Numerical investigation on thermal behavior of high temperature heat pipe based on thermal resistance network model

Abstract

High-temperature heat pipes are often used as heat exchangers in nuclear reactors because of their remarkable advantages in terms of thermal conductivity, isothermal properties, and self-actuation. To ensure the safe operation and efficient heat transfer of a reactor system, it is necessary to analyze the transient heat transfer performances of heat pipes. The working temperature range of the high-temperature heat pipe is 800–1,300 K when sodium is selected as the working fluid. A network system consisting of the thermal resistances can be used to analyze heat pipe transients. For a high-temperature thermosiphon, the existence of a liquid pool and a liquid film will affect the overall thermal resistance and temperature distribution. In this paper, a thermal resistance network model including convection and phase changes was established, a linear differential equation was established based on the energy conservation equation, and code was developed based on this differential equation to solve the thermal resistance and temperature field equations of the heat pipe. It was found that the temperature of numerical calculation in each region was in good agreement with the experimental results. To simulate a complex reactor environment, a power wave was introduced to explore the influence of the heat source on the thermal resistance and temperature field. It is found that with the increase of heating power, the temperature of each region of the heat pipe also increases, and the time required for the heat pipe to reach equilibrium decreases. In addition, the variations of the thermal resistance and temperature field with different heat pipe sizes and cooling modes at the condensation section under variable-power conditions were explored.