Experimental Evaluation of Air Flow Effect in Gas Diffusion Layer on PEM Fuel Cell Performance

This paper investigated the effects of gas and liquid water flow on the performance of a polymer electrolyte membrane (PEM) fuel cell using cells to allow direct observation of the phenomena in the cell and measurements of the local current density and the local pressure loss. The experimental results to compare the separator type indicated the effect of cross-over flow in the gas diffusion layer (GDL) under the lands of serpentine separators on cell performance and the potential of straight channel separator to achieve a relatively-uniform current density distribution. To evaluate the cross-over flow under the land of serpentine separators, a simple circuit model of the gas flow was developed. This analysis showed that slight variations in oxygen concentration caused by the cross-over flow under the land affect the local and overall current density distributions. It was also shown that the establishment of gas paths in the deep layer of GDL by the channels filled with condensed water is effective for stable operation at low flow rates of air in the straight channels.