JPS6123306A - Cooling device of superconductive coil - Google Patents

Abstract

PURPOSE:To enable a forced-cooling system superconductive coil to cool effectively in a short time by a method wherein a coolant path for heat-exchanging which has a smaller flow resistance than a flow resistance of a coolant path inside a conductor is installed and the means to control coolant flow in the coolant path for heat-exchanging is installed. CONSTITUTION:When a coolant 6 from a coolant supply source is sent by pressure with a valve 9 open at the time of initial cooling stage, almost whole coolant 6 is flowed into a coolant path 8 for heat-exchanging and the coil 5 is cooled indirectly, as the temperature of the coil is high and the flow resistance is large. Accordingly, as the temperature of the coil 5 falls and the flow resistance becomes small gradually, the coolant 6 turns to branch to even cooling path 4 side inside the conductor, thus cooling is accelerated. When the coil 5 is enough cooled, the temperature thereof reaches to 50-100K, the valve 9 is closed and the whole coolant 6 is flowed through the coolant path 4. As the result, the temperature of the coil 5 is rapidly fallen and the coil 5 can be turned on conductive that is, superconductive state is attained.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a cooling device for a superconducting coil, and is a forced cooling type superconducting coil suitable for, for example, a superconducting voloidal coil for a nuclear fusion reactor.
This invention relates to a cooling device 1c for conducting coils.

[Background of the invention]

In recent years, as shown in Fig. 4, multiple composite multi-core superconducting wires 2 in which multiple superconducting filaments are embedded in a stabilizing material such as steel or aluminum are used as conduits (pipes).
A superconducting conductor (hereinafter referred to as "conductor") using a forced cooling method has been developed, which is inserted into a conduit 3 and cooled by forcibly flowing a refrigerant such as supercritical pressure helium through the internal space of the conduit 3 as a refrigerant passage 4. There is a growing momentum to use this material to manufacture superconducting coils.

In this type of superconducting coil, since the refrigerant flows through the conductor 1j, that is, the conduit 3, the withstand voltage characteristics of the coil can be improved by electrically insulating the conduit 3, and unlike the immersion cooling type, the coil can be In the refrigerant (liquid helium) [Since a refrigerant container for immersion is not required, the overall structure of the package is simple, and since the refrigerant is forced to flow around the superconducting wire 20, the cooling characteristics are improved, etc. For this reason, the conventional immersion cooling method is being replaced. Possible applications include superconducting boloidal coils for nuclear fusion reactors that generate high voltage, and development efforts are currently underway in various places.

By the way, when a superconducting coil is manufactured by winding this kind of conductor, a problem arises in that the flow resistance of the coolant becomes significantly large. This refrigerant flow resistance is inversely proportional to the cross-sectional area of the refrigerant passage and proportional to the length of the refrigerant passage, so it becomes significantly larger especially when the cross-sectional area of the refrigerant passage is small and the length of the refrigerant passage, that is, the conductor, is long. , it becomes extremely difficult to distribute the refrigerant. Conventionally, therefore, a cooling method has been adopted in which the conductor is made short and a refrigerant is passed in parallel with it.

Such a conventional cooling system is shown in FIGS. 5 and 6. A forced cooling superconducting coil (hereinafter referred to as a coil) 5, which is constructed by winding a conductor l in a solenoid shape or a spiral shape, serves as a refrigerant supply source from initial cooling to warm temperature cooling where a superconducting state can be maintained. Refrigerant 6 is continuously fed under pressure from (not shown) and gradually cooled. coil 5
When the flow pressure loss is small, the refrigerant passage 4 is configured with the L route as shown in FIG. aisle 4
is a plurality of partial passages 4A, 4B, ......4N
[Sectioned, and each of these partial passages are connected in parallel to each other.] In either case, the current 7 is supplied through one route from an excitation power source (not shown). Incidentally, the coil 5 generally consists of a conductor 1 wound several hundred meters to several kilometers long, and the circulation pressure loss of the refrigerant 6 is large, so the cooling method shown in FIG. 6 is often adopted.

