Condensation heat transfer and pressure drop of R22 in 5-mm diameter microfin tubes

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 7degrees, and the other had a helix angle of 18degrees. 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 degreesC condensation temperature for 200-500 kg/m(2)s refrigerant mass fluxes with 5-30 degreesC inlet superheat degrees and 2-3 degreesC outlet subcooling degrees. The effects of helix angle and mass flux on the heat transfer coefficients and pressure drop are presented and discussed.