Analysis of Compact Heat Exchangers as an Intercooler in PEMFC Systems

1
Analysis of Compact Heat Exchangers as an
Intercooler in PEMFC Systems

• Ph.D. Student Takamasa Ito
• Dr. Jinliang Yuan
• Professor Bengt Sundén
• Department of Heat and Power Engineering
• Lund Institute of Technology

2
Todays Outline

• Introduction
• Problem statement
• Analysis method
• Result and discussion
• Conclusion

3
Introduction
Around 160 oC
Figure 1. Proton Exchange Membrane Fuel Cell
(PEMFC) system.
Aim of intercooler Compressed reactant air
cooling
4
Introduction

• Demand of an intercooler according to last paper
  1
• High system operating pressure
• High ambient temperature
• Low cathode operating temperature
• High stoichiometry of reactant
• System with internal humidification
• Large H2O gas-phase content for the
  humidification
• 1 Ito, T., Yuan, J. and Sundén, B., 2004, Heat
  and Mass Balances of an Intercooler in PEM Fuel
  Cell Systems, ASME FUELCELL 2005-47031,
  proceeding to appear in Third International
  Conference on Fuel Cell Science, Engineering and
  Technology, May 23-25, 2005, Michigan.

5
Introduction

• Problem statement
• Suitability of the compact heat exchangers as the
  intercooler

In terms of volume, pressure drop, weight, etc,.
6
Problem Statement

• Purpose of this study
• Analysis of two types of intercoolers in PEMFC
  systems

Case study 1 Plate-fin intercooler
Case study 2 Tube-fin intercooler
(a) (b) Figure 2. Compact heat exchangers
(a) plate-fin and (b) tube-fin.
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Problem Statement

• System configuration

Figure 3 Components in the cathode side in PEMFC
system.
8
Problem Statement
Case study 1 Plate-fin intercooler
Additional fan (SADC24B5, 16 W in 2) is
equipped for coolant. 2 Japan Servo Co., Ltd.
http//www.japanservo.jp/
9
Problem Statement
Case study 1 Plate-fin intercooler
Surface in 3 Plain 10.27T and
12.00T Louver 3/8-8.7 and 3/4-11.1 Strip 1/
4(s)-11.1 and 1/2-11.94(D) 3 Kays, W. M., and
London, A. L., Compact Heat Exchangers, 3rd ed.
McGraw-Hill, 1984.
10
Problem Statement
Case study 2 Tube-fin intercooler
Table 2. Conditions of the tube-fin intercooler.
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Problem Statement
Case study 2 Tube-fin intercooler
Table 3. Combination of geometries, material and
coolant in tube-fin intercooler.
Al Aluminum, SS Stainless steel
12
Analysis Method

• e-NTU method
• Dimensionless parameter
• Heat exchanger effectivenesse
• eq/Cmin(Th,i-Tc,i)
• q Heat transfer rate
• Cmin Heat capacity rate (mcp) in minimum flow
• Number of transfer units NTU
• NTU UA/Cmin
• Heat capacity rate ratio C
• CCmin/Cmax

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Analysis Method

• Solving procedure of size problem by e-NTU method
• Step 1. Calculate e from the specified inlet and
  outlet temperatures, then C, as well.
• Step 2. Determine NTU for known e and C for the
  given flow arrangement from the e-NTU formula.
• Step 3. Calculate the required heat transfer
  surface area A from ANTU?Cmin/U.

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Analysis Method

e-NTU formulas in 3

• Plate-fin intercooler

where

• Tube-fin intercooler

3 Kays, W. M., and London, A. L., Compact Heat
Exchangers, 3rd ed. McGraw-Hill, 1984.
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Analysis Method
Referred in 3


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Analysis Method

Pressure drop for plate-fin intercooler in 3 Dp
Exit effect
Entrance effect
Core friction
Momentum effect
f Fanning friction factor - G Core mass
velocity (G ru) kg/m2s Kc Contraction loss
coefficient - Ke Expantion loss coefficient
- L Flow length m p Pressure pa rh
Hydraulic radius m
r Density kg/m3 s Ratio of free flow area to
frontal area - Subscripts i Inlet o Outlet
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Result and Discussion
Figure 3. Thermal trait of the 100 kW PEMFC
system to the intercooler. T Temperature (oC),
q Required heat transfer rate in the intercooler
(kW) Subscripts h Hot (Reactant air)
side i Inlet of the intercooler o Outlet of
the intercooler
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Result and Discussion
Volume reduction by the interrupted fin
Figure 4. Volume of the plate-fin intercooler in
case study 1. Surface Plain 10.27T and
12.00T Louver 3/8-8.7 and 3/4-11.1 Strip 1/
4(s)-11.1 and ½-11.94(D)
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Result and Discussion
Pressure increase by the interrupted fin
Figure 5. Pressure drop of the plate-fin
intercooler in case study 1. Surface Plain
10.27T and 12.00T Louver 3/8-8.7 and
3/4-11.1 Strip 1/4(s)-11.1 and ½-11.94(D)
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Result and Discussion
SS has a large volume.
Figure 6. Volume and pressure drop of the
tube-fin intercooler in case study 2.
Surface Case 1 Al Mixture, CF7.34, Case 2 Al
Mixture, CF8.72 Case 3 Al Mixture,
CF8.72(c), Case 4 SS DI water, CF7.34 Case 5
SS DI water, CF8.72, Case 6 SS DI water,
CF8.72(c)
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Result and Discussion
Large volume of plate-fin intercooler
ANTUCmin/U

• Figure 7. Volume comparison between plate-fin and
  tube-fin intercoolers.
• Tube-fin intercooler with Al, CF7.34
• Tube-fin intercooler with SS, CF7.34
• Plate-fin intercooler with Al, 12.00T

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Result and Discussion

• Figure 8. Weight comparison between plate-fin and
  tube-fin intercooler.
• Tube-fin intercooler with Al, CF7.34
• Tube-fin intercooler with SS, CF7.34
• Plate-fin intercooler with Al, 12.00T

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Result and Discussion
Table 4. The characteristics of the plate-fin and
tube-fin intercooler in PEMFC system.
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Conclusion

• Plate-fin and tube-fin intercoolers in 100 kW
  PEMFC system are analyzed.
• General
• Volume increase with system operating pressure
• Pressure drop reduction by the volume increase
• Plate-fin intercooler
• Weight reduction because of aluminum
• Space consumption at the high operating pressure
• Tube-fin intercooler
• Volume reduction because of liquid coolant
• Weight increase