Dynamic Heat Exchanger for Pulse Tube Cryocooler

Period of Performance: 05/08/1998 - 11/07/1998


Phase 1 SBIR

Recipient Firm

Mitchell/stirling Machines/systems, Inc.
2550 NINTH ST - STE 207B
Berkeley, CA 94710
Principal Investigator


Pulse tube cryocoolers are the cutting edge of regenerative cryocooler development. A series of recent improvements (the orifice, various bypass arrangements) have brought pulse tube cooler performance into the range of Stirling and Gifford-McMahon coolers. A bi-directional Ranque/Hilsch vortex tube performs the functions of both heat-rejecting heat exchanger and orifice, offering further improvement in pulse tube performance. The bi-directional double Ranque/Hilsch vortex tube uses work that otherwise would be wasted in the pulse tube cooler's orifice to refrigerate the warm end of the pulse tube. The resulting temperature drop translates to an improvement in cooler capacity, efficiency and attainable no-load temperature. This novel device is simple, rugged and inexpensive; it has no moving parts. Preliminary experimental work demonstrates that a bi-directional Ranque/Hilsch vortex tube can be fabricated. Computer modeling shows that reduction of the heat -rejection temperature at the warm end of a pulse tube improves cooler performance, with greater improvement under higher load conditions. The technical challenge is to understand and optimize the relationship between vortex tube component dimensions and fluid flow requirements of a pulse tube cooler so as to achieve maximum performance improvement.