Transcript Heat Exchanger Design Optimization ME414 – Thermal Fluid

HE Design Optimization
ME414 – Thermal Fluid System Design
Professor John Toksoy
Final Project
Team Members:
Kaela Hlaulani
Prince Bedell
William Broaddus
Derek Vleck
Trever Zike
Seth Simonson
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Project Definition





Design heat exchanger to reduce fluid by 20 degrees
Celsius.
Mass flow rate at the inlet of tube side is fixed at
220,000 kg/hr.
Inlet flow rate of shell is a design parameter.
Inlet temperature of shell fluid is 20 degrees Celsius.
Both fluids are considered as water.
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Design Optimization Goals

System must cool fluid from 45 C to 25 C

Length of Heat Exchanger cannot exceed 7 m

Shell Diameter cannot exceed 2 m

Shell and Tube weight must be minimized

Pressure drop of Shell and Tube must also be
minimized
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Introduction

MATLAB is used to perform DOE runs.

Minitab is used to evaluate the importance of the
variables according to the DOE runs (Main Effect Plots).

Relatively unimportant variables are selected and
eliminated (fixed).

Most important variables are optimized using Minitab.
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Design – Funneling Process
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1st Step: Analyze all 11 variables
2nd Step: Two Factor DOE’s
3rd Step: Critical Variables Optimization
Single Factor Runs:
2 Factor DOE Runs:
4 Critical Variables:
Tube Length
Baffle Space
# Tube Passes
Shell ID
Shell Material
Tube OD
Tube Length
Baffle Space
Shell ID
Tube OD
Mdot shell
Tube Length
Baffle Space
Tube Thickness
# Tube Passes
Baffle Cut
Shell ID
Shell Thickness
Shell Material
Tube OD
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Optimization
I_Counter Flow
Variable Analysis

Each design variable is analyzed while everything else is kept
constant
q_calc (W)
variable Name
I_counter_flow
mdot_shell
Tube_length
Baffle_space
Tube_Thickness
N_tube_pass
baffle_cut
Shell_id
Shell_thickness
Shell_material
Tube_OD
Mass (kg)
DP_Shell (Pa)
DP_Tube (Pa)
20% ↓
20%↑
20% ↓
20% ↑
20% ↓
20% ↑
20% ↓
20% ↑
1.83E+07
5.22E+06
711.06
711.06
2.38E+08
2.38E+08
1.31E+05
1.31E+05
2.43E+06
6.69E+06
710.77
711.24
1.58E+08
3.32E+08
1.31E+05
1.31E+05
4.17E+06
6.26E+06
568.85
853.28
1.89E+08
2.86E+08
1.07E+05
1.55E+05
5.36E+06
5.09E+06
711.06
711.06
4.45E+08
1.44E+08
1.31E+05
1.31E+05
5.17E+06
5.28E+06
684.28
748.57
2.38E+08
2.38E+08
1.05E+05
1.88E+05
2.59E+06
705.87
2.38E+08
9.48E+05
5.22E+06
5.22E+06
711.06
711.06
2.38E+08
2.38E+08
1.31E+05
1.31E+05
4.05E+06
6.23E+06
456.96
1020.2
2.87E+08
2.04E+08
2.89E+05
6.95E+04
5.22E+06
5.22E+06
707.63
714.5
2.38E+08
2.38E+08
1.31E+05
1.31E+05
5.22E+06
5.22E+06
743.8
750.66
2.38E+08
2.38E+08
1.31E+05
1.31E+05
6.75E+06
4.22E+06
745.51
686.69
3.08E+08
1.92E+08
2.37E+05
8.67E+04
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1st run Main Effect Plots
(11 Variables)

Effect of each variable on q_calc
Main Effects Plot for qCalc
Main Effects Plot for qCalc
Data Means
I_counte_flow
Data Means
mdot_shell
Tube_length
baffle_cut
16000000
Shell_thick ness
5200000
12000000
5150000
8000000
5100000
5050000
4000000
5000000
0
0
2
Baffle_space
51.2
76.8
Tube_Thick ness
4.8
7.2
N_tube_pass
16000000
Mean
Mean
Shell_id
0.06732
0.10098
Shell_material
0.26928
0.40392
Tube_OD
5200000
12000000
5150000
8000000
5100000
5050000
4000000
5000000
0
0.107712
0.161568
0.0004472
0.0006708
0
1
21
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41
0.0041856
0.0062784
0.0008
0.0012
1st run Main Effect Plots
(11 Variables)

