Heat pipes, as highly efficient heat transfer components that combine evaporation and condensation, are widely used in fields such as nuclear energy and aerospace. If geyser boiling occurs in a heat pipe, it will cause temperature fluctuations, thereby affecting the safety of the entire heat pipe stack.

This study aims to analyze the heat transfer characteristics of geyser boiling in high-temperature sodium heat pipes.

Firstly, an experimental platform for high-temperature sodium heat pipe heating was established. Then, the heat transfer characteristics of the evaporation section of a heat pipe using liquid metal sodium as the working fluid were studied at different liquid level depths and various mesh sizes, and the temperature and pressure parameters of the sodium heat pipes under different power conditions were obtained. Subsequently, the variation pattern of the geyser boiling oscillation period with changes in heating power and the trends in the heat transfer coefficient of the evaporation section with variations in liquid pool depth and mesh count were summarized. Finally, based on the experimental data, a model for the heat transfer coefficient of the evaporation section of sodium heat pipe in single-phase convection and geyser boiling regions was proposed.

Experimental results show that the temperature oscillation period is shortened with the increase of heating power. At the end of the heat pipe startup phase, the oscillation amplitude significantly decreases. The new evaporation section heat transfer model shows a maximum error of 21% in the single-phase convection zone and a maximum error of 39% in the intermittent boiling zone.

The results indicate that, within a certain range, the higher the filling ratio and the higher the mesh count of the wire mesh, the better the heat transfer performance of the heat pipe. Additionally, when the heat pipe experiences geyser boiling, its heat transfer performance is significantly lower than that during normal operation.