In addition, when such a forced cooling method is adopted, the cryostat (not shown) becomes a mere vacuum container, unlike when the conventional immersion cooling method is adopted, as mentioned above, so it cannot be used with other refrigerants. For example, the structure is such that it cannot be precooled with liquid nitrogen. Therefore, cooling of the coil 5 starts from room temperature. Refrigerant 6 pumped from a refrigerant supply source
In some cases, the temperature may be appropriately selected at the beginning and end of cooling, but in any case, during the initial cooling, 1c is the temperature of coil 5.
As the refrigerant flows through the refrigerant, its temperature rises and the flow resistance becomes extremely high, and even if the supply pressure of the refrigerant supply source reaches the upper limit, almost no refrigerant can flow, and it takes a huge amount of time to cool down. Cooling may not be possible on laboratory time scales. Therefore, as mentioned above, a cooling method is adopted in which the refrigerant passage is divided into a plurality of sections and shortened and connected in parallel with each other. Although this is somewhat alleviated, it requires considerable cooling time. In addition, when such a parallel connection cooling method is adopted, the following problems also occur. The first point is that since the refrigerant passages are parallel, the refrigerant flow meter from the refrigerant supply source increases, and the capacity of the refrigerant supply source must be increased, which directly leads to an increase in cost. The second point is that since an unbalance in the refrigerant flow rate occurs between the refrigerant passages connected in parallel, control is required to balance this, and the operation of the coil 5 becomes complicated. In addition, a third point is required, and many branches are required to connect each section of the conductor l that makes up the coil 5 in parallel to the refrigerant 6 and in series to the current 7, so the coil fabrication requires a large number of branches. Not only is this extremely troublesome work, but it also causes a decrease in the reliability of the coil.

[Purpose of the invention]

The purpose of the present invention is to solve the problems of the prior art described above,
An object of the present invention is to provide a cooling device that can efficiently cool a forced cooling type superconducting coil in a short time.

[Summary of the invention]

To achieve this objective, the present invention provides a heat exchange refrigerant passage having a flow resistance smaller than the flow resistance of the refrigerant passage inside the conductor so as to be able to exchange heat in parallel with the forced cooling superconducting coil, Moreover, by providing means for controlling the flow rate of the refrigerant flowing through this heat exchange refrigerant passage, it is possible to indirectly cool the outside of the conductor in addition to the inside of the conductor.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 shows an embodiment in which the refrigerant passage 4 inside the conductor is applied to a coil having one route.

A heat exchange refrigerant passage 8 for indirectly cooling the coil 5 from the outside of the conductor is provided in a state in which sufficient heat can be exchanged with the coil 5 formed by winding the conductor l and in parallel with the refrigerant passage 4 inside the conductor. There is. The heat exchange refrigerant passage 8 is formed so that its flow resistance is much smaller than that of the refrigerant passage 4, and a pulp 9 is provided on the inlet side thereof. Also,
This heat exchange refrigerant passage 8 may be installed inside the coil 5, or may be installed in contact with the surface of the coil 5. Further, its structure may be a simple tubular structure, a tubular structure with cooling fins, or a container-like structure in which the refrigerant 6 can be stored.

In a cooling device having such a VC configuration, when the refrigerant 6 is pumped from the refrigerant supply source with the pulp 9 open during initial cooling, the temperature of the coil 5 is high and the flow resistance of the refrigerant 6 is extremely large. Almost all refrigerant passages for heat exchange 8
and cools the coil 5 indirectly. Along with this, the temperature of the coil 5 decreases and its flow resistance gradually decreases, so that the refrigerant 6 also flows to the refrigerant passage 4 side inside the conductor, and cooling is accelerated. When the coil 5 is sufficiently cooled to a temperature of 50 to 100 K, the pulp 9 is closed and all of the refrigerant 6 is allowed to flow into the refrigerant passage 4.

As a result, the temperature of the coil 5 decreases rapidly, and the coil 5 can be brought into a state where it can be energized, that is, into a superconducting state. In this embodiment, pulp can be provided not only at the heat exchange refrigerant passage 8 but also at the entrance of the refrigerant passage 40.

Further, Fig. 2 shows an example in which the refrigerant passage 4 inside the conductor is applied to a coil configured of a plurality of routes connected in parallel. Although one route of heat exchange refrigerant passage 8 is provided as in the embodiment shown in FIG. 1, it is also possible to provide a plurality of routes connected in parallel. However, it is better to keep the number of these multiple routes as small as possible.

