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Magnetic Refrigeration

Presented By:

Manu E NampoothiriM E

7

IntroductionIntroductionMagnetic refrigeration is the response of

a material to a changing magnetic field. It does not require any compressor or

liquid refrigerants.Low temperature refrigeration (Less than 1

Kelvin).

Low operating and maintenance cost.Solid refrigerant is used.COP can be up to 15. Works on Magneto-Caloric Effect (MCE).

ConceptConceptMagneto-Caloric Effect (MCE)

When a magnetic field is applied, the unpaired spins get aligned parallel to the magnetic field.

This lowers the entropy.

To compensate for entropy reduction, the atoms starts vibrating.

This increases the temperature.

Magneto-Caloric Effect (MCE)

As the field is removed, the pairs will return to high entropy state.

For having high entropy they absorb heat from surroundings.

Thus cooling effect is obtained.

Magneto-Caloric Effect

Materials UsedMaterials Used

Magneto Caloric materials are used.

Usually the materials in the Lanthanide series of periodic table are used.

Material is used as alloy with other elements such as Silicon.(Si), Germanium.(Ge), Iron.(Fe) etc .

Commonly used materials for preparation of the Refrigerants are Lanthanide.(La) and Gadolinium.(Gd).

PERIODIC TABLEPERIODIC TABLE

Compounds : Gd5(SixGe1 − x)4,

La(FexSi1 − x)13Hx

Increase in Magneto-caloric Effect of Gadolinium as Magnetic Field

increases by 1 Tesla

ThermodynamicsThermodynamics

1. Adiabatic Magnetization (+H)

2. Isomagnetic Enthalpy Transfer (-Q)

3. Adiabatic Demagnetization (H=0)

4. Isomagnetic Entropy Transfer (+Q)

ThermodynamicsThermodynamics

As it utilizes the Adiabatic

Demagnetization for the refrigeration effect, It is

commonly known as Adiabatic

Demagnetization Refrigerator.

WorkingWorking

Rotary Magnetic Refrigerator(Concept)

Other concept of Rotary Magnetic Refrigerator

Prototype of a Prototype of a Magnetic Magnetic

RefrigeratorRefrigerator

ApplicationsApplications

1. Cryogenic coolers use magnetic refrigeration technique.

2. Superconductive materials are cooled to their superconducting temperature by using magnetic refrigerators.

3. It may substitute for the home use refrigerator.

AdvantagesAdvantages

Less operating and maintenance cost

High value of COP about 3-6. High efficiency at large magnetic

fields (50%-60% at 0-5 Tesla). No use of inefficient compressors. No Ozone Layer Depleting

refrigerants. Solid refrigerant is used.

DisadvantagesDisadvantages

Use of high magnetic fields makes it unsuitable for home use.

Refrigerant is less durable. Cost of Refrigerant is high (eg:

Gd).

ConclusionConclusion

It is an environmental friendly refrigeration technique, and requires less power and money for its operation. It can be used in many fields including cryogenics, superconductivity and much more. In a near future magnetic refrigerators may come to cool our home.

Thank You !