New refrigeration cycle based on magnetic materials
New refrigeration cycle based on magnetic materials
17% of the world's energy expenditure goes to domestic and industrial refrigeration. This consumption is spiking, especially in emerging countries, and it is expected that in a few years spending on refrigeration will exceed that dedicated to generating heat, mainly because of climate change. On the other hand, the current technology used in refrigeration is based on fluorocarbons, gases that cause greenhouse effect and that in the coming years should be replaced by other possibilities.
One of the options of change is the creation of refrigeration systems based on the solid state, and within it, the materials that are based on the use of magnetic fields to cool are one of the best positioned alternatives. In this line a research has been developed in the Department of Condensed Matter Physics of the UB, published in Nature Materials and led by the professors Lluís Mañosa and Antoni Planes, as well as by the doctoral student Adrià Gràcia, in collaboration with Professor Oliver Gutfleisch, from the Technical University of Darmstadt (Germany), and Dr. Tino Gottschall, from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). These researchers have designed a six-step cooling cycle based on the "magnetic memory" of certain alloys.
«Certain types of alloys, when subjected to a magnetic field, are magnetized -even when the aforementioned field is extracted- and also, in this process, the material cools,» explains Lluís Mañosa. "What we have discovered in this work," he says, "is that by applying external pressure we can reverse the effect of magnetization and return the system to its original state. This step is necessary to establish a closed cycle. "
Explanation of the cooling process. (Image: U. Barcelona)
The refrigeration cycle developed by the researchers consists of six steps. In the first, the magnetic field is applied and the material cools; in the next one, the field is extracted so that the material remains magnetized thanks to the hysteresis. In the third step, mechanical pressure is applied on the material, which allows modifying its crystalline structure and returning it to its non-magnetic state while the material is heated. The cooling effect takes place in the fourth step, when the material absorbs heat from the environment. Then - fifth step - the pressure is eliminated and the material is kept in this new state in which it has already been demagnetized. Finally, the alloy delivers heat to the environment and thus closes the cycle.
For this research, experts have used a magnetocaloric alloy of nickel, manganese and indium (Ni-Mn-In) that allows to work at room temperature. In addition, the materials that make up the alloy are easily accessible, unlike those currently used.
For technological reasons, the magnetic refrigeration cycle needs to use permanent magnets. These magnets are based on rare earths, extremely expensive minerals and that are also obtained through highly polluting processes.
"Thanks to this new step that we have included in the refrigeration cycle, the size of the magnets that are required is considerably reduced, thus making it more competitive. Currently, four times as much magnet is required for each part of refrigerant materials. The new cycle is more competitive, since it only requires half the magnet, "says Antoni Planes. "Another important point," continues the researcher, "is that this new cycle takes advantage of the phenomenon of hysteresis, which usually involves a loss of energy."
Currently, there is some consensus around the idea that this type of magnetocaloric materials can be more efficient than current systems, and that devices based on these materials could replace those of those devices that do not require large decreases of temperature, between 15 and 20 ºC, as domestic air conditioners. (Source: U. Barcelona)
.
.
SOURCE LINK ERESVIRAL.COM https://www.beviral.online
Comentarios
Publicar un comentario