Effect of each variable on DP_tube
Main Effects Plot for DPTube
Main Effects Plot for DPTube
Data Means
I_counte_flow
1000000
Data Means
mdot_shell
baffle_cut
Tube_length
800000
240000
400000
0
2
Baffle_space
51.2
76.8
4.8
Tube_Thickness
7.2
N_tube_pass
Mean
120000
200000
Mean
Shell_thickness
360000
600000
1000000
Shell_id
480000
0
0.06732
0.10098
Shell_material
0.26928
0.40392
Tube_OD
480000
800000
360000
600000
240000
400000
120000
200000
0
0.107712
0.161568
0.0004472
0.0006708
0
1
21
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41
0.0041856
0.0062784
0.0008
0.0012
1st run Main Effect Plots
(11 Variables)

Effect of each variable on DP_shell
Main Effects Plot for DPShell
Main Effects Plot for DPShell
Data Means
I_counte_flow
Data Means
mdot_shell
Tube_length
baffle_cut
Shell_id
0.06732
0.10098
Shell_material
0.26928
0.40392
Tube_OD
Shell_thickness
320000000
400000000
280000000
300000000
240000000
100000000
0
2
Baffle_space
51.2
76.8
Tube_Thickness
4.8
7.2
N_tube_pass
Mean
Mean
200000000
200000000
320000000
400000000
280000000
300000000
240000000
200000000
200000000
100000000
0.107712
0.161568
0.0004472
0.0006708
0
1
21
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0.0041856
0.0062784
0.0008
0.0012
1st run Main Effect Plots
(11 Variables)

Effect of each variable on weight_HE
Main Effects Plot for Weight_HE
Main Effects Plot for Weight_HE
Data Means
I_counte_flow
Data Means
mdot_shell
Tube_length
baffle_cut
800
Shell_thickness
900
750
800
700
700
650
600
0
2
Baffle_space
51.2
76.8
4.8
Tube_Thickness
7.2
N_tube_pass
800
Mean
600
Mean
Shell_id
500
0.06732
0.10098
Shell_material
0.26928
0.40392
Tube_OD
900
750
800
700
700
650
600
600
500
0.107712
0.161568
0.0004472
0.0006708
0
1
21
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41
0.0041856
0.0062784
0.0008
0.0012
1st run Main Effect Plots
(11 Variables)

Following variables were eliminated as a result of 1st
DOE
 I counter flow (We chose counter flow to Increase LMTD
correction factor and heat exchanger effectiveness)
 Baffle cut (We chose 84.15 mm)
 Shell thickness (Only affects the weight, so we chose a
reasonably thin shell)
 Tube thickness (We chose a thickness of 0.559 mm)
 mdot _shell (We chose a value of 64 Kg/m3 to minimize
Dp_Shell.)
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2nd run Main Effect Plots
(6 Variables)
Effect of each variable on q_calc
Main Effects Plot for qCalc
Data Means
Tube_length
Baffle_space
N_tube_pass
4500000
4000000
3500000
3000000
2500000
Mean

4.8
7.2
Shell_id
0.107712
0.161568
Shell_material
0
1
Tube_OD
4500000
4000000
3500000
3000000
2500000
0.26928
0.40392
21
41
0.0041856
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0.0062784
2nd run Main Effect Plots
(6 Variables)
Effect of each variable on DP_tube
Main Effects Plot for DPTube
Data Means
Tube_length
Baffle_space
N_tube_pass
2000000
1500000
1000000
500000
Mean

0
4.8
7.2
Shell_id
0.107712
0.161568
Shell_material
0
1
Tube_OD
2000000
1500000
1000000
500000
0
0.26928
0.40392
21
41
0.0041856
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0.0062784
2nd run Main Effect Plots
(6 Variables)
Effect of each variable on DP_shell
Main Effects Plot for DPShell
Data Means
Tube_length
Baffle_space
N_tube_pass
50000000
40000000
30000000
20000000
Mean

