Mass transfer characteristics and concentration field evolution for gas-liquid Taylor flow in milli channels

The results of the recent experimental work performed by Butler et al. (2016, 2018) are analysed based on the dominant phenomena: (i) small scale convection by means of Taylor vortices in the liquid slugs and (ii) diffusion in lubrication film. A main result shown here is that the Taylor circulation frequency is able to reflect the global mass transfer rate in gas-liquid Taylor flow through an almost linear relationship, which emphasizes the interest of the circulating motion in the slug, and gives a very simple correlation to predict the k(L)a value (at large Schmidt number). A mechanism of flow behavior during the bubble formation at the T-mixer is proposed as a possible explanation of unexpected concentration areas (called islands). However, despite of these unusual concentration field structures in these cases, the mass transfer rate coefficient k(L)a is still accurately predicted by the Taylor circulation frequency in the slug. (C) 2019 Elsevier Ltd. All rights reserved.