/m - K 7 Dynamic viscocity 0 9 Specific Heat 4178.7 J/kg - K 10 Prandtl number 5.64
CONSTRUCTIONAL DATA OF THE PROPOSED SHELL AND TUBE HX
1 Shell diameter 0.800 m
2 Number of tubes 1121.07
3 Length of tubes(Allowancefor tubesheet not included)4.000 m
4 Tube outside diameter 0.019 m
5 Tube inside diameter 0.016 m
6 Baffle spacing ( baffle cut at 25%) 0.500 m
7 Tube pitch 0.025
8 Number of passes 3.000
9 Thermal Conductivity of tubes 42.300
10 Tube side heat transfer coefficient 8526.66
11 Shell side heat transfer coefficient 2800.32
12 Clean overall heat transfer coefficient 1869.27
13 Fouled overall heat transfer coefficient 1406.54
14 Tube side pressure drop 58.68 Kpa
15 Shell side pressure drop 6.40 Kpa
oC kg/m3 N.s/m2 m2 - K/W oC oC oC kg/m3 N.s/m2 W/m- K W/m2 - K W/m2 - K W/m2 - K W/m2 - K
