DSMC simulation of gas mixing in T-shape micromixer

Gas mixing in a T-shape micromixer has been simulated using the direct simulation Monte Carlo (DSMC) method in the present paper. The adequate mixing is considered to be obtained when the mass composition of the species, CO or N2, deviates by not more than ±1% from its equilibrium composition. The mixing coefficient was defined as the ratio of the mixing length to the main channel height. It was observed that the two gas streams started to diffuse at the inlet of the T junction before subsequent mixing. This phenomenon is quite distinguished from what have been observed in their macro counterparts. The simulation results show that with a certain inlet Knudsen number (Kn), maintaining the scale of the geometry, no difference occurs in the mixing process along the channel. As the inlet Kn increases, while the diffusion of the molecules behaves more active, the mixing coefficient decreases. Furthermore, increasing the inlet pressure will cause the mixing length to increase, since the convection effect of the gas stream is more pronounced compared with the diffusion effect. Increasing the gas flow temperature or the wall temperature can both enhance the mixing performance, while the effect of increasing the wall temperature is more significant.