JPH0536526A - Method for cooling forced cooling conductor - Google Patents

Abstract

PURPOSE:To improve a passage of coolant and also improve coolant property to increase coolant efficiency so as to improve stability of superconductivity by reducing a pressure at an outlet of a forced cooling type superconductor and sucking extremely low temperature coolant from an inlet to perform cooling. CONSTITUTION:A method for cooling a forced cooling conductor comprises a superconductor 3 of forced cooling type, extremely low temperature coolants 11, 22 for cooling the superconductor 3 and pressure reducing devices 4A, 4A' for sucking the coolants 11, 22 into the superconductor 3. In such a superconducting apparatus, a pressure is reduced at an outlet of the superconductor 3 to suck the extremely low temperature coolants 11,22 from an inlet to perform cooling. For example, three superconducting wires are twisted together, and three pieces of the twisted wires are twisted together. Further four fluxes each containing nine wires are bundled to be put into a stainless stool pipe and solid-drawn in a rectangle to form a superconductor 3 having a cooling passage 3L, which is wound around a bobbin to fabricate a superconducting coil 30. The coil 30 is cooled by sequentially switching over liquid nitrogen 11 and liquid helium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forced (hollow) cooling type superconducting conductor cooling system using a forced (hollow) cooling type superconducting conductor, such as a fusion reactor, an accelerator, a transmission line, or a superconducting device. Regarding the method.

[0002]

2. Description of the Related Art A method for cooling a superconducting device using a superconducting conductor is a direct immersion cooling method in which a superconducting conductor is directly immersed in a refrigerant, or a forced cooling method in which a cryogenic refrigerant is forced to flow into a hollow portion of the superconducting conductor for cooling. There is. In the case of the immersion cooling method, the stability of the coil is improved because the entire outer surface of the coil can be cooled with a large amount of refrigerant. When a coil becomes large, such as in a fusion reactor, accelerator, or transmission line, a large amount of cryogenic refrigerant that directly cools the large cryostat and the coil into which this coil is inserted is needed at one time. The liquefier and the recovery system become large due to the amount of evaporation, etc., and maintenance becomes difficult. On the other hand, in the case of the forced (hollow) cooling type superconducting conductor, the superconducting conductor itself has a refrigerant passage, and has a great feature that cooling can be performed by continuously flowing a very small amount of refrigerant. However, when the forced (hollow) cooling type superconducting conductor is used, there are disadvantages that the cross-sectional area becomes large and the current density decreases and that the refrigerant does not flow easily. In order to alleviate this problem, there is also a method of embedding a superconducting wire in a stabilizing material so that the hollow portion is completely hollow and enlarged to improve the flow of the refrigerant. However, this method is a method of indirectly cooling the superconducting wire, which causes a drawback that cooling efficiency is lowered and responsiveness is lowered. Further, the manufacturing structure of the superconducting conductor is complicated, the manufacturing cost is high, and further, the current density of the coil, which is the most important factor in handling the superconducting conductor, is lowered. In order to improve this drawback, there is a tendency to increase the space factor of the superconductor and to manufacture a superconductor having a high current density structure in which the refrigerant can be immersed and cooled in the superconductor. But,
During the initial cooling, the pressure loss becomes high, the flow rate of the refrigerant becomes difficult to flow, and another drawback that a long time is required for precooling occurs. Further, when quenching occurs during use, the vaporized gas explosively increases. For example, it is considered that the liquid helium of 4.2K expands seven hundred times, and most of the refrigerant is removed by the pressure increase in the refrigerant passage, and the heat energy of a large current may cause the refrigerant to melt. Many methods have been proposed to remedy this drawback. Japanese Patent Application Sho 59-24
According to the specification of 4484, a method is proposed in which a hollow cooling pipe line is provided in parallel with a forced (hollow) cooling type superconducting conductor to reduce pressure loss on the inlet side. However, if the coil is manufactured while it is attached in parallel with the superconducting conductor, there is a big drawback that the current density of the coil itself is lowered. Further, a method of winding a cooling pipe only on the exterior side of the coil has been proposed, but there is a drawback in that cooling heat is less likely to be transmitted to the inside of the coil body. Further, Japanese Patent Publication No. 2-50565 discloses a method in which a cryogenic refrigerant, for example, liquid helium is depressurized and converted into supercritical pressure helium for use. However, on the inlet side of the forced (hollow) cooling type superconducting conductor, it is necessary to apply pressure to actually send out the refrigerant, and it is extremely difficult to secure the properties of this supercritical pressure helium and use it. . The reason for this is that it requires the application of pressure to deliver. That is, it is unlikely that the refrigerant having entered the refrigerant passage becomes evaporative gas due to heat exchange, the pressure of the refrigerant itself increases, and the property of supercritical helium is maintained as it is. Further, the device for continuously producing this refrigerant has a large size, and pressure adjustment for temperature control is complicated, which causes many problems such that maintenance of the device itself becomes difficult.

