Performance Evaluation of a PEM Fuel Cell Stack with Coolant Operating Conditions

A coolant operating condition in a fuel cell stack is an important factor to determine the temperature distribution which affects a fuel cell performance and relative humidity. In this study, the fuel cell performance were evaluated as a function of the coolant flow rate of 0.1～0.8 liter/min·cell and the coolant inlet temperature of 20～82℃ when the anode inlet relative humidity was 0, 50 and 100%. In all cases, the cathode inlet relative humidity was fixed at 100% and the constant current mode of 0.7 A/cm². The coolant inlet temperature had the proper range to maintain the optimal cell voltage. The range of proper coolant inlet temperature moves to the higher temperature regime with increasing the coolant flow rate and the anode inlet relative humidity. The cell temperatures and the temperature differences between the coolant inlet and outlet increased with increasing the coolant inlet temperature and decreasing the coolant flow rate. The optimum voltage efficiency of the stack was observed at the anode inlet relative humidity 50% when the heat removal rate was 0.40~0.65 W/cm²·cell.