JPH11193979A - Low temperature liquefied gas cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low temperature liquefied gas cooler for suppressing an external heat entering amount by reducing a vibrating noise from a refrigerator and relatively simplifying a constitution of the overall cooler. SOLUTION: The low temperature liquefied gas cooler comprises a storage container 102 for storing a low temperature liquefied gas, a condensing tank 104 disposed above the container 102, transfer tubes 122, 124 for communicating the tank 104 with the container 102, and a refrigerator 106 for condensing the gas in the tank 104. A recondenser 138 of the refrigerator 106 is disposed in the tank 14. An evaporated gas in the container 102 is fed into the tank 14 via the tube 122. The liquefied gas condensed in the tank 104 overflows to flow down in the container 102 via the tube 124.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a low-temperature liquefied gas cooling apparatus for cooling a low-temperature liquefied gas.

[0002]

2. Description of the Related Art For measuring the strength of a magnetic field generated from a living body such as the human brain, arm, eyeball and heart, a superconducting ring is combined with one or two Josephson junctions. A superconducting quantum interference magnetometer is used, and the sensor of the magnetometer is immersed in liquid helium in a storage container composed of a low-temperature constant temperature bath. Then, in order to measure the magnetic flux from the human brain or the like, the temperature of the liquid helium is kept in a range of, for example, 4.2 ± 0.1K.

As a cooling device used in such a superconducting quantum interferometer, for example, a cooling device having a configuration shown in FIG. 4 is known (JP-A-4-39500). This known cooling device includes a storage container 2 covered with a heat insulating material, and a refrigerator 4 for cooling liquefied helium gas as a low-temperature liquefied gas. A liquid phase portion 6 of liquefied helium gas, that is, liquid helium exists in a lower portion of the storage container 2, and a gas phase portion 8 of liquefied helium gas, that is, gas helium exists in an upper portion thereof. It is immersed in the liquid phase part 6 in the container 2. A recondenser 10 of the refrigerator 4 is provided in the gas phase portion 8 in the storage container 2, and the refrigerator main body 12 of the refrigerator 4 and the recondenser 10 are connected via a pair of transfer pipes 14 and 16. Have been.

In such a cooling device, the cooling device 4
For example, liquid helium is used as a heat medium of the transfer pipe 1 and the heat medium cooled by the cooler main body 12 is transferred to the transfer pipe 1.
4 to a recondenser 10. Recondenser 10
Cools the gaseous helium in the gas phase part 8 in the storage vessel 2,
As a result, the liquefied helium gas is condensed and reliquefied. The heat medium of the re-condenser 10 is further returned to the cooler main body 12 through the transfer pipe 16, re-cooled by the cooler main body 12, and then sent to the re-condenser 10 again, thus the heat medium is circulated. Is done.

[0005]

However, in this known cooling device, the recondenser 10 of the refrigerator 4 is disposed in the gas phase portion 8 of the storage vessel 2, so that the refrigerator main body 12
And the storage container 2 are directly connected via the transfer pipes 14 and 16, and the mechanical vibration noise of the refrigerator main body 12 is transmitted to the storage container 2. As a result, the magnetic field is accurately detected by the interferometer. It becomes difficult to measure.

In order to solve such a problem, for example, a configuration shown in FIG. 5 has been proposed. The cooling device shown in FIG. 5 includes a storage container 22 covered with a heat insulating material,
A condensing tank 24 for condensing liquefied helium gas as a low-temperature liquefied gas and a refrigerator 26 for cooling liquefied helium gas are provided. A liquid phase portion 28 of liquefied helium gas exists at a lower portion of the storage container 22, and a gas phase portion 30 of liquefied helium gas exists at an upper portion thereof.
2 is immersed in the liquid phase part 28 in the storage container 22. Also,
A liquid phase portion 34 exists at a lower portion of the condensing tank 24, and a gas phase portion 36 exists at an upper portion thereof. The on-off valve 37 connects the gas phase portion 30 of the storage container 22 and the gas phase portion 36 of the condensing tank 24. The gas phase part 30 of the storage phase 22 and the liquid phase part 34 of the condensing tank 24 are connected via a transfer pipe 40. A re-condenser 42 of the refrigerator 26 is provided in the gas phase portion 36 in the condensation tank 24, and a refrigerator main body 44 of the refrigerator 26 is provided.
And the re-condenser 42 are connected via a pair of transfer pipes 46 and 48. Further, a liquid helium supply device 50 such as a pressurizing device is provided in the condensation tank 24, and the liquid helium supply device 50 and the gas phase portion 36 of the condensation tank 24 are connected via a feed pipe 52.

