CFD investigation of the cross flow phenomenon in a serpentine flow field for pefc

Reactants distribution over the active area plays a key role in the performance of PEM fuel cell. The flow path that is designed to uniformly distribute fuel and oxidant over the active area, has also to respect some geometrical constraints such as the active area shape. Serpentine layout has been proven as efficient design especially at cathode, due to the fluid motion established in the flow field. A convective flow through the gas diffusion layer, also called cross flow, has been demonstrated to be responsible for a better PEM fuel cell performance using serpentine flow channels. As highlighted in previous studies the intensity of the cross flow is affected by several parameters, such as the thickness and permeability of the gas diffusion layer and the serpentine path length, even though the correlation between the cross flow intensity and the fuel cell active area shape factor (MEA width/height) has never explored before. In this work a numerical and experimental study has been carried out to investigate the effect of the active area shape factor on the cross flow intensity and its effect on the fuel cell performance. Three-dimensional CFD simulation, including electrochemical aspects, has been performed for two different serpentine flow paths extending over the same active area but different in shape factor. The effect of reactants stoichiometry and humidification on the fuel cell performance have been also envisaged. Numerical computations has shown that cross over flow intensity is higher in the flow field with the lowest area shape factor. In terms of electrochemical performance, this flow field operates better at higher current density because the high intensity of cross flow enhances reactants concentration and improves water removal from the gas diffusion layer. Experimental tests have also been performed for a comparison with numerical results.