Abstract
The gas diffusion layer (GDL) plays an important role in the mass transfer process during proton exchange membrane fuel cell (PEMFC) operation. However, the GDL porosity distribution, which has often been ignored in the previous works, influences the mass transfer significantly. In this paper, a 2D lattice Boltzmann method model is employed to simulate the liquid water transport process in the real GDL (considered porosity distribution) and the ideal GDL (ignore porous distribution), respectively. It was found that the liquid water transport in the real GDL will be significantly affected by the local low porosity area. In the real GDL, a liquid water saturation threshold can be noticed when the contact angle is about 118°. The GDL porosity distribution shows a stronger influence on liquid dynamic than hydrophobicity, which needs to be considered in future GDL modelling and design.
Highlights
Introduction inside Gas Diffusion Layer withThe gas diffusion layer (GDL) in the proton exchange membrane fuel cell (PEMFC) is generally composed of carbon fiber substrate and micro-porous layer (MPL)
The GDL mainly ensures two mass transfer processes: (i) the reactants penetrate the GDL and reach the three-phase boundary (TPB), which is a diffusion process driven by the concentration gradient, and (ii) the water removal from the catalyst layer (CL) to the flow channel, which is known as one of the critical issues called “water management,” restricts the commercial development of PEMFC [1]
Under the conditions of high current density and high relative humidity (RH), the TPB produces excessive liquid water, which invades the pores of the GDL and decreases the porosity of the GDL [2]
Summary
The GDL in the proton exchange membrane fuel cell (PEMFC) is generally composed of carbon fiber substrate and micro-porous layer (MPL). The GDL mainly ensures two mass transfer processes: (i) the reactants penetrate the GDL and reach the three-phase boundary (TPB), which is a diffusion process driven by the concentration gradient, and (ii) the water removal from the catalyst layer (CL) to the flow channel, which is known as one of the critical issues called “water management,” restricts the commercial development of PEMFC [1]. The mass transfer polarization will seriously affect the fuel cell’s output performance due to water accumulation in the CL, GDL and gas channel (GC). The LBM (lattice Boltzmann method) was developed from the lattice gas method (LGA) in the 1990s. Unlike the traditional CFD method, the LBM has recently gained much attention as a powerful tool to simulate complex physical problems due to its advantages of capacity for investigating complicated geometries, simple implementation, high computation efficiency and easy implementation of parallel-processing [5]
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