JPH0579600A - Method and device for pumping up extremely low temperature liquid - Google Patents

Abstract

PURPOSE:To provide a device and a method for pumping up the extremely low temperature liquid which has the large versatility and in which the consumption of the extremely low temperature liquid can be reduced without deteriorating the workability. CONSTITUTION:The internal pressure of a Dewar 4 which is charged with liquid helium 3 is increased, and the liquid helium 3 is pumped up from the Dewar 4 by utilizing the rise of the internal pressure. The gas generated through the evaporation of the liquid helium 3 accommodated in the Dewar 4 is introduced into a compressor 24 and pressurized, and after the pressurized gas is heated by an electrical heater 27, the gas is returned into te Dewar 4, and then the internal pressure of the Dewar 4 is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic liquid pumping method for increasing the internal pressure of a heat insulating container containing a cryogenic liquid and utilizing this increase in internal pressure to send the cryogenic liquid out of the adiabatic container. Regarding the device.

[0002]

2. Description of the Related Art The main part of a superconducting magnet device is usually one in which a superconducting coil and liquid helium for cooling are housed in a heat insulating container (cryostat). The heat insulating container is devised so as to obtain a good heat insulating function, but it cannot completely prevent heat invasion from the outside. Further, heat enters from the outside through the power lead connecting the superconducting coil and the external power source, or Joule heat generated in the power lead enters the heat insulating container. Therefore, the liquid helium contained in the heat insulation container is
It gradually evaporates and eventually everything is gasified. Therefore, in order to keep the superconducting coil in the superconducting state, it is necessary to replenish the liquid content reduced by gasification.

For this replenishment, there are a method of reliquefying the helium gas drifting in the heat insulating container by a heat exchanger and a method of newly injecting liquid helium into the heat insulating container from the outside. Since the former requires a helium refrigerator, it is used in permanent equipment. On the other hand, the latter is widely used in experimental facilities.

By the way, when newly injecting liquid helium into the heat-insulating container, usually, FIG.
The method shown in is adopted. That is, in the method shown in FIG. 20, the heat insulating container containing the liquid helium 3, that is, the Dewar 4 is arranged near the heat insulating container 2 containing the superconducting coil 1. Then, the inside of the dewar 4 and the inside of the heat insulating container 2 are connected by a transfer tube 5 having a heat insulating structure.

When injecting liquid helium into the heat insulating container 2, first, the valve 7 inserted in the middle of the transfer tube 5 is opened. In this state, high-pressure helium gas is introduced from the high-pressure helium gas cylinder 9 into the upper space in the dewar 4 and the shield tank 8 communicating with this space.
By this introduction, the pressure P ₁ in the deer 4 and the heat insulating container 2
A pressure difference (P ₁ > P ₂ ) from the internal pressure P ₂ is provided, and a part of the liquid helium 3 in the Dewar 4 is injected into the heat insulating container 2 via the transfer tube 5 by this pressure difference. ..

However, such a method has the following problems. That is, the high pressure helium gas cylinder 9
It usually has a weight of 60 kg or more because of restrictions such as standards. Therefore, there is a problem that a great deal of labor and time are required for handling such as installation and replacement. There is also a problem that expensive helium gas is consumed each time the liquid helium 3 is pumped up from within the dewar 4.

On the other hand, in the method shown in FIG.
The electric heater 10 is installed in a position where it is submerged in the liquid helium 3, and by energizing the electric heater 10, a part of the liquid helium 3 is forcibly gasified. I try to increase the pressure.

However, even this method has the following problems. That is, assuming that the electric heater 10 has a capacity of 15 watts, 21 liters of liquid helium evaporates when the electric heater 10 is energized for 1 hour. In the case of immersion cooling a 180 kg superconducting coil, starting injection from room temperature takes 4 hours to complete the injection, and about 320 liters of liquid helium is used.
On the other hand, 84 liters of liquid helium evaporates when the electric heater 10 is energized for 4 hours. As can be seen, about 1/4 of the actually required amount of liquid helium is consumed only for pumping. As described above, this method has a problem that a large amount of liquid helium is consumed.

An electric heater of about 100 V and 200 W is installed in the upper space of the Dewar 4, and the electric heater heats the helium gas existing in the upper space of the Dewar 4 to reduce the density. A method of obtaining the necessary internal pressure by means of is also considered. However, since the withstand voltage of helium gas is extremely low at 500 V per millimeter, it is necessary to strengthen the insulation of the portion located inside the dewar 4. Further, the electric heater of the 200 watt class has a large diameter of the heating element of 2 mm or more and is long, so that it is difficult to install it in the dewar 4 using a hole or the like for inserting the transfer tube 5. Therefore, there is an inconvenience that an electric heater must be installed and fixed for each dewar.

[0010]

As described above, in the conventional so-called cryogenic liquid pumping method and device, not only the workability is poor and there are many restrictions, but also liquid helium, that is, an expensive cryogenic liquid. There was a problem that there was a lot of wasteful consumption of liquid. Therefore, it is an object of the present invention to provide a cryogenic liquid pumping method and apparatus capable of solving the above-mentioned problems.

[0011]

In order to achieve the above object, the present invention increases the internal pressure of a heat insulating container containing a cryogenic liquid, and utilizes this increase in internal pressure to remove the cryogenic liquid from the above. When pumping out from the inside of the heat-insulating container, the gas generated by evaporation of the cryogenic liquid contained in the heat-insulating container is guided to the compression means and pressurized, and the pressurized gas is returned to the inside of the heat-insulating container. As a result, the internal pressure of the heat insulating container is increased.

