Condensation heat transfer on single horizontal smooth and finned tubes and tube bundles for R134a and propane

For the refrigerants 1,1,1,2-tetrafluoroethane (R134a) and propane (R290), the condensation heat transfer was investigated on coated and uncoated horizontal smooth, standard finned and high performance tubes by experiments and computational fluid dynamics (CFD)-simulations. Measurements were carried out at a saturation temperature of 37 degrees C varying the heat flux between 4 kW m(-2) and 102 kW m(-2). In comparison to the Nusselt theory, enhancement factors of 12.8 to 30.2 were experimentally found for single standard finned and single high performance tubes. For both refrigerants, the high performance tubes showed a larger bundle effect than the standard finned tubes, although the latter show a lower heat transfer performance. In general, experimental results for coated tubes show a slightly lower heat transfer performance and no improvements of the condensate drainage could be observed for the modification. CFD-simulations were used to predict the condensation heat transfer on single tubes for the first time. Our experimental data and CFD-simulations were compared with analytical models available in the literature. (C) 2012 Elsevier Ltd. All rights reserved.