report magnetic refrigeration

Magnetic Refrigeration
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A SEMINAR REPORT ON
MAGNETIC REFRIGERATION
Submitted in partialfulfilment of the requirement forth
Award of the degree of
BACHELOR OF TECHNOLOGY
In
MECHANICAL ENGINEERING

Submitted in partialfulfilment of the requirement forth
Award of the degree of
BACHELOR OF TECHNOLOGY
In
MECHANICAL ENGINEERING

At last but not least, we thank the almighty for showering the blessings upon us.
Place: Name of student
Date:

ABSTRACT
The objective of the paper is to study the Magnetic Refrigeration which makes use
of solid materials such as Gadolinium silicon compounds as the refrigerant. These materials
illustrate the unique property known as magneto caloric effect, where there is an increase
or decrease in temperature when magnetized or demagnetized respectively. This effect was
observed many years ago and was used for cooling to near absolute zero temperature .In
the recent times materials are being developed in which enough temperature and entropy
change is produced which makes them useful for a wide range temperature applications.
Magnetic refrigeration is an emerging technology that utilizes this magneto-caloric effect
found in solid state to produce a refrigeration effect. The combination of solid-state
refrigerants, water based heat transfer fluids and its high efficiency unlike the traditional
methods lead to environmentally desirable products with minimal contribution to global
warming. If current research efforts are successful, within a few years, you may find
compressors and evaporators only in the history books. However, so far a few prototype
refrigeration machines are presented as there are quite a few technological and scientific
challenges need to be overcome. Among the numerous applications of refrigeration
technology, air conditioning applications contributing largest gross cooling power and
using large amount of quantity of electric energy.

TABLE OF CONTANTS
TITLE PAGE NO
ABSTRACT 5
LIST OF TABLES 8
LIST OF FIGURES 9
LIST OF NOMENCLATURE 10
INTRODUCTION
MAGNETIC REFRIGERATION 11
MAGNETO CALORIFIC EFFECT 13
LITERATURE SURVEY
INTRODUCTION 15
JOURNAL STUDIES 15
METHADOLOGY
WORKING PRINCIPLE
MAGNATO CALORIFIC EFFECT 18
THERMODYNAMIC CYCLE 20
ADIABATIC MAGNATIZATION 20
ISOMAGNETIC ENTHALPY TRANSFER 20
ADIABATIC DEMAGNATIZATION 21
ISOMAGNETIC ENTROPIC TRANSFER 22
CONSTRUCTION
COMPONANTS REQUIRED 22
MAGNETS 23
HOT HEAT EXCHANGER 23
COLD HEAT EXCHANGER 23
DRIVE 23
MAGNETO CALORIC WHEEL 24

REQUIREMENTS OF PRACTICAL APPLICATIONS
MAGNETIC MATERIAL 24
REGENERATORS 25
SUPER CONDUCTING MAGNETS 26
ACTIVE MAGNETIC REGENERATORS 27
PRACTICAL APPLICATIONS
RECIPROCATING ACTIVE MAGNETIC 29
REGENERATORS
ROTATING AMR LIQUIFIER 31
FUTURE APPLICATIONS
ADVANTAGES OF MAGNETIC REFRIGERATION 32
TECHNICAL 32
SOCIO-ECONOMICAL 33
DISADVANTAGES OF MAGNETIC
REFRIGERATION 33
COMPARISON
COMPARISON BETBWEEN MAGNETIC AND 34
COVENTIONAL REFRIGERATION
ADVANTAGES OVER VAPOUR COMPRESSION 35
CYCLE REFRIGERATION
DISADVANTAGES OF VAPOUR COMPRESSION 36
AND VAPOUR ABSORPTION REFRIGERATION
5.0 CASE STUDY 37
6.0 CONCLUSION 38
7.0 SCOPE OF FUTURE WORK 39
8.0 REFERANCE 40

LIST OF TABLES
LIST OF TABLES PAGE NO
Table 4.1 comparison between magnetic
refrigeration and conventional
refrigeration
35

LIST OF FIGURES
LIST OF FIGURES PAGE NO
figure 1.2 magneto calorific effect 13
figure 3.1.1 working principle of magneto calorific effect 20
figure 3.1.2(a) thermodynamic cycle 21
figure 3.1.2 (b) t-s diagram of magnetic refrigeration 22
figure 3.2 construction of a rotary magnetic refrigerator 23
figure 3.3.2 regenerator 26
figure 3.3.3 super conducting magnets 26
figure 3.3.4 AMR cycles 28
figure 3.4.1 schematic diagram of reciprocating type amr 30
figure 3.4.2 schematic diagram of a rotary amr liquefier 31
figure 4.1 steps in magnetic refrigeration 34

