Flexible, Gravity-Fed Heat Pipe

mechanical and fluid systems
Flexible, Gravity-Fed Heat Pipe (NPO-TOPS-47)
A flexible heat pipe for creating and maintaining local cryogenic environments
Overview
NASA's Jet Propulsion Laboratory has developed a flexible heat pipe for connecting high-capacity cryocoolers to large cryogenic systems. With today's cryocooler technology, cryogenic environments can be created and maintained locally, reducing cryogen transportation, logistics, and storage costs. While state-of-the-art systems use flexible braided copper heat straps to thermally link cryocoolers with cryogenic systems, these straps cannot be made short enough and flexible enough for use in larger systems requiring more than 50 W of heat extraction. If the heat strap is not flexible enough, thermal contraction will break the cryocooler; if the heat strap is not short enough, its thermal resistance will be too high to extract the required heat. With its flexibility and low thermal resistance, JPL's heat pipe is ideally suited for thermally linking high-capacity cryocoolers with larger cryogenic systems.

The Technology
JPL's flexible, gravity-fed heat pipe uses nitrogen, which condenses on a condenser attached to the cold head of a cryocooler. Using gravity, a flexible bellows delivers the liquid nitrogen to the radiation shield of a large cryogenic/vacuum chamber, where it evaporates at an evaporator, thereby cooling the shield. Another flexible bellows then returns the evaporated gas to the condenser for re-condensation. A flexible heat pipe of this design was fabricated and used to cool the radiation shield of a large cryogenic/vacuum chamber (1.8 m in diameter, 3.5 m in height) to ~100 K, extracting more than 50 W of heat. While large cryogenic facilities typically use liquid nitrogen systems for cooling, this requires a building-sized tank for storing the liquid nitrogen locally. Using cryocoolers together with JPL's heat pipe for cooling reduces the required space to about 2 m2 and simplifies installation and operation compared to conventional liquid nitrogen systems.
Left, test setup for JPLs heat pipe. Right, prototype condenser mounted on cryocooler cooling head. Prototype test results.
Benefits
  • Reduces cryogen transportation, logistics, and storage costs
  • Suitable use with cryocoolers extracting more than 50 W of heat
  • Simpler to install and use than conventional liquid cryogen systems

Applications
  • NASA and commercial environmental test facilities
  • Aerospace and military - storage and transportation of liquefied petroleum gas
Technology Details

mechanical and fluid systems
NPO-TOPS-47
NPO-49524-1
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