Lattice Boltzmann simulation of separation phenomenon in a binary gaseous flow through a microchannel

TL;DR

This study uses the lattice Boltzmann method to investigate gas separation phenomena in binary mixtures flowing through microchannels, revealing how molecular mass, pressure, and rarefaction influence separation efficiency.

Contribution

It applies the lattice Boltzmann method with diffuse-bounce-back boundary conditions to analyze separation in microchannel flows, highlighting effects of molecular mass ratio, pressure, and Knudsen number.

Findings

Separation is more pronounced in He-Ar than Ne-Ar mixtures.

Increasing pressure ratio weakens separation.

Higher Knudsen number enhances separation due to rarefaction effects.

Abstract

Gas separation of a binary gaseous mixture is one of characteristic phenomena in the micro-scale flows that differ from the conventional size flows. In this work, the separation in a binary gas mixture flows through a microchannel is investigated by the lattice Boltzmann method with a diffuse-bounce-back (DBB) boundary condition. The separation degree and rate are measured in the He--Ar and Ne--Ar systems for different mole fractions, pressure ratios, and Knudsen numbers. The results show that the separation phenomenon in the He--Ar mixture is more obvious than that in the Ne--Ar mixture at the same mole fraction owing to the larger molecular mass ratio. In addition, the increase in the pressure ratio reduces the difference in the molecular velocities between the two species, and the separation phenomenon becomes weaker. However, the gas separation is enhanced with an increase in the Knudsen number. This is because the resulting rarefaction effect reduces the interactions between the gas molecules of the two species, and thus increases the difference in the molecular velocity.