Recent activities in refrigeration technology in Japan are discussed. Stirling cycle refrigerators and magnetic refrigerators are discussed. The development of units for use on trains is discussed

Fujita, T.

Ishizaki, Y.

Ohtsuka, T.

English

NASA Technical Reports Server

JAPANESE ACTIVITIES IN REFRIGERATION TECHNOLOGY
T. Fujita, T. Ohtsuka and Y. Ishizaki*
Department of Physics, Tohoku University, Sendai 980, Japan
ABSTRACT
This paper reviews recent activities in refrigeration technology in
Japan, which are stimulated strongly by growing induxtirial demands and big
national projects. At present, the JNR project on the MAGLEV train is the
most powerful one and requires all knowledges of cryogenics including various
scales of refrigeration. In fact, several R & D works are now in progress
for various types of refrigerators. Currently research activities have also
started in developing Stirling cycle refrigerators and magnetic refrigerators
for applications in a wider area.
INTRODUCTION
Research in the field of cryogenic refrigeration below 20 K in Japan was
initiated at Tohoku University as a study of low temperature physics. Besides
the accumulation of basic physical data, some effort was also made to const-
ruct helium liquefiers in this early period of study. However, the first
helium liquefier in Japan was an imported ADL Collins machine, which was in-
stalled at Tohoku University in 1952. Following Tohoku University, some other
univeristies, national laboratories and companies installed the same type of
helium liquefiers successively during the next decade. In 1958, a group at
the Institute for Solid State Physics, the University of Tokyo, succeeded in
producing liquid helium by the first Japanese liquefier of cascade type with
an output of 4 liters per hour. Helium liquefiers in this period were used
mainly for laboratory experiments. Industrial needs for larger machines have
grown up in conjunction with progress in superconducting magnet technology and
its applications.
As for cryocoolers, the Gifford-McMahon cycle was first investigated at
Hitachi Ltd. The first test machine was reported to operate successfully but
it was not directly followed by a practical machine. A recent application of
the Gifford-McMahon refrigerator will be described by Matsubara and Yasukochi
in this Conference [I]. Supported by the group in the University of Tokyo,
Osaka Oxygen Industries developed a small cryocooler of a modified Solvay
cycle in 1971. A commercial version of this machine "Cryo-mini" is now
* Technical Consultant.
33
https://ntrs.nasa.gov/search.jsp?R=19840007262 2020-03-22T07:45:00+00:00Z
available with a capacity of 1W at 15 K, being applied mainly for cryopumps.
Basic study of Stirling cycle cryocooler was carried out at the University of
Tokyo and 30 K was reached in 1972 [2]. An improved version of this test
machine will be discussed later.
Recent activities in refrigeration technology in Japan are strongly sti-
mulated by big national projects. Of such stimulants, the Japanese National
Railways (JNR) project on the superconducting magnetically levitated (MAGLEV)
vehicles is the most powerfull one at present. As part of the project, R & D
works are now in progress for various types of on-board refrigerators includ-
ing Claude cycle, Stirling cycle and Gifford-McMahon cycle machines. Some
of them are expected to meet general demandsfor applications in a wider area,
such as for cryopumps. Superconductive electronics also is one of the recent
R & D targets in Japan which require cryogenic environment. Howeverthere
have been practically no activities in developing small, low-noise cryocoolers
for this purpose. As a rare exception, the present authors have just started
to develop small Stirling cycle cryocoolers for high temperature SQUIDs.
Researchactivities have also started in developing magnetic refrigerators.
In the following, the current activities are reviewed on development of such
cryocoolers which produce low temperatures particularly below 20 K.
MAGLEVREFRIGERATION SYSTEM
The JNR MAGLEV project was initiated formally in 1970 following technical,
economical and environmental assessments. After a variety of laboratory tests,
the first running test by a i/2 scale model vehicle ML500 was conducted in
1977, using the 1.3 km section of guideway constructed in Miyazaki prefecture.
At this early stage of running tests, a sealed-off cryostat system for super-
