Experimental study on heat transfer performance of axially rotating heat pipe in steady state

Abstract

Rotating heat pipe has a broad application prospect in the field of heat dissipation of rotating machinery due to its high heat transfer performance. However, researches on the heat transfer mechanism of the rotating heat pipe are insufficient, which limits its application. A horizontal axially rotating heat pipe with the cylindrical inner surface was made and tested with water and ethanol as the working fluids. The filling ratios of 65.3%, 39.2%, and 26.1% were experimentally studied, respectively. Then the heat transfer performances of the rotating heat pipes below 1100 RPM were mainly studied. Visualization of the flow pattern in the rotating heat pipe was carried out to explain the mechanism of the flow and heat transfer characteristics in the rotating heat pipe in detail. The thermal resistance was used to evaluate the heat transfer performance. Further, the thermal resistances at the evaporator and the condenser sections were also explored to reveal the intrinsic heat transfer mechanism of the rotating heat pipe. It is concluded that the thermal resistance of the rotating heat pipe is typically in the range of 0.1–0.6 K/W. The thermal resistance decreases monotonously with the increase of heating power and cooling temperature. It can be found that the optimal filling ratio is about 39.2% for the rotating heat pipe. Due to the transition of flow pattern, there is typically a maximum value of the thermal resistance of the rotating heat pipe with the variation of rotational speed, especially at high heating power, high cooling temperature, and low filling ratio.