Multiscale Modeling and Simulation of Heat Transfer between Alumina Nanoparticles and Helium Gas

Multiscale modeling and simulation of heat transfer between alumina nanoparticles and helium gas is conducted. Density functional theory (DFT) simulations are first performed to calculate adsorption energies and derive pair potentials for alumina-helium system. The obtained well depths are 2.794 meV and 0.921 meV for Al-He and O-He interactions, substantially lower than the values obtained using the Lorentz-Berthelot mixing rules. Subsequently, DFT derived potentials are used to conduct molecular dynamics (MD) simulations and calculate accommodation coefficients for solid temperatures in the range of 1700-2100 K and gas temperature of 300 K. The calculated accommodation coefficients are of the order of 0.1 and are weakly dependent on the solid temperature. Predictions are within the upper bound of 0.4 obtained using Altman's model for materials and conditions considered in the present study. MD derived accommodation coefficients are then fed as inputs to a macroscopic heat transfer model to predict temporal evolution of temperature of an alumina nanoparticle placed in helium gas. The proposed model captures the temporal decay of particle temperature reasonably well until about 200 ns. The disparity between predictions and experimental data is primarily attributed to different reasons such as heating up of the gas in a confined environment and sintering and aggregation of particles.