scope:

INTRODUCTION

The present study is one portion of ASHRAE Research Project RP-984, "The Effect of Inundation and Immiscible Oil on Condensation Heat Transfer of R-134a," which investigates shell-side condensation of HFC-134a on both single tubes and tube bundles. This part of the study focused on determining the effects of heat flux, saturation temperature, and tube geometry on shell-side condensation heat transfer coefficients of HFC-134a on a single tube, and performing the Wilson plot on each tube type selected for the project.

Shell-side condensation heat transfer coefficients for R-134a were obtained in a 76.2 mm (3 in.) outer diameter (OD) test section. The test tubes, which were horizontally mounted inside the test section, had a 19.1 mm (0.75 in.) nominal OD and were 1067 mm (42 in.) long. Three tubes were tested during this study: a tube with a two-dimensional (2D) fin structure, a tube with a three-dimensional (3D) fin structure, and a smooth tube. The data were obtained at refrigerant saturation temperatures of 40 and 45°C (104 and 113°F) over a nominal heat flux range of 3155 to 63 100 W/m² (1000 to 20,000 Btu/h· ft²).

The final phase of this study was to compare test results for each tube type and to evaluate the effect of outer surface enhancement on shell-side condensation heat transfer performance. In addition, the experimentally determined heat transfer coefficients were compared with the corresponding models for each test tube.