In such a cooling device, gaseous helium in the gaseous phase portion 30 of the storage vessel 22 passes through the open / close valve 37 and the transfer pipe 38 so that the gaseous helium gas in the vapor phase portion 36 of the condensing tank 24 is removed.
Flows to The cooler body 44 of the cooler 26 cools the heat medium (for example, liquid helium), and the cooled heat medium is supplied to the re-condenser 42 through the transfer pipe 46. Recondenser 4
2 cools the gaseous helium in the gas phase portion 8 in the condensing tank 24, whereby the helium gas is condensed and reliquefied. The heat medium of the re-condenser 10 is further returned to the cooler main body 44 through the transfer pipe 48, re-cooled by the cooler main body 44, and then sent again to the re-condenser 42, and thus the heat medium is circulated. Is done. The liquid helium in the liquid phase portion 34 of the condensing tank 24 is supplied to the storage container 22 through the transfer pipe 40,
In this way, liquid helium is circulated. When supplying liquid helium, the on-off valve 37 is held in a closed state,
In this state, the gas phase portion 36 of the condensing tank 24 is pressurized by the pressurized helium gas from the liquid helium supply device 50.

In the proposed cooling device, the re-condenser 42 is disposed in the condensing tank 24, and the cooler main body 44 is connected to the condensing tank 24 via the transfer pipes 46 and 48, so that the refrigerating machine is cooled. The mechanical vibration from the machine body 44 causes the storage container 22
To the storage container 22
The vibration noise generated in can be suppressed. However, the liquid helium supply device 50 for supplying the liquid helium in the condensation tank 24 to the storage container 22 and the on-off valve 37
In this connection, the size of the cooling device is increased, and the manufacturing cost is increased. Further, in connection with the above-described configuration, the distance between the storage container 22 and the condensing tank 24 is relatively large, in other words, the length of the transfer pipes 38 and 40 is increased. And the amount of heat entering through the liquefied helium gas is increased, and a cooler having a high refrigeration capacity is required to cool the liquefied helium gas as desired.

An object of the present invention is to provide a low-temperature liquefied gas cooling apparatus capable of reducing vibration noise from a refrigerator, relatively simplifying the configuration of the entire apparatus, and suppressing the amount of heat entering from the outside. That is.

[0010]

SUMMARY OF THE INVENTION The present invention provides a storage container for storing a low-temperature liquefied gas, a condensation tank disposed above the storage container, and a first and a second tank for communicating the condensation tank with the storage container. A second flow path, and a refrigerator for condensing the gas in the condenser, wherein the refrigerator includes a re-condenser for condensing the gas, and the re-condenser is a gas phase part of the condenser. And the gas in the condensing tank is condensed by the re-condenser, and the first flow path communicates the gas phase of the storage vessel with the gas phase of the condensing tank. The gas in the container flows into the condensation tank through the first flow path,
The flow path communicates the gas phase of the storage vessel with the boundary between the liquid phase and the gas phase of the condensing tank, and the liquid in the condensing tank overflows to form the second stream. A low-temperature liquefied gas cooling device characterized by flowing down to the storage container through a passage.

According to the present invention, the gas phase of the storage vessel and the gas phase of the condensing tank are communicated via the first flow path, and the re-condenser of the refrigerator is arranged in the gas phase of the condensing tank. As a result, the evaporated low-temperature liquefied gas is condensed in the condensing tank by the action of the re-condenser. The refrigerator is directly connected to the condensing tank,
As a result, mechanical vibration transmitted from the cooler to the storage container can be significantly suppressed. Also, since the condensing tank is disposed above the storage container, the liquid gas in the condensing tank can be sent to the storage container using gravity, and a dedicated feeding device for sending the liquid gas Can also be omitted. In addition, by disposing it above, the distance between the storage container and the condensing tank, in other words, the length of the first and second flow paths can be shortened. The amount of heat entering can be reduced. Further, one end of the second flow path is communicated with the gas phase of the storage vessel, and the other end is communicated with the boundary between the liquid phase and the gas phase of the condensation tank. The gas flows down into the storage container by overflow, and the liquefied gas can be circulated with a relatively simple configuration.

