22-07-2010, 09:15 PM
please send me the ppt
22-07-2010, 09:15 PM
please send me the ppt
20-09-2010, 03:11 PM
More Info About magnetic refrigeration ppt
https://seminarproject.net/Thread-magnet...ull-report More Info About magnetic refrigeration ppt https://seminarproject.net/Thread-magnet...ull-report
11-02-2011, 08:58 PM
send me ppt nd pdf of magnetic refrigeration
05-11-2012, 12:53 PM
MAGNETIC REFRIGERATION
MAGNETIC REFRIGERATION.pptx (Size: 132.54 KB / Downloads: 68) Introduction : Principle Mageto calorific effect is the basic principle on which the cooling is achieved. All magnets bears a property called Currie effect i.e. If a temperature of magnet is increased from lower to higher range at certain temperature magnet looses the magnetic field. Currie temperature. Depends on individual property of each material. As Energy input to the magnet is increased the orientation of the magetic dipoles in a maget starts loosing orientation. And vice a versa at currie temperature as maget looses energy to the media it regains the property. Adiabatic magnetization Procedure to be followed : Substance placed in insulated environment. Magnetic field +H increased. Magnetic dipoles of atoms to align, thereby material decreases. Total Entropy of the item is not reduced, and item heats up Isomagnetic enthalpic transfer Added heat removed by fluid, gas – gaseous or liquid helium Magnetic field held constant to prevent the dipoles from reabsorbing the heat. After a sufficient cooling magnetocaloric material and coolant are seperated Isomagnetic entropic transfer 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 ) Once the refrigerent and refrigerated environment are in thermal equillibrium, the cycle begins a new Development in Working Materials Magnetic refrigeration works in the vicinity of a material’s Curie temperature The range of operation is = +/- 20 In 1950’s MRC operated 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 Ericcson’s cycle system refrigerator was built and used for 1500 hrs continuously. Gd alloys, most notably Gd 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 % than previous refrigerent materials. NUCLEAR DEMAGNETIZATION 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 power arises 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 fields of 3 telsa or greator are often needed for the intial mgneization step of NDR
29-11-2012, 06:20 PM
MAGNETIC REFRIGERATION
1MAGNETIC.ppt (Size: 733 KB / Downloads: 46) INTRODUCTION Mageto calorific effect is the basic principle on which the cooling is achieved. All magnets bears a property called Currie effect i.e. If a temperature of magnet is increased from lower to higher range at certain temperature magnet looses the magnetic field. Currie temperature. Depends on individual property of each material. As Energy input to the magnet is increased the orientation of the magetic dipoles in a maget starts loosing orientation. And vice a versa at currie temperature as maget looses energy to the media it regains the property. A heat sink then absorbs the heat released by the refrigerant Thermal contact with the heat sink is then broken so that the system is insulated, and the magnetic field is switched off This increases the heat capacity of the refrigerant, thus decreasing its temperature below the temperature of the heat sink. Principle of Magnetic refrigeration : Mageto calorific effect is the basic principle on which the cooling is achieved. All magnets bears a property called Currie effect i.e. If a temperature of magnet is increased from lower to higher range at certain temperature magnet looses the magnetic field. Currie temperature. Depends on individual property of each material As Energy input to the magnet is increased the orientation of the magnetic dipoles in a magnet starts loosing orientation. And vice a versa at Currie temperature as magnet looses energy to the media it regains the property. Adiabatic Demagnetization The substance is returned to another adiabatic (insulated) condition so the total entropy remains constant thermal energy causes the domains to overcome the field, and thus the sample cools Working Materials Magneto caloric effect is an intrinsic property of magnetic solid. Ease of application and removal of magnetic effect is most desired propery of material. It is individual characteristics and strongly depends on : Curie temperature Degree of freedom for magnetic dipoles during ordering and randomization of particals. |
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