Ultralow temperature cooling system and ultralow temperature cooling method

Abstract

To make it possible, even when a failure occurs in a control valve for controlling a flow quantity of coolant to be made to flow through a plurality of superconducting coils, to cool the superconducting coils continuously.SOLUTION: An ultralow temperature cooling system 10 includes: a plurality of high-temperature superconducting coils 11A, 11B and an ultralow temperature refrigerator 12 that are connected by a cooling pipeline 13 comprising a plurality of branched branch pipeline parts 14A, 14B correspondingly to the high-temperature superconducting coils; and control valves 18A, 18B that are arranged on the branch pipeline parts, and control flow quantities of coolant flowing from the ultralow temperature refrigerator to the high-temperature superconducting coils. On the respective branch pipeline parts 14A, 14B are provided bypass pipelines 41, 42 that bypass the control valves 18A, 18B and comprise bypass valves 43, 44. The bypass valves 43, 44 are configured using differential pressure driving valves that are opened when a pressure difference between their upstream side and downstream side exceeds a predetermined pressure difference.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] Embodiments of the present invention relate to a cryogenic cooling system and a cryogenic cooling method.

Background Art

[0002] Generally, superconducting devices need to be cooled to cryogenic temperatures. In recent years, high-temperature superconductors and high-temperature superconducting magnets using them have been developed, and the cooling temperature has increased from around 4K in the past to about 20K. In this temperature range, the power required for cooling generally decreases in inverse proportion to the absolute temperature, so it has become possible to apply high-temperature superconducting magnets to devices with a large heat load. As a result, a large refrigeration capacity is often required in the cooling system of high-temperature superconducting devices.

[0003] In addition, since the cooling temperature is high, the conventional method using liquid helium is not suitable. For this reason, a method of cooling a high-temperature superconducting magnet by a conduction cooling method or a gas circulation method using a mechanical refrigerator is used. In particular, in a cooling system with a large heat load, in the conduction cooling method, there is a problem that the temperature difference between the refrigerator and the high-temperature superconducting magnet becomes large and the temperature of the high-temperature superconducting magnet becomes high, so the gas circulation cooling method is suitable.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, as shown in FIG. 7, consider a large-scale cryogenic cooling system 100 that uses a plurality of high-temperature superconducting magnets 101. Such a cryogenic cooling system 100 has a piping configuration in which a cooling pipe 103 that circulates a gas refrigerant by a circulation pump 102 is branched to include a plurality of parallel branched pipe portions 104, and each branched pipe portion 104 is connected to the high-temperature superconducting magnet 101. However, in such a piping configuration, there is a problem of instability of the gas refrigerant flow.

[0006] This is the case where, as shown in FIG. 8(B) from the state shown in FIG. 8(A), when an imbalance in the heat load occurs in the high-temperature superconducting magnet 101 (the heat load is indicated by the size of the arrow in the figure), the temperature of the branched pipe portion 104 connected to the high-temperature superconducting magnet 101 with a large heat load rises, and due to this temperature rise, the pressure loss of the branched pipe portion 104 increases and it becomes difficult for the gas refrigerant to flow, and furthermore, a negative chain occurs in which the temperature of the branched pipe portion 104 rises. Therefore, a method is taken in which a control valve 105 is provided in each branched pipe portion 104 arranged in parallel to control the flow rate of the gas refrigerant flowing through each branched pipe portion 104. Note that reference numeral 106 in FIG. 7 indicates a heat exchanger.

[0007] However, in the cryogenic cooling system 100 of the gas circulation method described above, there is a problem that impurities in the circulating gas refrigerant accumulate on the control valve 105 and the control valve 105 becomes blocked. When the control valve 105 is blocked, it becomes difficult for the gas refrigerant to flow through the branched pipe portion 104 in which the control valve 105 is disposed, and there is a problem that the temperature of the high-temperature superconducting magnet 101 being cooled by this branched pipe portion 104 rises and quenching occurs. Further, even if the control valve 105 is not completely blocked, the same problem occurs when the control of the control valve 105 becomes impossible due to a significant increase in the pressure loss or in the case of a failure of the control system.

