Magnetic refrigeration is considered as a more reliable and sustainable source to generate cooling and effect in the working fluid using a hysteresis effect. Magnetically soft material with less hysteresis loop area has been recommended for this project.

1. 1
DESIGN AND TESTING OF PROTOTYPE MAGNETIC
REFRIGERATION
SUPERVISOR:
DR. MUHAMMAD SAJID KAMRAN
MISS ANUM ABBAS
GROUP MEMBERS
MUHAMMAD USMAN 2015-ME-12
MUZAFFAR HUSSAIN 2015-ME-34
DEPARTMENT OF MECHANICAL ENGINEERING
UNIVERSITY OF ENGINEERING AND TECHNOLOGY, LAHORE

2. 2
DESIGN AND TESTING OF PROTOTYPE MAGNETIC
REFRIGERATION
GROUP MEMBERS
MUHAMMAD USMAN (2015-ME-12)
MUZAFFAR HUSSAIN (2015-ME-34)
A thesis is submitted to partially fulfill the requirements for the degree of B.Sc. Mechanical
Engineering
Approved on: ______________________
EXTERNAL EXAMINER SIGNATURE: _____________________
THESIS SUPERVISOR SIGNATURE: ______________________
CHAIRMAN’S SIGNATURE: ______________________
DEPARTMENT OF MECHANICAL ENGINEERING
UNIVERSITY OF ENGINEERING AND TECHNOLOGY, LAHORE

3. 3
DECLARATION
We hereby declare that this research work is purely of our own hard work and has not been
published anywhere else before in any of the format. The matter quoted in this text has been
properly referred and acknowledged.
Researchers
MUHAMMAD USMAN
__________________________
MUZAFFAR HUSSAIN
____________________________
DEPARTMENT OF MECHANICAL ENGINEERING
UNIVERSITY OF ENGINEERING AND TECHNOLOGY, LAHORE

4. 4
ACKNOELEDGEMENTS
I seek refuge in ALLAH from the Satan the outcast. In the name of ALLAH the most
Beneficent, the most Merciful. First of all, thanks be to ALLAH ALMIGTY who blessed us in
the whole course of study and we were able to complete the final year project.
Secondly, we take this opportunity to express our profound gratitude and deep regards
to our advisors DR. MUHAMMAD SAJID KAMRAN and MISS ANUM ABBAS for their
exemplary and extra ordinary guidance, monitoring and constant encouragement throughout
whole project work. We are much obliged that they gave us the opportunity to do research in
the field of Magnetic Refrigeration. It was quite an innovative idea that was accomplished in
fabricating up the Model through his entire support. The blessing, help and guidance given by
them time to time shall carry us a long way in the journey of life on which we are about to
remark.
Furthermore, we wish to express our deepest and profound respect to DR. NASIR
HAYYAT, head of Mechanical Department, University of Engineering and Technology, Lahore
whose contribution also lasted greatly in the execution of our prototype.

5. 5
Abstract
Magnetic refrigeration is considered as more reliable and sustainable source to generate
cooling and effect in the working fluid using hysteresis effect. Magnetically soft material with
less hysteresis loop area has been recommended for this project. Gadolinium is not only
magnetically soft material but also readily available. The magnetization of the gadolinium
material i.e. alignment of the atomic domains in phase with externally applied radial magnetic
field i.e. uniform throughout in the start, results in raising the temperature of the material ad at
that particular stage the working fluid at low temperature is passed through the materials
resulting in increase in the temperature of the working fluid. This project is based on direct heat
transfer between Gadolinium material and the working fluid. Since the project has been
prototyped on a small scale, direct heat transfer is preferred. On large scale heating and cooling
effect with certain storing factor, heat exchangers are also preferable. Gadolinium alloys with
different proportions of Gd and even in form of Gd wires was used to generate cooling and
heating effects of about 0.4 K / T.
In order to produce the cooling effect, Gadolinium has been demagnetized by moving it
out of the externally applied magnetic field. Due to less hysteresis loop area and controlled
reciprocating motion of the mobile material, the aligned domains get de-organized and the
amount of energy to overcome the lattice energies has been taken from the domains itself and
temperature get reduced. The University of California performed the similar effect using Gd
wires with results of 5.2 K / T.

6. 6
The driving motor speed was adjusted and the radial magnetic field of 0.8 T has been
applied. The mass flow rate of the water was controlled by the plunger. Powdered Gadolinium
material was placed in the acrylic tube. It was made to reciprocate with frequency. The
temperature difference were observed from 0.42 K / T to 3.64 K / T. The fluctuations in the
results were mainly due to heat rejection to atmosphere due to improper insulation of whole
apparatus.

7. 7
Table of Contents
Chapter 1. Introduction ............................................................................................................... 11
1. Background Literature............................................................................................................... 11
1.1 Thermodynamic Cycles ..................................................................................................... 12
1.1.1 Magnetic Carnot Cycle............................................................................................... 13
1.1.2 Magnetic Ericsson Cycle............................................................................................ 14
1.1.3 Magnetic Brayton Cycle............................................................................................. 15
1.1.4 Active Magnetic Regeneration (AMR) Cycle ............................................................. 17
1.2 Magnetic Refrigeration ...................................................................................................... 19
1.2.1 Stages involved in AMR Cycle................................................................................... 19
1.2.2 Main components of a magnetic regenerator............................................................... 20
1.2.3 Properties of the working fluid ................................................................................... 20
1.2.3 Properties of the magneto-caloric material.................................................................. 20
1.2.4 Magnetic Refrigeration Cycle..................................................................................... 21
1.2.5 Advantages of Magnetic Refrigeration ....................................................................... 22
1.2.6 Disadvantages of Magnetic Refrigeration ................................................................... 23
1.3 Magneto caloric Effect....................................................................................................... 23
1.3.1 Refrigeration Capacity ............................................................................................... 26
1.3.2 Coefficient of refrigerant performance........................................................................ 27
Chapter 2. Background and Literature review.............................................................................. 28
2. Research approaches ................................................................................................................. 28
2.1 System Design................................................................................................................... 31

8. 8
2.2 Mechanical Losses............................................................................................................. 32
2.3 Pumping Losses................................................................................................................. 33
Chapter 3. Research Methodology............................................................................................... 34
3. Introduction........................................................................................................................... 34
3.1 Designing of Magnetic Refrigeration model............................................................................. 35
3.1.1 Regenerator ...................................................................................................................... 35
3.1.2 Magnet ............................................................................................................................. 36
3.1.3 Reciprocating Pump.......................................................................................................... 36
3.1.4 Ducting System ................................................................................................................ 36
3.1.5 Thermocouple Wires......................................................................................................... 37
3.2 Purposed Model....................................................................................................................... 37
3.3 Prototyping of Refrigeration model.................................................................................... 38
3.4 Experimental Setup............................................................................................................ 44
Chapter 4 Results and Discussion...................................................................................................... 50
4.1 Results .................................................................................................................................. 50
4.2 Discussion ......................................................................................................................... 52
7. References:................................................................................................................................ 54

