A

Seminar

On

“MAGNETIC REFRIGERATION”

By

MR. HARDIK N KOTHIYA

Under The Guidance Of

Prof. J. R. MAHAJAN

Submitted In Partial Fulfillment of the Requirement For

Bachelor of Engineering (Mechanical) Degree

of

University of Pune

Department of Mechanical Engineering

Late G.N. Sapkal College of Engineering,

Anjaneri, Nashik-422212

2013-2014

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Kalyani Charitable Trust’s

Late G. N. Sapkal College of EngineeringSapkal Knowledge Hub, Kalyani Hills, Anjaneri, Trimbakeshwar Road,

Nashik – 422 212, Maharashtra State, India

CERTIFICATE

This is to certify that Mr. HARDIK N KOTHIYA has successfully

completed his Seminar on the topic “MAGNETIC REFRIGERATION”,

under the able guidance of Prof. J. R. MAHAJAN towards the partial

fulfillment of Third Year of Mechanical Engineering as laid down by

University of Pune during academic year 2013-14.

Prof. Prof. T.Y. Badgujar

[Seminar Guide] [ H.O.D. Mechanical ]

Dr. Basavaraj S. Balapgol

[Examiner] Principal

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CONTENTACKNOWLEDGEMENTABSTRACTINDEXSr. No.

Description Page No.

1 Introduction 7

2 History 8

3 Refrigeration 9

3.1 Magnetic Refrigeration 9

4 Objective Of Magnetic Refrigeration 10

5 Magneto-caloric Effect 10

6 Working Of Magnetic Refrigeration 12

6.1 Magnetic Refrigeration System 12

6.2 Refrigerator’s Configuration 13

7 Comparison Between Magnetic Refrigeration

& Conventional Refrigeration

14

8 Components 16

9 Application 17

9.1 A Rotary AMR Liquefier 17

9.2 Future Application 17

10 Techinical Benefits 18

11 Advantages 18

12 Disadvantages 19

13 Current & Future Uses 20

14 Conclusion 21

15 Reference 21

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FIGURE INDEX

FIGURE NO. TITLE PAGE NO.

2.1 Emil Warburg Gabriel 8

5.1 Magneto-Caloric Effect 11

5.2 Process of Magneto-Caloric Effect 11

6.1 Flow Process Diagram A 12

6.2 Flow Process Diagram B 13

7.1Comparison Between Magnetic

Refrigeration & Conventional Refrigeration14

7.2Refrigeration Cycle For Conventional Gas

Compression & Magnetic Refrigeration15

8.1 Components 16

9.1 A Rotary AMR Liquefier 17

4

ACKNOWLEDGEMENT

I take this opportunity to express our deep sense of gratitude and respect towards

our guide MR. J. R. MAHAJAN, Department of Mechanical Engineering, Late G N

Sapkal College Of Engineering , NASHIK. I am very much indebted to his for the

generosity, expertise and guidance; I have received from him while collecting data on this

seminar and throughout our studies. Without his support and timely guidance, the

completion of my seminar would have seemed a far fetched dream. In this respect I find

ourselves lucky to have his as our guide. He has guided us not only with the subject

matter, but also taught us the proper style and technique of working and presentation. It is

a great pleasure for me to express my gratitude towards those who are involved in the

completion of my seminar report. I whole-heartedly thank to our HOD Mr. T. Y.

BADGUJAR for their guidance. I am also indebted to all Sr. Engineers and others who

gave me their valuable time and guidance. The various information and sources I used

during my report completion find place in my report.

I am also grateful to Senior Seminar Coordinators respected sir’s.

HARDIK N KOTHIYA

III year, VSem

Deptt. Of Mechanical Engineering (L.G.N.S.COE, Nashik) Magnetic Refrigeration

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ABSTRACT

The objective of this effort is to study the Magnetic Refrigeration which uses

solid materials as the refrigerant. These materials demonstrate the unique property known

as magneto caloric effect, which means that they increase and decrease in temperature

when magnetized/demagnetized. This effect has been observed for many years and was

used for cooling near absolute zero. Recently materials are being developed which have

sufficient temperature and entropy change to make them useful for a wide range

temperature applications.

Magnetic refrigeration is an emerging technology that exploits the magneto-

caloric effect found in solid state refrigerants. The combination of solid-state refrigerants,

water based heat transfer fluids and high efficiency leads to environmentally desirable

products with minimal contribution to global warming. Among the numerous application

of refrigeration technology air conditioning applications provide the largest aggregate

cooling power and use of the greatest quantity of electric energy.

