Magnetic Refrigeration Principle
Magnetic Refrigeration: a bit of history
Some classes of materials, called Magnetocaloric Materials (MCM), heat up when immersed in a magnetic field and cool down when removed from it, almost instantaneously. The phenomenon, known as Magnetocaloric Effect (MCE), was discovered by E. Warburg in 1881.
In 1933, W. Giauque was the first to use the Magnetocaloric Effect (MCE) in a magnetocaloric system that reached a very low temperature (0.25K). W. Giauque received a Nobel Prize in 1949.
In 1997, the Ames Laboratory implemented a proof-of-principle using Gadolinium. Reacting at ambient temperature (~20°C), the use of Gadolinium was a milestone for all developments of magnetic refrigeration systems for commercial applications.
Magnetic Refrigeration: the physical principle
Magnetic refrigeration is based on the Magnetocaloric Effect (MCE). The MCE implies that the temperature of suitable materials (Magnetocaloric Materials, MCM) increases when they are exposed to a magnetic field and decreases when they are removed from it, that is, the effect is reversible and almost instantaneous.
The temperature with the strongest effect (the Curie temperature) depends on the properties of every material. The power generated by the system depends on the type of materials and their characteristics (mass and shape).
In a Magnetic Refrigeration System, a controlled magnetic field applies a series of Magnetization-Demagnetization cycles to the magneto-caloric alloys. Each of these cycles creates a temperature gradient in the material. A rapid succession of these cycles produces the final and stabilized hot and cold temperatures in the refrigerated system.
An environmentally friendly coolant fluid (glycol water) ensures the heat transfer between the cold to the hot sources. Similar to a heat pump process, Magnetic Cooling can be adapted to any kind of refrigeration system (professional fridge, display case, home appliance...).
Example of a system integration into a medical refrigerator: