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Results for “Magnetocaloric effect”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

The magnetocaloric effect in dysprosium

The magnetocaloric effect in polycrystalline Dy was measured in the 84-280-K range in measuring fields from 1 to 7 T. These adiabatic temperature changes reflect structural changes in Dy with applied field and temperature, and include the first magnetocaloric data for a helical antiferromagnet. Above the Neel point (179 K) a field increase always caused heating; below the Neel point fields less than about 2 T cause cooling for some values of initial temperature. The largest temperature increase with a 7 T field occurs at the Neel point and at fields below 2 T near the Curie point. For refrigeration purposes the optimal working region for a Dy cooling element is field dependent.

Benford, S. M.↗
NASA NTRS1973

Magnetocaloric pump

Very cold liquids and gases such as helium, neon, and nitrogen can be pumped by using magnetocaloric effect. Adiabatic magnetization and demagnetization are used to alternately heat and cool slug of pumped fluid contained in closed chamber.

Brown, G. V.↗
NASA NTRS2004

Magnetocaloric Pumping of Liquid Oxygen

The field-induced force density on a magnetic fluid is proportional to the magnetic susceptibility times the gradient of the magnetic field squared. The direction of the force is towards increasing magnetic field (positive gradient). Applying a magnetic field to a magnetic fluid will result in a force from all directions towards the location of peak field. Since the magnetic field is conservative and there are no magnetic monopoles, the net field-induced force on any fluid of constant susceptibly will be zero. The only manner to obtain a nonzero net field-induced force is to vary the susceptibility of the fluid. At the gas/liquid interface of liquid oxygen, the susceptibility varies drastically, and the exploitation of the resultant large net forces. An alternative method of varying the magnetic susceptibility is to vary the temperature of the fluid. The magnetic susceptibility of paramagnetic liquid oxygen obeys the Curie-Weiss law: it is inversely proportional to temperature. By applying a temperature gradient in the presence of a symmetric magnetic field, a nonzero net force results. Much of the theory of the so-called Magnetocaloric Effect has previously been developed for and applied to ferromagnetic fluids, or ferrofluids, but is readily applied to paramagnetic liquid oxygen.

Immer, Christopher↗