JP2014199745A - Cooling system for superconductive cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform continuous cooling of a superconductive cable over a long period in cooling the superconductive cable with a backup tank during shutdown of a refrigerating machine for cooling a coolant.SOLUTION: In a cooling system, a plurality of backup tanks 28a and 28b are arranged in parallel with a heat exchanger 26, and the heat exchanger 26 is arranged outside the backup tanks 28a and 28b. The cooling system is also provided with a plurality of liquid coolant circulation passages 30a and 30b which introduce individually a liquid coolant r2 stored in the backup tanks into the heat exchanger 26 and a switching mechanism which allows selectively a liquid coolant r2 from one backup tank to be circulated to the heat exchanger 26. During shutdown of a refrigeration machine 38, the pressure of the inside of one backup tank is reduced to take the evaporation latent heat from the stored liquid coolant r2 so as to cool, and a coolant r1 flowing through a coolant circulation passage 14 is cooled with the cooled liquid coolant r2.

Description

  The present invention relates to a cooling system for a superconducting cable that enables cooling of the superconducting cable to be continued for a long period of time even when a refrigerator has failed.

  When using a superconducting cable for power transmission, it is necessary to always cool the superconducting cable so that the superconducting cable loses the superconducting capability and the power transmission is not impaired. Therefore, the superconducting cable is cooled by always flowing a cooling medium such as liquid nitrogen through the superconducting cable. A refrigerator or the like is used to cool the cooling medium that flows through the superconducting cable. However, the refrigerator is expensive, complicated, and easily damaged. Therefore, instead of providing a plurality of refrigerators, a low-cost backup system is required to reliably cool the superconducting cable at all times.

  FIG. 11 shows an example of a conventional cooling system with a backup system. In FIG. 11, the cooling system 100 is connected to a cooling medium circulation path 104 for taking out a cooling medium (for example, liquid nitrogen) r1 flowing through the superconducting cable 102, cooling it, and returning it to the superconducting cable. A circulation pump 106 for circulating the cooling medium and a refrigerator 108 for cooling the cooling medium circulating in the cooling medium circulation path 104 are provided in the cooling medium circulation path 104.

  In addition, a backup tank 110 that stores liquid refrigerant (for example, liquid nitrogen) r2 is provided, and the cooling medium flowing through the cooling medium circulation path 104 and the liquid refrigerant r2 stored in the backup tank 110 are heated inside the backup tank 110. A heat exchanger 112 to be exchanged is provided. A suction path 114 is connected to the backup tank 110, and a vacuum pump 116 that sucks the internal gas of the backup tank 110 into the suction path 114 to depressurize the interior of the backup tank 110, and warms the sucked gas to 0 ° C. or higher. And a heater 118 is provided.

  The cooling medium supplied to the superconducting cable 102 is normally cooled by the refrigerator 108. However, when the refrigerator 108 stops due to a failure or the like, the vacuum pump 116 and the heater 118 are operated, and the inside of the backup tank 110 The gas is sucked, heated by the heater 118, and then released to the outside. As a result, the pressure inside the backup tank 110 is reduced, the stored liquid refrigerant is evaporated, and the cooling medium is cooled by removing latent heat of evaporation from the cooling medium. Liquid nitrogen is stored in the storage tank 120, and when the liquid nitrogen decreases in the cooling medium circulation path 104 or the backup tank 110, the liquid nitrogen is replenished via the replenishment path 122 or 124.

  Patent Documents 1 and 2 disclose a cooling means including a decompression container having the decompression mechanism as described above when a cooling medium that cools the superconducting cable is taken out and cooled.

JP 2003-307375 A JP 2004-303732 A

  Since the pressure reducing mechanism of the backup tank is operated and the liquid refrigerant is released to the outside, the amount of liquid refrigerant stored is limited, so there is a limit to the operation of the backup tank. Although it is conceivable to recover the liquid refrigerant to be released, there is a problem that the recovery equipment becomes extremely expensive. Further, if it is attempted to increase the operation duration of the backup tank, it is necessary to increase the capacity of the backup tank, resulting in high costs.

Although there is a method of cooling the cooling medium only with the backup tank, this method requires a larger volume of the backup tank and a storage tank for liquid refrigerant, which is very expensive. is there.
Alternatively, there is a method of reducing the pressure while supplying the liquid refrigerant to the backup tank. However, since the liquid refrigerant that has lost flash is sucked by the vacuum pump, the amount of consumption of the liquid refrigerant increases. Furthermore, the temperature of the liquid refrigerant in the backup tank rises and it becomes difficult to control the temperature control of the cooling medium.

  In the cooling system for a superconducting cable provided with a refrigerator and a backup tank in view of the problems of the conventional technology, the present invention cools the superconducting cable in the backup tank when the operation of the refrigerator for cooling the cooling medium is stopped. The purpose of the present invention is to allow the superconducting cable to be continuously cooled for a long period of time, and to reduce the size and cost of the backup tank.

