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Sensibility study of flooding and drying issues to the operating conditions in PEM fuel cells

Keywords: Hydrogen supply modes , Modeling , Parametric sensibility study , Polymer electrolyte membrane fuel cell , Water management.

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Abstract:

Due to water management issues, operating conditions need to be carefully chosen in order to properly operate fuel cells. Because of the gas consumption along the feeding channels and water production at the cathode, internal cell humidification is highly inhomogeneous. Consequently, operating fuel cells are very often close to critical operating conditions, such as flooding and drying, at least locally. Based on this observation, the critical current, corresponding to internal cell humidification balance (acurate membrane hydration, without excess of water at the electrodes), is deduced from a pseudo-2D model of mass transfer in the cell. Using the model, a parametric sensibility study of the operating conditions is presented to analyze the cell internal humidification. Dead-end and flow-through modes of hydrogen supply are also compared. It is shown that the operating temperature is a key parameter to manage the cell humidification. Moreover, although the oxygen stoichiometric ratio has an effect on cell humidification, this influence is limited and cannot be used alone to adjust the cell humidification. Furthermore, it is shown that in some cases, humidifying the anode inlet gas is of little interest to the internal humidification adjustment. Finally, those results allow to understand the role that each operating parameter can play on the cell internal humidification. Consequently, this study is of a great interest to water management improvement in polymer electrolyte membrane fuel cells.

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