[0003]

SUMMARY OF THE INVENTION An object of the present invention relates to a method for cooling a forced (hollow) cooling type superconducting conductor, in which the outlet side of the hollow interior is decompressed to improve the passage of the refrigerant. It is an object of the present invention to provide a method of improving properties, improving cooling efficiency, and improving stability of superconductivity.

An object of the present invention is to enable efficient cooling by changing the properties of the refrigerant so that the refrigerant can easily pass therethrough, and further to shorten the cooling time and improve the stability of the coil. Another object of the present invention is to make the apparatus small, simple, easy to handle and economical.

[0005]

In order to achieve the above object, the outlet inside the hollow of a forced (hollow) cooling type superconducting conductor is decompressed by using a decompressor so that the refrigerant can be easily drawn in from the inlet inside the hollow. is there. Further, in order to make it easier for the refrigerant to pass through the hollow interior, the pressure can be continuously reduced. Further, since the refrigerant (liquid helium 4.2k evaporates more than 700 times), the decompressor is arranged in a parallel circuit so that the hollow interior can be decompressed at all times with a margin.

[0006]

In the cooling of the forced (hollow) cooling type superconducting conductor, the refrigerant is depressurized on the outlet side and drawn into the inlet to continuously cool the superconducting conductor in a state where the cooling characteristic is improved by the depressurizing effect. The refrigerant continuously evaporates due to the temperature difference of the refrigerant that cools the coil. This structure continuously collects a large amount of evaporative gas, and enables the pressure inside the hollow to be constantly reduced so that the refrigerant can be forcibly continuously flown and cooled. As a result, the cooling time of the forced (hollow) cooling type superconducting conductor is
Even if the amount of vaporized gas increases rapidly due to extremely shortened and efficient operation and quenching, etc., the refrigerant may be removed and stopped due to a rise in gas pressure during the process, etc., by continuously and continuously forcibly reducing the pressure. It won't happen. That is, the superconducting wire is cooled continuously and safely and efficiently.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG.

