CFD simulation of anisotropic heat transfer and water vapor condensation in gas diffusion layer of a fuel cell

Effective water and thermal management are crucial for maximizing the performance of proton exchange membrane fuel cells (PEMFCs). This study presents a robust non-isothermal model that integrates two-phase flow, species transport, and heat and mass transfer phenomena to investigate water generation, accumulation, and permeation mechanisms within the gas diffusion layer (GDL) of PEMFCs. Utilizing X-ray computed tomography (XCT) reconstruction, a 2D structure of the Freudenberg GDL is generated. The model incorporates anisotropic thermal conductivity, distinguishes between in-plane and through-plane K IP K TP ratios, and demonstrates its importance to temperature distribution and subsequent condensation rate within the GDL. Additionally, our parametric analysis evaluates the effects of GDL thermal conductivity, current density, operating temperature, and pressure on water condensation and transport processes in PEMFCs. Key findings include the identification of distinct phases of condensation and transport within the porous medium under varying conditions: nucleation, growth, accumulation, and mobilization. Simulation results uncovered condensation regions within the GDL, demonstrating that temperature gradients, strongly influenced by anisotropic thermal conductivity, play a critical role in water generation and transport dynamics. The study further reveals that areas beneath the land in the GDL exhibit lower temperatures, leading to elevated condensation rates and larger droplet formation within those regions. Additionally, the interconnection of condensate droplets via wetting layers emphasizes the impact of temperature distribution on water movement. This study provides deeper insight into water vapor condensation and transport mechanisms within GDLs, informing the design and optimization of GDL structures for enhanced PEMFC performance. • A 2D CFD model simulates water vapor condensation in PEMFC GDLs. • Anisotropic thermal conductivity affects temperature and condensation. • Parametric study quantifies temperature, pressure, and current density effects. • Results reveal nucleation, growth, accumulation, and mobilization.