Heat and mass transfer in porous fuel cell electrodes

The multicomponent transport of gases through the cathode of a proton exchange membrane (PEM) fuel cell and the heat transfer effects caused by the exothermic chemical reaction at the membrane are simultaneously investigated. Two-dimensional cross-sections of the porous electrode normal to the gas flow at different locations from the inlet to the outlet are considered and finite-difference solutions of the temperature, gas density and component mass fractions are obtained. The non-linear algebraic system resulting from the discretisation of the governing equations and boundary conditions is solved using a line by line iterative procedure. The numerical results obtained for various operating conditions and design parameters show that the transport of oxygen to the membrane is dominated by diffusion and that at the membrane the oxygen mass flux and the temperature can vary considerably from inlet to outlet. Regions of water vapour oversaturation, where condensation is likely to occur, are identified from the results of the water vapour partial pressure and the temperature.