Mass transfer evaluation of full-scale PEMFC and flow field optimization based on the brachistochrone principle

A crucial aspect of high-performance PEMFC design is to enhance cathode mass transfer. In this study, a full-scale 3D simulation model for proton exchange membrane fuel cells was established. The periodic brachistochrone flow field (PBFF) for PEMFC was designed based on the brachistochrone principle, and a comprehensive analysis of heat and mass transfer characteristics was conducted. Multiple evaluation metrics were employed to assess the thermal and mass transfer characteristics of PBFF thoroughly. Additionally, to overcome the limitations of the conventional Pearson Correlation Coefficient (PCC) analysis in PEMFC research, the segmented-PCC method and V–O2 angle were innovatively proposed to enable a quantitative evaluation of concentration polarization characteristics. The results indicated that PBFF significantly enhanced mass transfer capability. At 3.0 A cm−2, the voltage of PBFF was increased by 5.31 %, the net power density was enhanced by 5.15 % and the oxygen concentration improved by 64.2 % compared to the parallel flow field. Through comprehensive evaluation, PBFF demonstrated superior mass transfer performance over the sine wave flow field and opposed sinusoidal wave flow field, particularly in effectively mitigating concentration polarization under high current density conditions. The concentration polarization severity in each case was quantitatively evaluated through the newly proposed segmented-PCC method and V–O2 angle, verified their universality and accuracy.