9. 9
Fig. 1.1.1 T- S diagram of Magnetic Carnot cycle .................................................................14
Fig. 1.1.2 T- S diagram of Ericson Carnot cycle....................................................................14
Fig. 1.1.3 T- S diagram of Magnetic Brayton cycle ...............................................................14
Fig 1.1.4 T- S diagram of Active Magnetic Regenerative (AMR) cycle.................................17
Fig. 1.1.4 Active Magnetic Regenerative (AMR) cycle………………………………………19
Fig. 3 Flow chart Magnetic Refrigeration model system.......... Error! Bookmark not defined.
Fig. 3.2 Schematic Diagram of Design of Magnetic Refrigeration Model..............................38
Fig. 3.3.1 Crank Case Mechanism.........................................................................................39
Fig. 3.3.2 Piston Crank Mechanism.......................................................................................40
Fig. 3.3.3 Piston Cylinder Mechanism...................................................................................40
Fig. 3.3.4 Permanent Magnet ................................................................................................41
Fig. 3.3.5 Regenerator reciprocating into the magnet.............................................................42
Fig. 3.3.6 Slider Crank mechanism assembly into the Magnet...............................................42
Fig. 3.3.7 Arduino Systems installed.....................................................................................43
Fig. 3.4. Experimental Demonstration of the complete setup.................................................46
Fig. 3.4.1 Thermocouples, Analogue and Digital Thermometers ...........................................47
Fig. 3.4.2 Calibration of thermocouples into certain Ice ........................................................48
Fig. 3.4.3 Calibration of thermocouples into certain Hot water..............................................48
Fig. 3.4.4 Graphical Representation of calibrated values .......................................................49
Fig. 4.1.1 Experimental results between Temperature and Time............................................51
Fig. 4.1.2 Theoretical Results................................................................................................52

10. 10
NOMENCLATURE-
COP Coefficient of Performance
M Magnetic Flux Density
V field Volume of the region where magnet is created
V mag Volume of magnet
H c Coercive magnetic field strength (de-guassing)
Br Residual Magnetic Flux density
B max Magnetic Flux
T coef Temperature coefficient of Br
T max Maximum operating Temperature
T curie Curie temperature
V Input Motor Voltage
I Rated Current
P Power of Motor
T Torque
N Revolution per minute
D, d Diameter
F Applied force on the Gadolinium

11. 11
Chapter 1. Introduction
1. Background Literature
In modern era, the abrupt changes in the climate have been taking place on global scale. The
temperature of earth is keep on increasing day by day. All this is because of global warming i.e.
high concentration of CO2 and ozone depletion due to the presence of chloroflouro carbons in
the environment. The refrigeration plants based on conventional vapour-compression cycle are
the main cause of global warming.
With the passage of time, the demand for energy production, environment safety and
protection keep on increasing. It enforces to find out new refrigeration technologies and also the
improvement in the already present technologies. In this regard, many refrigeration prototypes
have been produced with different MCM materials and with different configurations.
Refrigeration is basically a process of heat extraction from matter. The matter may either be in
solid, liquid or gaseous form. Temperature get reduced by removing heat and increases on heat
addition. For cooling purposes, energy demand has increased by 2.3% globally [1]. At low
temperature and pressure, a refrigerant absorbs heat from a substance and then it moves to a
condenser where it rejects the heat it carried and ultimately, its temperature and pressure get
reduces. Although pressure reduction takes place after passing through the expansion valve.
Magnetic refrigeration is based on solid state cooling in which the cyclic change in the
magnetic field, causes adiabatic temperature change and isothermal entropy change in the
material.

12. 12
Magnetic refrigeration is based on Magneto-caloric effect, i.e. the temperature of the
ferromagnetic material rises, due to alignment of its domains when it is placed in an external
magnetic field under reversible adiabatic conditions. This effect is depicted by most of the rare
earth metals and their alloys which are present in Lanthanide Series of the Modern periodic
table. For example Gadolinium (Gd, Z = 64), Rhodium (Rh, Z = 45) and Lanthanum (La, Z =
57) etc. This effect is observed at peak when the material is kept at its Curie temperature. The
strength of MCE decreases as the material temperature varies from its Curie temperature.
Magnetic refrigeration is now one of the most commonly used refrigeration technology.
The constant temperature difference across the ends of the regenerator or between the hot
reservoir (source) and cold reservoir (sink) is built up and magnified up to 2 − 3 Kelvin/Tesla
mostly in case of Gadolinium at room temperature. There can be either passive (for thermal
storage) or active regenerators (for refrigerating purposes). As Gadolinium has Curie
temperature of 21℃ (294 K) so it shows peak magneto-caloric characteristics at this
temperature [2].
This cooling technology is almost 20 − 30% more efficient than conventional vapour
compression cooling.
1.1 Thermodynamic Cycles
In a complete thermodynamic cycle of the magnetic refrigeration, for better
understanding, there are few essential components of a magnetic refrigerator i.e. magneto-
caloric material, source for the magnetic field, heat exchangers (both hold and cold), regenerator
(for the transfer of heat) and the working fluid (can be gaseous or in liquid phase).

13. 13
There are basically a few magnetic refrigeration cycles,
1. Magnetic Carnot Cycle.
2. Magnetic Ericsson Cycle.
3. Magnetic Brayton Cycle.
4. Active Magnetic Regeneration (AMR) Cycle.
1.1.1 Magnetic Carnot Cycle
The magnetic Carnot cycle is an ideal cycle in magnetic refrigeration. Its efficiency is quite
large while operating between two different thermal conditions. The stages which are included
in Magnetic Carnot cycle are listed below;
 Adiabatic increase in the temperature.
 Isothermal heat transfer from MCE to the working fluid.
 Adiabatic decrease in temperature.
 Isothermal heat transfer from working fluid to MCE.
There are two adiabatic processes and two isothermal processes. The description of this
cycle is as, in stage 1, initially the temperature of the material increases from Tcold to Thot
adiabatically by exposing it to a magnetic field. In stage 2, the material is fully magnetized
isothermally by increasing the magnetic field intensity of the applied magnet from Ho to H1 and
it rejects the heat energy, it got while magnetizing to the working fluid. In stage 3, when the
magnet field is reduced the temperature of the material decreases adiabatically from Thot to
Tcold. In stage 4, the magnetic field is reduced from H1 to Ho and material get completely

14. 14
demagnetized, the heat energy is absorbed by the material from the working fluid isothermally
and in this way the cycle got completed.
Fig. 1.1.1 T- S diagram of Magnetic Carnot cycle
1.1.2 Magnetic Ericsson Cycle
The Magnetic Ericsson cycle is based on second law of thermodynamics and fulfill its basic
requirements i.e. proper transfer of heat between the source and the sink due to temperature span
with maximum efficiency. The stages, this cycle comprises are,
 Isothermal heat rejection.
 Reduction in temperature at constant magnetic field (Isofield process).
 Isothermal heat absorption.
 Rise in temperature at constant magnetic field (Isofield process).

