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Mixing patterns in water plugs during water/ionic liquid segmented flow in microchannels

Dore, V; Tsaoulidis, D; Angeli, P; (2012) Mixing patterns in water plugs during water/ionic liquid segmented flow in microchannels. Chemical Engineering Science , 80 334 - 341. 10.1016/j.ces.2012.06.030. Green open access

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Abstract

Circulation patterns and mixing characteristics within water plugs in liquid/liquid segmented flow were investigated by means of micro-Particle Image Velocimetry. Experiments were carried out in a glass microchannel with circular cross-section of 100 μm radius using [C4mim][NTf2] ionic liquid as the carrier fluid. A T-junction was used as inlet, while mixture velocities varied from 0.0028 m/s to 0.0674 m/s. Two main circulation vortices were found within the plugs while at intermediate mixture velocities two additional secondary vortices appeared at the plug front. The mixing rate was locally quantified by means of the non-dimensional circulation time, which was calculated across the plug length. Consistently with the circulation patterns, the non-dimensional circulation time was found to have a profile along the direction of the flow that mirrors the shape of the plug, with a minimum at the axial location of the vortex cores (where the circulation velocity is maximum at the channel centre) while it tended to infinity towards the liquid/liquid interfaces. For all the experiments the minimum value of the circulation time fell within the range of 1.00–1.75. For increasing mixture velocities (i.e. increasing Ca) and sufficiently long plugs (εIL=0.4) a general decrease (i.e. higher mixing rate) of the circulation time minimum was found, although the behaviour was rather complex. On the other hand, the circulation velocity linearly increased as the Ca number (mixture velocity) increased.

Type: Article
Title: Mixing patterns in water plugs during water/ionic liquid segmented flow in microchannels
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.ces.2012.06.030
Publisher version: http://dx.doi.org/10.1016/j.ces.2012.06.030
Language: English
Additional information: This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Keywords: Multiphase flow, Microfluidics, Mixing, Liquid-liquid, Ionic liquids, PIV
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering
URI: http://discovery.ucl.ac.uk/id/eprint/1349518
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