Experimental investigation of condensation heat transfer of refrigerant R-134A in helicoidal pipes

摘要

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 investigaiton 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/m~2s with the superheat of the inlet vpaor of 2.8 deg C and 8.3 deg C, respectively. The cooling 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.