Superconducting coil device
By employing liquid hydrogen with higher specific heat and lower viscosity, the superconducting coil device achieves efficient cooling and miniaturization, addressing the size and energy consumption issues of existing devices.
Patent Information
- Application Number
- JP2024135415
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-08-14
- Publication Date
- 2026-02-27
AI Technical Summary
Existing superconducting coil devices are large in size due to the need for a large cross-sectional area to manage pressure loss and cooling rate, requiring expensive and scarce helium, which has low specific heat and high viscosity, leading to slow cooling rates and increased energy consumption.
The use of liquid hydrogen with higher specific heat and lower viscosity, combined with a pump and cooling device, allows for a smaller cross-sectional area and efficient cooling, eliminating the need for pressure-resistant equipment and reducing energy consumption.
The superconducting coil device is miniaturized with increased cooling rates and stable operation, reducing energy costs and eliminating the need for expensive helium.
Smart Images
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Abstract
Description
[Technical Field]
[0001] The present invention relates to a superconducting coil device. [Background technology]
[0002] For example, in nuclear fusion devices, superconducting coils are used to confine high-temperature, high-density plasma for long periods of time using magnetic fields. Superconducting coils are made by winding a conduit conductor containing superconducting wires to withstand the powerful electromagnetic forces, and a forced circulation cooling method is used in which cryogenic helium is forced to flow through a flow path formed inside the conduit. The cryogenic helium flowing through the superconducting coils is cooled and pressurized by a helium liquefier before being supplied.
[0003] The cryogenic helium that cooled the superconducting coil rises in temperature and returns to the helium liquefier, but if the temperature rise becomes too great, the superconducting state cannot be maintained. For this reason, it is necessary to control the flow rate of the cryogenic helium flowing through the superconducting coil so that the temperature rise remains within an appropriate range. Since helium in a gas-liquid mixture experiences large pressure fluctuations in the flow path, making it difficult to control the flow rate, in the case of forced circulation systems, it is common to cool the superconducting coil using supercritical helium that has been pressurized to the supercritical state. [Prior art documents] [Non-patent literature]
[0004] [Non-Patent Document 1] Toshiyuki Mito, "Long-term Operational Results of the LHD Cryogenic System," Cryogenic Engineering, Vol. 50, No. 12, 2015 Summary of the Invention [Problem to be solved by the invention]
[0005] However, since helium has a low specific heat, a large flow rate of helium is required to reduce the temperature rise of the helium returning from the superconducting coil, and the cross-sectional area of the flow path must be increased to reduce pressure loss, which requires a larger cross-sectional area of the conduit conductor, resulting in an increase in the size of the superconducting coil device.
[0006] Since the cooling is performed using helium pressurized to a supercritical state, pressure-resistant containers and piping are required. During the initial cooling process, the temperature of the helium gas is gradually lowered to cool the superconducting coil. However, helium gas has a low specific heat and high viscosity, making it difficult for it to flow through the flow path of the superconducting coil. This slows down the cooling rate of the superconducting coil, and it takes a long time to cool it down.
[0007] Therefore, the present invention provides a superconducting coil device that can be made smaller with a simple structure and that can increase the cooling rate of the superconducting coil. [Means for solving the problem]
[0008] In order to solve the above problems, the superconducting coil device according to the present invention comprises a superconducting coil formed by winding a superconducting conductor containing a superconducting wire and having a flow path formed therein for flowing liquid hydrogen, a pump for circulating the liquid hydrogen through the flow path, and a cooling device for cooling the liquid hydrogen.
[0009] This configuration allows the superconducting coil to be cooled efficiently using liquefied hydrogen. Liquid hydrogen has a higher specific heat capacity than cryogenic helium. This allows the cross-sectional area of the flow path for cooling the superconducting coil to be reduced, making it possible to miniaturize the superconducting coil device. Liquefied hydrogen can be used at normal pressure, eliminating the need for pressure-resistant equipment. Hydrogen gas has a lower viscosity and a higher specific heat than helium gas. This allows hydrogen gas to flow easily through the flow path. This allows the cooling rate of the superconducting coil to be increased during the initial cooling process.
[0010] In the above configuration, the temperature of the liquid hydrogen returning from the superconducting coil is maintained at a temperature lower than the boiling point of the liquid hydrogen.
[0011] This configuration prevents the hydrogen in the superconducting coil from becoming a gas-liquid mixture and allows it to always flow as a liquid, which reduces fluctuations in the pressure loss of the liquid hydrogen in the superconducting coil and makes it easier to control the flow rate of the liquid hydrogen flowing through the superconducting coil.
[0012] The above-mentioned configuration further comprises a pressure device that maintains the pressure in the flow path at a predetermined pressure.
