Hydrodynamics of Taylor flow in small channels: A Review

Abstract

The improved mass transfer characteristics of Taylor flow, make it an attractive flow pattern for carrying out gas—liquid operations in microchannels. Mass transfer characteristics are affected by the hydrodynamic properties of the flow such as thickness of the liquid film that surrounds the bubbles, bubble velocity, bubble and slug lengths, mixing, and flow circulation in the liquid slugs, and pressure drop. Experimental, theoretical, and modelling attempts to predict these properties are reviewed and relevant correlations are given. Most of these refer to capillaries but there are number of studies on square channels. In general, flow properties are well understood and predicted for fully formed Taylor bubbles in a developed flow and in clean systems, particularly in circular channels. However, the presence of impurities and their effect on interfacial tension cannot be fully accounted for. In addition, there is still uncertainty on the size of bubbles and slugs that form under certain operating and inlet conditions, while there is little information for channels with non-circular cross-sections.

Microbubble moving in blood flow in microchannels: effect on the cell-free layer and cell local concentration

“…Some work has been done to visualize and measure the flow of microbubbles in small vessels. Microbubbles moving in steady state co-current flow in microchannels have been studied numerically (Taha and Cui 2006, Angeli and Gavriilidis 2008, Talimi et al 2012) and experimentally (Thulasidas et al 1997, Angeli andGavriilidis 2008). Bubble flow and lodging in capillaries have been observed in vivo by Samuel et al (2012).…”

Surface geometry, miniaturization and metrology

“…If the shape of the pipe is changed, then this also causes profound effects. If the capillary number falls below 0.04, then the shape of the cross section can dominate, although the surface roughness does not appear to have as much effect if the pipe or channel size is a millimetre or more [14]. The point here is that there are occasions where the relationship between size and the shape of the system itself can change as the size changes rather than the properties of a single element.…”

Accelerated gas-liquid visible light photoredox catalysis with continuous-flow photochemical microreactors

“…Due to the small dimensions of microreactors, a homogeneous irradiation of the entire reaction medium can be achieved which allows for shorter reaction/residence times, higher reaction selectivity and lower catalyst loadings [8][9] . Moreover, carrying out gas-liquid reactions in microreactors results in a segmented flow regime (Taylor flow) providing enhanced mixing, increased radial mass transfer and minimal axial dispersion [10][11][12][13] .…”