Numerical investigations on two-phase flow in polymer electrolyte fuel cells

Abstract

Numerical modeling plays an important role in understanding various transport processes in polymer electrolyte fuel cells (PEFCs). It can not only provide insights into the development of new PEFC architectures, but also optimize operating conditions for better cell performance. Water balance is critical to the operation of PEFCs, since the membrane needs to attain sufficient water for effective ionic conduction. On the other hand, too much water accumulating in PEFCs would result in mass transport limitations, which is termed as liquid water flooding. In most cases, liquid water flooding occurs in porous diffusion layers and micro gas channels at the same time. This can limit the cell performance and detract the durability of PEFCs. In this talk, I would present the frontiers of numerical modeling of PEFCs with a focus on gas-liquid two-phase transport. In addition, current challenges in numerical modeling of PEFCs will be pointed out, such as validation of two-phase Darcy’s law in gas diffusion layer and interface treatments between adjacent layers (e.g. the interface treatment between gas channel and gas diffusion layer). It also needs to be noted that modeling of liquid water dynamics in gas channels has received much attention due to its importance in water management of PEFCs. Up to now, most previous works have been focused on explicit tracking of gas-liquid water interface for providing fundamental understandings of water dynamics in gas channels. However, a macro gas channel flooding model is more required for engineering applications due to its computational effectiveness. In this talk, I would give a detailed discussion on our recently proposed gas channel flooding model (one-dimensional phenomenological model for liquid water flooding in cathode gas channel of a polymer electrolyte fuel cell, JES, 2012). At last, I shall outline some future works relating to two-phase flow modeling in PEFCs.