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Magnetic Refrigeration- a Review- a Boon for the Coming Generations Dr

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Magnetic Refrigeration- a Review- a Boon for the Coming Generations Dr SSRG International Journal of Mechanical Engineering ( SSRG – IJME ) – Volume 3 Issue 5 – May 2016 Magnetic Refrigeration- A Review- A boon for the coming generations Dr. L.C.Singal#1, Aishna Mahajan#2, Rajwinder Singh#3 #1Professor, Deptt.of Mechanical Engineering, Chandigarh Engineering College, Landran (Mohali), Punjab, INDIA #2Associate Professor, Deptt. of Mechanical Engineering, Chandigarh Engineering College, Landran (Mohali), Punjab, INDIA #3Assistant Professor, Deptt. of Mechanical Engineering, Chandigarh Engineering College, Landran (Mohali), Punjab, INDIA Abstract magnet is called magnetic refrigeration. It is based on Magnetic cooling is an old concept but being the magneto caloric effect.Magnet caloric effect means tried for day today applications in order to overcome that the temperature of a suitable material changes the disadvantages of conventionally used vapor when magnetized or de-magnetized. This effect has compression refrigeration systems regarding reduced already been used to achieve extremely low power input and freedom from Ozone Depletion and temperatures (0.0001 K) and the temperatures ranges Global Warming. Long back, it has been successfully used in common cooling devices. The effect was first applied in the cryogenic temperature ranges. Magnetic noticed by French physicist P.Weiss and Swiss refrigeration is based on the magneto-caloric effect, a physicist A. Piccar in 1917(4). The fundamental characteristic present in all magnetic materials and principle was suggested by P.Debye (1926) and their alloys. Magnet caloric effect means that the W.Giauque in 1927(5).The first refrigerators working temperature of a suitable material changes when on magnetic refrigeration were constructed by many magnetized or de-magnetized. Magnetization of a groups in 1933. When a magnet is applied to a material magneto-caloric material is equivalent to the which can be magnetized under a magnetic field, the compression of a gas (heating), while demagnetization molecules of the material get arranged in a regular is equivalent to expansion of a gas (cooling). The first pattern and hence randomness of the molecules is most requirements are that these variations must be decreased. It amounts to compression or ordered achievable speedily, repeatedly, reversibly with molecules occupy less space than disordered. Disorder minimum energy losses.In this paper, the applicability changing into an ordered arrangement is exothermic. of this method for room temperature refrigeration and Now the hot salt is cooled with a fluid and then on air conditioning has been studied. Firstly, the magnetic demagnetization, the molecules acquire disordered refrigeration and vapor compression systems have been arrangement which is endothermic. The salt is compared. Secondly, the magneto – caloric materials thermally insulated while being demagnetized; there and their requirements has been listed.Thirdly, the will be a significant drop of temperature.The first most effect of various parameters as strength of the magnetic requirements are that these variations must be field, regenerator configuration, temperature span and achievable speedily, repeatedly, reversibly with refrigerant fluid on the performance of magnetic minimum energy losses.Themaximum cooling effectby refrigerationhas been discussed.Lastly and not the demagnetization has been found ingadoliniumand its least, the advantages and disadvantages has been alloy (Gd5Si2Ge2)andPraseodymium alloyed with mentioned. Magnetic refrigeration seems to posses’ nickel (PrNi5)respectively(6). The new solid-state great potential for future generations. approach appears to be perfect form of cooling and refrigeration in the right direction. Keywords –Magneto caloric material, Adiabatic magnetization, Adiabatic demagnetization, II. MAGNETO-CALORIC EFFECT (MCE) Regenerator, Fluid MATERIALS The magneto-caloric effect (MCE) will be I. INTRODUCTION maximum under a magnetic field when the solid is near As compared to conventional vapor its magnetic ordering temperature. Therefore the compression refrigeration, magnetic refrigeration is materials for magnetic refrigeration should have simple, safe, quiet and compact. It has a higher cooling magnetic phase transition temperature near the efficiency and is more eco-friendly because it does not application temperature as 22 to 270C in air use harmful ozone-depleting and global warming conditioning and 00C in a refrigerator (7-12). This refrigerants (1,2,3). Cooling produced by using a effect has been found to be maximum in ferro-magnetic ISSN: 2348 – 8360 www.internationaljournalssrg.org Page 22 SSRG International Journal of Mechanical Engineering ( SSRG – IJME ) – Volume 3 Issue 5 – May 2016 materials (paramagnetic salts, gadolinium and its of the free energy alloys) because these undergo a magnetic phase with the field, is transition at Curie temperature which is around 200C. discontinuous. These materials are expensive. In February 2014, GE 3. The MCE, in a The MCE, in a announced the development of a functional Ni- SOMT material, SOMT material, Mnbased magnetic refrigerator (13,14). Even this can be measured can be measured material is costly. Hence magnetic refrigeration is not in terms of the in terms of the likely to replace vapor-compression refrigeration till adiabatic adiabatic cheap and abundant magneto caloric materials are temperature temperature found. These materials should also have large magneto change (ΔTad) or change (ΔTad) or caloric effect over a larger range of temperatures under in terms of the in terms of the a magnetic field of two Tesla or less which can be isothermal isothermal produced with permanent magnets (15-27). Magnetic magnetic entropy magnetic entropy refrigeration have already produced lowtemperatures of change (ΔSM) change (ΔSM) 0.0001 k and 0.000001 K respectively using upon magnetic upon magnetic paramagnetic salts and by nuclear demagnetization. field variations. field variations. Since these low temperatures have limited laboratory MCE is However these applications only.Modern research is focused on near measureable from changes (ΔTad) or room temperature refrigeration by magnetic cooling.It the value of (ΔSM) are related will be possible only by the discovery of magneto (ΔTad) or (ΔSM). to (∂M/∂T)H caloric materials such asNiCoMnSb alloys with a parameter. higher concentration of Co decreases the phase change Therefore the temperature (martensitic transition temperature) and MCE becomes also increases the MCE. More research is required to maximum when achieve a breakthrough in finding many more such (∂M/∂T)H reaches suitable cheap materials. There are two types of its maximum magneto caloric materials namely FOMT (First Order value i.e.around Magnetic Transition) and SOMT (Second Order the Curie Magnetic Transition). temperature in a ferromagnetic or III. TABLE I near absolute zero COMPARISON OF FOMT AND SOMT MAGNETO CALORIC in a paramagnetic. MATERIALS [10-40] 4. The FOMT The SOMT 푴풂풕풆풓풊풂풍 FOMT (First SOMT (Second materials show a materials show a Order Magnetic Order Magnetic → simultaneous relatively slow Transition) Transition) Sr.No.↓ ordering of ordering of 1. A FOMT exhibits A SOMT exhibits magnetic dipoles magnetic dipoles a discontinuity in continuity in the and a latent heat and a latent heat the first derivative first derivative, associated with associated with of the Gibbs free but exhibits the transition is the transition is energy discontinuities in a released. released and gives second derivative relatively less of the free energy. MCE. 2. The In a SOMT The 5. There are large There are less magnetization magnetization adiabatic adiabatic effect in FOMT, effect in which is temperature temperature which is the first the first derivative variations in most variations in most derivative of the of the free energy of the FOMT of the SOMT than free energy with with the applied materials than that of FOMT. the applied magnetic field that of SOMT. magnetic field strength, is 6. The temperature The temperature strength, is continuous but the change in the change in the discontinuous magnetic SOMT materials SOMT materials susceptibility, is very slow and is almost which is the small because instantaneous. second derivative these experience a There are no ISSN: 2348 – 8360 www.internationaljournalssrg.org Page 23 SSRG International Journal of Mechanical Engineering ( SSRG – IJME ) – Volume 3 Issue 5 – May 2016 change in structure changes SOMT. for FOMT. structure which during 12. FOMT are costly. SOMT are costly. takes much longer magnetization or In general, SOMT materials seem to be better. But time. demagnetization. lot of research is required to discover cheap magneto 7. Hysteresis losses Hysteresis losses caloric materials having large temperature ranges on are high. are almost magnetization as well as on demagnetization coupled negligible. with durability, convenience and safe disposal after use. 8. Most of the Most of the FOMT are brittle SOMT are not IV. REGENATOR and undergoes brittle and The Magneto Caloric Material is magnetized large volume undergoes almost and heated up under a magnetic field and losses heat to changes on no volume change the surroundings with the use of a fluid (water). It magnetization or on magnetization demagnetizes as well as cooled when the magnetic field demagnetization or is removed, the fluid circulated is cooled. It is then and hence demagnetization. circulated round the space to be cooled like chilled develop cracks. There is a water used in central air conditioning applications.
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