JP2712096B2 - Cryogenic liquid pumping method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for pumping a cryogenic liquid, which raises the internal pressure of an insulated container containing the cryogenic liquid, and discharges the cryogenic liquid from the inside of the insulated container by utilizing the increase in the internal pressure. Related to the device.

[0002]

2. Description of the Related Art A main part of a superconducting magnet device is usually a superconducting coil and a liquid helium for cooling contained in a heat insulating container (cryostat). Although the heat insulating container is devised so as to obtain a good heat insulating function, it cannot completely prevent heat from entering from the outside. Further, heat enters the heat insulating container from the outside via a power lead connecting the superconducting coil and an external power supply, or Joule heat generated by the power lead enters. For this reason, the liquid helium contained in the insulated container is
It evaporates slowly and eventually everything gasifies. Therefore, in order for the superconducting coil to maintain the superconducting state, it is necessary to replenish the liquid reduced by gasification.

There are two types of replenishment: a method of reliquefying helium gas floating in an insulated container with a heat exchanger, and a method of newly injecting liquid helium from outside into the insulated container. 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 and the like.

[0004] By the way, when newly injecting liquid helium into an insulated container, normally, FIG. 20 or FIG.
The method shown in FIG. That is, in the method shown in FIG. 20, a heat insulating container containing liquid helium 3, that is, a dewar 4, is placed 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 communicated by a transfer tube 5 having a heat insulating structure.

When injecting liquid helium into the heat insulating container 2, first, a valve 7 inserted in 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.
With this introduction, the pressure P ₁ in the deer 4 and the insulation container 2
A difference (P ₁ > P ₂ ) is provided between the pressure P ₂ and the internal pressure P _2, 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 the pressure difference. .

However, such a method has the following problems. That is, the high-pressure helium gas cylinder 9
Usually, it has a weight of 60 kg or more due to restrictions such as standards. Therefore, there has been 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 every time the liquid helium 3 is pumped from the dewar 4.

On the other hand, in the method shown in FIG.
An electric heater 10 is installed at a position where the liquid helium 3 is submerged in the liquid helium 3, and a part of the liquid helium 3 is forcibly gasified by energizing the electric heater 10, and the gas pressure in the dewar 4 The pressure is raised.

However, even this method has the following problems. That is, assuming that the capacity of the electric heater 10 is 15 watts, 21 liters of liquid helium is evaporated by energizing the electric heater 10 for one hour. In the case of immersion cooling of a 180 kg superconducting coil, it takes 4 hours to start injection from room temperature, and about 320 liters of liquid helium is used.
On the other hand, 84 liters of liquid helium evaporates by energizing the electric heater 10 for 4 hours. As can be seen, nearly one-fourth of the liquid helium actually required is consumed for pumping only. Thus, this method has a problem that the consumption of liquid helium is large.

An electric heater of about 100 volts and 200 watts is installed in the upper space of the dewar 4, and the helium gas existing in the upper space of the dewar 4 is heated by the electric heater to reduce the density. A method of obtaining a necessary internal pressure by using such a method has also been considered. However, since the withstand voltage of helium gas is extremely low at 500 volts per millimeter, it is necessary to strengthen the insulation of the portion located in the dewar 4. Further, since the diameter of the heating element of the 200-watt-class electric heater is as thick as 2 mm or more and long, it is difficult to install the electric heater in the dewar 4 using a hole for inserting the transfer tube 5 or the like. For this reason, there is an inconvenience that an electric heater must be installed and fixed for each dewar.

[0010]

As described above, the conventional cryogenic liquid pumping method and apparatus are not only poor in workability and have many restrictions but also liquid helium, that is, expensive cryogenic liquid. There was a problem that wasteful consumption of liquid was large. Therefore, an object of the present invention is 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 raises the internal pressure of a heat insulating container containing a cryogenic liquid, and utilizes the increase in the internal pressure to convert the cryogenic liquid into the liquid. In pumping out 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 into the heat insulating container. Thereby, the internal pressure of the heat insulating container is increased.

[0012]

For example, when the cryogenic liquid is liquid helium, the helium gas present in the heat insulating container is guided to the compression means and pressurized, and then returned to the heat insulating container. Is maintained at the required pressure. Therefore, according to this method, it is possible to increase the internal pressure of the heat-insulating container with the consumption of helium gas or liquid helium extremely suppressed. Also, there is no need to install an electric heater in the heat insulating container. Further, a compact and lightweight compression means is sufficient, and there is no possibility that the workability is deteriorated.

