Magnetic refrigeration1

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Transcript of Magnetic refrigeration1

  • 1. Introduction Objective Magneto Calorific effect Components Thermodynamic Cycle Steps of Thermodynamic cycle Requirements for practical application Example of a prototype Rotary AMRR Advantages Disadvantages Future Applications Comparison Magnetic refrigeration under development Conclusion CONTENTs

2. Refrigeration is a process in which work is done to move heat from one location to another. Magnetic refrigeration is a cooling technology based on the magneto caloric effect. Magneto caloric effect Invented by Emil Warburg in 1880. 3. To understand the Principle and mechanism for generating cooling effect using the magnet To solve the problem of hydrogen storage 4. A reversible change in temperature of a suitable material Variation of internal energy of the material when applied magnetic field changes Intensive property and Extensive property 5. Magnets Hot Heat exchanger Cold Heat Exchanger Drive Magneto caloric wheel 6. Adiabatic magnetization. Isomagnetic enthalpic transfer. Adiabatic demagnetization. Isomagnetic entropic transfer 7. The substance is placed in an insulated environment. External magnetic field (+H) increased. Magnetic dipoles of atoms to align, thereby magnetic entropy and heat capacity decreases. Total Entropy of the item is not reduced, and item heats up. Adiabatic Magnetization 8. This added heat can then be removed by a fluid like water or helium (-Q). The magnetic field is held constant to prevent the dipoles from reabsorbing the heat After sufficient cooling, the magneto caloric material and the coolant are separated (H=0). 9. Substance returned to another adiabatic ( insulated ) condition Total Entropy remains constant Magnetic field is 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 ) 10. Material is placed in thermal contact with the environment being refrigerated. Magnetic field held constant to prevent from heating back up Because the working material is cooler than the refrigerated environment, heat energy migrates into the working material ( +Q ) 11. Magnetic Materials Regenerators Super Conducting Magnets Active Magnetic Regenerators(AMRs) 12. Gd alloys: Gd5(Si2Ge2); Gd5(Si0.33Ge3.67); Gd0.54Er0.46)NiAl Gd5(SixGe1 x)4, La(FexSi1 x)13Hx and MnFeP1 xAsx alloys are some of the most promising substitutes for Gadolinium and its alloys 13. a) Tubes. b) Perforated plates. c) Wire screens. d) Particle beds. 14. High heat transfer rate. Low pressure drop of the heat transfer fluid. High magneto caloric effect. Sufficient structural integrity. Low thermal conduction in the direction of fluid flow. Low porosity. Affordable materials. Ease of manufacture. 15. Example of a Prototype Rotary AMRR Fluid pump Drive motor Magneto caloric wheel Cold HX Permanent magnet 16. Noise-less technology Very high thermodynamic efficiency Lower energy consumption Simple design and building Low maintenance costs Long life Low pressure Green technology (no use of conventional refrigerants) High performance 17. Initial cost Magneto caloric material are rare earth metals Temperature span. Protection of electronic components from magnetic fields. Curie temperature of the magneto caloric material Moving machines need high precision 18. Magnetic household refrigeration Central cooling system Magnetic cooling and air conditioning in buildings and houses Refrigeration in medicine Cooling in food industry and storage Laptop Vehicle air conditioning Storage of Hydrogen 19. A rotating magnetic refrigerator developing by Astronautics Corporation of America Ltd. In collaboration with the Ames Laboratory. 20. No hazardous chemicals used [Environment friendly] Improved efficiency about 25% increase Larger temperature span Permanent magnet need to produce strong magnetic field over 10tesla Some thermal and hysteresis problem 21. Experiments done on Ames Laboratory Magnetic Refrigeration, ASHRAE Journal (2007), by John Dieckmann, Kurt Roth and James Brodrick Lounasmaa, experimental principles and methods, academic press www.google.com http://www.sciencedirect.com/science/article/pii/S014070071200117X http://www.ameslab.gov/files/MagFridge_Foundation.pdf