[0008] The embodiment of the present invention has been made in consideration of the above circumstances, and an object thereof is to provide a cryogenic cooling system and a cryogenic cooling method capable of continuously cooling a superconducting coil even when a problem such as blockage occurs in a control valve that controls the flow rate of the refrigerant flowing through each of a plurality of superconducting coils.

Means for Solving the Problem

[0009] In the cryogenic cooling system according to an embodiment of the present invention, a cryogenic refrigerator and a plurality of objects to be cooled are connected by a cooling pipe including a branch pipe portion branched into a plurality corresponding to the objects to be cooled, and a control valve is disposed in each of the branch pipe portions. In the cryogenic cooling system in which the flow rate of the refrigerant flowing from the cryogenic refrigerator to the object to be cooled is controlled by the control valve to cool the object to be cooled, a bypass pipe including a bypass valve is provided in each of the branch pipe portions to bypass the control valve, and the bypass valve is configured by a differential pressure-driven valve that is opened when a pressure difference between its upstream side and downstream side exceeds a predetermined pressure difference.

[0010] In the cryogenic cooling method according to an embodiment of the present invention, refrigerant is flowed from a cryogenic refrigerator to a plurality of objects to be cooled through a plurality of branch pipe portions of a cooling pipe, and the flow rate of the refrigerant is controlled by a control valve disposed in each of the branch pipe portions to cool the object to be cooled. In the cryogenic cooling method, a bypass pipe including a bypass valve is provided in each of the branch pipe portions to bypass the control valve, the bypass valve is a differential pressure-driven valve, and when a pressure difference between its upstream side and downstream side exceeds a predetermined pressure difference, the bypass valve is opened to supply the refrigerant to the object to be cooled through the bypass pipe.

Advantages of the Invention

[0011] According to an embodiment of the present invention, even when a problem such as blockage occurs in the control valve that controls the flow rate of the refrigerant flowing through each of the plurality of superconducting coils, the superconducting coils can be continuously cooled.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. [A] First Embodiment (FIG. 1) FIG. 1 is a pipeline diagram showing a cryogenic cooling system according to the first embodiment. The cryogenic cooling system 10 shown in this FIG. 1 cools a plurality of high-temperature superconducting coils (for example, high-temperature superconducting coils 11A and 11B) as objects to be cooled in a gas circulation method, and includes a cryogenic refrigerator 12, a cooling pipe 13 provided with a plurality of branch pipe sections (for example, branch pipe sections 14A and 14B), a circulation pump 15, heat exchangers 16 and 17, a plurality of control valves (for example, control valves 18A and 18B), a connection pipe 19 provided with a connection valve 20, a plurality of temperature measuring means (for example, temperature measuring means 21A and 21B), and a control unit 22.

[0014] The cryogenic refrigerator 12 has a first cooling stage 12N and a second cooling stage 12M, and these first cooling stage 12N and second cooling stage 12M are connected in series to the cooling pipe 13. Further, the branch pipe portions 14A, 14B of the cooling pipe 13 are arranged in a plurality of parallel corresponding to the plurality of high-temperature superconducting coils 11A, 11B, and each is connected to the high-temperature superconducting coils 11A, 11B. Thereby, the cryogenic refrigerator 12 and the high-temperature superconducting coils 11A, 11B are connected by the cooling pipe 13.

[0015] The circulation pump 15 circulates a gas refrigerant such as helium gas in the loop-shaped cooling pipe 13, and may be a compressor or a blower or the like. The gas refrigerant is sequentially fed to the first cooling stage 12N and the second cooling stage 12M of the cryogenic refrigerator 12 by the circulation pump 15 and cooled step by step.

