Sorption Refrigeration Development

The Jet Propulsion Lthoratory (JPL) has been involved in cryogenic refrigeration development for the National Aeronautics and Space AdminisUation (NASA) since 1979. Witi the help of NASA, Southern California Gas Company, Ford Automotive, and Aerojet General, we have spun off Ma technology for cmnmerciai air conditioning since 1990. In all, JPL has fabricated and successfully tested the following sorption refrigerators: physicai solid adsorption systems (helium, nitrogen, krypton, R22, R134a, and ammonia), chemical solid absorption systems (hydrogen, nitrogen, and oxygen), and liquid absorption systems (ammonia and RI 34a). Two hydrogen cbemisorption systems for cooling to 10 K (-263 ‘C) and 2S K (-248 “C) are prcsmntly flight qualified &nd ready to COOI detec&m for a NASA Shuttle mission and a Nationai Science Foundation (NSF) Balloon Flight. All of these systems operate on the same b~ic principle of absorbing a refrigerant gas at a lower temperature, typically near room temperature, and then desorbing, or venting, the gas at a much higher pressure when heated an additional 100 to 200 ‘C. Precooking and expansion of the gas then craatea refrigeration with essentially no wear-related moving parts. Of particular intertst are two commercial developmental projects. One system being built by Aerojet and licensed from JPL/Caltech, is a 7.2-ton solid adsorption air conditioner that will be installed on a subway train in Los Angeles. This system wili be powered by the waste heat from the train’a electro-resistive braking system, and is scheduled for completion in 19%. Another sorption project being pursued by Ford Automotive and the Soutiern California Gas Company at JPL is the development of high performance, compact iiquid absorption systems that can bo powered by gas ha or automotive exhaust waste heat. Although the performance projections are not quite as high as those for the solid adsorption systems, tbe liquid R134a and ammonia absorption comprwsion systems we extremely simple, inexpensive, and light weight. Furthermore, the systems are insensitive to gravity vector changes, thus potentially fitting some mobile heat-activated applications, where some perfo~ce can be sacrificed, but cost is criticai.