LIST OF NOMENCLATURE
MCE Magneto calorific effect
𝜇 Permeability of vacuum
𝛿𝑆 Change in Entropy
𝛿𝑇 𝑎𝑑 Change in adiabatic temperature
𝐻𝑖 and 𝐻𝑓 Initial and final magnetic field strength
C Heat capacity at constant magnetic field
𝑑𝑀
𝑑𝑇
Change in Magnetization with respect to temperature
Q Total heat transferred
Gd Gadolinium
GMCE Giant magneto calorific effect materials
AMR Active magnetic regenerators
HHEX Hot heat exchanger
CHEX Cold heat exchanger
COP Coefficient of performance
LN Liquid nitrogen
LNG Liquid natural gas

CHAPTER-1
INTRODUCTION
Refrigeration technology is widely used today. Refrigeration is a process in which
work is done to move heat from one location to another. This work is traditionally done by
mechanical work, but can also be done by magnetism, laser or other means. Magnetic
refrigeration, or adiabatic demagnetization, is a cooling technology based on the magneto
caloric effect, an intrinsic (basic) property of magnetic solids. The refrigerant is often a
paramagnetic salt, such as cerium magnesium nitrate. A strong magnetic field is applied to
the refrigerant, forcing its various magnetic dipoles to align and the entropy of the
refrigerant is lowered. 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.
While magnetic refrigeration is a new refrigeration technology with huge potential
application prospect, characterized by high efficiency, energy saving and environmental
friendly.
Magnetic refrigeration is a process based on the magneto caloric effect, a property of
certain magnetic crystals that causes them to generate heat when they are in the presence
of a magnetic field and cool when they are removed from that field. When a strong
magnetic field is applied to an isolated magnetic material, its randomly oriented magnetic
dipoles tend to align, causing the system to become more ordered. That is, the system's
entropy, the measure of thermodynamic disorder, decreases. The system restores its
entropy balance by heating up several degrees. This solid state phenomenon is similar to
the way a liquid warms as it crystallizes or when a gas warms as it is being compressed.
When the magnetic field is removed, the magnetic dipoles rearrange randomly, the entropy
increases and the solid cools.
Scientists and engineers are learning to exploit this highly reversible process, known
as the magneto caloric effect, to create a novel cryogenic cooling technology that may be
sufficiently energy efficient and reliable to compete with conventional refrigeration
techniques. Magnetic refrigeration performs essentially the same task as traditional

compression-cycle gas refrigeration technology. In both technologies, cooling is the
removal of heat from one place (the interior of a home refrigerator is one commonplace
example) and the rejection of that heat to another place (a home refrigerator releases its
heat into the surrounding air). The traditional refrigeration systems, whether air
conditioners, freezers or other forms, use compounds that are alternately expanded and
compressed to perform the transfer of heat. Magnetic refrigeration systems do the same
job, but with metallic compounds. Compounds of the element gadolinium are most
commonly used in magnetic refrigeration, although other compounds can also be used.
The extremely broad market potential of magnetic refrigeration includes any industry that
requires a low temperature technology. The compact, simple system, a typical magnetic
refrigerator requires only one cubic foot of space, is a potential replacement for traditional
compression-cycle systems that have been in existence for more than 70 years. Magnetic
refrigeration can be more energy efficient than compression-cycle systems; the efficiency
depends on the application and temperature range
Magneto caloric-based cryogenic refrigeration systems could be used for liquefying
industrial gases such as oxygen, nitrogen, argon and helium or fuels such as natural gas,
propane, and hydrogen. This application is particularly attractive since gas liquefaction,
which is costly, inefficient, and energy intensive, must be highly centralized because of
engineering scaling considerations. Researchers are also working on application of
magnetic refrigerators to cool orbiting infrared detectors for military surveillance, medical
imaging devices, and large scale food storage and processing systems.
The magnetic refrigeration at room temperature is an emerging technology that has
drawn the interest of researchers around the world. Magnetic refrigeration is a cooling
technology based on the magneto-caloric effect discovered more than 130 years ago. This
method can be used to attain the temperatures near 0 K, as well as the ranges used in
common refrigerators, depending on the design of the system .The effect was first observed
by the German physicist Emil Warburg in the year 1881, and the basic principle was then
suggested by Debye (1926) and Giauque (1927). The first working magnetic refrigerators
were constructed by many people from 1933. Magnetic Refrigeration was the first method
developed for cooling below about 0.3K

Figure 1.2 Magneto Calorific Effect
MAGNETO CALORIFIC EFFECT
When a magneto-caloric material is subjected to a strong magnetic field (measured in
Tesla, T), the electrons present in the material are forced into alignment with the magnetic
field. That is, the magnetic field performs work to align the electron spins into
thermodynamically lower energy state. The energy released during the process causes the
temperature of the material to rise. When the magnetic field is lowered, the electron spins
return to their more random and zigzag motion, higher energy state, absorbing heat from
the material and causing the temperature to fall
Magneto calorific effect is the basic principle on which the cooling is achieved. All
magnets bears a property called Currie effect ie If a temperature of magnet is increased
from lower to higher range at certain temperature, magnet loses the magnetic field. 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
MCE works only in the vicinity of a material's transition temperature. MCE reaches a
maximum value at a material's Curie temperature, the temperature above which a
ferromagnetic material becomes paramagnetic due to the noise generated by atomic
vibrations and further away from this point the weaker the magneto calorific effect.

