Characteristics Of Heat Transfer Of The Wiped Film Molecular Distillation And The Wall Optimization Of The Wiped Film Molecular Distillator

Wiped film molecular distillation(WFMD)has advantages because of the existence of the wipers,and it is widely used in the production of food and pharmaceutical,the separation and purification of polymer,the separation and recycling of heat sensitive material.In recent years,research on WFMD mainly concentrate in the flow of the liquid,film thickness,the mean residence time distribution,the evaporation ratio,and the flow of vapor phase,only a few of researchers studied the heat transfer characterisitics of WFMD.So the study of heat transfer characteristics of WFMD with the existence of two phase flow and their evaporatin,can improve the understanding of WFMD,and provide a reference for the further optimization of WFMD.CFD software can numerically calculate the fluid motion,and widely used in the flow and heat transfer process which are complex and difficult to measure.So in this paper,we syudy the heat transfer charactristics of WFMD with the CFD software that hooked the UDF which can get the result of evapoation;we also optimized the evaporating cylinder and compared the result with the smooth evaporating cylinder in WFMD.The WFMD was simulated with different rotor speeds,different feed rates and different evaporating temperatures,and the full developed temperature filed and velocith field were got,these result showed that:the of the wiper affect the tangential velocity most,produce the local eddy and change the helicity of the liquid;the local Nu increase sharply where the wiper wipes,and this is an important factor that increases the average Nu.With the increasing of the rotor speed,the wiped period decrease,the dynamic stable film surface temperature(Tdst)increases and then dicreases,and the change of Tdst decreases;the temperature gradient,the velocity gradient and the average Nu are also increase firstly and then decrease.with the increasing of feed rate,the Tdst decreases,but Nu increases.With the increasing of evaporating cylinder temperature,the average Nu increases.appropriately increase the rotor speed and evaporating cylinder temperature will accelerate the evaporation of light component.Add tiny fins on the evaporating cylinder of WFMD,the simulation result showed that:the addition of the tiny fins complicate the liquid flow,and increase the vorticity and helicity,and change the direction of the helicity of the liquid.With therectangular arrangement,triangular arrangement and the spiral arrangement of fins,the average Nu respectively 1.32,1.23 and 1.04 times as large as the smooth one.The addition of tiny fins increase the synergistic effect of temperature field and velocity field,improve the heat transfer characteristics;and the different arrangements of tiny fins makes the heat transfer process increase differently.