JP2854424B2 - Cryogenic cooling device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cryogenic cooling device, for example, a cooling system for cooling a superconducting coil.

[0002]

2. Description of the Related Art As a conventional cryogenic cooling device, a superconducting coil for a magnetically levitated railway and a cryogenic container accommodating the coil will be described as an example. FIG. 6 is a partially cutaway perspective view showing a superconducting magnet for a magnetically levitated railway disclosed in a document (IEEE, Linear Drive Workshop, April 27, 1988, page 27). In the figure, 3 is an inner tank containing a superconducting coil and liquid helium as a refrigerant, 15 is a liquid helium tank for supplying liquid helium to the inner tank 3, and 13 is a heat shield covering the inner tank 3 and the liquid helium tank 15. Plate, 16 is a permanent current switch for operating the superconducting coil in the permanent current mode, 17 is a load supporting member for supporting the inner tank 3 insulated, 18 is the inner tank 3, the liquid helium tank 1
5, an outer tank containing components such as the heat shield plate 13, the permanent current switch 16, and the load support member 17, that is, a cryogenic vacuum vessel. Reference numeral 19 denotes a cooling pipe for supplying liquid nitrogen from a liquid nitrogen tank (not shown) by a liquid nitrogen pump as indicated by an arrow A.

[0003] The operation of the superconducting magnet thus configured will be described mainly with respect to a cooling device. A superconducting coil is housed in the inner tank 3, and a helium tank 15 for keeping the superconducting coil in a superconducting state.
The liquid helium supplied is full. The superconducting coil is supplied with current from an exciting power supply (not shown), and is operated in a permanent current mode by using a permanent current switch 16. To operate the superconducting coil and the permanent current switch 16, it is necessary to maintain the superconducting state. For this purpose, it is necessary to minimize the intrusion of heat from the outside into the inner tank 3, and many measures have been taken.

The inner tank 3 is usually about 4.2 K, the helium tank 15 is about 80 K, and the outer tank 18 is about 300 K. As a countermeasure against heat intrusion from the outside, for example, in addition to employing the heat-insulating load supporting member 17, the heat shield plate 1 may be used.
3 installations. The heat-insulating load supporting member 17 is a measure for reducing heat intrusion due to heat conduction from the outer tank 18 to the inner tank 3, and the heat shield plate 13 is also a measure for reducing heat intrusion due to heat radiation. The heat shield plate 13 is normally cooled to the temperature of liquid nitrogen, that is, about 77.3 degrees K under one atmosphere. In this conventional example, the liquid nitrogen is passed through the cooling pipe 19 to maintain the temperature near the liquid nitrogen temperature. And That is, the cooling pipe 19 is led from a liquid nitrogen tank (not shown). In this device, liquid nitrogen is forcibly circulated in the cooling pipe 19 by a liquid nitrogen pump attached to the liquid nitrogen tank, and the heat shield plate 13 is The temperature is maintained near the temperature of liquid nitrogen. Of course, heat radiation from the outer tank 18 also exists in the heat shield plate 13, but the amount of heat penetration is covered by liquid nitrogen which is cheaper than liquid helium. It can be called thought.

In the conventional apparatus, the heat intrusion into the inner tank 3 containing the superconducting coil and the liquid helium tank 15 is reduced as described above, but the heat intrusion never becomes zero. Therefore, liquid helium evaporates gradually, and a measure is usually taken to re-inject new liquid helium or to recondense the liquid helium with a helium refrigerator in order to compensate for the evaporation.

[0006]

The conventional cryogenic cooling apparatus is configured as described above. When liquid helium is re-injected, moisture or impurity gas is mixed into the liquid helium tank 15 from outside air. In addition, there is a problem that a device must be devised so as not to do so, and in addition, the injection operation must be performed each time. In the case of recondensing, the condenser must be installed in the gas phase, and there is a restriction that the liquid helium tank 15 must be always placed above the inner tank 3. There was a problem that it was a body force convection condensation, and was not a heat transfer form that could obtain a large heat transfer coefficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and does not require a liquid injection operation, and can efficiently transfer heat in a cold generating section and a heat load section of a refrigerator. The purpose is to obtain a cooling device.

