SEMINAR ON

MAGNETIC REFRIGERATION

SUBMITTED BY:AKANSHA VOHRAME ROLL NO. 07

index• Magneto caloric effect• Basic concepts• Refrigeration cycle• Comparison• Requirement for practical application• Future model• Future application• Advantages• Disadvantages

MAGNETO CALORIC EFFECT

• It is a magneto-thermodynamic phenomenon in which a change in temperature of a suitable material is caused by exposing the material to a 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.

• Magnetocaloric property is an intrinsic property of material

concepts1. Entropy

Thermal entropy Magnetic entropy

2. Entropy of an isolated system remain constant

3. Thermal entropy of a system increase with temperature

4. Magnetic entropy of a system increase with decrease in magnetic field applied

Magnetic refrigeration

cycle

Adiabatic magnetization

MAGNETIC FIELDINCREASED

•MAGNETIC ENTROPY DECREASED•NET ENTROPY CONSTANT (ISOLATED SYSTEM)•THERMAL ENTROPY INCREASE•TEMPERATURE INCREASE (T + ΔTad )

ISOMAGNETIC ENTHALPY TRANSFER

MAGNETIC FIELD KEPT AS CONSTANT

HEAT REMOVED BY COOLING FLUID AS WATER AND HELIUM

ADIABATIC DEMAGNETIZATION

MAGNETIC FIELDDECREASED

•MAGNETIC ENTROPY INCREASED•NET ENTROPY CONSTANT (ISOLATED SYSTEM)•THERMAL ENTROPY DECREASE•TEMPERATURE DECREASE (T - ΔTad )

ISOMAGNETIC ENTROPY TRANSFER

MAGNETIC FIELD KEPT AS CONSTANT

The material is placed in thermal contact with the environment being refrigerated.

comparison

REQUIREMENTS FOR PRACTICAL APPLICATION

WORKING MATERIAL•Alloys of gadolinium producing 3 - 4 K per tesla [K/T] of change in a magnetic field• Giant magneto caloric effect (GMCE) materials as •Gd5(SixGe1 − x)4, La(FexSi1 − x)13Hx and MnFeP1 − xAsx

TYPES OF REGENERATOR

• Tubes• Perforated plates• Wire screens• Particle beds

Continued..SUPERCONDUCTING MAGNETS• They operate 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

Future models

FUTURE APPLICATION• 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:-

v Magnetic household refrigeration appliances

v Magnetic cooling and air conditioning in buildings and houses

v Central in spacecraft and laboratory applicatiions

v Refrigeration in medicine

v Cooling in food industry and storage

v Cooling in transportation

v Cooling of electronic equipments

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.

disadvantages

• 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

• There are still some thermal and magnetic hysteresis problems to be solved for the materials that exhibit the MCE

bibliography

• www.wikipedia.com• Well’s paper by Dr. Robert

O’Handley on Magnetic Materials Spring 2004 Department of Materials Science & Engineering (MIT)

• www.youtube.com

Thank you!