Through-Plane Water Distribution in a Polymer Electrolyte Fuel Cell: Comparison of Numerical Prediction with Neutron Radiography Data

A multidimensional mathematical model is presented for simulating the coupled phenomena of gaseous fuel/reactant flows, species (including liquid water) transport, heat transfer, hydrogen oxidation, and oxygen reduction reactions in a polymer electrolyte fuel cell (PEFC). The present work focuses on elucidating water distribution in the through-plane direction, in particular across the membrane electrode assembly (MEA) and gas diffusion layer (GDL). Two-dimensional model predictions are computed numerically and compared with available experimental data from neutron radiography or imaging. Using the same set of model parameters, reasonably good agreements are obtained quantitatively between the computed water profile in the MEA-GDL component and the neutron-imaging data reported by two separate research groups, and qualitatively between model prediction and the data from another (third) group. Case-study simulations are carried out for PEFC operation at various temperatures, relative humidities, and current densities. It is found that liquid-water content is lower at higher cell temperatures due to greater water evaporation and stronger water diffusion in the vapor phase, as expected. Without strong water diffusion in the vapor phase, the liquid-water profiles are found to increase with current density in the cathode GDL but indicate a complex trend in the anode. Effect of varying GDL thermal conductivity on water distribution is also examined. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3498997] All rights reserved.