Optimization of variable cross-sectional flow channel parameters for fuel cells: Numerical analysis and distributional uniformity evaluation

The bipolar plates (BPs) are the core component of proton exchange membrane fuel cell (PEMFC) stacks, and its structure has a substantial impact on the performance of the stack. Optimizing the parameters of flow channels of bipolar plates is crucial for enhancing the mass transfer of reacting gas and improving water removal capacity. In this study, three-dimensional numerical models of staggered variable cross-sectional flow channels (VCSFCs) are developed to investigate the impact of cathode humidities, contraction ratios, numbers and lengths on the performance and uniformity of PEMFC. The results show that a cathode humidity of 50 % can maximize the advantages of VCSFCs. A higher contraction ratio leads to a significant increase in pressure drop, a decrease in mass transfer capacity, and a less uniform distribution of current density and temperature compared to different numbers and lengths of variable cross-sectional structures (VCSSs). Increasing the overall gas velocity in flow channels can effectively enhance the uniformity of current density and temperature. A VCSS arrangement with a contraction ratio of 0.25, a number of 1 in each channel, and a length of 6 mm is utilized for channels with a length of 100 mm can achieve optimal results.