An Investigation of Condensation Heat Transfer Performance of HFC-134a on Single Enhanced Tubes (RP-984)

Abstract

Tests to measure shell-side heat transfer coefficients were performed on a single-tube test facility. HFC-134a was condensed on the horizontal test tube with cold water working as the coolant. Two 19.1 mm (0.75 in.) outer diameter (OD) enhanced tubes, one a two-dimensional (2D) finned tube and the other a three-dimensional (3D) enhanced tube, were used to construct the test section. For comparison purposes, a smooth tube of the same nominal diameter was also tested. The experiments were conducted over a heat flux range of 3155 to 63 100 W/m 2 (1000 to 20,000 Btu/h · ft 2 ) at saturation temperatures of 40 and 45°C (104 and 113°F).The tests revealed that the shell-side heat transfer coefficient dropped as heat flux increased. The enhanced tubes significantly improved the condensation heat transfer effectiveness compared with the smooth tube, with the 3D enhanced tube having the highest heat transfer coefficients. Specifically, the 2D tube had heat transfer coefficients that were 8.0 times better than the smooth tube, whereas enhancements of 11.8 times were seen in the 3D tube. The heat transfer coefficients for each tube were also compared with existing single-tube models.