Study On Bubble Regulation And Enhanced Mass Transfer In Gas-liquid Two-phase Flow

The coalescence phenomenon caused by the interaction between bubbles has a great impact on the bubble movement behavior.The bubble coalescence behavior seriously hinders the increase of gas-liquid interfacial area,and the operation behavior of liquid phase will also affect the bubble movement.The key to enhance the gas-liquid mass transfer should be based on the full understanding of bubble dynamics and fluid flow characteristics.To reduce the influence of bubble polymerization and mass transfer efficiency,this topic uses the method of combining experimental research and numerical simulation to investigate the influence of liquid viscosity on the flow characteristics of gas-liquid two-phase fluid,puts forward the bubble regulation means in gas-liquid two-phase flow,and makes an experimental study on its effect of enhancing mass transfer.The effects of different liquid viscosity and superficial gas velocity on bubble size distribution,liquid velocity vector and flow field distribution were studied by using the coupling method of computational fluid dynamics and population balance model（CFD-PBM）.It is found that the bubble size increases with the increase of superficial gas velocity and liquid viscosity.Liquid viscosity promotes the bubble coalescence behavior and inhibits the bubble breakup behavior.The increase in superficial gas velocity and liquid viscosity,the bubble size distribution gradually changes from single to double peak.The increase of superficial gas velocity intensifies the fluid turbulence,while the increase of viscosity weakens the fluid turbulence,and the flow field tends to be more stable.The effects of bubble regulation technology on bubble regulation behavior,bubble trajectory,bubble distribution,gas-liquid interfacial area and fluid flow field were studied by using high-speed camera,particle image velocimetry（PIV）and laser induction fluorescence（LIF）.The experimental results show that the average bubble size can be significantly reduced by bubble regulation.Compared with no regulation,the Sauter mean diameter is reduced by 33.5% and 22.2% respectively by 3.8 mm and5.5 mm mesh internals.The increase in viscosity results in bubbles that are more likely to pass through the mesh or not breakup when subjected to severe deformation.The two-stage regulation technology is proposed.Through two-stage regulation,the bubble size can be further reduced and the probability of bubble re-coalescence can be reduced.After two-stage regulation and single-stage regulation,the Sauter mean diameter is reduced by 47.1% and 30.3% respectively.After installing the mesh internals,an independent flow field distribution is formed above and below the mesh in the device,which reduces the liquid back-mixing.Through the bubble regulation technology,the process strengthening purpose of reducing the bubble size and prolonging the bubble residence time can be realized,and the number of bubbles,gas holdup and gas-liquid interfacial area can be increased,which is conducive to improving the gas-liquid mass transfer rate.The change of solution p H caused by the chemical absorption of sodium hydroxide to carbon dioxide is used as the basis for judging the mass transfer effect by comparing the reaction time between gas and liquid.The mass transfer experiment shows that the bubble regulation technology can significantly reduce the gas-liquid reaction time and improve the mass transfer effect.The better the bubble regulation effect is,the more conducive it is to promote the mass transfer process between gas and liquid.The reaction time of 3.8 mm wire mesh is 8.8% less than that of 5.5 mm wire mesh and 10.3% less than that without wire mesh;The reaction time of two-stage regulation was reduced by 22.2% compared with that of non regulation.The research shows that the bubble regulation technology can effectively promote the mass transfer process of gas-liquid two-phase by inhibiting the bubble coalescence,increasing the bubble breakup,significantly enhancing the bubble dynamics behavior and updating the phase interface.The research work of this subject has great scientific significance for in-depth understanding of gas-liquid flow characteristics and strengthening mass transfer process.It has broad industrial application value and development prospects for gas-liquid mass transfer,structural optimization,design and development of reaction equipment.