[0016] The heat exchanger 16 is disposed in the cooling pipe 13, and cools the refrigerant flowing from the first cooling stage 12N to the second cooling stage 12M of the cryogenic refrigerator 12 by heat exchange with the gas refrigerant after cooling the high-temperature superconducting coils 11A and 11B. Further, the heat exchanger 17 is disposed in the cooling pipe 13, and cools the refrigerant flowing to the first cooling stage 12N of the cryogenic refrigerator 12 by heat exchange with the gas refrigerant flowing out of the heat exchanger 16.

[0017] Each of the control valves 18A, 18B is disposed in each of the branch pipe portions 14A, 14B of the cooling pipe 13. The gas refrigerant flowing in the cooling pipe 13 by the action of the circulation pump 15 and sequentially cooled step by step by the heat exchanger 17, the first cooling stage 12N of the cryogenic refrigerator 12, the heat exchanger 16, and the second cooling stage 12M of the cryogenic refrigerator 12 flows to the high-temperature superconducting coil 11A through the branch pipe portion 14A of the cooling pipe 13 and to the high-temperature superconducting coil 11B through the branch pipe portion 14B, and cools these high-temperature superconducting coils 11A and 11B. At this time, when there is an imbalance in the heat load in the high-temperature superconducting coils 11A, 11B, the control valves 18A, 18B perform flow control to preferably ensure the flow rate of the gas refrigerant flowing in the branch pipe portions 14A, 14B, and cool the high-temperature superconducting coils 11A and 11B well.

[0018] The connecting pipe 19 is a pipe that connects the downstream sides of the control valves 18A and 18B in the plurality of branch pipe portions 14A and 14B of the cooling pipe 13. For example, one connecting pipe 19 connects two of the plurality of branch pipe portions 14A and 14B on the downstream sides of the control valves 18A and 18B.

[0019] Regarding the connection valve 20 arranged in this connecting pipe 19, the control unit 22 controls its opening degree based on the temperature measurement values from the temperature measurement means 21A and 21B. That is, the temperature measurement means 21A is installed in the high-temperature superconducting coil 11A to measure the temperature of the high-temperature superconducting coil 11A, and the temperature measurement means 21B is installed in the high-temperature superconducting coil 11B to measure the temperature of the high-temperature superconducting coil 11B. The temperature measurement values from these temperature measurement means 21A and 21B are input to the control unit 22.

[0020] When the temperature measurement values from the temperature measurement means 21A and 21B rise rapidly, that is, when the change rate of the temperature measurement value exceeds a predetermined value, the control unit 22 determines that a problem such as blockage has occurred in the control valve 18A or 18B through which the gas refrigerant flows in the high-temperature superconducting coil 11A or 11B where the temperature measurement means 21A or 21B that measured this temperature measurement value is installed. Then, the control unit 22 opens (fully opens) the connection valve 20 provided in the connecting pipe 19 on the downstream side of the control valve 18A or 18B where this problem has occurred.

[0021] That is, the control unit 22 opens the connection valve 20 of the connecting pipe 19 that connects the branch pipe portion 14A or 14B where the flow of the gas refrigerant has become poor due to a problem with the control valve 18A or 18B and the branch pipe portion 14B or 14A where the flow of the gas refrigerant is good. Thereby, through the opened connection valve 20, the branch pipe portion 14A or 14B having the defective control valve 18A or 18B and having a poor flow of the gas refrigerant is supplied with the gas refrigerant from the branch pipe portion 14B or 14A having the good control valve 18B or 18A and having a good flow of the gas refrigerant.