[0013] This configuration makes it possible to control the boiling point of the liquid hydrogen, preventing, for example, cavitation in the pump and the generation of bubbles in the flow path, thereby enabling stable operation of the superconducting coil device.
[0014] In the above configuration, the cooling device includes at least one refrigerator.
[0015] By configuring in this way, hydrogen can be reliably cooled with a simple structure. Furthermore, when using multiple refrigerators with different peak efficiencies at different temperatures, each refrigerator can be operated at its most efficient state. For example, when using gas refrigerators, it becomes possible to use hydrogen as the refrigerant for these gas refrigerators. This reduces the operating costs of the superconducting coil device compared to using helium, which is expensive and scarce.
[0016] In the above configuration, the cooling device includes at least one magnetic refrigerator.
[0017] By configuring it in this way, it is possible to cool liquid hydrogen at atmospheric pressure to a temperature below its boiling point without using a gas refrigerator or pressure reducing device that uses helium as a refrigerant, thereby reducing the operating costs of the superconducting coil device. [Effects of the Invention]
[0018] According to the present invention, the superconducting coil device can be made compact with a simple structure, and the cooling rate of the superconducting coil can be increased. [Brief explanation of the drawings]
[0019] [Figure 1] 1 is a schematic diagram of a superconducting coil device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram of a superconducting coil device according to a first modified example of an embodiment of the present invention. [Figure 3] FIG. 10 is a schematic diagram of a superconducting coil device according to a second modified example of an embodiment of the present invention. [Figure 4] FIG. 10 is a schematic diagram of a superconducting coil device according to a third modified example of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION
[0020] Next, an embodiment of the present invention will be described with reference to the drawings.
[0021] <Superconducting coil device> FIG. 1 is a schematic diagram of a superconducting coil device 1. As shown in FIG. As shown in FIG. 1, the superconducting coil 101 of the superconducting coil device 1 is housed in a fusion reactor 102. The superconducting coil 101 is made by winding a conduit conductor containing superconducting wires, and is cooled by flowing liquid hydrogen through a flow path (hereinafter referred to as the flow path) in the conduit conductor. The fusion reactor 102 confines high-temperature, high-density plasma generated by the magnetic field of the superconducting coil 101 for a long period of time. A vacuum insulation layer 103 is provided within the fusion reactor 102 so as to surround the superconducting coil 101. The vacuum insulation layer 103 prevents heat from entering from the outside from being transferred to the superconducting coil 101.
[0022] The superconducting coil device 1 includes a circulation path 2 for circulating liquid hydrogen through the superconducting coil 101, a pressurizing device 3 connected to the circulation path 2, and a pump 4 and a cooling device 5 provided midway along the circulation path 2.
[0023] <Pump> The circulation path 2 is connected to a flow path in the conduit conductor of the superconducting coil 101, and liquid hydrogen is circulated in the flow path in the conduit conductor by circulating hydrogen in the circulation path 2 using a pump 4. In Figure 1, hydrogen is circulated counterclockwise (arrow F in Figure 1) in the circulation path 2. Hereinafter, the upstream side and downstream side may be referred to based on the flow direction of hydrogen in the circulation path 2.
[0024] <Pressure device> The pressurizing device 3 is connected to the circulation path 2 upstream of the pump 4 and downstream of the superconducting coil 101. The pressurizing device 3 includes a buffer tank 7. Hydrogen is stored in the buffer tank 7. The pressure of the hydrogen in the buffer tank 7 is increased to and maintained at a predetermined pressure, thereby maintaining the pressure in the flow path at the predetermined pressure and controlling the boiling point of the liquid hydrogen in the flow path.
[0025] <Cooling device> The cooling device 5 is provided on the circulation path 2 upstream of the pump 4 and downstream of the superconducting coil 101. The cooling device 5 includes a heat exchanger 8 that exchanges heat with the circulation path 2, and one refrigerator 9 connected to the heat exchanger 8. The refrigerator 9 is, for example, a so-called gas refrigerator. The refrigerant used in the refrigerator 9 is, for example, helium gas.
[0026] The liquid hydrogen flowing in the flow path is cooled to a temperature of about 14[K] to 20[K] by the cooling device 5. As a result, the liquid hydrogen flowing in the flow path of the superconducting coil 101 is always maintained in a liquid state. In other words, the temperature of the liquid hydrogen returning from the superconducting coil 101 is maintained at a temperature lower than the boiling point of the liquid hydrogen. Liquid hydrogen has a larger specific heat capacity than cryogenic helium, which has conventionally been used as brine to cool the superconducting coil 101. Therefore, the cross-sectional area of the flow path of the superconducting coil 101 can be reduced, and the superconducting coil 101 can be made smaller.
