seminar on magnetic refrigeration

• 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