Numerical Optimization of an Alkali-Metal Heat Pipe for Use in sCO2 Power Generation

The need for clean and sustainable energy in recent years has led to an increased demand for fusion reactors and supporting technology. Supercritical Carbon Dioxide (sCO2) power cycles are an efficient, compact, and cost-effective way to convert the large amounts of thermal energy produced by fusion reactors into usable energy. This study aims to investigate the performance of a metal-alkali heat pipe for moving the heat flux generated in a fusion reactor into a sCO2 cycle. Heat pipes are passive and closed system heat transfer devices that utilize the capillary forces of a wick and pressure changes across the device to move the working fluid. The heat pipe investigated would be integrated between the plasma facing components of the fusion reactor and the sCO2 heat exchanger, ultimately powering a closed Brayton cycle. Numerical analysis is performed on various performance limits including the capillary, sonic, and entrainment limits for differing wick geometries and sizes. Additional analysis is then conducted on the thermal conductivity of various wicks geometries and sizes. The findings are then compared and used to determine the optimal structure and geometry for maximum power transfer from a reactor into a sCO2 cycle. The simple design of heat pipes as well as their use in high temperature applications including fusion and turbo machinery as well as other sectors such as waste heat recovery and aircraft engines makes the technology worthy of investigation.