Study On Interfacial Convection In Gas-liquid Mass Transfer Processes By Schlieren Observation And Theoretical Analysis

The distribution grade of concentration or temperature in the process of mass or heat transfer at the interface will trigger off the interface convection when it rose to a certain level.Which can be classified as Rayleigh convection driven by density gradient and Marangoni convection driven by surface tension gradient.Without external disturbance introduced in the system,the interfacial convective will accelerate fluid mixing and promote the effect of mass and heat transfer.The deeper research on the mechanism of the mass transfer the better development of mass transfer separation engineering,and which is of great significance to the optimization of heat exchange equipment modification.What’s more,by introducing non-equilibrium thermodynamics,theory this article studied the pictures of mass transfer process obtained by schlieren experiment,to contribute to promoting the development of the theory of transmission.In this paper,workers built reasonable schlieren device and eliminated the influence of the heat disturbance,by using higher precision observation equipment,detailedly watched the occurrence and development of convection structure of ethanol absorbing CO₂.And analyzed the influence of the liquid viscosity,inert gas N₂,interface small eddy structure on convection development and the coming of new interfacial convective structures.After quantifying the mass transfer interface,the author obtained accurate interface structure,accurately determined the mass transfer interface,and lay a foundation for the subsequent quantitative analysis.In this article,by introducing the theory of entropy generation of non-equilibrium thermodynamics,the author quantificationally analyzed the process of CO₂ absorbed into ethanol about the energy dissipation,and acquired the specific distribution and change trend of local entropy generation before the Rayleigh convection trigger,which was that nearby the interface mass transfer local entropy generation decreased with the going on of mass transfer time and reduced gradually,while the maximum of mass transfer Ra number was gradually increasing.This experimental result challenged the knowing that there was a critical entropy generation corresponding to the critical Ra number,and lay a foundation for the further study of the relationship between the critical Ra number and the entropy generation.Based on the quantitative analysis of the horizontal Angle of mass transfer box,the condition of slightly unbalanced during mass transfer process was constructed in this paper,and the interfacial eddy structure,which usually accompanied with the interfacial plume structure,was separated from the plume convection structure.What’s more,we introduced the non-equilibrium thermodynamics analysis method of entropy generation which avoid the analysis of small eddy structure nearby the interface,and studied the influence of the vortex.Quantitative analyzed the influence of the vortex structure during the interfacial mass transfer process on the energy dissipation and the liquid phase distribution of entropy generation.At the same time,the compare with the situation without interface vortex structure,we known the eddy’s influence furtherly.Moreover,the interface eddies played important roles in the interface concentration uniform and the forming of new plume structures.The study of global entropy generation indicated that the irreversible form of convection changes from linear to non-linear with the appearance of the ordered plume structure,and the complexity of mass transfer was further deepened.