Bending of heat pipes is an inevitable occurrence in heat pipe cooled reactors designed for shadow cone shielding and the reduction of neutron leakage. Geyser boiling, characterized by periodic fluctuations in wall temperature during heat pipe operation, is common in conventional straight heat pipes. Temperature fluctuations in straight heat pipes can reach up to hundreds of degrees Celsius, which has an adverse impact on the heat transfer performance and stable operation of heat pipes.

This study aims to analyze the impact of high-temperature sodium heat pipe bending on heat transfer performance.

Both experimental and numerical methods were applied to the analysis of geyser boiling effect of bent heat pipe in heat pipe cooled reactor. Firstly, an experimental platform was established to conduct comparative tests on straight and bent heat pipes under vertical conditions. The heat pipes were heated by electromagnetic induction heating and cooled by natural convection and radiation. The wall temperatures of the straight heat pipe and bent heat pipe were compared to analyze the effect of bending on geyser boiling phenomena. Meanwhile, a multiphase flow model was established using Fluent to simulate the internal flow within both straight and bent heat pipes.

The experimental results indicate that, under identical operating conditions, the bent heat pipe exhibits significantly lower temperature fluctuation amplitude and period during geyser boiling compared to the straight heat pipe. The simulation results reveal that the presence of the bend induces a stable stratified flow regime, replacing the slug flow typically observed in straight pipes, thus mitigating the effects of geyser boiling. The maximum wall temperature decreases by 15 ℃ in bending heat pipe.

The findings of this study demonstrate that bending the high temperature sodium heat pipe can effectively suppress geyser boiling, which is beneficial for enhancing the heat transfer performance and operational stability of heat pipe cooled reactors.