Magnetism and Temperature Essay

Submitted By nikhilkoli
Words: 8450
Pages: 34
Open Document
i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 3 5 ( 2 0 1 2 ) 1 0 4 3 e1 0 5 4

Available online at www.sciencedirect.com

w w w . i i fi i r . o r g

journal homepage: www.elsevier.com/locate/ijrefrig

Assessment of demagnetization phenomena in the performance of an active magnetic regenerator
Paulo V. Trevizoli, Jader R. Barbosa Jr.*, Pablo A. Oliveira, Fa´bio C. Canesin,
Roge´rio T.S. Ferreira
POLO Research Laboratories for Emerging Technologies in Cooling and Thermophysics, Department of Mechanical Engineering,
Federal University of Santa Catarina (UFSC), Floriano´polis, SC 88040900, Brazil

article info

abstract

Article history:

The primary objective of this paper is to quantify the impact of the internal magnetic field

Received 28 January 2011

and reversibility of the magnetocaloric effect on the numerical evaluation of the thermal

Received in revised form

performance of a parallel-plate active magnetic regenerator. To this end, direct measure-

24 November 2011

ments of the adiabatic temperature change of commercial-grade gadolinium samples were

Accepted 13 February 2012

carried out for an applied field change of 1.65 Æ 0.03 T (for both magnetization and

Available online 21 February 2012

demagnetization) and temperatures between 283 and 303 K. The tests were carried out in a specially constructed apparatus and the results were in good agreement with the liter-

Keywords:

ature. The data were incorporated into a mathematical model for solving the fluid flow and

Regenerator

conjugated heat transfer in the parallel-plate regenerator. It was found that if demagne-

Magnetic refrigerator

tization phenomena (i.e., the demagnetization factor and the reversibility of the magne-

Gadolinium

tocaloric effect) are not take properly into account, the thermal performance of the

Adiabatic magnetization

regenerator can be severely over-predicted.
ª 2012 Elsevier Ltd and IIR. All rights reserved.

Adiabatic demagnetization

Evaluation des phe´nome´nes de de´saimantation sur la performance d’un re´ge´ne´rateur actif magne´tique
Mots cle´s : Re´ge´ne´rateur ; Re´frige´rateur magne´tique ; Gadolinium ; Aimantation adiabatique ; De´saimantation adiabatique

1.

Introduction

The magnetocaloric effect (MCE) is the reversible temperature variation of a magnetic material subjected to a changing magnetic field. Some classes of magnetic materials exhibit a significant MCE at the vicinity of room temperature, which makes them potential candidates for utilization as refrigerants in systems based on active magnetic regeneration cycles

(Tishin and Spichkin, 2003; Gschneidner et al., 2005; Bru¨ck et al., 2008). To date, the most widely examined of such materials is gadolinium (Gd), which has an MCE around
3.5e4 K T for a magnetic field change of 1 T, at its magnetic transition (Curie) temperature (w293 K).
The MCE can be described by the magnetic entropy variation (DSM) or by the adiabatic temperature change (DTad), which can be quantified indirectly from the measurements of

* Corresponding author. Tel./fax: þ55 48 3234 5166.
E-mail address: jrb@polo.ufsc.br (J.R. Barbosa).
0140-7007/$ e see front matter ª 2012 Elsevier Ltd and IIR. All rights reserved. doi:10.1016/j.ijrefrig.2012.02.003 1044

i n t e r n a t i o n a l j o u r n a l o f r e f r i g e r a t i o n 3 5 ( 2 0 1 2 ) 1 0 4 3 e1 0 5 4

TC w Nomenclature
Roman letters
[
Characteristic dimension [mm] f Frequency [Hz]
H
Magnetic field [T]
L
Sample length [mm]
M
Magnetization [emu gÀ1]
_
m
Mass flow rate [kg hÀ1]
Demagnetization factor [-]
ND
t
Sample thickness [mm]
T
Temperature [K]

Sub and
1
2 appl cold demag hot mag res

magnetization and specific heat capacity as a function of temperature (Pecharsky and Gschneidner, 1999; Pecharsky et al., 2001). DTad can also be measured directly by means of temperature detectors, such as thermocouples or infrared thermography (Christensen et al., 2010). By definition, DTad is the difference between the
Show More

Related Documents: Magnetism and Temperature Essay

Oils And Magnets: Opposites Attract

Magnetism is a characteristic of electromagnetism, in fact, it is the force that allows objects with magnetic fields to attract or repeal other objects. Electromagnetism being the force that directs how atoms and molecules interact. Additionally, it embodies as electricity or magnetism. Ultimately, it is the force that drives most of the world, for instance it is the force that allows the light to rise or for computers to operate and so much more. Obviously, magnetism is the force in…