FIG. 3 shows an embodiment of the present invention with a more specific structure. This embodiment is an example in which the conductor l is wound in a double pancake shape. Each turn of the conductor l and between the pancakes are electrically insulated with an insulator 12, and cooling fins 10 made of a good thermal conductor such as copper or aluminum are inserted between the pancakes in an insulated state, and A heat exchange refrigerant passage 8 is attached to the outer periphery of the cooling fin IO in a spirally wound state, and is also attached to a bobbin 11.

The superconducting coil 5 shown in FIG. 3 was manufactured as a prototype, and the results of experiments conducted with and without the heat exchange refrigerant passage 8 will be briefly described.

The fourth conductor L was constructed by inserting 30 superconducting wires 2 with a diameter of 1 mm into a concrete 3 with a refrigerant passage cross section of 7 mm square.
Using a conductor having the structure shown in the figure, a coil 5 with an inner diameter of 100 mm, an outer diameter of 200 mm, a height of 200 mm, and a winding i of 72 turns was manufactured. Moreover, a combination of a compressor and a heat exchanger was used as a refrigerant supply source. At first, when we conducted a cooling experiment for the case without the heat exchange refrigerant passage 8, we found that it took 18 hours to start cooling from room temperature and for supercritical pressure helium to flow inside the conductor 1, and then inside the heat exchanger. The amount of liquid helium used was 15,001. On the other hand, when we conducted a cooling experiment with a heat exchange refrigerant passage 8 and cooling fins 10 as shown in Figure 3, the time was shortened to one-sixth, and the consumption of 1 noum to liquid was could be reduced to one-tenth.

In the embodiment shown in FIG. 3, since the conductor l is wound in a pancake shape, the cooling fins lO are arranged perpendicularly to the winding axis of the coil 5, but the conductor l is wound in a solenoid shape. In the case where the cooling fins IO are arranged parallel to the winding axis of the coil 5, the heat exchange refrigerant passage 8 may be attached to the externally projecting end thereof in a spiral f-wound state.

〔Effect of the invention〕

As explained above, according to the present invention, the conductor has a flow resistance smaller than the flow resistance of the refrigerant passage inside the conductor so as to be able to exchange heat in parallel with a forced cooling type superconducting coil having a refrigerant passage inside the conductor. By providing a refrigerant passage for heat exchange and a means for controlling the flow rate of the refrigerant flowing through this refrigerant passage for heat exchange, 5VC can be indirectly cooled not only from the inside of the conductor but also from the outside of the conductor. It would be possible to efficiently cool superconducting coils using cooling methods in a short time.

As a result, for example, it becomes possible to significantly shorten the initial cooling time and to significantly reduce the amount of refrigerant consumed for cooling.

[Brief explanation of the drawing]

1 and 2 are system diagrams showing the basic configuration of cooling devices according to different embodiments of the present invention, and FIG. 3 is a sectional view showing the specific configuration of a cooling device according to an embodiment of the present invention. , FIG. 4 is a sectional view of a forcedly cooled superconducting conductor, and FIGS. 5 and 6 are system diagrams showing the basic configurations of different conventional forced cooling superconducting coil cooling devices. ■...Conductor, 4...Refrigerant passage inside the conductor, 5...Superconducting coil, 6...Refrigerant, 8...Heat exchange refrigerant passage, 9...valve, lO...cooling fin. N-, -11↓ N4, B” Pe! Gin

Claims (1)

[Claims] 1. In a superconducting coil formed by winding a superconducting conductor having a refrigerant passage inside the conductor, the flow resistance of the refrigerant passage inside the conductor is higher than the flow resistance of the refrigerant passage inside the conductor so that heat exchange can be performed in parallel with the superconducting coil. 1. A cooling device for a superconducting coil, characterized in that a heat exchange refrigerant passage with low flow resistance is provided, and means for controlling the flow rate of refrigerant flowing through the heat exchange refrigerant passage. 2. A superconducting coil according to claim 1, characterized in that cooling fins are provided in thermally conductive contact with a plurality of turns of the superconducting conductor, and the cooling fins are connected to the heat exchange refrigerant passage. Cooling system.