Numerical study on cell performance and local transport phenomena of PEM fuel cells with novel flow field designs

In this work, a novel style of straight flow channel tapered in height or width is proposed to improve the efficiency of fuel utilization for PEM fuel cells. Fuel channels of various height and width taper ratios are numerically analyzed to understand their effects on fuel transport characteristics and cell performance. Influences of the liquid water formation on the transport phenomena and cell performance are included in the numerical model. The present results demonstrated that, with the tapered channel designs, the flow area contraction along the flow channel leads to increase in fuel velocity and thus enhances the fuel transport through porous layers, fuel utilization, and the capability of the liquid water removal. The results also reveal that the cell performance can be improved by either decreasing height taper ratio or increasing width taper ratio. If the power loss due to pressure drop is not considered, the performance of the fuel cell with the tapered flow channels is consistently improved with height taper ratios decreased and width taper ratio increased. With the pressure loss considered, however, the best performance can be obtained at the height taper ratio (Λ_x) of 0.5 and the width taper ratio (Λ_z) of 1.8 among the taper ratios studied in the present work.