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A semi-empirical dynamic model with a generalized modeling framework is presented in this paper for the optimal design of a proton-exchange membrane fuel-cell system in order to bring out the importance of thermal and water management dynamics. Numerous electrochemical models exist in the literature presently predict the static and dynamic behavior at a specified operated conditions. However, those models have not considered the influence of both thermal and water management dynamics on the cell polarization and performance behavior. Hence an integrated exploration is done to illustrate the combined effect of operating temperature and membrane hydration over the steady state and dynamic behavior of the fuel-cell stack system. Benchmark data obtained from a stand-alone 5-kW Ballard fuel-cell power system using Nafion 117 membrane are taken to validate the predicted results over a wide range of operating conditions. The influence of stack-operating temperature over the membrane dynamics is investigated, and a similar trend is followed to analyze the temperature dynamics for the effect of dehydrated membrane. Thereby, the optimal operating condition of the stack is determined in terms of thermal and water management dynamics that facilitate the scale-up design of a fuel-cell stack system.
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