[0013]

Embodiments will be described below with reference to the drawings.

FIG. 1 shows an example in which liquid helium is injected into an insulated container housing a superconducting coil by applying the present invention. In this figure, the same parts as those in FIG. 20 are indicated by the same reference numerals. Therefore, a detailed description of the overlapping part will be omitted.

In order to carry out the present invention, an upper space in the dewar 4 and a shield tank 8 communicating with 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 to a gas discharge port 26 formed on the upper wall of the dewar 4 via a pipe 25. In the middle of the pipe 25, the pipe 2
An electric heater 27 for heating the helium gas flowing in the inside 5 is provided. The dewar 4 is provided with a pressure sensor 28 for detecting an internal pressure. The valve 7, the compressor 24 and the electric heater 27 are controlled by the control device 29 as follows.

When an injection start command is given, the control device 29 first controls the valve 7 to open, and then controls the compressor 24
And the energization start control of the electric heater 27 are executed. The pressure in the dewar 4 detected by the pressure sensor 28 is 0.14 kg / cm ^{2 at the} upper limit. , Lower limit 0.09Kg
/ Cm ² The compressor 24 and the electric heater 27 are turned on and off so as to fall within the range. 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 and the operation of the compressor 24 is stopped. Stop energizing.

Therefore, when an injection start command is given to the controller 29, the compressor 24 starts operating, and the helium gas present in the upper space in the dewar 4 and the helium gas present in the seal tank 8 are provided. Gas flows to a 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. For this reason, the pressure in the dewar 4 increases.

In this case, the helium gas returned to the upper space in the dewar 4 is heated by the electric heater 27, so that the gas floating in the upper space is heated and the low-temperature gas floating in the upper space is heated. Helium gas is rapidly expanded.
Therefore, the internal pressure rises rapidly. At this time, since the valve 7 is kept open, a pressure difference occurs between the inside of the dewar 4 and the inside of the heat insulating container 2.
The liquid helium inside is injected into the heat insulating container 2 via the transfer tube 5. And the control device 29
Until the liquid level in the heat insulating container 2 reaches a predetermined 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 is kept small. Further, since there is no need to install an electric heater in the dewar 4, the number of control items can be greatly reduced. The compressor 24 used has a total weight of 5 kg.
A small size is sufficient and can contribute to improvement of workability. According to experiments, the internal pressure of a liquid helium dewar having a capacity of 500 liters was set to 0.14 kg / cm ^2. It took 2 minutes to rise to 0.09 kg / cm ² From 0.14Kg / cm ² 40 minutes to climb
Seconds. Therefore, the pumping start-up time can also 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 located in the liquid helium layer as shown in FIG. 2, a part of the liquid helium can be evaporated by the discharged helium gas, and the internal pressure can be more rapidly increased.

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

This example is different from the example shown in FIG. 1 in the control mode of the control device 29a and the fact that helium gas is sucked from the inside of the dewar 4 and then pressurized to dewar.
And the structure of the return path.

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

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

In the figure, reference numeral 104 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 periphery 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 portion 107 is formed on the inner peripheral surface of the upper end portion.

One end of a pipe 108 used for sucking up helium gas is connected to a peripheral wall of the cylinder 105 at an intermediate position in the axial direction so as to communicate with the inside of the cylinder 105. And tube 1
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
The connection port of the pipe 21 is automatically closed, and the connection port of the pipe 21 is automatically closed when detached from the joint mechanism 109.

A connection pipe 111 having an inner diameter larger than the outer diameter of the transfer tube 5 by a predetermined amount is provided at an upper portion in the cylindrical body 105.
Are inserted concentrically with the transfer tube 5. An O-ring 112 is mounted between a lower outer peripheral surface of the connection pipe 111 and a step 107 formed on the cylindrical body 105, and a pressing ring 11 is mounted on an upper surface of the O-ring 112.
3 is applied. A retaining ring 114 is mounted on the screw thread 106 formed in the cylindrical body 105, and the O-ring 112 is pressed via a retaining ring 113 by tightening the retaining ring 114, and the O-ring 1
Due to the deformation of 12, the airtightness between the connection pipe 111 and the cylinder 105 is maintained, and the connection pipe 111 is fixed to the cylinder 105.

