This NASA SBIR proposal is concerned with the development of a refrigerator for use on spacecraft under microgravity conditions for the storage of biological samples. The proposed refrigerator is novel form of pulse tube refrigerator generating refrigeration at two different temperatures, say 0 degree and -50 degree C. The refrigerator works on an open cycle releasing a flow of cold pressurized working fluid for convective cooling as well as a cold plate at substantially lower temperatures for conductive or convective cooling. The gaseous working fluid is the spacecraft cabin environment gas. No lubricants or other pollutants are used in the refrigerator to contaminate the gas in passing through it. There are few moving parts in a pulse tube refrigeration unit except the compressor require to produce the pulse necessary to operate the refrigerator. The compressor can be driven by a free piston Stirling engine integrated with the refrigerator using common pistons. The Stirling engine can be energized by a waste heat stream at an elevated temperature, by concentrated solar energy, or by any other heat source (radioisotope or electric resistance heating). Alternatively, the refrigerator motor may be driven by an electric motor.
Potential Commercial Applications:The proposed refrigerator with gaseous working fluid may be made at low cost and is anticipated to have the same performance and durabilitya s present vapor-compression refrigerators. Numerous commercial applicationof the refrigerator may be anticipated in environmentally sensitive situations involving aircraft, spacecraft,underwater vehicles, marine vehicles, hospital crews and commercial or domestic establishments.
