Atomistic Simulations of Thermal Energy Transfer between the Rarified Gas and Solid Surface

The scattering of gases on solid surfaces plays an essential role in many advanced technologies. When gas molecules have a mean free path comparable to or larger than the system's characteristic length, the behavior falls under rarefied gas dynamics, such as systems in high-altitude aerospace environments, vacuum technology, and nanoscale processes. Understanding heat transfer mechanisms in these environments is critical to designing and operating various engineering systems, including spacecraft, satellites, microscale devices, and vacuum-based manufacturing systems. This chapter focuses on the atomistic simulation methods for studying thermal energy transfer between rarefied gases and solid surfaces. Molecular dynamics simulations with massive gas molecules were introduced to evaluate the interfacial energy transfer between sparse helium gas molecules and iron crystals. The influence of velocity distribution of gas molecules on the interfacial thermal accommodation coefficient was investigated by molecular beam molecular dynamics simulations of helium on graphite to showcase the significance of the fast atom effect. The incident angle-resolved behaviors and the scattering process were examined for helium on graphene to provide a fundamental understanding between gas molecules and solid surfaces. Then the Monte Carlo method was used to build the connection between the angle-resolved solutions and the macroscopic energy accommodation coefficient by sampling the velocity distribution of gas molecules. This chapter should pave an avenue for the atomistic simulations of energy transfer between gas and solid surfaces.