| In recent years,tetrafluoropropene HFO1234 ze stands out because of its great environmental protection advantages(zero ODP,GWP<1,very short atmospheric lifetime,only 0.0029 years).Therefore,this article focuses on the new refrigerant HFO1234 ze,from experiments and theory two aspects,to explore the condensation heat transfer characteristics outside the horizontal tube.In this paper,HFO1234 ze and R134 a were subjected to condensation heat transfer experiments on a two-side enhanced tube phase change thermal experimental bench,including a smooth,two-dimensional reinforced tube(C43a,C44a)and a three-dimensional reinforced tube(C45a).The experimental results outside the two-dimensional enhanced tube are compared with the prediction results of the common two-dimensional fin tube outer-convex condensation heat transfer model,and the following main conclusions are obtained:(1)The surface heat transfer coefficient of HFO1234 ze outside the horizontal tube decreases with the increase of heat flux density.This change rule is consistent with the prediction result of Nusselt’s theoretical solution.The experimental value of condensation heat transfer of HFO1234 ze outside the horizontal light tube and Nusselt’s theoretical prediction value The deviation is within ±10%.(2)Whether it is a light pipe,a two-dimensional reinforced pipe,or a three-dimensional reinforced pipe,the heat transfer coefficient at the outer surface of the pipe at a temperature of 40℃ is larger than that at 35℃ under a small heat flux density.But at large heat flux(light pipe greater than 15kW/m2,reinforced pipe greater than 50 kW/m2),the heat transfer coefficient at the outer surface of the pipe at 40℃ is approximately equal to that at 35℃.The outer surface heat transfer coefficient of the tube showed no effect.(3).For the pure working fluid HFO1234 ze,the surface heat transfer coefficient outside the three-dimensional reinforced pipe(C45a)is higher than that of the two-dimensional reinforced pipe(C43a,C44a)at the same heat flux density,and the two-dimensional reinforced pipe is also higher than the light pipe.The two-dimensional reinforced pipe(C44a)with a large rib density is higher than the two-dimensional reinforced pipe(C43a)with a small rib density.At the same wall temperature difference of 7℃,the condensation heat transfer enhancement ratios of the enhancement tubes C43 a,C44a,C45 a with respect to the light pipe were 8.04,8.57,and 9.53,respectively.(4)in this paper,the commonly used two-dimensional reinforced tube condensation heat transfer model(Beatty-Katz model,Owen model,Webb model,Honda model,Rose model)was used to predict the heat transfer coefficient of HFO1234 ze and R134 a outside the horizontal two-dimensional rib surface.The results show that: HFO1234 ze has a large deviation between the theoretical prediction and the experimental value.To better predict the condensation heat transfer characteristics of HFO1234 ze outside the two-dimensional rib tube,this paper proposes a novel refrigerant HFO1234 ze outside the horizontal two-dimensional rib tube.The film condensation heat transfer model,and whether the model for the new refrigerant HFO1234 ze or refrigerant R134 a,the theoretical prediction results and experimental values can be controlled within ± 10%. |
