Effect of Geometry and Dimensionless Parameters on Heat Transfer Characteristics of a Closed–end Oscillating Heat-pipe at Vertical Position

Abstract

This heat transfer characteristics of a closed-end oscillating heat-pipe (CEOHP) depend on a number of parameters. They are the number of turns, inner diameter of the tube, aspect ratio and the dimensionless parameters of heat transfer. The CEOHPs used to employ a copper tube with inner diameter of 0.66, 1.09 and 2.03 mm. The lengths of the evaporator, adiabatic and condenser sections were equal and changed to 50,100 and 150 mm. R141b was used as the working fluids with filling ratio of 50% by total volume. The meandering turns of 10, 20 and 40.The evaporator section was heated by hot water and the condenser section was cooled by distilled water. The experimental inclination angles were 0, 20, 40, 60, 80 and 90 degree from the horizontal plane. The controlled temperature at the adiabatic section of 50°C. When the system reached the steady state, the temperature and the flow rate of the cooling substance was recorded in order to calculate the heat transfer rate of the CEOHPs. The experimental results showed that the heat flux decreases with an increasing number of turns and decreases with an increasing aspect ratio. The heat flux increases with an increasing inner diameter. A correlation to predict the heat transfer rate at vertical position can be established.