Abstract
Expenmentswere conducted to obtain row-by-row heat transfer data during condensation of downward-flowing zeotropic refrigerant mixture HCFC-123/HFC-134 a on a staggered bundle of horizontal low-finned tubes. The vapor temperature and the HFC-134a m ass fraction at the tube bundle inlet were maintained at about 50°C and 14% respectively. The refrigerant mass velocity ranged from 9 to 33 kg/m2s, and the condensation temperature difference from 2 to 12K. Four kinds of low-finned tubes with different fin geometry were tested. The highest heat transfer coefficient was obtained with a tube which showed the highest performance for HCFC-123. However, the effect of fin geometry was much smaller for the mixture than for HCFC-123. The heat transfer coefficient and the vapor-phase mass transfer coefficient decreased significantly with decreasing mass velocity. On the other hand, the mass transfer coefficient increased with condensation temperature difference. This was due to the effect of suction associated with condensation. On the basis of the analogy between heat and mass transfer, a dimensionless correlation of the mass transfer coefficient was developed for each tube.