[0012]

For example, when the cryogenic liquid is liquid helium, the helium gas existing in the heat insulating container is guided to the compression means and pressurized, and then returned to the heat insulating container, whereby the heat insulating container is cooled. Is maintained at the required pressure. Therefore, according to this method, the internal pressure of the heat insulating container can be increased while the consumption of helium gas or liquid helium is suppressed to an extremely small level. Moreover, it is not necessary to install an electric heater in the heat insulating container. Further, a compact and lightweight compressing means is sufficient, and there is no fear of deteriorating workability.

[0013]

Embodiments will be described below with reference to the drawings.

FIG. 1 shows an example in which the present invention is applied to inject liquid helium into a heat insulating container containing a superconducting coil. In this figure, the same parts as those in FIG. 20 are indicated by the same reference numerals. Therefore, detailed description of the overlapping portions will be omitted.

In order to carry out the present invention, the upper space in the dewar 4 and the shield tank 8 leading to this space are connected to the pipe 2.
The suction port of the compressor 24 is connected via 1, 22, and 23. The discharge port of the compressor 24 is connected via a pipe 25 to a gas discharge port 26 formed on the upper wall of the dewar 4. Pipe 2 at the middle of pipe 25 on the outer circumference
An electric heater 27 is provided for heating the helium gas flowing in the chamber 5. A pressure sensor 28 for detecting the internal pressure is attached to the dewar 4. Then, the valve 7, the compressor 24, and the electric heater 27 are controlled by the control device 29 as follows.

When the injection start command is given, the control device 29 first controls the valve 7 to open and then the compressor 24.
Drive start control and electric heater 27 bias start control. The upper limit of the pressure inside the dewar 4 detected by the pressure sensor 28 is 0.14 Kg / cm ^2. , Lower limit 0.09Kg
/ Cm ² The compressor 24 and the electric heater 27 are on / off controlled so as to fall within the range. Further, when the liquid level in the heat insulating container 2 detected by a liquid level sensor (not shown) reaches a predetermined level, the valve 7 is controlled to be closed, the operation of the compressor 24 is stopped, and the electric heater 27 Stop energizing.

Therefore, when the injection start command is given to the control device 29, the compressor 24 starts to operate, and the helium gas existing in the upper space in the dewar 4 and the helium existing in the seal tank 8 are supplied. The gas flows to the suction port of the compressor 24 and is pressurized by the compressor 24. The pressurized helium gas is heated by the electric heater 27 while flowing through the pipe 25. Then, the pressurized and heated helium gas is returned from the gas discharge port 26 to the upper space in the dewar 4. Therefore, the pressure inside the dewar 4 increases.

In this case, since the helium gas returned to the upper space in the dewar 4 is heated by the electric heater 27, it warms the gas drifting in the upper space, and the low temperature drifting in the upper space. The helium gas is rapidly expanded.
Therefore, the internal pressure rises rapidly. At this time, since the valve 7 is held open, a pressure difference is generated between the inside of the dewar 4 and the inside of the heat insulating container 2, and this pressure difference causes the dewar 4 to move.
Liquid helium inside is injected into the heat insulating container 2 through the transfer tube 5. Then, the control device 29
Until the liquid level in the heat insulating container 2 reaches a specified level,
The compressor 24 and the electric heater 27 are controlled so as to maintain the pressure in the dewar 4 between the upper limit and the lower limit described above.

In such a pumping method, the internal pressure of the dewar 4 can be increased while the consumption of helium gas or liquid helium remains small. Moreover, since it is not necessary to install an electric heater in the dewar 4, the control items can be greatly reduced. The total weight of the compressor 24 used is 5 kg.
A small size is enough and it can contribute to the improvement of workability. According to the experiment, the internal pressure of a liquid helium dewar having a capacity of 500 liters was 0.14 kg / cm ² It took 2 minutes to rise to 0.09 Kg / cm ² To 0.14 Kg / cm ² It took 40 to rise to
It was seconds. Therefore, the pumping start-up time can be shortened.

Since the latent heat of vaporization of liquid helium is as small as 5 calories per gram, the gas discharge port 26
If the position is positioned in the liquid helium layer as shown in FIG. 2, part of the liquid helium can be evaporated by the discharged helium gas, and the internal pressure can be further rapidly increased.

FIG. 3 shows a modification in which the present invention is applied to inject liquid helium into a heat insulating container containing a superconducting coil. In this figure, the same parts as those in FIG. 1 are indicated by the same reference numerals. Therefore, detailed description of the overlapping portions will be omitted.

This example is different from the example shown in FIG. 1 in that the control device 29a controls the helium gas from the inside of the dewar 4 and then pressurizes the helium gas.
It is in the structure of the route to return.

In this example, the pipes 21 and 22 leading to the upper space in the dewar 4 and the shield layer 8 are the pipes 2 and 2.
3 and a gas circuit system (not shown) via the solenoid valve 101.

