Study On Ultrasound Enhancing The Heat Transfer Performance In The Evaporation Process

The ultrasonic evaporator is a new type highly efficient evaporating equipment. Ultrasonic technology is utilized to assist material concentrate by evaporation. Until now, the reports of the ultrasonic evaporator used in the industrial production are very few due to the theoretical study of ultrasonic field on evaporation of solution and the complication of boiling heat transfer. The basic data applied to ultrasonic evaporator design calculations is quite scarce.On the basis of the 0.4m2 steel ultrasonic evaporator which was developed by Tianjin University of Science and Technology, the heat transfer performance of water of the ultrasonic evaporator was investigated by numerical simulation and experimental study. The main work and conclusions are as follows:1) The effect of the main operating parameters on the ultrasonic evaporator by single factor experiment:the heat transfer coefficient, the efficiency of the evaporation and the evaporation rate increased with the increase of ultrasonic power density first and then decreased with it, and increased with the evaporation temperature, and increased with the feed flow.2) By analyzing the effect of main operating parameters on the degree of ultrasonic intensified heat transfer coefficient:Strengthen the efficiency increased to 25.29% first and then decreased with the increase of ultrasonic power density, and decreased from 29.85% to 24% approximately with the increase of the evaporation temperature, and basically stabled at 20%with the increase of the temperature difference, and slowly increased from 19.4% to 22.55% with the increase of the feed flow. Heat transfer coefficient increased the 17.06% ～ 29.85%, when the ultrasonic power density was 0.9w/cm2.3) Obtaining the sensitivity of the main operating parameters on overall heat transfer coefficient of the ultrasonic evaporator in regression analysis of the process of ultrasonic evaporation kinetics by orthogonal method and response surface analysis respectively: temperature difference> evaporator temperature> feed flow> ultrasonic power density. In analyzing and comparing the regression model of multivariate linear regression model and multivariate quadratic, the correlation coefficient of multivariate quadratic regression model was97.09% and the prediction accuracy was 91.89%, which can be used to estimate the heat transfer coefficient with different parameters. The optimum operating conditions of ultrasonic evaporator is that the evaporation temperature is 85 ℃, the processing capacity of 48L/h, the power density of 0.7455w/cm2, temperature difference is 20℃. The heat transfer coefficient theory can reach 1185.5 W/m2·℃.