Heat Transfer and Pressure Drop Characteristics During R22 Evaporation in an Oval Microfin Tube

摘要

An experimental study on R22 evaporating heat transfer in round and oval microfin tubes has been performed. The oval tube was an elliptic tube of axis ratio 1:15 which was fabricate from the round tube with an outer diameter of 9.52 mm and 18 deg helix angle counterclockwise. The test section was a straight horizontal tube of 0.6 m in length and was heated electrically by a tape heater wound on the tube surface. Heat flux of 12 kW/m~2 was maintained constant and the range of refrigerant quality was 0.2-0.8. The tests were conducted for evaporation at 15 deg C for 30-60 kg/h mass flow rate (mass flux based on the oval tube: 150-300 kg/m~2s) and the installation angles of the oval tube were varied between 0 and 135 deg in the circumferential direction.