[0027] Hydrogen has a lower viscosity than helium, and therefore it flows easily through the flow path of the superconducting coil 101. This allows the cooling rate of the superconducting coil 101 to be increased.
[0028] Moreover, the hydrogen is always maintained in the liquid state within the flow path, which means that fluctuations in pressure loss within the flow path are small, making it easy to control the flow rate through the flow path. Furthermore, with conventional superconducting coils that use cryogenic helium, pressure loss in the superconducting coil is large, making it difficult to increase the pressure by the cryogenic circulation pump to compensate for this pressure loss. As a result, it was necessary to increase the pressure using the room-temperature compressor of the helium liquefier. For this reason, the helium returning from the superconducting coil had to be heated in the helium liquefier, pressurized in the compressor, and then cooled to cryogenic temperatures again in the helium liquefier before being circulated to the superconducting coil. In this way, the entire amount of helium circulating in the superconducting coil had to be repeatedly heated to room temperature and cooled to cryogenic temperatures. This resulted in a large amount of energy consumption by the helium liquefier.
[0029] In contrast, when liquid hydrogen is used, the pressure loss in the superconducting coil 101 is small, so it can be circulated by the pump 4. As a result, the liquid hydrogen circulated to the superconducting coil 101 only needs to be cooled by the cooling device 5 by the amount corresponding to the temperature rise in the superconducting coil device. Therefore, the energy consumption of the cooling device 5 can be significantly reduced.
[0030] The superconducting coil device 1 includes a pressure device 3 that maintains the pressure in the circulation path 2 at a predetermined pressure. This makes it possible to prevent, for example, cavitation in the pump 4 and the generation of bubbles in the flow path. As a result, the superconducting coil device 1 can be operated stably. A refrigerator 9 is used as the cooling device 5. In this way, hydrogen can be reliably cooled with a simple structure.
[0031] In the above embodiment, the cooling device 5 is described as including a heat exchanger 8 that exchanges heat with the circulation path 2, and one refrigerator 9 connected to the heat exchanger 8. However, this is not limiting, and the cooling device 5 may be provided midway along the circulation path 2 as long as it can cool hydrogen. Modified examples of the cooling device 5 will be described below.
[0032] [First Modification] <Superconducting coil device> FIG. 2 is a schematic diagram of the superconducting coil device 1 in the first modified example. As shown in Fig. 2, the cooling device 5 may include a plurality of refrigerators 11, 12 (first refrigerator 11, second refrigerator 12). Of the plurality of refrigerators 11, 12, the first refrigerator 11 cools hydrogen via a heat exchanger 8. Of the plurality of refrigerators 11, 12, the second refrigerator 12 cools the exhaust heat of the first refrigerator 11. With this configuration, the hydrogen in the circulation path 2 can be reliably cooled while reducing the cooling capacity of each of the refrigerators 11, 12.
[0033] For example, a magnetic refrigerator can be used as the first refrigerator 11. Magnetic refrigerators utilize the phenomenon (magneto-caloric effect) in which a magnetic material generates heat when a magnetic field is applied to it, and the temperature drops when the magnetic field is removed. A magnetic refrigerator uses a solid magnetic material instead of a refrigerant.
[0034] As the second refrigerator 12, for example, a gas refrigerator can be used. In this first modified example, since two refrigerators 11 and 12 are used, it is also possible to use hydrogen as the refrigerant of the second refrigerator 12. That is, when a hydrogen refrigerant is used, it is difficult to cool the hydrogen in the circulation path 2 to a temperature lower than the boiling point (subcool temperature) using a single refrigerator 9 as in the above-described embodiment. For this reason, it is difficult to use hydrogen as the refrigerant of the refrigerator 9. In contrast, in the first modified example, it is possible to use hydrogen as the refrigerant of the second refrigerator 12.
[0035] Therefore, according to the first modification, in addition to the same effects as the above-described embodiment, the operating costs of the superconducting coil device 1 can be reduced.
[0036] [Second Modification] <Cooling device> FIG. 3 is a schematic diagram of the superconducting coil device 1 in the second modified example. 3, the second modified example differs from the first modified example described above in the method of installing the two refrigerators 11 and 12. That is, in the second modified example, the two refrigerators 11 and 12 are arranged side by side (in series) along the circulation path 2. More specifically, two heat exchangers 13, 14 (first heat exchanger 13 and second heat exchanger 14) are arranged side by side in the circulation path 2. Of the two heat exchangers 13, 14, the first heat exchanger 13 is connected to a first refrigerator 11. Of the two heat exchangers 13, 14, the second heat exchanger 14 is connected to a second refrigerator 12.
