What Is Magnetic refrigeration he magnetocaloric effect (MCE, from magnet and calorie) is a magneto-thermodynamic phenomenon in which a temperature change of a suitable material is caused by exposing the material to a changing magnetic field. This is also known by low temperature physicists as adiabatic demagnetization. In that part of the refrigeration process, a decrease in the strength of an externally applied magnetic field allows the magnetic domains of a magnetocaloric material to become disoriented from the magnetic field by the agitating action of the thermal energy (phonons) present in the material. If the material is isolated so that no energy is allowed to (re)migrate into the material during this time, (i.e., an adiabatic process) the temperature drops as the domains absorb the thermal energy to perform their reorientation. The randomization of the domains occurs in a similar fashion to the randomization at the curie temperature of a ferromagnetic material, except that magnetic dipoles overcome a decreasing external magnetic field while energy remains constant, instead of magnetic domains being disrupted from internal ferromagnetism as energy is added. One of the most notable examples of the magnetocaloric effect is in the chemical element gadolinium and some of its alloys. Gadolinium's temperature increases when it enters certain magnetic fields. When it leaves the magnetic field, the temperature drops. The effect is considerably stronger for the gadolinium alloy (Gd 5Si 2Ge 2).[8] Praseodymium alloyed with nickel (PrNi 5) has such a strong magnetocaloric effect that it has allowed scientists to approach to within one milliKelvin, one thousandth of a degree of absolute zero.[9]

2. MAGNETIC
REFRIGERATION
Group Members
Ehtisham Ahsan BSME 01153113
Hafiz Usama Akhtar BSME 01153120
Zain ul Abideen BSME 01153130
Asjad Ahmed Khan BSME 01153143
Hafiz Shahreyar Raza BSME 01153115

3. EHTISHAM AHSAN
BSME 01153113

4. INTRODUCTION
 A compressor is a mechanical device like a pump
that is used in various different applications.
 Basically it is a refrigerant gas pump in which the
evaporator supplies gaseous refrigerant at a low
pressure and increases it to a greater pressure.
Upon being compressed, the temperature and
pressure of the vapor are increased.
 The gaseous refrigerant is delivered to the
condenser at a pressure at which condensation
occurs at an appropriate temperature.
COMPRESSOR

5. TYPES OF COMPRESSOR
There are basically 5 types of air conditioner
compressor that are commonly used in the HVAC
industry:
Reciprocating
Scroll
Screw
Rotary
Centrifugal

6. MAGNETIC REFRIGERATION
 It 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.

7. 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 liquification
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.

8. HISTORY
 Magneto caloric effect was discovered in pure iron in 1881 by E.
Warburg.
 Debye (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.

9. MAGNETIC CALORIC EFFECT
 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.

10.  Currie temperature Depends on individual property of
each material.
 As Energy input to the magnet is increased the
orientation of them magnetic dipoles in a magnet
starts loosing orientation. And vice a versa at curie
temperature as magnet looses energy to the media it
regains the property.

11. Zain ul Abideen
BSME 01153130

12. WORKING PRINCIPLE

13. THERMODYNAMIC CYCLE

14. VIDEO

15. DETAILS OF THERMODYNAMIC
CYCLE
 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

16. ADIABETIC MAGNETIZATION
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 ).

17. ISOMAGNETIC ENTHALPY
TRANSFER
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 Magneto caloric material
and coolant are separated(H=0).

18. Hafiz Usama Akhtar
BSME 01153120

19. ADIABETIC DEMAGNETIZATION
 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)

20. ISOMAGNETIC ENTROPIC TRANSFER
 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.

21. Construction
 Components required for construction :-
 Magnets
 Hot Heat exchanger
 Cold Heat Exchanger
 Drive
 Magneto caloric wheel

22. WORKING MATERIALS
 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.
 Ferro magnets, 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

24. Asjad Ahmed KhanBSME 01153143

25. REGENERATORS
 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”

26. Typical regenerator
geometries include:
Tubes
Perforated plates
Wire screens
Particle beds

27. SUPER CONDUCTING MAGNETS
 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

28. SUPER CONDUCTING MAGNETS

29. AMR
 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

30. BENEFITS
TECHNICAL
High Efficiency
Reduced Operating
Cost
Compactness
Reliability
SOCIO-ECONOMIC
Competition in
Global Market
Low Capital Cost
Key Factor to new
technologies

31. Hafiz Shahreyar RazaBSME 01153115

32. FUTURE APPLICATIONS
Some of the future applications are:-
Magnetic household refrigeration appliances
Magnetic cooling and air conditioning in buildings and houses
Central in spacecraft and laboratory applications
Refrigeration in medicine
Cooling in food industry and storage
Cooling in transportation
Cooling of electronic equipments

33. ADVANTAGES
 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.

34. DISADVANTAGES
 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.

35. CONCLUSION
 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.