On the inner peripheral surface of the lower end of the connection pipe 111, a step 1
An inner diameter of the step portion 115 is substantially equal to that of the connection tube 111, and one end side of a thin guide tube 116 is fitted and fixed in the step portion 115. This guide tube 11
The other end of the tube 6 is provided with a pipe 108 in order to prevent a relative flow between the gas flow sucked from the dewar 4 inside the cylinder 105 and the gas flow discharged into the dewar 4.
Extending 20cm or more below the entrance.

The transfer tube 5 is an inner tube 5
a and a liquid helium flowing in the transfer tube 5 in the guide tube 116 because the gas discharged into the dewar 4 and the liquid helium flowing in the transfer tube 5 are formed in the guide tube 116. There is almost no heat exchange between them. Therefore, there is no possibility that the helium gas flowing through the gap between the guide tube 116 and the transfer tube 5 is cooled.

On the peripheral wall of the connecting pipe 111 at an intermediate position in the axial direction,
One ends of the pipes 117 and 118 are connected so as to communicate with 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.
1, 122 are connected to a piping 123 for pressure measurement. The other end of the pipe 123 communicates with the pressure sensor in the control device 29a described above. In addition, the joint mechanisms 120 and 122 are connected to the joint mechanisms 119 and 121, respectively.
The connection ports of the corresponding pipes are automatically opened when the connection is made, and the connection ports of the corresponding pipes are automatically closed when the connection ports are detached from the joint mechanisms 119 and 121.

A thread 1 is provided on the outer peripheral surface of the upper end of the connection pipe 111.
24 are formed on the inner peripheral surface of the upper end portion.
5 are formed. O between the outer peripheral surface of the transfer tube 5 and the step 125 formed in the connection tube 111
A ring 126 is mounted, and a pressing ring 127 is applied to an upper surface of the O-ring 126. A retaining ring 128 is attached to the thread 124,
The O-ring 126 is pressed via the holding ring 127 by the tightening of the retaining ring 128, and the O-ring 126 is deformed by the pressing, thereby maintaining the airtightness between the transfer tube 5 and the connection pipe 111 and to the connection pipe 111. The transfer tube 5 is fixed.

With such a configuration, the control device 29a
, The valve 7 is controlled to open and the solenoid valve 101 is controlled to close. At the same time, the compressor 24 starts operating and the helium gas and the seal layer existing in the upper space in the dewar 4 are controlled. The helium gas present in 8 flows to the inlet of the compressor 24 and is pressurized by the compressor 24. That is, the helium gas floating in the upper space of the dewar 4 enters between the guide tube 116 and the cylindrical body 105 as shown by a solid arrow 129 in FIG.
It flows through the pipe 108 to the pipe 21. The helium gas pressurized by the compressor 24 flows into the annular space 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. For this reason, the pressure in the dewar 4 starts to rise. As described above, when the pressure in the dewar 4 rises, a part of the liquid helium 3 in the dewar 4 is transferred into the heat insulating container 2 through the transfer tube 5 by this pressure. Therefore, the same effects as in the above embodiment can be exhibited.

In this example, in order to prevent a relative flow between the flow of the gas sucked from the inside of the dewar 4 into the cylindrical body 105 and the flow of the pressurized gas discharged into the dewar 4, a pipe is not formed. The inlet 108 and the discharge port 130 do not exist in the same cylindrical body 105, and the distance H between the inlet of the pipe 108 and the discharge port 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,
With a separation of 20 cm or more, the rise can be started in a short time.

In this example, the control device 29a
Monitors the upper space pressure in the dewar 4 by opening the pipe 123, and when the pressure in the dewar 4 is 0.06 to
0.10Kg / cm ² The rotation speed or voltage of the compressor 24 is controlled so as to fall within the range described above, and after the time period set by the timer 103 has elapsed, the pressure in the dewar 4 becomes 0.14 kg / cm.
^Two Is controlled so that the rotation speed or voltage of the compressor 24 is maintained. Therefore, the flow rate of the 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, the liquid helium can be injected into the heat insulating container 2 with the consumption of the liquid helium suppressed. That is, initially, the temperature of the superconducting coil 1 has risen to near room temperature. As described above, since the latent heat of vaporization of liquid helium is as small as 5 calories per gram, the liquid helium that touches the superconducting coil 1 evaporates instantaneously. In particular, the thermal conductivity of the copper material constituting a part of the superconducting coil 1 does not increase unless it becomes 100K or less. Therefore, even if the liquid helium injection amount is increased from the initial stage, most of the liquid helium is evaporated. In order to pour the superconducting coil 1 in a state where the consumption of liquid helium is minimized, it is advisable to gradually cool the superconducting coil 1. As in this example, the injection can be performed efficiently by decreasing the flow rate at the beginning and increasing the flow rate after a certain time has elapsed.

