A special-shaped sodium heat pipe with a “bridge-type” artery for coupling free-piston Stirling generator and fission reactor

The nuclear-powered free-piston Stirling generator (FPSG) by using heat pipes as heat transfer devices has significant potential for future applications in the deep space exploration. Due to the compact size of the FPSG, it is very difficult to directly insert the cylindrical heat pipe into the heat head to transfer heat, which has been a challenge for application in such a system. Here, a special-shaped heat pipe is designed to match the heat head. In this design, the surface of the heat head was used as the condensing surface and a “bridge-type” composite artery was used to transfer the liquid sodium from the condensing surface to the evaporating surface, which could greatly simplify the structure and improve the capillary limit. A simplified model for arterial wick was proposed to predict the artery geometrical parameters and capillary limit and the performance of the startup and steady state were experimentally investigated. It successfully transmitted about 4 kW of heat with a tilt angle of −35°, verifying the feasibility of the new structure. The effect of different cooling conditions and inclinations were also investigated. To ensure that the heat pipe was fully activated, it was necessary to meet the minimum input power under different cooling conditions.