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_La 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_La is still accurately predicted by the Taylor circulation frequency in the slug.