The control device 29a includes the push switch 10
When the injection start command is given by the operation of 2 or the like, first, the valve 7 is controlled to be opened and the electromagnetic valve 101 is controlled to be closed, and then the compressor 24 is started to be driven. In this example, the pressure in the upper space in the dewar 4 is monitored, and the pressure in the dewar 4 is 0.06 to 0.10 kg / cm ² during the time period set by the timer 103 from the start of driving the compressor 24. The rotation speed or voltage of the compressor 24 is controlled so as to fall within the range. Then, after the time limit set by the timer 103 has elapsed, the pressure in the dewar 4 is 0.14 kg / cm ² The rotation speed or voltage of the compressor 24 is controlled so as to be maintained at.
That is, the control device 29a performs two-stage control so that the pressure in the dewar 4 is kept at a relatively low value at the beginning of pumping and is kept at a higher value after a certain period of time. Further, the control device 29a controls the valve 7 to be closed and the solenoid valve 101 to be open when the liquid level in the heat insulating container 2 detected by a liquid level sensor (not shown) has reached a predetermined level, and the compressor 29 The operation of 24 is stopped. On the other hand, a path for sucking the helium gas from the inside of the dewar 4 and thereafter pressurizing and returning the helium gas into the inside of the dewar 4 is configured as shown in FIG.

Reference numeral 104 in the figure denotes a suction port provided on the upper wall of the dewar 4. One end of the transfer tube 5 is inserted into the dewar 4 through the suction port 104. A cylindrical body 105 is connected to the peripheral portion of the suction port 104 so as to extend upward. Cylinder 105
A thread 106 is formed on the outer peripheral surface of the upper end portion, and a step 107 is formed on the inner peripheral surface of the upper end portion.

The peripheral wall of the cylindrical body 105 at an intermediate position in the axial direction is connected to the cylindrical body 105 such that one end of a pipe 108 for sucking up helium gas is connected to the cylindrical body 105. And tube 1
The other end of 08 is connected to the pipe 21 via joint mechanisms 109 and 110. The joint mechanism 11
0 is the pipe 21 when connected to the joint mechanism 109.
Is automatically opened, and the connection port of the pipe 21 is automatically closed when it is detached from the joint mechanism 109.

At the upper part of the cylindrical body 105, a connecting pipe 111 whose inner diameter is larger than the outer diameter of the transfer tube 5 by a predetermined amount.
Are inserted concentrically with the transfer tube 5. An O-ring 112 is mounted between the outer peripheral surface of the lower portion of the connecting pipe 111 and the step portion 107 formed on the cylindrical body 105, and the pressing ring 11 is mounted on the upper surface of the O-ring 112.
3 is applied. A retaining ring 114 is attached to the screw thread 106 formed on the cylindrical body 105, and the O-ring 112 is pressed by the tightening of the retaining ring 114 via the retaining ring 113.
The deformation of 12 maintains the airtightness between the connecting pipe 111 and the cylindrical body 105 and fixes the connecting pipe 111 to the cylindrical body 105.

The step portion 1 is formed on the inner peripheral surface of the lower end portion of the connecting pipe 111.
15 is formed, and one end side of a thin guide tube 116 having an inner diameter substantially equal to that of the connecting pipe 111 is fitted and fixed to the step portion 115. This guide tube 11
The other end of the pipe 6 is provided with a pipe 108 in order to prevent a relative flow between the flow of gas sucked from the Dewar 4 and the flow of gas discharged into the Dewar 4 in the tubular body 105.
It extends down to more than 20 cm away from the entrance.

The transfer tube 5 is the inner tube 5
Since it is formed in a double tube structure in which the vacuum heat insulating layer 5c is provided between the a and the outer tube 5b, the gas discharged into the dewar 4 and the liquid helium flowing in the transfer tube 5 in the guide tube 116. There is almost no heat exchange between and. Therefore, the helium gas flowing through the gap between the guide tube 116 and the transfer tube 5 is not likely to be cooled.

On the peripheral wall of the connecting pipe 111 at the midway position in the axial direction,
One ends of the pipes 117 and 118 are connected so as to communicate with the inside of the connection pipe 111. The other end of the pipe 117 is connected to the pipe 25 via joint mechanisms 119 and 120. The other end of the pipe 118 is connected to the joint mechanism 12
It is connected to a pipe 123 for pressure measurement via 1 and 122. The other end of the pipe 123 communicates with the pressure sensor in the control device 29a described above. The joint mechanisms 120 and 122 are the joint mechanisms 119 and 121.
The connection port of the corresponding pipe is automatically released when the connection mechanism is connected to the connection mechanism, and the connection port of the corresponding pipe is automatically closed when the connection mechanism is disconnected from the joint mechanism 119, 121.

A screw thread 1 is formed on the outer peripheral surface of the upper end of the connecting pipe 111.
24 is formed, and a step portion 12 is formed on the inner peripheral surface of the upper end portion.
5 is formed. Between the outer peripheral surface of the transfer tube 5 and the step portion 125 formed in the connection pipe 111, O
A ring 126 is attached, and a holding ring 127 is applied to the upper surface of the O-ring 126. And, a retaining ring 128 is attached to the screw thread 124,
By tightening the retaining ring 128, the O-ring 126 is pressed via the pressing ring 127, and the O-ring 126 is deformed due to this pressing, so that the transfer tube 5 and the connecting pipe 111 are kept airtight and to the connecting pipe 111. The transfer tube 5 is fixed.