Further, in this example, the connection with the pipes 21, 25, 123 is made by using the joint mechanisms 110, 120, 122 having a function of automatically releasing when connected and automatically closing when disconnected. Since it is performed, even if it is disassembled in order to switch to another dewar, the inside of the pipes 21, 25, 123 is filled with helium gas, so that air can be prevented from entering.
For this reason, it is possible to prevent a problem that easily occurs when air is mixed, that is, contamination of the helium gas, and that water in the mixed air freezes on the discharge port 130 or the like to cause poor pressurization or blockage of the pipe. 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 Koki 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 communicating with the gas recovery system, so that pumping can be completely automated by remote control. Thus, the pumping operation can be performed safely without approaching the superconducting coil 1.

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

FIG. 5 shows a modification in which the flow process of the helium gas is reversed in the structure shown in FIG. That is, the place where the suction port 104 is in FIG. 4 is a discharge port in FIG. 5, and similarly, the place where the discharge port 130 is the suction port is a suction port. With this change, the positions of the pipe 123 for pressure measurement, the joint mechanisms 121 and 122, and the pipe 118 connected to the pressure sensor in the control device 29a are changed.
Is connected to the peripheral wall at an intermediate position in the axial direction. However, these positions are not limited to the positions shown in the drawing, and may be provided anywhere 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, a detailed description of the overlapping part will be omitted. FIG. 6 shows a modification of the structural portion used in the embodiment of the present invention, here, a portion corresponding to FIG. In this figure, elements corresponding to the elements shown in FIG. 4 are denoted by the same reference numerals. Therefore, a detailed description of the overlapping part will be omitted.

This example is different from the example shown in FIG. 4 in that an element necessary for sucking up the helium gas floating in the upper space in the dewar 4 returns the compressed helium gas to the upper space in the dewar 4. That is, all the elements necessary for the measurement and the elements necessary for the pressure measurement are provided on the connection pipe 111a side.

That is, the transfer tube 5
It penetrates the eccentric position in the connection pipe 111a. Connection pipe 1
11a, the inner surface thereof and the transfer tube 5
The connecting pipe 111a
One ends of the pipes 117 and 118 are connected so as to communicate with each other. An oblique through-hole 131 is formed in the peripheral wall of the connection pipe 111a at a position where the distance between the inner surface thereof and the transfer tube 5 is long. This through hole 13
One end of a tube 132 is airtightly connected to 1. The other end of the tube 132 is connected to the joint mechanism 109. In the tube 132, one end is connected to the joint mechanism 109, and the other end extends downward in a space existing between the inner surface of the connection tube 111 a and the transfer tube 5. A tube 134 made of tetrafluoroethylene is provided in the upper space. In addition, the tube 134 has a discharge portion between the distal end portion 133 and the pipe 117 so that the flow of the pressurized (discharged) gas and the flow of the suction gas do not become a relative flow in the cylinder 105a or the connection pipe 111a. The distance to the exit is 2
The length is set to be 0 cm or more. In this example, since the transfer tube 5 is eccentrically arranged with respect to the connection tube 111a, the step portion 125 and the O-ring 12
6, an O-ring 135 and an intermediate ring 136 are interposed.

With such a configuration, it is not necessary to provide an element required for pressurization in the cylinder 105a, so that it is possible to immediately cope with various dewars and to improve the ease of handling.

FIG. 7 shows a modification of the structure shown in FIG. 6 in which the flow of helium gas is reversed. That is, the suction port 133 in FIG. 6 is a discharge port in FIG. 7, and similarly, the discharge port 104 is a suction port in FIG. With this change, the positions of the pipe 123 for pressure measurement, the joint mechanisms 121 and 122, and the pipe 118 connected to the pressure sensor in the control device 29a are changed.
It is connected to the upper wall. However, these positions are not limited to the positions shown in the drawing, and may be provided anywhere 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, a detailed description of the overlapping part will be omitted.

