Thermal performance of rotating closed-loop pulsating heat pipes: Experimental investigation and semi-empirical correlation

A rotating closed loop pulsating heat pipe (RCLPHP) was experimentally investigated as a passive heat sink for rotary equipment cooling. The effects of heat input, rotational speed, filling ratio, and working fluid on the thermal resistance of RCLPHP were studied. Pure water and ethanol were used as working fluids with filling ratios of 30%, 50%, and 70% by volume, and the RCLPHP was tested at four rotational speeds: 200, 400, 600, and 800 rpm. The results showed that the best filling ratio for both water and ethanol is 50% and proved that the RCLPHP is able to work efficiently in a wide range of rotational speed. Moreover, it was observed that at the optimum filling ratio for ethanol and water, which is 50%, the decrease in thermal resistance at 800 rpm compared to 200 rpm was 5.4% and 13%, respectively. Such an enhancement in thermal performance indicates that these types of heat pipes are applicable for the purpose of cooling rotating devices. Moreover, a correlation is presented to estimate the amount of heat flow in RCLPHP with a maximum estimated error of 20%.