CONDENSATION HEAT TRANSFER AND PRESSURE DROP OF R22 IN 5 MM MICRO-FIN/SMOOTH TUBES

摘要

Condensation heat transfer coefficients and pressure drops of R22 in two micro-fin tubes with 5 mm OD and a smooth tube with 5.4 mm OD were examined. The main difference in geometries of the two micro-fin tubes was the helix angle; one had a helix angle of 7° and the other one had a helix angle of 18°. The test section had a length of 3.0 m and was divided into five sub-sections to achieve the local heat transfer coefficient. The condensation tests were carried out at 45 °C condensation temperatures for 200-500 kg/(m~2-s) refrigerant mass fluxes with 5-30°C inlet superheat degrees and 2-3°C outlet sub-cooling degrees. The effects of helix angle and mass flux on the heat transfer coefficients and pressure drop were presented and discussed.