Influence of local porosity, local permeability, and contact resistance between the gas diffusion layer and the bipolar plate, on the performances of a polymer electrolyte membrane fuel cell

摘要

For the past years, many studies have been conducted to understand and analyze the behavior of fuel cells in order to improve this source of energy. In our present work, we are interested in polymer electrolyte membrane (PEM) type fuel cells (FC) often encountered in transportation; we investigate the effects of FC compression on the properties of the cell. We first analyze the influence of different pressures (applied on graphite or steel bipolar plates BP) on the porosity, permeability, and deformation of the gas diffusion layer (GDL) and then we evaluate these local fields of GDL porosity and permeability. Moreover, a new numeric approach based on fluid mechanics is elaborated to study the effects of mechanical compression of the GDL on the performance of the cell through the variation of the local pressure at the GDL/BP interface. Finally, we model the contact resistance between the GDL and the BP and then calculate the local electrical resistivity field at this interface. These effects of FC compression are incorporated into a multi-physical model that considers the chemical phenomena and the effects of mechanical compression of the fuel cell to correctly simulate and report the polarization and power density curves and to conclude about the performance of the cell. It was found that the GDL porosity and permeability as well as the pressure at the interface between the GDL and the BP vary locally with compression and should not be kept constant. Also, it was found that the compression applied on the FC decreases the contact resistance and the effect of contact resistance at the GDL/BP interface is smaller than that of electrolyte resistance which is a source for current limitation.