Numerical analysis of gas-surface scattering effect on thermal transpiration in the free molecular regime

The microscopic reversibility of gas-surface collisions is discussed and analyzed using the direct simulation Monte Carlo method for different scattering kernels. A testing procedure for the reversibility analysis is described. Then, the thermal transpiration phenomenon is studied numerically for free molecular flow through short and long capillaries using Maxwell, Cercignani-Lampis, and Epstein scattering kernels. Comparison with experimental data shows that the Cercignani-Lampis and Epstein kernels allow a more accurate description of non-isothermal internal rarefied gas flows than the commonly used Maxwell model.