Analysis of reactant gas transport in a PEM fuel cell with partially blocked fuel flow channels

In the present study, we propose a novel configuration of partially blocked fuel channel with baffle plates transversely inserted in the channel. The effects of the blockage with various gap ratios and numbers of the baffle plates, the fuel flow Reynolds number and the porosity of the diffusion layer on the reactant gas transport, and the pressure drop across the channel length are explored. A two-dimensional model of one-side porous-walled channel with the presence of baffle plates is considered. An approximate analysis is performed first to examine the qualitative natures of the flow in the gap region and then numerical simulations for the parametric study of the reactant gas transport in a half-cell model are carried out. The velocity field, the oxygen mass flux/flow rate reaching the catalyst layer, the concentration of the water vapor produced, the fraction of the fuel gas entering the diffusion layer, and the pressure drop at various conditions are analyzed. The results reveal that reducing the gap size and/or increasing the baffle number to enhance the reactant gas transport results in a penalty of high pressure-loss. Among the parameters considered in the present work, the gap ratio has the most remarkable impact on the variation of the pressure drop. Very high pressure-loss can be generated due to high flow resistance at a low gap ratio combined with a low gas diffusion layer (GDL) porosity. With the consideration of both high performance and reasonable pressure drop, the present results disclose that designs with the baffle gap ratio no smaller than 0.1, number of baffle plates N = 3-5, and the GDL porosity around 0.7 seem quite appropriate.