[0037] With this configuration, the hydrogen in the circulation path 2 is cooled by the second heat exchanger 14, and then further cooled by the first heat exchanger 13. This cools the hydrogen to a subcooled temperature. For example, in the first heat exchanger 13, the hydrogen that has been cooled to near the liquefaction temperature by the second heat exchanger 14 is further cooled by about 5 [K] to a subcooled state. Therefore, according to the second modified example, it is possible to achieve the same effects as the first modified example.
[0038] In the first and second modified examples described above, the cooling device 5 is described as including two refrigerators 11, 12. However, this is not limited to this, and the number of refrigerators in the first and second modified examples may be three or more. In the first modified example, three or more refrigerators may be connected to each other, and in the second modified example, a heat exchanger may be provided for each of the three or more refrigerators, and the heat exchangers may be arranged side by side in the circulation path 2.
[0039] In the first and second modified examples described above, the two refrigerators 11 and 12 are configured, for example, by a magnetic refrigerator and a gas refrigerator. However, the combination of multiple refrigerators is not limited to a combination of a magnetic refrigerator and a gas refrigerator. The multiple refrigerators may also be configured by only magnetic refrigerators or only gas refrigerators.
[0040] [Third Modification] <Superconducting coil device> FIG. 4 is a schematic diagram of the superconducting coil device 1 in the third modified example. 4, the cooling device 5 may be a decompression type using a sub-cooler tank 15 instead of the refrigerators 9, 11, 12, etc. In this case, the cooling device 5 includes the sub-cooler tank 15 provided on the circulation path 2, and a decompression device 16 and a supply tank 17 connected to the sub-cooler tank 15.
[0041] The sub-cooler tank 15 is made up of a heat-insulating container. Liquid hydrogen is stored in the sub-cooler tank 15. The pressure inside the sub-cooler tank 15 is reduced by a pressure reducing device 16 to maintain the liquid hydrogen state. The pressure reducing device 16 is, for example, a vacuum pump. The pressure inside the sub-cooler tank 15 is evacuated and reduced by the vacuum pump. Liquid hydrogen is also stored in the supply tank 17. The supply tank 17 supplies liquid hydrogen to the sub-cooler tank 15 based on the amount of liquid hydrogen that is reduced by continuing to exhaust and decompress the sub-cooler tank 15. This prevents the liquid hydrogen in the sub-cooler tank 15 from running out.
[0042] Therefore, according to the third modification, the cooling device 5 can have a simple structure, and liquid hydrogen can be circulated in the circulation path 2. Therefore, the superconducting coil 101 can be cooled efficiently.
[0043] The present invention is not limited to the above-described embodiment, and includes various modifications to the above-described embodiment without departing from the spirit of the present invention.
[0044] For example, in the above-described embodiment and each modified example, the pressurizing device 3 is described as including the buffer tank 7. The pressure in the circulation path 2 is maintained at a predetermined pressure by sucking hydrogen from the buffer tank 7 into the circulation path 2 or discharging hydrogen from the circulation path 2 to the buffer tank 7 in response to pressure fluctuations in the circulation path 2. However, the present invention is not limited to this, and the pressurizing device 3 may be any device that can maintain the pressure in the circulation path 2 at a predetermined pressure.
[0045] In the above-described embodiment and each modified example, the case where hydrogen is always maintained in the state of liquid hydrogen in the circulation path 2 has been described. However, this is not limited to this, and hydrogen may be vaporized after heat exchange with the superconducting coil 101. It is sufficient that hydrogen is liquefied at least at the time when hydrogen is supplied to the superconducting coil 101. [Explanation of symbols]
[0046] 1...Superconducting coil device 2…Circulation path 3...Pressure device 4. Pump 5…Cooling device 8...Heat exchanger (cooling device) 9... Refrigerator (cooling device) 11...No. 1 refrigerator (refrigerator, cooling device) 12…Second refrigerator (refrigerator, cooling device) 13...First heat exchanger (cooling device) 14…Second heat exchanger (cooling device) 15...Subcooler tank 16...Decompression device 101...Superconducting coil 102...Fusion reactor 103...Vacuum insulation layer
Claims
1. a superconducting coil formed by winding a superconducting conductor containing a superconducting wire and having a flow path for flowing liquid hydrogen therein; a pump that circulates the liquid hydrogen through the flow path; a cooling device for cooling the liquid hydrogen; Equipped with A superconducting coil device characterized by:
2. The temperature of the liquid hydrogen returning from the superconducting coil is maintained at a temperature lower than the boiling point of the liquid hydrogen.
2. The superconducting coil device according to claim 1.
3. a pressure device that maintains the pressure in the flow path at a predetermined pressure; 3. The superconducting coil device according to claim 1 or 2.
4. The cooling device comprises at least one refrigerator.
3. The superconducting coil device according to claim 1 or 2.
5. The cooling device comprises at least one magnetic refrigerator.
3. The superconducting coil device according to claim 1 or 2.