Modeling of two phase flow in a hydrophobic porous medium interacting with a hydrophilic structure

TL;DR

This paper presents a pore-network modeling approach to simulate two-phase water flow at the interface of hydrophobic and hydrophilic porous media, relevant for fuel cell performance optimization.

Contribution

It introduces a novel extension of pore-network models to capture mixed-wet interactions at the interface between hydrophobic and hydrophilic domains.

Findings

Model successfully simulates flow at the hydrophobic/hydrophilic interface.

Application to realistic GDL configurations demonstrates model relevance.

Provides insights into water transport mechanisms in fuel cells.

Abstract

Fluid flow through layered materials with different wetting behavior is observed in a wide range of applications in biological, environmental and technical systems. Therefore, it is necessary to understand the occuring transport mechanisms of the fluids at the interface between the layered constituents. Of special interest is the water transport in polymer electrolyte membrane fuel cells (PEM FC). Here, it is necessary to understand the transport mechanisms of water throughout the cell constituents especially on the cathode side, where the excess water has to be removed. This is crucial to choose optimal operating conditions and improve the overall cell performance. Pore-scale modeling of gas diffusion layers (GDLs) and gas distributor has been established as a favorable technique to investigate the ongoing processes. Investigating the interface between the hydrophobic porous GDL and the hydrophilic gas distributor, a particular challenge is the combination and interaction of the different material structures and wetting properties at the interface and its influence on the flow. In this paper, a modeling approach is presented which captures the influence of a hydrophilic domain on the flow in a hydrophobic porous domain at the interface between the two domains. A pore-network model is used as the basis of the developed concept which is extended to allow the modeling of mixed-wet interactions at the interface. The functionality of the model is demonstrated using basic example configurations with one and several interface pores and it is applied to a realistic GDL representation in contact with a channel-land structured gas distributor.