The Numerical Simulation Of Fluid Flow And The Preliminary Research Of Heat Transfer Calculation For Thin-film Evaporator

The thin-film evaporator (TFE) is a new-type highly efficient evaporating equipment. It utilizes the high-speed rotation blade to disperse the fluid as uniform thin film so as to concentrate the material. It is especially suitable for the separation of materials that are high-boiling, high viscosity and heat-sensitive. Up to now, the research and popularization of TFE at home and abroad have got some achievements, but the foundational data for design are still limited. How to get the distribution of the velocity field, temperature field and concentration field which are formed in the process of thin-film evaporation is a valuable research subject.On the basis of the 1m2 steel TFE test equipment which was developed by CHEMICAL EQUIPMENT DESIGN INSTITUTE OF NANJING UNIVERSITY OF TECHNOLOGY, a 0.4m2 steel TFE test equipment is designed. Based on the design parameters of the 0.4m2 evaporator, the fluid flow and heat transfer process in thin-film evaporator are numerically simulated using the CFD software CFX4.4, and the velocity field and temperature field of the thin film are obtained. Consequently, the effects of blade length, blade inclination angle, rotational speed, mass flow-rate, material viscosity and inlet temperature on the fluid flow and heat transfer process are preliminary analyzed. The simulation results show that the rotation speed and the blade inclination angle have great effects on the fluid flow process in TFE. The high-speed rotation blade disperses the fluid as fully uniform thin film and increases the radial mixing of the fluid effectively, the radial velocity and total velocity of the fluid in thin-film increase obviously with the increase of blade inclination angle. The blade with positive inclination angle can accelerate the radial mixing of the thin film, and the mean residence time can be controlled by changing the inclination angle of the blade. The mass flow-rate and viscosity have great effects on heat transfer process. Finally, the effects of structure and operation parameters on the fluid flow and heat transfer are preliminary studied. Also the design parameters of TFE are discussed. These researches lay the foundation for further application and popularization of this equipment.