Gas-liquid-liquid Three Phase Flow Patterns And Mass Transfer In Microchannel

Microreactor has great potential in the field of process intensification and the characteristics of easy to control,high reaction safety and no amplification effect.Therefore,it has caused great concerns of researchers these years.In this paper,flow patterns and mass transfer process of gas-liquid-liquid three phase flow in double T-junction microchannels are researched.Effect of the introduction of gas phase on liquid-liquid two phase flow patterns and mass transfer are researched.Experiments are conducted under different gas volume fraction,flow ratio of organic phase to aqueous phase and total flow rate of liquid phase.In this paper,30% TBP(in cyclohexane)as organic phase,deionized water as aqueous phase and atmosphere as gas phase are used to observe the flow patterns in microchannel.Firstly,flow patterns of liquid-liquid two phase flow without gas phase in microchannel are researched under different flow ratio of organic phase to aqueous phase and total flow rate of liquid phase.Three kinds of flow patterns are observed by CCD high speed camera,which are slug flow,droplet flow and parallel flow.Secondly,double T-junction microchannel is employed to research the flow patterns of gas-liquid-liquid three phase flow in microchannel.With the introduction of gas phase,gas-liquid-liquid slug flow can be formed in microchannel instead of liquid-liquid parallel flow under relatively high flow rate.Gas-liquid-liquid slug flow are divided into three kinds of flow patterns which are “bubble cutting flow”,“spontaneous break-up and bubble cutting coupling flow” and “bubble cutting and bubble break-up flow” on the basis of formation mechanism of disperse phase droplet and whether bubble break up in the formation process of gas-liquid-liquid slug flow.Flow pattern map is obtained at the end of the research about flow patterns of gas-liquid-liquid flow patterns.In this paper,the extraction system of 30% TBP(in cyclohexane)-acetic aciddeionized water is employed to research the mass transfer process of gas-liquid-liquid three phase flow in double T-junction microchannel.Effect of gas volume fraction α,flow rate ratio of organic phase to aqueous phase q and total liquid phase flow rate on mass transfer are experimentally investigated.With the introduction of gas phase,the overall volumetric mass transfer coefficient k_La is significantly enhanced and the mass transfer process can be further strengthened with the increase of gas volume fraction.The concept of enhancement factor of mass transfer E is introduced to measure the strengthen effect under different gas volume fraction.Flow rate ratio of organic phase to aqueous phase has significant influence on the overall volumetric mass transfer coefficient k_La.Under the three kinds of flow rate ratio of organic phase to aqueous phase,it can be seen that k_La(q=1:1)> k_La(q=2:1)> k_La(q=1:2).Besides,total liquid flow rate will also greatly influence the mass transfer process,the overall volumetric mass transfer coefficient k_La and enhancement factor of mass transfer E enhance with the increase of total liquid flow rate.The overall volumetric mean mass transfer coefficient k_La is correlated with flow rate ratio of organic phase to aqueous phase q,Reynolds number of gas phase Re_g and mean Reynolds number of liquid phase Re_M.