Effect of Compression on the Water Management of a Proton Exchange Membrane Fuel Cell With Different Gas Diffusion Layers

Abstract

The gas diffusion layer (GDL) plays an important role in maintaining suitable water management in a proton exchange membrane fuel cell. The properties of the gas diffusion layer, such as its porosity, permeability, wettability, and thickness, are affected by the shoulders of the bipolar plates due to the compression applied in the assembly process. Compression therefore influences the water management inside fuel cells. A two-phase fuel cell model was used to study the water management problem in a proton exchange membrane fuel cell with interdigitated flow channels. The effect of the compression on the fuel cell performance was numerically investigated for a variety of GDL parameters. This paper focuses on studying the water management of fuel cells under compression for various types of gas diffusion layers. First, the deformation of a gas diffusion layer due to compression applied from the shoulders of the bipolar plates was modeled as a plain-strain problem and was determined using finite element analysis (FEA). The porosity and the permeability of the gas diffusion layer were then recalculated based on the deformation results. Next, the deformed domain from the FEA model was coupled with a fuel cell model, and the effects of the compression during the assembly process on the water management and fuel cell performance were studied for gas diffusion layers with different thicknesses, porosities, and compressive moduli. It was found that the deformation of the GDL results in a low oxygen concentration at the reaction site. The saturation level of liquid water increases along the flow direction, and is higher when the compression effect is considered in the simulation.

Investigation of effects of non-homogenous deformation of gas diffusion layer in a PEM fuel cell

“…There exists a transitional region, that is, a nonlinear porosity distribution zone in the GDL region corresponding to the interface between the channel and the shoulders, a linear porosity distribution zone above the shoulders, and a constant porosity distribution zone above the middle part of the channels for the cases when an assembly pressure is applied. A similar nonlinear porosity distribution zone caused by the compression was also found in most of the available GDL models . Unfortunately, the impact of such nonlinear porosity distributions in the GDL has not been well investigated in the literature.…”

“…Non‐linear deformations of the GDL under various assembly pressures were obtained in the numerical work; however, the properties of the non‐linear porosity distribution were not implemented in the CFD investigations . A remarkable numerical work was presented by Shi et al , who investigated water management under inhomogeneous compression coinciding with the calculated non‐linear porosity. That study reported that the presence of liquid water could result in a non‐uniform distribution of the porosity and permeability in the GDL.…”

Experimental measurement of effective diffusion coefficient of gas diffusion layer/microporous layer in PEM fuel cells

“…More importantly though, is its role to evenly distribute the reactants to the reaction sites and to provide water management [24,25]. This explains the use of porous material in the design of the GDL; the void area provides a region for the free diffusion of gaseous species and the removal of the reaction products, while the solid is used as a transport medium for the electrons to and from the reaction site.…”

The Effect of Clamping Pressure on Gas Diffusion Layer Performance in Polymer Electrolyte Fuel Cells

“…Higher compression decreases the contact resistance between the GDL and the plates (FFP) 5, 8–11, however, it also decreases the porosity and transport ability 4, 12, 13. This has been studied mathematically and experimentally 14–16.…”