This talk consists of two parts. In the first part, we will present the tools and methods we use to determine transport properties of porous media. In the second part of the talk we will apply these methods to simulate and analyze porous layers of a PEM fuel cell.
Central in our approach is the 3D structure model of the pore structure, represented as a 3D voxel image. Such a model can originate from a CT image of the media, segmented into solid and void parts by choice of a threshold. Or, a 3D model can be constructed virtually.
Next, various properties of the structure can be determined numerically. Some, like surface area and pore size distribution, can be determined purely geometrically.
Transport properties like diffusivity, permeability or conductivity require to solve a partial differential equation. For example, the permeability can be obtained from the solution of the Stokes equation. Even more involved is the determination of twophase flow properties. Here, we use the pore morphology method to obtain the capillary pressure - saturation relationship. A combination of this method with singlephase flow computations allows us to determine relative permeabilitiies.
As exemplary application we will consider a PEM fuel cell. In fact, the membrane electrode assembly (MEA) of a PEM fuel cell consists of several porous layers on both the cathode and the anode side: the gas diffusion layer (GDL), the catalyst layer (CL) and sometimes a micro-porous layer (MPL) in between. We will present both CT based and virtually created GDL models and show the numerically determined properties. Where available, the results will be compared with experimental data.