The magnetic refrigeration technique based on the magnetocaloric effect (MCE) has attracted increasing interest because of its high efficiency and environment friendliness. in this article, our recent progress in exploring effective MCE materials is reviewed with emphasis on the MCE in the LaFe13-xSix-based alloys discovered by us. These alloys show large entropy changes over a wide temperature range near room temperature. The effects of magnetic rare-earth doping, interstitial atoms and high pressure on the MCE have been systematically studied. Special issues, such as appropriate approaches to determining the MCE associated with the first-order magnetic transition, the depression of magnetic and thermal hysteresis, and the key factors determining the magnetic exchange in alloys of this kind, are discussed. The applicability of giant MCE materials to magnetic refrigeration near ambient temperature is evaluated. A brief review of other materials with significant MCE is also presented.

Recent Progress in Exploring Magnetocaloric Materials

The seminal study by Brown in 1976 showed that it was possible to use the magnetocaloric effect to produce a substantial cooling effect near room temperature. About 15 years later Green et al. built a device which actually cooled a load other than the magnetocaloric material itself and the heat exchange fluid. The major breakthrough, however, occurred in 1997 when the Ames Laboratory/Astronautics proof-of-principle refrigerator showed that magnetic refrigeration was competitive with conventional gas compression cooling. Since then, over 25 magnetic cooling units have been built and tested throughout the world. The current status of near room temperature magnetic cooling is reviewed, including a discussion of the major problems facing commercialization and potential solutions thereof. The future outlook for this revolutionary technology is discussed.

Thirty years of near room temperature magnetic cooling: Where we are today and future prospects

A method and system are described herein for producing a magnetic field emission structure (104a). In one embodiment, the method includes the steps of: generating a plurality of magnetic fields (102a); and exposing a plurality of locations on a magnetizable material (104a) to the plurality of magnetic fields to create a plurality of magnetic field sources, the plurality of magnetic field sources having polarities in accordance with elements of a code corresponding to a force function.

Field emission system and method

The magnetic refrigerating device according to one embodiment includes a fixed container filled with a refrigerant, the fixed container including a magnetic material container that is filled with a magnetic material and that can move in the fixed container and an elastic member provided at the end of the magnetic material container. The magnetic refrigerating device also includes a magnetic-field applying/removing mechanism that is provided at the outside of the fixed container, and that can apply and remove a magnetic field to and from the magnetic material and can generate a magnetic torque to the magnetic material container in moving direction of the magnetic material container.

Magnetic refrigerating device and magnetic refrigerating system

A magnetic attachment system is described. The magnetic attachment system has a first plurality of magnetic sources arranged in accordance with a first pattern and a second polarity of magnetic sources arranged in accordance with a second pattern. The first pattern and second pattern are self-complementary, where the magnetic attachment system will correlate and align with a duplicate magnetic attachment system.

Magnetic attachment system

A magnetic refrigeration device, which can be reduced in size and improve magnetic refrigeration efficiency, and a magnetic refrigeration system can be provided. The magnetic refrigeration device has a heat exchanger vessel of a helical structure filled with magnetic particles having a magnetocaloric effect, a magnetic circuit, a driving unit configured to relatively move the heat exchanger vessel and the magnetic circuit so that a magnetic field can be applied to and removed from the magnetic particles, a low temperature side heat exchanging unit, a high temperature side heat exchanging unit, a refrigerant flow device, and a refrigerant circuit formed by connecting the heat exchanger vessel, the low temperature side heat exchanging unit, the high temperature side heat exchanging unit, and the refrigerant flow device by a pipe for circulating a refrigerant. The magnetic refrigeration system is arranged to use the magnetic refrigeration device.

Magnetic refrigeration device and magnetic refrigeration system

According to the embodiment of the present invention, a heat exchanger is provided with a container having a heat transport medium introduced therein, and a plurality of heat exchanging elements, which are provided at predetermined intervals inside of the container. The heat exchanging elements are provided at the front and the rear in the direction in which the heat transport medium flows such that at least some of the heat exchanging elements do not overlap each other when viewed from the direction in which the heat transport medium flows.

Heat exchanger and magnetic refrigeration system

To verify effectiveness for a magnetic refrigerant, we have fabricated spheres of La(Fe0.86Si0.14)13 by a rotating electrode process (REP). The Curie temperature of the spheres was increased up to around room temperature by hydrogen absorption. Putting these spheres into an active magnetic regenerator (AMR) test module, the temperature span of 16 K in the vicinity of room temperature was obtained in a steady state. Consequently, it has been confirmed for the first time that the La(Fe0.86Si0.14)13 spheres perform as an excellent material for the AMR.

http://iopscience.iop.org/article/10.1143/JJAP.46.L154/pdf

Active Magnetic Regeneration Behavior of Spherical Hydrogenated La(Fe0.86Si0.14)13 Fabricated by Rotating Electrode Process

We have fabricated spherical La(FexSi1−x)13 compounds by a rotating electrode process (REP) to provide suitable refrigerants for active magnetic regenerator (AMR)-type systems. In the as-prepared state, the cross section exhibits a dendritic metallographic structure composed of two phases of α-Fe-based alloy with Si and LaFeSi equiatomic compound. After annealing at 1323 K for 5 days, the spheres become a single phase of La(FexSi1−x)13. From the temperature dependence of magnetic entropy change for the hydrogenated spheres, it has been confirmed that the hydrogen concentration in the spheres is homogeneous. In addition, it has also been demonstrated that the itinerant-electron metamagnetic transition appears in the spheres with the higher Fe concentration. Consequently, the spherical La(FexSi1−x)13 fabricated by the REP are suitable for AMR-type refrigerations.

Shiori Kaji

Papers

Magnetic refrigerating device and magnetic refrigerating system

Magnetic refrigeration device and magnetic refrigeration system

Heat exchanger and magnetic refrigeration system

Active Magnetic Regeneration Behavior of Spherical Hydrogenated La(Fe0.86Si0.14)13 Fabricated by Rotating Electrode Process

Magnetocaloric effect in spherical La(FexSi1−x)13 and their hydrides for active magnetic regenerator-type refrigerator