With such a configuration, the control device 29a
When the injection start command is given to the valve 7, the valve 7 is controlled to be opened and the electromagnetic valve 101 is controlled to be closed. At the same time, the compressor 24 starts operating and the helium gas and the sealing layer existing in the upper space in the dewar 4 are controlled. The helium gas existing inside 8 flows to the suction port of the compressor 24 and is pressurized by the compressor 24. That is, the helium gas drifting in the upper space of the dewar 4 enters between the guide tube 116 and the cylindrical body 105 as shown by the solid arrow 129 in FIG.
It flows through the pipe 108 to the pipe 21. Then, the helium gas pressurized by the compressor 24 flows into the annular space after being formed between the connection pipe 111 and the transfer tube 5 after passing through the pipe 25 and the pipe 117 as shown in FIG. Transfer tube 5 and guide tube 11
6 and flows into the Dewar 4 from the discharge port 130. Therefore, the pressure inside the dewar 4 starts to rise. Thus, when the pressure inside the dewar 4 rises, part of the liquid helium 3 inside the dewar 4 is transferred into the heat insulating container 2 through the transfer tube 5 by this pressure. Therefore, the same effect as that of the above-mentioned embodiment can be exhibited.

In this example, in order to prevent a relative flow between the flow of the gas sucked from the Dewar 4 and the flow of the pressurized gas discharged into the Dewar 4 in the cylindrical body 105, The inlet 108 and the outlet 130 do not exist in the same cylindrical body 105, and the distance H between the inlet of the pipe 108 and the outlet 130 is 20 cm or more. H
Is short, it takes time to raise the pressure, but it is longer than the length of the cylinder 105 as in this example, for example,
If they are separated by 20 cm or more, the rise can be started in a short time.

Further, in this example, the control device 29a
Opens the pipe 123 to monitor the upper space pressure in the dewar 4, and the pressure in the dewar 4 is 0.06 to 0.06 during the time period set by the timer 103 from the start of driving the pressure machine 24.
0.10Kg / cm ² The rotational speed or voltage of the compressor 24 is controlled so as to be within the range of, and after the time set by the timer 103 has elapsed, the pressure in the dewar 4 is 0.14 kg / cm.
² The rotation speed or voltage of the compressor 24 is controlled so as to be held at. Therefore, the flow rate of liquid helium transferred into the heat insulating container 2 is small at the start of pumping and increases after a certain time has elapsed. Therefore, it is possible to inject liquid helium into the heat insulating container 2 while suppressing the consumption of liquid helium. That is, initially, the temperature of the superconducting coil 1 has risen to near room temperature. Since the latent heat of vaporization of liquid helium is as small as 5 calories per gram as described above, the liquid helium that touches the superconducting coil 1 is instantly vaporized. In particular, the copper material forming a part of the superconducting coil 1 does not have a large thermal conductivity unless it becomes 100 K or less. Therefore, even if the injection amount of liquid helium is increased from the initial stage, most of it is evaporated. In order to pour the superconducting coil 1 with the consumption amount of liquid helium suppressed to the minimum, it is a good idea to gradually cool it. As in this example, the flow rate can be reduced in the initial stage and increased from the time when a certain period of time has elapsed, whereby efficient injection can be achieved.

Further, in this example, the joint mechanisms 110, 120, 122 having a function of automatically releasing when connected and automatically closing when disconnected are used to connect to the pipes 21, 25, 123. Since this is done, even in the case of disassembling to switch to another dewar, the pipes 21, 25 and 123 are filled with helium gas and air can be prevented from entering.
For this reason, it is possible to prevent a problem that is likely to occur when air is mixed, that is, to prevent contamination of helium gas, and moisture in the mixed air is frozen in the outlet 130 or the like to cause pressurization failure, or a pipe is blocked. Can be prevented.

The joint mechanisms 110, 120 and 122 for achieving the intended purpose are SP-V type couplers (2SP-V type, 3SP-type) manufactured by Nitto Kohki Co., Ltd.
V type, 4SP-V type) or the like may be used.

Further, in this example, when the control device 29a is operated, the control device 29a closes the electromagnetic valve 101 leading to the gas recovery system. Therefore, the pumping can be completely automated by remote control. Therefore, the pumping work can be safely performed without approaching the superconducting coil 1.

Further, in this example, the thin guide tube 116 is coaxially connected to the lower end of the connecting tube 111, and the outer diameter of the guide tube 116 is smaller than the outer diameter of the connecting tube 111. Therefore, the O-ring 112 inserted between the connecting pipe 111 and the cylindrical body 105 does not come into contact with the guide pipe 116 cooled to a cryogenic temperature. Therefore, it is possible to prevent the plastic deformation of the O-ring 112 due to the heat transfer from the guide pipe 116, and as a result, it is possible to prevent the connection pipe 111 from being difficult to pull out during disassembly.

FIG. 5 shows a modification of the structure shown in FIG. 4 in which the flow process of helium gas is reversed. That is, the suction port 104 in FIG. 4 is the discharge port in FIG. 5, and the discharge port 130 is the suction port in the same manner. Further, along with this change, the positions of the pressure measuring pipe 123, the joint mechanisms 121 and 122, and the pipe 118 communicating with the pressure sensor in the control device 29a are changed, and the pipe 118 becomes the cylindrical body 105.
Is connected to the peripheral wall at an axially intermediate position. However, these positions are not limited to the positions shown in the drawing, and may be provided at any positions as long as the internal pressure of the dewar 4 can be accurately measured. In FIG. 5, the same parts as those in FIG. 4 are indicated by the same reference numerals. Therefore, detailed description of the overlapping portions will be omitted. FIG. 6 shows a modified example of the structural portion used for implementing the present invention, in which a portion corresponding to FIG. 4 is shown. In this figure, elements corresponding to those shown in FIG. 4 are designated by the same reference numerals. Therefore, detailed description of the overlapping portions will be omitted.