The present invention also provides an internal space of the storage container,
The internal space of the condensation tank and the first and second flow paths define a substantially closed circulation space.

According to the present invention, the interior of the storage vessel in which the low-temperature liquefied gas is circulated, the interior of the condensing tank, and the first and second flow paths constitute a substantially closed cycle system.
The liquefied gas can be efficiently reliquefied without the low-temperature liquefied gas flowing out or flowing in from the outside.

Further, the present invention relates to a refrigeration capacity R of the refrigerator.
Is larger than the total heat penetration amount TQ which is the sum of the heat penetration amount of the storage vessel, the heat penetration amount of the condensation tank, and the heat penetration amount of the first and second flow paths (R> TQ In connection with this, a heater is disposed in the gas phase of the condensing tank, and by controlling the heater, the heat balance between the refrigerating capacity R of the refrigerator and the total heat penetration is maintained. Dripping.

According to the present invention, the refrigerating capacity R of the refrigerator is larger than the total heat inflow TQ in the cooling device. In connection with this, a heater is provided in the condensing tank. . Therefore, the refrigerator is always operated with the predetermined refrigerating capacity, and the imbalance between the refrigerating capacity R of the refrigerating machine and the total heat inflow amount TQ of the refrigerating apparatus is maintained by controlling the heater, so that the heat balance is relatively simple. With the configuration and simple control, the low temperature liquefied gas can be cooled as required.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a low-temperature liquefied gas cooling apparatus according to the present invention will be described below with reference to FIGS.

Referring to FIG. 1, a cooling device shown includes a storage container 102 covered with a heat insulating material, a condensing tank 104 for condensing low-temperature liquefied gas, and a refrigerator for cooling low-temperature liquefied gas. 106. This cooling device is used, for example, to cool a superconducting quantum interferometer (SQUID) for measuring the strength of a magnetic field generated from a human brain or the like. In such a case, liquefied helium gas is used as a low-temperature liquefied gas. Is used.

The storage container 102 has a substantially sealed container body 108 in which liquefied helium gas is stored. In order to measure a magnetic field generated from the human brain or the like, the temperature of the liquefied helium gas in the container body 108 is kept at, for example, 4.2 ± 0.1K.
In such a liquefied helium gas, a liquid phase portion 110 of the liquefied helium gas, that is, liquid helium exists at a lower portion of the container body 108, and a gas phase portion 112 of the liquefied helium gas, that is, gas helium exists at an upper portion thereof. The sensor 114 of the interferometer is immersed in the liquid phase 110 in the container body 108.

The condensing tank 104 has a substantially sealed tank body 116, which also contains a liquefied helium gas as a low-temperature liquefied gas.
There is a liquid phase 118 of liquefied helium gas at the bottom of
Above the gas phase, there is a gaseous phase section 120 of liquefied helium gas. Referring also to FIG. 2, the container body 108 and the tank body 116
Are connected via a pair of transfer pipes 122 and 124. In this embodiment, one end of the first flow path defined by the transfer pipe 122 is connected to the gas phase section 122 of the container body 108.
The other end is opened to the gas phase 120 of the tank body 116, and the first flow path is connected to the gas phase 11 of the container body 108.
2 and the gas phase part 120 of the tank body 116 are communicated. Also,
One end of the second flow path defined by the other transfer pipe 124 opens to the gas phase part 112 of the container body 108, and the other end is a boundary between the liquid tank part 118 of the tank body 116 and the gas phase part 120. The second flow path communicates the gas phase portion 112 of the container body 108 with the above-described boundary portion of the tank body 116. Since the container body 108 and the tank body 116 are connected as described above via the transfer pipes 122 and 124, the container body 1
08 in the gas phase 112 flows into the gas phase 120 of the tank body 116 through the first flow path.
The liquid helium at the boundary 16 is returned to the gas phase 112 of the container body 108 via the second flow path.

