A study of multi-phase flow through the cathode side of an interdigitated flow field using a multi-fluid model

This work presents a study of multi-phase flow through the cathode side of a polymer electrolyte membrane fuel cell employing an interdigitated flow field plate. A previously published model has been extended in order to account for phase change kinetics, and a comparison between the interdigitated flow field design and a conventional straight channel design has been conducted. It is found that the parasitic pressure drop in the interdigitated design is in the range of a few thousand Pa and could be reduced to a few hundred Pa by choosing diffusion media with high in-plane permeability. The additional compressor work due to the increased pressure loss will only slightly increase, and this may be offset by operating at lower stoichiometries as the interdigitated design is less mass transfer controlled, which means that the overall efficiency of the interdigitated arrangement will be higher. In the interdigitated design more product water is carried out of the cell in the vapor phase compared to the straight channel design which indicates that liquid water management might be less problematic. This effect also leads to the finding that in the interdigitated design more waste heat is carried out of the cell in the form of latent heat which reduces the load on the coolant. Finally we see that the micro-porous layer might help keep the gas diffusion layer substrate dry due to a potentially higher evaporation rate caused by a combination of the Kelvin effect and a larger specific surface area compared to the diffusion layer substrate.