[0022] Further, when the temperature measurement values from the temperature measurement means 21A and 21B exceed a predetermined value, the control unit 22 opens the connection valve 20 provided in the connection pipe 19 on the downstream side of the control valve 18A or 18B regardless of whether there is a defect (e.g., blockage) in the control valve 18A or 18B through which the gas refrigerant flows to the high-temperature superconducting coil 11A or 11B where the temperature measurement means 21A or 21B that measured this temperature measurement value is installed. Thereby, via the opened connection valve 20, it becomes possible to branch and supply the gas refrigerant from the branch pipe section 14B or 14A provided with the other control valve 18B or 18A to the high-temperature superconducting coil 11A or 11B where the temperature measurement means 21A or 21B with a temperature measurement value exceeding the predetermined value is installed.

[0023] Due to being configured as described above, according to the first embodiment, the following effect (1) is achieved. (1) In the cryogenic cooling system 10, the gas refrigerant flows from the cryogenic refrigerator 12 through the plurality of branch pipe sections 14A and 14B of the cooling pipe 13 to the plurality of high-temperature superconducting coils 11A and 11B, and the flow rate of the gas refrigerant is controlled by the control valves 18A and 18B provided in the respective branch pipe sections 14A and 14B, thereby cooling the high-temperature superconducting coils 11A and 11B. Further, in the cryogenic cooling system 10, the plurality of branch pipe sections 14A and 14B are connected by a connection pipe 19 having a connection valve 20 on the downstream side of the control valves 18A and 18B. When a defect occurs in the control valve 18A or 18B, the connection valve 20 provided in the connection pipe 19 on the downstream side of this defective control valve 18A or 18B is opened, and via this connection valve 20, the gas refrigerant is branched from the branch pipe section 14B or 14A provided with the good control valve 18B or 18A to the branch pipe section 14A or 14B provided with the defective control valve 18A or 18B. As a result, the high-temperature superconducting coils 11A and 11B can be continuously cooled.

[0024] [B]Second Embodiment (FIG. 2) FIG. 2 is a piping diagram showing a part of the cryogenic cooling system according to the second embodiment. Regarding the parts similar to those in the first embodiment in this second embodiment, the same reference numerals as those in the first embodiment are given to simplify or omit the description. Note that FIG. 2 shows the configuration below the cryogenic refrigerator in the cryogenic cooling system shown in FIG. 1.

[0025] The difference between the cryogenic cooling system 25 of this second embodiment and the first embodiment is that a plurality of flow rate measuring means (for example, flow rate measuring means 26A, 26B) for measuring the flow rate of the gas refrigerant flowing inside are provided in each of a plurality of branch pipe portions (for example, branch pipe portions 14A, 14B) of the cooling pipe 13, and the control unit 27 inputs the flow rate measurement values from the respective flow rate measuring means 26A, 26B and controls the opening degree of the connection valve 20 provided in the connection pipe 19.

[0026] That is, when the flow rate measurement values from the flow rate measuring means 26A, 26B drop below a predetermined flow rate, the control unit 27 determines that a problem such as blockage has occurred in the control valve 18A or 18B disposed in the branch pipe portion 14A or 14B where the flow rate measuring means 26A or 26B that measured this flow rate measurement value is provided. Then, the control unit 27 opens (fully opens) the connection valve 20 provided in the connection pipe 19 on the downstream side of the control valve 18A or 18B in which this problem has occurred.

[0027] That is, the control unit 27 opens the connection valve 20 of the connection pipe 19 that connects the branch pipe portion 14A or 14B where the flow of the gas refrigerant has become poor due to a problem with the control valve 18A or 18B and the branch pipe portion 14B or 14A where the flow of the gas refrigerant is good. Thereby, through the opened connection valve 20, the gas refrigerant is supplied from the branch pipe portion 14B or 14A having a good control valve 18B or 18A and a good flow of the gas refrigerant to the branch pipe portion 14A or 14B having a defective control valve 18A or 18B and a poor flow of the gas refrigerant.

