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. T he velocity of the liquid is governed by gradients of membrane phase potent ial (electroosmotic effect) and pressure. The results show that, near the f uel channel, transport of methanol is determined mainly by the pressure gra dient, whereas in the active layers, and in the membrane, diffusion transpo rt 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 K-p(BL) on methanol cros sover through the membrane. If the value of K-p(BL) is comparable to that o f the membrane and active layers, electroosmotic effects lead to the format ion of an inverse pressure gradient. The flux of liquid driven by this pres sure gradient is directed towards the anode and reduces methanol crossover.