This example differs from the example shown in FIG. 4 in that the elements necessary for sucking up the helium gas drifting in the upper space in the dewar 4, compressed helium gas, is returned to the upper space in the deur 4. This is because all the elements required for the above and the elements required for pressure measurement are provided on the side of the connecting pipe 111a.

That is, the transfer tube 5 is
It penetrates the eccentric position in the connection pipe 111a. Connection tube 1
The inner surface of the peripheral wall 11a and the transfer tube 5
This connecting pipe 111a is provided at a position where the distance between
One ends of the pipes 117 and 118 are connected to each other so as to communicate with each other. Further, an oblique through hole 131 is formed at a position where the distance between the inner surface of the connection pipe 111a and the transfer tube 5 is long on the peripheral wall of the connection pipe 111a. This through hole 13
One end of a pipe 132 is connected to 1 in an airtight manner. The other end of the pipe 132 is connected to the joint mechanism 109. One end of the pipe 132 is connected to the joint mechanism 109, and the other end of the pipe 132 extends downward in a space existing between the inner surface of the connection pipe 111a and the transfer tube 5, and the tip 133 thereof is connected to the dewar 4. A tube 134 made of tetrafluoroethylene located in the upper space is provided. It should be noted that the tube 134 discharges the tip portion 133 and the tube 117 so that the flow of the pressurized (discharge) gas and the flow of the sucked gas do not become a relative flow in the cylindrical body 105a or the connection pipe 111a. 2 distance from exit
The length is set to be 0 cm or more. Further, in this example, since the transfer tube 5 is eccentrically arranged with respect to the connection pipe 111a, the step portion 125 and the O-ring 12 are arranged.
An O-ring 135 and an intermediate ring 136 are interposed between the No. 6 and.

With this structure, it is not necessary to provide an element necessary for pressurization on the cylindrical body 105a, so that various dewars can be dealt with immediately and the easiness of handling can be improved.

FIG. 7 shows a modification of the structure shown in FIG. 6 in which the flow process of helium gas is reversed. That is, the suction port 133 in FIG. 6 is the discharge port in FIG. 7, and the discharge port 104 is the suction port in the same manner. Further, along with this change, the positions of the pressure measuring pipe 123, the joint mechanisms 121 and 122, and the pipe 118, which communicate with the pressure sensor in the control device 29a, are changed, and the pipe 108 becomes the Dewar 4
Is attached to the upper wall. However, these positions are not limited to the positions shown in the drawing, and may be provided at any positions as long as the internal pressure of the dewar 4 can be accurately measured. In FIG. 7, the same parts as those in FIG. 6 are indicated by the same reference numerals. Therefore, detailed description of the overlapping portions will be omitted.

Next, the relationship between the pressure increase in the Dewar and the pressurization time when the structure shown in FIGS. 4 and 6 is used will be described. FIG. 8 is a graph showing the experimental results regarding the relationship between the pressure increase in the Dewar and the pressurization time. The experiment was performed on a liquid helium dewar with a volume of 500 liters. In the figure, A is the result when the structure shown in FIG. 4 is used, and B is the result when the structure shown in FIG. 6 is used.

According to the structure shown in FIG. 4, the pressure inside the dewar 4 is 0.14 kg / cm ² capable of transferring the liquid helium 3. It takes about 1 minute to reach, while the structure shown in FIG. 6 requires about 10 minutes. This is considered to be due to the following reasons.

In the structure shown in FIG. 6, the cryogenic helium gas is sucked from the suction port 133 in the vicinity of the liquid surface of the liquid helium 3 in the dewar 4, is compressed to about room temperature, and is then discharged from the discharge port 104. It is discharged to the upper space in the dewar 4 having a relatively low helium gas density. Therefore, it is considered that a large density change (pressure increase) in the dewar of helium gas is unlikely to occur.

On the other hand, according to the structure shown in FIG.
Helium gas is sucked from the upper space in the dewar 4 through the suction port 104, and the pressurized helium gas is discharged to the cryogenic helium gas space from the discharge port 130 provided immediately above the liquid surface of liquid helium. .. It is considered that this causes liquid helium, which has a low latent heat of vaporization, to vaporize rapidly from the surface of the liquid, resulting in a large density change (pressure increase).

Therefore, it is considered most effective to release the pressurized helium gas into the liquid helium having a small latent heat of vaporization in order to cause a more drastic change in density.

9 to 11 show a structure based on the structure shown in FIGS. 4 and 6 in which pressurized helium gas is discharged into the liquid helium. Here, the respective discharge ports 130 and 133 are connected to the dewar 4
It extends near the bottom. As a result, even when liquid helium is consumed and the liquid level is lowered, it is possible to effectively utilize the density change due to evaporation of liquid helium. In other words, when pumping liquid helium, the process shown in FIGS.
The example shown in 1 is considered to be the most efficient structure.

However, practically, the pressure increase caused by releasing the pressurized helium gas into the cryogenic helium gas space immediately above the liquid surface of the liquid helium 3 is sufficient as in the structure shown in FIG. 3 or 7. The intended purpose can be achieved.

