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MAGNETIC REFRIGERATION

Presented By,Ananthu Sivan

Feby Philip AbrahamS4, Dept. of Mechanical Engineering,

Mohandas College of Engineering & Technology, Anad, Trivandrum

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INTRODUCTIONWHAT IS MAGNETIC REFRIGERATION??MAGNETOCALORIC EFFECTHOW DOES AN ADR WORK??MAGNETIC REFRIGERATION CYCLECONSTRUCTIONAL COMPONENTSWORKING MATERIALSGMCE MATERIALSALTERNATIVE TECHNIQUESCOMMERCIAL DEVELOPMENTCONCLUSION

CONTENTS

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Refrigeration is the process of removing heat from an enclosed space or from a substance and moving it to a place where it is unobjectionable

The primary objective of refrigeration is lowering the temperature of the enclosed space or substance and then maintaining that lower temperature.

INTRODUCTION

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Magnetic refrigeration is a cooling technology based on the magneto caloric effect.

It is used to attain temperature well below 1 Kelvin.

Magnetic refrigeration currently finds application in cryogenics.

What is Magnetic Refrigeration??

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Some magnetic materials heat up when they are placed in a magnetic field and cool down when they are removed from a magnetic field. This is known as the magnetocaloric effect.

The effect was discovered in pure iron in 1880 by German physicist Emil Warburg

In 1997, the first near room temperature proof of concept magnetic refrigerator was demonstrated by Prof. Karl A. Gschneidner

Magneto-caloric Effect

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Illustration of the

Magnetocaloric effect

Gadolinium alloy

heats up inside

the magnetic field

and loses

thermal energy

by irradiation, so

that it exits the

field cooler than

when it entered.

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Magnetic Refrigeration Cycle

1. Adiabatic magnetization

2. Isomagnetic enthalpic transfer

3. Adiabatic demagnetization

4. Isomagnetic entropic transfer

How Does an ADR Work??

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1. Working material is placed in an insulated environment

2. Increasing magnetic field is applied

3. Magnetic dipoles of the atoms of the material align

4. Decreases material’s magnetic entropy and heat capacity

5. Total entropy of the material remains conserved (Laws of Thermodynamics)

6. Results in heating up of the material (T+ΔTad)

Adiabatic Magnetization

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1. Heat generated in the previous process is removed by a fluid (He or H2O)

2. Magnetic field is held constant

3. After being sufficiently cooled, the magnetocaloric material and coolant are separated

Isomagnetic Enthalpic Transfer

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1. The substance is brought to another insulated environment

2. Magnetic field is decreased

3. Magnetic entropy increases, thermal entropy decreases

4. Material cools down

Adiabatic Demagnetization

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1. Magnetic field is held constant

2. Environment to be cooled is brought in contact with the magnetocaloric material

3. Heat transfers from space to be cooled to the magnetocaloric material

Isomagnetic Entropic Transfer

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Magnetic Refrigeration Cycle

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Magnets

Hot Heat Exchanger

Cold Heat Exchanger

Drive

Magnetocaloric Wheel

Constructional Components

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Magnets provide the magnetic field to the material so that they can lose or gain the heat to the surrounding and from the space to be cooled respectively

Magnets

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The hot heat exchanger absorbs the heat from the material used and gives off to the surrounding. It increases the efficiency of heat transfer

Hot Heat Exchanger

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The cold heat exchanger absorbs the heat from the space to be cooled and gives it to the magnetic material. It helps to make the absorption of heat efficient.

Cold Heat Exchanger

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Drive provides the right rotation to the Magneto caloric wheel. Due to this, heat flow in the desired direction is achieved.

Drive

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It forms the base structure of the whole device. It is the fundamental element in the whole system. It joins the two magnets and ensures proper operability.

Magnetocaloric Wheel

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An artist’s rendition of a Rotary Magnetic Refrigerator

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Proposed representation of a commercial system

This is the picture

of a proposed

commercial

magnetic

refrigeration

system which is

being developed

by Camfridge and

Whirlpool. It is

planned to be

launched in the

UK in the year

2012.

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Magneto caloric effect is characteristic of the material

The ability of a material to produce a change in its temperature per Tesla of change in magnetic field, is the deciding factor.

Alloys of gadolinium can be used for magnetic refrigeration.

Paramagnetic Salts like Cerium Magnesium Nitrate

Working Materials

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Giant Magnetocaloric Effect Materials

Exhibits GIANT change in entropy

Most promising material with respect to magnetic refrigeration, at room temperature

Examples - Gd5(SixGe1−x)4

La(FexSi1−x)13Hx

MnFeP1−xAsx

GMCE Materials

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Nuclear Demagnetization Refrigeration

Working Principle remains the same

Cooling power arises from the magnetic dipoles of the nuclei of the refrigerant atoms, rather than their electron configurations.

They have much smaller magnetic dipoles

Less prone to self alignment

Lower intrinsic minimum fields

Temperatures of up to 1 µK or less, achievable

Alternative Techniques

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Pros :1.Viable in various industries and research facilities

2.Environmentally friendly, as it doesn’t require any polluting gases

3.Comparatively lower power consumption, research shows them to be 50% more efficient than conventional cooling systems

4.In commercial refrigeration a key cost is maintenance caused by leakage of refrigerant. By eliminating gases this maintenance cost will be removed.

5.In domestic refrigeration low noise is valuable; elimination of gas compression reduces noise.

Commercial Development

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Cons:1.Various technical difficulties remain at large

2.Availability of good working material is a concern

3.Superconducting magnets are required to produce sufficient field

4.Magnetic hysteresis losses are considerable for certain materials

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Gschneidner stated in 1999 that: “Large-scale applications using magnetic refrigeration, such as commercial air conditioning and supermarket refrigeration systems, could be available within 5–10 years. Within 10–15 years, the technology could be available in home refrigerators and air conditioners.”

Conclusion

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http://en.wikipedia.org/wiki/Magnetic_refrigeration

http://cryo.gsfc.nasa.gov/ADR/ADR_primer/ADR_primer.html

http://imagine.gsfc.nasa.gov/docs/teachers/lessons/xray_spectra/background-adr.html

http://www.physlink.com/Education/AskExperts/ae488.cfm

http://www.ameslab.gov/content/magnetocaloric-effect-magnetic-refrigeration-and-ductile-intermetallic-compounds

http:/newenergyandfuel/com/2009/05/25/progress-update-on-magnetic-refrigeration/magnetic-refrigeration-process-graph/

http://www.camfridge.com/Pages/story.html

References

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Thank You