Seminar On Magnetic Refrigeration
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Transcript of 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