What is the development direction of magnetic refrigeration and what is the principle of magnetic re

At present, magnetic refrigeration is mainly used in small-scale installations such as very low temperature and liquefied helium. Although the basic theory of magnetic refrigeration is not yet mature due to the limitations of many reasons, magnetic refrigeration will eventually become a new refrigeration method with great potential in the future because of its high efficiency and pollution-free characteristics, and the deepening of the magnetic refrigeration cycle theory will vigorously promote the application of magnetic refrigeration technology in space development and civil technology, and open up a broader prospect for magnetic refrigeration.

In addition, magnetic refrigeration refrigerators have been successfully developed.

According to the experiment, the refrigerant used in refrigerators and air conditioning units, Freon, will pollute the environment, while the refrigerator made by the principle of magnetic refrigeration not only does not damage the environment, but also has 40% higher efficiency and 25% lower cost than Freon refrigeration.

In addition, magnetic refrigeration has a wide range of applications in defense fields such as space and nuclear technology: in this field, refrigeration equipment is required to be lightweight, low vibration and noise, easy to operate, high reliability, long working cycle, and a wide range of operating temperatures and cooling capacity. The magnetic refrigerator fully meets these conditions, such as deuterium pellets for cryolaser targeting, deuterium and tritium pellets for nuclear fusion, cooling of infrared elements, cooling of magnetic window systems, cooling of superconducting magnets for minesweepers, etc.

Aside from redundant features such as touchscreens and built-in cameras, basic refrigeration technology hasn't changed much in decades. We still have cooling through chemical refrigerants and compressors, and now European researchers have demonstrated a promising early cooling system that uses magnetic fields and deformed memory alloys for cooling. <>

Magnetic cooling systems work by utilizing the magnetocaloric effect, which is that certain materials change their temperature when exposed to a magnetic field. The technology is almost as long as traditional refrigeration, but it has never really been applied because the complexity of the equipment undermines energy efficiency, where superconducting magnets are often used, which require their own cooling systems.

To solve this problem, researchers at the Technical University of Darmstadt and Germany (HZDR) used a unique combination of magnets and special alloys. Magnets contain the rare earth metal neodymium, as well as iron and boron. The alloy is a mixture of nickel, manganese and indium.

This combination is key to making the system practical. These magnets are the strongest permanent magnets currently known, capable of producing a magnetic field 40,000 times stronger than that of Earth. At the same time, this particular alloy will cool when exposed to a magnetic field, and in addition, it will return to its original shape after deformation.

Using this combination, the project's researchers developed a six-step refrigeration cycle. First, the cooling element (alloy) is exposed to a magnetic field, which is enough for only one millisecond to magnetize and cool. The alloy is then removed from the magnetic field and any desired substances are cooled.

As the alloy warms up, it will remain magnetized. Next, the alloy is compressed by the rollers, which makes the alloy denser, loses its magnetic properties and rises in temperature, and when the drum is removed, the alloy returns to its original shape when it returns to its normal temperature, ready for the cycle to start again. <>

The project is primarily a feasibility study to illustrate how SMAs can help reduce the number of permanent magnets required for such devices. The team said these magnets were the most expensive part. "We've shown that SMAs are well suited for cooling cycles," says Oliver, the study's author.

We need much less neodymium magnets, but still produce a stronger magnetic field and a correspondingly greater cooling effect. The team plans to build a demonstration unit by 2022 to better understand how the system cools items and how energy-efficient it can be.

Principle of Magnetic RefrigerationMagnetic refrigeration is a new technology that uses the magnetocaloric effect of magnetic materials to achieve refrigeration.

Compared with the traditional vapor compression refrigeration technology, the room temperature magnetic refrigeration technology is a solid-state refrigeration method based on the physical properties of the material (magnetocaloric effect), using water and other environmentally friendly media as the heat transfer fluid, with zero GWP (global warming potential), zero ODP (ozone depletion potential), intrinsic high efficiency, low noise and low vibration, etc., and is expected to become one of the refrigeration technologies with important application prospects.

Magnetic refrigeration is a new technology that uses the magnetocaloric effect of magnetic materials to achieve refrigeration, and the so-called magnetocaloric effect refers to the change of the orderly arrangement of magnetic moments of magnetic materials when the applied magnetic field changes, that is, the magnetic entropy changes, resulting in the phenomenon of heat absorption and release of the material itself.

In the absence of an external magnetic field, the direction of the magnetic moment in the magnetic material is chaotic, which is manifested by the large magnetic entropy of the material. When there is an applied magnetic field, the orientation of the magnetic moment in the material gradually tends to be the same, which is manifested by the small magnetic entropy of the material. The basic principle of magnetic refrigeration, in the process of excitation, the magnetic moment of the magnetic material changes from disorder to order along the direction of the magnetic field, and the magnetic entropy decreases.

In the process of demagnetization, the magnetic moment of the magnetic material changes from ordered to disordered along the direction of the magnetic field, and the magnetic entropy increases. Secondly, under adiabatic conditions, there is no heat exchange between the magnetic working fluid and the outside world, and in the allergy range of excitation and demagnetization, the magnetic field does work on the material, so that the internal energy of the material changes, so that the temperature of the material itself changes.

Magnetic refrigeration is a new technology that uses the magnetocaloric effect of magnetic materials to achieve refrigeration, and the so-called magnetocaloric effect refers to the change of the orderly arrangement of magnetic moments of magnetic materials when the applied magnetic field changes, that is, the magnetic entropy changes, resulting in the phenomenon of heat absorption and heat release of the material itself.

In the absence of an external magnetic field, the direction of the magnetic moment in the magnetic material is chaotic, which is manifested by the large magnetic entropy of the material. When there is an applied magnetic field, the orientation of the magnetic moment in the material gradually tends to be the same, which is manifested by the small magnetic entropy of the material.

The basic principle of magnetic refrigeration is shown in the figure, in the process of excitation, the magnetic moment of the magnetic material changes from disorder to order along the direction of the magnetic field, and the magnetic entropy decreases. In the process of demagnetization, the magnetic moment of the magnetic material changes from ordered to disordered along the direction of the magnetic field, the magnetic entropy increases, and the magnetic working fluid absorbs heat from the outside.

Secondly, under adiabatic conditions, there is no heat exchange between the magnetic working fluid and the outside world, and in the process of excitation and demagnetization, the magnetic field does work on the material, so that the internal energy of the material changes, so that the temperature of the material itself changes.