Abstract
The present study experimentally investigated the condensation heat transfer characteristics, condensate flow modes, and condensate flooding angle of R245fa on horizontal low-finned and microscopic-grooved tubes. Seven low-finned and three microscopic-grooved tubes with tube diameters of approximately 19 mm at the fin tip were used as the test tubes. Experiments were conducted at a constant saturation temperature of 40 °C. Three condensate flow modes—droplet mode, droplet-column mode, and column mode—were observed in this experiment. The transition film Reynolds number of the condensate flow mode of the low-finned tubes was different from that of the condensate flow mode of the microscopic-grooved tubes. The condensate flow mode of the microscopic-grooved tubes transited from droplet mode to droplet-column mode had a lower film Reynolds number than that of the low-finned tubes. The condensation heat transfer characteristics of the low-finned and microscopic-grooved tubes were experimentally investigated to clarify the condensate flow modes and the effects of fin pitch, fin height, and fin geometries on the condensate flooding angle and condensation heat transfer.
