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Article

Water and Thermal Balance in PEM and Direct Methanol Fuel Cells

[+] Author and Article Information
Michael G. Izenson

 Creare Incorporated, P.O. Box 71, Hanover, NH 03755mgi@creare.com

Roger W. Hill

 Creare Incorporated, P.O. Box 71, Hanover, NH 03755

J. Fuel Cell Sci. Technol 1(1), 10-17 (Apr 21, 2004) (8 pages) doi:10.1115/1.1782918 History: Received January 26, 2004; Revised April 21, 2004

A key consideration for portable power systems is that they must operate simultaneously at water balance (no external water supply) and thermal balance (controlled temperature). Water and thermal management are intimately linked since evaporation is a potent source of cooling. This paper presents the basic design relationships that govern water and thermal balance in polymer electrolyte membrane (PEM) fuel cell stacks and systems. Hydrogen/air and direct methanol fuel cells are both addressed and compared. Operating conditions for simultaneous water and thermal balance can be specified based on the cell’s electrochemical performance and the operating environment. These conditions can be used to specify the overall size and complexity of the cooling equipment. The water balance properties can have strong effects on the size of the thermal management equipment required.

Copyright © 2004 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Control volume boundary for analysis

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Figure 2

Flow rates that determine water accumulation rate

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Figure 3

Stack heat removal mechanisms for an HAFC over a range of cell temperatures (S=2.5, ambient conditions of 0 percent and 100 percent relative humidity at 30°C)

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Figure 4

Direct stack cooling approach

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Figure 5

Fluid temperatures in direct stack cooling

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Figure 6

Condenser cooling approach

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Figure 7

Fluid temperatures for condenser cooling

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Figure 8

Temperature profiles for condenser and stack cooling

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Figure 9

Water and heat balance temperatures for a range of air flow rates (dry (0 percent) and saturated (100 percent) ambient air at 30°C)

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Figure 10

Comparison of HAFC and DMFC cooling requirements (baseline conditions, see Table 1)

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Figure 11

Generalized heat exchanger sizing for HAFCs (baseline conditions from Table 1 except for stoichiometric ratio, S)

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Figure 12

Effects of cathode pressure on HAFC thermal management (baseline conditions from Table 1 except for cathode pressure, Pc)

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Figure 13

Generalized heat exchanger sizing for DMFCs (baseline conditions from Table 1 except for stoichiometric ratio S)

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Figure 14

Effects of ambient humidity and stoichiometric flow ratio on DMFC exchanger size (baseline conditinos from Table 1 except for stoichiometric ratio, S, and ambient relative humidity, φa)

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Figure 15

Capacity rate ratio and thermal effectiveness for typical HAFC

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Figure 16

“F Factors” for crossflow heat exchangers (from Rohsenow and Choi (12))

Tables

Errata

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