10 K Airborne Cryocooler and High Efficiency Heat Exchangers

Presented at the 16th International Cryocooler Conference, held May 17-20, 2008 in Atlanta, Georgia.Ball Aerospace has designed, built, and characterized a compact refrigeration system for cooling very low temperature infrared imagers. The system is robust, will be integrated into an airborne application, and can also be used in space environments. This paper reviews the completed system testing and results as well as component testing of the high efficiency, microchannel heat exchangers, which are an enabling technology for this cooler system. The system is a hybrid of complementary Stirling and Joule-Thomson (J-T) cycle cryocoolers. The Stirling is a version of our standard two-stage SB235E cryocooler with its second stage optimized for cooling below 20 K. The J-T cycle, which provides the refrigeration at 10 K, uses a reed valve equipped Oxford style compressor to drive a compact cold head which is precooled by the Stirling cooler. The cold head consists of three counter flow heat exchangers, a bypass valve, and an expansion valve packaged on a small diameter, mechanically robust cryostat