In-situ estimation of water transfer parameters in a proton exchange membrane fuel cell

Abstract

A reduced model to describe steady state transport of water through a PEM fuel cell is proposed. It includes three rigorously estimated parameters: the effective gas diffusion coefficient of water vapor in hydrogen, of water vapor in air and of water in sorbed phase in the membrane. First, it is proved that the parameters are well decorrelated. Then, uncertainty on estimates is calculated by simulating an experiment with random noise. Finally, the parameters are estimated as a function of the average humidity. It is observed that the gas phase diffusion coefficients do not depend on humidity. The effective diffusion coefficient in sorbed phase decreases slightly with increasing average relative humidity. It is shown that the effect of electrodes on water transport is negligible by comparing the water fluxes through an MEA and a membrane alone. A temperature gradient is imposed between the two plates and allows to obtain the condensation of water on one side of the membrane. A discontinuity of the water flow through the MEA is observed and results are interpreted by an increase of the effective diffusion coefficient in sorbed phase and/or by an increase of the water content of the membrane in contact with liquid water.