(469j) Dispersion and Mass Transfer of Microbubble in Capillary Embedded Step T-Junction Microchannel

The size of microbubble is an important parameter in microchannels, especially for absorption of low concentration gas. Smaller microbubble can provide higher surface to volume ratio and shorter mass transfer distance, which can significantly improve the mass transfer. In this work, a kind of capillary embedded step T-junction microchannel was used to obtain microbubbles with small diameter. Capillary with 50μm inner diameter is embedded into the gas passage of T-junction. The DEG-water system was used as continuous phase, and nitrogen was used as dispersed phase. Liquid phase shears the gas phase vertically, and the step can significantly intensify continuous phase flow focusing. Different regimes have been studied, such as Dripping regime, Squeezing regime and dripping-squeezing regime. Monodispersed microbubbles with diameter lower than 100μm can be easily obtained in this microchannel. The dispersion law of this microchannel has been studied, and a correlation was found as d/w=0.28Ca^-0.28（Q_L/Q_G）^-0.29 , which could predict the bubble size well. Further, the mass transfer performance of microbubble size lower than 100μm has been investigated experimentally. The mass transfer is quite good under this condition, and the K_la can be up to 800 s^-1.The results also indicated that the mass transfer coefficient is inversely proportional to the diameter of microbubbles.