Transcript MAGNETIC REFRIGERATION (2)

INTRODUCTION
 Magnetic refrigeration is a cooling technology based
on the magneto caloric effect.
 Invented by Emil Warburg in 1880
 Used to attain cryogenic temperatures well below 1o K
with the help of magnetic fields
PRINCIPLE OF MAGNETIC
REFRIGERATION
 Magneto caloric effect is the basic principle on which
the cooling is achieved.
 Magneto caloric effect is a magneto-thermodynamic
phenomenon in which a reversible change in
temperature of a suitable material is caused by
exposing the material to a changing magnetic field.
 This is called adiabatic demagnetisation .
THERMODYNAMIC CYCLE
STEPS OF THERMODYNAMIC CYCLE
 Adiabatic magnetisation
 Isomagnetic enthalpic transfer
 Adiabatic demagnetization
 Isomagnetic entropic transfer
REQUIREMENTS FOR PRACTICAL
APPLICATIONS
 Magnetic Materials
 Regenerators
 Super Conducting Magnets
 Active Magnetic Regenerators(AMR’s)
MAGNETIC MATERIALS
 Magnetocaloric effect is an intrinsic property of a
substance
 Gadolinium and its alloys are the best materials
available for magnetic refrigeration
 They can reach ultra low temperatures
REGENERATORS
 Efficient heat transfer requires large surface areas
offered by porous materials
 When these porous materials are used in refrigerators
they are referred to as regenerators
SUPER CONDUCTING MAGNETS
 The magnetic field is created by superconducting
magnets
 Most practical magnetic refrigerators are based on
super conducting magnets operating at cryogenic
temperatures
 Commonly used is made of a Niobium-Titanium alloy
ACTIVE MAGNETIC REGENERATORS
 A regenerator that undergoes cyclic heat transfer
operations and magneto caloric effect is called Active
Magnetic Regenerator
 It should be designed to possess:
high heat transfer rate
high magneto calorific effect
affordable materials
ease of manufacture
APPLICATIONS
 Liquefaction purposes in the case of hydrogen,nitrogen
and helium
 Also focuses on many future applications like magnetic
household refrigeration,cooling in
transportation,cooling electronic circuits etc.
MERITS
 High efficiency
 Reduced operating cost
 Reliability
CONCLUSIONS
 Magnetic refrigeration is a technology that has proven to
be environmentally safe
 In order to make the Magnetic Refrigerator commercially
viable, scientists need to know how to achieve larger
temperature swings and also permanent magnets which
can produce strong magnetic fields of order 10 tesla
 There are still some thermal and magnetic hysteresis
problems to be solved for the materials that exhibit the
MCE to become really useful
THANK YOU