Transient behavior of liquid water distribution in a lung-inspired PEM fuel cell

Abstract

Water management is a crucial aspect of hydrogen fuel cell operation because inadequate management can lead to significant losses in mass transport, limitations in oxygen diffusion, and membrane durability issues. This study investigates the impact of various operational conditions on the initial formation and evolution of liquid water content and distribution, as well as water evacuation, within a lung-inspired PEM fuel cell with a 50 cm2 active area. A series of experiments were conducted to assess the effects of cell pressure, relative humidity of the reactant (anode and cathode), temperature, and cell current density. Neutron imaging was utilized as it has been shown to be an effective technique for quantitative analysis of water distributions. The results indicate that water initially appears in the sponges located in the central region of the cathode, but due to considerable back-diffusion, water predominantly accumulates in the area of the anode channels in contact with the cathode sponges. The amount of water in the cell increases faster when the relative humidity of the cathode and anode is higher, and high pressure and low temperature also favours water accumulation. After the experiments, the design of the cathode sponge facilitates faster water evacuation compared to the anode side. Overall, this study offers valuable insights into the behaviour of water in a hydrogen fuel cell and the factors influencing its distribution.