Porous Materials as Fluid Distributors in Polymer Electrolyte Fuel Cells: A Computational Performance Analysis

Commonly used ribbed flow-fields such as parallel and serpentine flow-fields in polymer electrolyte fuel cells (PEFC) exhibit limited mass transfer to the part of the diffusion and catalyst layer which is not covered by flow channels, leading to a considerably reduced reactant concentration and increased overpotential losses under the current collector shoulders. In this study, a novel concept is investigated, according to which the traditional ribbed flow delivery systems are replaced with permeable porous fluid distributors, which circumvent drawbacks such as those mentioned earlier. A complex mathematical model, including the conservation of mass, momentum, energy, species and electric current, using Butler-Volmer kinetics for electrochemical reaction rates, is numerically solved in three dimensions, to investigate the impact of different flow configurations on the performance of hydrogen fuel cells. It is found that cells with porous gas distributors generate substantially higher current densities and therefore are more advantageous with respect to mass transfer. Reduction in stack weight is another strong argument for using porous flow distributors in future applications.