Mass transfer characteristic in the formation stage of gas-liquid segmented flow in microchannel

In this paper, the mass transfer characteristic in the formation stage of gas-liquid segmented flow in microchannel was investigated. Modified T-junction microchannels with differing contact angles were applied as the microdevices. The length of formed gas slug was determined firstly. An in situ method was developed to measure the mass transfer characteristic. The results showed that the initial length of gas slug with mass transfer was much smaller than that without mass transfer. The slug formation time was in the range of 0.2-0.4 s and the mass transfer during the formation stage could contribute around 30-40% of the total transferred solute. The overall mass transfer coefficient during the slug formation stage was in the range of 1.4-5.5 x 10(-4) m/s. The comparison between the experimental results and the calculated data by diffusion model indicated that the recirculation flow in the gas slug significantly intensified the mass transfer with the enhancement factor in the range of 5-15. A correlation equation was developed to predict the enhancement factor, considering both the influences of the surface renewal and the moving speed of the gas phase. The calculated data was in good coincidence with the experimental results. (c) 2012 Elsevier B.V. All rights reserved.