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An Experimental GM/Magnetic Refrigerator

  • G. F. Nellis
  • J. L. SmithJr.
Part of the Advances in Cryogenic Engineering book series (ACRE, volume 43)

Abstract

This paper describes the results obtained with an experimental prototype of a new type of cryocooler. The cycle employed by the device (a GM/magnetic cycle) uses two thermodynamically active substances: a compressible gas (helium) and a paramagnetic solid (Gadolinium Gallium Garnet or GGG). The two substances alternately regenerate one another, thereby overcoming the low temperature thermal saturation associated with a GM cycle while producing more refrigeration than a regenerative magnetic cycle. The experimental prototype utilizes a unique regenerative upper stage device to maintain the warm reservoir temperature seen by the GM/magnetic stage at the required 10–20 K. The pressure in the apparatus is controlled using a room temperature compressor and a system of valves. The device operates at a pressure level which is on the order of 4 atmospheres and uses a pressure ratio of approximately 2. The applied field in the GM/magnetic stage is controlled with a superconducting solenoid and a power supply. The maximum applied field imposed on the paramagnetic regenerator bed is 4 tesla.

The GM/magnetic refrigerator ultimately reached a no load temperature of 4.5 K while rejecting heat at 10.9 K. The device supplied 0.36 W of refrigeration at 6 K while rejecting heat at 15.4 K. The prototype clearly shows that the GM/magnetic cycle is an effective refrigeration cycle below 15 K.

Keywords

Gadolinium Gallium Garnet Expansion Valve Superconducting Solenoid Magnetic Stage Displacer Volume 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 1998

Authors and Affiliations

  • G. F. Nellis
    • 1
  • J. L. SmithJr.
    • 2
  1. 1.Creare, Inc.HanoverUSA
  2. 2.M.I.T. Cryogenic Engineering LabCambridgeUSA

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