In the above embodiment, liquid helium is used as the cryogenic liquid, but it goes without saying that it can be applied to pumping out other cryogenic liquids such as liquid nitrogen and liquid oxygen. FIG. 12 shows a transfer tube 31 suitable for transferring a cryogenic liquid. The transfer tube 31 is a cryogenic liquid contained in the Dewar 32,
For example, it is used when transferring liquid helium 33 into another heat insulating container, for example, the heat insulating container 34 accommodating the superconducting coil 34.

Since the latent heat of vaporization of liquid helium is as small as 5 calories per gram, it easily evaporates if heat enters from the outside during transfer. For this reason, this type of transfer tube usually has a double-tube structure consisting of an inner tube that allows liquid helium to flow therethrough and an outer tube that is arranged outside it, and a vacuum heat insulation is provided between the inner tube and the outer tube. Layers are provided.
The presence of the vacuum insulation layer suppresses evaporation of liquid helium.

However, the vaporization of liquid helium caused by heat intrusion due to heat conduction from the outer tube cannot be ignored, and generally the transfer efficiency is low. In particular, in this type of transfer tube, a fitting type connecting portion is provided on the way, but a large amount of heat is transferred to liquid helium by heat conduction from the outer tube at this connecting portion. In order to reduce the amount of heat transfer, it is necessary to set the axial length of the connecting portion to be long, which inevitably leads to lengthening of the whole. In addition, when transferring liquid helium from one heat insulating container to the other heat insulating container using a transfer tube, normally,
It is necessary to insert one end of the transfer tube into liquid helium in one heat insulation container. Therefore, there is also a problem that the external heat is transmitted to the liquid helium through the outer tube of the transfer tube, and the evaporation amount of the liquid helium is inevitably increased.

The transfer tube 31 shown in FIG. 12 can contribute to solving the above-mentioned problems.
This transfer tube 31 is the first tube 3
7 and the second tube 38 are connected by a connecting portion 39.

The tube 37 includes an inner tube 40 made of stainless steel, an outer tube 41 arranged so as to cover the inner tube 40, and a vacuum formed between the inner tube 40 and the outer tube 41. It is composed of a heat insulating layer 42. Similarly, the tube 38 is also made of stainless steel, an inner tube 43, an outer tube 44 arranged to cover the inner tube 43, and a vacuum heat insulation formed between the inner tube 43 and the outer tube 44. And layer 45. The tube 37 is provided so as to hermetically penetrate the upper wall of the dewar 32 such that the tip end opening portion 46 on one end side thereof is located in the liquid helium 33 in the dewar 32. In addition, the tube 38 has a heat-insulating container 3 so that a tip opening 47 on one end side thereof is located in the heat-insulating container 35.
5 is provided so as to penetrate airtightly through the upper wall. Then, the other end side of the tube 37 and the other end side of the tube 38 are connected by a fitting type connection portion 39.

The connecting portion 39 includes a male portion 48 formed by reducing the outer diameter of the other end of the tube 37, a female portion 49 formed by increasing the inner diameter of the other end of the tube 38, and a female portion 49. It is composed of a seal ring 50 which seals an annular gap existing between the male part 49 and the male part 49 when the male part 49 is fitted to the part 49.

On the other hand, the outer tube 4 constituting the tube 37
As shown in FIG. 13, in No. 1, the portion close to the male portion 48 and the portion located in the upper space in the dewar 32 are formed by ceramic tubes 51 and 52 made of alumina or the like having a low thermal conductivity. Similarly, in the inner tube 43 forming the tube 38, a part of the portion forming the female portion 49 is formed of the ceramic tube 53. Further, the outer tube 44 constituting the tube 38 is formed by a ceramic tube 54 at a part of the portion located inside the heat insulating container 35. In FIG. 12, reference numeral 55 denotes a valve.

Thus, the transfer tube 31
If a ceramic tube is placed in the middle of the process, especially in the area where heat is likely to enter from the outside, the thermal conductivity of stainless steel will be 8
It is 21W / m ・ for ceramic compared to 4W / m ・ k
Since k is small, it is possible to suppress heat intrusion from the outside and improve transfer efficiency.

According to the experiment, the transfer tube 31 shown in FIG. 12 was used and the internal pressure of the dewar 32 was 0.14 kg / cm ^2. When liquid helium 33 was transferred to the heat insulating container 35 by setting the above condition, it took 12 minutes to store 50 liters in the heat insulating container 35 as shown by the solid line in FIG. Therefore, the transfer efficiency is 85%. on the other hand,
When a ceramic tube of alumina or the like was not present and the transfer tube was transferred under the same conditions under other conditions, it took 20 minutes as indicated by a broken line in FIG. The transfer efficiency at this time is 65%. in this way,
Transfer efficiency can be improved by interposing a ceramic tube. Further, the axial length of the connecting portion 39 can be made shorter than that of the existing one, which can contribute to shortening of the transfer tube.

FIG. 15 shows a means for preventing the piping leading to the heat insulating container from being blocked by the solidification of water, nitrogen, oxygen, etc. contained in the air which is about to enter the heat insulating container.

In the heat insulating container for accommodating the superconducting coil, a pipe for protecting a power lead for energizing the superconducting coil, a pipe for protecting measurement lines such as pressure, temperature and strain, and helium gas are usually provided. Many pipes such as a pipe for collecting and a pipe for cooling the shield are provided. The main material of the piping is stainless steel, and aluminum is also used. Air may flow through these pipes depending on the situation. Incoming air (moisture, nitrogen, oxygen)
It easily touches the pipe cooled with cryogenic helium gas and solidifies.

