Recent testing of diaphragm-defined, Stirling-cycle machines and components has demonstrated cooling performance potential, validated the design code, and confirmed several critical operating characteristics. In addition, substantial progress has been made in several hardware development projects targeting long-life, spaceborne cryocoolers and terrestrial heat pump applications.
A “breadboard” cryocooler was rebuilt and tested from cryogenic to near-ambient cold end temperatures. There was a significant increase in capacity at cryogenic temperatures and the performance results compared well with code predictions at all temperatures. Further testing on a “breadboard” diaphragm compressor validated the calculated requirement for a minimum axial clearance between diaphragms and mating heads. A separate apparatus containing a colinear pair of diaphragms and linear oscillating drive motors demonstrated excellent vibration cancellation for this motor and drive electronics design.