Experimental Investigation of Condensation Heat Transfer of Refrigerant R-134A in Helicoidal Pipes

Alternative refrigerant R-134a is considered to be ozone-friendly and a potential candidate for replacing the refrigerant CFC-12 in refrigeration and air-conditioning applications. This paper presents the experimental investigation of condensation heat transfer characteristics of superheated R-134a vapor flowing inside helicoidal pipes with the cooling water flowing through the annular helicoidal passage in a counter-flow direction. The heat transfer experiment was performed for R-134a mass flow flux ranging from 100 to 420 kg/m2s with the superheat of the inlet vapor of 2.8°C and 8.3°C, respectively. The cooling water flow Reynolds Rew ranges from 1500 to 12000. The Nusselt numbers were experimentally determined for a helicoidal pipe with the helix axis of vertical direction. The correlations for Nusselt numbers are developed based on the experimental results, which can be used as a reference in the design of helicoidal pipe condensers.