Low-temperature magnetic refrigerator

An about 4 to about 20 K. refrigeration apparatus comprising:

• a generally U-shaped housing having a base and two arms, said housing comprising electromagnets on the insides of the tips of the arms, said electromagnets being spaced opposed to one another;
• a hermetically sealed container, said container comprising a wheel-shaped part and a rotatable driveshaft enclosing drive post shield perpendicular thereto at the center thereof, said wheel-shaped part comprising a rotatable rim portion, said rim portion containing a ring of fluid contactable magnetic material disposed therein, said driveshaft and said ring being substantially frictionlessly rotatable within said container;
• means for affixing said driveshaft within said drive post shield to said ring of magnetic material;
• means for rotating said driveshaft and thereby rotating said ring of magnetic material at a selected speed;
• first means for heat exchange comprising means for contacting a first fluid with a first portion of said ring of magnetic material disposed substantially outside a magnetic field produced by said electromagnets;
• and
• second means for heat exchange comprising means for contacting a second fluid with a second portion of said ring of magnetic material disposed inside said magnetic field.