Impact of Small Regenerator Structural Flaws on the Performance of Miniature Pulse Tube Cryocoolers

Presented at the 16th International Cryocooler Conference, held May 17-20, 2008 in Atlanta, Georgia.Miniature cryocoolers are suitable for space applications and installation in portable devices. They can also be useful as final stages for applications where small cooling loads must be carried at temperatures lower than that required by the primary load. Strong regeneration, near plug-flow regime in the pulse tube and good flow control are essential for these cryocoolers to function. Miniature cryocoolers that use wire mesh as regenerator filler generally have a much larger ratio of regenerator filler pore size to regenerator diameter than their larger counterparts. For this reason, the significance of gaps existing between the porous regenerator filler and the interior wall of the regenerator shell will likely be greater for miniature cryocoolers. These gaps provide a low resistance flow path which may decrease the effectiveness of the regenerator. In this investigation the effects of such gaps on the performance of miniature pulse tube cryocoolers are examined using 2-D CFD simulations. Miniature scale pulse tube cryocooler designs whose suitability for cooling under ideal conditions that have been theoretically demonstrated are used as the basis for this study. The results confirm that extra precision and robustness are needed for miniature cryocoolers