Study On Bubble Cutting Motion Behavior And Mass Transfer Process

Gas-liquid two-phase flow,movement behavior of bubbles can not only change the velocity distribution of the fluid,but also cha nge the effect of mass transfer and heat transfer through the gas-liquid interface,which has an important influence on the gas-liquid contact process.Bubble cutting fracturing can increase atmospheric liquid phase interface,which has important research significance for improving the mass transfer efficiency of the chemical process by increasing the atmospheric liquid contact area.In this paper,the PIV technology and numerical simulation method are combined to study the cutting behavior and mass transfer process of a single bubble.PIV technology was used to capture the movement trajectory of bubbles in the cutting process,influences of bubble shape change,velocity change and mass transfer wake distribution in the cutting process under different viscos ity were analyzed.The experimental results show that there are three morphologic changes in the bubble cutting process,symmetrical cutting,asymmetric cutting and sliding through the filament.Velocity of bubbles decreases first and then increases during the cutting process.Stable velocity of the sub-bubble after symmetrical cutting is lower than that before cutting,and the decreasing amplitude of the bubble velocity is less affected by the viscosity.When the bubbles are asymmetrically cut,the velocit y of the larger sub-bubbles decreases less than that of the smaller ones.When the bubble slides through the filament,the velocity decreases first and then returns to the original stable velocity,acceleration decreases with the increase of viscosity.Mass transfer experiment was designed based on the oxidation and reduction reactions between resazurin and sodium hydroxide and glucose to capture the oxygen mass transfer wake and analyze the distribution of oxygen concentration in the cutting process.Oxygen concentration distribution is mainly located at the bottom of the bubble during the cutting process.The range of mass transfer wake before contact filament is small.With the rise of the bubble,the mass transfer wake gradually becomes longer and the concentration gradient becomes larger.After the mass transfer wake is cut with the bubble movement,the mass transfer wake range increases,while the mass transfer efficiency of smaller bubbles is higher,the oxygen components are consumed faster,and the mass transfer wake gradually disappears.Based on the VOF model,the numerical calculation model of mass transfer is established,and the mass transfer process is computerized by UDF,so as to realize the quantification of mass transfer flux.During the cutting process,the pressure,velocity and streamline around the bubble change,and the vortex structure in the liquid phase increases,and the turbulence intensity increases.For bubbles with an initial diameter greater than 10 mm,multiple cuts can be made to enhance mass transfer.The larger the wire diameter,the greater the fluctuation of bubble velocity during the cutting process.Decrease rate of bubbles decreases with the increase of wire diameter,and the decrease rate of 0.5mm wire is the largest,reaching 23%.The effect of wire diameter on CO2 dissolution is small.After the asymmetric cutting of bubbles,the volume of sub-bubbles is different,resulting in a large difference in the velocity of sub-bubbles,and the dissolution of CO2 decreases with the increase of the volume difference.