The range of temperatures about which a material experiences a substantial MCE and
adiabatic temperature drop is typically ± 20° C around the Curie temperature. This effect
is obeyed by all transition metals and lanthanide series elements.
One of the most notable examples of the magneto caloric effect is in the chemical
element gadolinium, a rare earth material and some of its alloys. It was used as the
refrigerant for many of the early magnetic refrigeration designs. The magnetic refrigeration
is mainly based on magneto caloric effect according to which some materials change in
temperature when they are magnetized and demagnetized.

INTRODU
CTION
CHAPTER 2
LITERATURE SURVEY
The purpose of this chapter is to provide a literature survey of past research effort
such as journals or articles related to magnetic refrigeration and to study the new inventions
related to this topic. Moreover, review of other relevant research studies are made to
provide more information in order to understand more on this research.
JOURNAL STUDIES
An Introduction to New RefrigerationTechnologyMagnetic
Refrigeration
Smt. Kinnari S. Damania
From the journal An Introduction to New Refrigeration Technology Magnetic
Refrigeration, Magnetic Refrigeration which uses solid material as the refrigerant. These
materials demonstrate the unique property known as magneto caloric effect, which means
that they increase and decrease in temperature. This paper focuses on the working principle,
comparison with conventional methods, different magneto caloric materials, benefits and
Practical applications of magnetic refrigeration. Benefits of magnetic refrigeration are
lower cost, longer life, lower weight and higher efficiency because it only requires one
moving part-the rotating disc on which the magneto-caloric material is mounted. The unit
uses no gas compressor, no pumps, no working fluid, no valves and no ozone destroying
chlorofluorocarbons/hydro chlorofluorocarbons. Potential commercial applications
include cooling of electronics, super conducting components used in cooling of electronics,
superconducting components used in telecommunication equipment, home and
commercial refrigerator, air conditioning for homes, offices and automobiles and virtually
any places where refrigeration is needed.
At the end of this study it is concluded that, Large MCE of magnetic material is
investigated for room temperature magnetic cooling application strong magnetic field is
required. Magnetic materials available for room temperature magnetic refrigeration are
mainly Gd, GdSiGealloys, MnAs-like materials, perovskite like materials. Excellent

behavior of regenerator and heat transfer is required. Room temperature magnetic
refrigeration is a new highly efficient.
A Review on Magnetic RefrigerationatRoom Temperature
Yash Kulkarni
From the journal A Review on Magnetic Refrigeration at Room Temperature, to
study the Magnetic Refrigeration which makes use of solid materials such as Gadolinium
silicon compounds as the refrigerant. These materials illustrate the unique property known
as magneto caloric effect, where there is an increase or decrease in temperature when
magnetized or demagnetized respectively. This effect was observed many years ago and
was used for cooling to near absolute zero temperature. In the recent times materials are
being developed in which enough temperature and entropy change is produced which
makes them useful for a wide range temperature applications. Magnetic refrigeration is an
emerging technology that utilizes this magneto-caloric effect found in solid state to produce
a refrigeration effect. The combination of solid-state refrigerants, water based heat transfer
fluids and its high efficiency unlike the traditional methods lead to environmentally
desirable products with minimal contribution to global warming. If current research efforts
are successful, within a few years, you may find compressors and evaporators only in the
history books. However, so far a few prototype refrigeration machines are presented as
there are quite a few technological and scientific challenges need to be overcome. Among
the numerous applications of refrigeration technology, air conditioning applications
contributing largest gross cooling power and using large amount of quantity of electric
energy.
From the end of this study it is concluded that, there are two conditions which limits
the applications of the technology in its current state. The first is the temperature span. As
the difference between the upper and lower temperature levels is large, the number of
stages also becomes also large and is practically not economic. The second condition is
regarding the stability of the running conditions. Because the Magneto-caloric effect is
limited to a domain around the Curie temperature where the continuous phase transition
occurs, it is difficult to operate magnetic refrigerating machines under highly fluctuating
conditions.

More or less stable temperature levels are required. 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.

