Investigation of liquid retention behavior in the flow field plate of large-size proton exchange membrane fuel cells: Effects of sub-distribution zone

For proton exchange membrane fuel cells (PEMFCs) featuring an active area exceeding 100 cm2, it is essential to incorporate a sub-distribution zone on both the inlet and outlet sides of the flow field plate to ensure optimal reactant distribution. However, the outlet sub-distribution zones improve liquid water removal resistance and cause cell performance degradation. This study quantitively described the water removal with time and velocity in a straight channel and evaluated the effects of sub-distribution zone for structural optimization. A three-dimensional (3D), two-phase model using the volume of fluid (VOF) method was used to investigate the dynamic liquid retention behaviors in channel with and without sub-distribution zone. The result shows that the liquid retention ratio varies exponentially with time and gas velocity under the liquid-gas shear stress. Meanwhile, it was found that the gas stagnant area created by barriers in the sub-distribution zone significantly enhances liquid retention. Therefore, this study compared the removal capacity in different sub-distribution zones and concluded that liquid removal can be accelerated by improving the breaking up and appropriately reducing the gas stagnant area. The proposed droplet-shaped barrier could serve as an effective water management method for large-size PEMFCs.