Influence of distributing channel configuration and geometric parameters on flow uniformity in straight flow-field of PEM fuel cell 2020-01-1173
Gas distribution of PEMFC is mainly decided by flow field of bipolar plate. In study of straight parallel flow field, there is little research focusing on distributing channel. However, if distributing channel is designed improperly, there are tends to show nonuniform gas flux distribution and current density distribution which has tremendously disadvantageous effects on output behavior and lifetime of the cell. A three dimensional numerical model of PEMFC cathode flow field is developed with CFD method to investigate the effects of type and width of the distributing channel on pressure distribution in distributing channel and reactant flow flux distribution, pressure drop and concentration distribution in multiple straight channel. Effects of electrochemical reaction and formation of water on the flow distribution are taking into consideration. Furthermore, extending one group z-type channel to four groups, a new flow field for a full cell is designed. Numerical results indicate that different type and width of distributing channel do effect the flow flux, pressure drop and gas concentration uniformity. The pressure drop and the distributed flow flux in every straight channel have the same variation tendency, and those of straight channel near the general outlet are higher than those of straight channel near the general inlet. Furthermore, Z-type distributing channel has a better pressure drop uniformity and flow flux uniformity than the U-type. As the width of Z-type distributing channel increases 0.8mm to 1.8mm, the difference between the max and min flux of straight channel decreases by 29%, and the concentration difference as well. This analysis informs that the optimization design of the geometric parameters of distributing channel, such as adopting Z-type distributing channel and increasing its width, can effectively improve the gas distribution uniformity in PEMFC.