Thermal and Mechanical Properties of Magnetic Materials for Regenerative Magnetic Refrigeration on Hydrogen Liquefaction

摘要

Magnetic refrigeration which is based on the magnetocaloric effect of the solid material haspotential for a hydrogen liquefier with high thermal efficiency. Magnetic materials with rareearth elements were studied from the viewpoint of magnetic refrigerant. Several materialswere proposed in order to cover the wide temperature range above 20 K becausemagnetocaloric effect is large only around the magnetic transition temperature. The entropyof the magnetic material was obtained from the magnetization and specific heat measurement.The characteristics of magnetic entropy change were compared.Regenerative refrigeration cycle is required for the wide temperature refrigeration in order tomake better use of magnetocaloric effect. An active magnetic regenerator (AMR) is regardedas many cascaded magnetic refrigerators. An active magnetic regenerator with a Brayton-likecycle was discussed and the refrigeration performance was estimated in the case ofrefrigeration temperature below 70 K and magnetic material of DyAl2.