Study of the anisotropic permeability of proton exchange membrane fuel cell gas diffusion layer by lattice Boltzmann method

et al. 2021

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The effect of binder and compression on the transport parameters of the multilayer gas diffusion layer (GDL) is numerically studied by the lattice Boltzmann method. A stochastic algorithm is implemented to generate three multilayer GDLs with a porosity gradient and a uniform GDL, and then, the GDLs are compressed after the binder is added to obtain structures with various binder volume fractions and various compression ratios. The pore size distribution, through-plane (TP) permeability, in-plane (IP) permeability, tortuosity, and electric conductivity of the four structures of GDLs are analyzed. The pore size distributions of GDLs move toward smaller pores due to compression, and the GDL with a larger porosity gradient has a larger maximum pore size. The TP permeability decreases with the increase of compression ratio and binder volume fraction, and the TP permeability of the four GDLs decreases similarly due to compression, but the TP permeability of the multilayer GDL with a larger porosity gradient drops more due to the binder. IP permeability is slightly affected by the compression. Similar to TP permeability, the IP permeability of the multilayer GDL with a large porosity gradient decreases more due to the binder. Multilayer GDL with a small porosity gradient has a smaller tortuosity, more superior pore connectivity, and thus more outstanding gas permeability. The electric conductivity increases with the increase in compression ratio and binder volume fraction.

Section: Resultsmentioning

confidence: 99%

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

Wang

et al. 2021

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“…Because the wetting properties of the material have a negligible effect on gas flow, standard bounce-back boundary conditions are applied to both the fiber and binder surfaces. The verification of the fluid flow LB model can be found in our previous work …”

Section: Model Descriptionmentioning

confidence: 99%

“…The verification of the fluid flow LB model can be found in our previous work. 52 The D3Q7 model is employed to simulate the mass transport in GDL, and the equilibrium distribution function of the mass transport LB model and the discrete lattice velocities (c j ) need to be modified as follows: 53 ( 1, 0, 0), (0, 1, 0), (0, 0, 1),…”

Section: Compression Modelmentioning

confidence: 99%

Transport-Parameter-Based Correlations for Gas Diffusion Layers Considering Compression and Binder: An Investigation Using the Lattice Boltzmann Method

Wang

et al. 2021

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The mesoscopic three-dimensional (3D) lattice Boltzmann (LB) model is employed to investigate the transport parameters for the gas diffusion layer (GDL) of a proton-exchange membrane fuel cell, and the corresponding correlations are proposed. The effects of the binder and the compression caused by the assembly pressure on the permeability, diffusivity, and tortuosity are discussed. The GDL fiber skeleton samples are first reconstructed using the stochastic reconstruction algorithm, and samples with various binder volume fractions and various compression ratios are generated. The 3D LB model is subsequently implemented to simulate the single-phase gas flow characteristics in the GDL, and the transport parameters are calculated after the fluid reached the steady state. The simulation results indicate that the increase in the binder volume fraction and compression ratio results in a more complex GDL structure, leading to a decline in permeability and diffusivity and an increase in tortuosity. The fitted multi-factor transport parameter prediction correlations that consider fiber skeleton porosity, binder volume fraction, and compression ratio have more accurate prediction characteristics than the single-factor transport parameter prediction correlations that only consider the GDL porosity.

“…The 3D structure of the GDL is generated by a stochastic reconstruction method, the details of which are described in previous works. − The planar structure that meets the porosity requirement is selected for the 2D melting calculation, and for in-plane it is also necessary to ensure that the fiber diameter meets the set value. To investigate the effect of fiber diameter on the anisotropic melting process, the porosity of the porous structure is chosen to be 0.7.…”

Section: Mathematical Modelingmentioning

confidence: 99%

Investigation of the Ice Melting Process in a Simplified Gas Diffusion Layer of Fuel Cell by the Lattice Boltzmann Method

Jiang

et al. 2022

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Cold start is a challenge for the proton exchange membrane fuel cell, and understanding the heat transfer characteristics of solid–liquid phase change in this process is necessary. An enthalpy-based lattice Boltzmann model is established, and the heat transfer of ice melting in in-plane and through-plane of the gas diffusion layer (GDL) is studied. The effects of fiber diameter, double heat sources, and Rayleigh number are analyzed. It is found that the fiber diameter has a significant influence on heat transfer. The ice melting rate of XZ position is faster than other planes, and it has the best effect when the diameter is 8 μm. The heat transfer of different heating positions is analyzed, and it is found that the left-right-heated has the highest melting efficiency. The heat sources location has different effects on the heat transfer between the XY position (TP1) and YZ position (TP2). Although the increase of Rayleigh number can enhance the convective heat transfer, the change of melting efficiency is extremely small. The convective heat transfer intensity has no direct effect on the ice melting of GDL, and fiber plays a more critical role in the heat transfer of ice melting.