Simulation of separative gaseous molecular flow through porous membrane with DSMC method

摘要

Recently Direct Simulation Monte Carlo (DSMC) method increasingly has been used to simulate the gas flow in micro channels and rarefied gas flows. This method on the basis of particle approach, continuously has been developed for gaseous mixtures. Gaseous isotopic separation is an important process in nuclear industries. In this paper, using DSMC method, isotopic separation of a gaseous molecular flow through a porous membrane is investigated. In gaseous diffusion technology, the molecules of a lighter isotope would pass through a porous barrier of the convertor more readily than those of a heavier isotope. In this work, the effect of operating parameters on isotopic separation of gaseous molecular flow is studied. The DSMC method is utilized to evaluate the separation of gaseous components in a binary mixture ((SF6)-S-32&(SF6)-S-34). A detailed explanation of the theory is carried out, and a fitting element of membrane with proper boundary conditions is introduced. The effect of Knudsen number (Kn) on local separation factor is evaluated and verifications are shown. The simulation results prove that a gas separation is not formed in the continuous flow and it is formed only for the molecular stream of the binary mixture. It is shown by Kn increment (0.1-0.8), the amount of light component concentration increases in downstream. Also, the separation factor for Kn = 0.1 is calculated 1.001778 and this value reaches 1.004604 for Kn = 0.8. From results the enchantment of the separation factor is demonstrated and local concentrations are reported.