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Unformatted text preview: A Two-Dimensional Two-Phase Model of a PEM Fuel Cell Guangyu Lin * and Trung Van Nguyen ** ,z Department of Chemical and Petroleum Engineering, The University of Kansas, Lawrence, Kansas 66045, USA A two-dimensional, two-phase, steady-state, isothermal model was developed for a fuel cell region consisting of the catalyst and gas diffusion layers bonded to a proton exchange membrane ~ PEM ! . This model extends the previously published one-dimensional model of the gas diffusion and catalyst layers to two dimensions in order to account for the effects of the shoulder of the gas distributor and the electronic conductivity of the solid phase. The new model was validated with experimental results and then used to investigate the effect of the relative dimensions of the shoulders and channels on the cell performance. The effects of the in-plane liquid water permeability and electronic conductivity of the gas diffusion layer on cell performance were also examined. It was found that more channels, smaller shoulder widths on the gas distributor, and higher in-plane water permeability of the gas diffusion layer can enhance the transport of liquid water and oxygen, leading to better cell performance. The in-plane electronic conductivity of the gas diffusion layer was found to have minimal effect on the cell performance. However, a highly nonuniform distribution of electronic current was formed within the gas diffusion and catalyst layers when the in-plane electronic conductivity was low. © 2006 The Electrochemical Society. @ DOI: 10.1149/1.2142267 # All rights reserved. Manuscript submitted July 5, 2005; revised manuscript received October 4, 2005. Available electronically January 4, 2006. Electrode flooding is one of the major causes of poor perfor- mance of proton exchange membrane ~ PEM ! fuel cells. 1,2 A better understanding of this phenomenon is essential to the development of water management strategies. Because of the small geometry of the electrodes, it has been difficult to conduct experiments to investigate the distribution of water in the gas diffusion and catalyst layers and its effect on reactant species in an operating fuel cell. Alternatively, researchers have developed mathematical models to gain qualitative insights into the processes involved in the PEM fuel cells. Many mathematical models have been presented, but these models either treated the catalyst layer as an ultrathin interface or did not fully account for the effect of liquid water in this layer. 3-11 The authors of this paper have presented a two-phase, one- dimensional isothermal model of the cathode of a PEM fuel cell. 12 In this model, a thin-film/agglomerate approach was used to repre- sent the catalyst layer. The results clearly showed that the water flooding level in the catalyst layer was higher than that in the gas diffusion layer. This is because water is generated within the catalyst layer and removed from this layer via evaporation and/or capillary flow. Therefore, the catalyst layer should not be treated as an inter-flow....
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This note was uploaded on 10/28/2010 for the course EE 89 taught by Professor Asgarian during the Fall '10 term at Amirkabir University of Technology.
- Fall '10