Numerical and experimental investigation of 3D flow field bipolar plates for PEMFCs by metal 3D printing

The bipolar plate is one of the core components of a proton exchange membrane fuel cell (PEMFC). Its flow field structure directly affects the drainage and heat dissipation performance of the cell, as well as the transmission and distribution of the reaction gas. Compared with conventional 2D flow fields, novel 3D flow fields can provide superior gas–liquid mass transfer performance, significantly improving the performance of PEMFCs. However, traditional manufacturing processes fail to meet the associated molding needs, due to the complex structure of such plates. This research aims to investigate the metal 3D printing process, mass transfer law, and efficiency of 3D flow field bipolar plates, focusing on the influence of structural parameters on the gas–liquid mass transfer performance, by combining CFD multi-phase flow numerical simulations and experiments. The results indicate that the use of a 3D stepped flow field enhances the convection effect in the vertical direction due to the increase in Z-directional inflow, thus promoting oxygen transfer and reducing the accumulation of water. In particular, better gas–liquid mass transfer performance is achieved when the number of steps is 4. At 0.55 V, the measured power density of the Stepped-IV cell reached as high as 6727 W/m2, which is about 26 % higher than the conventional parallel flow field. This study provides an important technical and theoretical reference for the design and preparation of novel 3D complex flow fields.