Magnet vs. freon

A fundamentally new refrigerator has been developed by researchers from the National University of Science and Technology MISIS and Tver State University – it is based on a solid-state magnetic system that gives 30-40% odds to the gas-compressor mechanism of a conventional refrigerator in terms of energy efficiency.

One of the main objects of our apartments – the refrigerator – consumes up to 20-40% of all electricity. On a global scale, technology to create cold, meaning industrial and domestic refrigerators, home air conditioners and automotive air conditioners is a very expensive pleasure. According to expert estimates, all these devices spend up to 10% of the world’s electricity as a whole.

The scientific team of physicists and engineers of the NUST MISIS Department for Functional Nanosystems & High-Temperature Materials and Tver State University solved the problem of efficient cold generation by proposing a new cooling system – a magnetic one. In a conventional refrigerator, cooling occurs due to the sudden evaporation of freon (or other refrigerants), which passes into a gaseous state. A different principle works in the invention of young Russian scientists – the so-called magnetocaloric effect. In simple terms, it means the change of the magnetic material temperature during its magnetization or demagnetization.

Technically, it looks quite simple – the metal bar is introduced into the magnetic field and heats up, and when taken out of the field – cools down. However, this must be done quickly and cyclically so that the temperature difference was maintained. A team of scientists designed a device prototype, which is small in size, but capable of cooling an entire refrigerator.

“Since the density of the metal alloy is much greater than that of the gas, the stored entropy value (measure of disorder), and therefore its cooling capacity, is greater,” explains one of the project developers, senior researcher at the NUST MISIS Department for Functional Nanosystems & High Temperature Materials Dmitry Karpenkov, “this explains the 30-40% higher energy efficiency of new solid-state devices by compared to gas-compression analogues.

While small in sizes these devices can provide the maximum difference between the temperatures of hot and cold heat exchangers – 9 degrees Celsius. The main difference of the developed prototype from all predecessors is that the working fluids simultaneously perform as the refrigerant and the pressure pump. This technical solution excludes the pumps, which are an additional thermal load for the refrigerator, from the scheme.”

The second unique technical solution was to distinguish the flows of heat transfer fluid from the cold and hot heat exchangers, while allowing the working fluid, being in a magnetized (demagnetized) state, to sequentially move from one flow to another.

“The results of our tests show that the use of cascade magnetic cooling cycles leads to an 80% increase in the cooling range,” Dmitry Karpenkov added.

During the experiment to assess the effectiveness of the prototype, the researchers have found that the maximum amount of heat that a heat pump can take during a cycle is about 405 J, which corresponds to a maximum cooling power of 45 watts.

Currently, the research team has assembled a laboratory prototype of the cooling mechanism and is conducting a series of laboratory tests.

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