A hierarchical multiscale model of heat transfer between nano-alumina powder and noble gases

Hierarchical multiscale modeling and simulations are conducted to study heat transfer between nano-alumina powder and noble gases. The noble gases considered in this study are helium, argon, and xenon. Density functional theory (DFT) computations are conducted to predict adsorption energies of noble gases on alumina slab for eight different sites. Using the adsorption energy data, new interatomic pair potential functions that describe gas-slab interactions are developed. Classical molecular dynamics (MD) simulations are then conducted to compute energy accommodation coefficients (EACs) for a gas temperature of 300 K and slab temperatures in the range of 1000–2800 K. For a solid alumina slab, the computed average EACs are 0.16, 0.40 and 0.36 for helium, argon and xenon, respectively. An abrupt jump in the EAC is observed upon melting of the slab. For a liquid alumina slab, the computed average EACs are 0.29, 0.63, and 0.66 for helium, argon, and xenon, respectively. The observed EAC trends are reasoned by independently probing the effects of potential well-depth and gas atom mass. The MD derived EACs are fed as inputs to the transition regime heat transfer model to predict the time evolution of the temperature of nano-alumina powder in noble gas environments. The capability of the hierarchical multiscale model and the validity of the Altman's EAC bounds are assessed by comparing the model predictions with the experimental data.