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
Related Documents: Magnetism and Temperature 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…
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…
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…
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…
[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…
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…
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.…
Geology Test 1 Study Guide Chapter 1: Introduction Key terms * Asthenosphere – A subdivision of the mantle situated below the lithosphere. This zone of weak material exists below a depth of about 100 km and in some regions extends as deep as 700 km. The rock within this zone is easily deformed. * Hypothesis – A tentative explanation that is then tested to determine if it is valid. * Mantle – One of Earth’s compositional layers. The solid rocky shell that extends from the base of the…
Forces Force - acceleration requires force - push or pull - measured in Newtons (N) - causes objects to accelerate or decelerate - objects accelerate when there is a net force acting on it - objects moving at constant speeds do not have net force - objects at rest do not have net force Fundamental Forces - 4 Fundamental forces - Gravitational force - Electromagnetic force – electrons/protons attract/repel - Weak nuclear force - Strong nuclear force – holds nucleus of atoms together…
"lower world" where they would then use powerful visualisations and suggestion in order to will a healing for a sick person. Following from that, in the 1700's, Franz Anton Mesmer developed this idea further and concluded with the theory of "animal magnetism". Mesmer believed that there was an astrological influence upon human health and that this influence was presented in the form of "cosmic fluid". Mesmer felt that he could magnetise inanimate objects such as magnets and transfer this then onto patients…