CHAPTER 3
METHODOLOGY
WORKING PRINCIPLE
MAGNETO CALORIFIC EFFECT
The Magnetic Refrigeration works on the principle of Magneto-Calorific Effect. It
is basically a thermodynamic effect caused due to the changing magnetic field, hence called
as magneto thermodynamic phenomenon. 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 some physicists,
because of its application in the process to cause the 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 distressing action of the thermal energy
(phonons) present in the material. If the material is isolated so that no energy exchange is
allowed to between the material and its surrounding i.e (dQ=0 an adiabatic process), the
temperature drop takes place as the domains absorb the thermal energy to perform their
reorientation
When the magneto-caloric material is subjected the magnetic field, the magnetic
moments of soft ferromagnetic materials get aligned, making the material more ordered.
Hence the material liberates more heat and which results in the decrease of their magnetic
entropy. But, when the magnetic material subjected to the magnetic field is reduced
isothermally, the magnetic moments become disoriented, due to which the material absorbs
heat and consequently their magnetic entropy increases. The magnetic entropy change that
takes place due to the magneto-caloric effect can be expressed in the form of equation as
below
𝐻 𝑓
𝜕𝑆 = 𝜇 ∫
𝐻𝑖
( 𝑑𝑀)
( 𝑑𝑇)
𝑑𝐻

=−𝜇 𝑓
While the adiabatic temperature change can be given by the expression as shown
below
𝜕𝑇 𝐻 𝑇 𝑑𝑀∫ [ ] ( ) 𝑑𝐻
Where,
𝑎𝑑
`𝜇 - Permeability of vacuum
𝐻𝑖 𝐶 𝑑𝑇
𝐻𝑖and𝐻 𝑓- the initial and final magnetic field strength respectively
C - is the heat capacity at constant magnetic field
𝛿𝑆 - is the change in Entropy
𝛿𝑇 𝑎𝑑 -Change in adiabatic temperature
𝑑𝑀
-Change in Magnetization with respect to temperature
𝑑𝑇
Now given the two equations for change in entropy and change in adiabatic
temperature, refrigeration capacity for a magnetic refrigerator, which helps in analyzing
how much heat is actually transferred in one refrigeration cycle
𝑇 𝑓
𝑄 = ∫ 𝑑𝑆 𝑑𝑇
𝑇 𝑖
From the above equations we can conclude that magneto-caloric effect can be
enhanced by applying a large field, using a magnet and small heat capacity, using a magnet
with a large change in magnetization vs temperature, at a constant magnetic field
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 drops
back to normal. The effect is considerably stronger for the gadolinium alloy Gd5(𝑆𝑖2Ge2).
Praseodymium alloyed with nickel (Pr𝑁𝑖2) 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

Figure 3.1.1 magneto calorific effect
THERMODYNAMIC CYCLE
The basic thermodynamic cycle of the magnetic refrigerator is Bryton Cycle, which
operates between two adiabatic and two isomagnetic field lines. The working material is
the refrigerant, and starts in thermal equilibrium with the refrigerated environment
Adiabatic magnetization
A magneto caloric material when placed in an insulated environment (Q=0) and
external magnetic field is increased (+H) it causes the magnetic dipoles of the atoms to
align and thereby decreasing the material's magnetic entropy and heat capacity. Since
overall energy is not lost during this process, hence the total entropy also does not change,
the net result is that the object heats up (T + ΔTad).
Isomagnetic enthalpy transfer
The magnetic field is held constant during this process (H=0) and the heat added
during the adiabatic magnetization is then removed (-Q) by a fluid or gaseous substance.
to prevent the dipoles from reabsorbing the heat. Once completely cooled, the magneto-
caloric substance and the coolant are separated.

Adiabatic demagnetization
The substance is returned to another adiabatic process (Q=0) and hence the total
entropy remains constant. However, this time the magnetic field is reduced, the thermal
energy causes the magnetic moments to overcome the field, and thus the sample cools, i.e.,
an adiabatic temperature change energy (and entropy) transfers from thermal entropy to
magnetic entropy (disorder of the magnetic dipoles).
Isomagnetic entropic transfer
The magnetic field is held constant to prevent the material from heating backup.
The material is placed in thermal contact with the environment being refrigerated. Because
the working material is cooler than the refrigerated environment (by design), heat energy
migrates into the working material (+Q).

Figure 3.1.2(a)thermodynamic cycle
Figure 3.1.2(b) T-S diagram for magneto calorific cycle
The processes involved in the magnetic refrigeration can be represented using the
T-S diagram of the Bryton cycle as shown below (the cycle involves four processes which
already discussed)
1-2 Adiabatic Magnetization
2-3 Isomagnetic Enthalpy Transfer
3-4 Adiabatic Demagnetization
4-1 Isomagnetic Enthalpy transfer
3.2 CONSTRUCTIONS
Components Required
1. Magnets
2. Hot heat exchanger
3. Cold heat exchanger
4. Drive
5. Magneto caloric wheel

Figure 3.2 constructionof a rotary magnetic refrigerator
Magnets
Magnets are the main functioning elements of the magnetic refrigeration. Magnets
are the one that provide the magnetic field to the material which provide the refrigeration
effect i.e. they lose the heat to the surrounding and gain heat from the space to be cooled
respectively. The magnets used are usually made of ceramic or ferrite
Hot heat exchanger
Here, the heat transfer is taking place between the magneto-caloric material and the
heat exchanger, the heat exchanger gains the heat from the material used and release it into
the surrounding. It makes the transfer of heat much effective.
Cold heat exchanger
The working of the cold heat exchanger is similar as compared to the hot heat
exchanger except that it absorbs the heat from the space to be cooled and gives it to the
magnetic material. It helps to make the absorption of heat more effective
Drive
Drive provides the right rotation to the heat to rightly handle it. Due to this, heat
flows in the right desired direction.

