| Abstrakt: |
This research was studied to determine the reason for the occurrence of the critical state of the rotating closed- loop pulsating heat pipe (RCLPHP) and to identify the effect of the meandering turn numbers on the maximum heat flux (MHF) of the RCLPHP. Furthermore, the phenomena happening inside the RCLPHP were presented by considering the characteristic temperature of each section of the heat pipe. The RCLPHP was made from the capillary tube which has a diameter of 1.78 mm, evaporator section length of 50 mm, the meandering turn number was varied within 11, 22, and 33 turns, and rotational speed of 220 rpm. Water and R123 were used as the working fluid. In the experiment, the heat input was increased in a small step with a value of heat input of 20 W. The temperatures of the evaporator and the condenser sections of the RCLPHP were recorded. The experiment was started from the start-up state to the critical state. The criteria to determine that the RCLPHP has reached the critical state consisted of a decrease in the condenser section temperature, an increase in the thermal resistance, and a decrease in the heat throughput compared to the prior step of the heat input. In addition, the results indicated that when the meandering turn number increased, although the maximum heat throughput increased, the MHF decreased for both working fluids of water and R123. This is because when the meandering turn number increased, the pressure drops from the frictional force between working fluid and inside surface of tube also increased. Thus, the flow rate of the working fluid obviously decreased. This led the transition of the internal flow regime of the working fluid from slug flow to annular flow to be more difficult and the maximum heat throughput consequently increased. However, since the rate of an increase in the heating area was very higher than the rate of an increase in the maximum heat throughput in the evaporator section, the MHF subsequently decreased. [ABSTRACT FROM AUTHOR] |
