Effect of Centrifugal Acceleration on Heat Transfer Characteristics of Rotating Closed-Loop Pulsating Heat Pipes

Abstract

The objective of this paper is to qualitatively study the effect of centrifugal acceleration on heat transfer characteristic of a rotating closed-loop pulsating heat pipe (RCLPHP). RCLPHP can be applied to cool rotating devices, such as disc brake or steam turbine. It improves the lifetime and reduces the wear of the device. In recent studies, effects of several parameters on thermal performanceof CLPHP have been investigatede.g. inner diameter, length of evaporator section, meandering of turn and working fluid. Some researchersderivedthese parameters in dimensionless form, and then established correlation to predict thermal performance of CLPHP at specified inclination angles. Another parameter that affects rotating or moving heat pipe is centrifugal acceleration. The induced internal centrifugal acceleration of the RCLPHP affects the circulation of working fluid. When flow direction of condensate is in the same direction as the acceleration,the centrifugal acceleration is defined to be positive. In turn,thecondensate is in thecounter-flow direction to the acceleration, if centrifugal acceleration is negative. This acceleration affectsthe circulation of liquid phase. Because of heavier mass of the liquid, most of itaccumulatedat the end part of evaporator section. When the RCLPHPis heated, working fluid in this section changes from liquid to vapor phase. Then it circulates to condenser section, or another end, and condensed. When centrifugal acceleration is increased, thermal resistance decreases. The condensate can quickly circulate to evaporation sectionbecause working fluid velocityis higher than those at lower acceleration. In the future, researches to quantitatively study on the effects of centrifugal and parameters which related to the thermal performance of RCLPHP will be further conducted.