Magneto caloric wheel
It forms as the basic structure of the whole device and it turns through the field of
a permanent magnet. The wheel is packed with spherical particles of the magneto-caloric
material like Gadolinium, which acts as refrigerant. It joins both the magnets to work
orderly.
One of the most important components in the process is magnetic refrigerant. Pure
gadolinium may be regarded as being the ideal substance for magnetic refrigeration, just
as the ideal gas is for conventional refrigeration. Various other compounds are used as the
magnetic refrigerant components as the pure Gadolinium is very rare and cannot be used
in ambient temperature due to its other properties
REQUIRMENTSFOR PRACTICALAPPLICATIONS
Magnetic Materials
Only a limited number of magnetic materials possess a large enough magneto
caloric effect to be used in practical refrigeration systems. The search for the "best"
materials is focused on rare earth metals, either in pure form or combined with other metals
into alloys and compounds .The magneto caloric effect is an intrinsic property of a
magnetic solid. This thermal response of a solid to the application or removal of magnetic
fields is maximized when the solid is near its magnetic ordering temperature. The
magnitudes of the magnetic entropy and the adiabatic temperature changes are strongly
dependent upon the magnetic order process: the magnitude is generally small in
antiferromagnets, ferrimagnets and spin glass systems.
Pure gadolinium may be regarded as being the ideal substance for magnetic
refrigeration, just like the ideal gas is for conventional refrigeration. But just as
conventional systems are practically cannot be operated with ideal gases, magnetic
refrigerators using pure gadolinium is also not possible and it performs better with specially
designed alloys. Below is the list of the promising categories of magneto-caloric materials
for application in magnetic refrigerators
a) Gadolinium- Silicon- Germanium Compounds
b) Binary and ternary intermetallic compounds
c) Manganite’s

d) Lanthanum iron based compounds etc
Gadolinium, a rare earth metal and exhibits one of the largest known magneto-
caloric effects. It was used as the refrigerant in many of the early magnetic refrigeration
systems. The problem with using pure gadolinium as the refrigerant material is that it does
not exhibit a strong magneto-caloric effect at room temperature, where the usual
applications of the effect exist. However, it has been discovered that arc-melted alloys of
gadolinium, silicon, and germanium are quite efficient at room temperature. Gd-Si-Ge
alloys are all considerably large in the presence of a 5 T magnetic field and most of those
Curie temperatures are in the room temperature range. Therefore, this series of alloys meet
the requirements of room temperature magnetic Refrigeration. However, many urgent
problems such as easy oxidation, hard preparation, and high price, need to be settled before
they are applied in room temperature magnetic refrigeration.
Recent research on materials that exhibit a giant entropy change showed that Gd5
(SixGe1 − x)4, La(FexSi1 −x)13Hx and MnFeP1 − xAsx alloys, for example, are some of
the most promising substitutes for Gadolinium and its alloys (GdDy, GdTy, etc.). These
materials are called giant magneto caloric effect materials (GMCE). A few magnetic
materials, however, exhibit a significantly larger MCE, which is known as the giant
magneto caloric effect (GM) More recently, however, it has been discovered that arc
melted alloys of gadolinium, silicon, and germanium are more efficient at room
temperature.
The effect is considerably stronger for the gadolinium alloy Gd5(Si2Ge2).
Praseodymium alloyed with nickel (PrNi5) has such a strong magneto caloric effect that it
has allowed scientists to approach within one thousandth of a degree of absolute zero.
Regenerators
Magnetic refrigeration requires excellent heat transfer to and from the solid
magnetic material. Efficient heat transfer requires the large surface areas offered by porous
materials. When these porous solids are used in refrigerators, they are referred to as
"regenerators”. Typical regenerator geometries include:
 Tubes
 Perforated plates
 Wire screens

 Particle beds
Figure 3.3.2 Regenerator
Super Conducting Magnets
Most practical magnetic refrigerators are based on superconducting magnets
operating at Cryogenic temperatures (i.e., at -269 C or 4 K).These devices are
electromagnets that conduct electricity with essentially no resistive losses. The
superconducting wire most commonly used is made of a Niobium-Titanium alloy. Only
superconducting magnets can provide sufficiently strong magnetic fields for most
refrigeration applications. A typical field strength is 8 Tesla (approximately 150,000 times
the Earth's magnetic field).An 8 Tesla field can produce a magneto caloric temperature
change of unto 15 C in some rare-earth materials.
Figure 3.3.3 super conducting magnets

