Dynamic Thermal, Transport and Mechanical Model of Fuel Cell Membrane Swelling

When polymer electrolyte membrane materials are exposed to liquid water, they swell and distort. This frustrates the process of depositing liquid catalyst ink directly onto the membrane. We present a model predicting the transient compositional, thermal, and mechanical response of a membrane undergoing changes in water content. The model describes coupled heat and mass transfer and solid mechanics and is capable of describing the large changes in size and shape exhibited by a swelling membrane. Simulation results are presented for sorption and desorption and for the process of drying a saturated piece of membrane with an aqueous coating applied. We suggest that the well-established discrepancy in the rate of sorption and desorption may be partially due to pressure-driven diffusion effects absent in other models but present in ours. We also demonstrate that the model can represent the transient curling behavior of a membrane undergoing nonuniform changes in water content. The model will later be used to predict manufacturing defects caused by swelling-induced wrinkling.