The transfer pipes 122 and 124 may have an integrated structure, for example, a pipe member having a concentric double structure over substantially the entire length. In this case, the inner pipe member functions as the transfer pipe 124 through which the liquid helium flows, and the outer pipe member functions as the transfer pipe 12 through which the gas helium flows.
2 and transfer pipes 122 and 124
Can enhance the heat insulating effect. At the end of the tube member, the inner tube member communicates with the gas phase portion 120 of the condensation tank 104, and the outer tube member communicates with the above-described boundary portion of the condensation tank 104.

The storage container 102 and the condensing tank 104 are preferably disposed in a magnetic shield housing 126 as shown in FIG. The shield housing 126 defines a magnetically substantially shielded shield chamber 128 in which the reservoir 102 and the condensing tank 104 are provided. With this configuration, it is possible to cut off the magnetic flux from the outside, and thus it is possible to significantly reduce the magnetic noise picked up by the sensor 114.

In this cooling device, it is important that the condensing tank 104 is disposed above the storage container 102. In this embodiment, four (three in FIG. 3) columns 130 are provided at intervals in the shield housing 126, and these columns 130 are connected to the shield housing 126.
Is fixed between the bottom wall 132 and the top wall 134 of the slab. The storage container 102 is disposed at an intermediate portion in the vertical direction of the column 130, and the outer periphery of the container body 108 is attached to the column 130 via a mounting bracket (not shown) or the like. The condensing tank 104 is disposed at the upper end of one of the four columns 130 (the right side in FIG. 3), and one side wall of the tank body 116 is fixed to the columns 130 via a mounting bracket (not shown) or the like. ing. By arranging the storage container 102 and the condensation tank 104 in this manner, the condensation tank 10
4 can be supplied by gravity drop into the storage container 102, and the liquid helium can be returned to the storage container 102 without providing a dedicated supply device.
In addition, by arranging in this manner, the storage container 10
2 and the condensing tank 104 can be arranged close to each other, and by reducing the length of the transfer pipes 122, 124, heat invasion from outside through these transfer pipes 122, 124 can be reduced. it can.

Referring again to FIG. 1 and FIG.
The re-condenser 138 of the refrigerator 106 is
Is provided, and the refrigerator main body 140 of the refrigerator 106 and the re-condenser 138 are connected via a pair of transfer pipes 142 and 144. GM known per se as the refrigerator 106
(Gifford-McMahon) refrigerators can be used, in which case liquid helium is used as the heating medium. Refrigerator 1
06 has a compressor 146 for operating it.
Is attached. The refrigerator main body 140 has a compressor 146.
The liquid helium, which is operated by the cooling device 140 and cooled in the cooler body 140, is supplied to the re-condenser 138 through the transfer pipe 142, and then is transferred through the transfer pipe 142.
And cooled again. Thus, the refrigerator 106 and the condensing tank 104 are connected via the transfer pipes 142 and 144,
The condensing tank 104 and the storage container 102 are transferred to transfer pipes 122 and 12.
4, the mechanical vibration from the refrigerator 106 is not directly transmitted to the storage container 102, and the storage container 1
02 can be significantly suppressed, whereby a noise component caused by the mechanical vibration included in the detection signal of the sensor 114 can be significantly reduced.

The transfer pipes 142 and 144 are connected to the refrigerator 1
In order to suppress the transmission of the mechanical vibration from 06 to the condensing tank 104, it is desirable to attach the condensing tank 104 via a vibration isolating structure. As the vibration isolation structure, for example, a rubber film seal is used, and the transfer pipes 142 and 144 are passed through the film seal.
Can be attached to the tank body 116.

