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

Abstract

The mathematical description of liquid water flooding in the gas channel (GC) of a polymer electrolyte fuel cell (PEFC) at the macro scale has remained a challenge up to now. The mist flow assumption in the GC has been commonly used in previous numerical studies. In this work, a one-dimensional (down-the-channel) macroscale phenomenological model for the liquid water flooding in the cathode GC is developed based on several reasonable assumptions. We focus on the operating conditions with fully humidified inlet air on the cathode side. Some simplifications are introduced to obtain a manageable numerical model. A series of case studies are conducted to investigate the effects of droplets and various operating parameters on the liquid water flooding in the GC. The results show that the gas drag force at the film-gas interface significantly enhances the film flow along the GC corners. Based on a proposed droplet model, we can capture key scenarios of liquid water flooding in the GC under different operating conditions like varying stoichiometry, current density and cell temperature. We find that droplets in the GC mainly contribute to the gas pressure loss and water flooding in the GC, which should be depressed for better water management. At last, a proper selection of the GC sidewall contact angle is found to be critical to a better water management in the GC.

A new approach to modelling water flooding in a polymer electrolyte fuel cell

“…That can be justified by the fact that high gas flow rates in the GC will remove emerging liquid water droplets effectively. Otherwise, water coverage effect [31,32] will be of concern which is beyond the scope of the present study. At the side boundaries, no-flux conditions are assumed.…”

Liquid Water Scavenging of PEMFC Contaminants

“…The penetration model readily applies to the water drops in the flow field channel. 36 However, for the liquid water in the gas diffusion electrode, 37 the penetration model no longer applies as the gas velocity is significantly reduced within the solid porous structure with a pore characteristic dimension of the order of or less than 100 μm.…”

“…The penetration model readily applies to the water drops in the flow field channel. 36 However, for the liquid water in the gas diffusion electrode, 37 the penetration model no longer applies as the gas velocity is significantly reduced within the solid porous structure with a pore characteristic dimension of the order of or less than 100 μm.38 This difference significantly impact contaminant scavenging dynamics and it will be shown that the product liquid water in a PEMFC is always saturated by the contaminant greatly simplifying analysis.A model is proposed for the water scavenging effect inside PEMFCs. A time scale analysis of the different processes within the PEMFC revealed that the contaminant saturates water droplets in the gas diffusion electrode.…”

Discrete-Particle Model to Optimize Operational Conditions of Proton-Exchange Membrane Fuel-Cell Gas Channels

“…A phenomenological model 36 accounted for droplet and corner film conditions in channels with momentum exchange with the air but did not track the droplets explicitly. In another study, 37 the gas channel was coupled to a MEA where droplet dynamics were simulated including transport of oxygen, allowing accurate prediction of PEFC operation compared to experimental data.…”