An experimental Investigation of effectiveness of a closed-end flat heat pipe heat exchanger (CEFHPHE)

Abstract

The effectiveness of a closed-end flat heat pipe heat exchanger (CEFHPHE) was investigated experimentally. The CEFHPHE consists of three parts, which include the evaporator, adiabatic and condenser sections that the lengths were 300, 100 and 300 mm respectively. The standard copper tube with inner diameter of 8.6 mm and 0.46 mm thick was pressed to reform its cross sectional area for a flat tube, and then bent to many U-shapes, which was closed at both ends. The water was used for working fluid with filling ratios of 45% of internal volume. In experiments, hot air was used for supplying the heat to the evaporator section with different temperatures (105-145oC), and different velocities (0.5-2.0 m/s). Fresh air was used for cooling condenser section with temperature approximately 30oC, and was kept constant velocity at 0.5 m/s. The experimental results indicated that the effectiveness of CEFHPHE increase with the inlet hot air temperature, and decrease with the increase of hot air velocity. In addition, the effectiveness of the CEFHPHE obtained from the experiments varied between 0.35 and 0.74.