[0028] As described above, in the second embodiment, the flow rate of the gas refrigerant flowing in the branch pipe portions 14A and 14B of the cooling pipe 13 that supplies the gas refrigerant to the high-temperature superconducting coils 11A and 11B is measured, and the malfunction of the control valves 18A and 18B provided in the branch pipe portions 14A and 14B is determined. Then, control is performed to open the connection valve 20 provided in the connection pipe 19 on the downstream side of the malfunctioning control valve 18A or 18B. Therefore, also in the second embodiment, similar to the effect (1) of the first embodiment, the high-temperature superconducting coils 11A and 11B can be continuously cooled.

[0029] [C] Third Embodiment (FIG. 3) FIG. 3 is a pipeline diagram showing a part of the cryogenic cooling system according to the third embodiment. Regarding the parts similar to those in the first embodiment in this third embodiment, the description is simplified or omitted by attaching the same reference numerals as those in the first embodiment. Note that FIG. 3 shows the configuration below the cryogenic refrigerator in the cryogenic cooling system shown in FIG. 1.

[0030] The difference between the cryogenic cooling system 30 of this third embodiment and the first embodiment is that the downstream sides of the control valves 18A and 18B in a plurality of branch pipe portions (for example, branch pipe portions 14A and 14B) of the cooling pipe 13 are connected by connection pipes 31 and 32, and a differential pressure driven valve 33 is provided in the connection pipe 31, and a differential pressure driven valve 34 is provided in the connection pipe 32, and they are respectively arranged as connection valves.

[0031] The differential pressure driven valves 33 and 34 are normally in a closed valve state by the biasing force of an elastic body such as a spring, but are opened when the pressure difference between their upstream side and downstream side exceeds a predetermined pressure difference.

[0032] That is, the differential pressure-driven valve 33 is opened, for example, when a problem such as blockage occurs in the control valve 18A and the pressure in the branch pipe portion 14A becomes lower than the pressure in the branch pipe portion 14B by more than a predetermined pressure value, and the gas refrigerant in the branch pipe portion 14B flows into the branch pipe portion 14A through the connecting pipe 31 and the differential pressure-driven valve 33. Further, the differential pressure-driven valve 34 is opened, for example, when a problem such as blockage occurs in the control valve 18B and the pressure in the branch pipe portion 14B becomes lower than the pressure in the branch pipe portion 14A by more than a predetermined pressure difference, and the gas refrigerant in the branch pipe portion 14A flows into the branch pipe portion 14B through the connecting pipe 32 and the differential pressure-driven valve 34.

[0033] As described above, in the third embodiment, when the pressure difference in the branch pipe portions 14A and 14B of the cooling pipe 13 that supplies the gas refrigerant to the high-temperature superconducting coils 11A and 11B exceeds a predetermined pressure difference, the differential pressure-driven valve 33 of the connecting pipe 31 that connects the branch pipe portions 14A and 14B, or the differential pressure-driven valve 34 of the connecting pipe 32 is opened. Therefore, even when a problem such as blockage occurs in the control valve 18A provided in the branch pipe portion 14A or the control valve 18B provided in the branch pipe portion 14B, the gas refrigerant flows from the branch pipe portion 14B to the branch pipe portion 14A through the connecting pipe 31 and the differential pressure-driven valve 33, and from the branch pipe portion 14A to the branch pipe portion 14B through the connecting pipe 32 and the differential pressure-driven valve 34. As a result, similar to the effect (1) of the first embodiment, the high-temperature superconducting coils 11A and 11B can be continuously cooled.

[0034] [D] Fourth Embodiment (FIG. 4) FIG. 4 is a pipeline diagram showing a part of the cryogenic cooling system according to the fourth embodiment. For parts that are the same as those in the first embodiment in this fourth embodiment, the same reference numerals as those in the first embodiment are used to simplify or omit the description. Note that FIG. 4 shows the configuration below the cryogenic refrigerator in the cryogenic cooling system shown in FIG. 1.

