Nearly free molecular heat transfer from a sphere

[摘要] Consider a sphere immersed in a rarefied monatomic gas withzero mean flow. The distribution function of the molecules at infinityis chosen to be a Maxwellian. The boundary condition at the body isdiffuse reflection with perfect accommodation to the surface temperature.The microscopic flow of particles about the sphere is modeledkinetically by the Boltzmann equation with the Krook collision term.Appropriate normalizations in the near and far fields lead to a perturbationsolution of the problem, expanded in terms of the ratio ofbody diameter to mean free path (inverse Knudsen number). The distributionfunction is found directly in each region, and intermediatematching is demonstrated. The heat transfer from the sphere is thencalculated as an integral over this distribution function in the innerregion. Final results indicate that the heat transfer may at firstincrease over its free flow value before falling to the continuum level.

[发布机构] University:California Institute of Technology;Department:Engineering and Applied Science

[关键词] Applied Mathematics