Mixing of a split and recombine micromixer with tapered curved microchannels

Abstract

We demonstrate a novel parallel laminar micromixer with two-dimensional staggered curved channels with tapered structures. Dean vortex flows are produced in curved rectangular channels by centrifugal forces. The split structures of the tapered channels result in the uneven split of the main stream and the reduction of the diffusion distance of two fluids. Furthermore, when one stream is injected into the other the impingement effects increase the mixing strength. Cross-sectional concentration distributions and particle trajectories are utilized to examine the flow characteristics inside the curved microchannel numerically. To evaluate the mixing performance of the designed micromixer, four different designs of a curved channel micromixer are introduced for the purpose of comparison. The mixing index of the staggered curved-channel mixer with a tapered channel is 20% higher than those of the other curved-channel mixers: i.e., the staggered curved-channel mixer with sudden contracted channels, the staggered curved-channel mixer with uniform channel width and the continuous curved-channel mixer. However, a comparison of the pressure drop penalty for the mixing is also reported. The pressure drop of the staggered curved-channel mixer with a tapered channel is about 50% higher than those of the other two staggered curved-channel mixers. The effects of various Reynolds numbers (Re) and channel configurations on mixing performances are investigated in terms of the experimental mixing indices and the computational interfacial patterns. It appears that the Dean vortex and split and recombine (SAR) effects provide improved mixing when the Re is increased above 5. At the Re of 50, the channel length necessary for mixing to be achieved is 5 times shorter compared to the case where the Re equals 1. The comparison between the experimental data and numerical results shows a very similar trend.