[0008] First, this time the fabricated superconducting coils, superconducting conductor 3 hollow cross-sectional area of the line of superconducting wire 31 cross-sectional area 0.785 mm ² three twisted at 50 mm ^2, further it three twisted, present the nine Four more bundles were bundled into a stainless pipe and drawn into a rectangle to complete a molded conductor. This forming process has a structure in which the clearance through which the refrigerant passes and the superconducting wire 31 itself is not damaged by coil forming, and measures are taken to prevent the superconducting wire 31 from moving due to the exciting current and the magnetic field to deteriorate the characteristics. Superconducting conductor 3 bobbin inner diameter 15
A forced hollow cooling type superconducting coil 30 having a 0 mm outer diameter of 175 mm and a length of 40 turns and a length of about 23.5 m was manufactured. This coil 30 was placed in the vacuum container 3A and cooled. The coil 30 was subjected to a cooling test and an excitation test using liquid nitrogen 11, liquid helium 22, and supercritical helium 5A. First, the liquid nitrogen and the gaseous mixture are introduced at an inlet pressure of 5 kg / cm.
^It was inserted with ² and the outlet side was opened. At this time, gas was blown out from the outlet for a few seconds only at the beginning. But then
Gradually, the flow of evaporative gas stopped. Next, the entire coil was sufficiently warmed to room temperature, and then 4.2K liquid helium liquid was directly fed under pressure of 0.3 kg / cm ² .
As a result, initially gaseous gas was released from the outlet. After that, the same result as when liquid nitrogen was inserted was obtained. However, when the applied pressure was lowered to 0.1 kg / cm ² or less, the evaporative gas from the outlet was discharged more smoothly than when the applied pressure was high. The coil 30 was heated to room temperature and cooled using the supercritical helium liquefier 5A. Circulating gas pressure 5 atm, circulating gas flow rate 3.5 g / s, refrigerant temperature 3
It was carried out using an apparatus having a cooling capacity of 100 watts at -5K. Gaseous gas blew out of the outlet for a few seconds at the beginning, but after that almost disappeared. Instead, the pressure at the entrance gradually increased and the refrigerator stopped. As described above, when the difference between the refrigerant temperature and the temperature of the superconducting conductor 3 to be cooled is large, the refrigerant is vaporized and its volume is increased (about 700 times the volume when liquid helium of 4.2 K and 1 atm is vaporized to room temperature). Since it increases more than seven hundred times, the pressure in the refrigerant passage explosively rises when the cooling is repeated continuously, creating a state in which the refrigerant passage is blocked. That is, the method of cooling the superconducting wire 3 by pouring the refrigerant under pressure from the inlet side is
The higher the pressurizing force, the faster the heat exchange proceeds, the gas volume increases rapidly, the internal pressure rises, and it becomes difficult for the refrigerant to pass. It was also confirmed that the lower the temperature of the refrigerant, the larger the volume when gasified, and the sudden rise in the internal pressure, making it difficult to cool the superconducting wire 3.

Then, as a result of studying the cooling method, it was possible to devise this device.

This device uses a coolant (eg, liquid oxygen, liquid nitrogen, liquid hydrogen,
It has a structure that allows switching between liquid helium, supercritical helium, etc.). First, the container refrigerant 11 in the storage tank 1A
Is connected by a transfer pipe and enters the refrigerant passage of the superconducting coil 30 by opening and closing an automatic opening / closing valve (hereinafter referred to as a valve) valve B11. Pressure adjustment automatic opening / closing valve (hereinafter referred to as a valve) valves B1 to Bn are used for pressure adjustment and refrigerant. A coolant passage is provided which allows the flow rate to be adjusted and cools the coil. In this state, pressurized gas can be introduced from the inlet 1 and the valve B10 can be opened to pump the liquid nitrogen. The gas generated by the heat exchange opens the pressure regulator C, or opens or closes an automatic opening / closing valve (hereinafter referred to as a valve) valve B31 and works in conjunction with a pressure reducing regulator (hereinafter referred to as a pressure reducing device) 4A in a refrigerant passage. The inside is decompressed and the coil is cooled by the passage of the refrigerant, and the gas generated and vaporized thereby can be released to the outside more quickly by the decompressor 4A. Further, it may be recovered for the problems of the structure of the superconducting device, the cooling structure of the superconductor, the treatment of evaporative gas or the like, or for economical operation, and may be liquefied by the liquefier 5A 'and reused. A refrigerant that is liquefied by opening and closing an automatic opening / closing valve (hereinafter referred to as a valve) valve B41 can be selected. The refrigerant to be recovered is recovered by the decompressor 4A 'and guided to the liquefier for reuse. Also, the refrigerant that has entered the liquefying process is 4.2K by the liquefier 5A.
Of liquid helium or supercritical helium. In the case of 4.2K liquid helium, liquid helium 22 is stored in the storage tank 2A container by opening and closing an automatic opening / closing valve (hereinafter referred to as a valve) valve B52.
By opening and closing an automatic opening / closing valve (hereinafter referred to as a valve) valve B21 and supplying a pressurized gas from the inlet 2, the superconducting coil 30 sufficiently cooled by liquid nitrogen or the like is sent to the valves B1 to B1.
The coil is further cooled by opening and closing n, and the evaporated refrigerant is released to the atmosphere by the pressure reducer 4A or 4A 'in consideration of the purity of the refrigerant and the like by liquid nitrogen, by opening and closing the valve B31, or Select whether to collect and reuse. Further, the pressure reducers 4A and 4A 'are attached in parallel so that the cooling heat of the refrigerant does not cause any trouble. The liquid made into supercritical helium by the liquefaction machine 5A is the same as the superconducting coil 30 sufficiently cooled with liquid helium of 4.2K by opening and closing an automatic opening / closing valve (hereinafter referred to as valve) valve B51. Cooled in the circuit. In this way, the coil is cooled by the forced cooling conductor 3
Or the arrangement structure of the superconducting wire 3, the space factor, the surface area ratio, and the temperature or the nature and the property of the refrigerant, a large amount of vaporized gas is generated due to the temperature difference from the coil. This gas was quickly recovered by the decompressor 4A ', and the decompressed state could be continuously maintained up to 0.8 atm. In this depressurized state, the inlet side refrigerant could be easily drawn in continuously. As a result, it could be cooled in only 45 minutes. As a result of exciting the coil 30, it was possible to energize the coil 30 with one excitation up to 100% of the short length characteristic value. It was also confirmed that when the pressure of the refrigerant is reduced, the properties of the refrigerant change and the cooling characteristics are greatly improved. This content is based on Cryogenic Engineering Handbook No. 3
It is described in detail in Chapter, Properties of Cold Wood.

