TWIST - a numerical technique for calculating the steady-state mass fraction variation in an axi-symmetric binary gas mixture subjected to pressure gradients

Abstract

The equation for diffusion in a binary gas mixture is integrated over each of a number of elements into which the R-Z system volume is divided. The resulting equations are soluble using the TWIST programme to give the mass fraction variation through the system. The Programme is suitable for analysis of any device which utilises pressure diffusion for the separation of a binary gas mixture, the components of which have approximately equal molecular weights and is describable in the R-Z coordinate system. Applications include the centrifuge, the vortex tube and the Vortex Matrix. A knowledge of the mixture mass flow and pressure distribution throughout the system is assumed. A weakness of this method is the requirement of a fine subdivision of the system volume when such flows are large. The TWIST programme has been applied to a counter-current centrifuge and the results compared with those from Cohen's theory.