conducting magnets was employed [3]. In parallel, research was also made on
developing small scale "on-board" refrigerators. In 1978, an on-board re-
frigerator with a capacity of 30 W at 4.4 K was installed on ML500R and
tested at 200 km/hr. A series of tests with MLS00 were successfully completed
in 1979 with achievement of a Tecord speed of 517 km/hr on the 7 km full scale
test track in Miyazaki [4].
For performance tests on more practical vehicles containing all essential
feature required commercially, the test track was converted in 1980 from the
inverted T-shape to a U-shaped guideway (Fig. I). In parallel, a test train
MLU001 was constructed. As shown in fig. 2, the final configuration of the
new model consists of three connected vehicles, each of which has eight super-
conducting magnets. Figure 3 shows the arrangement of compressors, refrigera-
tors, cryostats, and superconductive magnets. Two superconducting magnets
are installed in one cryostat on the first and third cars (MLU001-1 and -3),
whereas each magnet is installed individually in one crvostat on the second
car (MLU001-2). To compensate for heat leak to cryostats, one refrigerator per
car system is employed on MLU001-1, but one refrigerator per cryostat system
is employed on MLU001-2 and -3. The configuration is expected to allow
critical comparison between various systems.
34
A remarkable progress has been madein cryostat design during the past
ten years. Finally, a cooling capacity of 2.5 Wper magnet was specified for
the cryocooler to compensatethe heat leak. JNR is developing various on-
board refrigerators in collaboration mainly with three industrial groups:
Hitachi Ltd., Toshiba Co./ SumitomoHeavy Industries Ltd., and Mitsubishi
Electric Co./ Aisin Seiki Co.
Figure 4 shows a Claude cycle refrigerator of type A with a capacity of
30 Wat 4.4 K developed for MLU001-1. Specifications of the machine are
listed in the Table I. The machine has 5 stages of heat exchangers, 2 ex-
pansion engines and a Joule-Thomsonvalve.
Claude cycle refrigerators of type B with a capacity of 5 Wat 4.5 K
were independently developed and installed on MLU001-2and -3. Figure 5
showsone of the machines attached on the cryostat. The heat exchangers
which were adopted for this type of refrigerators will be described by
Koizumi et al. in this Conference [5].
An on-board refrigerator of type C which consists of Stirling cycle and
Joul-Thomson loop, was also developed for MLU001-2. The J-T loop has four
heat exchangers, three precoolers and a J-T valve. Each stage of the pre-
coolers is cooled by a three stage Stirling cycle refrigerator, which is
operated at 4.93 Hz with helium gas pressure of 16 kg/cm2. The coldest stage
of the refrigerator reached ii.i K. The overall cooling capacity of this
machine is 8 W at 4.37 K. Further effort is concentrated on developing a
StJ_ ing cycle machine which can reach 4 K without J-T loop.
In Novemberof 1982, JMRsucceeded in the mannedtest run with three
connected cars train MLU001which carries these various types of refrigera-
tors.
OTHER DEVELOPMENTS
STIRLING CYCLE CRYOCOOLER
After basic investigation on regenerators and refrigeration cycles,
Ishizaki and his co-workers at the University of Tokyo designed some Stirling
cycle cryocoolers in the early 1970s. A three-phase Stirling cycle machine
was constructed to obtain optimal design figures. Especially the effect of
phase angle on refrigeration output was investigated with different compres-
sion and expansion volume ratios. Based on the result, they next constructed
a four-phase Stirling cycle cryocooler, in which the pistons were driven with
a swash plate. This machine produced a refrigeration output of 45 W at 78 K
[2]. A four-phase regenerator, which consists of multi-layers of metal plate
fixed with adhesives and small metal balls inside was also developed for
compact design and improvement in thermal efficiency.
More recently, Ishizaki cooperated with a group of Aisin Seiki in deve-
loping a commercial Stirling cycle cryocooler. Figure 6 shows the 2 stage
Stirling cycle cryocooler developed for general purposes including application
35
to cryopumps. A swashplate driving mechanismis employedto convert motor
rotation to reciprocal motions of four pistons which are arranged at 90 degree
intervals. A pair of the counter pistons is for the second stage of 20 K