Active Magnetic Regenerators (AMR's)
A regenerator that undergoes cyclic heat transfer operations and the magneto
caloric effect is called an Active Magnetic Regenerator (AMR).An AMR should be
designed to possess the following attributes: These requirements are often contradictory,
making AMR's difficult to design and fabricate.
1. High heat transfer rate
2. Low pressure drop of the heat transfer fluid
3. High magneto caloric effect
4. Sufficient structural integrity
5. Low thermal conduction in the direction of fluid flow
6. Low porosity
7. Affordable materials
8. Ease of manufacture
The AMRR consists of regenerator beds, magnets, pumps, and heat exchangers.
The regenerator beds are packed with particle magnetic materials that are subjected to
changing magnetic fields controlled by external magnets. The working fluid alternates
between the hot end and the cold end synchronously with the external magnetic field
changes. By repeating the process, this regenerator operates as a refrigerator and the forms
the AMR cycle
Four steps of Active Magnetic Regenerator Refrigeration cycle (AMRR)
1) Magnetizing
2) Flow from cold to hot
3) Demagnetizing
4) Flow from hot to cold

Figure .3.3.4 schematic diagramof AMR
Figure 3.3.4 AMR cycles

PRACTICAL APPLICATIONS
 Reciprocating Active Magnetic Regenerators
 Rotary Active Magnetic Regenerators liquefier
3.4.1 Reciprocating Active Magnetic Regenerators
The first laboratory prototype tested at the Federal University of Santa Catharina
has been described by Trevizoliet al(2011). The AMR experimental apparatus is shown
schematically in Figure and consisted of a reciprocating system with a fixed regenerator
and a pneumatic system to move the magnet and change the magnetic flux. The regenerator
consisted of 28 parallel plates of commercial-grade Gd plates (160 mm long, 0.85 mm
thick, 6.9 mm height), which formed 26 parallel channels (160 mm long, 0.1 mm thick, 6.4
mm height). The total mass of Gd in the regenerator was195.4 g. The matrix porosity was
9.2 %. The regenerator housing was made of AISI 304 stainless steel, and de-ionized water
was the heat transfer fluid. The magnetic field was generated by Nd2Fe14B permanent
magnets in a Hal Bach array. The (volume) average magnetic field applied on their
generator was approximately 1.22 T (uncertainty of 3.5 %).The operating frequency was
fixed at 0.14 Hz. The hot heat exchanger (HHEX) was a cross-flow mini channel copper
heat exchanger. A thermoelectric module was attached to one side of the heat exchanger
surface to emulate a constant temperature hot source. The cold heat exchanger (CHEX)
was an electric (Joule) heater with a constant dissipation rate.
The results obtained with the reciprocating AMR test device have shown qualitative
agreement with the trends reported in the literature for tests with and without applied
thermal loads. The maximum temperature difference between the hot and cold sources at
zero thermal load was 4.4 K for a utilization factor of 0.4 and THHEX = 296.15 K. For
tests with a thermal load, the typical linear relationship between the cooling capacity and
the temperature difference between the sources has been observed. A maximum cooling
capacity was achieved for a utilization factor of 0.9. In absolute and general terms, the
results obtained with the first lab demonstration prototype were quite modest, which can
be attributed to losses of several types along the cycle. Some of the potential losses have
been investigated numerically by Nielsenet al. (2010). In these numerical simulations, the
spatial variation of the magnetic field was taken into account as was the regenerator

geometry. Considering cases with and without thermal parasitic losses, it was shown that
the numerical AMR model significantly over predicted the zero load temperature span of
the experiment.
Figure 3.4.1 schematicdiagramof a reciprocating AMR
Given the conditions at which the experiments were performed, a better
performance was expected. It was argued that the main cause for the lack of performance
with the first apparatus was that the stainless steel casing acting as regenerator housing
would have such a large thermal conductivity that the regenerator in practice was “short-
circuited” thermally, i.e., the thermal gradient was partially destroyed by the housing.

3.4.2 RotaryActive Magnetic Regeneratorsliquefier
Figure 3.4.1 schematicdiagramof a rotary AMR liquefier
The Cryofuel Systems Group at 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
Process 1–2 is an adiabatic magnetization: The magnetic material is placed in
adiabatic condition, and the heat transfer fluid does not flow. After magnetization, the
temperature is up to (T + Δad) due to the MCE

Process 2–3 is fluid flowing from the magnetic material and heated by absorbing
heat. Then, the temperature of magnetic material is back to T. The fluid rejects heat to hot
reservoir.
Process 3–4 is an adiabatic demagnetization. The magnetic material is in another
adiabatic condition where the magnet filed changes from Bmax> 0 to Bmin=0 and the fluid
does not flow. After demagnetization, the temperature is down to (T-Δad).
Process 4–1 is fluid flowing from hot to cold at B =Bmin. Pushing the fluid back
from hot end to cold end makes the temperature back to T, absorbing heat from cold
reservoir.
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. An option to
realize magnetic freezing applications could be the use of superconducting magnets.
However, this may only be economic in the case of rather large refrigeration units. 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
ADVANTAGES OF MAGNETIC REFRIGERATION
Technical
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