Words 1537 - Pages 7

Animal Magnetism Affect The Regeneration Of An Earthworm

Animal Magnetism is when any living organism characterized by voluntary movement is affected by a strong magnetic field. Magnetism is one of the most powerful forces, but it is poorly understood. In this case neodymium magnets will affect the regeneration and biological function of the lumbricus. When an earthworm's body is cut off into pieces, it will usually regenerate. Earthworms will usually regenerate most of their rear segments, meaning under their abdominal area. The front section of an earthworm's…

Words 581 - Pages 3

“What Is Hypnosis?” Describe the Psychological and Physical Aspects of Hypnosis and Discuss the Role of Relaxation in Hypnotherapy. Essay

and inanimate objects that he called animal magnetism. In 1774, Franz Mesmer made her patient swallow something that contained iron and then attached magnets to various parts of her body. Her feedback was that she felt streams of fluid running through her body. For several hours, she was cured from her symptoms. Mesmer did not believe that the magnets had cured his patient on their own. He believed her situation had benefited from animal magnetism also. He stopped using magnets as part of his…

Words 1850 - Pages 8

Essay Fervent Core

Frias March 1st (The Core) “Movie” The Fervent Core The movie, The Core, shows an impossible mission in which six specialists decide to make a trip into the core of the Earth, willing to save humanity. The Earth's core has stopped spinning. The magnetism of the Earth was deteriorating and directly affecting the Earth’s protection from the Sun. Birds began acting crazy, powerful thunderstorms were occurring, and the world was literally stopping. People were frequently and simultaneously dying at the…

Words 328 - Pages 2

Energy and Stored Energy Essay

Science of Everything 2 Last Class 3 Today: Energy (Chapter 2) • Contrast the general properties of the different forms of energy. • Articulate the difference and relation between Energy, Power and Work. • Compare the concepts of Temperature with Heat. • Examine the implications of the laws of Thermodynamics in our lives. • Explore possible sources of energy for our society. 4 Energy • Doing anything requires energy • Everyday life “energy” = exuberance • Physics takes…

Words 982 - Pages 4

Density And Other Physical Properties

Sixth Grade Science Density and other Physical Properties TEKS (6) Matter and energy. The student knows matter has physical properties that can be used for classification. The student is expected to: (6B) Calculate density to identify an unknown substance. Supporting Standard PRIOR KNOWLEDGE MASS: the amount of matter, and is not affected by the force of gravity Use appropriate units, grams (g) and practice using triple beam balance Measure the mass of 1 mL of water (it will…

Words 1783 - Pages 8

How Did Foucault Contribute To Science

blood so he instead focused on other branches of science. Because in the mid 19th century scientists did not usually specialize in just one narrow speciality, Foucault studied many different branches of science. He made discoveries in electricity, magnetism, chemistry, optics, and astronomy. But it was only until he developed his experiment with a pendulum that he was able to achieve worldwide success and renown.…

Words 807 - Pages 4

Kiara Fornaris Ad Essay Revised

purchase this brand of Deodorant because of all the beauty and security the commercial displays, thus using pathos to attract women to using their product. Imagine yourself walking into a room and everyone you pass by is suddenly drawn to you. The temperature seems to rise, and all eyes are on you. That's how men wearing Axe Body spray feel. The commercial makes it seem as if men that wear Axe body spray are more masculine and macho than those who don’t wear it. Men, having very sensitive egos want to…

Words 1014 - Pages 5

A Song Essay

[CURRENT] [WET CELL BATTERY] [CIRCUITS] [SERIES] [PARALLEL] [DIAGRAMS] [SYMBOLS] [FUNCTIONS] [FORMULAS] [KIRCHOFF – VOLTAGE/CURRENT] [OHM’S LAW – RESISTANCE] [POWER] [COST OF ELECTRICITY] [RESISTORS] [ANALYZING] [MAGNETISM] [CHARACTERISTICS] [ELECTROMAGNETISM] Static Electricity: -In order to create a charge, friction is required -Protons do not move(except in certain circumstances) -Electrons can move between objects -Charges collect on…

Words 1421 - Pages 6

Geography AQA Tetonics A Level Key Definitions Essay

Geography Key Words (Tectonics) Palaeomagnetism – Palaeomagnetism is the branch of geophysics concerned with the magnetism in rocks that was induced by the earth's magnetic field at the time of their formation. Convection Currents – As semi-molten rock in the mantle is heated it becomes less dense than its surroundings and rises. As it reaches the crust above, it spreads out carrying the plates above with it. As the semi-molten rock then cools, it gradually sinks back down to be re-heated.…

Words 1113 - Pages 5