[0035] The cryogenic cooling system 40 of this fourth embodiment is different from that of the first embodiment in that there are no connecting pipes and connecting valves, and bypass pipes 41 and 42 are provided for a plurality of branch pipe portions (for example, branch pipe portions 14A and 14B) of the cooling pipe 13 to bypass the control valves 18A and 18B respectively. Differential pressure driven valves 43 and 44 that function as bypass valves are respectively disposed in the bypass pipes 41 and 42.

[0036] The differential pressure driven valves 43 and 44 are normally in a closed valve state by the biasing force of an elastic body such as a spring, but are opened when the pressure difference between the upstream side and the downstream side exceeds a predetermined pressure difference.

[0037] That is, for example, when a problem such as blockage occurs in the control valve 18A and the pressure on the downstream side of the control valve 18A in the branch pipe portion 14A becomes lower than the pressure on the upstream side by more than a predetermined pressure difference, the differential pressure driven valve 43 is opened, and the gas refrigerant on the upstream side of the control valve 18A in the branch pipe portion 14A flows to the downstream side of the control valve 18A through the bypass pipe 41. Also, for example, when a problem such as blockage occurs in the control valve 18B and the pressure on the downstream side of the control valve 18B in the branch pipe portion 14B becomes lower than the pressure on the upstream side by more than a predetermined pressure difference, the differential pressure driven valve 44 is opened, and the gas refrigerant on the upstream side of the control valve 18B in the branch pipe portion 14B flows to the downstream side of the control valve 18B through the bypass pipe 42.

[0038] As described above, in the fourth embodiment, when the pressure difference between the upstream side and the downstream side of the control valves 18A and 18B provided in the branch pipe portions 14A and 14B of the cooling pipes 13 that supply the gas refrigerant to the high-temperature superconducting coils 11A and 11B exceeds a predetermined pressure difference, the differential pressure-driven valves 43 and 44 provided in the bypass pipes 41 and 42 are opened. Therefore, when a problem such as blockage occurs in the control valve 18A or 18B, the differential pressure-driven valve 43 or 44 is opened, and the gas refrigerant is supplied to the high-temperature superconducting coil 11A or 11B through the bypass pipe 41 or 42. As a result, similar to the effect (1) of the first embodiment, even when a problem occurs in the control valves 18A and 18B, the high-temperature superconducting coils 11A and 11B can be continuously cooled.

[0039] [E]Fifth Embodiment (FIG. 5) FIG. 5 is a pipeline diagram showing a part of the cryogenic cooling system according to the fifth embodiment. For the parts similar to those in the first embodiment in this fifth embodiment, the same reference numerals as those in the first embodiment are used to simplify or omit the description. Note that FIG. 5 shows the configuration below the cryogenic refrigerator in the cryogenic cooling system shown in FIG. 1.

[0040] The difference between the cryogenic cooling system 50 of this fifth embodiment and the first embodiment is that there are no connecting pipes and connecting valves, a plurality of high-temperature superconducting coils (for example, high-temperature superconducting coils 11A and 11B) 11 are thermally connected by a heat transfer member 51, the temperatures of the high-temperature superconducting coils 11A and 11B are measured by temperature measuring means 21A and 21B, and a control unit 52 for controlling the opening degrees of the control valves 18A and 18B is provided.

[0041] That is, first, when a problem such as blockage occurs in the control valve 18A or 18B and the temperature of the high-temperature superconducting coil 11A or 11B rises, the control unit 52 determines the occurrence of the problem based on the temperature measurement value of the temperature measurement means 21A or 21B. Next, the control unit 52 increases the opening degree of the good control valve 18B or 18A in which no problem has occurred, supplies more gas refrigerant by the high-temperature superconducting coil 11B or 11A, and cools the high-temperature superconducting coil 11A or 11B connected to the control valve 18A or 18B in which the problem has occurred by heat conduction through the heat transfer member 51.

