CFD simulation based on film model of high temperature potassium heat pipe at different positions: Horizontal, vertical, and 45° inclined

High temperature heat pipe is an ideal technical solution for microreactors applied for space missions, planet surface, and the small electricity markets on the ground. By using heat pipes, fission heat can be transferred passively and the structure of microreactor is highly simplified as the pumps, pipelines and coolant system are no longer needed in reactor system. For space reactors, because there is no gravity to drive working fluid in the heat pipe, wick structure is used to provide capillary force to generate driving head. However, for the microreactors operating on planet surface or on the earth, high temperature heat pipe is proved to have different thermal behavior compared to weightless environment. Due to gravity, the heat transfer characteristics varies from operation positions, including horizontal, vertical, and inclined positions. This paper aims to develop a general CFD model for heat pipe with wick structure that can predict the thermal behavior at different inclinations. The thermal conduction through heat pipe shell, liquid film on the inner surface, and the formation of liquid reservoir at the bottom of heat pipe are considered in this model. Simulation results are compared with experimental data, showing that the numerical model is able to predict temperature distribution along the heat pipe, especially the temperature increase at the beginning part of evaporator when heat pipe is vertical or 45° inclined. Therefore, this paper can provide a reference to the design and analysis of high temperature heat pipe used in micronuclear reactors.