15. 15
There are two isothermal and two isofield processes. The cycle can be explained as, in stage
1, when the material was getting magnetized isothermally, the amount of energy it got, was
rejected to the working fluid [3].
In stage 2, the temperature of the material decreases while staying under the influence of
the same magnetic field and its temperature decreases from Thot to Tcold. In stage 3, the magnetic
field is reduced on the material and it starts demagnetizing, during this extent, it starts absorbing
heat from the working fluid, isothermally and eventually in stage 4, due to this absorbed it, at
constant magnetic field its temperature increases from Tcold to Thot.
Fig. 1.1.2 T- S diagram of Magnetic Ericsson cycle
1.1.3 Magnetic Brayton Cycle
Magnetic Brayton cycle is quite similar to Ericsson cycle. The only difference lies where
the heat transfer in Ericsson cycle was isothermally, the heat transfer in Brayton cycle is isofield
i.e. there may be temperature variations involved.
The stages, this cycle contains are,

16. 16
 Adiabatically increase in temperature.
 Reduction in temperature at constant magnetic field (Isofield process).
 Adiabatically decrease in temperature.
 Rise in temperature at constant magnetic field (Isofield process).
The description of each stage is quite simple. In first stage, the temperature of the material
increases from T4 to T1 by applying the magnetic field on the material and material get
magnetized, adiabatically. In the second stage, the material was exposed to the working fluid at
low temperature, the heat was transferred to the working fluid at the constant magnetic field and
the temperature of the material get reduced from T1 to T2. In the third stage, the material was
completely demagnetized by removing the magnetic field, adiabatically, to which it was
exposed and the temperature of MCM further get reduced from T2 to T3. In the fourth stage, the
material when at quite low temperature is exposed to the high temperature working fluid from
which it absorbs heat energy at its temperature increases from T3 to T4 to complete the cycle [4].
Fig. 1.1.3 T- S diagram of Magnetic Brayton cycle

17. 17
1.1.4 Active Magnetic Regeneration (AMR) Cycle
AMR cycle is the fundamental refrigeration cycle operating at room temperature and
considered to be quite efficient after Carnot cycle. In this MCM, acts as both refrigerant and
also a regenerator. The main stages in this cycle are,
 Adiabatic magnetization.
 Isofield heat rejection.
 Adiabatic demagnetization.
 Isofield heat addition.
Fig 1.1.2 T- S diagram of Active Magnetic Regenerative (AMR) cycle
This cycle includes two isofield and two adiabatic processes. Initially, magneto-caloric
material was placed in contact with the heat exchangers present across it. The working fluid is
considered to be at Tcold. In stage 1, when the material get magnetized adiabatically, the

18. 18
temperature of the working fluids on both side increases i.e. on cold side, it becomes Tcold +
∆Tcold and on hotter side Thot + ∆Thot. In stage 2, the working fluid was allowed to flow through
MCM and after passing through the material (the fluid absorbs heat energy from the material),
its temperature Tcold + ∆Tcold to Thot + ∆Thot. The fluid then discharge the amount of heat
energy it gained to the sink through heat exchanger and its temperature get reduced to Thot
from Thot + ∆Thot. In stage 3, the material was demagnetized adiabatically and its temperature
get reduced. Owing to this there occurs fall in temperature on both sides of MCM i.e. on cold
side temperature becomes Tcold − ∆Tcold and on hotter end Thot − ∆Thot. [5]
In stage 4, the fluid present at the hotter end is allowed to flow through the material and
on reaching the cooler end, its temperature was found to be Tcold − ∆Tcold. The working fluid
then absorbs heat from the other heat exchanger and its temperature again becomes Tcold. In this
way, the cycle got completed. [6]
Fig. 1.1.4 Active Magnetic Regenerative (AMR) cycle

19. 19
1.2Magnetic Refrigeration
The Carnot Cycle is an ideal cycle while Ericsson cycle is not as such operational now-
a days because of its expenses regarding the generation of magnetic field i.e. to generate the
magnetic field up to 1.5 T, electromagnets are used. The usage of electromagnets makes its
usage uneconomical. So the only cycle which is now being used is Active Magnetic
Regenerative cycle i.e. Brayton cycle.
1.2.1 Stages involved in AMR Cycle
The stages involved in AMR cycle are;
1. Magnetization.
2. Cold blow.
3. Demagnetization.
4. Hot blow.
The first stage is associated with the rise in the temperature of MCM when exposed to
magnetic field intensity. In second stage, the fluid flows from the cold end of the regenerator to
the hot end. In third stage, the magnetic flux density decreases, and the material was
demagnetized. Consequently, the atoms in domains get distorted again and the temperature of
the material decreases. At the end of the cycle, the working fluid moves from the hot side of the
regenerator to the cold side.
The thermocouples installed across MCM measures the temperature difference. This
difference can be enhanced by using more than one MCM materials along its length with
material of low Curie temperature at cold end and of high Curie temperature at hot end. [7]

20. 20
1.2.2 Main components of a magnetic regenerator
The main constituents of a Magnetic Refrigerator are;
 AMR (Active Magnetic Regenerator acting as refrigerant and regenerator).
 Heat transfer fluid (that provides and accept heat from MCM e.g. water).
 Magnetic field source (that provides the magnetic field of desired strength).
 Heat exchanger (at hot end, to give out heat energy of the working fluid in the
atmosphere causing heating effect, at cold end, to take heat energy from atmosphere to
the working fluid causing cooling effect).
 Hydraulic system (that enforces the working fluid to move across MCM).
1.2.3 Properties of the working fluid
The major properties a working fluid must possess regarding the point of view of magnetic
refrigeration are given as;
 High thermal conductivity.
 High heat capacity.
 Low viscosity.
1.2.4 Properties of the magneto-caloric material
The properties of MCM are given below;
 It should have high Magneto-Caloric effect (High ∆Tadiabatic)
 High thermal conductivity.

