Direct Simulation of Liquid Water Dynamics in the Gas Channel of a Polymer Electrolyte Fuel Cell

Abstract

For better water management in gas channels (GCs) of polymer electrolyte fuel cells (PEFCs), a profound understanding of the liquid water dynamics is needed. In this study, we propose a novel geometrical setup to conduct a series of direct simulations of the liquid water dynamics in a GC. The conducting pathways in the gas diffusion layer (GDL) are simplified by three cylindrical pipes connected to a liquid water reservoir representing the catalyst layer (CL). The droplet dynamics, corner film dynamics, and the competition between the film and droplet flows in the GC are explored in detail. The results show that the three-phase contact line plays an important role in resisting the gas drag force for a droplet movement in the GC. The gas drag force can dominate the film flow along the GC corners, and a proper selection of the contact angle of the GC sidewalls is necessary to balance two requirements: increasing the film removal ability and removing the water clogging fast. The competing mechanisms of the droplet and film flows give us the possibility to regulate liquid water flow into GCs, and maybe lead to a better water management in GCs. Finally, the results from this work also serve to provide insights into the development of a phenomenological model for the liquid water flooding in GCs.

One-Dimensional Phenomenological Model for Liquid Water Flooding in Cathode Gas Channel of a Polymer Electrolyte Fuel Cell

“…Qin et al 29 studied the effect of the sidewall contact angle on the film flow at the GC corners by means of direct simulations. They concluded that larger contact angle of the hydrophilic sidewalls was beneficial to the film removal at the GC corners.…”

“…This is a reasonable assumption under low gas flow rates. 8,9,29 Governing equations.- Fig. 3 depicts the assumed idealized liquid water distribution in the GC cross section, which is separated into film (including two symmetric parts) forming at the hydrophilic GC corners, as well as droplet sitting on the hydrophobic GDL surface (i.e.…”

Pore-Network Modeling of Water and Vapor Transport in the Micro Porous Layer and Gas Diffusion Layer of a Polymer Electrolyte Fuel Cell

“…In the literature, there have been many pore-scale numerical studies of liquid water transport in the GDL ([2, [16][17][18] many thereof) and gas channels (GCs) [19]. Recently, evaporation was also included in the pore-network modeling [2,20] for understating its role in water management.…”

Water Transport in the Gas Diffusion Layer of a Polymer Electrolyte Fuel Cell: Dynamic Pore-Network Modeling

“…This has stimulated many pore-scale numerical studies of the GDL over the past few years. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] Several distinctive features of liquid water transport in the GDL make its pore-scale modeling extremely difficult. First, a small flow rate of liquid water, with a capillary number value of around 10 −8 , causes the modeling computationally expensive.…”

“…But, the computational effort was extremely heavy. Compared to direct simulations, [29][30][31][32][33] the pore-network modeling has attracted more attention, [16][17][18][19][20][21][22][23][24][25][26][27][28] mainly because it is computationally cheap. The basic idea of a pore-network model is to first construct a pore network which can adequately represent the porous medium of interest; then, flow and transport are solved in the constructed network, usually with the help of some local rules.…”