Experiment And Research On Condensation Heat Transfer Outside A Horizontal Tube Bundle Under Negative Pressure

Condensation heat transfer experiment uses several light tube bundle of horizontal arrangement,the biggest advantage of which are the lower cost and the highest heat exchange efficiency.Using condensation heat transfer coefficient as the experimental standard,the condensation heat transfer mechanism in the different rows of tubes and the model of bundle effect were analyzed.Outside condensation heat transfer of horizontal tube bundle taking the mixture of alcohol-water vapor as the research object,Marangoni phenomenon of double mediums was studied on the wall of horizontal tube bundle.Marangoni condensation than the previous effects of condensation heat transfer outside the light tube is much higher and has better generalization ability.By the experiment system of Marangoni condensation heat transfer with much higher air tightness.Heat transfer of the isothermal surface has studied experimentally under various vapor flow(10kg?h-1、14 kg?h-1) and pressure(31.5kPa、47.5kPa、80.5kPa).A wide range of ethanol mass fractions(0%、1%、5%、10%) has been employed.The characteristic curves of the heat transfer coefficient according to vapor-to-surface temperature difference have been obtained.The experimental results indicated that the coefficient of the first row condenser pipe(having the same condensation situation with the single condenser pipe) decreased with the increase of vapor-to-surface temperature difference,but the decrease rate of the second row tubes will change at a certain vapor-to-surface temperature difference and then became relaxtive.While the ethanol vapor concentration was larger than 5%,the second ones shows the same decrease.The highest heat transfer coefficient appeared at the ethanol vapor concentration of 1%.When the ehanol vpor concentration was more than 5%,the heat transfer coefficient decreased with the increase of ethanol vapor concentration.Steam pressure for tube heat transfer coefficient also shows basically the same impact curve. Steam flow has less impact on the heat transfer coefficient than concentration and pressure.To study bundleeffect,the “bundle effect facor” was put forward to analyzing the effect of condensation heat transfer tube bundle and obtained polynomial fitting of the tube bundle effect.