Presentazione del Prof. P. W. Egolf (University of Applied Sciences of Western Switzerland) al XVI Convegno Europeo il 12 giugno 2015 - 2a sessione

1. Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
MAGNETIC REFRIGERATION
AND STANDARDIZATION
Peter W. Egolf
University of Applied Sciences of Western Switzerland
Yverdon-les-Bains, Switzerland

2. Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
E. Warburg, Magnetische Untersuchungen über einige Wirkungen der Coerzitivkraft,
Ann. Phys. 13, pp. 141 –164, 1881.
Discovery of magneto caloric effect

3. Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
Cooling process with different elements

4. Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
The principal of magnetic heating and refrigeration
Analogous four stage
processes

5. Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
Important: Standardization
Sub groups in IIR WP on Magnetic Refrigeration
Taking physical property measurements into consideration one
faces the following problems:
1) Data sets may be slightly erraneous
2) Data sets are not complete
3) First-order magnetic phase transitions show discontinuities
4) Physical models (Brillouin theory, Mean-field theory (MFT), etc.) have
also disadvantges (e.g. trancendental functions, false Curie temp., etc.)
5) Large amplifications of errors in thermomagnetic cycles occur!
New idea: Phenomenological magnetocaloric model
substance of high accurracy!

6. Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
Magnetic moments and magnetization
∑=
=
n
k
k
V
M
1
1
µ

0

=M 0

≠M

7. Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
Phenomenological model
-2 10
5
0
2 105
4 105
6 105
8 10
5
1 10
6
1.2 106
1.4 106
0 1 10
6
2 10
6
3 10
6
4 10
6
276 K
280 K
284 K
288 K
292 K
296 K
300 K
304 K
308 K
312 K
M
L
N
O
P
Q
R
S
T
U
M(A/m)
H (A/m)
000
)(
0000 )()1)((),( 0
00
HTTCeTTATHM TTB
H
µµµ
µ
−+−−= −
−
Measurements of magnetization for
different magnetic fields and tempe-
ratures (Vuarnoz et al., 2015).
Curve fitting with an exponential function
containing linear functions A, B and C
depending on temperature.

8. Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
Thermomagnetic theory
T
m
H H
s
T
M






∂
∂
−=
∂
∂
00
1
0
µ
The Maxwell relation:
is the key to by differentiation and integration obtain the specific entropy function!
Problem: Integration «constant» is function of temperature (field integration):
),0(
)(
)(
),(
0
0
0
)(
2
01
101100 TsdHe
TB
HbTA
aHcaTHs m
H
TB
H
m +∫














+−+−=
−
µ
µ
µµ
),( 0 THsm∆
M(T,H ) s(T,H )0 0
Chen et al.

9. Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
Coherence and compatibility test
-1.2 105
-8 104
-4 10
4
0
275 280 285 290 295 300 305 310 315
sm
and∆s
m
(Jkg
-1
K
-1
)
Chen et al., (1991) Vuarnoz et al., (2015)
∆s
m
for ∆H
0
=1, 3, 5 T s
m
for ∆H
0
=1, 3, 5 T
T (K)
7.5 10
5
8 105
8.5 105
9 10
5
9.5 10
5
275 280 285 290 295 300 305 310 315
s
m
*(H
0
,T)ands
m
(0,T)(Jkg-1
K-1
)
T (K)
s
m
*(3T,T)
s
m
*(5T,T)
s
m
*(1 T,T)
s
m
(0,T) Present work
s
m
(0,T) Chen et al. (1991)
),0(),(),(),(* 000 TsTHsTHsTHs mmmm =−= ∆
Our model Chen et al.
Vuarnoz et al. - Chen et al.
Well cited measurements do not fulfill coherence test!

10. Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
Ericsson thermomagnetic cycle
0
0.5
1
1.5
2
0.6 1.4 2.2 3 3.8 4.6
MofHfromGama
8 K
0 K
2 K
4 K
6 K
4 K
6 K
8 K
0 K
K
K
276 K
312 K
296 K
1, 2
4
3
7.2 105
7.6 10
5
8 10
5
8.4 10
5
8.8 105
280 285 290 295 300 305 310 315
T_s diagr table
0.5 T
1 T
3 T
5 (T)
cycle 0
cycle 2
1
2
3
4
5.0 T
3.0 T
1.0 T
0.5 T
0.0 T
µ0M(T)
µ0H (T)
s(Jm-3
k-1
)
T (K)
Work w=7.5 10 J m corresponds within 0.67 % !
5 -3

11. Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
Diverse items
1) EU 7 frame work project ELICiT deals with magnetic refrigeration
IIR is partner in this project (Didier Coulomb)
1) BASF, Haier, Astronautics Corporation unveil Next-Generation Refrigeration
Technology at CES 2015. Please see video on internet:
http://www.sustainablebrands.com/news_and_views/chemistry_materials/
sustainable_brands/basf_haier_astronautics_corp_unveil_next-gen_r)
3) Kitanovski et al. have published an interesting Springer
edition book on magnetocaloric energy conversion:

12. Latest Technologies in Refrigeration and Air Conditioning - XVI European Conference Milano, 12th - 13th June 2015
Conclusions
1) Magnetic refrigeration, heat pumping and energy conversion is an active
domain of Ra&D. Furthermore, it is at the boarder to market penetration
2) The industry is interested in standardization procedures for all magneto-
caloric technologies, e.g. for their materials and machines
3) A phenomenological model substance was developed that allows physical
modeling and numerical simulations with a predefined accurracy and which
also guarantees that energy conservation is always fulfilled
4) The model permits to make a coherence test of experimental data sets
5) Our model will be presented at the ICR 2015 in Yokohama (Japan) in more
detail.
Thank you for your attention!