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1. INTRODUCTION

Refrigeration is the process of removing heat from matter which may be a solid,

a liquid, or a gas. Removing heat from the matter cools it, or lowers its temperature. In

the mechanical refrigeration a refrigerant is a substance capable of transferring heat that it

absorbs at low temperatures and pressures to a condensing medium; in the region of

transfer, the refrigerant is at higher temperatures and pressures. By means of expansion,

compression, and a cooling medium, such as air or water, the refrigerant removes heat

from a substance and transfers it to the cooling medium.

Our society is highly dependent on reliable cooling technology. Refrigeration is

critical to our health and the global economy. Consumer application includes air

conditioning, food preservation, air dehumidification, beverage dispensing and ice

making without refrigerant ion the food supply wood still be seasonal and limited to

locally produced non-perishable items.

Modern refrigeration is almost entirely based on a compression/ expansion

refrigeration cycle. It is a mature, reliable & relatively low cost technology. Over the

years ,all parts of a conventional refrigerator were considerably improved due to extended

research and development efforts. Furthermore, some liquids used as refrigerants are

hazardous chemicals, while other eventually escape into the environment contributing

towards ozone layer depletion and global warming and therefore, conventional

refrigeration ultimately promotes deleterious trends in the global climate.

Magnetic refrigerator, which has advantages in refrigeration efficiency,

reliability, low noise and environmental friendliness with respect to the conventional gas

refrigerators, is becoming a promising technology to replace the conventional technique.

The development of the magnetic material, magnetic refrigeration cycles, magnetic field

and the refrigerator of room temperature magnetic refrigeration is introduced.

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2. HISTORY

Fig. 2.1 Emil Warburg Gabriel

The effect was discovered in pure iron in 1881 by E. Warburg. Originally, the

cooling effect varied between 0.5 to 2 K/T. Major advances first appeared in the late

1920s when cooling via adiabatic demagnetization was independently proposed by two

scientists: Debye (1926) and Giauque(1927).

The process was demonstrated a few years later when Giauque and MacDougall

in 1933 used it to reach a temperature of 0.25 K. Between 1933 and 1997, a number of

advances in utilization of the MCE for cooling occurred.

This cooling technology was first demonstrated experimentally by chemist Nobel

Laureate William F. Giauque and his colleague Dr. D.P. MacDougall in 1933 for

cryogenic purposes (they reached 0.25 K) In 1997, the first near room temperature proof

of concept magnetic refrigerator was demonstrated by Prof. Karl A. Gschneidner, Jr. by

the Iowa State University at Ames Laboratory. This event attracted interest from

scientists and companies worldwide that started developing new kinds of room

temperature materials and magnetic refrigerator designs.

Refrigerators based on the magneto caloric effect have been demonstrated in

laboratories, using magnetic fields starting at 0.6 T up to 10 teslas. Magnetic fields above

2 T are difficult to produce with permanent magnets and are produced by a

superconducting magnet (1 tesla is about 20,000 times the Earth's magnetic field).

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3.REFRIGERATION

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 purpose of

refrigeration is lowering the temperature of the enclosed space or substance and then

maintaining that lower temperature. The term cooing refers generally to any natural or

artificial process by which heat is dissipated. The process of artificially producing

extreme cold temperatures is referred to as cryogenics. Cold is the absence of heat, hence

in order to decrease a temperature, one “removes heat", rather than "adding cold." In

order to satisfy the Second Law of Thermodynamics, some form of work must

be performed to accomplish this. This work is traditionally done by mechanical work but

can also be done by magnetism, laser or other means.

3.1 MAGNETIC REFRIGERATION

Magnetic refrigeration, or adiabatic demagnetization, is a cooling technology

based on the magneto caloric effect, an intrinsic property of magnetic solids. The

refrigerant is often a paramagnetic salt, such as cerium magnesium nitrate. The active

magnetic dipoles in this case are those of the electron shells of the paramagnetic atoms.

A strong magnetic field is applied to the refrigerant, forcing its various magnetic

dipoles to align and putting these degrees of freedom of the refrigerant into a state of

lowered entropy. A heat sink then absorbs the heat released by the refrigerant due to its

loss of entropy. 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.

Because few materials exhibit the needed properties at room temperature, applications

have so far been limited to cryogenics and research.

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4. OBJECTIVES OF MAGNETIC REFRIGERATION

To develop more efficient and cost effective small scale H2 liquefiers as an

alternative to vapor-compression cycles using magnetic refrigeration. With the help of

magnetic refrigeration our objective is to solve the problem of hydrogen storage as it

ignites on a very low temperature. Hydrogen Research Institute (HRI) is studying it

with the help of magnetic refrigeration. We provide the cooling for the hydrogen storage

by liquefying it.

