Numerical investigation of cold-start behavior of polymer-electrolyte fuel-cells from subzero to normal operating temperatures – Effects of cell boundary and operating conditions

In this study, we performed transient cold-start simulations of polymer-electrolyte fuel-cells (PEFCs) under a wide range of PEFC operating temperatures, from subzero (−20 °C) to normal operating temperatures (80 °C). For these wide temperature range transient simulations, the cold-start model developed in a previous study is enhanced by including ice-melting phenomena and additional constitutive relationships. The model successfully predicts various stages of PEFC cold-starts, i.e., ice formation/growth, constant ice accumulation with undersaturated vapor, ice melting/membrane hydration, and membrane dehydration. In addition, the results for simulations performed under various cold-start operating conditions clearly address the effects of key cold-start factors such as cathode stoichiometry, external thermal boundary condition, inlet relative humidity, startup temperature, and co- and counter-flow configurations on PEFC cold-start behavior, especially ice freezing/melting and membrane hydration/dehydration processes. This numerical investigation attempts to develop effective cold-start strategies that can simultaneously suppress both ice formation/growth and anode dry-out, thereby ensuring rapid and stable startup of a PEFC from subzero temperatures.