Condensation heat transfer coefficients of enhanced tubes with alternative refrigerants for CFC11 and CFC12

In this study, condensation heat transfer coefficients (HTCs) of a plain tube, low fin tube, and Turbo-C tube were measured for the low pressure refrigerants CFC11 and HCFC123 and for the medium pressure refrigerants CFC12 and HFC134a. Ail data were taken at the vapor temperature of 39 degrees C with a wall subcooling of 3-8 degrees C. Test results showed that the HTCs of HFC123, an alternative for CFC11, were 8.2-19.2% lower than those of CFC11 for all the tubes tested. On the other hand, the HTCs of HFC134a, an alternative for CFC12, were 0.0-31.8% higher than those of CFC12 for all the tubes tested. For all refrigerants tested, the Turbo-C tube showed the highest HTCs among the tubes tested showing almost an 8 times increase in HTCs as compared to the plain tube. Nusselt's prediction equation yielded a 12% deviation for the plain tube data while Beatty and Katz's prediction equation yielded a 20.0% deviation for the low fin tube data. (C) 1999 Elsevier Science Ltd and IIR. All rights reserved.