NONUNIFORM PRESSURE DIFFUSION OF A TERNARY GAS MIXTURE IN A CIRCULAR TUBE IN THE TRANSITION REGION

[摘要] References(22)A new, explicit equation for nononiforni pressure diffusion of a ternary gas mixture in a circular tube is obtained. The theory employed is based on the authors'' existing kinetic model of foursided local velocity distributions. The diffusion equation shows that transport of the individual components is expressed by a simple summation of two separated terms of diffusional and hydrodynamic flows. Validity of the equation is shown by comparison of the fluxes with those measured for a He-Ne-Ar mixture through a diffusion bridge. The diffusion equation gives a physical explanation for striking phenomena at low pressures, such as Hoogschagen''s nonequimolar counter-diffusion at a uniform pressure, diffusio-molecular pressure effect, velocity slip at the channel wall, and Knudsen''s minimum in volume flow. The concept of "diffusional momentum slip" is newly proposed. Use of this concept is effective in deriving the solutions to transport of gases at low pressures directly from the continuum theory.