Thermal characteristics of rotating closed-loop pulsating heat pipe designed for rotating-type energy storage devices

This research was aim to investigate the thermal characteristics of the rotating closed-loop pulsating heat pipe (RCLPHP) designed for integrating onto rotating-type energy storage devices. The thermal characteristics beginning from the start-up state to the post-critical state were thoroughly observed. The RCLPHP was made from 1.78-mm inner diameter copper tube and it was bent to be 11 meandering turns. The evaporator section length was 50 mm, which was the same as of the condenser section. Working fluid was distilled water. Filling ratio was 50% of total volume. It was installed on a rig and oriented in vertical plane. Annular plate electrical heaters were used to supply heat input. The heat released from the condenser section to the ambient air at constant temperature of 25 ± 1 °C. The rotational speed was 70 rpm. It could be found that when the RCLPHP worked in the normal operating state, the evaporator and the condenser section temperatures fluctuated with obvious frequency and amplitude, and the internal phenomena of the working fluid could be implied as the slug-train. When the RCLPHP has reached the critical state, the condenser section temperature subsequently decreased. This is because the condensate is strongly pushed by the centrifugal force against the vapor flow direction, then the vapor plugs cannot flow to transfer the heat to the condenser section as usual.