Study On The Flow Field Characters In The Wiped Film Molecular Distillation Equipment By Cfd Simulation Method

As a high efficiency separation method, molecular distillation is widely used in the chemical, food, pharmaceutical, cosmetic industry and so on, due to its special separation mechanism. Comparing with the conventional distillation technology, molecular distillation has the mild operating condition, high separating efficiency, and is more suitable for the separation of the material with low volatility, high boiling point, thermo-sensitive property and biological activity. Among the various molecular technologies, wiped film molecular distillation has a broadest application in the lab and industry due to its advantages. Inside the molecular distillation equipment, there has a complex flow field because of the rotors'scraping effect, so the study on the molecular distillation is usually restricted to the experimental conditions and can't get a good effect. But CFD simulation method is almost not limited by the experimental condition. It also has the shorter research period and the more flexibility. Therefore, this paper chooses the CFD software FLUENT6.2 to study on the flow field characters inside the molecular distillation equipment.Firstly, the 2D model of the evaporator in the wiped film molecular distillation equipment is built to simulate the liquid film thickness and uniformity in the cold model. After investigating the influence of the rotors'rotational speed, motion mode , shape and material kind on the liquid's flow state, the best operating condition is achieved. And the study also provides some advice to improve this kind of equipment and the separation effect.On the basis of the 2D model, the 3D model is built to study on the resident time distribution(RTD). The influence on the RTD from the feeding velocity, rotors'rotational speed and material viscous is taken into consideration. The RTD curve in different operating conditions is analyzed. The orthogonal test is designed to get the various effect of the factors and the optimum condition. And the empirical correlations equation between average RTD and feeding velocity and rotors'rotational speed are achieved in different viscous.At last, the UDF method is used to improve the 3D model. The inlet is defined by the UDF program, so as to simplify the geometry model and improve the grid quality. As a result, the velocity and the precision of the simulation is improved. What's more, the feeding speed distribution at the inlet is defined by UDF in order to achieve the conditions which tally with the actual situation. And it provides a direction for the further study of this kind.