Experimental Study Of R1234ze And R134a On Film Condensation Heat Transfer Outside The Low Rib Tube

The destruction of the ozone layer and the increasing global temperature have caused widespread concern in the world.Because of the protection of human survival environment,CFCs and HCFCs refrigerants are being phased out.Although the ozone layer is greatly reduced by HFCs refrigerants,most of which have relatively high Greenhouse Effect,they can only meet the needs of human beings at a certain stage.Eventually,they have to face the fate of being eliminated.This is an urgent need for the search for new alternative refrigerants(zero ODP,low GWPs).In this paper,the condensation heat transfer of R134a and R1234ze outside the light tube and the strengthened tube is studied experimentally at the operating temperature of 35?and 40?,Combined with the theoretical analysis,the correlation formula for predicting the condensation heat transfer outside the mixed working fluid tube is predicted,and the following conclusions are obtained:(1)For pure working medium R134a and R1234ze,The condensation heat transfer coefficient in the light tube and the reinforced tube decreases with the increase of the heat flux.(2)The condensation heat transfer coefficient outside the strengthened tube is higher than that outside the light tube under the same conditions,which indicates that the surface of the tube can be thinned by the effect of surface tension.For pure R134a,when the heat flux is30kW/m~2,the condensation heat transfer coefficient outside the strengthened(C43a/C44a/C45a)tube is13.27/13.38/14.99 times of that of the light tube at the operating temperature of35?,and the condensation heat transfer coefficient of pure R1234ze outside the strengthened tube(C43a/C44a/C45a)is 12.78/12.84/14.49 times that of the light tube when the heat flux is 30kW/m ~2 at the operating temperature of 35?.(3)Under the same condition,the condensation heat transfer coefficient of the three-dimensional strengthened tube is higher than that of the two-dimensional strengthened tube.When the temperature of the working condition is 35?,and the heat flux is 30kW/m~2,The condensation heat transfer coefficient of pure R134a outside the three dimensional reinforced tube(C45a)is 1.13 times as high as that of a two-dimensional reinforced tube(C43a).(4)When the working temperature is 35?,the condensation heat transfer coefficient of pure R134a is obviously higher than that of pure refrigerant R1234ze.When the heat flux is25-100kW/m~2,the condensation heat transfer coefficient of two-dimensional reinforced tube(C43a/C44a)in R134a is 1.25-1.10/1.20-1.12 times of that of R1234ze.Under the same conditions,the three dimensional enhanced tube(C45a)was 1.20-1.07 times.(5)On the basis of theoretical analysis,the correlation of condensation heat transfer outside the mixture tube is predicted.By comparing the experimental data of condensation heat transfer outside the R134a/R125 tube,it is found that the deviation between the theoretical and experimental values of condensation heat transfer coefficient outside the strengthened tube is±20%.