Water Transport Simulation in a Gas Diffusion Layer of PEMFC Using Lattice Boltzmann Method

Abstract

The water transport in a gas diffusion layer (GDL) has been investigated using two-dimensional lattice Boltzmann (LB) simulation. The LB model is developed to simulate the dynamic behavior of liquid water and enables to visualize the water-invasion process through micro-pores in GDL. To investigate the effect of rib structure on water invasion process in GDL, two different cases (i.e., with and without rib structure) are compared. The numerical model is verified by the comparison of the flow permeabilities in GDL. The validation result indicates that the LB model can properly predict the permeability of GDL and enables to simulate the water transport behavior in the GDL. The reconstruction of GDL is established by randomly placing the particles in GDL and ignoring the GDL deformation due to clamping force. The results of LB simulation confirm that the liquid water transport inside GDL is strongly governed by capillary force and the rib structure greatly impacts on the water transport behavior. The rib structure influences on the location of water breakthrough by comparing the simulation results of two different cases. This is due to the higher resistance force underneath the rib, resulting in the change of flow path which preferentially selects the lower resistance force. The water saturation level under the channel is higher than that under the rib caused by the suppression of growth of water cluster. After water breakthrough, the liquid water distribution under the channel has little change, whereas that under the rib keeps stretching for a while. The result indicates that a careful control of rib structure would enhance the water removal from the GDL. Therefore further studies for the optimum design of rib structure are needed. In an operating PEMFCs, the mechanism of water transport and wetting characteristics play an important role on flooding behavior. Therefore the results of the present study would contribute to the novel design for better water removal and flooding alleviation from the GDL.