Reduced operating cost: - As it eliminates the most inefficient part of today’s
refrigerator i.e. Compressor. The cost reduces as a result
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.
Reliability: - Due to the absence of gas, it reduces concerns related to the emission
into the atmosphere and hence is reliable one.
Socio-Economic
Competition in global market:-Research in this field will provide the opportunity
so that new industries can be set up which may be capable of competing the global or
international market.
Low capital cost:-The technique will reduce the cost as the most inefficient part
comp. is not there and hence the initial low capital cost of the equipment.
Key factor to new technologies:-If the training and hard wares are developed in
this field they will be the key factor for new emerging technologies in this world.
DISADVANTAGES OF MAGNETIC REFRIGERATION
1. The initial investment is very high when compared to conventional refrigeration.
2. The magneto caloric materials are rare earth materials hence their availability also
adds up to become a disadvantage. These materials need to be developed to allow
larger frequencies of rectilinear and rotary magnetic refrigerators.
3. Protection of electronic components from magnetic fields. But it must be noted that
they are static, of short range and may be shielded
4. Permanent magnets have limited field strength. While, Electromagnets and
superconducting magnets are very 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

CHAPTER 4
COMPARISON
Comparison between magnetic
refrigeration and conventional
refrigeration.
The magneto caloric effect can be utilized in a thermodynamic cycle to produce
refrigeration. Such a cycle is analogous to conventional gas-compression refrigeration.
Figure 4.1 magnetic refrigeration
Co-efficient of Performance: Co-efficient of Performance of magnetic
refrigeration is given by the equation COP= Qc/Win
QC is the cooling power i.e. the heat absorbed from the cold end.
Win is the work input into magnetic refrigerator

Table 4.1 comparison between conventional and magnetic refrigeration
Magnetic refrigeration Conventional refrigeration
Step 1 Magnetize the solid there by
increasing the temperature
Compressing the gas and hence
increasing the temperature
Step 2 Removing the heat from the hot fluid
using heat exchanger
Removing the heat with cooling
fluid
Step3 Demagnetizing adiabatically and
cooling the solid ie, reducing the
temperature
Expansion of
cooling process
gas resulting in
Step 4 Absorb heat from the cooling load Absorb heat from the cooling load
Advantages over vapour compressionand vapour absorption cycles
Magnetic refrigeration performs essentially the same task as traditional
compression-cycle gas refrigeration technology. Heat and cold are not different qualities;
cold is merely the relative absence of heat. In both technologies, cooling is the subtraction
of heat from one place (the interior of a home refrigerator is one commonplace example)
and the dumping of that heat another place (a home refrigerator releases its heat into the
surrounding air). As more and more heat is subtracted from this target, cooling occurs.
Traditional refrigeration systems – whether air-conditioning, freezers or other forms - use
gases that are alternately expanded and compressed to perform the transfer of heat.
Magnetic refrigeration systems do the same job, but with metallic compounds, not gases.
Compounds of the element gadolinium are most commonly used in magnetic refrigeration,
although other compounds can also be used.
Magnetic refrigeration is seen as an environmentally friendly alternative to
conventional vapor cycle refrigeration. And as it eliminates the need for the most
inefficient part of today's refrigerators, the compressor, it should save costs. New materials
described in this issue may bring practical magneto caloric cooling a step closer. A large
magnetic entropy change has been found to occur in MnFeP0.45As0.55 at room
temperature, making it an attractive candidate for commercial applications in magnetic
refrigeration.

The added advantages of MR over Gas Compression Refrigerator are compactness,
and higher reliability due to Solid working materials instead of a gas, and fewer and much
slower moving parts our work in this field is geared toward the development of magnetic
alloys with MCEs, and phase transitions temperatures suitable for hydrogen liquefaction
from Room temperature down to 20 K.
Disadvantages of vapor
compression and vapor absorption
refrigeration
1. Produces toxic gases and chloro-fluoro carbon, thus reducing ozone layer depletion.
2. Very low temperature of order 001K cannot be achieved.
3. The unit produces noise and vibration compared to magnetic refrigerators.
4. Compressor is needed to produce required pressure.
5. An unnecessarily large motor is required to overcome the inertia of the stationary
6. Compressor in case of heavy load applications
7. Large torque loads are placed on the motor, compressor mounts, bearings and belts
at start up.
8. In the lithium bromide absorption refrigeration system, lithium bromide is
corrosive in Nature and in case of the ammonia system, ammonia is toxic,
flammable