4.8
7.2
Shell_id
0.107712
0.161568
Shell_material
0
1
Tube_OD
50000000
40000000
30000000
20000000
0.26928
0.40392
21
41
0.0041856
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0.0062784
2nd run Main Effect Plots
(6 Variables)
Effect of each variable on weight_HE
Main Effects Plot for Weight_HE
Data Means
Tube_length
Baffle_space
N_tube_pass
900
800
700
600
Mean

500
4.8
7.2
0.107712
Shell_id
0.161568
0
Shell_material
1
Tube_OD
900
800
700
600
500
0.26928
0.40392
21
41
0.0041856
CUMMINS CONFIDENTIAL
0.0062784
2nd run Main Effect Plots
(6 Variables)

Variables Eliminated:
 Number of tube passes
 We sacrificed some amount of heat transfer, however, we
minimized the pressure drop, which implies that we can use
less powerful pump.
 Shell material
 We chose pure aluminum because:
 It has a high thermal heat coefficient
 low weight.
 Fluid has same properties as water, therefore there is no corrosion
hazard.
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3rd run Main Effect Plots
(4 Variables)

Effect of each variable on q_calc
Main Effects Plot for qCalc
Pareto Chart of the Standardized Effects
Data Means
Tube_length
6000000
(response is qCalc, Alpha = 0.05)
2.20
Baffle_space
5500000
Tube_length
5000000
Shell_id
4000000
4.8
7.2
0.107712
Shell_id
6000000
0.161568
Tube_OD
Term
Mean
4500000
Baffle_space
5500000
Tube_OD
5000000
4500000
0
4000000
0.26928
0.40392
0.0041856
0.0062784
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10
20
30
40
50
Standardized Effect
60
70
80
3rd run Main Effect Plots
(4 Variables)

Effect of each variable on DP_tube
Main Effects Plot for DPTube
Pareto Chart of the Effects
Data Means
Tube_length
(response is DPTube, Alpha = 0.05)
Baffle_space
F actor Name
A
Tube_length
D
Tube_O D
480000
360000
D
240000
0
4.8
7.2
0.107712
Shell_id
0.161568
Term
Mean
120000
A
Tube_OD
480000
360000
AD
240000
120000
0
0
0.26928
0.40392
0.0041856
0.0062784
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100000
200000
300000
Effect
400000
500000
3rd run Main Effect Plots
(4 Variables)

Effect of each variable on DP_shell
Main Effects Plot for DPShell
Pareto Chart of the Standardized Effects
Data Means
Tube_length
500000000
(response is DPShell, Alpha = 0.05)
2.31
Baffle_space
400000000
D
300000000
A
4.8
7.2
0.107712
Shell_id
500000000
0.161568
Tube_OD
Term
200000000
Mean
F actor
A
B
C
D
B
C
BD
400000000
AB
300000000
BC
200000000
0
0.26928
0.40392
0.0041856
0.0062784
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5
10
Standardized Effect
15
20
Name
Tube_length
Baffle_space
Shell_id
Tube_O D
3rd run Main Effect Plots
(4 Variables)

Effect of each variable on weight_HE
Main Effects Plot for Weight_HE
Pareto Chart of the Standardized Effects
Data Means
Tube_length
(response is Weight_HE, Alpha = 0.05)
Baffle_space
2.2
F actor
A
C
D
900
800
C
700
A
500
4.8
7.2
0.107712
Shell_id
0.161568
Tube_OD
Term
Mean
600
AC
900
800
D
700
600
0
500
0.26928
0.40392
0.0041856
0.0062784
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20
40
60
80
Standardized Effect
100
120
Name
Tube_length
Shell_id
Tube_O D
Minitab Optimization
Critical Variables:

Tube Length

Baffle Space

Shell ID

Tube OD
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Final Design Specifications
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

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Tube Length = 6.06 m
Baffle Space = 0.1616 m
Shell ID = 0.2693 m
Tube OD = 6.3 E-3 m
Weight
= 547.9 kg
DP Shell = 238 MPa
DP Tube = 45.44 KPa
Q_Calc
= 5,227 KW
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Conclusion

The Shell Pressure is high because we selected baffles
• Baffles induce turbulence which increases heat loss.

We chose a low Fouling factor of 3E-5:
• The chemical has water like properties which minimizes the
likelihood of fouling.

We chose a 90° square pitch:
• makes cleaning of the tubes easier
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Questions ?
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