CFD Simulation Of Liquid Flow And Mass Transfer In Wiped Film Molecular Distillation

Molecular distillation technology has a significant effect on liquid-liquid separation technology, while the liquid film on the surface of the wall is in a complicated state of motion because of the scraping action of the rotor. Therefore, the purpose of the paper is to study the flow field characteristics and mass transfer process of the wiped film molecular distillation equipment, and to further improve the molecular distillation equipment and optimize the operation parameters.First, The simplified three-dimensional of wiped film molecular distillation was established by gambit software. The volume of fluid(VOF) multiphase model was applied to track gas-liquid two-phase flow.The RNG k-? turbulence model closed the momentum equation and enhanced wall function treated the liquid flow in the near wall region in the simulation. Without taking into account the state of mass transfer and heat transfer, the flow of liquid film in wiped film molecular distillation was simulated. The result showed that when the liquid film flow was stable, the change of the turbulent kinetic energy with time and the distribution of the turbulent kinetic energy were investigated. The turbulent kinetic energy of liquid film with time showed changes in volatility, and the fluctuation amplitude was related to the feed rate and rotor speed; In addition, the distribution of turbulent kinetic energy was not uniform, which mainly concentrated in the front rotor bow wave and rotor and the film contact area.Secondly, with the aid of the FLUENT software and UDF, the paper applied component transfer model and considered the mass transfer process of light components in two-component DBP-DBS, to research the mass transfer process of wiped film molecular distillation. The paper mainly discussed the variations of parameters of heat and mass transfer along the three-dimensional direction,such as liquid temperature, the volatile components of liquid concentration, gas concentration and evaporation rate. The result indicated that the surface temperature of liquid film and evaporation rate were gradually reduced along the circumferential and radial direction, and gradually increased along the axial direction; the concentration of volatile components in liquid phase decreases gradually along the circumferential and axial direction; The gas phase concentration increases along the axial direction.and the gas concentration in the vicinity of the rotor gradually spread to the entire surface.Finally, based on the research of hydrodynamics and mass transfer process, the single factor analysis method was used to explore the influences of the operating parameters,such as feed rate, wall heating temperature,rotor speed on mass transfer characteristics of wiped film molecular distillation. The effect was mainly reflected in the heat and mass transfer parameters such as the surface temperature, the liquid phase and gas phase concentrations of volatile components, evaporation rate and the total mass transfer coefficient which was for the purpose of providing a reference for further optimization of operating parameters.