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ICE - Magnetic cooling
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Magnetic cooling

The fundamental principle of the Magneto-Caloric Effect (MCE) was discovered by E. Warburg (1881) and further on studied by Debye (1926) and Giauque (1927). The first magnetic cooling system for a very low temperature (0.25 K) was built in 1933, leading to a Nobel Prize in physics in 1949.



Emil Gabriel Warburg


The magnetocaloric effect (MCE) results in a few Kelvin reversible temperature change within a magnetocaloric material when a magnetic field is applied. The material reaches the initial temperature once the magnetic field is removed.


The magnetocaloric effect:

  • Depends on the magnetic field intensity, on the magnetocaloric alloy and on the temperature.
  • Has a greater intensity at the Curie temperature of the material.

Permanent magnet materials will be employed as field source within the ICE project. This is usually done for systems requiring a high cooling power. In the end of the 20th century an important progress has been done in NdFeB-based permanent magnets.

 

 

The whole system has to be designed properly in order to achieve a maximal magnetic induction in the maximum volume of active MCE materials and to permit the alternate and repetitive variation of the magnetic field. With this technology, thermal COPs between 2 and 22 can be achieved, thus higher than in conventional vapour-compression chillers.

The heat transfer is also a key issue in such machines. The fluid flows back and forth between the thermal sources, passing through the magneto-caloric element:

  • The fluid generates exchanges heat with all of the components
  • The fluid alternation is synchronous with the magnetization


The machine designed for the ICE project uses an AMR (active magnetic regenerator) which is a regenerator made of magnetocaloric material exposed to a periodic intermittent magnetic field. A temperature gradient is created along the regenerator, as shown in the next IR picture of the ICE project magnetocaloric heat pump prototype.

 

IR picture of a magnetocaloric heat pump