Experimental study on 100 hour-term performance of high-temperature sodium heat pipes

High-temperature heat pipes, utilizing alkali metals as working fluids, are essential heat transfer components in cooling systems of nuclear reactors. To assess the long-term isothermal behavior and heat transfer performance variation of high-temperature sodium heat pipes, this research presents the design and construction of a long- duration experimental test rig for high-temperature heat pipes. A 100-hour experimental investigation was conducted under operating conditions of 900 degrees C. The results demonstrate that the heat pipes can operate stably for extended periods after startup. The average temperature at the condenser section gradually increased, while the overall temperature difference fluctuation decreased. The magnitude of temperature difference reduction was measured to be 2.3 degrees C, and the effective thermal resistance of the heat pipe decreased to 0.0639 K/W. These results suggest an enhancement in both the isothermal performance and heat transfer capability characteristics of the sodium heat pipe after long-term testing. This study provides valuable insights for the design and assessment of high-temperature heat pipe systems in nuclear reactor cooling applications.