Monte Carlo Analysis of Lobular Gas-Surface Scattering in Tubes Applied to Thermal Transpiration

摘要

A model of rarefied gas flow in tubes was developed which combines a lobular distr ibution with diffuse reflection at the wall. The model with Monte Carlo techniques was used to explain previously observed deviations in the free molecular thermal transpiration ratio which suggest molecules can have a greater tube transmission probability in a hot- to-cold direction than in a cold-to-hot direction. The model yields correct magnitudes of transmission probability ratios for helium in Pyrex tubing (1.09 to 1.14), and some effects of wall-temperature distribution, tube surface roughness, tube dimensions, gas temperature, and gas molecular mass. (Author)