cooling circuit, whereas the other pair is for the first stage of 90 K cooling
circuit which is used to precool the 2nd stage. Cooling capacities of 20 W
and 150 Ware reported at the first stage temperature of 90 K respectively
with cooling downtime of about 15 minutes.
A low noise Stirling cycle cryocooler is also investigated for cooling
SQUIDsensors. Recently, we developed Nb3GeSQUIDswhich operate satisfac-
torily at temperatures approaching 18 K [6]. Our device has a relatively wide
range of operating temperature. High temperature and wide range operation
make the cryocooler design more practical with sufficient margin. In col-
laboration with Aisin Seiki, our group at Tohoku University constructed a two
stage Stirling cycle cryocooler, in which small lead balls of 0.1 mmin dia-
meter were used for the coldest part of the regenerators. A front view of
our machine and an enlarged view of the cold heads are shownin Fig.7. This
cryocooler was built to test a design for compact, light weight, easy-to-
handle refrigerators for eventual use in cooling cryogenic sensors. Measure-
ments are now undertaken on cooling performance, mechanical vibration, tem-
perature fluctuation, electromagnetic noise, etc. Specification are listed
in Table 2. Expected cooling capacity is 50 mWat 15 K. Although the tests
with this trial machinehave not been completed, a non-metalic structure and
the use of heat pipe are now under consideration as a next step for reducing
magnetic noise and temperature fluctuation respectively.
MAGNETICREFRIGERATION
A study group on magnetic refrigeration was formed at the Society of
Non-traditional Technology in 1980 to look into the possibility of its future
use in refrigeration ranging from sub-room temperatures downto superfluid
helium temperature (_1.8 K). More recently, a group at the Tokyo Institute
of Technology lead by Hashimoto and a group at Toshiba have cooperated in
constructing a prototype machine aimed at establishing the feasibility of a
magnetic refrigerator working between 20 K and 4.2 K. The working substance
used is Gadolinium Gallium Garnet (GGG)single crystal which has a relatively
high entropy density, high heat conductivity and reasonably high Debyetem-
perature (_500 K). As the lattice entropy is small comparedto the spin
entropy below 20 K for GGG,the refrigerator may , in principle, be operated
in a Carnot cycle. Heat of magnetization at the high temperature isothermal
was removedby gaseoushelium flowing through a pipe P (Fig.8). The lower
end of GGGwas attached to a thermosiphon, the cold end of the thermosiphon
wasused to condensehelium gas. By measuring the rate of liquefication of
helium, the refrigeration capacity at 4.2 K for a cycle starting at 16 K and
6.7 T using 1.7 mole of GGGwas estimated to be 42 J whenthe field was
reduced at a rate of 0.67 T per sec [7]. The magnetic field for this experi-
ment was changedby energizing and de-energizing a superconducting pulse
magnet at various sweeprates. This modeof altering the magnetic field is
not favourable for practical use due to extra losses incurred in operation of
the superconducting magnet. The experiment is still in its initial stage,
however, and the method wasused to investigate problems in the magnetic
36
refrigeration cycle proper.
CONCLUSION
Groups engaged in R & D works on cryocoolers in Japan are summarized in
Table 3. Almost all cryocooler activities are more or less stimulated by big
national projects as pointed out in the introduction.
JNR invested more than 20 billion yen in the MAGLEV project and since
1979 the government has been subsidizing the project with an annual outlay of
600 million yen. However, the amount of the funds alloted to the refrigera-
tion technology is not known.
Science and Technology Agency appropriated 463 million yen in the 1982
fiscal year budget for promoting R & D studies for establishing the technolo-
gical base of applied superconductivity and cryogenics. Out of the total
fund, about 95 million yen is to be alloted for refrigeration technology
regarding Stirling cycle cryocoolers and magnetic refrigerators.
Ministry of Education and Culture supported university research on
superconductive electronics with a grant of 600 million yen for the period
1979 to 1981. Although the need for small cryocoolers gained gradual recog-
nition in this area, development efforts are still minor.
Although basic research and digital application of superconductivity are
