Analysis of geyser boiling in liquid metal heat pipe: Impact on startup and shutdown, fuel temperature, and heat removal performance

Abstract

Liquid metal heat pipes are efficient heat transfer devices with diverse applications in various industries, including nuclear power plants. The use of liquid metal heat pipes in Heat Pipe-Cooled Nuclear Reactors (HPNRs) has been proposed for high-temperature heat utilization during electricity generation. This study experimentally investigates the impact of geyser boiling on the temperature of the fuel and its effect on heat removal performance using a sodium heat pipe. The investigation includes the influence of both increasing and decreasing power levels. The study reveals significant differences between operating the heat pipe in vertical and horizontal orientations. The thermal resistance and efficiency of the heat pipe are analyzed under different operating conditions. The results show that geyser boiling has a more pronounced impact in unsteady states compared to steady states, leading to non-periodic behavior and fluctuations in temperature and heat removal. The study emphasizes the importance of considering the changing liquid pool in liquid metal heat pipes to prevent or mitigate geyser boiling effects. Modifications to the optimal filling ratios of heat pipes are suggested to enhance stability and efficiency, making liquid metal heat pipes more feasible for HPNR applications.