Experimental Study And Mode Optimization On R245fa Condensation Heat Transfer Properties In Horizontal Tube

With the development of science technology, the use of refrigerant has polluted environment seriously, especially the effect of ozone depletion and greenhouse, although it benefits to mankind. The huge emission of carbon oxide and chlorofluorocarbons material has been produced by the waste of energy and the applications of non-environmental refrigerants. Since the properties of R245fa(five fluorine propane) has been found, more and more scholars has paid attention into the properties of evaporation and condensation.R245 fa, which could replace some mid-high temperature refrigerants, has many advantages such as zero ODP, low GWP, non-flammable and so on. What’s more, R245 fa could also have a good application in low pressure water chillers, high temperature heat pump and polyurethane foam industry. This paper mainly study the condensation properties and mode optimization of R245 fa in a horizontal circular tube.This research focuses on condensation heat transfer process of R245 fa with 4.38 mm horizontal tube. The range of condensation temperatures is employed from 30°C to 55°C,these data of mass velocity and cooling water range from 92(kg/m2s) to 276(kg/m2s),1056(kg/m2s)to 1752(kg/m2s), respectively. The temperature difference between water and R245 fa is 20°C. The results show the changing rate of heat transfer coefficient for R245 fa is normally same in the different condensation temperature. The peak of heat transfer coefficient exists in the large mass velocity and water velocity condition when the quality increases. And heat transfer coefficient increases in small mass velocity and water velocity conditions when quality increases. What’s more, the optimal operating range to maintain the high heat transfer coefficient and velocity properties is inferred by entropy analysis.Through the comparison conducted in different operating conditions, the conclusions for the application of R245 fa could be obtained as following:1.The heat transfer coefficient of R245 fa is affected by condensation temperature,quality and mass velocity of medium.2.The heat transfer coefficient could reach the peak when the quality ranges from 0.7to 0.9, and the velocity pattern is annular velocity at this time.3.ΔQ/ΔP could be maximum when the condensation temperature and mass velocity of medium from 30°C to 45°C, from 184(kg/m2s) to 276(kg/m2s), respectively, through the entropy method; The heat transfer coefficient could be maximum when the condensation temperature is 30℃-40℃ at the same time. The influence of condensation temperature is greater than that of velocity performance in the condensation heat transfer experiment of R245 fa in a 4.38 mm tube.4.The condensation heat transfer coefficient of R245 fa increase approximately linearwhen the quality is 0.1-0.7, while its rate becomes smaller when the quality is 0.7-0.8 in a case of large mass velocity rate. The heat transfer increase approximately linear when the mass velocity rate is small.5.Compare the experimental data with the Kim correlation, the error of R245 fa heat transfer experimental value with the Kim correlation is within 15%.The regular of heat transfer coefficient in the condensation process is obtained, as well as the different operating ranges to maintain high heat transfer coefficient. The result could provide a useful reference for the further development of high efficiency heat exchangers and some engineering practical significance for heat pump system optimization.