R410A flow condensation inside two dimensional micro-fin tubes and three dimensional dimple tubes

Condensation heat transfer characteristics were experimentally investigated inside two dimensional helix micro fin (HX) tubes, three-dimensional dimple (1EHT) tubes and smooth (ST) tubes; while using R410A, for a variety of operating conditions and tube parameters. Tubes evaluated had a length of 2 m, with outer diameters of 9.52 and 12.7 mm; tube materials included copper and stainless steel. Experimental procedure was verified using a single-phase heat balance; with a comparison of results (enhanced tubes to smooth tube) being performed. The condensation experiments were performed at a saturated temperature of 35-45 degrees C; for the vapor quality range from 0.1 to 0.9; with mass fluxes that ranged from 70 to 450 kg m(-2) s(-1). Additionally, the effect of various parameters (mass flux, mean vapor quality, saturation temperature, tube thermal conductivity, tube diameter, and surface structure) on the tube side condensation heat transfer was evaluated. For the test conditions considered here the HTC enhancement ratio is in the range from 1.15 to 2.05 for the 1EHT tube and for the HX tube it ranged from 1.18 to 1.69; while the performance factor (PF takes into account the pressure drop) is 1.02-1.57 (1EHT) and 1.23-1.78 (HX). Heat transfer performance of the smooth tube was determined to be slightly affected by the thermal conductivity of the tube; however, for enhanced tubes there is a more dramatic increase in the HTC for an increase of thermal conductivity. Additionally, better heat transfer performance is demonstrated for smaller diameter tubes. Finally, the enhancement effect of the experimental parameters on the enhanced tubes was quantified through the use of a newly introduced evaluation factor. (c) 2021 Elsevier Ltd. All rights reserved.