In this case, the metal pipe has poor wettability.
For this reason, the attached water is solidified in a hemispherical shape like a polka dot. In many cases, these coagulated substances collect and block the pipe. If the helium gas recovery pipe is closed, the internal pressure of the heat insulating container rises, which may damage the heat insulating container. In addition, for example, when a liquid nitrogen shield tank is provided around the heat insulating container, when liquid helium is introduced into the heat insulating container, part of the liquid nitrogen in the shield tank solidifies, and only this solidified portion The pressure inside the shield tank is reduced. Due to this pressure reduction, air easily flows in through the pipe connected to the shield tank. When air tries to flow in,
Moisture and the like contained therein are solidified on the inner surface of the pipe.
For this reason, the pipe is blocked, and thereafter liquid nitrogen cannot be flown into the shield tank, which may increase evaporation of liquid helium in the heat insulating container.

Therefore, in the example shown in FIG. 15, means for preventing the blockage of the pipe, which is likely to be caused by the inflow of air, is provided. In the example shown in FIG. 15, a pipe 66 connected to a liquid nitrogen shield tank 65 arranged via a vacuum heat insulating layer 64 is closed outside a heat insulating container 63 containing a superconducting coil 61 and liquid helium 62. Are prevented.

Inside the pipe 66, as shown in FIG. 16, a tetrafluoroethylene pipe 67 is mounted. That is, the portion of the pipe 66 has a double pipe structure, and the ethylene tetrafluoride pipe 67 is located inside. Then, these double pipes are connected to a gas recovery pipe 69 via an adsorption tank 68 containing an adsorbent such as activated carbon or molecular sieve, and these recovery pipes 69 are respectively opened to the atmosphere via a valve 70. ..

With such a structure, the shield tank 65
When liquid helium 62 is introduced into the heat insulating container 63 in a state where the liquid nitrogen 71 is accommodated therein and the valve 70 is closed, the liquid nitrogen 71 in the shield tank 65 is transmitted by transmission or the like.
Is cooled and part is solidified. This solidification reduces the pressure in the shield tank 65, which causes the valve 70
Air flows in from the connection part of. A part of water contained in the inflowing air when it passes through the adsorption tank 68 is removed, and then the air flows into the tetrafluoroethylene pipe 67. At this time, the inner surface of the tetrafluoroethylene tube 67 is cooled to an extremely low temperature. Therefore, the water contained in the air that has flowed in adheres to the inner surface of the tetrafluoroethylene tube 67 and solidifies.
In this case, since the tetrafluoroethylene tube 67 has good wettability, the attached water spreads in a thin film and is attached, and is solidified in this state. Therefore, the tetrafluoroethylene pipe 67, that is, the pipe 66 is not blocked by the solidification of water.

Although the above is an example applied to the piping of the shield tank, it is needless to say that it can also be applied to the piping leading to the main heat insulating container. Also, instead of using a tetrafluoroethylene tube,
A coating layer of ethylene tetrafluoride may be applied. In addition, as shown by 72 in the figure, the adsorption tank 68 is provided with a cooling pipe.
May be cooled to about 77 K to improve the adsorption efficiency of water, nitrogen, oxygen, etc. in the adsorption tank 68.

In FIG. 17, a plurality of heat insulating containers 83a respectively containing a superconducting coil 81 and liquid helium 82,
A means for eliminating a problem that occurs when the gas recovery pipes 84a and 84b of 83b are commonly connected to a gas bag or a helium refrigerator 85 is shown. When the gas recovery pipes of a plurality of heat-insulating containers respectively containing superconducting coils and liquid helium are connected to a gas bag or a helium refrigerator in common, when one superconducting coil is quenched, other superconducting coils are also quenched due to the effect. There is. That is, when a certain superconducting coil is quenched, this superconducting coil
Heat is generated by (square of current) × (resistance value in normal conduction state).
Due to this heat generation, the surrounding liquid helium is evaporated and the high-pressure helium gas is filled in the heat insulating container. This high-pressure helium gas moves into another heat insulating container through the gas recovery pipe. Therefore, the temperature in the other heat insulating container rises, liquid helium in the other heat insulating container evaporates, and eventually the superconducting coil in the other heat insulating container also quenches in a chain reaction.

Therefore, in the example shown in FIG. 17, the gas recovery pipes 84a and 84b are connected to the helium refrigerator 85 via the common pipe 86, and the gas recovery pipes 84a and 84b are connected.
The valves 87a and 87b, which are electromagnetic valves and spring return type electromagnetic valves, are interposed in the 84b. And
Safety valves 88a and 88b are attached to the heat insulating containers 83a and 83b, pressure sensors 89a and 89b are attached, and when the detected values of the pressure sensors 89a and 89b are about to exceed a certain value, the corresponding valves are controlled by the controllers 90a and 90b. 87a and 87b are controlled to be closed.

Therefore, when the superconducting coil 81 in the heat insulating container 83a is now quenched and the pressure in the heat insulating container 83a rises above a certain value due to this quench, the controller 90a operates and the valve 87a is controlled to be closed. It Therefore, high-temperature, high-pressure helium gas can be prevented from moving into the heat insulating container 83b, and the quenching of the superconducting coil 81 in the heat insulating container 83b can be prevented. Then, when the pressure inside the heat insulating container 83a further rises, the safety valve 88a operates and the high temperature and high pressure helium gas inside the heat insulating container 83a is released into the atmosphere to prevent the heat insulating container 83a from being damaged. As described above, quenching can be prevented from occurring in a chain reaction.