CHAPTER 5
CASE STUDY
T. Utaki, T. Nakagawa T. A. Yamamoto and T. Numazawa from Graduate school
of Engineering, Osaka University Osaka, 565-0871, Japan and K. Kamiya from National
Institute for Materials Science, Tsukuba Magnet Laboratory ,Tsukuba, Ibaraki, 305-0003,
Japan have constructed a Active Magnetic Regenerative(AMR) cycle for liquefaction of
hydrogen.
The magnetic refrigerator model they have constructed is based on a multistage
active magnetic regenerative (AMR) cycle. In their model, an ideal magnetic material with
constant magneto caloric effect is employed as the magnetic working substance. The
maximum applied magnetic field is 5T, and the liquid hydrogen production rate is
0.01t/day. Starting from liquid nitrogen temperature (77K), it is assumed that four separate
four stages of refrigeration are needed to cool the hydrogen. The results of the simulation
show that the use of a magnetic refrigerator for hydrogen liquefaction is possibly more than
the use of conventional liquefaction methods.
In general, they have found that, it is helpful to precool hydrogen prior to
liquefaction using a cryogenic liquid such as Liquid nitrogen (LN) or liquid natural gas
(LNG).Therefore, we chose three system configurations to analyze with our numerical
simulation. In the first case, the supplied hydrogen is precooled by the AMRR only. In this
case it is assumed that the magnetic refrigeration system precools the hydrogen from 300
K to 22 K using approximately 7-9 stages of AMRR. In the second case, the supplied
hydrogen is precooled from 300 K to 77 K by LN and from 77 K to 22 K by 3 stages of
AMRR. In the third case, the supplied hydrogen is precooled from 300 K to120 K by LNG
and from 120 K to 22 K by 5 stages of AMRR.
The best performance was achieved by a combined CMR plus a 3-stage AMRR
with LN precooling. It had a total work input of 3.52 kW and had a liquefaction efficiency
of 46.9 %. This provides promise that magnetic refrigeration systems may be able to
achieve higher efficiency than conventional liquefaction methods.

CONCLUSION
Magnetic refrigeration is a technology that has proven to be environmentally safe.
Computer models have shown 25% efficiency improvement over vapor compression
systems. In order to make the Magnetic Refrigerator commercially viable, scientists need
to know how to achieve larger temperature swings. Two advantages to using Magnetic
Refrigeration over vapor compressed systems are no hazardous chemicals used and they
can be up to 60% efficient. There are still some thermal and magnetic hysteresis problems
to be solved for these first-order phase transition materials that exhibit the GMCE to
become really useful; this is a subject of current research. 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).

SCOPE OF FUTURE WORK
In future I will continue my researches on this project topic. I have to verify the
question that magneto caloric refrigeration at near room temperature will succeed or not
commercially. It certainly has great potential from a fundamental thermodynamic
perspective, but it also has several challenges in terms of cost, availability of materials,
manufacturing processes and thermal-hydraulic performance. Future activities will involve
further investigation of this topic, journal reference etc..

REFERANCES
1. Kitanovski A., Egolf P.W., Gendre F., Sari O., Besson CH., 2005, ―A Rotary Heat
Exchanger Magnetic Refrigerator‖. Proceedings of the First international
Conference on Magnetic Refrigeration at Room Temperature, Montreux,
Switzerland, p. 297-307, 27-30 Sept.
2. Gschneidner K., Pecharsky. "Magnetic Refrigeration Materials"."Journal of
Applied Physics". vol.85, no.8,15. April 1999. pp.5365-5368
3. Kitanovski A., Egolf P.W., 2006. The Thermodynamics of Magnetic Refrigeration.
Review Article of the Int. J. Refr. 29, p. 3-21.
4. Rosensweig R.E, Gonin C, Kitanovski A, Egolf P.W., ―20th Informatory Note on
Refrigerating Technologies —magnetic refrigeration at roomTemperature‖
Ecolibrium, February 2008.
5. Engin GED_K a, * MuhammetKAYFEC_b. ―Magnetic Refrigeration Technology
applications on near room temperature‖ from 5th
International Advanced
Technologies Symposium (IATS’09),
6. Zimm C.B., Auringer J., Boeder A., Chell J., Russek S., Sternberg A. (2007) Design
and initial performance of a magnetic refrigerator with arotatingpermanent magnet,
Proc. 2nd International Conferenceon Magnetic Refrigeration at
RoomTemperaturePortorož, Slovenia, p. 341-347.
7. PrakashChawla, AnkitMathur.,―A Review Paper on Development of Magnetic
Refrigerator at Room Temperature‖ from IJIRSE, ISSN(online)- 2347-3207,
Volume 3. Issue. 3 Page 127-140.
8. Jing Li a,b, TakenoriNumazawa a, Hideki Nakagomeb, Koichi Matsumoto, japan,”
Numerical modeling ona reciprocating active magnetic regeneratorrefrigeration in
room temperature” they weredeveloped”
9. Manh-HuongPhana, Hua-XinPenga, Seong-Cho Yub,Nguyen DucThoc, Hoang
Nam Nhatc, Nguyen Chauc,South Korea.” Manganese perovskites for
roomtemperature magnetic refrigeration applications.”

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