[0008]

A cryogenic cooling apparatus according to the present invention connects a heat receiving storage tank and a cooling receiving storage tank for storing a single-phase fluid, and connects the storage tanks so that the single-phase fluid in the storage tank can flow inside. Connecting pipe, a driving mechanism for periodically vibrating the single-phase fluid in the connecting pipe, a superconducting coil housed in the heat-receiving storage tank, a cooling unit for cooling the single-phase fluid in the cold-receiving storage tank, and a driving mechanism. The heat is transferred to a cryogenic temperature by causing a single-phase fluid to periodically reciprocate within the range of the connecting pipe without entering the storage tank from the other storage tank.

Further, a heat receiving storage tank and a cold receiving storage tank for storing a single-phase fluid, a connecting pipe for connecting the storage tanks so that the single-phase fluid in the storage tank can flow through the inside, and a single-phase fluid in the connecting pipe for periodicity. A cooling mechanism for cooling the single-phase fluid in the cold storage tank.

The drive mechanism is a drive mechanism for the refrigerator and the cooling section is a cold generation section of the refrigerator.

Further, two connecting pipes for connecting the storage tanks are provided, and the drive mechanism is configured to periodically and alternately vibrate the single-phase fluid in the two connecting pipes.

[0012]

In the cryogenic cooling apparatus according to the present invention, a heat transfer pipe called a connecting pipe or a dream pipe is used as a cooling means for the cryogenic vessel. With this dream pipe, the heat received at the heat load section and the cold generated at the cold generating section are exchanged with each other, so that the exhaust heat can be cooled. Further, heat transfer between the heat load unit and the cold generating unit and the refrigerant is governed by convective heat transfer due to forced flow of the refrigerant, so that the superconducting coil or the heat shield unit can be efficiently cooled.
Therefore, there is no need to perform a refrigerant injection operation other than the initial injection.

[0013]

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a cryogenic cooling device according to one embodiment of the present invention. In the figure, 1 is a superconducting coil, 2 is liquid helium which is a single-phase fluid, 3 is an inner tank containing the superconducting coil 1 and liquid helium 2, that is, a heat receiving storage tank, 4 is a connecting pipe, for example, a dream pipe section, and 5 is, for example, a piston. 5a is a shaft connected to the piston 5, 5b is a low-temperature seal, 6 is a cooling unit,
For example, a cold generating section of a helium refrigerator, 7 is a cold storage tank, 8
Is a fluid escape pipe. The length of the dream pipe section 4 in the longitudinal direction is, for example, about 1 m, and each of the storage tanks 3 and 7 and the dream pipe section 4 are made of stainless steel or epoxy resin.

Next, the cooling operation of the superconducting coil in the superconducting magnet thus configured will be described.
Regardless of how the superconducting coil 1 and the inner tank 3 are designed to be thermally insulated, there is some heat loss. For example, in the superconducting coil 1, frictional heat is generated when the superconducting wire moves due to loss or electromagnetic force at a connection portion, and heat intrusion occurs in the inner tank 3 due to conduction through a heat insulating support member (not shown in FIG. 1). Therefore,
If the liquid helium 2 in the inner tank 3 is in a supercooled state, the temperature of the liquid helium 2 rises due to these heat generation and heat intrusion. On the other hand, the temperature of the cold storage tank 7 is lower than that of the heat receiving storage tank 3 by being cooled by the cold generating unit 6. It is the dream pipe section 4 that equalizes the temperature between these two storage tanks.

The basic principle of the dream pipe section 4 is described in, for example, Journal of the Japan Society of Mechanical Engineers, Vol. 90, No. 824,
It is described on page 991. Briefly, as a basic configuration, at least two cryogenic storage tanks are provided, these storage tanks are connected by a connecting pipe through which a refrigerant can flow, and a heat load unit such as a superconducting coil or a thermal anchor is provided in one of the storage tanks. The other storage tank is provided with a cold generation part.

