A Pulse Tube Cryocooler with 300 W Refrigeration at 80 K and an Operating Efficiency of 19% Carnot

An electrically driven pulse tube cryocooler that produces 300¶W of refrigeration at 80¶K is now available from Praxair Inc. The unit reflects efforts by Praxair R&D to meet the need for higher operating efficiencies required by commercial HTS (High Temperature Superconducting) applications. A unique in-line design philosophy along with proprietary technology developed at Praxair allows losses in the regenerator and pulse tube to be minimized, thus achieving an efficiency of 19% of Carnot. A dual opposed ‘pressure wave generator’ from CFIC, Inc. supplies the acoustic power to the cold head. Experimental results from refrigeration performance tests and load curves are presented. Praxair is working on the development of a family of units in this geometry with incremental refrigeration capacities. The intended application of these units to satisfy internal and external market needs, particularly in industrial gas liquefaction and HTS cooling is discussed. The cryocoolers have an integrated cold heat exchanger designed for forced convective cooling, condensation, and subcooling of a cryogenic fluid such as nitrogen. This allows convenient and direct integration into an HTS cooling system—for example, an HTS cable.