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HE Design Optimization

ME414 – Thermal Fluid System DesignProfessor John Toksoy

Final Project

Team Members:Kaela HlaulaniPrince Bedell

William BroaddusDerek VleckTrever 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

Single Factor Runs:

I_Counter Flow

Mdot shell

Tube Length

Baffle Space

Tube Thickness

# Tube Passes

Baffle Cut

Shell ID

Shell Thickness

Shell Material

Tube OD

11stst Step: Analyze all 11 variables Step: Analyze all 11 variables 22ndnd Step: Two Factor DOE’s Step: Two Factor DOE’s 33rdrd Step: Critical Variables Optimization Step: Critical Variables Optimization

2 Factor DOE Runs:2 Factor DOE Runs:

Tube LengthTube Length

Baffle SpaceBaffle Space

# Tube Passes# Tube Passes

Shell ID Shell ID

Shell MaterialShell Material

Tube ODTube OD

4 Critical Variables:4 Critical Variables:

Tube LengthTube Length

Baffle SpaceBaffle Space

Shell ID Shell ID

Tube ODTube OD

Opt

imiz

atio

Opt

imiz

atio

nn

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Each design variable is analyzed while everything else is kept constant

Variable Analysis

  q_calc (W)   Mass (kg)   DP_Shell (Pa)   DP_Tube (Pa)

variable Name 20% ↓ 20%↑   20% ↓ 20% ↑   20% ↓ 20% ↑   20% ↓ 20% ↑

                       

I_counter_flow 1.83E+07 5.22E+06   711.06 711.06   2.38E+08 2.38E+08   1.31E+05 1.31E+05

mdot_shell 2.43E+06 6.69E+06   710.77 711.24   1.58E+08 3.32E+08   1.31E+05 1.31E+05

Tube_length 4.17E+06 6.26E+06   568.85 853.28   1.89E+08 2.86E+08   1.07E+05 1.55E+05

Baffle_space 5.36E+06 5.09E+06   711.06 711.06   4.45E+08 1.44E+08   1.31E+05 1.31E+05

Tube_Thickness 5.17E+06 5.28E+06   684.28 748.57   2.38E+08 2.38E+08   1.05E+05 1.88E+05

N_tube_pass   2.59E+06     705.87     2.38E+08     9.48E+05

baffle_cut 5.22E+06 5.22E+06   711.06 711.06   2.38E+08 2.38E+08   1.31E+05 1.31E+05

Shell_id 4.05E+06 6.23E+06   456.96 1020.2   2.87E+08 2.04E+08   2.89E+05 6.95E+04

Shell_thickness 5.22E+06 5.22E+06   707.63 714.5   2.38E+08 2.38E+08   1.31E+05 1.31E+05

Shell_material 5.22E+06 5.22E+06   743.8 750.66   2.38E+08 2.38E+08   1.31E+05 1.31E+05

Tube_OD 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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Effect of each variable on q_calc

1st run Main Effect Plots (11 Variables)

20

16000000

12000000

8000000

4000000

076.851.2 7.24.8

0.1615680.107712

16000000

12000000

8000000

4000000

00.00067080.0004472 10

I_counte_flow

Mean

mdot_shell Tube_length

Baffle_space Tube_Thickness N_tube_pass

Main Effects Plot for qCalcData Means

0.100980.06732

5200000

5150000

5100000

5050000

5000000

0.403920.26928 0.00120.0008

4121

5200000

5150000

5100000

5050000

5000000

0.00627840.0041856

baffle_cut

Mean

Shell_id Shell_thickness

Shell_material Tube_OD

Main Effects Plot for qCalcData Means

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Effect of each variable on DP_tube

1st run Main Effect Plots (11 Variables)

20

1000000

800000

600000

400000

200000

76.851.2 7.24.8

0.1615680.107712

1000000

800000

600000

400000

200000

0.00067080.0004472 10

I_counte_flow

Mean

mdot_shell Tube_length

Baffle_space Tube_Thickness N_tube_pass

Main Effects Plot for DPTubeData Means

0.100980.06732

480000

360000

240000

120000

00.403920.26928 0.00120.0008

4121

480000

360000

240000

120000

00.00627840.0041856

baffle_cut

Mean

Shell_id Shell_thickness

Shell_material Tube_OD

Main Effects Plot for DPTubeData Means

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Effect of each variable on DP_shell

1st run Main Effect Plots (11 Variables)

20

400000000

300000000

200000000

10000000076.851.2 7.24.8

0.1615680.107712

400000000

300000000

200000000

1000000000.00067080.0004472 10

I_counte_flow

Mean

mdot_shell Tube_length

Baffle_space Tube_Thickness N_tube_pass

Main Effects Plot for DPShellData Means

0.100980.06732

320000000

280000000

240000000

200000000

0.403920.26928 0.00120.0008

4121

320000000

280000000

240000000

200000000

0.00627840.0041856

baffle_cut

Mean

Shell_id Shell_thickness

Shell_material Tube_OD

Main Effects Plot for DPShellData Means

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Effect of each variable on weight_HE

