Experimental Analysis on Thermal Performance of Radially Rotating Heat Pipes at Different Filling Ratios

Radially rotating heat pipes (RRHPs) are novel, efficient heat transfer devices with high thermal conductance and simple structure for rotary equipment. Filling ratio is of key relevance to the heat transfer of RRHPs. In this paper, the thermal performance of the RRHP at different filling ratios of 25%, 50% and 75% are experimentally investigated. RRHPs with copper shell and distilled water as working fluid were tested at heat input power ranging from 50 W to 200 W and average centrifugal accelerations ranging from 100 g to 1000 g. The experimental results showed that the optimum filling ratio was 25% at most operating conditions but 50% at high centrifugal acceleration and high heat input. The difference of thermal resistance between filling ratio of 25% and 50% was less than 15% for most operating conditions, except for conditions of high accelerations and high heat inputs. Interestingly, periodic temperature oscillations were observed at low accelerations and intermediate heat inputs for filling ratio of 75%, suggesting the Geyser boiling and intermittent churn flow would also occur in RRHPs.