Testing of a Cryogenic Loop Heat Pipe for Large Area Cryocooling



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44th International Conference on Environmental Systems


Cryocooling of large areas such as optics, detector arrays, and cryogenic propellant tanks is required for future NASA space telescopes and exploration missions. A cryogenic loop heat pipe (CLHP) has a great potential to provide a closed-loop cooling system for this purpose and has many advantages over other devices in terms of reduced mass, reduced vibration, high reliability, and long life. A neon CLHP was tested extensively in a thermal vacuum chamber using a cryopump as the heat sink to characterize its transient and steady performance and verify its ability to cool large areas or components. Tests conducted included loop cool-down from the ambient temperature, startup, power cycle, evaporator heat removal capability, loop capillary limit and recovery from dry-out, low power operation, and long duration steady state operation. The neon CLHP demonstrated robust operation under steady state and transient conditions. The loop could be cooled from the ambient temperature to subcritical temperatures very effectively, and could start successfully by applying power to both the pump and evaporator without any pre- conditioning. It could adapt to changes in the pump power and/or evaporator power, and reach a new steady state very quickly. The evaporator could remove heat loads between 0.25W and 4W, yielding a power turn down ratio of 16. When the pump capillary limit was exceeded, the loop could resume its normal function by reducing the pump power. Steady state operations were demonstrated for up to 6 hours. The ability of the neon loop to cool large areas was therefore successfully verified.


The 44th International Conference on Environmental Systems was held in Tuscon, Arizona, USA on 13 July 2014 through 17 July 2014.
Jentung Ku, NASA Goddard Space Flight Center, USA
Franklin Robinson, NASA Goddard Space Flight Center, USA