Pore-Scale Transport and Two-Phase Fluid Structures in Fibrous Porous Layers: Application to Fuel Cells and Beyond

Area of Science:

• Fluid Dynamics
• Materials Science
• Biomedical Engineering

Background:

• Understanding multiphase flow in porous media is crucial for applications like filtration and energy devices.
• Fuel cell gas diffusion layers (GDLs) are complex fibrous materials where liquid water management is critical.
• Pore-scale dynamics significantly influence macroscopic transport properties.

Purpose of the Study:

• To investigate two-phase flow dynamics in a reconstructed fuel cell gas diffusion layer.
• To identify dominant fluid structures and transport regimes at the pore scale.
• To develop a macroscopic model for predicting liquid transport influenced by microstructure.

Main Methods:

• Acquisition of a 3D microstructure of a fibrous material using X-ray computed tomography.
• Execution of pore-scale, two-phase flow simulations using the lattice Boltzmann method.
• Quantitative analysis of multiphase dynamics and identification of flow regimes.

Main Results:

• Three distinct transport regimes were identified: fast inertial, viscous-capillary, and stabilized flow.
• Microstructural heterogeneities induce capillary pressures, leading to unstable front displacement and capillary fingering.
• The fibrous material's morphology significantly affects pore invasion dynamics, counteracting stabilizing viscous forces.

Conclusions:

• Pore-scale variations in fibrous materials dictate complex liquid transport behaviors.
• A macroscopic model using an effective contact angle can capture microstructure-induced capillary effects.
• Findings are relevant for optimizing the design of protective face masks for pandemic mitigation.