21. 21
 Low heat capacity.
 Non-toxic.
 Corrosion resistant.
 High electrical resistance.
 Low environmental impact.
 Low manufacturing and production cost.
In AMR cycles, as the refrigerant is solid bases MCM and working fluid is water based so
it is quite environment friendly and does not inculcate the evolution of hazardous gases. The
absence of compressor is quite helpful in reducing the input power consumption to a reasonable
extent.
The parameters controlling the efficiency of AMR systems are;
 MCE of the material that should be large.
 Magnetic field source that should provide quite higher magnetic flux density.
1.2.5 Magnetic Refrigeration Cycle
The magnetic refrigeration cycle can be understood in a better way by firstly making
clear understanding about the general refrigeration cycle i.e. vapour compression cycle.

22. 22
Vapour Compression Cycle Magnetic Refrigeration Cycle
1. Compression of the gas (High P & T)
2. Extraction of heat from the gas
(High P & Low T)
3. Expansion of the gas (Low P & Low
T)
4. Addition of heat to the gas.
(Low P & High T)
1. MCM moves inside the magnetic
field
2. Extraction of the heat to the
working fluid
3. MCM moves out of the magnetic
field
4. Addition of heat from the
working fluid
In case of vapour compression cycle, the heat transfer (heat addition and heat rejection)
is very fast. But the rate is quite slow in the solid state cooling. This problem can be overcome
to some extent by using porous MCM [8].
1.2.6 Advantages of Magnetic Refrigeration
The main advantages of Magnetic refrigeration are following;
 It does not use conventional refrigerants so not a cause of CFCs
 It does not use compressor so it is noiseless and power saving technology.
 As MCE is reversible process so the efficiency of this system is quite high about 20 −
30% more than VCR.
 Simplicity in its design is quite encouraging.
 Its maintenance cost is quite small.

23. 23
1.2.7 Disadvantages of Magnetic Refrigeration
The disadvantages associated with this technology are given below;
 It requires proper distant separation and insulation of the electric and electronic
components present near the magnetic field source.
 To vary the magnetic field with proper time intervals, electromagnets are used but they
are quite expensive.
 The temperature differences achieved are limited.
 Highly precise machines are used while controlling the moving parts of the system either
regenerator or the magnet.
1.3 Magneto caloric Effect
The MCE was introduced by German Physicist Emil Warburg (1881). Using the same
principle, Tesla (1892) tried to run a heat engine but could not make success. Giauque and
MacDougall (1933), used the same principle successfully for the liquefaction of H2 and He gas.
Magnetic caloric effect is based on reversible variation in the temperature of a ferromagnetic
substance when it is exposed to a varying magnetic field intensity. The field change that occurs
adiabatically (in magnetic refrigeration) is just like adiabatically pressure variations on the gas
(in vapour compression refrigeration). [9]
The variation in the internal energy of the MCM can be given as,
dU = Hdm (1.3.1)

24. 24
Where, dU is the differential change in internal energy, H is the Magnetic field intensity and dm
is the differential change in the magnetization. It is a process in which the magneto caloric
material, thermally quite sensitive to the varying magnetic field i.e. magnetic flux, got change
in its entropy isothermally or change in its temperature reversible adiabatically (isentropically).
The materials that can show magneto caloric effect are either pure magnetic elements or
solid alloys of 4f (Cerium, Neodmium, Promethium, Gadolinium etc), La based
compounds (La1−xMx, M = Na, Ag etc) and Manganites (MnO3).
Although Gd, was used in Magnetic refrigeration for a long time because of its tendency
to bring large entropy change in it near room temperature i.e. ∆SM = 10.2
J
kg.K
with ∆H = 5 T.
But owing to its high oxidation potential and high cost, it can’t be used on commercial scale.
When a magneto caloric material is exposed to externally applied magnetic field, the magnetic
force acting on the atoms in the domains of the material does work in aligning the atoms in the
domains and bringing them in the ordered state. Before exposing to the magnetic field, the atoms
were disturbed and at unstable state, they carry large amount of energy. But when they achieved
stable state, there energy get reduced, thus the amount of energy released increases the
temperature of the material and material is said to be magnetized. In this situation it heats up the
working fluid [10].
Within a narrow range of temperature, when the magnetic field is applied moderately,
MCE varies directly and linearly and when the temperature is above the Curie temperature,
MCE decreases. At higher magnetic field intensity, MCE increases exponentially with
temperature but within the Curie temperature of the material.

25. 25
When the magnetic field is removed, the atoms again start distorting i.e. transition from low
energy level to high energy level. The material requires energy for this purpose and that energy
it gets by absorbing heat energy from the working fluid. Thus it causes cooling of the working
fluid.
Now considering a quasi-static process, and applying energy conservation principle,
dU = dQ + (−dWmechanical) + dWmagnetization (1.3.2)
Where, dU is the differential change in internal energy, dQ is the differential of heat flux. T dS
dW mechanical is the differential amount of mechanical work done, pdV is pressure and v is the
volume, Dw magnetization is the work done by the magnet.
The total temperature change can easily be calculated by,
∆Tad = ∫ dT
T2
T1
= − ∫ μo
T
Cp,H
[μo (
∂m
∂T
)
p,H
] dH
H2
H1
(1.3.3)
And ultimately, the Magneto caloric effectiveness (measures reversible change in the
temperature with variations in magnetic field intensity in an adiabatic process) can be calculated
as,
MCE = ∆Tad = ∫ dT
T2
T1
= − ∫ μo
T
Cp,H
[μo (
∂m
∂T
)
p,H
] dH
H2
H1
(1.3.4)
Ultimately, the magneto caloric magnitudes are given as,
∆SM(T,∆H) = [SH2
− SH1
]
T
(1.3.5)
∆Tad(T, ∆H) = [TH2
− TH1
]
S
(1.3.6)

26. 26
The magneto-caloric materials during refrigeration cycle may undergo either FOPT
(First Order Phase Transition) of SOPT (Second Order Phase Transition). In FOPT, there is
smooth and continuous entropy change between magnetization and demagnetization. While in
SOPT, there is sharp change in entropy over a wide range of temperature during magnetization
and demagnetization.
Although the MCM showing FOPT, produce large Magneto Caloric effect, but during
the transitions, the lattice structure get disturbed which causes cracking in the material. Thus
these materials are not preferred for the long term usage. Therefore MCM having SOPT are
preferred and Gd belongs to this family.
Cooling capacity is actually the enthalpy difference at the cold end of the regenerator
and heat dissipation is the enthalpy differences at the hot end of the regenerator.
1.3.1 Refrigeration Capacity
It is the measure of amount of heat energy that is transferred between the hot and cold
reservoirs. It is also termed as relative cooling power. [9]
RC = ∫ ∆SM(T, ∆H)dT
Thot
Tcold
(1.3.1)
Where, T cold is Temperature of the cold reservoir and Thot is the Temperature of the hot
reservoir

27. 27
1.3.2 Coefficient of refrigerant performance
The comparison of the work energies (net-work and positive work) on the working fluid
in a reversible process is called coefficient of refrigerant performance. It can also be defined as,
CRP =
Refrigerant capacity
Magnetic work performed
In adiabatic conditions,
Magnetic entropy change + Lattice entropy change = 0
∆SM + ∆SLattice = 0
∆SM = −∆SLattice (1.3.2)
If there is positive change in ∆SM there must be a negative change in ∆SLattice to compensate it.
As a result, ∆Tadiabatic takes place in the material.
∆Tadiabatic = −
∆SM
CP
=
∆SLattice
CP
. (1.3.3)
Note that with increase in the strength of externally applied magnetic field, ∆Tadiabatic decreases
gradually.