The hydrogen can be liquefied at a low temperature and the low temperature is

achieved with the help of magnetic refrigeration. Thus, the magnetic refrigeration also

provides a method to store hydrogen by liquefying it. The term used for such a device is

magnetic liquefier.

5. MAGNETO CALORIC EFFECT

The Magneto caloric effect (MCE, from magnet and calorie) is a magneto-

thermodynamic phenomenon in which a reversible change in temperature of a suitable

material is caused by exposing the material to a changing magnetic field. This is also

known as adiabatic demagnetization by low temperature physicists, due to the

application of the process specifically to affect a temperature drop. In that part of the

overall refrigeration process, a decrease in the strength of an externally applied magnetic

field allows the magnetic domains of a Chosen (magneto caloric) material to become

disoriented from the magnetic field by the agitating Action of the thermal energy

(phonons) present in the material. If the material is isolated so that no energy is allowed

to (e) migrate into the material during this time (i.e. an adiabatic process), the temperature

drops as the domains absorb the thermal energy to perform their reorientation.

One of the most notable examples of the magneto caloric effect is in the chemical

element gadolinium and some of its alloys. Gadolinium's temperature is observed to

increase when it enters certain magnetic fields. When it leaves the magnetic field, the

temperature returns to normal. The effect is considerably stronger for the gadolinium

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alloy Gd5 (Si2Ge2). Praseodymium alloyed with nickel (Pr Ni 5) has such a strong

magneto caloric effect that it has allowed scientists to approach within one thousandth of

a degree of absolute zero. Magnetic Refrigeration is also called as Adiabatic

Magnetization.

Fig. 5.1 Magneto-Caloric Effect

Fig. 5.2 Process of Magneto-Caloric Effect

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1. WORKING OF MAGNETIC REFRIGERATION SYSTEM

6.1 Magnetic Refrigeration system : -

Consists of two beds containing spherical powder of Gadolinium with water

being usedas the heat transfer fluid. The magnetic field for this system is 5 Wb/m2,

providing a temperature span of 38 K. The process flow diagram for the magnetic

refrigeration system is shown in Fig.

Fig. 6.1 Flow process diagram A

A mixture of water and ethanol serves as the heat transfer fluid for the system.

The fluid first passes through the hot heat exchanger, which uses air to transfer heat to the

atmosphere. The fluid then passes through the copper plates attached to the no

magnetized cooler-magneto caloric beds and loses heat. A fan blows air over this cold

fluid into the freezer to keep the freezer temperature at approximately 0°F. The heat

transfer fluid then gets heated up to 80°F, as it passes through the copper plates adjoined

by the magnetized warmer magneto caloric beds, where it continues to cycle around the

loop. However, the magneto caloric beds simultaneously move up and down, into and out

of the magnetic field. The temperature of the refrigerator section is kept around 39°F.

6.2 Refrigerator Configuration :-

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The typical household refrigerator has an internal volume of 165-200 litres,

where the freezer represents approximately 30% of this volume. Freezers are designed to

maintain at temperature of 0°F. Refrigerators maintain a temperature of 39°F. The

refrigerator will be insulated with polyurethane foam, one of the most common forms of

insulation available. The refrigerator is kept cool by forcing cold air from the freezer into

the refrigerator by using a small fan.

Fig. 6.2 Flow process diagram B

The control system for maintaining the desired internal temperatures consists of

two thermostats with on/off switches. The freezer thermostat regulates the temperature by

turning the compressor off when the temperature gets below 0°F. A second thermostat

regulates the fan that cools the refrigerator to 39°F. To maintain a frost-free environment

in the freezer, a defrost timer will send power to a defrost heater on the coils for a fifteen

minute time period every eight hours. In the first six minutes, the walls of the freezer will

be defrosted. The water will then drain into a pan at the base of the refrigerator. The next

nine minutes involve the safety factor of not reaching a temperature in the freezer that is

too high. Also, a safety thermostat keeps the liquid water from freezing as it drains.

The heat transfer fluid for the magnetic refrigeration system is a liquid alcohol

water mixture. The mixture used in the design consists of 60 % ethanol and 40 % water.

This mixture has a freezing point of –40°F, assuring that the mixture does not freeze at

operating temperatures. This heat transfer fluid is cheaper than traditional refrigerants

and also eliminates the environmental damage produced from these refrigerants.

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7. COMPARISON BETWEEN MAGNETIC REFRIGERATION

AND CONVENTIONAL REFRIGERATION

Fig. 7.1 Comparison between Magnetic Refrigeration and Conventional Refrigeration

In Figure 2 the four basic steps of a conventional gas compression/ Expansion

refrigeration process are shown. These are a compression of a gas, extraction of heat,

Expansion of the gas, and injection of heat. The two Process steps extraction of heat and

expansion are Responsible for a cooling process in two steps. The main Cooling usually

occurs through the expansion of the gas.

