Magnetic Refrigeration - Refrigerazione magnetica

1. Rotary Magnetic Refrigerator
Design and Assembly
Luca A. Tagliafico, Federico Scarpa
March 18, 2016 – Milan, Expocomfort - MCE

2. a solid’s temperature change due to
magnetic induction (B) variation.
T = T0
B > 0
T=T0+ΔT
• B increases  T increases
• B decreases  T decreases
Combining these temperature
changes with heat exchanges
with an external fluid, we can
realize a thermodinamic cycle
The magneto-caloric effect
March 18, 2016 – Milan, Expocomfort - MCE 2/16

3. B1
B2
S
T
1
2
3
4
p2
p1
S
T
1
2
3
4
B2B1
T1 T2 T3
Q2
Q1
Q1
B1B2
p1p2 p2p1
N
S
N
S
N
S
T4
N
S
The Brayton cycle
March 18, 2016 – Milan, Expocomfort - MCE 3/16

4. Research effort on magnetic refrigeration
March 18, 2016 – Milan, Expocomfort - MCE
2004
4/16

5. March 18, 2016 – Milan, Expocomfort - MCE
Main prototypes
5/16

6. First DIME magnetic refrigerator demonstrator:
- Linear reciprocating motion (fixed magnet, moving regenerator)
- AMR cycle (two parallel regenerators)
Permanent magnet structure:
- 10 NdFeB magnets
- soft steel magnetic circuit (~30kg total weight)
- magnetic gap dimensions: 130x50x13 mm3
- maximum magnetic field intensity:
1.85T (foreseen by FEM with regenerator), 1.5T (measured in free air)
FEM magnetic Actual
field analysis magnetic structure
FEM magnetic field profile
6/16

7. core process AMR
number of regenerators 2
total regenerator size 95cm3
active material commercial Gd sheeets
total Gd mass 400g
average particle size 300μm
foreseen void fraction 0.46
maximum applied field ~1.5T
minimum applied field ~<0.005T
heat transfer fluid water
flow rate operating range 5÷20 g/s (0.3÷1.2 l/min)
frequency operating range 0÷1/8 Hz
Next steps:
- Shift to rotating concept
Intrinsic balanced operations
Small inertial effects
More compact
- Patent review
- Magnetic aspects
- Geometric&mechanical aspects
- Functional design
Drawbacks
- Limited temperature span (5°C)
- Low frequency
- High moving forces
- Not well balanced operations
March 18, 2016 – Milan, Expocomfort - MCE 7/16

8. Patent & Literature review
Halbach magnet
Kitanovski
Okamura
Steyert
March 18, 2016 – Milan, Expocomfort - MCE 8/16

9. N
S
N
N N
N
S
S S
S
Rotating gadolinium sheets
Selected magnetic configuration
Static external iron bushing
Opposite water flows
Static magnets
March 18, 2016 – Milan, Expocomfort - MCE 9/16

10. 0.9 T in air
Magnetic Analysis (1)
March 18, 2016 – Milan, Expocomfort - MCE 10/16

11. Flux lines are concentrated in
the MCM (Gd) due to the
reduced reluctance, so
magnetic induction increase in
the Gadolinium sheets
1.2 T in the Gd interior
0.7 T between two Gd sheets
Magnetic Analysis (2)
March 18, 2016 – Milan, Expocomfort - MCE 11/16

12. DT= 15 °C Nu=4.36
Working condition Analysis
U=
ṁ 𝐹∙𝑐 𝑝,𝐹
ṁ 𝑀𝐶𝑀∙𝑐 𝑝,𝑀𝐶𝑀
Optimal rotational
frequency around
0.25 [Hz], with a
utilization factor
U= 0.9
U=0.9
F[Hz]
Qref [W]
March 18, 2016 – Milan, Expocomfort - MCE 12/16

13. Ovalization of the supporting
rim due to magnetic forces on
gadolinium sheets
Stress is greater in the lateral
zero field portion of the rim
Stress Analysis
March 18, 2016 – Milan, Expocomfort - MCE 13/16

14. • Simplified inlet/outlet rotating joints
• Thick bushing
• Complex internal working
• Axial rotating shaft
• Balanced configuration
• Mounting issues
Rotating configuration comparison
• Easy construction
• Easy centering of components
• Non symmetrical configuratine
March 18, 2016 – Milan, Expocomfort - MCE 14/16

15. bearing
iron bushing
bearing
shaft
distributor
distributor
shaft
rotating flange
o-ring
gadolinium sheets
Selected mechanical implementation
Iron bushingcentering element
magnet
March 18, 2016 – Milan, Expocomfort - MCE 15/16
• Magnets 2.8 kg
• Iron 10.5 kg
• Gadolinium 1.5 kg
• Alluminum 0.2 kg
weight
15 kg

16. Thanks for your attention
March 18, 2016 – Milan,
Expocomfort - MCE