Numerical investigation on the improved reactant mass transport with depth-dependent flow fields in polymer electrolyte fuel cell under inhomogeneous gas diffusion layer compression

Abstract

In this work, a numerical model is developed to analyse the effects of depth-dependent reactant flow field geometry under inhomogeneous gas diffusion layer (GDL) compression on the mass transport process and performance of polymer electrolyte fuel cell (PEFC). The types of depth-dependent flow channels considered in this study are: converging channel (depth continuously decreasing) and diverging channel (depth continuously increasing), and the conventional flow field designs. The model is investigated for local and global inhomogeneity due to GDL compression. The localized inhomogeneity is introduced in the flow-field rib as well as channel regions. The results are compared for reactant concentration, water concentration, local current density, and the polarization curve for different flow channel combinations. It is observed that the availability of reactants is higher in case of converging channel design, which leads to an increase in cell performance at higher currents. However, this is subjected to GDL inhomogeneity in compression. We observe in this study that such inhomogeneity, instead of having a significant impact on cell performance, lead to minimal influence in terms of reduction in cell performance. This we observe is due to improved H2 availability at anode and reduced O2 distribution at cathode that ultimately impacts respective hydrogen oxidation reaction (HOR) and reduction in oxygen reduction reaction (ORR). This study aims to investigate the cases for altered variation in cell performance due to change in depth-dependent flow fields.