27-12-2012, 06:29 PM
MAGNETIC REFRIGERATION
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INTRODUCTION
Refrigeration is the process of removing heat from an enclosed space or from a substance and moving it to a place where it is unobjectionable
The primary objective of refrigeration is lowering the temperature of the enclosed space or substance and then maintaining that lower temperature.
What is Magnetic Refrigeration?
Magnetic refrigeration is a cooling technology based on the magneto caloric effect.
It is used to attain temperature well below 1 Kelvin.
Magnetic refrigeration currently finds application in cryogenics.
Magneto-caloric Effect
Some magnetic materials heat up when they are placed in a magnetic field and cool down when they are removed from a magnetic field. This is known as the magnetocaloric effect.
The effect was discovered in pure iron in 1880 by German physicist Emil Warburg
In 1997, the first near room temperature proof of concept magnetic refrigerator was demonstrated by Prof. Karl A. Gschneidner
How Does an ADR Work?
Magnetic Refrigeration Cycle
Adiabatic magnetization
Isomagnetic enthalpic transfer
Adiabatic demagnetization
Isomagnetic entropic transfer
Adiabatic Magnetization
Working material is placed in an insulated environment
Increasing magnetic field is applied
Magnetic dipoles of the atoms of the material align
Decreases material’s magnetic entropy and heat capacity
Total entropy of the material remains conserved (Laws of Thermodynamics)
Results in heating up of the material (T+ΔTad)
Conclusion
“Large-scale applications using magnetic refrigeration, such as commercial air conditioning and supermarket refrigeration systems, could be available within 5–10 years. Within 10–15 years, the technology could be available in home refrigerators and air conditioners.”