1. SEMINARON MAGNETICREFRIGERATION PRESENTEDBY GANESHPRALHADBHARAMBE UNDERTHEABLEGUIDANCEOF PROF.A. M. PATIL. DEPARTMENTOFMECHANICALENGINEERING, PADMABHUSHANVASANTRAODADAPATILINSTITUTEOFTECHNOLOGY, BUDHAGAON,DIST.SANGLI.MAHARASHTRA.

2. ACKNOWLEDGEMENT

THE AUTHOR OF THIS SEMINAR IS THANKFUL TO PROF. A.M. PATIL AND PROF. DANGEFROM MECHANICAL DEPARTMENT FOR GIVING VALUABLE GUIDANCE FOR PREPARING THIS SEMINAR. THEIRINSPIRATIONS HAVE SUCCEEDED IN GIVING A FULL FORM AND SHAPE OF THIS SUBJECT IN DEPTH.

GP BHARAMBE

3. CONTENTS > Basicprinciplesofmagneticrefrigeration >Thermodynamic cycle > Materials: Working materials,Development in materials and Nano compositswhich can play important role inupgradin the efficiency of materials>Commercialaspects >Historicalbackground 4. MAGETICREFRIGERATION

AIMSOFSEMINAR :

To understand the principle and mechanism for generating

cooling effect using the magnet.

Materialsand process

Commercialaspects .

Nanotechnology

History

Practicalcases ofequipment building

5. Introduction:Principle

Magetocalorificeffectis the basicprincipleon which the coolingis achieved.

All magnetsbears a property calledCurrieeffecti.e.If a temperatureofmagnetisincreasedfrom lower to higher range atcertaintemperature magnetlooses the magnetic field.

Currietemperature.Depends on individualproperty of each material.

As Energyinput to the magnetis increased the orientation of the magetic dipoles in a maget starts loosing orientation.And vice a versaat currie temperature as maget looses energy to the media it regains the property.

6. Thermo dynamiccycle 7. DETAILSOF THE THERMODYNAMICCYCLE

PROCESSISSIMILARTOGASCOMPRESSIONAND EXPANSIONCYCLEASUSEDIN REGULARREFRIGERATIONCYCLE.

Stepsofthermodynamiccycle -

Adiabaticmagnetization

Isomagneticenthalpictransfer

Adiabaticdemagnetization

Isomagneticentropictransfer

8. Adiabaticmagnetization

Procedureto be followed :

> Substance placed in insulated environment.

> Magnetic field +Hincreased.

> Magneticdipoles of atoms to align, thereby

material decreases.

> TotalEntropy of the item is not reduced, and item heats up

9. Isomagneticenthalpictransfer

>Addedheatremovedbyfluid, gas gaseous or

liquid helium

> Magneticfieldheldconstant to prevent the dipoles

fromreabsorbing the heat.

> Aftera sufficientcoolingmagnetocaloricmaterial

andcoolant are seperated

10. AdiabaticDemagnetization

>Substancereturned to another adiabatic( insulated ) condition

>Entropyremainsconstant

>Magneticfieldis 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 )

11. Isomagneticentropictransfer

> Materialisplacedin thermal contact with the environment being refrigerated.

> Magneticfieldheldconstant to prevent from heating back up

> Because the working material is cooler than the refrigerated environment, heat energy migrates into the working material ( +Q )

***** Once the refrigerent and refrigerated environment are in thermal equillibrium, the cycle begins a new

12. Advantages of Magnetic Refrigeration

> 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 saving would lessen the strain on our household appliances

> Energy conservation and reducing the energy costs are added advantages.

13. WorkingMaterials

> Magneto caloric effect is an intrinsic porperty of magnetic solid.

> Ease of application and removal of magnetic effectis most desired propery of material.It is individualcharacteristicsand strongly depends on :

Curie temperature,

Degree of freedom for magnetic dipoles during ordering and randomization of particals.

>ferrimagnets, antiferromagnets and spin glass sytems are not suitable forthis application

Alloysofgadolinium producing 3 to 4 K per tesla of change in magnetic field are used for magnetic refrigeration or power generation purposes.

