Experimental study of single-phase flow and heat transfer characteristics for a horizontal internal helically-finned tube

Abstract

Helical fin roughness has been extensively used in the large heat exchangers. The single-phase flow and heat transfer characteristics in an internal helically-finned tube are determined experimentally in this study. The main parameters of the internal helically-finned tube is fin height to the tube inside diameter ratio (0.022), number of fins (60) and helix angle (45°). The adiabatic friction factor was collected and heat transfer experiments were conducted in a flooded evaporator with R134a boiling outside the tube. The aqueous ethylene glycol was used as the working fluid and the tests were performed with Prandtl number from 17.8 to 36.4 and Reynolds number from 8000 to 34,000. In the flow parameter range, this enhanced tube provided a 2.79-3.56 heat transfer enhancement ratio and 1.58-2.3 for friction factor and efficiency index varied from 1.77 to 1.55. This study offers the reference on the design of heat exchangers.