28. 28
Chapter 2. Background and Literature review
2. Research approaches
The very first time in the history, Warburg in 1881 observed MCE in the pieces of iron when
they were exposed to externally varying magnetic field. Vuarnoz and Kawanami studied the
thermal characteristic curves by using Gd wires as active magnetic regenerator. Weiss and
Pickard made researches and studied the magneto-caloric effect in Nickel at its curie
temperature (627 K) and found it to be 0.467 K/T. [11]
Monfared, Palm, and Lei et al. by using layered bed regenerators of GdxTb1−x alloys,
concluded that instead of using single material, layered and alloys materials are even more
efficient in refrigeration process with quite greater efficiency [12].
Yu et al proposed Gd and Gd alloys as MCM under different configurations like
spherical and flat plates. But it was observed that the resulting cooling capacity and the achieved
temperature difference is not as such that it can replace the vapour compression cycle. The root
causes are small variations in the magnetic field, produced by permanent magnet, i.e. 1.5 T,
small temperature difference i.e. 1.5 − 2 K/Tesla and large pressure drop ultimately increased
per unit cost of the refrigeration and made it even more expensive than the vapour compression
refrigeration.
A team from University of California, introduced the first device working on magnetic
refrigeration mechanism. As a MCM, ribbons of Gd were used and they achieved far better
results i.e. 5.26 K/T. Bahl et al made comparison between different working fluids in magnetic
refrigeration on the basis of heat transfer rate. The working fluids were Water – ethanol,

29. 29
Propylene glycol, Ethylene glycol and olive oil. It was inferred that the heat transfer rate is
maximum in Water – ethanol.
Barclay introduced MCM to generate heating and cooling effect and the heat is
transferred through the working fluid. Now on the basis of same working principle, the devices
are made to work at the room temperature which would be made by selecting such ferromagnetic
materials having Curie temperature quite close to the room temperature.
Tura and Rowe using superconducting rotary magnets and reciprocating flow of the
working fluid, achieved the temperature difference of 29 K. In 2014, Arnold made certain
amendments in the same model, and sustained the temperature difference across the MCM, of
about 33 K. In AMR technology, by using layers of La(Fe, Si)13, the cooling performance of
the cycle was increased upto a certain mark, but during continuous cycles of magnetization and
demagnetization, the material got fractures. Richard et al. used coatings of Gd and GdTb in the
layers of MCM to achieve the temperature difference of 20 K.
The active magnetic regenerator having 2 regenerator, with approximately 66 g of
gadolinium Gd and 70 g of Gd-Er in properly crushed form were placed in magnetic field of
5 T and a temperature difference across it was observed to be 8 K with COP = 0.64 under
thermal load of 35 W. Lozano et al. (2013) explored rotary magnetic regenerators by using
2.8 kg Gd in a concentric 1.24 T four-pole magnets, and attained the temperature difference of
16.8 K with COP = 0.69 under thermal load of 200 W.
In 2016 Paulo V. Trevizoli and Alan T. Nakashima used different porous matrix
geometries for making a performance assessment for an active magnetic regenerators. Three
different regenerator geometries i.e. parallel-plate, pin array and packed bed of spheres were

30. 30
fabricated having porosity between 0.36 and 0.37. It was observed after the performance
analysis that the parallel plates had poorest performance, while the packed bed of spheres had a
highest cooling capacity but also viscous losses. But the pin array showed a highest COP value
and second-law efficiency [13].
Dan Erikson in 2016 made a research on discovering the efficiency potential for and
active magnetic regenerator (AMR). An efficiency of 18% was obtained for a cooling load as
81.5 that resulted in a temperature span of about 15.5 K and a performance coefficient of about
3.6%. Moreover an upper efficiency of about 30% was obtained while considering all the
parasitic losses to be eliminated. Matheus S. Capovilla in 2016 made a performance evaluation
of a magnetic refrigeration system. Moulay Youssef El Hafidi in 2017 made a calculation on
MCE and relative cooling power using different materials in composite form at room
temperature. This targeted material gave higher RCP value within the range of 280-300K in the
magnetic refrigeration cycle of Ericson [7].
Kristina Navickaitie in 2017 made a comparison of experimental and numerical active
multi-layered magnetic refrigerator in which a temperature span of 20K was measured. Four
AMR varying up to 9 layered were used for the prediction of one dimension numerical model.
Tian Lei in April 2017 made a research on epoxy bonded regenerators at room
temperature in which the passive characterization and active testing was done on it for the
magnetic refrigeration process. Regenerators that are epoxy regenerated for both spherical and
irregular particles were developed for increasing the mechanical strength of AMR. A test
apparatus which passively characterizes the regenerators thus simulating the hydraulic working
in active magnetic refrigerators by using a liquid heat transfer fluid at low Reynolds numbers.

31. 31
JA Barclay made a research on the balancing of passive force for an active magnetic
regenerative liquefier for which a model was developed i.e. magneto static model and simulated
waveform of force were compared with experimental measurements [14]. Ondrej Kapusta and
Andriana Zelenakova studies the change of entropy and response that is caused by magneto
caloric by heat capacity measurement in magnetic nanoparticles. In a temperature range of 1.9
to 55 K under the magnetic field the magneto caloric effect was investigated for the nano-
particles with the help of heat capacity measurement. The Iso thermal magnetic entropy change
was obtained as 3.11J/K kg in a magnetic field of 0 to 9 T.
V Franco in 2018 made a research in refrigeration devices using magneto caloric effect
using different materials In which a comparison was made, the effects and techniques were
measured and possible improvements techniques in this method of refrigeration were done in
details [15].
C. Aprea in 2018 performed the energy performances and the numerical investigations
in an active magnetic regenerator using magneto caloric material in solid state. Gadolinium
material served as AMR and its behavior was investigated [16].
2.1 System Design
In designing a whole system for active magnetic refrigeration, we need to take into account
the technological issues that are associated with it. A few of them are mentioned below,
 Designing of source that can provide a strong magnetic field intensity in cyclic manners.
 Configuration of the regenerator either layered, porous or graded based on
requirements.

