Water Management of PEM Fuel Cell Systems Based on the Humidity Distribution in the Anode Gas Channels

A proper water management is important for an efficient operation of a polymer electrolyte membrane (PEM) fuel cell system. The humidity distribution in the anode gas channels is highly dependent on the cathode humidity and the resulting transmembrane water transport. Therefore, it can be assumed that the cell humidification is optimal when the relative anode humidity is nearly 100% and homogeneously distributed. In contrast to state-of-the-art approaches, this study focuses on the humidity distribution on anode side in consideration of the anode recirculation loop. Therefore, a macroscopic 1D+1D simulation model was developed, which simulates humidity profiles along the gas channels with consideration of the transmembrane water transport and the anode gas recirculation. This study shows the impact of relevant input parameters, such as pressure, stoichiometry and cathode inlet humidity. Furthermore, the results show that it is possible to reach a nearly homogeneous humidity distribution along the anode gas channels for automotive fuel cell systems. This can be achieved through appropriate operation conditions, e.g., suitable combination of pressure and stoichiometry, and supportive flow directions of the gases and the coolant. The analysis was made for fuel cells operating at full load at system relevant conditions with and without external humidification.