High temperature capillary pumped loops for thermionic power systems

Abstract

A high temperature capillary pumped loop (CPL) is being developed for thermal control applications in space power systems. Space power systems where capillary pumped loops can be used include the SP‐100 system, the SDIO Multi‐Megawatt system, and the Air Force Thermionic Nuclear Power System. The advantages of a CPL include the ability to subcool liquid before it enters the evaporator, reducing the chance of boiling in the evaporator artery. A second major benefit is that only the evaporator and condenser need a wick, simplifying fabrication of the adiabatic section. Finally, it is easy to connect multiple evaporators and condensers with a single vapor and liquid line. Several high temperature capillary pumped loops were fabricated with sodium as the working fluid. With a 1.75 m long vapor line, a CPL carried 5300 W near 1000 K, with an evaporator heat flux of 60 W/cm2. The evaporator was elevated 15 cm above the condenser, which was the maximum possible due to mechanical limitations of the experimental setup.A high temperature capillary pumped loop (CPL) is being developed for thermal control applications in space power systems. Space power systems where capillary pumped loops can be used include the SP‐100 system, the SDIO Multi‐Megawatt system, and the Air Force Thermionic Nuclear Power System. The advantages of a CPL include the ability to subcool liquid before it enters the evaporator, reducing the chance of boiling in the evaporator artery. A second major benefit is that only the evaporator and condenser need a wick, simplifying fabrication of the adiabatic section. Finally, it is easy to connect multiple evaporators and condensers with a single vapor and liquid line. Several high temperature capillary pumped loops were fabricated with sodium as the working fluid. With a 1.75 m long vapor line, a CPL carried 5300 W near 1000 K, with an evaporator heat flux of 60 W/cm2. The evaporator was elevated 15 cm above the condenser, which was the maximum possible due to mechanical limitations of the experimental s...