Abstract
New experimental data are reported for condensation of R-113 at near atmospheric pressure and low velocity on five three-dimensional pin-fin tubes. The only geometric parameters varied were circumferential spacing and thickness, since these have been shown to have a strong effect on condensate retention on pin-fin tubes. Heat transfer enhancement was found to be strongly dependent on the active-area enhancement, i.e., on the parts of the tube and pin surface not covered by condensate retained by surface tension. For all the tubes, vapor-side heat transfer enhancements were found to be approximately 2.5 times the corresponding active-area enhancements, and this finding was in line with earlier data for R-113. An increase in the vapor-side heat transfer enhancement is noticed with the decreasing values of pin spacing. The best performing pin-fin tube gave a heat transfer enhancement about 14% higher than the "equivalent" two-dimensional integral-fin tube (i.e., with the same fin root diameter, longitudinal fin spacing, and thickness and fin height).