Experimental investigation of 20 K two-stage layered active magnetic regenerative refrigerator
Inmyong Park and Sangkwon Jeong
Cryogenic Engineering Laboratory, KAIST, Daejeon, Republic of Korea
Experimental results
Introduction
Case 1: mHe, AMR1 = 0.15 g/s, mHe, AMR2 = 0.07 g/s
✓Since MCE is a reversible process, it facilitates high thermodynamic efficiency of an AMRR.
80
T10
T9
T8
T7
T6
Temperature (K)
70
✓Wide temperature span can be achieved by multi-layered structure of the active magnetic regenerator (AMR).
Experimental apparatus and methodology
60
50
40
30
684
686
688
690
72 mm, GdNi2
60
Temperature (K)
✓An AMRR utilizes magneto-caloric effect (MCE) of a magnetic refrigerant for cooling.
T5
T4
T3
T2
T1
50
684
686
1
690
15 mm, Gd0.1Dy0.9Ni2
50
Valve 3
Valve 4
Thermal
anchoring
HXW 2
2
Void volume 1
LN2
chamber
H
T
AMR1
AMR2
LTS magnet
2308
Liquid helium
level meter
Experimental procedure
2312
2304
2306
2308
2310
Ar:R14:R218 = 0.2:0.6:0.2
40
100
2312
Case 1 :
T9
Case 3 :
T9
110
Time (s)
120
130
140
150
160
T7
T7
170
180
190
40
4T
35
0T
Dy0.5Er0.5Al2
30
Ar:R14:R218 = 0.2:0.6:0.2
Case 1 :
T2
Case 3 :
T2
25
20
50
60
70
80
90
100
110
120
T4
T4
130
140
Entropy (J/kg-K)
Entropy (J/kg-K)
Case 3: mHe, AMR1 = 0.07 g/s, mHe, AMR2 = 0.03 g/s
Calculated cooling capacity of the AMR system
1.0
AMR1
Hot film sensor
80
Temperature
sensor
70
LTS magent
AMR2
T10
T9
T8
T7
T6
60
50
40
30
3250
3252
3254
Time (s)
1.
2.
3.
4.
5.
6.
7.
2310
45
4T 0T
AMR1 QL
Void volume 1
Hot film sensor
2306
20
50
Void volume 2
Dump resistor
HXW 3
2304
30
Time (s)
Vacuum
chamber
Vacuum chamber
3
40
40
4T 0T
GdNi2
55
Gd0.1Dy0.9Ni2
45
0T
4T
Filling liquid nitrogen in liquid nitrogen chamber
Pre-cooling of the AMR with liquid nitrogen by one way-circulating flow of the helium gas
Pre-cooling of the LTS magnet with liquid nitrogen
Cool-down of the LTS magnet with liquid helium
Test operation of the LTS magnet
Synchronizing the phase of the mass flow rate and the AC operation of the LTS magnet
Changing the experimental conditions
3256
3258
60
T5
T4
T3
T2
T1
50
40
30
20
3250
3252
3254
3256
Cooling capacity (W)
Sol.
valve 2
50
30
Temperature sensor
feedthrough
P2
50
Ar:R14:R218 = 0.4:0.1:0.4 Ar:R14:R218 = 0.4:0.1:0.4
Vacuum port
Thermal anchoring
with LN2 reservoir
T5
T4
T3
T2
T1
Temperature (K)
HXW 1
60
60
Temperature (K)
T10
T9
T8
T7
T6
Temperature (K)
LN2 cryostat
1
Temperature (K)
MFM
Sol.
valve 1
Time (s)
T-s diagram of the case 1 and the case 3
Dy0.85Er0.15Al2
Cryostat
5
T1
692
3
Temperature (K)
Helium
compressor
P1
.
-m
65
70
Vapor cooled
current lead
3
10
Time (s)
80
Tandem
rotary
Valve 1 valve
7
35 mm, Dy0.5Er0.5Al2
60
Water
bath
.
m
Temperature (K)
2
688
Case 2: mHe, AMR1 = 0.12 g/s, mHe, AMR2 = 0.05 g/s
GHe
Feedline
48 mm, Dy0.85Er0.15Al2
64 mm,
Magnet 2
30
Time (s)
Temperature sensor
feedthrough
114 mm,
Magnet 1
H
40
20
692
T10
0.6
0.4
0.2
0.0
0.00
3258
Time (s)
AMR2 QL
0.8
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
Mass flow rate (g/s)
Conclusion




The two-stage AMRR system proposed for the operation between 77 K and 20 K has been tested.
The modified AMR system reached the lowest no-load temperature of 25 K without gas expansion effect.
The performance of the AMR is also influenced by shuttle heat transfer and the environmental liquid helium.
Each effect of shuttle mass or liquid helium on the overall cooling performance has not been decoupled from the original MCE.
Acknowlegement This research was supported by the Converging Research Center Program through the Ministry of Science, ICT and Future Planning, Korea (2014M3C1A8048836).