HEAT TRANSFER CHARACTERISTICS OF THE HELICAL OSCILLATING HEAT PIPE WITH A CHECK VALVE

Abstract

The performance of the helical oscillating heat pipe (HOHP) is remarkable. It was improved by the check valve (CV). The scarcity of helical oscillating heat pipe with a check valve (HOHP/CV) literature necessitates. The purpose of this research is to investigate the heat transfer characteristics of the HOHP/CV with various working fluids such as R11, ethanol, and DI water. The HOHP/CV was constructed from copper tubes with inner diameters of 1.8, 2.4, and 3.4 mm. The condenser and evaporator were of the same length, but the straight tube was divided into three lengths, 600, 800, and 1000 mm, before bending to a helical shape. The coil diameter was set to 50 mm, and the pitch to 10 mm. It was tested at three angles of inclination: 30, 60, and 90 degrees. The heat sources were 60, 75, and 90 oC. The condenser temperature was set to 25 oC, and the flow rate was set at 20 liters/hour. The adiabatic section was fixed at 100 mm and a check valve was installed per tube, but this condition was divided into two positions, namely up-flowing and down-flowing direction of a working fluid. The thermocouple Type-K and data logger were used to record the inlet and outlet water temperatures in the condenser section. The highest heat flux was 12.84 kW/m2, which occurred at the 1000 mm tube length, inclination angle 90 degrees, inner diameter 3.4 mm, R11 as working fluid, and check valve installed on the down-flowing side.