Vapour condensation of R22 retrofit substitutes R417A, R422A and R422D on CuNi turbo C tubes

Heat transfer coefficients (HTCs) for outer condensation of R22 and vapours of its retrofit substitutes R417A, R422A and R422D on 90/10 CuNi Turbo C tubes were experimentally measured. The tubes have 19.05 mm nominal outside diameter, 40 fins per inch (1575 fpm) on the outer surface and a smooth inner surface. The effective condensing length per tube was 1895 mm. Experimental data are reported at vapour saturation temperature of 40 °C and wall subcoolings from around 1.5 to 8 °C. A rapid increase of the HTCs for low wall subcoolings attributable to the presence of the hydrocarbon in the mixtures was found. For wall subcoolings greater than around 3 °C, the condensation HTCs slightly increase with raising the wall subcooling and they are for vapours of R417A, R422A and R422D lower by 65–76%, 24–31% and 60–67% than the HTCs for R22, respectively. Comparisons of the condensation performance amongst the different refrigerants and experimental enhancement factors for the condensation of R22 on 90/10 CuNi Turbo C tubes are reported in the paper.