14. Development in WorkingMaterials

>Recent research on materials exhibit a giant entropy change showed.Alloys of gadolinium are promising materials as below as compared to existing stocks.

Gd 5 (Si xGe 1 x) 4,La(FexSi1 x)13Hx

>These are some of the most promising substitutefor Gadolinium.

Such materials are called as magnetocaloric effect materials

15. Development in WorkingMaterials

Magneticrefrigerationworks in the vicinity of a materials Curie temperature

The range of operation is =+/- 20

In 1950sMRCoperated near by 1 to 30 K, in 1976 this range had expanded to 80 C around the Curie temperature.

1997 lead this activity to built commecial and industrial use.

Using the Ericcsons cycle system refrigerator was built and used for 1500 hrs continuously.

Gd alloys, most notablyGd alloy, most notably Gd5(Si2Ge2), due to simultaneous magnetic and crystallographic first order transition, the adiabatic temperature rise was 30%higher than that of Just Gd and 200 600 % thanprevious refrigerent materials.

16. Development in WorkingMaterials

MaterialDy0.5Er0.5)Al2 has paramagnetic to ferromagnetic transition at 40 k where the large peak occur.

Similar is Gd5(Si0.33Ge3.67) shows enormous peak

It is possible to predict weight to mass ratio of components which produce maximum constant magnetic entropy.This technique allows one to find a suitable material composition which has a constant slope on MCE vs temperature plot.It should have good magnetocaloric effect and could withstand the process of cooling.

Gadolinium silicon germanium ternary system ( Gd-Si-Ge ),with stoichiometry of Gd5(SixGe1-x)4

Transition temperatures of the alloys formed by Gd, Tb, Dy, Ho, Er, Tm and Lu shows transitions with transitions above 180 k.

17. Development in WorkingMaterials

10 Amorphous materialsshows high resistivity and improved corrosion resistance which aids the process of magnetic refrigeration.

Amorphous alloys may be able to fill up the gaps between100 to 200k

Gd0.54Er0.46)NiAlhas 11 top effects, is currently being implemented in Erriccson cycle refrigerators.

18. NUCLEARDEMAGNETIZATION

This type is one of the variant that continues to find substantial research application.

It follows the same principle,but in this case the cooling powerarises from the magnetic dipoles of the nuclei of refrigent atoms rather than their electronic configuration.

Since these dipoles ar of much smaller magnitude, they are less prone to self alignment and have lower intrinsic minimum field.

This allows NDR to cool the nuclear spin system to very low temperatures, often 1 micro kelvin.

Magnetic fieldsof 3 telsa or greator are often needed for the intialmgneizationstep ofNDR

19. NANO MATERIALS FOR REFRIGERATION

Newresearchshows that nanocomposites from metallic glasses

could make promising magnetic refrigeration materials,

>These materialsare as good as the best currenly available magnetic refrigerantswith added adavantages.

>Thisleads to environmental friendlyand more efficient than the existing devices that rely on a vapour cycle.

Energy effiiciency reaches upto 60 % .This saves 40% energy.

Working temperatures and operating range can be tailored by tuning the composition and manipulating the microstructure.

Properties are similar to crystallized and amorphous materials due to unique microstructure

20. NUCLEARDEMAGNETIZATION

This type is one of the variant that continues to find substantial research application.

It follows the same principle,but in this case the cooling powerarises from the magnetic dipoles of the nuclei of refrigent atoms rather than their electronic configuration.

Since these dipoles ar of much smaller magnitude, they are less prone to self alignment and have lower intrinsic minimum field.

This allows NDR to cool the nuclear spin system to very low temperatures, often 1 micro kelvin.

Magnetic fieldsof 3 telsa or greator are often needed for the intialmgneizationstep ofNDR

21. NUCLEARDEMAGNETIZATION

Nano composite made of gadolinium nanocrystallites embedded in a gadolinium-aluminium-manganese (Gd60Al10Mn30) metallic glass matrix.

These materials exhibits unique properties of hysteric and hard magnetic behaviour, which reduces the efficiency of cooling process.

Structural changes in these materials promote crack nucleation and propogation that can cause severe damage to the refrigerant material during cycling.Disadvantage of material.

22. PromotingenergyefficeincyThanking you