The steps of a magnetic refrigeration process are Analogous. By comparing a

with b, in Figure.2 one can see That instead of compression of a gas, a magnetocaloric

Material is moved into a magnetic field and that instead of Expansion it is moved out of

the field. As explained in the Previous section, these processes change the temperature Of

the material and heat may be extracted, respectively Injected just as in the conventional

process. There are Some differences between the two processes. The heat Injection and

rejection in a gaseous refrigerant is a rather Fast process, because turbulent motion

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transports heat Very fast. Unfortunately, this is not the case in the solid Magneto-caloric

materials. Here, the transport mechanism For heat is slow molecular diffusion. Therefore,

at present fi Ligree porous structures are considered to be the best Solution to overcome

this problem. The small distances From the central regions of the material to an adjacent

fluid Domain, where a heat transport fluid captures the heat and Transports it out of the

material, are ideal to make the Magnetic cooling process faster. Furthermore, the not very

Large adiabatic temperature differences of magneto-caloric Materials will require more

often a design of cascade or Regenerative magnetic refrigerators than in conventional

Refrigerators and hence require additional heat transfer Steps. In the is the conventional

gas compression Process is driven by continuously repeating The four different basic

processes shown and is the Magnetic refrigeration cycle comparison. Compression is

Replaced by adiabatic magnetization and expansion by Adiabatic demagnetization.

Fig. 7.2 Refrigeration cycles for conventional gas compression and magnetic

refrigeration

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8. COMPONENTS

Components required for construction :-

Fig. 8.1 Components

1. Magnets : - Magnets are the main functioning element of the magnetic refrigeration.

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.

2. Hot Heat Exchanger : - The hot heat exchanger absorbs the heat from the material used and gives off to

the surrounding. It makes the transfer of heat much effective.

3. Cold Heat Exchanger :- 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 effective.

4. Drive : - Drive provides the right rotation to the heat to rightly handle it. Due to this heat

flows in the right desired direction.

5. Magneto caloric Wheel : -It forms the structure of the whole device. It joins both the two magnets to work properly.

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9. APPLICATIONS

9.1 A rotary AMR liquefier :-

The Cryofuel Systems Group is developing an AMR refrigerator for the purpose

of liquefying natural gas. A rotary configuration is used to move magnetic material into

and out of a superconducting magnet. This technology can also be extended to the

liquefaction of hydrogen.

Fig. 9.1 A Rotary AMR liquefier

9.2 Future Applications:-

In general, at the present stage of the development of magnetic refrigerators with

permanent magnets, hardly any freezing applications are feasible. These results, because

large temperature spans occur between the heat source and the heat sink. Such are used

for freezing, e.g. in cooling plants in the food industry or in large marine freezing

applications. Some of the future applications are:

1. Magnetic household refrigeration appliances

2. Magnetic cooling and air conditioning in buildings and houses

3. Central cooling system

4. Refrigeration in medicine

5. Cooling in food industry and storage

6. Cooling in transportation

7. Cooling of electronics

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10. TECHNICAL BENEFITS

2. High efficiency: - As the magneto caloric effect is highly reversible, the thermo

dynamic efficiency of the magnetic refrigerator is high. It is somewhat 50% more

than Vapor Compression cycle.

3. Reduced operating cost: - As it eliminates the most inefficient part of today’s

refrigerator i.e. comp. The cost reduces as a result.

4. Compactness: - It is possible to achieve high energy density compact device. It is

due to the reason that in case of magnetic refrigeration the working substance is a

solid material (say gadolinium) and not a gas as in case of vapor compression

cycles.

5. Reliability: - Due to the absence of gas, it reduces concerns related to the emission

into the atmosphere and hence is reliable one.

11. ADVANTAGES

1. Environmental friendly: - Conventional refrigerator use refrigerant that contains

CFC or HCFC, which have been linked to Ozone depletion and global warming.

Some refrigerant like ammonia are toxic and inflammable.

2. Low running and operating cost:-There is no compressor in magnetic

refrigerator, which is most inefficient and costlier part. This leads in less energy

consumption and hence low running cost.

3. Higher efficiency:-Because it eliminates the need to expand and compressed the

liquid, magnetic refrigerator consume less energy and can operate at 60%

efficiency.

4. Wide temperature span: - Operating temperature of magnetic refrigerator can

easily be changed over a wide range from about 30 k to 290 k without losing the

magneto-caloric effect.

