Condensation Heat Transfer and Pressure Drop of R22 in 5-mm Diameter Microfin Tubes

Abstract

Condensation heat transfer coefficients and pressure drops of R22 in two microfin tubes with 5-mm outside diameter (OD) and a smooth tube with 5.4-mm OD were experimentally investigated. The main difference in geometries of the two microfin tubes was the helix angle: one had a helix angle of 7°, and the other had a helix angle of 18°. The test section had a length of 3.0 m and was divided into five subsections to achieve the local heat transfer coefficient. The condensation tests were carried out at 45 °C condensation temperature for 200−500 kg/m2s refrigerant mass fluxes with 5−30 °C inlet superheat degrees and 2−3 °C outlet subcooling degrees. The effects of helix angle and mass flux on the heat transfer coefficients and pressure drop are presented and discussed.