32. 32
 Optimized conditions for the whole process to run.
The active magnetic regenerator devices comprise of regenerator, a magnet and a flow
control device, the flow of working fluid can easily be controlled by using different crank radii.
The porous regenerator are used here to increase the heat transfer rate by increasing the surface
area in contact. Aluminum core (to make it corrosion resistant) with glass fibers is installed there
concentric with the permanent magnet. The permanent magnet is coaxial with the reciprocating
tube. The flow of heat energy was made properly unidirectional. The magnet is made up of
NdFeB material.
There is an air gap present between the housing of regenerator and the magnet. The magnet
is considered to be at ambient temperature T∞. But in regenerator, there is a radial temperature
gradient from TC to TH. The heat transfer in this complete system is by both conduction and
convection (free and forced). There is also a temperature gradient in the air gap which is present
between the regenerator and the inner surface of the magnet. For the sake of simplicity in the
results, the heat transfer taking place through convection is considered to be quite small through
the air gap.
The heat is transferred through convection between the working fluid while flowing through
the porous MCM. While designing a whole refrigeration system for higher value of COP
(Coefficient of Performance), the air gap between the regenerator and the magnet must be kept
approximately 1 mm. Because at higher values, the maximum cooling power will get reduced.
2.2 Mechanical Losses
The power produced by the motor is considered approximately equal to the power with
which the regenerator reciprocates in and out of the magnet but there are certain mechanical

33. 33
losses associated with it. The amount of energy get lost in the friction between the rails and the
slider, between the bearings and internal hysteresis losses in the winding of the motor while
rotating at slightly higher RPM.
2.3 Pumping Losses
There a pumping losses across the whole AMR system. Initially, these losses were not
taken into account but when we need to calculate the overall performance of the system, the
losses that occur across the needles, connecting tubes, improper fittings, valve control and flow
resistance must be taken into account at different flow rates which would be achieved by varying
crank radius.

34. 34
Chapter 3. Research Methodology
3. Introduction
The methodology adopted for our magnetic refrigeration system is given as below: -
1. Designing of Magnetic Refrigeration model
2. Prototyping of Refrigeration model
3. Experimental Setup
4. Calibration and Testing
5. Calculating and comparing the experimental and theoretical results
The Methodology includes all the series of steps that were adopted in the execution of the
Refrigeration system process. Initially, the requirement demands for the proposal of a model
that is based upon the theoretical model that works on some refrigeration cycle i.e. in our
Magnetic Refrigeration system the cycle is Active Magnetic Refrigeration cycle and based upon
that cycle the design of the system is made along with its systematic diagram. Then, it is
analyzed onto some software in order to check its feasibility and the data is collected for the
observation and calculations of the results.
After that prototyping step is done, in order to ensure that either our system is running
same as if the practical model is made. So for that the prototyping was done for our magnetic
refrigeration model and it was fabricated. Some of the components were imported so that a
complete setup could be made in a running conditions.
Further, then the model is assembled by coupling all of the components as per our system
design. And all the parts are joined properly so that they could in a proper working order.

35. 35
Then the fabricated experimental fabricated model is passed through the phase of testing.
The apparatus is calibrated with some other measuring instruments and is then tested so that all
of the parts are properly assembled and there is no flaw left behind.
Then, at last the model is passed through calculation and observation phase i.e. the data
is collected by running down the apparatus and series of values are obtained. Further, the values
are plotted and then compared with the theoretical data results. If the system results are same as
per the requirements then its fine however, if they negates the practical results then the
methodology cycle is again reviewed for ensuing the proper working of the system.
3.1 Designing of Magnetic Refrigeration model
Based upon the theoretical background study and a clear literature review, the model of
Magnetic Refrigeration Model was designed. The Active Magnetic Cycle was considered for
our magnetic refrigeration model design. Based upon this cycle, the required components that
were feasible for our design system of our refrigeration model were proposed onto the design
and the systematic diagram was made.
3.1.1 Regenerator
In the magnetic refrigeration system, there is a regenerator that encloses a refrigerating
material through which the cooling effect can be measured. The regenerator can be of any type
i.e. layered, porous or channel shaped that varies as per the model design and the requirements.

36. 36
3.1.2 Magnet
A permanent magnetic nearly of 1 Tesla (taken from the theoretical background study)
was used for the magnetization and demagnetization of the refrigerating material in the
regenerator.
3.1.3 Reciprocating Pump
Double acting reciprocating pump that is used to flow the working fluid inside the
periphery of the piping system. The basic function of this pump is to flow the working fluid
(water in our case) in both the directions of the regenerator. The piston plunger systems are
introduced that flow the fluid as per the required arranged mechanisms. Further, the Crank Case
Mechanism is used to hold up the regenerator in order to achieve its movements into the
permanent magnetic and out of the magnetic field. The slider crank case mechanism allows to
and fro motion in a proper systematic manner of the coupled regenerator (by a clamp) that
includes the refrigerating material.
3.1.4 Ducting System
Piping system are used for the flow of water (working fluid) in the whole refrigeration
system. The ducts were designed as per the system requirements and their diameters along with
length are suitably selected for the entire working system. Such that the flow of the water must
be in a proper flow rate within the periphery of the tubes.
Heat Exchangers as per the design were used for extracting up the heat form the working
fluid and making the system more efficient in the magnetic refrigeration system. Two heat

37. 37
exchangers installed at both the ends of regenerator so that when the working fluid enters at one
end of the regenerator and it enters the magnetic field for the magnetization, it make the fluid
hot by rising of the temperature. When it reaches the other end the fluid is comparatively colder
than the previous end which makes the one end of the refrigerant i.e. Gadolinium, to be hot and
the other end to be cold. The heat exchangers purpose is to exchange the amount of heat within
the fluids and to achieve the best possible temperature difference at both ends of the Gadolinium
material.
3.1.5 Thermocouple Wires
Thermocouples wires that are used for measuring up the temperature difference at the
two ends of regenerator. Their ends were plugged into the meshes in the regenerator tube as per
the design which were close to the refrigerating material for getting the unsurpassed
temperature. Finally, the Arduino System for controlling mechanism of the fluid movement into
the whole system and the regenerator movement (through the to and fro motion of Slider Crank)
into and out of the magnetic field.
3.2 Purposed Model
The proposed model of the system is given as below,
i. Regenerator (Layered/ Porous/ Channel)
ii. 1 Tesla Magnet
iii. Crank Case Mechanism
iv. Heat Exchangers

38. 38
v. Piping System
vi. Fluid Reservoirs
vii. Double acting Reciprocating Pump
viii. Thermocouples
Fig. 3.2 Schematic Diagram of Design of Magnetic Refrigeration Model [17] [18]
3.3 Prototyping of Refrigeration model
The analysis of the design the calculations were performed by running under the
theoretical parameters and the results were taken by making keen observations from the data
that was analyzed. After that the whole model was made practically by fabricating the individual
components parts by parts and then assembled into the magnetic system. Below here is the
procedure by which it is shown that how the individual parts were made into the practical model.
Initially, the Slider Crank Case system was fabricated. The Crank of certain dimensional

39. 39
parameters having a connecting rod attached to its periphery and then to the slider case. The
motor was of certain was installed into the system and upon which the crank was attached.
Fig. 3.3.1 Crank Case Mechanism
The Double Acting Reciprocating pump was installed. For this a step motor was taken
and a crank was drilled on its center position. Then the crank was fixed on the step motor for
having number of revolutions. The Crank surface was further drilled at different positions from
the center for the use of variable flow rate in the refrigeration system. Further then, a crank rod
was fixed with a bolt onto the surface of crank at one end and its other end was fixed with the
slider case mechanism for having a reciprocating motion on its mean position.

