Experimental study of condensation heat transfer characteristics of R134a and its blends outside tubes
This experimental study investigates the condensation heat transfer properties of refriger-ant R134a and its blends,including R125,outside both a smooth tube and an enhanced tube.The re-sults show that the variation of condensation heat transfer coefficient of R134a outside the smooth tube is consistent with the Nusselt solution.When the heat flux is 25 kW/m2,the condensation heat transfer coefficient outside the enhanced tube is higher than that of the smooth tube.The enhanced ra-tio of R134a is 15.27,and the enhanced ratio of R134a/R125(the proportion of R125 is 6%,12%and 18%)is 7.45,5.74 and 5.38,respectively.The enhanced ratio of R417A was 6.69.The condensa-tion heat transfer coefficient of R134a mixture containing R125 decreases with the increase of heat flux.The condensation heat transfer coefficient increases with the increase of heat flux over the en-hanced tube.It is found that the condensation heat transfer coefficients show that the pure working medium is higher than the binary mixture,and the binary mixture is higher than the ternary working medium.
R134a/R125R417Aenhanced tubecondensation heat transfer
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