Numerical Simulation Of Heat And Mass Transfer Characteristics Of A Kettle Evaporator

In the radioactive waste liquid evaporation and concentration process,the core equipment is the evaporator,and the heat and mass transfer parameters of the evaporator are closely related to the product yield and product quality.However,a large amount of energy and materials are used for one run because of the large volume of industrial evaporators.The research on the heat and mass transfer characteristics of the reactor is expensive,and it is difficult to inspect the inside of the evaporator.With the maturity of computational fluid dynamics,the simulation of heat and mass transfer characteristics of evaporators has become an important research tool.This paper calculates the heat and mass transfer parameters of the evaporator for the evaporator process index provided in the radioactive waste liquid evaporation and concentration process firstly.The mass flow rate of the secondary is calculated to be 482.18kg/h.the heat flux is 1.20×106kJ/h,the condensation heat transfer coefficient is 1.52×104W/(m2·K),and the boiling heat transfer coefficient is 1.17×105W/(m2·K),the total heat transfer coefficient is 734W/(m2·K),the heat exchange area is 17.11m2,the heating chamber diameter is 2m and the high is 2.5m,the evaporation chamber diameter is 0.5m and the high is lm,the heat and mass transfer parameters of the evaporator are calculated.According to the above results,in order to find a better heat and mass transfer mode of the evaporator,four heating surfaces are constructed The four heating surfaces are heating coil heating,heating coil and heating jacket heating.vertical heating tube heating,vertical heating tube and the heating jacket,and the geometric model was established for the above schemes.The meshing and grid quality inspection were also carried out.The calculation software COMSOL Multiphysics was used to establish the evaporator heat transfer model,the diluted species transport model,the evaporator moisture transport model.The liquid laminar flow model and the secondary steam turbulence model complete the setting of the solver and the program to complete the simulation calculation.The calculation results showed that the simulated steam generation is less than 10%compared with the parameters calculated by the evaporator.The parameters we studied are the flow rate,the different hydraulic pressure of the feed liquid,the different temperatures of the feed liquid,the heat flux of the feed liquid,the solute flux,the steam quantity distribution,and the comparative analysis.The results showed that the heat and mass transfer performance of the heating coil and the heating jacket were better than other heating surfaces,and the evaporation efficiency was higher,which can support the improvement of the evaporator.The simulation results of the three-dimensional model of the evaporator were carried out.These results can be used to analyze the heat and mass transfer characteristics of the evaporator.They were similar to the two-dimensional model.The two-dimensional model can be used to simplify the calculation of the three-dimensional model.