Magnetic refrigeration apparatus with conductive heat transfer

Abstract

A magnetic refrigerator has a rotating magnetic wheel which includes a stack of spaced rings of magnetic material. Heat transfer plates of a high temperature heat extractor are interleaved with the magnetic rings and extend to a solid heat transfer conduit which leads to a high temperature terminal. Superconducting magnet coils are mounted to provide a magnetic field through the magnetic wheel at the position of the high temperature heat transfer plates. Low temperature extractor heat transfer plates are positioned outside of the magnetic field and interleave with the rings of the magnetic wheel to transfer heat thereto which is conducted from a low temperature terminal through a solid conduit. As the magnetic wheel is rotated, heat is drawn from a load and conducted through the solid material of the low temperature heat extractor to the magnetic wheel, is released when the material of the wheel is subjected to the magnetic field and transferred to the high temperature heat transfer plates, and is then conducted through the solid material of the heat transfer conduit to the high temperature terminal. Helium gas is sealed in the space surrounding the rotating magnetic wheel to transfer heat between the rings of the wheel and the heat transfer plates. Substantially all heat transfer in the magnetic refrigerator is thus provided by conduction through a solid, allowing start-up of the refrigerator without an initial charge of liquid helium to cool the refrigerator to cryogenic operating temperatures.