2005 Volume 45 Issue 7 Pages 1005-1013
Recently, it was found that the performance of proton-exchange membrane (PEM) fuel cells was improved by the deposition of small magnet particles in the cathode-side catalyst layer. We developed a numerical simulation to clarify this effect, for a PEM fuel cell equipped with an interdigitated gas distributor. A two-dimensional, two-phase model was used. Cathode electrode consisted of gas diffusion layer and catalyst layer, and the latter was treated as a line. Darcy's law was used to describe the transport of the gas phase. The forces from the shear of the gas flow and of the capillary action move the liquid water through the porous cathode electrode. The magnetic field was modeled by using an equivalent magnetic field. Our numerical results show that the repulsive Kelvin forces acting on liquid water can control the liquid water flow through a porous gas diffusion layer. With increasing residual flux density of magnet particles, the velocity of liquid water near the interface of the catalyst/diffusion layers increases, the saturation of liquid water near the interface decreases, and increasing more pore space is freed for O2 transport and reactions. Therefore, the mechanism of the improvement of the cell performance by magnet particles is clarified using such a numerical model. The use of permanent magnets will be especially useful for portable fuel cell in which there is no power to supply air.