40. 40
Fig. 3.3.2. Piston Crank Mechanism
Piston Cylinders were installed in the system. The cylindrical tubes were installed in the
system having piston mechanism in it for making the flow of working fluid into the pipes. The
other end of the crank rod has two branches (pistons) i.e. at the right side and the other one at
the left side thus entering into the cylinders with their reciprocating motion to and fro.
Fig. 3.3.3 Piston Cylinder Mechanism

41. 41
Permanent magnet nearly of 1 Tesla was installed in the system. The magnet was
rounded in shape and has a slot inside it for the entry of regenerator into it. The magnet functions
as in the providing of magnetic flux to the material inside the regenerator for the cooling effect
mechanism.
Fig. 3.3.4. Permanent Magnet (Top and Side view)
Regenerator having an enclosure of acrylic tube has a Gadolinium material present
inside it. The tube has two open ends which are closed by the nuts. These nuts has two drilled
holes i.e. one for the passage of working fluid and the other for the thermocouple wire. The
regenerator has two meshes that bounds the movement of refrigerating material inside an acrylic
tube. These meshes had many number of holes that lets the water to pass through them.

42. 42
Fig. 3.3.5. Regenerator reciprocating into the magnet
Duct system is installed into the magnetic refrigerating system. Two pipes are attached
as one their end with the head of the cylinders of the piston (reciprocating pump) while the other
end is inserted within the both ends of acrylic tubes.
Thermocouples for the measuring of Temperature difference were installed in the system. The
temperature was displayed onto the Omega which was further connected to the Laptop for
getting up the graphical values. The leads of thermocouples ends were inserted in the regenerator
ends near the placement of refrigerating material.
Fig. 3.3.6 Slider Crank mechanism assembly into the Magnet

43. 43
Arduino Systems were installed for the controlling mechanism of working fluid inside
the ducts as well as controlling the timing of motor for getting the controlled movement of
regenerator inside the permanent magnet in a systematic way. So that all the system can operate
completely on Active Magnetic Regenerative Cycle.
Fig. 3.3.7 Arduino Systems installed
The diameters, lengths and all related dimensions were calculated and after that they were
fabricated accordingly. Each of the parts were either brought or fabricated. Specifications of
individual components are listed in the table as below: -

44. 44
Serial
Number
Parts Specifications
1 Double
reciprocating pump
Diameter of flywheel= 6.25 inch
Length of Connecting rod= 12 inch
2 Magnet Length of magnet= 4 inch
Diameter of magnet including test tube
diameter= 2.5 inch
3 Small motor Diameter of motor= 4.5 inch
Length of connecting rod= 9.25 inch
4 Test tube Length of test tube= 8.25 inch
Diameter of test tube= 1 inch
5 Ducting system Length of pipe using for flow= 5 ft. 3 inches
Diameter of mesh= 0.85 inch
6 Battery Voltage = 12V
Timing = 34AH@ 20HR
3.4 Experimental Setup
After the fabrication of all individual components, all the parts were assembled as per
our designed model for ensuring the running of system. Firstly, the slider crank mechanism was
fitted onto the board and its alignments were checked for its proper orientation. The slider crank
mechanism was connected to the Motor. The refrigerating material (Gadolinium) was enclosed
inside the regenerator and meshes were fixed at its both ends for the material to be fixed in its

45. 45
position. The ends of regenerator were closed by the push fits which had openings at the both
the ends for the entry and exiting of the working fluid. The push fits also contained small drilled
holes so that the Thermocouples wires can be inserted into them for the conduction of the
Temperature at both ends of the material. The regenerator is further clamped with the slider
mechanism so that it can have the to and fro motion at its mean position into and out of the
Permanent Magnet. The magnet having magnetic field of 1 tesla was fabricated to have hole
inside it of certain diameter for the motion of the regenerator into it.
Moreover, a second motor was installed at the separate space again for achieving the
reciprocating movement for the Piston cylinder mechanism. The rpms of the motor were
adjusted in a manner that the pistons movement was in synchronized with the rotation of slider
crank mechanism. These motors are governed by the battery. So that the working fluid can be
that is carried out in the ducting systems according to the design specifications. When the water
is pumped by the reciprocating motion of the piston mechanisms from one side into the one end
of the regenerator, it passes through the whole acrylic tube till reaches the other end of the tube.
And finally enters the other cylinder. Here, the water (working fluid) is again pumped by the
piston from that cylinder and is sent back to the regenerator and hence, back to the first piston
cylinder. During this motion of the working fluid, the motion of regenerator is synchronized
into and out of the magnetic field.
The Arduino systems were also installed for ensuring the proper movements of the
cylinders. The timing of the Arduino were adjusted as per our design requirements i.e. when the
slider of the crank hits with the Arduino by having a reciprocating motion making the piston of
the cylinder to flow the water into the regenerator at the same time the regenerator gets strike
with an another controlling device for the slider to stop for the time being until the working fluid

46. 46
gets to other end of the piston. Then the first slider again strike the push button for having the
fluid flow in the backwards direction.
The attached thermocouple wires at the both ends of the regenerative material helps in
taking the readings of Temperature. Two thermocouple wires displayed the Temperature rise
and fall at each end of the gadolinium which was further displayed in the screen of omega. The
Omega device was connected to the Laptop for achieving the values in the Tabular form. The
values are recorded for the time limit we want to set for and further from which plots can be
made onto the Excel sheet.
The whole apparatus in the assembled form comprising of all individual fabricated parts are
shown in the figure below: -
Fig. 3.4.1 Experimental Demonstration of the complete setup
3.4 Calibration and Testing

