Fraunhofer Institute for Physical Measurement Techniques IPM
Based on the principle of a thermal diode, the heat is »pushed forward« in only one direction. The heat generated in the magnetic field causes liquid in the magnetocaloric material to evaporate (1). The pressure in the segment increases. The pressure relief valve opens so that vapor enters the neighboring element (2). After switching off the magnet, the magnetocaloric material cools down to below the initial temperature (3). The vapor pressure drops, resulting in a negative pressure compared to the preceding segment. Gaseous fluid flows in, and heat is absorbed from the preceding segment (4).
The magnetocaloric effect can be used to develop highly energy-efficient cooling systems that require no harmful refrigerants at all. They are based on so-called magnetocaloric materials.
How does a magnetocaloric heat pump work?
Magnetocaloric materials are magnetizable materials that heat up when exposed to a magnetic field and cool down once the field is removed. This is how a cooling cycle can be realized: the heated magnetocaloric material is connected to a heat sink so that heat can be dissipated. When the magnetic field is removed, the material cools down and is at a lower temperature than at the beginning of the cycle. The magnetocaloric material is now connected to the area that is to be cooled, so now it can absorb heat. This effect is reversible to a very high degree, which offers the potential to realize highly energy-efficient cooling systems and heat pumps using magnetocaloric materials.
Patented cooling concept
Fraunhofer IPM develops magnetocaloric cooling systems and heat pumps using a patented system concept: a fluid transfers heat by evaporation and condensation from the area to be cooled to the magnetocaloric material. This allows cooling power densities to be achieved that are an order of magnitude better than alternative system approaches. In future, this system concept can be used to realize cost-effective systems.
In particular, Fraunhofer IPM is working on:
- Development and construction of measurement setups for the characterization of magnetocaloric materials
- Simulation, configuration and construction of magnet systems
- Construction and characterization of magnetocaloric systems
- Simulation of magnetocaloric materials and systems
