Numerical Determination of Two-Phase Material Parameters of a Gas Diffusion Layer Using Tomography Images

Abstract

In this paper, we give a complete description of the process of determining two-phase material parameters for a gas diffusion layer: Starting from a 3D tomography image of the gas diffusion layer the distribution of gas and water phases is determined using the pore morphology method. Using these 3D phase distributions, we are able to determine permeability, diffusivity, and heat conductivity as a function of the saturation of the porous medium with comparatively low numerical costs. Using a reduced model for the compression of the gas diffusion layer, the influence of the compression on the parameter values is studied.

Computation of Thermal Conductivity of Gas Diffusion Layers of PEM Fuel Cells

“…on the heat treatment of the fibers. This may explain the apparent discrepancy between the results for structural models of carbon paper by (Becker et al, 2008) and where thermal conductivity values of 17 W/ m K and 130 W/ m K were used, respectively.…”

“…A carbon cloth is shown as sample X-ray computed tomography (Ostadi et al, 2008;Pfrang et al, 2010) as well as synchrotron based tomography (Becker et al, 2008;Becker et al, 2009) have been used for imaging of gas diffusion layers at resolutions below 1 µm. Also membranes and membrane electrode assemblies (Garzon et al, 2007;Pfrang et al, 2011) have been imaged by X-ray computed tomography and even functioning fuel cells have been imaged by synchrotron-based methods and soft X-ray radiography e.g.…”

“…As more accurate thermal conductivity data is required, one further approach is the computation based on 3D structure data (Becker et al, 2008;Pfrang et al, 2010;Zamel et al, 2010). Fig.…”

Influence of threshold variation on determining the properties of a polymer electrolyte fuel cell gas diffusion layer in X-ray nano-tomography

“…The latest laboratory-based X-ray nano-tomography can achieve a resolution of 400 nm with detectability of 100-200 nm (McNulty et al, 1995;Warwick et al, 1998;Cai et al, 2000;Parkinson and Sasov, 2008). Recently, X-raymicro-tomography has been used to quantify liquid water saturation distribution in porous GDLs and determining the Q1 two-phase material parameters with a sub 10 mm resolution (Becker et al, 2008;Sinha et al, 2006). The latest report suggests that nano-tomography (Nano XCT, US: Xradia Corp.) can be used to reconstruct the porous catalyst layer (CL) of fuel cells at sub-micron resolution in order to study the changes in membranes after transient operation (Garzon et al, 2007).…”

Microfluidics of imbibition in random porous media

“…The macroscale model was based on Darcy's law and mass conservation, where the permeability and capillary pressure must be calculated as a function of saturation level from a microscopic model. On that level, instead of directly solving the two-phase flow problem, a pore morphology model was used [13]. The pore morphology model determined the fluid-gas interface geometry by inserting different sizes of spheres in the porous media and thus provides the capillary pressure through the Young-Laplace equation.…”