In this embodiment, the condenser 104
A heater 148 and a temperature sensor 150 (see FIG. 2) are arranged in the gas phase section 120 of the gas turbine, for example, in the vicinity of the area where the recondenser 138 is arranged. As understood from the above description, the inside of the container body 108, the inside of the tank body 116, and the first and second flow paths (the transfer pipes 122 and 12).
4) defines a substantially closed circulation space for the liquefied helium gas, and the heater 148 controls the temperature of the liquefied helium gas in this closed cycle. More specifically, in connection with the heater 148, a control means 152 constituted by, for example, a microcomputer is provided.
The detection signal from the temperature sensor 150 is sent to the control means 152, and the control means 152 controls the operation of the heater 148 based on the detection signal from the temperature sensor 150. In this embodiment, as can be understood from FIG. 2, in the closed cycle of the liquefied helium gas, heat intrusion from the outside is caused by the storage vessel 102, the condensation tank 104, and the transfer pipes 122 and 124.
Occurs at On the other hand, it is the cooler 106 that cools the liquefied helium gas. Therefore, the refrigerating capacity R of the cooler 106 is determined by the amount of heat penetration TQ from outside, in other words, the amount of heat penetration Q1 in the storage container 108, the amount of heat penetration Q2 in the condensing tank 104, and the transfer pipes 122 and 124.
And the total heat penetration TQ (T
Q = Q1 + Q2 + Q3) (R> T
Q). In this way, the liquefied helium gas in the closed cycle can be set in a temperature range to be set, for example, 4.2 ±.
The temperature tends to be somewhat lower than the 0.1K range,
By setting the refrigerating capacity of the refrigerating machine 106 in this manner, the refrigerating machine 106 can always be operated with a predetermined refrigerating capacity. When the refrigerator 106 is operated in this manner, the heat balance in the closed cycle of the liquefied helium gas cannot be maintained, so that the heater 148 is operated based on the detection signal from the temperature sensor 150 to apply heat to the closed cycle. Thus, the heat balance of the closed cycle is maintained. By maintaining the heat balance of the closed cycle as described above, the operation of the refrigerator 104 may be always constant, and the operation control thereof is simplified. Further, since the heat balance is maintained by the control of the heater 148, the heat balance can be maintained by a simple control, and the control of the entire cooling device can be simplified.

In such a cooling device, gaseous helium evaporated in the storage vessel 102 flows through the transfer pipe 122 to the gas phase section 120 of the condensing tank 116. Condensing tank 116
Cooled heat medium (liquid helium) from the cooler main body 44 of the cooler 26 is supplied to the recondenser 138 disposed in the gas phase section 120 of the gas phase section 120.
The zero gas helium is cooled, condensed and reliquefied. The heat medium contributing to the cooling is transferred through the transfer pipe 144 to the cooling device main body 1.
40, is re-cooled by the cooler main body 140 and sent to the re-condenser 138. In this way, the transfer pipes 142 and 144 pass between the cooler main body 140 and the re-condenser 138.
Circulated through.

When the liquefied helium gas is liquefied in the condensation tank 104 as described above, the liquid phase 1
The liquid level of 18 rises to be higher than the other end opening of the second flow path, whereby the liquid helium in the liquid phase portion 118 overflows and enters the storage tube 102 through the transfer pipe 124, that is, the second flow path. Flow down. Thus, the evaporated liquefied helium gas is condensed in the condensing tank 104 and then returned to the storage vessel 102. In this way, the liquefied helium gas is transferred between the storage vessel 102 and the condensing tank 104 by the transfer pipe 122,
It is circulated through 124 and is not discharged outside. As described above, the liquefied helium gas does not evaporate and is discharged to the outside, and the temperature of the evaporated liquid helium does not greatly increase, so that it can be efficiently reliquefied and returned to the storage container. it can.

While the embodiment of the cooling device according to the present invention has been described above, the present invention is not limited to such an embodiment, and various modifications and alterations can be made without departing from the scope of the present invention. is there.

For example, in the illustrated embodiment, the present invention is applied to the cooling device for cooling the sensor 114 of the superconducting quantum interferometer. However, the present invention is similarly applied to other cooling devices for maintaining the temperature at a low temperature. be able to. Although liquefied helium gas is used as the low-temperature liquefied gas in the cooling device, other types of cooling devices may use, for example, liquefied nitrogen gas as the low-temperature liquefied gas.

