A two-dimensional simulation of developing laminar heat and mass transfer in fuel cell channels with uniform suction of O2and H2

Abstract

A numerical model was developed to simulate the momentum, heat, and mass transfer in the fuel cell channels at steady state and developing laminar flow with constant fluid properties. The continuity, momentum, energy, and species equations were solved for humidified air and humidified H2with constant mass flux suction boundary condition for O2in the cathode and H2in the anode channels. A finite-volume method was used to solve the equations in two-dimensional cases. Friction coefficient was related to the flowrate, whereas Nusselt and Sherwood numbers were, respectively, related to the heat and mass transfer in the flow channels. The distribution of local Nu and Sh numbers and their average values were obtained on the porous walls of the channels (electrodes). The local Nu and Sh numbers were increased with increasing the pressure and Reynolds numbers, whereas the coefficient of friction and the average Nu and Sh numbers were decreased when the pressure and Re number are increased. The mass fraction of O2and H2were decreased along the channel, except at the entrance regions, whereas the mass fraction of water vapour increased along the channel, especially on the porous wall. Solving the species equations gave: (a) the distribution of mass concentration of O2and H2and other species in the channels and on the electrode surfaces for several stochiometric ratios and different current densities; (b) the local and average Sherwood numbers in the cathode channels for O2at different stochiometric ratios, different inlet wall Reynolds numbers, and several inlet pressures; and (c) the water vapour mass fraction in both channels and the mass of liquid water if condensation occurs.