The dream pipe section 4 may be an elongated pipe having a diameter of about several mm. And in dream pipe section 4 a liquid helium, for example several tenths of Hz~ tens Hz
What is necessary is to oscillate periodically in the left-right direction of the figure at this frequency.
The driving source is a piston mechanism 5, and a desired vibration can be given to the liquid helium 2 by reciprocating the piston mechanism. The escape portion of the fluid when the liquid helium 2 is vibrated periodically is the escape pipe 8. The liquid helium 2 only needs to flow in the dream pipe section 4, and there is no need to send the liquid helium in the cold storage tank 7 to the heat receiving storage tank 3. That is, it is sufficient that the amplitude oscillates at or below the length of the dream pipe section 4, for example, about 1/3 of the length near the center of the dream pipe section 4. By giving such a flow amplitude to the liquid helium 2, the heat exchange between the heat receiving storage tank 3 and the cold receiving storage tank 7 can be performed extremely well, and the uniform cooling of both storage tanks can be achieved efficiently. The degree of heat transport of the dream pipe portion 4 reaches several hundred times that of the heat pipe depending on the conditions. In addition, heat exchange between the superconducting coil 1 and the liquid helium 2 in the heat receiving storage tank 3 and heat exchange between the liquid helium 2 and the cold generating part 7 in the cold receiving storage tank 7 are performed in the respective storage tanks 3 and 7. Since the liquid helium 2 is flowing, it can be performed more effectively than when the liquid helium 2 is stationary.

As described above, the heat received by the heat load section by the dream pipe section 4 and the cold generated by the cold generation section can be exchanged for exhaust heat cooling. Heat transfer between the heat load section and the cold generating section and the refrigerant is governed by convective heat transfer due to forced flow of the refrigerant, so that the superconducting coil 1 can be efficiently cooled. Therefore, there is no need to perform a refrigerant injection operation other than the initial injection.

Although the internal fluid in the above embodiment is liquid helium, it may be supercritical helium, or liquid nitrogen for cooling a high-temperature superconductor or for heat shielding. Of course, there is no problem even if other refrigerants are used. In other words, it is sufficient that the refrigerant is a single-phase fluid, and the temperature level of the cold generating section may be adjusted according to the refrigerant used. In the above embodiment, the fluid drive mechanism is of the piston type, but may be a structure using bellows or the like.

Embodiment 2 FIG. FIG. 2 is a configuration diagram illustrating a cryogenic cooling device according to a second embodiment of the present invention, in which a piston for driving a fluid and a piston (or displacer) of a refrigerator for generating cold are connected. In the figure, reference numeral 9 denotes a cylinder of the refrigerator, 10 denotes a piston or displacer of the refrigerator, 10a denotes a shaft, 11 denotes a seal, and 12 denotes a connection drive unit for the piston 6 and the piston 10. As described above, the drive structure 5 for flowing the working fluid in the dream pipe 4 and the drive mechanism of the refrigerator for the cooling unit 6 are linked to form an integrated structure, thereby reducing the size and efficiency of the drive mechanism. There is an effect that can be achieved.

Embodiment 3 FIG. Third Embodiment FIG. 3 is a configuration diagram when a third embodiment of the present invention is applied to a heat shield. In the figure, 13 is a storage tank for heat shield, and 14 is liquid nitrogen which is a single-phase fluid. Of course, the cold generation part 6 is at the liquid nitrogen temperature level (about 65 to 75 degrees K).
In this configuration, the surface of the heat receiving storage tank is used as a heat shield surface. Even with such a configuration, the same effect as in the above embodiment can be obtained. Further, the heat receiving storage tank may be brought into thermal contact with the heat shield surface. Furthermore, in this configuration, the dream pipe part 4 and the heat shield part 13 are separate, but the dream pipe part 4 may be the heat shield part as it is.

Further, if the dream pipe section 4 is configured to receive the heat load generated in the heat receiving storage tank, the efficiency can be further improved.

Embodiment 4 FIG. FIG. 4 shows a fourth embodiment of the present invention, in which a plurality of heat receiving storage tanks 3a, 3a, 3
This is an example where b and 3c are connected. Normally, superconducting coils for a magnetically levitated railway are arranged at a plurality of locations in one device, and with such a configuration, one refrigerator can be used effectively.

