Effects of sub-distribution zone structure of bipolar plate on the mass transport of large-area proton exchange membrane fuel cells

Sub-distribution zone of the flow field plays an important role in distributing gas reactants and removing liquid products in large-active area proton exchange membrane (PEM) fuel cells. This study evaluates the effects of sub-distribution zone of PEM fuel cells with the active area of 300 cm(2) based on a three-plus-one-dimensional (3D+1D) model. A new structural design of sub-distribution zone, namely, mixed structure distribution zone (MSDZ) is proposed and compared with the classic dot matrix distribution zone (DMDZ) and forced shunt distribution zone (FSDZ) design regarding pressure drop, gas distribution uniformity and cell performance. It is found that FSDZ and MSDZ design distribution uniformities are improved by 90.4 % and 55.5 %, compared to DMDZ design. The cell with the MSDZ design reaches an optimal value of 0.647 V, attributed to the reduction in mass transport voltage loss. Subsequently, based on structure characteristics of FSDZ and MSDZ designs, the effects of the rib/channel width ratio in sub-distribution zone are explored. It is found that primary shunt affects the overall distribution and secondary shunt regulates the localization. Finally, the cell performance of the three types of sub-distribution zones is compared under different humidification conditions. Results show that the cell with MSDZ design demonstrates a power density increased by 4.0 % (0.05 W cm(-2)) and 7.6 % (0.09 W cm(-2)) compared with that with DMDZ design at high and low humidification conditions, respectively.