A multiphase and transient model is presented to describe transport and electrochemical processes with ice formation during startup of polymer electrolyte fuel cells (PEFCs) from subzero temperatures. The model accounts for ice/frost precipitation and growth in the cathode catalyst layer (CL) and gas diffusion layer, water transport at very low temperatures, heat transfer with phase transition, oxygen transport, electrochemical kinetics, and their mutual interactions. The governing equations of mass, momentum, species, heat, and charge transport under cold-start conditions are developed in a single-domain framework and solved by a finite-volume-based computational fluid-dynamics technique. Validated by extensive experimental data, this computational model is used to predict PEFC cold-start performance as well as to reveal 3D distributions of current density, temperature, membrane water content and ice fraction in the CL. Effects of startup current density and membrane thickness are numerically explored to illustrate the utility of the model. (c) 2007 The Electrochemical Society.
