Heat transfer analysis of a spherical particle in rarefied slip regime

In order to investigate how far the velocity slip and temperatures jump influence the heat flux, a 3D simulation study for an incompressible slip flow around a spherical aerosol particle was performed. The full Navier-Stokes and energy equations were solved simultaneously and the slip velocity and temperature jump at the gas-particle interface were considered.GAMBIT, the companion package of commercial software FLUENT^TM, was used to build the model geometry and computational grids. A multiblock structured and body-fitted grid was considered for analyzing the flow over a single spherical particle. Incompressible ideal gas model was used to simulate density changes caused by temperature gradient near the particle surface. Gas properties such as viscosity, conductivity and mean free path were also taken variable with temperature. Nusselt number values in continuum flow regime were used as a benchmark for code verification, and reasonable agreement was achieved.The effect of Knudsen number on spherical particle Nusselt number was taken into account. It was concluded that velocity slip and temperature jump affect the heat transfer in opposite ways: a large slip on the wall increases the convection along the surface. On the other hand, a large temperature jump decreases the heat transfer by reducing the temperature gradient at the wall. Therefore, neglecting temperature jump will result in the overestimation of the heat transfer coefficient.