[0030]

According to the cooling device of the first aspect of the present invention,
Since the gas phase of the storage vessel and the gas phase of the condensing tank are communicated via the first flow path, and the recondenser of the refrigerator is disposed in the gas phase of the condensing tank, The low-temperature liquefied gas is condensed in the condensing tank by the action of the re-condenser. The refrigerator is directly connected to the condenser so that mechanical vibrations transmitted from the cooler to the storage vessel can be significantly reduced. Also, since the condensation tank is located above the storage container,
The liquid gas in the condensing tank can be sent to the storage container using gravity, and a dedicated feeding device for sending the liquid gas can be omitted. In addition, by disposing it above, the distance between the storage container and the condensing tank, in other words, the length of the first and second flow paths can be shortened. The amount of heat entering can be reduced. Further, one end of the second flow path is communicated with the gas phase of the storage vessel, and the other end is communicated with the boundary between the liquid phase and the gas phase of the condensation tank. The gas flows down into the storage container by overflow, and the liquefied gas can be circulated with a relatively simple configuration.

According to the cooling device of the second aspect of the present invention, the closed cycle in which the inside of the storage vessel in which the low-temperature liquefied gas is circulated, the inside of the condensing tank, and the first and second flow paths are substantially closed. Since the system is configured, the liquefied gas can be efficiently reliquefied without the low-temperature liquefied gas flowing out or flowing in from the outside.

Further, according to the cooling device of the third aspect of the present invention, the refrigerating capacity R of the refrigerator is larger than the total heat inflow TQ in the cooling device. Is provided with a heater. Therefore, the refrigerator is always operated with the predetermined refrigerating capacity, and the imbalance between the refrigerating capacity R of the refrigerating machine and the total heat inflow amount TQ of the refrigerating apparatus is maintained by controlling the heater, so that the heat balance is relatively simple. With the configuration and simple control, the low temperature liquefied gas can be cooled as required.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an embodiment of a low-temperature liquefied gas cooling device according to the present invention.

FIG. 2 is a diagram schematically showing a storage container, a condensing tank, and the vicinity thereof in the cooling device of FIG.

FIG. 3 is a perspective view for explaining a support state of a storage container and a condensation tank in the cooling device of FIG. 1;

FIG. 4 is a diagram schematically showing an example of a conventional low-temperature liquefied gas cooling device.

FIG. 5 is a diagram schematically showing another example of a conventional low-temperature liquefied gas cooling device.

[Explanation of symbols]

 Reference Signs List 102 storage container 104 condensing tank 106 refrigerator 108 container main body 110, 118 liquid phase part 112, 120 gas phase part 114 sensor 116 tank main body 122, 124, 142, 144 transfer pipe 126 magnetic shield housing 138 recondenser 148 heating heater

Claims (3)

[Claims] A storage container for storing the low-temperature liquefied gas, a condensation tank disposed above the storage container, a first and a second flow path communicating the condensation tank with the storage container, A refrigerator for condensing the gas in the condensing tank, the refrigerator including a recondenser for condensing the gas, wherein the recondenser is disposed in a gas phase portion of the condensing tank, and The gas in the condensing tank is condensed by a vessel, the first flow path communicates the gas phase of the storage vessel with the gas phase of the condensing tank, and the gas in the storage vessel is the first gas. The second flow path communicates with the gas phase part of the storage vessel and the boundary between the liquid phase part and the gas phase part of the condensing tank through the flow path. The liquid in the tank overflows and flows down to the storage container through the second flow path. Temperature liquefied gas cooler. 2. The low temperature as claimed in claim 1, wherein the internal space of the storage container, the internal space of the condensation tank, and the first and second flow paths define a substantially closed circulation space. Liquefied gas cooling device. 3. The refrigerating capacity R of the refrigerator is a sum of a heat penetration amount of the storage container, a heat penetration amount of the condensation tank, and a heat penetration amount of the first and second flow paths. Total heat penetration TQ
(R> TQ), and in this connection, a heater is disposed in the gas phase of the condensing tank, and the refrigerating capacity R of the refrigerator and the total heat intrusion are controlled by controlling the heater. 3. The low-temperature liquefied gas cooling device according to claim 1, wherein a heat balance with the amount is maintained.