PORE-SCALE SIMULATION OF MULTI-COMPONENT GAS DIFFUSION IN THE CARBON XEROGEL NANOPOROUS STRUCTURE USING LATTICE BOLTZMANN METHOD

The gas diffusion in the carbon xerogel nanoporous structure is studied at the pore-scale using the lattice Boltzmann method in this paper. The carbon xerogel has been reconstructed by an improved diffusion-limited, cluster-cluster aggregation method, and the physical properties of the reconstructed nanoporous structure, including the porosity, the effective pore volume, and the pore size distribution, agree well with the experimental data. The diffusion of multi-component gas in the carbon xerogel nanoporous structure has been simulated. The results show that the diffusivity for argon in the carbon xerogel nanoporous structure is much slower than that for nitrogen and air. Therefore, argon is a better option to be pre-filled into the carbon xerogel to prevent its structure from ablation. Besides, a correlation to predict the required time for the gas concentration in the carbon xerogel reaching a certain value has been developed, and the correlation could offer reliable guidance to help the design of thermal insulation systems which are based on carbon xerogels.