A comparison of heat transfer coefficients for condensation of CFC-11 and HCFC-123 on an in-line bundle of horizontal finned tubes

This paper presents a comparison of measured condensation heat transfer coefficients for refrigerant CFC-11 and its proposed replacement HCFC-123 flowing down a 3×15 (columns×rows) in-line bundle of horizontal finned tubes. The vapor velocity at the tube bundle inlet (based on minimum flow cross section) ranged from 0.9 to 10 m/s, and the condensation temperature difference from 1.3 to 19 K. Heat transfer measurements were made on a row-by-row basis. Generally, the heat transfer coefficient for HCFC-123 was about 10% lower than that for CFC-11. The heat transfer enhancement due to vapor shear was much smaller than that in the case of a smooth tube bundle. At a high vapor velocity, the enhancement was most significant for the top row and decreased sharply with increasing row number. The decrease in the heat transfer coefficient due to condensate inundation was also much smaller for the finned tube bundle. The measured heat transfer coefficient for the smallest vapor velocity agreed well with the theoretical prediction for a stagnant vapor.