Investigating the Dispersion Characteristics of High-Viscosity Gas–Liquid Systems in Capillary-Embedded Ultrasonic Microreactors

Aiming at the low mass transfer efficiency of conventional reactors dealing with highly viscous gas–liquid systems, this work proposes a novel capillary-embedded ultrasonic microreactor (CEUM) based on an ultrasonic field and microscale effect for enhancing the mass transfer performance. The results show that the formation of bubbles in the channel is the result of a combination of multiple forces. As the ultrasonic power increased, the flow pattern gradually shifted from a bubble flow to a Taylor bubble flow. In addition, ultrasound increases the bubble size, generation frequency, and gas flow rate, and this trend becomes more pronounced with increasing ultrasound power. Lastly, the periodic contraction–expansion phenomenon of the bubbles was observed and revealed a sinusoidal evolution of the bubble sizes, a phenomenon that significantly perturbs the flow field in the liquid phase, which, in turn, facilitates the gas–liquid mass transfer. This study is presented to provide a promising method of enhancement for dispersion and mass transfer in highly viscous gas–liquid systems.