The Effect of Reaction Gas Relative Humidity on the Current Density Distribution of the Cathode Flow Field Plate of PEM Fuel Cell

Abstract

The purpose of this study is to find the effect of reaction gas relative humidity (RH) on the current density distribution of cathode flow field plate in a commercial size proton exchange membrane fuel cell (PEM fuel cell) with serpentine flow field. In the experiment of this study, the RH of reaction gas was determined by setting the temperatures of the inlet reaction gas of cathode and anode to their dew point temperature (Tdp). The cell performance was evaluated by using the polarization curves and current density distribution of the cell for different relative humidity. In the experiments, the cell temperature was set to be a steady value of 65±1°N (Tcell) and the Tdp were different (40°N, 65°N and 80°N respectively to different experiment). The experiment results showed that the performance of Tdp=40°N (RH~30%) is conspicuous lower than the performance of Tdp=65°N and 80°N; but the polarization curve of Tdp=65°N (RH=100%) and Tdp=80°N (RH>100%) are not conspicuous different. The current density distribution is uniform at Tdp=65°N. The tendency of the current density is gradually increased from inlet to outlet of flow channels at Tdp=40°N, this indicates that the humidity condition in the flow channel is changed from dehydration to water balance, adversely as Tdp=80°N, the current density is gradually decreased from inlet to outlet of flow channels. This means that the humidity in the flow channel is from water balance to flooding. This work proved that the current density distribution depend on the water management, as long as it has a good thermal management.)