Numerical Analysis of the Effects of Processing Conditions on the Casting of High Temperature PEMFC Membrane Solutions

Polymer Electrolyte Membranes have numerous failure modes resulting from chemical, mechanical and thermal influences. The conventional state–of–the–art low temperature Nafion^® membrane is susceptible to such failures due to its sensitivity to high temperatures and the presence of carbon monoxide (CO) in the reactant streams, which poisons the platinum catalyst at low temperatures. To circumvent these problems, novel, cost-effective membranes that operate at high temperatures (>120°C) and low humidity levels, such as phosphoric acid doped polybenzimidazole (PBI/PA) membranes, have been developed. However, an optimized manufacturing process for the PBI membranes is required to negate failure mechanisms that are mechanically and thermally induced; e.g., gas cross-over due to pinholes. This paper focuses on understanding defects arising in the fluid state during manufacturing, using Computational Fluid Dynamics (CFD) techniques. Simulations are performed to understand the effects of processing conditions (substrate velocity, inlet velocity and temperature) on the quality of the cast and pressure drop through the system. It is found that processing speeds affected both the cast quality and pressure drop, while temperature only affected the pressure drop.