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5. Reliability: - High energy density and more compact device, less moving parts as

compared to traditional system hence more reliable.

6. Quite operation: - This refrigerator unit is substantially quite than traditional

refrigeration system.

12. DISADVANTAGES

On the other hand, some disadvantages include:

1. The initial investment is more as compared with conventional refrigeration.

2. The magneto caloric materials are rare earth materials hence their availability also

adds up an disadvantage in MAGNETIC REFRIGERATION.

GMCE materials need to be developed to allow higher frequencies of rectilinear

and rotary magnetic refrigerators.

3. Protection of electronic components from magnetic fields. But notice that they

are static, of short range and may be shielded

4. Permanent magnets have limited field strength. Electromagnets and

superconducting magnets are (too) expensive.

5. Temperature changes are limited. Multi-stage machines lose efficiency through

the heat transfer between the stages.

6. Moving machines need high precision to avoid magnetic field reduction due to

gaps between the magnets and the magneto caloric material.

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13. CURRENT AND FUTURE USES

There are still some thermal and magnetic hysteresis problems to be solved for

these first-order phase transition materials that exhibit the MCE to become really useful;

this is a subject of current research. A useful review on magneto caloric materials

published in 2005 is entitled "Recent developments in magneto caloric materials" by Dr.

Karl A. Gschneidner, .This effect is currently being explored to produce better

refrigeration techniques, especially for use in spacecraft. This technique is already used to

achieve cryogenic temperatures in the laboratory setting (below 10K). As an object

displaying MCE is moved into a magnetic field, the magnetic spins align, lowering the

entropy. Moving that object out of the field allows the object to increase its entropy by

absorbing heat from the environment and disordering the spins. In this way, heat can be

taken from one area to another. Should materials be found to display this effect near room

temperature, refrigeration without the need for compression may be possible, increasing

energy efficiency.

In addition, magnetic refrigeration could also be used in domestic refrigerators.

In 2006, a research group led by Karl Sandeman at the University of Cambridge made a

new alloy, composed of cobalt, manganese, silicon and germanium that can be used for

magnetic refrigeration. This has made the use of the expensive material gadolinium

redundant, and made the creation of domestic magnetic refrigerators possible. The use of

this technology for domestic refrigerators though is very remote due to the high efficiency

of current Vapor-compression refrigeration in the range of 60% of Carnots efficiency.

Gas molecules are responsible for heat transfer, they absorb heat in the inner side of the

refrigerator by expanding and release this heat in the outside by condensing. The work

provided to do this work is a cheap and highly efficient compressor, driven by an electric

motor that is more than 80% efficient. This technology could eventually compete with

other cryogenic heat pumps for gas liquefaction purposes.

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14. CONCLUSION

If we say future perspectives of room temperature Magnetic Refrigeration; It can

be seen from the earlier Description that main progresses have been made in America.

However, with the continual phasic progresses of Room temperature magnetic

refrigeration, the whole world Has accelerated in the research. Nevertheless, it is notable

that main work is concentrated On investigations of magnetic materials, lack of

Experimental explorations of magnetic refrigerator. From The former results achieved by

researchers, it can be seen. At the end of this study we can say;

1. It is a technology that has proven to be environmentally safe.

2. In order to make the magnetic refrigerator commercially Viable, scientists need to

know how to achieve larger temperature swings and also permanent magnets

which can produce strong magnetic fields of order 10 tesla.

3. There are still some thermal and magnetic hysteresis problems to be Solved for

the materials that exhibit the MCE to become really useful.

4. Magnetic materials available for room Temperature magnetic refrigeration are

mainly Gd, Gdsige alloys, mn as-like materials, perovskite like Materials,

5. Materials under development for room Temparature magnetic refrigeration are

La(fexsi1-X)13 and La(Fe0.88Si0.12)13Hy

6. Excellent behavior of regeneration and heat Transfer is required It can be use

household refrigerator, central Cooling systems, room air conditioners and

Supermarket refrigeration applications.

7. This technology must be universalized worldwide.

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15. REFERENCES

1. http://en.wikipedia.org/wiki/Magnetic_refrigeration

2. http://www.scribd.com/doc/19537314/Magnetic-Refrigeration

3. Lounasmaa, experimental principles and methods, academic press

4. Richardson and Smith, experimental techniques in condensed matter physics at low

temperature, Addison Wesley (2003)

5. A text book on cryogenic engineering by V.J.Johnson

6. “Refrigeration and Air conditioning” by Arora and Domkundwar

7. Magnetic Refrigeration, ASHRAE Journal (2007), by John Dieckmann, Kurt Roth and

James Brodrick

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