Multi-sub-inlets at cathode flow-field plate for current density homogenization and enhancement of PEM fuel cells in low relative humidity

Abstract

Multi-sub-inlets are proposed at the cathode flow-field plate (FFP) of a polymer electrolyte membrane (PEM) fuel cell to improve the current density homogeneity and overall cell performance. The cathode main inlets andsub-inlets arefed with humidified and dry air, respectively, for appropriate membrane hydration and enhanced water removal to maintain thecathodetotalflow rateat the same relative humidity. The influences of the number of sub-inlets and the sub-inlet flow rate (the amount of air from the sub-inlets) on the overall cell performance with cathode reactant relative humidity (RHc) of 0%, 10%, and 20% are numerically investigated using a 3D multiphase fuel cell model. Compared with the conventional parallel FFP design, a multi-sub-inlet parallel FFP design can relieve oxygen maldistribution, improve water removal ability and dissolved water content, and maintain a low pressure drop, increasing the homogeneity of current density and overall cell performance. The numerical results also indicate that a reasonable increase in the sub-inlet flow rate for upstream sub-inlets can further benefit the maximum power density while maintaining the homogeneity of oxygen distribution. Multi-sub-inlet parallel FFP designs with RHc of 10% and 20% exhibit no significant differences in the distributions of internal physical quantities and cell performance, although 10% RHc saves water for air humidification.