47. 47
After the assembly of all the features in the magnetic refrigerator system the next phase
that started was the calibration and Testing before the operation of the system. As per the defined
definition of Calibration process in the field of technology and metrology is the comparison of
the measured values. So in our refrigerating system the measuring instruments were the
Thermocouples wires for recording down the Temperature and then displaying in the computer.
The values are further imported into the Excel Sheet.
Thermocouples were calibrated using some other standards temperature measuring
devices. For that Digital and Analogue Thermometers were used. Then by using different
mediums the values of temperatures were measured. The Thermocouples wires, digital
thermometer rod and Analogue Thermometer tip were inserted in the mediums like, Ice, Hot
Water, Normal Body Temperature, Normal air Temperature and Normal water Temperature.
Multiples readings were taken under account for the purpose of comparison to be used for the
correct values. Following are the images for the calibration process that was adopted during the
temperature measurement in three of the different mediums as given below:
Fig. 3.4.1 Thermocouples, Analogue and Digital Thermometers

48. 48
Fig. 3.4.2 Calibration of thermocouples into certain Ice
Fig. 3.4.3 Calibration of thermocouples into certain Hot water
The results obtained by the calibration process by using three different measuring
instruments are given as below in the table. The temperatures were recorded in degree Celsius.
For Atmospheric Temperature the Thermocouples, Analogue and Digital Thermometers gave
the readings as 32.8o
C, 32.2o
C and 32.5o
C. For the Normal water the temperatures came out to
be as 31.7o
C, 32o
C and 34.1o
C by using same measuring instruments in the same order. Moving

49. 49
towards normal body temperature that gave results as 36.5, 36.2 and 36.3o
C. The Freeze ice
gave the temperature scale readings as 0.2, 0.3 and 0o
C. Finally after noting down the reading
by using Thermocouples, Analogue Thermometers and Digital Thermometers the Temperatures
came out to be as 81.3, 81.6 and 81.4o
C respectively.
The bar graphs are plotted between Temperature in Celsius and Mediums against the
values of the experimental results as obtained in the table above. The graph is shown as below
the table which is clearly depicting the results. The Red color bar is showing the Digital
Thermometer readings, The Yellow color bar is showing the values for Analogue Thermometer
and Green color bar is showing for the Thermocouples readings.
Fig. 3.4.4 Graphical Representation of calibrated values
32.5 31.4 36.3 0
81.4
32.2 32 36.2 0.3
81.6
32.8 31.7 36.5 0.2
81.3
ATMOSPHERIC
TEMPERATURE
NORMAL
WATER
TEMPERATURE
NORMAL BODY
TEMPERATURE
FREEZE ICE HOT WATER
Temperature(oC)
Medium
Medium vs Digital Thermometer Medium Vs Analogye Thermometer
Medium vs Thermocouples

50. 50
Chapter 4 Results and Discussion
4.1 Results
After the successful calibration of Thermocouples wires and proper assembly of all the
individual parts in a systematic manner, the next step was the running of the apparatus in order
to get the experimental values. The apparatus needed to run for certain flow rate for our better
accurate results. When the apparatus (motor more specifically) is given certain number of
revolution per minute RPM then it creates a variation in the Temperature difference at the both
ends. Similarly, by varying the diameters of the crank case (on which the slider is attached), the
flow rate of the working fluid can also be varied.
The scatter with smooth lines graph is obtained between two axis as Temperature in
Kelvin and Time in seconds. The apparatus ran for a period of 3 minutes time and the variations
in Temperature were recorded in the table. The Thermocouples wires were attached similarly as
was in the design model of Magnetic Refrigeration. Initially, the temperature shown as by the
Omega was 300.5 K equal to 25.5o
C. When the apparatus was started to run the temperature
varied based upon the Active Magnetic Caloric effect. As the regenerator came into the magnetic
field, the material i.e. Gadolinium got magnetized and the temperature of material increased.
This increase in temperature was displayed by the Thermocouple. The Temperature at this end
gradually rose from 300.5 K to 302.5 K at maximum.
Similarly, when the regenerator came out of the Magnetic Field the cooling effect is
produced by the Magnetic Caloric effect and Temperature gets dropped that is again measured
by the Thermocouple. So by the principle of AMC, one end of the regenerator got hotter and

51. 51
the other end of the regenerator got colder enough to provide sufficient temperature difference
that can further be applied for the applications. After the running of the apparatus for a period
of 3 minutes the Temperature difference that was achieved, came out to be 3.5 K at maximum.
Here, by running the apparatus, the graph for our experimentation values is as obtained
as below: -
Fig. 4.1.1 Experimental results between Temperature and Time
The theoretical graph between the Temperature T which is represented in Kelvin and
Time t in second is plotted as per shown in the results. Here, the values obtained from the data
observed after running the apparatus, are represented by the red and blue lines. The
Thermocouple wires were attached at the both ends of refrigerating material bounded by the
meshes at the both ends inside the regenerator. The obtained Temperature started from the 293
K which fluctuated as the apparatus was set to the working condition. The Temperature at the
299
299.5
300
300.5
301
301.5
302
302.5
303
303.5
0 50 100 150 200
Temperature(K)
Time (s)
TEMPERATURE VS TIME
Hot End Cold End Log. (Hot End ) Log. (Cold End)

52. 52
hotter end rose up to 300 K at maximum while the temperature at the colder end came out to be
equal to 287 K thus giving a Temperature difference of 13 K. Whole of the graphical
representation is shown as below:
Fig. 4.1.2 Theoretical Results [17]
4.2 Discussion
The mass flow rate of the working fluid and the heat transfer fluids have been found the
critical parameter in the generation of heating and cooling effect. The project has been mainly
concerned with the direct heat transfer from Gd to the working fluid. The heat transfer fluid
related with environmental issues have been excluded. The direct heat transfer was related with
convection heat transfer between the fluid and the hot or cold contacting surface that is
magnetically soft in nature. Convection heat transfer was controlled by the plungers. Greater the
mass flow rate, for the particular temperature difference the heat transfer rate of the working
substance also got increased. The maximum mass flow rate was adjusted and the heat transfer
was found maximum.

53. 53
Due to improper insulation the heat transfer from Gd to working substance plus, to the
atmosphere results in heat energy. The amount of energy that has been provided to the
atmosphere. The increase in the heat transfer to the atmosphere for certain temperature gradient,
was compensated with increment in the mass flow rate of the working substance. Proper
covering and isolation form the atmosphere will reduce the heat loss and the temperature
difference related with certain lower mass flow rate, was observed. The maximum temperature
difference across the magnetic refrigerator was observed to 3.46 K / T. For every rise in the
magnetic flux density on the material, the maximum temperature difference of 0.5 K was
observed.

54. 54
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11. Warburg, W., and the connection between magnetism and a. heat, Who discovered the
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Wu e, Hua Sheng Wang a,* Numerical investigation of room temperature magnetic
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Gui Chen c, Hua Sheng Wang b, Performance optimisation of room temperature magnetic
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