Liquid–liquid extraction in twisted micromixers

• The twisting was applied on the micromixer to enhance liquid–liquid mass transfer.
• Water (Cu) + D2EHPA + kerosene system used for mass transfer analysis.
• Flow patterns at various flow rates, with and without the twist, were studied.
• Results showed that KLa and E were increased by increasing the twisted ratio.
• Performance ratio was proposed for economic evaluation of the proposed micromixer.

This paper reports a study on mixing performance and mass transfer enhancement between two immiscible liquid phases in proposed twisted micromixers. The experiments conducted for three different twisted micromixer and results were compared with a plain microchannel. Water (Cu) + D2EHPA + kerosene system, was chosen for evaluation of mass transport. The fluid flow patterns were compared in different studied twisted micromixers at the Reynolds number ranging from 76.7 to 460.3 at the same aqueous to organic flow rate. Moreover the effect of the twisted ratio on the overall volumetric mass transfer coefficient (KLa) and the extraction efficiency (E) was studied. Results show that creating more twist in micromixer is more effective for liquid–liquid mass transfer, but more energy is required to pump fluids to microchannel. Performance ratio was proposed to evaluate this matter from economic aspect. As far as the twisted ratio has direct effects on extraction efficiency and pressure drop, it was used as a design variable for determining the most appropriate channel geometry. The results show that the extraction efficiency as well as pressure drop increased with increase in twist ratio. Therefore, in order to reach the highest performance ratio an optimum value for twist ratio was proposed.

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