Is there any difference between time of mixing and residence time for mixing inside microchnnel? also how to calculate it by COMSOL or analytically?
Dear Imran Shah,
I think time of mixing in your question refers to the time required for fluids to mix, which is caused by several factors depending on the Re value, fluids properties, micromixer design, ...etc. On the other hand, residence time for mixing refers to the time required for fluids to mix at very low Re value, where fluids mix with each other due to the molecular diffusion. In several cases, you will observe a behavior like the one demonstrated in the Figure. This can be explained as follows:
When the two fluids are pushed from each microchannel towards the mixing element, the fluids will start mixing due to laminar flow recirculation that generates transverse velocity components around the corners (depending on the design) of the mixing element. However, the transverse flow is negligible at low Re values, which means that mixing is dominated by the molecular diffusion as a result of the low velocity and the high residence time.
More details can be found in my paper:
Article Frequency-Controlled Wireless Passive Thermopneumatic Micromixer
Thank you Marwan Nafea for your quick response. i will read the reference paper.
Hello can anyone explain the difference by calculation by taking some example?
Finally i understand the residence time for micro-mixers. The formulas are T=L/u where T= residence time L=main mixing channel length and u= average velocity and u= Re* v/D where Re= Reynolds number D=hydraulic diameter of channel different for different cross-sectional area and V= viscosity. Thanks to all for your answers. But still i am not clear about time of mixing and its formulas.
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