  The present invention relates to a cooling medium circulation path that takes out a cooling medium that is cooling a superconducting cable from one end of the superconducting cable and returns it to the other end of the superconducting cable, and a cooling medium that is provided in the cooling medium circulation path and flows through the cooling medium circulation path A heat exchanger that heat-exchanges the refrigerant that is stored in the backup medium, the backup tank having a pressure reducing mechanism that stores liquid refrigerant and depressurizes the inside, and the cooling medium that flows through the cooling medium circulation path and the liquid refrigerant that is stored in the backup tank And is applied to a cooling system for superconducting cables.

  In order to achieve the above object, a plurality of backup tanks are provided in parallel to the heat exchanger, and a heat exchanger is provided outside each backup tank, and the liquid refrigerant stored in the plurality of backup tanks is stored. A plurality of liquid refrigerant circulation paths to be introduced into the heat exchanger, respectively, and a switching mechanism that allows liquid refrigerant to selectively circulate to the heat exchanger from one of the backup tanks via the liquid refrigerant circulation path And a heat exchanger is provided in the cooling medium circulation path upstream of the refrigerator.

In the above configuration, during the steady operation of the refrigerator, the liquid refrigerant circulates from at least one backup tank of the plurality of backup tanks to the heat exchanger. As a result, the liquid refrigerant circulated through the heat exchanger is cooled by the subcooled cooling medium taken out from the superconducting cable, and can maintain a liquid state.
When the operation is stopped due to a failure of the refrigerator, the pressure reducing mechanism of the backup tank that circulates the liquid refrigerant in the heat exchanger is operated. Thereby, the cooling medium can be cooled by cooling the liquid refrigerant circulating in the heat exchanger. When the liquid refrigerant stored in one backup tank is exhausted, the cooling of the superconducting cable can be continued by switching to another backup tank and circulating the liquid refrigerant from the other backup tank to the heat exchanger.

Further, by providing a plurality of backup tanks, each backup tank can be reduced in size, so that the backup tank can be transported, and handling such as filling with liquid refrigerant is facilitated.
Furthermore, by providing the heat exchanger outside the backup tank, it can be integrated into one heat exchanger, the heat exchanger configuration can be simplified and reduced in cost, and heat exchanger installation and maintenance are easy. Become. Further, by separating the heat exchanger, the configuration inside the backup tank can be simplified and reduced in cost.

Furthermore, by providing a heat exchanger in the cooling medium circulation path upstream of the refrigerator, liquid refrigerant circulated from one of the backup tanks to the heat exchanger is circulated from the superconducting cable during steady operation by the refrigerator. The subcooled cooling medium can be cooled. As a result, the liquid refrigerant stored in the backup tank can be held in a cooled state in liquid form.
Furthermore, since the liquid refrigerant in the backup tank is always cooled, it is not necessary to replenish the liquid refrigerant during steady operation, and unattended continuous operation is possible.

The inventors of the present invention considered a configuration different from the present invention before reaching the present invention. The configuration is such that a plurality of backup tanks are provided and a heat exchanger is provided inside each backup tank. Thus, when the liquid refrigerant in one backup tank is consumed, the cooling medium is cooled in another backup tank, so that cooling of the cooling medium can be continued and each backup tank can be downsized.
Furthermore, by providing a plurality of backup tanks, the size of each backup tank can be reduced, so that the backup tank can be transported, and handling such as filling with liquid refrigerant is facilitated.

  However, the present inventors have reached the present invention for the purpose of further reducing the configuration of the backup tank and the heat exchanger and reducing the cost.

As one aspect of the present invention, when a temperature sensor provided in a cooling medium circulation path downstream from the refrigerator and a detected value of the temperature sensor are input and the detected value exceeds a threshold value, a pressure reducing mechanism for the backup tank is provided. And a control device to be operated.
As a result, it is possible to quickly detect an operation stop due to a failure of the refrigerator, and to start the cooling operation using the backup tank without delay. Therefore, there is no possibility of interrupting the cooling of the superconducting cable.

  As one aspect of the present invention, in addition to the above configuration, an alarm device is further provided that issues an alarm when the detected value of the temperature sensor exceeds a threshold value. The detected value of the temperature sensor is input, and the detected value exceeds the threshold value. The alarm device can be activated by the control device. As a result, it is possible to promptly notify the manager of the cooling system of the abnormality of the refrigerator.

  As one aspect of the present invention, the backup tank and the heat exchanger are arranged at the same height level or higher, and the liquid refrigerant is naturally circulated in the liquid refrigerant circulation path. That is, the backup tank is arranged at the same height level or higher with respect to the heat exchanger. In this case, the case where the level of the liquid refrigerant formed in the backup tank is equal to or higher than the heat exchanger is included. This eliminates the need for power for circulating the liquid refrigerant, thus simplifying and reducing the cost of the liquid refrigerant circulation mechanism.

