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 proton exchange membrane fuel cells (PEMFCs) is mainly decided by flow field of bipolar plate. The improper design of distributing channel, nonuniform gas flow distribution and current density distribution among different straight channels are the leading factors that could tremendously undermine the performance and life expectancy of the cell. However, there is lack of research focusing on distributing channel in straight-parallel flow field. In this work, a three-dimensional numerical model of PEMFC cathode flow field is developed with CFD method to investigate the effects of configuration type and width of the distributing channel on pressure distribution in distributing channel and on reactant flow distribution, pressure drop and concentration distribution in multiple straight channel. Effects of electrochemical reaction and formation of water on the flow distribution are taken into consideration. By extending one group of z-type channels 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 affect the flow, pressure drop and gas concentration uniformity. The pressure drop and the distributed flow in every straight channel have the same variation tendencies, and those of straight channels near the general outlet are higher than those of straight channels near the general inlet. Furthermore, Z-type configuration has a better pressure drop uniformity and flow uniformity than the U-type. As the width of Z-type distributing channel increases from 0.8mm to 1.8mm, the difference between the max and min flow of straight channels decreases by 29%, and the concentration difference descends 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.