Experimental studies of film condensation of R134a and mixed R134a/R125 at three different concentrations have been conducted on three tubes

one is smooth tube

the others are two-dimensional and three-dimensional enhanced tubes at the same fin density. The results indicate that the predicted condensation heat transfer coefficients of R134a on smooth tube from Nusselt theory agree with the experimental data within ±10 percent. The condensation heat transfer coefficients of pure R134a are consistent with Nusselt theoretical trend for smooth and enhanced tubes. Compared with pure R134a

the condensation heat transfer coefficients of mixed R134a/R125 are all decreased. For smooth tube

condensation heat transfer coefficient of mixed refrigerants decreased with the increase of temperature difference. But for enhanced tubes

condensation heat transfer coefficients increased with the increase of temperature difference

which is close to pure R134a at high temperature difference

the mixed refrigerant including 6 percent and more R125. Indicating that condensation heat transfer of mixed refrigerants is quite different with pure refrigerants. Condensation heat transfer coefficient of three-dimensional enhanced tube is higher than that of the two-dimensional tubes

and two-dimensional tube is significantly higher than that of smooth tube at the same working fluid. The condensation heat transfer enhancement factor of HT-3D

HT-2D are 9.83 and 7.85

respectively

which compared with smooth tube at the temperature difference 8 K.