Water balance in a polymer electrolyte membrane fuel cell (PEMFC) was investigated by measurements of the net drag coefficient under various conditions. The effects of water balance in the PEM fuel cell on the cell performance were also investigated at different operating conditions. Experimental results reveal that the net drag coefficient of water through the membrane depends on current density and humidification of feed gases. It is found that the net drag coefficient (net number of water molecules transported per proton) has values between 0.93 and −0.015 depending on operating condition, current loading and level of humidification. It was also found that the humidity of both anode and cathode inlet gases had significant effect on fuel cell performance. The results will be used to define conditions of optimal hydration of the membrane. Based on the performance and resistance measurements, optimal humidification can be achieved. The resistance of working fuel cell shows that the membrane resistance increases with the feed gas relative humidity (RH) decreased. Data obtained will be used to evaluate the transport parameters such as net flux of water through the membrane and the effective drag under various operating conditions, and further provide validation data for the fuel cell modeling and simulation efforts.

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