[0011]

According to the present invention, the properties of the refrigerant can be changed by reducing the pressure of the refrigerant before use. Due to this effect, the refrigerant temperature further decreases and the cooling efficiency improves. Especially, the cooling of the forced (hollow) cooling type superconducting conductor is due to the small volume of the hollow part and the immersion cooling in which the refrigerant directly adheres to the superconducting wire. The effect is remarkable, the decompressor can be downsized, the structure and operation are simple, and the temperature can be surely controlled. Further, it is effective in improving the characteristics of the superconducting coil and improving the economical operation.

[Brief description of drawings]

FIG. 1 is a system diagram of a cooling device for a forced cooling conductor according to an embodiment of the present invention.

FIG. 2 is a sectional view of the forced cooling conductor of the present invention.

FIG. 3 is a sectional view showing the shape and cooling structure of a conventional superconducting conductor.

[Explanation of symbols]

1, 2 ... inlet, 3 ... forced (hollow) cooling type superconducting conductor,
11 ... Liquid nitrogen, 22 ... Liquid helium, 30 ... Superconducting coil, 31 ... Superconducting wire, 1A, 2A ... Storage tank, 3A ... Vacuum heat insulation container, 4A, 4A '... Decompression regulator, 5A, 5A' ...
Liquefaction device, B1 to Bn, B31, B32, B33, B5
1, B52 ... Automatic on-off valve, C ... Pressure regulator, 3L ... Refrigerant passage.

Claims (11)

