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Novel magnetocaloric materials formagnetic cooling applications
M. Katter Vacuumschmelze GmbH & Co. KG
page 2
outline
• introduction
• thermodynamic basics of magnetic cooling
• LaFeSi-based alloys produced by powder metallurgy
• prototypes and applications
• conclusions
page 3
magnetocaloric effect: discovered by Wartburg 1881magnetic cooling: Debye and Giauque 1926
page 4
magnetic refrigeration at room temperature
Features
no compressorno green house gaseshigh efficiencynew magnetocaloric materialspermanent magnets
Applications
industrial coolingair conditioningfood refrigeration
O. Tegus, E. Brück, K.H.J. Buschow, F.R. de Boer, Nature, vol. 415 (2002) 150.
„compression“
„expansion“
page 5
motivation for magnetic cooling
- > 180 Mio. new cooling devices every year, needing ten-thousand tonsof environmentally harmful coolants (HFCs), 28-45% of CO2 equivalent in 2050 (Velders 2009)R134a banned in newly developed cars since 2011 in Europe
magnetic cooling uses solid, environmentally friendly coolants
- alternative CO2-compressors need pressures > 100 barmagnetic cooling devices need only 1-2 bar
- gas compression cycles reach ca. 40 % of Carnot-efficencymagnetic coolers reached ca. 60% in laboratory
- compressors are noisymagnetic cooling devices are silent
magnetic cooling cycle for a single magnetocaloric material
page 6
COP = 90
ΔS = 15 J/kgK
magnetic cooling cycle for a set of 10 magnetocaloric materials
page 7
COP = 10
page 8
„Giant“ magnetocaloric effect
K. Gscneidner (2007)
page 9
new magnetocaloric materials
K. Gscneidner (2007)
accessable withNd-Fe-B magnets
page 10
Designs for active magnetic regenerators
J.A. Barclay and S. Sarangi 1984 in A.M. Tishin and Y.I. Spichkin 2003
large pressure drops in powder beds?
page 11
- casting- anneal, e.g. 1080°C/140 h- optionally load with hydrogen
⇒ long annealing times, ⇒ with hydrogen only powder
- melt spinning- short anneal, e.g. 1000°C/2 h
⇒ only flakes or powder, no shaped parts for heat exchangers
conventional preparation of La(Fe,Si)13
S. Fujieda et al. 2005F.X. Hu et al. 2005 (with Co)
O. Gutfleisch et al. 2005S. Hirosawa et al. 2006
K. Niitsu 2012
page 12
Powder Metallurgical (PM) Processing of La-Fe-Si
P
Vacuum Induction Alloying and Casting
Crushing
Milling
Blending
Pressing:CIP - die
isostatic pressing
die-pressing
elemental powders
page 13
Powder Metallurgical (PM) Processing of La-Fe-SiP
Pressing:CIP - die
die-pressing
Isostaticpressing
Reactive Sintering
Machining and Surface Finishing
page 14
set of La-Fe-Co-Si parts for a magnetic regenerator
0
1
2
3
4
5
6
7
8
9
10
-20 -10 0 10 20 30 40 50 60 70 80temperatur (°C)
entr
opy
chan
ge -Δ
Sm
(J/k
gK)
ΔH = 16 kOe
page 15
MFP-1056, TC = -14°C
-0,50
-0,40
-0,30
-0,20
-0,10
0,00
0,10
0,20
-100 -50 0 50 100 150 200
temperature [°C]
stra
in [%
]
magnetocaloric passive statea-Fe = 71 %
magnetocaloric active statea-Fe = < 2%
reversible conversion
good machinability
good magnetocaloric properties
0,0
2,0
4,0
6,0
8,0
10,0
230 240 250 260 270 280
temperature T (K)
- ∆S
m (J
/kgK
)
4,0
8,0
12,0
16,0
Hmax (kOe)
Thermally induced Decomposition and Recombination (TDR) process
difficult to machine
tensile stress=> cracks
Katter et al. 2009
page 16
La-Fe-Co-Si blocks and platelets with thicknesses of 0.25 – 1.0 mm
page 17
monolithic La-Fe-Co-Si regenerators with 0.2 mm slots
Linearly graded LaFeCoSi parts
page 18
P
1. Compaction of powderswith different Co content
2. Sintering and diffusion treatmentto generate linearly varying TC
page 19
sintered La-Fe-Mn-Si-Hx powders
particle sizeca. 400 µm
page 20
prototype for wine cooler, HEIG, Yverdons le Bains, CH, M. Balli (2010)
regenerator with Gd
regenerator with LaFeCoSi
page 21
prototype of Astronautics, USA
with La-Fe-Si-Hx powder from VAC400 W cooling power at 14°C temperature span
best performance up to now!
S. Russek(2010)
page 22
magnetocaloric cooling systemmaterials
magnet assemblies
thermo-hydraulicsmechanics
Cooltech Applications (2008)
ca. 0,3 kg La-Fe-Si +ca. 1,5 kg Nd-Fe-Bper kW cooling power
Astronautics (2001)
page 23
room temperautre magnetic refrigeration prototypes
K. Gscneidner (2007)
page 24
conclusion
- magnetocaloric effect is the temperature change of a material in dependence on a magnetic field change
- La(Fe,Co,Si)13 and La(Fe,Si)13Hx with tunable Curie temperaturecan be produced by powder metallurgy
- prototypes for application at room temperature under construction
- there is a huge market for magnetic cooling, also due to upcomingenvironmental legislation for HFCs