Practical aspects of gas mixture separation using turbomolecular pump: Numerical study

Abstract

Present paper uses Direct Simulation Monte Carlo method to perform numerical assessment of turbomolecular pump (TMP) performance when applied to separation of mixtures of gases with disparate masses. The problem is studied on example of Neon–Argon mixture. Several features, distinguishing present problem from classical vacuumation application of TMP, are highlighted. It is shown that in contrast to vacuumation, the optimal separation performance is achieved at low rotation speeds of turbines (around 50–200 m/s and lower), intermediate rarefaction rates ($\delta$ around 1–10) in the device, as well as intermediate values of accomodation coefficients on the surface (around 0.5). Increase in the number of stages in device demonstrated the highest boost in performance, leading to exponential growth of separation factor. It was also shown that combination of low rotation speeds (50 m/s), intermediate rarefaction rates ($\delta \approx 1-10$) and high number of stages ($N\approx 50$) in the device appears to be viable in practice in terms of mechanical stress and heating, experienced by blades of turbines.