Next, the relationship between the pressure rise 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 an experimental result on a relationship between a pressure increase in the dewar and a pressurizing time. The experiment was performed on a 500 liter liquid helium dewar. 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 in the dewar 4 is 0.14 kg / cm ² capable of transporting the liquid helium 3. It takes about 1 minute to reach, whereas the structure shown in FIG. 6 requires about 10 minutes. This is considered to be due to the following reason.

In the structure shown in FIG. 6, cryogenic helium gas is sucked from the suction port 133 near the liquid level of the liquid helium 3 in the dewar 4, compressed to about room temperature, and then discharged from the discharge port 104. The helium gas is discharged into the upper space in the dewar 4 having a relatively low helium gas density. For this reason, it is considered that a significant change in the density (pressure rise) of the helium gas in the dewar 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 from the discharge port 130 provided immediately above the liquid helium liquid level into the cryogenic helium gas space. . It is considered that this causes a large change in density (pressure rise) because liquid helium having a small latent heat of vaporization evaporates rapidly from the liquid surface.

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

FIGS. 9 to 11 show a structure in which pressurized helium gas is released into liquid helium based on the structure shown in FIGS. 4 and 6. FIG. Here, each of the discharge ports 130 and 133 is a Dewar 4
It extends to near the bottom. Thus, even when liquid helium is consumed and the liquid level is lowered, the density change due to the evaporation of liquid helium can be effectively used. That is, in pumping liquid helium, FIGS.
The example shown in FIG. 1 is considered to be the most efficient structure.

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

In the above embodiment, liquid helium is used as the cryogenic liquid. However, it is needless to say that the present invention can be applied to pumping 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 a dewar 32,
For example, it is used when the liquid helium 33 is transferred into another heat insulating container, for example, the heat insulating container 34 containing the superconducting coil 34.

Since the latent heat of vaporization of liquid helium is as small as 5 calories per gram, if heat enters from outside during transportation, it evaporates easily. For this reason, this type of transfer tube usually has a double tube structure consisting of an inner tube through which liquid helium flows, and an outer tube arranged outside the inner tube, and vacuum insulation is provided between the inner tube and the outer tube. Layers are provided.
Evaporation of liquid helium is suppressed by the presence of the vacuum heat insulating layer.

However, evaporation of liquid helium caused by heat intrusion due to heat conduction from the outer tube cannot be ignored, and the transfer efficiency is generally low. In particular, in this type of transfer tube, a fitting-type connecting portion is provided in the middle, and a large amount of heat is transmitted to the 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 connection portion to be long, and it is unavoidable that the entire length is increased. Also, when transferring liquid helium from one insulated container to the other using a transfer tube,
It is necessary to insert one end of the transfer tube into liquid helium in one insulated container. For this reason, 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 inevitably increases.

The transfer tube 31 shown in FIG. 12 can contribute to solving the above-mentioned problem.
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 has an inner tube 40 made of stainless steel, an outer tube 41 arranged to cover the inner tube 40, and a vacuum formed between the inner tube 40 and the outer tube 41. And a heat insulating layer 42. Similarly, the tube 38 is also formed of an inner tube 43 made of stainless steel, an outer tube 44 arranged so as to cover the inner tube 43, and a vacuum insulation formed between the inner tube 43 and the outer tube 44. And a layer 45. The tube 37 is provided so as to hermetically penetrate the upper wall of the dewar 32 so that the tip opening 46 on one end side is located in the liquid helium 33 in the dewar 32. In addition, the tube 38 is inserted into the heat insulating container 3 such that the distal end opening 47 on one end side is located in the heat insulating container 35.
5 is provided in an airtight manner through the upper wall. Then, the other end of the tube 37 and the other end 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 seal ring 50 for sealing 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, a portion 1 near the male portion 48 and a portion located in the upper space in the dewar 32 are formed of ceramic tubes 51 and 52 made of alumina or the like having a low thermal conductivity, as shown in FIG. Similarly, in the inner tube 43 constituting the tube 38, a part of the portion constituting the female portion 49 is formed of the ceramic tube 53. Further, a part of a portion of the outer tube 44 constituting the tube 38 located in the heat insulating container 35 is formed of the ceramic tube 54. In FIG. 12, reference numeral 55 denotes a valve.

