Condensation Characteristics of Flows in Newly Developed, Three-Dimensional Enhanced Heat Transfer Tubes

Abstract

Condensation heat transfer characteristics were studied experimentally to evaluate the heat transfer performance for copper heat transfer tubes (smooth and enhanced). Condensation tests were performed at 45 °C (saturation temperature); mass flux values in the range of 50 to 400 kg/(m2·s), with an inlet vapor quality of 0.8 and outlet vapor quality of 0.2. Single-phase heat balance verification found that the heat loss is less than 6 %, and the deviation between single-phase experimental results and various prediction correlations is less than 15 %. The condensation heat transfer coefficient increases with an increase in mass flow. When the mass flow rate increases, the turbulence of the liquid flow increases, and the liquid film becomes thinner; thermal resistance is reduced, and the heat transfer coefficient increases. Heat transfer values at lower mass velocities increase slightly with increasing mass flux values; however, at higher mass flux rates, the heat transfer increase is larger than that at low mass flux values. Experimental results determined that the performance factor ratio for most tubeside and outside condensation heat transfer conditions (enhanced tube/smooth tube) of the three-dimensional surfaces investigated in this study are greater than 1.