Abstract
A new design scheme is proposed for twisting the walls of a microchannel, and its performance is demonstrated numerically. The numerical study was carried out for a T-shaped microchannel with twist angles in the range of 0 to 34π. The Reynolds number range was 0.15 to 6. The T-shaped microchannel consists of two inlet branches and an outlet branch. The mixing performance was analyzed in terms of the degree of mixing and relative mixing cost. All numerical results show that the twisting scheme is an effective way to enhance the mixing in a T-shaped microchannel. The mixing enhancement is realized by the swirling of two fluids in the cross section and is more prominent as the Reynolds number decreases. The twist angle was optimized to maximize the degree of mixing (DOM), which increases with the length of the outlet branch. The twist angle was also optimized in terms of the relative mixing cost (MC). The two optimum twisting angles are generally not coincident. The optimum twist angle shows a dependence on the length of the outlet branch but it is not affected much by the Reynolds number.
Highlights
Microscale fluid mixing is needed to homogenize reagents in many microfluidic systems, such as microreactors and micrototal analysis systems
The mixing performance was studied numerically, and the performance was analyzed by calculating the degree of mixing, relative mixing cost and mixing energy cost
The swirl motion is very slow compared with the rate of the channel wall twisting along the outlet branch
Summary
Microscale fluid mixing is needed to homogenize reagents in many microfluidic systems, such as microreactors and micrototal analysis systems (μTASs). Many passive techniques modify the channel wall of the outlet branch, which is the portion of a microchannel after the junction where the two fluids merge. Other examples are the AccoMix split-and-recombine technique by Panic et al [19], the FAMOS multi-lamination micromixer by Keoschkerjan et al [20], and the K-M collision micromixer by Schneider et al [21] These designs use complex elements such as multiple flow passages, 3-dimensional structures, and curved or non-straight channels. Jafari et al [22] studied a twisted channel with the Reynolds number ranging from 76.7 to 460.3 They coiled the outlet branch at a given twist angle, and showed that the mixing is enhanced with the twist angle. The mixing performance was studied numerically, and the performance was analyzed by calculating the degree of mixing, relative mixing cost and mixing energy cost
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