Magnetocaloric Refrigeration.

The magnetocaloric refrigerator uses the adiabatic temperature response of ferromagnetic materials rare-earth metals in a high magnetic field. A mathematical model of a reciprocating magnetic refrigerator having an active element of a rare-earth metal predicted that a 60-K temperature span could be achieved. Based on the models results, an experimental refrigerator was fabricated and the thermal characteristics of an active regenerator in a reciprocating apparatus were measured. The active material was gadolinium, which has a Curie temperature of 293 K and was formed into an embossed ribbon geometry. Significant regeneration in the magnetic material was observed, and a 50-K temperature span was achieved. A cold end temperature of 246 K was measured. The results indicated that the active regeneration concept can successfully produce magnetocaloric refrigeration at temperatures near the Curie temperature of the material, and the measured temperature span verified the mathematical model developed to describe the process. Further, if the active magnetic element were a combination of several rare-earth metals having significant magnetocaloric effects at decreasing temperatures, the possibility exists for producing a single-stage magnetic refrigerator that could operate over a very large temperature span.