Transient Heat and Mass Transfer in a Reacting Cerium Dioxide Medium Exposed to Direct High-Flux Irradiation

A numerical heat and mass transfer model is presented for a porous medium of cerium dioxide exposed to direct high-flux irradiation and undergoing thermal reduction. The model  couples conduction, convection and radiation heat transfer modes to the chemical kinetics of the non-stoichiometric reduction of cerium dioxide while allowing for local thermal non-equilibrium between the solid and gas phases. The Rosseland diffusion approximation is applied to solve for internal radiative transport in the medium, with the spectral radiative characteristics obtained for selected morphological configurations of the medium with high porosities and polydispersed cerium dioxide grains. The finite volume method with an implicit time integration scheme are applied to solve the mass and energy equations in space and time to obtain transient temperature distribution and the extent of the chemical reaction. The results show the impact of grain/pore size distribution on heat and mass transfer rates, and consequently on the temperature distribution and the extent of the chemical reaction.