Impacts of inhomogeneous clamping force on local performance and liquid water formation in polymer electrolyte fuel cells
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A two dimensional, half-cell, non-isothermal, multi-phase model of a polymer electrolyte fuel cell (PEFC) is developed. The model accounts for the acting clamping force on the cell with accompanying effects on gas transport properties and contact resistances. Spatial variations of anisotropic structural and physical properties of gas diffusion layers (GDLs) in both in-plane and through-plane directions are considered. Designed mechanistic model is compared and validated with the experimental data for voltage-current characteristics and channel-rib current density distribution for the first time. Significant changes are observed in local gas and water concentrations as well as current density profiles with respect to cell compression and humidity ratios of entrant gases. Compression exacerbates the liquid saturation under the rib in consequence of porosity and permeability reduction. Under compression, phase change rate increases in the cell; degree of supersaturation under the channel escalates leading to higher condensation rate while degree of undersaturation under the rib increases leading to higher evaporation rate.