Asymptotic analysis of anode relative humidity effects on the fastest voltage decay single cell in a stack

An anode relative humidity (ARH) model is set up to analyze the effects of anode relative humidity on the fastest voltage decay single cell in a stack. In the ARH model, the saturation pressure related to relative humidity is established by anode pressure drop instead of using conventional empirical equation in Fluent model. First, a three dimensional (3D) model incorporating geometry and grids is established. Second, experiment is conducted including a 10-cell stack, single cell distribution and test schematic. Third, both experiment and simulation results are discussed in detail. Furthermore, for the fastest voltage decay single cell, a comparable analysis among ARH model, Fluent model and experiment is carried out at the different anode relative humidities (55%, 70%, 85% and 100%). The results show that FC10 (the furthest distance single cell from gas inlet) voltage decay is the fastest in the stack. ARH model applied to FC10 voltage decay shows good agreement with Fluent model and experiment. ARH model accuracy increases by 47% compared to Fluent model. And the error between ARH model and experiment is reduced to 3% at 350 mA/cm² for 100% anode relative humidity. FC10 species molar concentration distributions inside fuel cell in each case are non-uniform.