Study On The Influence Of Soybean Oil Compound Interpolation Spiral On The Heat Transfer Performance Of Syrup Falling Film Evaporation

Syrup is a high viscosity multi-component solution,often used in feed additives.Lime water is needed in the syrup production process,which will easily lead to the deterioration of heat transfer and scale formation during evaporation.In this paper,the heat transfer enhancement technology of composite interpolation spiral of soybean oil is adopted,and the reciprocating vibration characteristic of the interpolation spiral and the synergistic effect of viscosity reduction of soybean oil are utilized to enhance the heat transfer and prevent and remove scale at the same time.Through numerical simulation and experimental research,the falling film evaporation heat transfer of the composite interpolation spiral syrup of soybean oil is studied.The contents are as follows:(1)The physical parameters of the syrup and three kinds of common vegetable oil were measured,and the changing rules of the syrup and vegetable oil with temperature are obtained,which provided a theoretical basis for the experimental study on the falling film evaporation of soybean oil syrup.The falling film evaporation experiment platform was set up,and the soybean oil syrup falling film evaporation experiment was carried out.The heat transfer process of the three vegetable oil syrups is compared and the heat transfer performance of soybean oil is the best.Therefore,soybean oil is selected as the viscosity reducer for heat transfer research.(2)In order to analyze the influence of viscosity on the heat transfer of syrup,three kinds of soybean oil with volume concentrations(3Vol%,5Vol% and 10Vol%)were used in the experiment.It is found that the heat transfer coefficient of soybean oil added with 10Vol% is better than that of 5Vol% and 3Vol%.The heat transfer coefficient of three concentrations increases with the increase of heat flux and heat transfer temperature difference.However,with the increase of mass flow,it firstly increases and then decreases,and then peaks when the mass flow is 1267kg/h.The heat transfer correlation equation suitable for falling film evaporation is obtained by numerical fitting with heat flux,heat transfer temperature difference and mass flow rate as functions.(3)The influence of interpolation spiral on the heat transfer of syrup was analyzed through the heat transfer experiment of falling film evaporation.Orthogonal analysis shows that the order affecting heat transfer is the highest pitch p,followed bymedian diameter D,and the smallest wire diameter e.The optimal spiral structure parameter combination is p=25mm,e=1.9mm and D=33mm.By analyzing the three parameters in turn,the heat transfer coefficient increases with the increase of median diameter and pitch.The heat transfer coefficient increases first and then decreases as the wire diameter increases.When the wire diameter is 1.9mm,the heat transfer coefficient reaches the highest.(4)In order to study the heat transfer enhancement effect of compound interpolation spiral of soybean oil,the falling film evaporation experiment of compound interpolation spiral of soybean oil with 5Vol% was carried out to compare the heat transfer performance of four conditions(compound interpolation spiral of soybean oil with 5Vol%,interpolation spiral,5Vol% soybean oil with light tube)under different process parameters.When the heat transfer temperature difference,evaporation pressure and mass flow rate are the same,the heat transfer coefficient of5Vol% compound interpolation spiral pipe of soybean oil is the largest,followed by the interpolation spiral pipe and 5Vol% soybean oil pipe,and the light pipe is the smallest.With the increase of syrup brie,the heat transfer coefficient of the four tubes decreases gradually.(5)In order to further analyze the heat transfer mechanism of compound interpolation spiral of soybean oil,the falling film evaporation flow and heat transfer process of compound interpolation spiral of soybean oil were simulated on the basis of the experiment.The velocity distribution,temperature field distribution and liquid film distribution of the four working conditions(compound interpolation spiral of5Vol% soybean oil,interpolation spiral,5Vol% soybean oil and light tube)are simulated.It is found that the viscosity of 5Vol% soybean tubing decreases and the axial velocity of liquid film increases.The axial velocity and radial velocity of the liquid film in the inserted helical tube increase.When the Reynolds number is the same,the liquid film thickness of 5Vol% soybean oil composite intercalated spiral pipe is the thinnest,followed by the intercalated spiral pipe and 5Vol% soybean oil pipe,and the liquid film thickness of light pipe is the second thickest.The liquid film evaporation temperature is the highest in the compound interpolation spiral tube of soybean oil,in which the liquid phase volume fraction is the lowest and the syrup evaporation efficiency is the highest.