The magnetic refrigeration at room temperature is an emerging technology that has attracted the interest of researchers around the world (Bouchekara, 2008). Such a technology applies the magnetocaloric effect which was first discovered by Warburg (Bohigas, 2000; Zimm, 2007).

1. Project Guide:
Prof. Ganesh
Assistant Professor
Dept. of Mechanical Engg.
GECBH
Project Members:
Akhil S (10)
Akhil.R (12)
Nidheeesh T T (4)

2.  To develop more efficient and cost-effective small-scale H2 liquefiers as
an alternative to vapour-compression cycles using Magnetic
refrigeration (adiabatic magnetization)
 To understand the Principle and mechanism for generating cooling
effect using the magnet.

3. Magnetic refrigeration is a cooling technology based on the magneto caloric effect.
This technique can be used to attain extremely low temperatures (well below 1
Kelvin), as well as the ranges used in common refrigerators, depending on the design
of the system.
It is a physical process that exploits the magnetic properties of certain solid materials
to produce refrigeration.
The refrigerant is often a paramagnetic salt, such as cerium magnesium nitrate.
It gives cooling nearest to absolute zero than any other method hence it made
liquidification of gases easier.
At the same time it does not emit any CFC or HCFC compounds hence it never
affects our environment specially OZONE layer.

4. Magneto caloric effect was discovered in pure iron in 1881 by E. Warburg.
DeDebye (1926) & Giauque (1927) proposed a improved technique of cooling
via adiabatic demagnetization independently.
The cooling technology was first demonstrated experimentally in 1933 by
chemist Nobel Laureate William F.Giauque & his colleague Dr.D.P. MacDougall
for cryogenic purposes.
In 1997,Prof. Karl A. Gscheidner, Jr. by the lowa State University at Ames
Laboratory demonstrated the first near room temperature proof of concept
magnetic refrigerator.

5. MCE is a magneto-thermodynamic phenomenon in which a reversible change
in temperature of a suitable material is caused by exposing the material to
changing magnetic field.
All magnets bears a property called Currie effect i.e. If a temperature of
magnet is increased from lower to higher range at certain temperature
magnet looses the magnetic field.
Currie temperature depends on individual property of each material.
As Energy input to the magnet is increased the orientation of the magnetic
dipoles in a magnet starts loosing orientation and vice-versa. At curie
temperature as magnet looses energy to the media it regains the property.

9. • Process is similar to gas
compression and expansion
cycle as used in regular
refrigeration cycle
• Steps of thermodynamic Cycle :->
 Adiabatic Magnetization
 Isomagnetic Enthalpy Transfer
Adiabatic demagnetization
Isomagnetic Entropic Transfer

10. Substance placed in insulated environment
Magnetic field +H increased
This causes the magnetic dipoles of the atoms to align
The net result is that total Entropy of the item is not reduced and
item heats up (T + ΔTad )

11. Added heat removed by a fluid like water or helium (-Q)
Magnetic Field held constant to prevent the dipoles from reabsorbing the
heat.
After a sufficient cooling Magnetocalric material and coolant are
separated(H=0)

12. Substance returned to another adiabatic(insulated) condition
Entropy remains constant
Magnetic field is decreased
Thermal Energy causes the Magnetic moments to overcome the
field and sample cools(adiabatic temperature change)
Energy transfers from thermal entropy to magnetic entropy(disorder
of the magnetic dipoles)

13.  Material is placed in thermal contact with the Environment being
refrigerated.
Magnetic field held constant to prevent material from heating back up.
Because the working material is cooler than the refrigerated environment,
heat energy migrates into the working material (+Q)
Once the refrigerant and refrigerated environment are in thermal
equilibrium, the cycle continuous.

15. Components required for
construction :-
 Magnets
 Hot Heat exchanger
 Cold Heat Exchanger
 Drive
 Magneto caloric wheel

16.  Magnetic Materials
 Regenerators
Super Conducting Magnets
Active Magnetic Regenerators

18.  MCE is an intrinsic property of a magnetic solid
 Ease of application and removal of magnetic effect is most desired
property of material
Alloys of gadolinium produce 3 to 4 K per tesla of change in magnetic field
are used for magnetic refrigeration or power generation purposes
ferrimagnets, antiferromagnets and spin glass systems are not suitable for
this application.
Gd5(SixGe1 − x)4, La(FexSi1 − x)13Hx and MnFeP1 − xAsx alloys are some of the
most promising substitutes for Gadolinium and its alloys

19. Magnetic refrigeration requires excellent heat transfer to and from the
solid magnetic material. Efficient heat transfer requires the large surface
areas offered by porous materials. When these porous solids are used in
refrigerators, they are referred to as “Regenerators”
 Typical regenerator
geometries include:
• Tubes
• Perforated plates
• Wire screens
• Particle beds

20. Most practical magnetic refrigerators
are based on superconducting
magnets operating at cryogenic
temperatures (i.e., at -269 C or 4 K)
These devices are electromagnets
that conduct electricity with
essentially no resistive losses.
The superconducting wire most
commonly used is made of a
Niobium-Titanium alloy

21. A regenerator that undergoes cyclic heat transfer operations and the
magneto caloric effect is called an Active Magnetic Regenerator.
An AMR should be designed to possess the following attributes:-
 High heat transfer rate
 High magneto caloric effect
 Sufficient structural integrity
 Low thermal conduction in the direction of fluid flow
 Affordable materials
 Ease of manufacture

22. TECHNICAL
• High Efficiency
• Reduced Operating Cost
• Compactness
• Reliability
SOCIO-ECONOMIC
• Competition in Global Market
• Low Capital Cost
• Key Factor to new
technologies

23. At the present stage of the development of magnetic refrigerators with
permanent magnets, hardly any freezing applications are feasible.
Some of the future applications are:-
Magnetic household refrigeration appliances
Magnetic cooling and air conditioning in buildings and houses
Central cooling system
Refrigeration in medicine
Cooling in food industry and storage
Cooling in transportation
Cooling of electronic equipments

24.  Purchase cost may be high, but running costs are 20% less than the
conventional chillers.
 Thus life cycle cost is much less.
 Ozone depleting refrigerants are avoided in this system, hence it more
eco-friendly.
 Energy conservation and reducing the energy costs are added
advantages.
 The efficiency of magnetic refrigeration is 60% to 70% as compared to
Carnot cycle.
 Magnetic refrigeration is totally maintenance free & mechanically simple
in construction.

25. As every coin has 2 sides, this technique also posses some
drawbacks to be worked on
 The initial investment is more as compared with conventional
refrigeration.
 The magneto caloric materials are rare earth materials hence their
availability also adds up an disadvantage in MAGNETIC REFRIGERATION.

26.  It is a technology that has proven to be environmentally safe. Computer
models have shown 25% efficiency improvement over vapor compression
Systems.
 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.