Monte Carlo Simulations to Determine Effective Gas Diffusivity of an Actual Porous Medium Image Obtained From Focused Ion Beam Scanning Electron Microscopy

Abstract

Computer simulation methods have been widely used to study the effective transport properties of porous media. Simulation methods such as Monte Carlo (MC) have been used to characterize the randomness associated with such media. Most of these simulations have been carried out in artificially generated porous media represented as random pack of spheres or randomly arranged cylindrical fibers. In the present work, we apply MC simulation to images of an actual porous medium, obtained by using Focus Ion Beam Scanning Electron Microscopy (FIB SEM). The porous medium under consideration is the porous electrode of Solid Oxide Fuel Cell (SOFC). The effective gas diffusivity of the SOFC electrode is calculated based on mean square displacement method. The simulations are performed initially on a 2D image and are further carried out on a 3D image. For the validation of the numerical method, the porosity of the electrode is calculated and is used for the computation of the effective diffusivity by Bruggeman equation. In such case, the porosity is calculated by Hit and Miss MC approach and is further validated with the porosity values available in the literature. This work also addresses the effect of tessellation of solid surfaces in discrete geometries on the calculation of effective transport properties. Such computation of effective properties from the actual porous media geometry can be further used in the cell modeling and optimization of different components of the SOFC.