Research On Falling Film Evaporation Enhancement Of Acrylic Solvent Recovery

Compared with other types of heat exchanger equipment,vertical falling film evaporator has some advantages,such as high heat transfer coefficient,low heat transfer temperature,can handle the heat sensitive materials,easy to multi-effect operation,simple structure and other advantages.Because of these advantages,falling film heat evaporator is widely used in industry.In this paper,a new type of high efficiency falling film evaporation device is developed to solve the problem that the low heat transfer coefficient,for that liquid is not easy to film and low heat transfer temperature difference,and based on the purpose of energy conservation and emission reduction of acrylic solvent.Main work and achievements are as follows:1.In this paper,three types of film distributors with rectangular,elliptical and circular openings are developed,and the minimum liquid flow rate is measured,combined with the theoretical formula proposed by Hartley,the elliptical opening film distributor is optimized.Using Nusselt model and Wilke model to calculate the average thickness of the liquid film.Finally,the liquid level of the liquid distributor is checked,which provides a guarantee for the experimental results.2.The heat transfer coefficients of fluted tubes were calculated with heat flux from 13.2 kW/m2 to 56.52 kW/m2,liquid peripheral feed flow from 0.419 kg/m s to 1.112 kg/m s,heat transfer temperature difference from 2.02? to 9.87?,and compared heat transfer coefficients to smooth tubes under the same operation conditions.The results show that the heat transfer enhancement of fluted tubes increases with the increase of Reynolds number in certain range;in the same heat flux,the heat transfer temperature difference of the fluted tube are only 51%compared with smooth tube;the condensation heat transfer coefficients of fluted tube are 2.07 times that of smooth tube,and the overall heat transfer coefficients are 1.73 times,the enhancement effects are remarkable.3.Using the improved Wilson graphical method,combined with the experimental data,conduct the liner regression of vertical fluted tubes and ordinary light tubes' results,and get condensation heat transfer coefficient of outside tube,results show that the Wilson graphic method of linear regression relationship is very good,the regression results accord with the experimental results,proved the reliability of the experimental data.According to the relevant heat transfer theory,the correlations of condensation heat transfer on vertical fluted surface were obtained based on the experimental results,and the correlations can provide reference for the engineering application.