Simulation of gas-liquid flow in direct methanol fuel cells

A two-dimensional two-phase model considering methanol crossover has been established and the phenomena of two-phase flow and mass transfer in the anode are paid special attention to in this paper. The model takes measures to calculate gas and liquid velocity separately and investigates the effect of gas and liquid velocity on mass transfer and fuel cell's performance. Quantitative investigations show results below: Parasitic voltage resulted from methanol crossover makes the practical open circuit voltage much lower than theoretical value. Since gaseous volume fraction in diffusion layer and catalyst layer is very high under high current density, the generated gas may block the transfer of liquid fuel and become key factor that hinders the performance of fuel cell. The gas-liquid counter flow in diffusion and catalyst layer can help vent the generated CO₂ and drive liquid fuel to catalyst layer. Lower permeability of the porous media weakens gas-liquid counter flow and deteriorates the performance of the fuel cell.