FITTING A THREE DIMENSIONAL PEM FUEL CELL MODEL TO MEASUREMENTS BY TUNING THE POROSITY AND

A three-dimensional, computational fluid dynamics (CFD) model of a PEM fuel cell is presented. The model consists ofstraight channels, porous gas diffusion layers, porous catalystlayers and a membrane. In this computational domain, most ofthe transport phenomena which govern the performance of thePEM fuel cell are dealt with in detail.The model solves the convective and diffusive transport of thegaseous phase in the fuel cell and allows prediction of theconcentration of the species present. A special feature of themodel is a method that allows detailed modelling and predictionof electrode kinetics. The transport of electrons in the gasdiffusion layer and catalyst layer is accounted for, as well as thetransport of protons in the membrane and catalyst layer. Thisprovides the possibility of predicting the three-dimensionaldistribution of the activation overpotential in the catalyst layer.The current density dependency on the gas concentration andactivation overpotential can thereby be addressed. The proposedmodel makes it possible to predict the effect of geometrical andmaterial properties on the fuel cell?s performance. It is shownhow the ionic conductivity and porosity of the catalyst layeraffects the distribution of current density and further how thisaffects the polarization curve.The porosity and conductivity of the catalyst layer are some ofthe most difficult parameters to measure, estimate and especiallycontrol. Yet the proposed model shows how these two parameterscan have significant influence on the performance of the fuel cell.The two parameters are shown to be key elements in adjusting thethree-dimensional model to fit measured polarization curves.Results from the proposed model are compared to single cellmeasurements on a test MEA from IRD Fuel Cells