[Claims] 1. A superconducting device comprising a forced cooling type superconducting conductor, a cryogenic refrigerant for cooling the superconducting conductor, and a pressure reducing device for sucking the refrigerant into the superconducting conductor. A method for cooling a forced cooling conductor, comprising decompressing on the outlet side of a superconducting conductor and sucking a cryogenic refrigerant from the inlet side for cooling. 2. The method for cooling a forced cooling conductor according to claim 1, wherein the superconducting conductor is cooled by depressurizing the outlet side and pressurizing the inlet side. 3. The method for cooling a forced cooling conductor according to claim 1, wherein an on-off valve and a temperature sensor are provided on the outlet side for each one or each of the superconducting conductors to control the flow rate of the refrigerant. 4. The force sensor according to claim 3, wherein a temperature sensor for detecting a refrigerant temperature on an inlet side of the superconducting conductor and an opening / closing valve and the temperature sensor on an outlet side for each one layer or each partition are provided to regulate the flow rate of the refrigerant. Cooling method for cooling conductors. 5. A superconducting device comprising a forced cooling type superconducting conductor, a cryogenic refrigerant for cooling the superconducting conductor, and a pressure reducing device for sucking the refrigerant into the superconducting conductor. A method for cooling a forced cooling conductor, characterized in that the type of refrigerant and the flow rate of the refrigerant are sequentially switched to perform cooling. 6. A superconducting device comprising a forced cooling type superconducting conductor, a cryogenic refrigerant for cooling the superconducting conductor, and a pressure reducing device for sucking the refrigerant into the superconducting conductor. A method for cooling a forced cooling conductor, characterized in that a type of refrigerant and a flow rate of the refrigerant are flown in a parallel circuit to cool. 7. A superconducting multi-row conductor of forced cooling type, a plurality of cryogenic refrigerants for cooling the superconducting conductor, and a pressure reducing device for sucking the refrigerant into the inside and the outside of the superconducting conductor. In this superconducting device, a pressure reducer is connected to the refrigerant outlet side by multiple parallel circuits for each refrigerant passage, and either the pressure or temperature at the inlet side is detected and the flow rate is adjusted for each refrigerant type and each refrigerant passage. A method for cooling a forced cooling conductor, characterized in that the cooling is carried out in a flowing manner. 8. A superconducting device comprising a plurality of rows of forced cooling type superconducting conductors, a cryogenic refrigerant for cooling the superconducting conductors, and a pressure reducing device for sucking the refrigerant into a refrigerant passage of the superconducting conductors. In the device, a plurality of pressure reducers are provided in parallel circuits for each of the refrigerant passages, and the inlet temperature, the pressure, or the temperature in the middle of the superconducting conductor is detected to detect the flow rate of the refrigerant and the manufacturing efficiency of the liquefying machine. A method for cooling a forced cooling conductor, characterized by adjusting. 9. A superconducting device comprising a plurality of forced cooling type superconducting conductors, a cryogenic refrigerant for cooling the superconducting conductor, and a pressure reducing device for sucking the refrigerant into a refrigerant passage of the superconducting conductor. In the apparatus, a plurality of pressure reducers are provided in parallel circuits for each of the refrigerant passages, and the forced cooling conductor is also controlled to increase or decrease the flow rate of the refrigerant in conjunction with an abnormal voltage or a voltage generated by a Pearl magnet. Method. 10. A forced cooling type of superconducting conductors in a plurality of rows, a plurality of liquefying devices for cooling the superconducting conductors, several kinds of cryogenic refrigerants manufactured by the device, and the superconducting conductors containing the refrigerants. In a superconducting device composed of a plurality of decompression devices for sucking into the refrigerant passage, the decompressor is provided in a plurality of parallel circuits for each of the refrigerant passages, and the temperature and pressure on the inlet side,
A feature is that the forced cooling conductor is cooled by providing a relay point capable of adjusting the flow rate of the refrigerant and the manufacturing efficiency of the liquefier by detecting either the temperature in the middle of the superconducting conductor or the temperature on the outlet side. Cooling method for forced cooling conductor. 11. A forced cooling type of superconducting conductors in a plurality of rows, a plurality of liquefying devices for cooling the superconducting conductors, several kinds of cryogenic refrigerants manufactured by the device, and the refrigerants in the superconducting conductors. In a superconducting device composed of a plurality of pressure reducing devices for sucking into the passage of the refrigerant, a plurality of pressure reducing devices are formed in parallel circuit for each of the refrigerant passages, and the temperature at the inlet side,
A pressure sensor, a temperature in the middle of the superconducting conductor, or a temperature on the outlet side can be detected to provide a relay point where the flow rate of the refrigerant and the manufacturing efficiency of the liquefier can be adjusted. A method for cooling a forced cooling conductor, characterized in that a forced cooling conductor is cooled by adjusting a flowing direction and a flow rate.