Rarefied gas flow through a long tube at any temperature ratio

Abstract

The mass flow rate of a rarefied gas through a long capillary caused by small pressure and temperature gradients has been calculated based on the s-model for the diffuse specular gas-surface interaction in the range of the rarefaction parameter from 0.005 to 50. A simple method of calculation of the thermomolecular pressure effect and the thermal creep caused by a large temperature ratio have been elaborated. Numerical calculations of both phenomena for the temperature ratio T2/T1=3.8—usually realized in experiments—have been carried out. It has been determined that the nonlinear thermomolecular pressure effect does not depend on the temperature distribution along the capillary. The nonlinear thermal creep has been calculated for two different temperature distributions along the capillary. A dependence of the creep on the temperature distribution has been found. It has been shown that the application of the linear theory based on the average rarefaction parameter to the gas flow at a large temperature ratio gives a significant error.