in progress at various industries, Nippon Telegraph and Telephon Public Cor-
poration, and Electrotechnical Laboratory. However, no explicit activities
have not been reported on refrigeration at present.
The authors would like to thank Y. Kyotani for providing them with a
mass of information on the JNR project.
37
Table 1 Specifications of JNRMAGLEVOn-Board Refrigerators
Type A
Claude
Inlet Pressure
(kg/cm2G)
Ref. Cycle Claude StirlinR+J-T
Cooling Capacity at
4.4 K (W) 30 5 8
tie Flow Rate
(Nm3/h) 150 30 17.2
15 16 18.9
Size diam (mm)
length (mm)
400
1400
300
8OO
296
796
Weight (Kg) 140 40 33.9
Table 2 Specifications of the Cryocooler Built in Tohoku University
to Test a Design for Eventual Use in Cooling Cryogenic Sensors.
Item Specification
Refrigeration Cycle Stirling cycle
Output (cooling capacity) 50 mW at 15 K
Lowest temperature _ 10 K
Working gas Helium
Input power 150 W
Dimension 260mm x 290mm x 540 mm
Weight 24 Kg
Drive _ 5 Hz
38
Table 3 List of GroupsWorking with Cryocoolers in Japan
Group
Aisin Seiki Co. Ltd.
Leader
[
!
T. Tani
Consultant
Hitachi Ltd.
JNR
Mitsubishi Electric
Corporation
Sumitomo Heavy
Industries, Ltd.
Toshiba Corporation
Nihon University
Tohoku University
Tokyo Institute of
Technology
i Y. Ishizaki
i
i
I
1
T. Fujinaga
Y. Kyotani
i
I
I
i Y. Furuta
I
T. Koizumi
M. Yamaji
H. Nakagome
Y. Matsubara
T. Ohtsuka
T. Fujita
T. Hashimoto
Object
Mag. Lev.
Cryopump
SQUID
Mag. Lev.
Josephson Com-
puter
Cryopump
Nag. Lev.
Nag. Lev.
Mag. Lev.
Mag. Lev.
Mag. Lev.
Superfluid 4He
Refrigeration
Cycle
Stirling + J-T
Stirling
Stirling
Stirling Cycle
Machine
Cryogenic System
Claude
Stirling
G-M + J-T
Claude
G-M + J-T
Claude
Claude
Magnetic Refri-
rator
Study of
Regenerator
SQUID
Superfluid 4He
Regenerative
Cycle
Stirling
Magnetic Refri-
gerator
39
ML 500
(a
I-t--n
W///////j
MLU 001
_//////////////////////.>'_
(b)
Figure I. Schematic views of (a) ML500 on the inverted T-
shaped guideway and (b) MLU001 on the U-shaped guideway.
The vehicles carry liquid helium cryostat systems of L-shape
and I-shape respectively.
Figure 2. Photograph of MLU001 running on the test track.
40
MLU 001-I MLU 001-2 M LU 001-3
Is $I
s sl
Is s s Sl
I S S S
Figure 3. Schematic diagram of the cryogenic system on MLU001. S : Super-
conducting magnet, R : Refrigerator, C : Compressor.
Figure 4. A Claude cycle on-board refrigerator of type A.
41
Liq. He Tank
_"_---......,:..-fR ef ri ger at or
1 t _ _._--_t.J_--<*_'--_ / [ _ Superconducting/
_ .__.',j., --14_ ! V_s_t
Persistent __----.... I "_ \ ;
Current "- __..__ ] i
Switch Outer __ _.-'
Figure 5. Photograph (upper) of an on-board refrigerator mounted
on the I-shaped cryostat system. The structure is outlined in
the schematic drawing (lower).
42
Figure 6. A 2-stage Stirling cycle cryocooler
commercially developed for general purposes.
43
Figure 7.
(a) (b)
A test model of low-power Stirling cycle cryocooler for SQUID
sensors: (a) front view and (b) cold head
44
J
GG
SUPERCONDUCT ING '.
MAGNET = ... =
• • ° _ °
He Gas for Cooling
I
THERMOSI PHON
I
STAINLESS
STEEL
COPPER
Liq. He
Filling Tube
COPPER
n
,°
• .
• °
Figure 8. Schematic arrangement of experiments on
magnetic refrigeration
45
REFERENCES
[i] Matsubara, Y. and Yasukochi, K.: An Application of Gap Regenerator/
Expander Precooled by Two State G-M Refrigerator (This Conference).
[2] Oshima, K. and Ishizaki, Y.: Refrigeration Technology in Japan, Proc. 5th
International Cryogenic Engineering Conference, Kyoto, edited by
K. Mendelssohn, IPC Science and Technology Press (1974) pp.357-360.
[3] Ishizaki, Y., Kuroda, T. and Ohtsuka, T.: Sealed Cryostat System for
Magnetically Levitated Vehicles, ibid., pp.i02-i05.
[4] Ohtsuka, T. and Kyotani Y.: Recent Progress in Superconducting Magnetic
Levitation Tests in Japan, IAS Conference Record, CH1575-0/80/0000-0238,
IEEE (1980) pp.238-243.
[5] Koizumi, T., Kanazawa, M., Takahashi, M., Uchida, T. and Suzuki, M.: A
Small and Light Weight Heat Exchanger for On-Board Helium Refrigerator
(This Conference).
[6] Fujita, T., Suzuki, M., Ikegawa S., Ohtsuka, T. and Anayama, T.: High
Temperature Operation of Nb3Ge SQUIDs, Proc. 9th International Cryogenic
Engineering Conference, Kobe, edited by K. Yasukochi and H. Nagano,
Butterworth & Co. (1982) pp369-372.
[7] Hashimoto, T.: private communication.
46


Japanese activities in refrigeration technology

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