Two-dimensional numerical modelling of a direct methanol fuel cell

The results of a numerical simulation of a direct methanol fuel cell (DMFC) with liquid methanol feed are presented. A two-dimensional numerical model of a DMFC is developed based on mass and current conservation equations. The velocity of the liquid is governed by gradients of membrane phase potential (electroosmotic effect) and pressure. The results show that, near the fuel channel, transport of methanol is determined mainly by the pressure gradient, whereas in the active layers, and in the membrane, diffusion transport dominates. ‘Shaded’ zones, where there is a lack of methanol, are formed in front of the current collectors. The results reveal a strong influence of the hydraulic permeability of the backing layer KpBL on methanol crossover through the membrane. If the value of KpBL is comparable to that of the membrane and active layers, electroosmotic effects lead to the formation of an inverse pressure gradient. The flux of liquid driven by this pressure gradient is directed towards the anode and reduces methanol crossover.