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Photoetched regenerator for use in a high frequency pulse tube.

Régénérateur photogravé pour utilisation dans un tube à pulsation à fréquence élevée.

Résumé

To produce refrigeration at 20 K in a single-stage regenerative cryocooler requires a combination of materials that possess high heat capacity within its operational temperature range. This has typically been accomplished using woven screens made of stainless steel or phosphorous-bronze operating in the 300 to 50 K range followed by a packed bed of spheres made of lead or other rare earth material. However, screens and particularly spheres produce high pressure losses within the regenerator. In a pulse tube operating at higher frequencies (40 to 60 Hz) where the pressure ratio is on the order of 1.3, the pressure loss becomes a more significant factor and prevents achieving 20 K. Therefore, Chesapeake Cryogenics, Inc. (CCI) is investigating the use of a gap-type regenerator employing both conventional materials and rare earths. The flow channels are created by a photochemical etching process to generate slots in disks. The disks are then stacked in the regenerator aligning the slots to produce parallel channels in the axial direction. The photochemical machining process may provide sufficient dimensional tolerances and repeatability resulting in uniform channels with heat transfer surface area approaching that of screens and spheres. Furthermore, this etching process can be applied to rare earth materials making the disks suitable for use at temperatures below 50 K. CCI has performed preliminary tests to determine the pressure loss under steady flow conditions, thermal conduction, and cryocooler performance using photoetched disks make of phosphorous-bronze and stainless steel to determine their suitability as replacements for screens and spheres. Results of these tests and a description of the flow channel geometry are presented.

Détails

  • Titre original : Photoetched regenerator for use in a high frequency pulse tube.
  • Identifiant de la fiche : 2008-1066
  • Langues : Anglais
  • Date d'édition : 14/06/2006