Magnetic refrigeration and heat pumping design options

Magnetic cycles have potential for refrigeration and heat pumping from temperatures of 4 K or below to over 500 K. Theoretical studies have repeatedly indicated that demagnetization refrigeration has significant potential advantage over gas expansion or vaporization refrigeration. Tests of physical models have shown that there are many design problems to be overcome. However, these tests have not exposed any fundamental reasons why high efficiency and capacity predicted by analysis cannot be realized. Adequate solutions to all design problems have not been found, and practical machines have not been demonstrated. Continued study, testing, and exchange of ideas is necessary for rapid development of this technology. Most studies conducted to date have focused on a single magnetic refrigerator design concept and on problems associated with that configuration. Performance considerations and design options are discussed. Concepts discussed should be applicable to the entire range of possible cycle temperatures, although most results and conclusions are derived from high-temperature magnetic heat pump studies at the Idaho National Engineering Laboratory.