Absorption-Desorption Compressor for Spaceborne/Airborne Cryogenic Refrigerators.

Abstract : The objective of this program was to analytically and experimentally determine the feasibility of using gas sorption processes as the basis for a compressor in a thermally activated aerospace cryogenic refrigeration system. The study involved materials investigations, development of static compressor design techniques, and the compatability of the static compressor with various refrigeration cycles. Lanthanum-pentanickel (LaNi5) was selected as the most suitable sorbing material because of its large hydrogen storage capability and favorable pressure-temperature characteristics. The ways in which the heat input and LaNi5 mass requirements of a compressor vary with hydrogen flow rate compressor heat capacity, and cycle time were analytically determined and experimentally confirmed. A compressor module designed to deliver 0.015 g/sec at a pressure of 50 atm (and reabsorb hydrogen at a pressure of 4 atm), over a cycle time of 450 seconds, was designed, constructed, and tested. The relative merits of various cryogenic cooling cycles were assessed. For 1 W of cooling at 20-30 K, the absorption compressor combined with a Joule-Thomson cooler was selected for further study. A spaceborne sorption compressor/J-T cooler for producing 1 W at 26 K was approximately sized. The overall system weight and power requirement were estimated to be 278 lbs. and 2.5 kW, respectively. Of the systems selected to produce 2 W at 77 K, none appear to offer any distinct advantages over existing mechanical coolers. (Author)