Study On Formation And Mass Transfer Process Of Droplet Flow In A Microchannel

Microchemical technology is the frontier of multi-interdisciplinary field that hasthe characteristics of process intensification, easy to control, security and so on. Inrecent years, it has been widely used in micro heat transfer, micro mixing and microreaction fields. The flow and mass transfer of liquid-liquid two-phase flow are thecommon problems in the chemical process. And liquid-liquid two-phase flow hasbeen widely applied in extraction, phase transfer catalyst, emulsion preparation,organic synthesis and so on. In this paper, a new droplet flow generating device (i.e.,opposite-flowing T-shaped microchannel) has been proposed. In this T-shapedmicrochannel, the droplet flow is much easier to form and suitable for a wide range offlow ratio. Moreover, the flow patterns and mass transfer characteristics ofliquid-liquid two-phase droplet flow in this microchannel are investigatedexperimentally.Water-n-butanol is chosen for the working system of study of liquid-liquidtwo-phase flow patterns. And the fluid flow in the self-made microchannel wasobserved by CCD high speed camera, etc. Stratified flow and droplet flow wereobserved in the capillary, and slug flow and droplet flow were observed in the mainchannel. In addition, the droplet formation process, the droplet coalescence anddroplet size distribution were investigated, and the influences of two phase flowvelocity, the total flow velocity, flow ratio and the inner diameter of the main channelon the droplet coalescence and droplet size were discussed.Water-succinic acid-n-butanol is chosen for the working system, and the masstransfer characteristics of liquid-liquid two-phase droplet flow have been studied inthe present work. The influences of two phase flow velocity, the total flow velocity,flow ratio, succinic acid concentration and the inner diameter of the main channel onthe extraction efficiency and the volumetric mass transfer coefficient wereinvestigated. The extraction efficiency of8.5%-86.7%was obtained, and thevolumetric mass transfer coefficients were in the ranges of0.012-0.082s-1.Furthermore, an empirical correlation was developed to predict the volumetric masstransfer coefficients. It was found that the volumetric mass transfer coefficient isproportional to the total flow velocity of the0.53-th power, inversely proportional to the inner diameter of the main channel of the1.99-th power, and inverselyproportional to the flow ratio of the0.34-th power.