Embodiment 5 FIG. The cryogenic cooling device shown in FIG.
One drive mechanism 5 allows the fluids in the two cold storage tanks 7a and 7b to flow. In a cryogenic cooling device using a dream pipe, it is necessary to secure a relief portion for the fluid in order to vibrate the fluid periodically, but with such a configuration, the escape pipe 8 is not required, and the efficiency is reduced. A compact configuration can be realized.

[0024]

As described above, according to the present invention, a heat receiving storage tank and a cooling receiving storage tank for storing a single-phase fluid, a connecting pipe for connecting the storage tanks so that the single-phase fluid in the storage tank can flow through the inside, A drive mechanism for periodically vibrating the single-phase fluid in the connection pipe, a superconducting coil housed in the heat-receiving storage tank, and a cooling unit for cooling the single-phase fluid in the cold-receiving storage tank are provided. By reciprocally flowing heat within the range of the connecting pipe from one storage tank to the other without periodically entering the other storage tank, heat is transferred to extremely low temperature, eliminating the need to resupply refrigerant. In addition, a cryogenic cooling device capable of realizing cooling with a higher heat exchange rate than a normal recondensing type can be obtained.

Further, a heat-receiving storage tank and a cooling-receiving storage tank for storing a single-phase fluid, a connecting pipe for connecting the storage tanks so that the single-phase fluid in the storage tank can flow through the inside, and a single-phase fluid in the connecting pipe for periodicity. The provision of a drive mechanism that vibrates the heat, a superconducting coil surrounded by the heat-receiving storage tank, and a cooling unit that cools the single-phase fluid in the cooling-receiving storage tank has the effect of being applicable as a heat shield plate.

The drive mechanism is a drive mechanism of the refrigerator and the cooling section is a cold generation section of the refrigerator.
In addition to the above effects, there is an effect that the device can be made compact.

Further, two connecting pipes for connecting the storage tanks are provided, and the drive mechanism vibrates the single-phase fluid in the two connecting pipes alternately and periodically. There is an effect that can be done.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a cryogenic cooling device according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a cryogenic cooling device according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a cryogenic cooling device according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram showing a cryogenic cooling device according to Embodiment 4 of the present invention.

FIG. 5 is a configuration diagram showing a cryogenic cooling device according to Embodiment 5 of the present invention.

FIG. 6 is a configuration diagram showing a conventional cryogenic cooling device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Superconducting coil 2 Single-phase fluid 3 Heat receiving storage tank 4 Connecting pipe 6 Cooling unit 7 Cold receiving storage tank

Claims (4)

(57) [Claims] 1. A heat-receiving storage tank and a cooling-receiving storage tank for storing a single-phase fluid, a connecting pipe connecting the storage tanks so that the single-phase fluid in the storage tank can flow inside, and a single-phase fluid in the connecting pipe. A drive mechanism that periodically vibrates, a superconducting coil housed in the heat receiving storage tank, a cooling unit that cools a single-phase fluid in the cold receiving storage tank, and the drive mechanism causes the single-phase fluid to flow from one of the storage tanks. A cryogenic cooling apparatus characterized in that heat is transferred to a cryogenic temperature by periodically reciprocating flow within the range of the connecting pipe without entering the other storage tank. 2. A heat receiving storage tank and a cooling receiving storage tank for storing a single-phase fluid, a connection pipe connecting the storage tanks so that the single-phase fluid in the storage tank can flow inside, and a single-phase fluid in the connection pipe. A drive mechanism for periodically vibrating, a superconducting coil surrounded by the heat receiving storage tank, a cooling unit for cooling a single-phase fluid in the cold receiving storage tank, wherein the drive mechanism causes the single-phase fluid to flow from one storage tank to the other. A cryogenic cooling device wherein heat is transferred to a cryogenic temperature by periodically reciprocating flow within the range of the connecting pipe without entering the storage tank. 3. The cryogenic cooling apparatus according to claim 1, wherein the drive mechanism is a drive mechanism of the refrigerator, and the cooling unit is a cold generating unit of the refrigerator. 4. The apparatus according to claim 1, further comprising: two connecting pipes for connecting the storage tanks, wherein the driving mechanism vibrates the single-phase fluid in the two connecting pipes alternately and periodically. Item 4. The cryogenic cooling device according to any one of Items 1 to 3.