Study On The Motion Characteristics And Coalescence Behaviors Of Bubbles In Microchannels

Microfluidics is an emerging technology that greatly facilitates heat and mass transfer between substances.At present,the study of bubble behavior in microchannels mainly focuses on the bubble generation process,and there is less study on the bubble motion characteristics and the coalescence at the outlet of the channel.Therefore,in this work,the motion characteristic and coalescence behaviors of bubbles in the anhydrous ethanol-air system and silicone oil-air system were investigated by experiments.In this work,the motion characteristics of bubbles were investigated in equal-width microchannels.The influencing factors of bubble generation process and flow patterns change were analyzed.The effects of two-phase rates,continuous-phase viscosity and channel size on bubble head and neck width,bubble head and neck velocity,bubble generation period,bubble generation frequency,bubble generation size,bubble generation volume and bubble motion velocity were investigated.The prediction models of bubble generation frequency,bubble generation size and bubble generation volume associated with two-phase rates,capillary number and Reynolds number in anhydrous ethanol-air system and silicone oil-air system were obtained.The forces on the bubbles during the generation process were analyzed.In this work,the coalescence behaviors of bubbles in the sudden expansion microchannels.The arrangement of bubbles before coalescence in the second stage channel was analyzed,and found that there were five flow patterns and three tightly arranged patterns of bubbles.The flow patterns and coalescence of bubbles in the first stage channel to the second stage sudden expansion channel and the second stage channel to the third stage sudden expansion channel.The ranges of bubbles size distribution at different pressures in the third stage channel were investigated,and the coalescence of two bubbles with the two coalescence types of three bubbles were observed in the third stage channel,and the factors influencing the coalescence process and velocity variation of two bubbles and two types of three bubbles were analyzed.The above study provides theoretical guidance for the prediction of bubble behaviors in microchannels,and provides reference for the design of new microchannels and industrial applications.