[0042] As described above, since the high-temperature superconducting coils 11A and 11B are thermally connected by the heat transfer member 51, even when a problem occurs in the control valves 18A and 18B, the high-temperature superconducting coils 11A and 11B can be continuously cooled by heat conduction of the heat transfer member 51, similar to the effect (1) of the first embodiment.

[0043] [F]Sixth Embodiment (Fig. 6) Fig. 6 is a pipeline diagram showing a part of the cryogenic cooling system according to the sixth embodiment. Regarding the parts similar to those in the first and second embodiments in this sixth embodiment, the description is simplified or omitted by attaching the same reference numerals as those in the first and second embodiments. Note that Fig. 6 shows the configuration below the cryogenic refrigerator in the cryogenic cooling system shown in Fig. 1.

[0044] The difference between the cryogenic cooling system 60 of this sixth embodiment and the first and second embodiments is that there are no connecting pipes and connecting valves, and each of a plurality of high-temperature superconducting coils (for example, high-temperature superconducting coils 11A and 11B), that is, a plurality of branch pipe parts (for example, branch pipe parts 14A-1 and 14A-2) are connected to a single high-temperature superconducting coil 11A, and a plurality of branch pipe parts (for example, branch pipe parts 14B-1 and 14B-2) are connected to a single high-temperature superconducting coil 11B.

[0045] Furthermore, in the cryogenic cooling system 60, flow rate measuring means 26A-1, 26A-2, 26B-1, and 26B-2 are respectively disposed in each of the branch pipe portions 14A-1, 14A-2, 14B-1, and 14B-2. Also, in the cryogenic cooling system 60, a control unit 62 is provided for controlling the opening degrees of the control valves 18A-1, 18A-2, 18B-1, and 18B-2 respectively provided in the branch pipe portions 14A-1, 14A-2, 14B-1, and 14B-2.

[0046] That is, first, the control unit 62 determines, based on the flow rate measurement values of the flow rate measuring means 26A-1, 26A-2, 26B-1, and 26B-2, that a problem such as blockage has occurred in the control valves 18A-1, 18A-2, 18B-1, and 18B-2. Suppose a problem has occurred in the control valve 18A-1 and the control valve 18B-1. Then, the control unit 62 next increases the opening degrees of the good control valves 18A-2 and 18B-2 in which no problem has occurred, increases the refrigerant flow rate flowing through each of the branch pipe portions 14A-2 and 14B-2, and thereby continuously ensures the cooling of the high-temperature superconducting coils 11A and 11B.

[0047] As described above, the single high-temperature superconducting coil 11A is connected to the branch pipe portions 14A-1 and 14A-2 which are a plurality of branch pipe portions, and the single high-temperature superconducting coil 11B is connected to the branch pipe portions 14B-1 and 14B-2 which are a plurality of branch pipe portions. Therefore, even if a problem occurs in either of the control valves 18A-1 and 18A-2 respectively provided in the branch pipe portions 14A-1 and 14A-2, the gas refrigerant can be supplied from the branch pipe portion 14A-2 or 14A-1 having the good control valve 18A-2 or 18A-1 in which no problem has occurred to the high-temperature superconducting coil 11A. As a result, similar to the effect (1) of the first embodiment, the high-temperature superconducting coils 11A and 11B can be continuously cooled.

[0048] As described above, several embodiments of the present invention have been explained. However, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the gist of the invention. Also, those replacements, changes, and combinations are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0049] 10… cryogenic cooling system, 11A, 11B… high-temperature superconducting coil, 12… cryogenic refrigerator, 13… cooling pipe, 14A, 14A-1, 14A-2, 14B, 14B-1, 14B-2… branch pipe section, 18A, 18B… control valve, 19… connecting pipe, 20… connecting valve, 21A, 21B… temperature measuring means, 22… control unit, 25… cryogenic cooling system, 26A, 26B… flow rate measuring means, 27… control unit, 30… cryogenic cooling system, 31, 32… connecting pipe, 33, 34… differential pressure driving valve, 40… cryogenic cooling system, 41, 42… bypass pipe, 43, 44… differential pressure driving valve, 50… cryogenic cooling system, 51… heat transfer member, 52… control unit, 60… cryogenic cooling system, 62… control unit