FIG. 18 shows a modification. In this example, the three-way valve 91 is interposed between the gas recovery pipes 84a, 84b and the common pipe 86, and the pressure sensors 89a,
The output of 89b is introduced into the decision circuit 92. And
The judgment circuit 92 judges which pressure in the heat-insulated container has risen, and this output is introduced into the controller 93.
The three-way valve 91 is switched and controlled so that the heat-insulating container whose pressure has risen is disconnected, and only the heat-insulating container having a normal pressure is connected to the helium refrigerator 85. Therefore, for example, when the superconducting coil 81 in the heat insulating container 83a is quenched and the pressure in the heat insulating container 83a rises due to this quench, the three-way valve 91 is switched as shown in FIG. Helium refrigerator 8
Separated from 5. This prevents the chain reaction of quench from occurring. The above example is an example in which there are two heat insulating containers, but in the case where the number exceeds three, it can be easily realized by adopting the method shown in FIG.

[0071]

As described above, according to the present invention, the internal pressure of the heat insulation container containing the cryogenic liquid is not consumed without the consumption of the cryogenic liquid or its gas and without the electric heater provided inside. The internal pressure can be raised by a compact and lightweight compressor, which can contribute to the improvement of workability.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of a cryogenic liquid pumping method according to the present invention.

FIG. 2 is a diagram for explaining a modified example of the embodiment of the cryogenic liquid pumping method according to the present invention.

FIG. 3 is a view for explaining another embodiment of the cryogenic liquid pumping method according to the present invention.

FIG. 4 is a diagram showing a specific configuration example for realizing the above implementation.

FIG. 5 is a diagram showing a modified example of a specific configuration for realizing the above implementation.

FIG. 6 is a diagram showing another specific configuration example for realizing the above implementation.

FIG. 7 is a diagram showing a modified example of another specific configuration for realizing the above implementation.

FIG. 8 is a diagram showing the relationship between the internal pressure of a liquid helium container and the pressurization time.

FIG. 9 is a diagram for explaining a modified example of another embodiment of the cryogenic liquid pumping method according to the present invention.

FIG. 10 is a diagram showing another modified example of the specific configuration for realizing the above implementation.

FIG. 11 is a diagram showing another modified example of another specific configuration that realizes the above-described embodiment.

FIG. 12 is a schematic configuration diagram of a transfer tube.

FIG. 13 is a cross-sectional view showing the transfer tube taken out locally.

FIG. 14 is a view showing the transport characteristics of the transfer tube in comparison with that of a known transfer tube.

FIG. 15 is a view showing a blockage preventing means for a pipe connected to a heat insulating container.

FIG. 16 is a sectional view showing a pipe taken out locally.

FIG. 17 is a view showing a means for preventing quench from occurring in a chain reaction.

FIG. 18 is a view showing another means for preventing quench from occurring in a chain reaction.

FIG. 19 is a diagram for explaining the operation of the means shown in FIG.

FIG. 20 is a view showing a known example of a cryogenic liquid pumping method.

FIG. 21 is a view showing another known example of a cryogenic liquid pumping method.

[Explanation of symbols]

1 ... Superconducting coil, 2 ... Insulation container, 3 ... Liquid helium,
4 ... Dewar, 5 ... Transfer tube, 7 ... Valve, 8 ... Shield tank, 24 ... Compressor, 26 ... Gas inlet, 27 ... Electric heater, 28 ... Pressure sensor, 29, 29
a ... Control device.

Claims (7)

[Claims] 1. An internal pressure of a heat insulating container containing a cryogenic liquid is increased, and when the internal pressure is pumped out from the inside of the heat insulating container by utilizing the increase of the internal pressure, the inside of the heat insulating container is contained. The gas generated by the evaporation of the cryogenic liquid is introduced into a compression unit to be pressurized, and the pressurized gas is returned into the heat insulating container to increase the internal pressure of the heat insulating container. Cryogenic liquid pumping method. 2. The cryogenic liquid pumping method according to claim 1, wherein the gas pressurized by the compression means is heated to raise the temperature and then returned to the inside of the heat insulating container. .. 3. The cryogenic liquid pumping method according to claim 1, wherein the gas pressurized by the compressing means is returned to the cryogenic liquid layer in the heat insulating container. 4. The internal pressure of the heat insulating container is increased stepwise toward a target pressure.
The method for pumping a cryogenic liquid according to 1. 5. The heat insulating container and the compression means are detachable, and when the heat insulating container and the compression means are attached and detached, the entire compression means is a gas generated by evaporation of the cryogenic liquid. 2. The cryogenic liquid pumping method according to claim 1, wherein 6. A cryogenic liquid pumping apparatus for pumping the cryogenic liquid from an adiabatic container containing the cryogenic liquid,
Compressing means for pressurizing a gas generated by evaporation of the cryogenic liquid in the heat insulating container, a pumping port provided for guiding the gas to the compressing means, and the electrode pressurized by the compressing means. A cryogenic liquid pumping apparatus having a discharge port provided to return the low temperature liquid gas to the heat insulating container. 7. A position at which the gas guided from the inside of the heat insulating container to the suction port and the pressurized gas returned from the discharge port into the heat insulating container do not cause a relative flow. The cryogenic liquid pumping apparatus according to claim 5, wherein the suction port and the discharge port are provided.