| Title |
Condensation Heat Transfer Coefficients of Binary Refrigerant Mixtures on Enhanced Tubes |
| Keywords |
Condensation heat transfer ; 응축열전달 ; Binary refrigerant mixture ; 이원 혼합냉매 ; Non-azeotropic mixture ; 비공비 혼합냉매 ; Enhanced tube ; 열전달 촉진관 |
| Abstract |
In this study, external condensation heat transfer coefficients (HTCs) of two non-azeotropic refrigerant mixtures of HFC32/HFC134a and HFC134a/HCFC123 at various compositions were measured on both low fin and Turbo-C enhanced tubes of 19.0 mm outside diameter. All data were taken at the vapor temperature of 39℃ with a wall subcooling of 3∼8 K. Test results showed that HTCs of the tested mixtures on the enhanced tubes were much lower than the ideal values calculated by the mass fraction weighting of the pure components' HTCs. Also the reduction of HTCs due to the diffusion vapor film was much larger than that of a plain tube. Unlike HTCs of pure fluids, HTCs of the mixtures measured on enhanced tubes increased as the wall subcooling increased, which was due to the sudden break up of the vapor diffusion film with an increase in wall subcooling. Finally, heat transfer enhancement ratios for mixtures were found to be much lower than those of pure fluids. |