1st run Main Effect Plots (11 Variables)

20

800

750

700

650

600

76.851.2 7.24.8

0.1615680.107712

800

750

700

650

600

0.00067080.0004472 10

I_counte_flow

Mean

mdot_shell Tube_length

Baffle_space Tube_Thickness N_tube_pass

Main Effects Plot for Weight_HEData Means

0.100980.06732

900

800

700

600

5000.403920.26928 0.00120.0008

4121

900

800

700

600

5000.00627840.0041856

baffle_cut

Mean

Shell_id Shell_thickness

Shell_material Tube_OD

Main Effects Plot for Weight_HEData Means

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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.)

1st run Main Effect Plots (11 Variables)

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Effect of each variable on q_calc

2nd run Main Effect Plots (6 Variables)

7.24.8

4500000

4000000

3500000

3000000

2500000

0.1615680.107712 10

0.403920.26928

4500000

4000000

3500000

3000000

2500000

4121 0.00627840.0041856

Tube_length

Mean

Baffle_space N_tube_pass

Shell_id Shell_material Tube_OD

Main Effects Plot for qCalcData Means

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Effect of each variable on DP_tube

2nd run Main Effect Plots (6 Variables)

7.24.8

2000000

1500000

1000000

500000

00.1615680.107712 10

0.403920.26928

2000000

1500000

1000000

500000

04121 0.00627840.0041856

Tube_length

Mean

Baffle_space N_tube_pass

Shell_id Shell_material Tube_OD

Main Effects Plot for DPTubeData Means

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Effect of each variable on DP_shell

2nd run Main Effect Plots (6 Variables)

7.24.8

50000000

40000000

30000000

20000000

0.1615680.107712 10

0.403920.26928

50000000

40000000

30000000

20000000

4121 0.00627840.0041856

Tube_length

Mean

Baffle_space N_tube_pass

Shell_id Shell_material Tube_OD

Main Effects Plot for DPShellData Means

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Effect of each variable on weight_HE

2nd run Main Effect Plots (6 Variables)

7.24.8

900

800

700

600

5000.1615680.107712 10

0.403920.26928

900

800

700

600

5004121 0.00627840.0041856

Tube_length

Mean

Baffle_space N_tube_pass

Shell_id Shell_material Tube_OD

Main Effects Plot for Weight_HEData Means

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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.

2nd run Main Effect Plots (6 Variables)

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Effect of each variable on q_calc

3rd run Main Effect Plots (4 Variables)

7.24.8

6000000

5500000

5000000

4500000

40000000.1615680.107712

0.403920.26928

6000000

5500000

5000000

4500000

40000000.00627840.0041856

Tube_length

Mean

Baffle_space

Shell_id Tube_OD

Main Effects Plot for qCalcData Means

Tube_OD

Baffle_space

Shell_id

Tube_length

80706050403020100

Term

Standardized Effect

2.20

Pareto Chart of the Standardized Effects(response is qCalc, Alpha = 0.05)

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Effect of each variable on DP_tube

3rd run Main Effect Plots (4 Variables)

7.24.8

480000

360000

240000

120000

00.1615680.107712

0.403920.26928

480000

360000

240000

120000

00.00627840.0041856

Tube_length

Mean

Baffle_space

Shell_id Tube_OD

Main Effects Plot for DPTubeData Means

AD

A

D

5000004000003000002000001000000

Term

Effect

A Tube_lengthD Tube_OD

Factor Name

Pareto Chart of the Effects(response is DPTube, Alpha = 0.05)

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Effect of each variable on DP_shell

3rd run Main Effect Plots (4 Variables)

7.24.8

500000000

400000000

300000000

200000000

0.1615680.107712

0.403920.26928

500000000

400000000

300000000

200000000

0.00627840.0041856

Tube_length

Mean

Baffle_space

Shell_id Tube_OD

Main Effects Plot for DPShellData Means

BC

AB

BD

C

A

D

B

20151050

Term

Standardized Effect

2.31

A Tube_lengthB Baffle_spaceC Shell_idD Tube_OD

Factor Name

Pareto Chart of the Standardized Effects(response is DPShell, Alpha = 0.05)

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Effect of each variable on weight_HE

3rd run Main Effect Plots (4 Variables)

7.24.8

900

800

700

600

5000.1615680.107712

0.403920.26928

900

800

700

600

5000.00627840.0041856

Tube_length

Mean

Baffle_space

Shell_id Tube_OD

Main Effects Plot for Weight_HEData Means

D

AC

A

C

120100806040200

Term

Standardized Effect

2.2

A Tube_lengthC Shell_idD Tube_OD

Factor Name

Pareto Chart of the Standardized Effects(response is Weight_HE, Alpha = 0.05)

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Minitab Optimization

Critical Variables:

Tube Length Baffle Space Shell ID Tube OD

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Final Design Specifications

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 ?