As described above, the transfer tube 31
If a ceramic tube is interposed in the middle of the process, especially in a portion where heat is likely to enter from the outside, the thermal conductivity of stainless steel can be reduced.
For 4W / m · k, that of ceramic is 21W / m · k
Since it is as small as k, heat intrusion from the outside can be suppressed, and transfer efficiency can be improved.

According to the experiment, the transfer tube 31 shown in FIG. 12 was used and the internal pressure of the dewar 32 was set to 0.14 kg / cm ^2. When the liquid helium 33 was transferred into the heat insulating container 35, 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,
The transfer was performed under the same conditions using the same transfer tube, except that only a ceramic tube of alumina or the like was not present. It took 20 minutes as shown by the broken line in FIG. The transfer efficiency at this time is 65%. in this way,
The transfer efficiency can be improved by interposing the ceramic tube. In addition, 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 pipes leading to the heat insulating container from being blocked by solidification of moisture, nitrogen, oxygen and the like contained in the air which is about to enter the heat insulating container.

In general, a pipe for protecting a power lead for supplying a current to the superconducting coil, a pipe for protecting measurement lines for pressure, temperature, strain, etc., and a helium gas are provided in the heat insulating container containing the superconducting coil. Many pipes, such as a pipe for collecting and a pipe for cooling the shield, are provided. The main material of the pipe is stainless steel, and aluminum is also used. Air may flow through these pipes depending on the situation. The incoming air (moisture, nitrogen, oxygen)
It is easy to solidify by touching the pipe cooled with cryogenic helium gas.

In this case, the metal pipe has poor wettability.
Therefore, the attached water solidifies in a hemispherical shape like a polka dot. These coagulations often collect and block the piping. If the helium gas recovery pipe is closed, the internal pressure of the heat insulating container increases, and the heat insulating container may be damaged. 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, a part of the liquid nitrogen in the shield tank solidifies. The pressure inside the shield tank is reduced. Due to this reduced pressure, air easily flows in through the pipe connected to the shield tank. When air tries to flow in,
Water and the like contained therein solidify on the inner surface of the pipe.
For this reason, the pipe is blocked, and thereafter, it becomes impossible to flow liquid nitrogen to the shield tank, which may increase the evaporation of liquid helium in the heat insulating container.

Therefore, in the example shown in FIG. 15, there is provided means for preventing blockage of the pipe which is likely to be caused by the inflow of air. 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. Is prevented.

As shown in FIG. 16, an ethylene tetrafluoride pipe 67 is mounted inside the pipe 66. That is, the pipe 66 has a double pipe structure, and the ethylene tetrafluoride pipe 67 is located inside. 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 opened to the atmosphere via valves 70, respectively. .

With such a configuration, the shield tank 65
When the liquid helium 62 is introduced into the heat insulating container 63 with the liquid nitrogen 71 accommodated therein and the valve 70 closed, the liquid nitrogen 71 in the shield tank 65 is transmitted or the like.
Is cooled and partly solidifies. This solidification reduces the pressure in the shield tank 65, which causes the valve 70
Air flows in from the connection part of the. The inflowing air removes a part of the water contained when passing through the adsorption tank 68, and subsequently flows to the tetrafluoroethylene pipe 67. At this time, the inner surface of the ethylene tetrafluoride tube 67 is cooled to an extremely low temperature. Therefore, the water contained in the flowing air adheres to the inner surface of the tetrafluoroethylene pipe 67 and solidifies.
In this case, since the ethylene tetrafluoride tube 67 has good wettability, the attached water spreads and adheres in a thin film shape, and solidifies in this state. Therefore, there is no possibility that the tetrafluoroethylene pipe 67, that is, the pipe 66 is blocked by the coagulation of water.

Although the above is an example in which the present invention is applied to the piping of the shield tank, it is needless to say that the present invention 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 tetrafluoroethylene may be applied. Also, as indicated by reference numeral 72 in the drawing, the adsorption tank 68 is connected by a cooling pipe.
May be cooled to about 77 K to improve the efficiency of adsorption of moisture, nitrogen, oxygen and the like in the adsorption tank 68.

