1 Presented By, Ananthu Sivan Feby Philip Abraham S4, Dept. of Mechanical Engineering, Mohandas College of Engineering & Technology, Anad, Trivandrum

INTRODUCTION WHAT IS MAGNETIC REFRIGERATION?? MAGNETOCALORIC EFFECT HOW DOES AN ADR WORK?? MAGNETIC REFRIGERATION CYCLE CONSTRUCTIONAL COMPONENTS WORKING MATERIALS GMCE MATERIALS ALTERNATIVE TECHNIQUES COMMERCIAL DEVELOPMENT CONCLUSION 2

Refrigeration is the process of removing heat from an enclosed space or from a substance and moving it to a place where it is unobjectionable The primary objective of refrigeration is lowering the temperature of the enclosed space or substance and then maintaining that lower temperature. 3

Magnetic refrigeration is a cooling technology based on the magneto caloric effect. It is used to attain temperature well below 1 Kelvin. Magnetic refrigeration currently finds application in cryogenics. 4

Some magnetic materials heat up when they are placed in a magnetic field and cool down when they are removed from a magnetic field. This is known as the magnetocaloric effect. The effect was discovered in pure iron in 1880 by German physicist Emil Warburg In 1997, the first near room temperature proof of concept magnetic refrigerator was demonstrated by Prof. Karl A. Gschneidner 5

Gadolinium alloy heats up inside the magnetic field and loses thermal energy by irradiation, so that it exits the field cooler than when it entered. 6

Magnetic Refrigeration Cycle 1. Adiabatic magnetization 2. Isomagnetic enthalpic transfer 3. Adiabatic demagnetization 4. Isomagnetic entropic transfer 7

1. Working material is placed in an insulated environment 2. Increasing magnetic field is applied 3. Magnetic dipoles of the atoms of the material align 4. Decreases materials magnetic entropy and heat capacity 5. Total entropy of the material remains conserved (Laws of Thermodynamics) 6. Results in heating up of the material (T+ΔT ad ) 8

1. Heat generated in the previous process is removed by a fluid (He or H 2 O) 2. Magnetic field is held constant 3. After being sufficiently cooled, the magnetocaloric material and coolant are separated 9

1. The substance is brought to another insulated environment 2. Magnetic field is decreased 3. Magnetic entropy increases, thermal entropy decreases 4. Material cools down 10

1. Magnetic field is held constant 2. Environment to be cooled is brought in contact with the magnetocaloric material 3. Heat transfers from space to be cooled to the magnetocaloric material 11

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Magnets Hot Heat Exchanger Cold Heat Exchanger Drive Magnetocaloric Wheel 13

Magnets provide the magnetic field to the material so that they can lose or gain the heat to the surrounding and from the space to be cooled respectively 14

The hot heat exchanger absorbs the heat from the material used and gives off to the surrounding. It increases the efficiency of heat transfer 15

The cold heat exchanger absorbs the heat from the space to be cooled and gives it to the magnetic material. It helps to make the absorption of heat efficient. 16

Drive provides the right rotation to the Magneto caloric wheel. Due to this, heat flow in the desired direction is achieved. 17

It forms the base structure of the whole device. It is the fundamental element in the whole system. It joins the two magnets and ensures proper operability. 18

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This is the picture of a proposed commercial magnetic refrigeration system which is being developed by Camfridge and Whirlpool. It is planned to be launched in the UK in the year

Magneto caloric effect is characteristic of the material The ability of a material to produce a change in its temperature per Tesla of change in magnetic field, is the deciding factor. Alloys of gadolinium can be used for magnetic refrigeration. Paramagnetic Salts like Cerium Magnesium Nitrate 21

Giant Magnetocaloric Effect Materials Exhibits GIANT change in entropy Most promising material with respect to magnetic refrigeration, at room temperature Examples - Gd 5 (SixGe 1x ) 4 La(Fe x Si 1x ) 13 H x MnFeP 1x As x 22

Nuclear Demagnetization Refrigeration Working Principle remains the same Cooling power arises from the magnetic dipoles of the nuclei of the refrigerant atoms, rather than their electron configurations. They have much smaller magnetic dipoles Less prone to self alignment Lower intrinsic minimum fields Temperatures of up to 1 µK or less, achievable 23

Pros : 1. Viable in various industries and research facilities 2. Environmentally friendly, as it doesnt require any polluting gases 3. Comparatively lower power consumption, research shows them to be 50% more efficient than conventional cooling systems 4. In commercial refrigeration a key cost is maintenance caused by leakage of refrigerant. By eliminating gases this maintenance cost will be removed. 5. In domestic refrigeration low noise is valuable; elimination of gas compression reduces noise. 24

Cons: 1. Various technical difficulties remain at large 2. Availability of good working material is a concern 3. Superconducting magnets are required to produce sufficient field 4. Magnetic hysteresis losses are considerable for certain materials 25

Gschneidner stated in 1999 that: Large-scale applications using magnetic refrigeration, such as commercial air conditioning and supermarket refrigeration systems, could be available within 5–10 years. Within 10–15 years, the technology could be available in home refrigerators and air conditioners. 26

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