Presented By, Ananthu Sivan Feby Philip Abraham S4, Dept. of Mechanical Engineering, Mohandas College of Engineering & Technology, Anad, Trivandrum1

y INTRODUCTION y WHAT IS MAGNETIC REFRIGERATION?? y MAGNETOCALORIC EFFECT y HOW DOES AN ADR WORK?? y MAGNETIC REFRIGERATION CYCLE y CONSTRUCTIONAL COMPONENTS y WORKING MATERIALS y GMCE MATERIALS y ALTERNATIVE TECHNIQUES y COMMERCIAL DEVELOPMENT y CONCLUSION2

y Refrigeration is the process of removing heat from an

enclosed space or from a substance and moving it to a place where it is unobjectionabley The primary objective of refrigeration is lowering the

temperature of the enclosed space or substance and then maintaining that lower temperature.

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y Magnetic refrigeration is a cooling technology based

on the magneto caloric effect.y It is used to attain temperature well below 1 Kelvin. y Magnetic refrigeration currently finds application in

cryogenics.

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y 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.y The effect was discovered in pure iron in 1880 by

German physicist Emil Warburg

y In 1997, the first near room temperature proof of

concept magnetic refrigerator was demonstrated by Prof. Karl A. Gschneidner5

Illustration of the Magnetocaloric effectGadolinium 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 Cycle1. 2. 3. 4.

Adiabatic magnetization Isomagnetic enthalpic transfer Adiabatic demagnetization Isomagnetic entropic transfer7

1. 2. 3. 4. 5.

Working material is placed in an insulated environment Increasing magnetic field is applied Magnetic dipoles of the atoms of the material align Decreases material s magnetic entropy and heat capacity Total entropy of the material remains conserved (Laws of Thermodynamics) Results in heating up of the material (T+ Tad)8

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1.

Heat generated in the previous process is removed by a fluid (He or H2O) Magnetic field is held constant After being sufficiently cooled, the magnetocaloric material and coolant are separated

2. 3.

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1.

The substance is brought to another insulated environment Magnetic field is decreased Magnetic entropy increases, thermal entropy decreases Material cools down10

2. 3.

4.

1. 2.

Magnetic field is held constant Environment to be cooled is brought in contact with the magnetocaloric material Heat transfers from space to be cooled to the magnetocaloric material

3.

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y Magnets y Hot Heat Exchanger y Cold Heat Exchanger y Drive y Magnetocaloric Wheel13

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

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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

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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.

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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.

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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.

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An artist s rendition of a Rotary Magnetic Refrigerator19

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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y Magneto caloric effect is characteristic of the material y The ability of a material to produce a change in its

temperature per Tesla of change in magnetic field, is the deciding factor.y Alloys of gadolinium can be used for magnetic

refrigeration.y Paramagnetic Salts like Cerium Magnesium Nitrate21

y Giant Magnetocaloric Effect Materials y Exhibits GIANT change in entropy y Most promising material with respect to magnetic

refrigeration, at room temperaturey Examples -

Gd5(SixGe1 x)4 La(FexSi1 x)13Hx MnFeP1 xAsx22

y 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 K or less, achievable23

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Pros : 1. Viable in various industries and research facilities2. 3.

Environmentally friendly, as it doesn t require any polluting gases Comparatively lower power consumption, research shows them to be 50% more efficient than conventional cooling systems leakage of refrigerant. By eliminating gases this maintenance cost will be removed. In domestic refrigeration low noise is valuable; elimination of gas compression reduces noise.

4. In commercial refrigeration a key cost is maintenance caused by

5.

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y 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 field4. 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.

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y http://en.wikipedia.org/wiki/Magnetic_refrigeration y http://cryo.gsfc.nasa.gov/ADR/ADR_primer/ADR_primer.html y http://imagine.gsfc.nasa.gov/docs/teachers/lessons/xray_spectra/background-

adr.html

y http://www.physlink.com/Education/AskExperts/ae488.cfm y http://www.ameslab.gov/content/magnetocaloric-effect-magnetic-

refrigeration-and-ductile-intermetallic-compounds

y http:/newenergyandfuel/com/2009/05/25/progress-update-on-magnetic-

refrigeration/magnetic-refrigeration-process-graph/

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

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