FIG. 17 shows a plurality of heat-insulating containers 83a and 83a respectively containing a superconducting coil 81 and liquid helium 82.
A means for solving the problem that occurs when the gas recovery pipes 84a and 84b of the 83b are commonly connected to a gas bag or a helium refrigerator 85 is shown. When the gas collection pipes of multiple insulated containers containing a superconducting coil and liquid helium are connected to a gas bag or a helium refrigerator in common, if one superconducting coil is quenched, the other superconducting coils must be quenched by 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 evaporates, and the high-pressure helium gas is filled in the heat insulating container. This high-pressure helium gas passes through the gas recovery pipe and moves into another insulated container. For this reason, the temperature in the other heat-insulated container increases, and the liquid helium in the other heat-insulated container evaporates. As a result, the superconducting coils in the other heat-insulated container also quench 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 through the common pipe 86, and the respective gas recovery pipes 84a and 84b are connected.
Valves 87a and 87b including an electromagnetic valve, a spring return type electromagnetic valve, and the like are interposed in 84b. And
Safety valves 88a and 88b are attached to each of the heat insulating containers 83a and 83b, and pressure sensors 89a and 89b are attached. When the detected values of the pressure sensors 89a and 89b are going to exceed a certain value, the valves corresponding to the controllers 90a and 90b correspond. 87a and 87b are controlled to be closed.

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

FIG. 18 shows a modification. In this example, a 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 to the decision circuit 92. And
The judgment circuit 92 judges which pressure in the heat insulating container has risen, and the output is introduced to a controller 93.
The three-way valve 91 is controlled so that only the heat-insulated 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 increases due to the quench, the three-way valve 91 is switched as shown in FIG. Helium refrigerator 8
Disconnected from 5. This prevents chain reaction of the quench. The above example is an example in which there are two insulated containers, but when more than three are used, the method shown in FIG. 18 can be easily realized by dividing the system into two systems.

[0071]

As described above, according to the present invention, the internal pressure of an insulated container containing a cryogenic liquid without the consumption of the cryogenic liquid or its gas and without providing an electric heater inside. Can be increased, and the internal pressure can be increased by a small and lightweight compressor, which can contribute to improvement of workability.

[Brief description of the 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 view for explaining a modification 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 embodiment.

FIG. 5 is a diagram showing a modification of the specific configuration for realizing the above embodiment.

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

FIG. 7 is a diagram showing a modification of another specific configuration for realizing the above embodiment.

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

FIG. 9 is a view for explaining a modification of another embodiment of the cryogenic liquid pumping method according to the present invention.

FIG. 10 is a diagram showing another modification of the specific configuration for realizing the above embodiment.

FIG. 11 is a diagram showing another modified example of another specific configuration for realizing the above embodiment.

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

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

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

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

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

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

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

FIG. 19 is a view for explaining the operation of the means shown in FIG. 8;

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 method for pumping a cryogenic liquid.

[Explanation of symbols]

1 ... superconducting coil, 2 ... heat insulating 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)

(57) [Claims] 1. An internal pressure of an insulated container containing a cryogenic liquid is increased, and the cryogenic liquid is pumped out of the insulated container by using the increase in the internal pressure. The gas generated by evaporation of the cryogenic liquid is guided to a compression unit and 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 heat is applied to the gas pressurized by said compression means to raise the temperature, and then the gas is returned into the heat insulating container. . 3. The cryogenic liquid pumping method according to claim 1, wherein the gas pressurized by the compression means is returned to the cryogenic liquid layer in the heat insulating container. 4. The apparatus according to claim 1, wherein the internal pressure of the heat insulating container is increased stepwise toward a target pressure.
The method for pumping out a cryogenic liquid according to the above. 5. The apparatus according to claim 1, wherein said heat-insulating container and said compression means are detachable, and when said heat-insulation container and said compression means are attached and detached, said compression means as a whole is produced by evaporating said cryogenic liquid. The method for pumping out a cryogenic liquid according to claim 1, wherein the liquid is filled. 6. A cryogenic liquid pumping device for pumping the cryogenic liquid from an insulated container containing the cryogenic liquid,
Compression means for pressurizing a gas generated by the evaporation of the cryogenic liquid in the heat insulating container, a pumping port provided for guiding the gas to the compression means, and the electrode pressurized by the compression means A cryogenic liquid pumping device having a discharge port provided for returning the cryogenic liquid gas to the heat insulating container. 7. A position where the relative flow does not occur between the gas guided from the inside of the heat insulating container to the suction port and the pressurized gas returned into the heat insulating container from the discharge port. The cryogenic liquid pumping device according to claim 6, wherein the suction port and the discharge port are provided.