The effect of channel-to-channel gas crossover on the pressure and temperature distribution in PEM fuel cell flow plates

The air flow in a simplified model of the flow plate and adjacent diffusion layer of a PEM fuel cell has been numerically studied. The flow plate has been assumed to have serpentine flow channels with a square cross-section. It has been assumed that the flow in the porous diffusion layer can be modelled by using Darcy's law. It has also been assumed that there is a uniform rate of heat generation at the base of this diffusion layer. The three-dimensional flow and temperature distribution in the flow plate-diffusion layer combination has been numerically studied by writing the governing equations in dimensionless form and solving the resultant equations using a commercial software package. As a result of the pressure drop along the flow channel, there can be crossover of air through the porous diffusion layer from one part of the channel to another. The conditions under which this crossover becomes important and the effect this crossover on the pressure distribution in the channel and the temperature distribution in the flow plate has been examined in this study. Attention has been given to flow plates having a single serpentine channel. Various numbers of flow passes through the plates have been considered these flow passes leading to what are effectively a series of parallel serpentine channels in the plate. The effects of Reynolds number, relative flow plate material thermal conductivity, dimensionless permeability of the diffusion layer and of flow channel geometry on the channel flow and the plate temperature distribution have been numerically examined and related to air crossover.