Claims

1. An ultra-low temperature refrigerator and a plurality of objects to be cooled are connected by a cooling pipe provided with a branched pipe portion branched into a plurality corresponding to the objects to be cooled, and a control valve is disposed in each branched pipe portion. In an ultra-low temperature cooling system in which the flow rate of the refrigerant flowing from the ultra-low temperature refrigerator to the object to be cooled is controlled by the control valve to cool the object to be cooled. Each branched pipe portion is provided with a bypass pipe that bypasses the control valve and includes a bypass valve. The ultra-low temperature cooling system is characterized in that the bypass valve is constituted by a differential pressure-driven valve that is opened when the pressure difference between its upstream side and downstream side exceeds a predetermined pressure difference.

2. An ultra-low temperature refrigerator and a plurality of objects to be cooled are connected by a cooling pipe provided with a branched pipe portion branched into a plurality corresponding to the objects to be cooled, and a control valve is disposed in each branched pipe portion. In an ultra-low temperature cooling system in which the flow rate of the refrigerant flowing from the ultra-low temperature refrigerator to the object to be cooled is controlled by the control valve to cool the object to be cooled. The ultra-low temperature cooling system is characterized in that a plurality of the objects to be cooled are thermally connected by a heat transfer member.

3. It further includes temperature measuring means provided for each object to be cooled to measure the temperature of the object to be cooled, and a control unit that inputs a temperature measurement value from the temperature measuring means. When the rate of change of the temperature measurement value exceeds a predetermined value, the control unit determines that a malfunction has occurred in the control valve that allows the refrigerant to flow through the object to be cooled where the temperature measuring means that measured the temperature measurement value is installed, and is configured to increase the opening degree of the control valve in which no such malfunction has occurred. The ultra-low temperature cooling system according to claim 2, characterized in that.

4. An ultra-low temperature refrigerator and a plurality of objects to be cooled are connected by a cooling pipe provided with a branched pipe portion branched into a plurality corresponding to the objects to be cooled, and a control valve is disposed in each branched pipe portion. In an ultra-low temperature cooling system in which the flow rate of the refrigerant flowing from the ultra-low temperature refrigerator to the object to be cooled is controlled by the control valve to cool the object to be cooled. The ultra-low temperature cooling system is characterized in that the branched pipe portion is configured by connecting a plurality of pipes to a single object to be cooled.

5. It further includes flow rate measuring means provided for each branched pipe portion to measure the flow rate of the refrigerant flowing through the inside of the branched pipe portion, and a control unit that inputs a flow rate measurement value from the flow rate measuring means. When the flow rate measurement value drops below a predetermined flow rate, the control unit determines that a malfunction has occurred in the control valve disposed in the branch piping section where the flow rate measuring means that measured this flow rate measurement value is provided, and is configured to increase the opening degree of the control valve in which no such malfunction has occurred. The cryogenic cooling system according to claim 4, characterized in that.

6. In a cryogenic cooling method of flowing a refrigerant from a cryogenic refrigerator to a plurality of objects to be cooled through a plurality of branch piping sections of a cooling pipe and controlling the flow rate of the refrigerant by a control valve disposed in each of the branch piping sections to cool the objects to be cooled, Each of the branch piping sections is provided with a bypass pipe that bypasses the control valve and is provided with a bypass valve. The bypass valve is a differential pressure driven valve, and supplies the refrigerant to the object to be cooled through the bypass pipe by opening when the pressure difference between the upstream side and the downstream side thereof exceeds a predetermined pressure difference. A cryogenic cooling method characterized by that.

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