Effect of porosity gradient in cathode gas diffusion layer of polymer electrolyte membrane fuel cells on the liquid water transport using lattice Boltzmann method

Abstract

In this paper, a two-dimensional model has been developed to simulate the liquid water transport in a cathode gas diffusion layer with different porosity gradients in polymer electrolyte membrane fuel cells (PEMFCs). Due to the complexity of porous media, the simulation was carried out by lattice Boltzmann method. According to dimensionless numbers that characterize liquid water transport in porous media, simulation conditions were similar to the liquid water transfer into the gas diffusion layer of PEMFC. Different gas diffusion layers were created randomly by solid circular particles with an average diameter of [Formula: see text] and the numerical code was validated by conducting several tests. The results indicated that capillary force is the main factor in liquid water transport in the gas diffusion layer, while viscous and gravitational forces do not have a significant effect. In addition to improve the water management, the gas diffusion layer should have a positive porosity gradient, i.e. the porosity increases along the thickness. Also, under the same boundary conditions and at the average porosity (0.659), the saturation distribution curves in three porous media were compared including the gas diffusion layer with porosity gradient, the gas diffusion layer with the micro-porous layer, and the gas diffusion layer with uniform porosity. The average liquid water saturation in the gas diffusion layer with the 10% porosity gradient was 20.2% lower than in the gas diffusion layer with uniform porosity and 10.5% lower than the gas diffusion layer + micro-porous layer. Furthermore, upon elevation of the porosity gradient in the gas diffusion layer, the average liquid water saturation in the gas diffusion layer decreased. Specifically, as the porosity gradient rose from 10% to 14% and 18.5%, the average liquid water saturation values decreased to 29.8% and 38.8%, respectively compared with the gas diffusion layer with uniform porosity.

Effect of Binder and Compression on the Transport Parameters of a Multilayer Gas Diffusion Layer

“…In recent years, fuel cell assemblies with a porosity gradient have received attention from many scholars. − GDL with a porosity gradient can enhance the ability of GDL to remove water, − the bending stiffness of GDL, and its steady-state performance. − A double-layer microporous layer with a porosity gradient prepared using the double coating method was proposed by Chun et al, and the water permeability and water removal ability of GDL was enhanced. The two-dimensional liquid water transport model of cathode porosity gradient GDL was established by Habiballahi et al They found that GDL with a porosity gradient can effectively enhance the water removal ability of GDL and that the porosity of GDL near the catalytic layer should be smaller than that near the gas channel.…”

“…In recent years, fuel cell assemblies with a porosity gradient have received attention from many scholars. − GDL with a porosity gradient can enhance the ability of GDL to remove water, − the bending stiffness of GDL, and its steady-state performance. − A double-layer microporous layer with a porosity gradient prepared using the double coating method was proposed by Chun et al, and the water permeability and water removal ability of GDL was enhanced. The two-dimensional liquid water transport model of cathode porosity gradient GDL was established by Habiballahi et al They found that GDL with a porosity gradient can effectively enhance the water removal ability of GDL and that the porosity of GDL near the catalytic layer should be smaller than that near the gas channel. The multilayer GDL structure makes GDL easier to keep water in the membrane to increase ion conductivity, and the steady-state performance and voltage stability of the fuel cell are strengthened .…”

“…Although there have been some experimental , and numerical ,,,,− studies on GDL with a porosity gradient, the research on the gas transport parameters of GDL with a porosity gradient is not sufficient. Experimental studies are costly to fully evaluate the effects of binder and compression on the transport parameters of multilayer GDL, and the specific fluid flow behavior inside the GDL is difficult to obtain.…”

“…Experimental studies are costly to fully evaluate the effects of binder and compression on the transport parameters of multilayer GDL, and the specific fluid flow behavior inside the GDL is difficult to obtain. Previous numerical studies have mainly focused on the effect of GDL with a porosity gradient on fuel cell performance ,− and liquid water removal capacity, ,,, but binders and compression are not considered. Therefore, the present paper considers the binder added during the manufacturing process of GDL and the compression caused by the assembly process and conducts an in-depth investigation on the transport parameters of multilayer GDL.…”

Effect of adding simultaneous hydrophilic and microporous layers on water transport in the gas diffusion layer of polymer electrolyte membrane fuel cell

“…Many studies have been conducted on the factors affecting the dynamic water transport in the GDL. Compression under the rib, 24,[40][41][42][43][44] GDL wettability, 25,[45][46][47] structure of GDL such as porosity and pore size [48][49][50][51][52] are important parameter on water transport in GDL that is investigated in previous work.…”