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Research Papers

Local Voltage Degradations (Drying and Flooding) Analysis Through 3D Stack Thermal Modeling

[+] Author and Article Information
J. Ramousse

Institut de Recherche sur L’Hydrogène, Université du Québec à Trois-Rivières, CP 500, Trois-Rivières, QC, G9A 5H7, Canada; LOCIE, Université de Savoie, 73376 Le Bourget du Lac, Cedex, France

K. P. Adzakpa, Y. Dubé

Institut de Recherche sur L’Hydrogène, Université du Québec à Trois-Rivières, CP 500, Trois-Rivières, QC, G9A 5H7, Canada

K. Agbossou1

Institut de Recherche sur L’Hydrogène, Université du Québec à Trois-Rivières, CP 500, Trois-Rivières, QC, G9A 5H7, Canadakodjo.agbossou@uqtr.ca

M. Fournier, A. Poulin, M. Dostie

 LTE-Hydro-Québec, 600 avenue de la Montagne, Shawinigan, QC, G9N 7N5, Canada

1

Corresponding author.

J. Fuel Cell Sci. Technol 7(4), 041006 (Apr 06, 2010) (10 pages) doi:10.1115/1.4000626 History: Received April 12, 2008; Revised May 11, 2009; Published April 06, 2010; Online April 06, 2010

Temperature is a key parameter of fuel cell efficiency. In air cooled fuel cell stacks, large temperature disparities are observed. This temperature distribution has a significant influence on cell behavior in the stack, resulting in voltage disparities. The aim of this study, thus, is to correlate the temperature distribution in the stack to local voltage degradations, such as membrane drying and electrodes flooding. Indeed, the temperature has a strong impact on the water distribution in the cells because the saturation pressure is thermo-dependent. As a result, the hottest cells are prone to drying, whereas the coolest cells tend to be flooded, depending on the operating conditions. Measurements show that while drying, cell voltages decrease slowly and continuously until complete shutdown of the cells, whereas flooding results in quick voltage drops. Under drying conditions, voltage can be improved by increasing the inlet gas humidity or decrease in the stoichiometric ratio. In the case of flooding cells, purging the stack or reducing the inlet gas humidity is necessary to avoid complete shutdown of the cells. Consequently, small cell temperature variations through the stack can be responsible for large voltage variations from one cell to another. The cooling device must thus be optimized to reduce stack temperature nonuniformity.

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Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

The modeled PEM fuel cell stack and its cooling system

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Figure 2

Symmetries in the modeled PEM fuel cell stack

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Figure 3

Closed loop describing the dependence between thermal and electrochemical behaviors

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Figure 4

Thermocouples’ positions on the stack

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Figure 5

Cell thermal power versus load current—60°C operational temperature

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Figure 6

3D stack steady temperature profile—7.5 A load current—24.2°C ambient temperature

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Figure 7

Simulated temperature profiles along the stack

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Figure 8

Simulated and experimental transient temperature response

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Figure 9

Stack voltage without degradations—low level of humidification—15 A current

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Figure 10

Stack voltage under drying—low level of humidification and large flow rates—5 A current

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Figure 11

Stack voltage under flooding—high level of humidification—5 A current

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Figure 12

Stack voltage under flooding—high level of humidification—15 A current

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