As one embodiment of the present invention, a plurality of backup tanks can be a portable tank that can be detached from the installation surface.
Thereby, when the operation of the refrigerator is stopped, the pressure reducing mechanism of one backup tank in which the liquid refrigerant is circulated to the heat exchanger is operated, and the backup tank depleted in the liquid refrigerant is transported to the liquid refrigerant supply place, After the backup tank is filled with liquid refrigerant at this supply location, it can be transported to the installation location. Therefore, even when the backup tank is provided in a place where there is no space where the tank lorry for transporting the liquid refrigerant can be stopped, the liquid refrigerant can be supplied to the backup tank.

  According to the present invention, the cooling operation of the superconducting cable can be continued for a long time while replenishing the liquid refrigerant by providing a plurality of backup tanks in the cooling medium circulation path and switching and using these backup tanks. Further, since each backup tank can be reduced in size, it is possible to reduce the construction cost and the like, and to make it possible to refill the backup tank with liquid refrigerant.

It is a distribution diagram at the time of steady operation of the cooling system concerning a 1st embodiment of the present invention. It is an enlarged view of a part of structure of the said cooling system. (A) And (B) is a figure which shows the structural example of the heat exchange pipe | tube applicable to the said cooling system, respectively. It is a systematic diagram at the time of the refrigerator failure of the said cooling system. It is a block diagram of the control system of the cooling system. It is a schematic diagram which shows temperature control of the liquid refrigerant of the said cooling system. It is a systematic diagram at the time of steady operation of the cooling system concerning a 2nd embodiment of the present invention. It is a systematic diagram at the time of the refrigerator failure of the cooling system which concerns on the said 2nd Embodiment. It is a systematic diagram at the time of the refrigerator failure of the cooling system which concerns on the said 2nd Embodiment. It is a systematic diagram of a cooling system according to an intermediate technique (not disclosed) before reaching the present invention. It is a systematic diagram of the conventional cooling system for superconducting cables.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

(Embodiment 1)
1st Embodiment of this invention is described based on FIGS. In FIG. 1, in the cooling system 10 </ b> A of the present embodiment, a cooling medium circulation path 14 is connected to the outlet portion 12 a and the inlet portion 12 b of the high temperature superconducting cable 12. Liquid nitrogen is used as the cooling medium r1. The cooling medium r1 is temporarily stored in the reservoir tank 16 from the cooling medium circulation path 14, and then supplied to the heat exchanger 26 by the circulation mechanism 18. A refrigerator 38 is provided on the downstream side of the heat exchanger 26. The circulation mechanism 18 is provided with open / close valves 20a and 20b, circulation pumps 22a and 22b, and flow rate adjustment valves 24a and 24b in two circulation paths 14a and 14b, respectively.

  The reservoir tank 16 has a role of performing pressure adjustment to keep the pressure of the cooling medium r1 flowing in the superconducting cable 12 at, for example, 0.2 MPa or more in order to prevent dielectric breakdown due to charge concentration due to bubbles in the superconducting cable 12. When the temperature of the cooling medium r1 rises in the superconducting cable 12, the volume of the cooling medium r1 also changes, so that the volume change is absorbed. Further, for redundancy of the circulation pump, two circulation paths 14a and 14b are arranged in parallel, and the circulation pumps 22a and 22b are provided in the respective circulation paths. Normally, the circulation pumps 22a and 22b are alternately operated. When one unit has insufficient head, the circulation pumps 22a and 22b are arranged in series and operated simultaneously, and when the flow rate is insufficient, the operation is performed in parallel arrangement. Let

  The cooling system 10A includes two backup tanks 28a and 28b. In the backup tanks 28a and 28b, liquid refrigerant r2 made of liquid nitrogen is stored. The liquid refrigerant r2 stored in the backup tanks 28a and 28b is circulated to the heat exchanger 26 via the liquid refrigerant circulation paths 30a and 30b provided between the respective backup tanks and the heat exchanger 26. In the heat exchanger 26, heat is exchanged between the cooling medium r1 and the liquid refrigerant r2. The cooling medium r1 heat-exchanged by the heat exchanger 26 is cooled by the refrigerator 38 and then returned to the inlet 12b of the superconducting cable 12.

  The backup tanks 28a and 28b are provided with suction paths 32a and 32b for sucking the gas in the backup tank. The suction paths 32a and 32b merge into one, and a heater 34 and a vacuum pump 36 for heating the vapor of the liquid refrigerant sucked from the backup tank are provided at the merge portion. In addition, a control device 40 and an alarm device 44 are provided in a monitoring room 42 that monitors the cooling system 10A. The cooling medium circulation path 14 near the inlet 12 b is provided with a temperature sensor 46 that detects the temperature of the cooling medium r <b> 1 flowing through the cooling medium circulation path 14, and the detected value of the temperature sensor 46 is sent to the control device 40.

  The control device 40 controls the operations of the circulation pumps 22a and 22b, and controls the operations of the heater 34, the vacuum pump 36, the refrigerator 38, and the alarm device 44 based on the detection value of the temperature sensor 46, and Controls the operation of each valve. Switching valves 48a and 50a are provided in the liquid refrigerant circulation path 30a, switching valves 48b and 50b are provided in the liquid refrigerant circulation path 30b, and a switching valve 52 is provided in the cooling medium circulation path 14 downstream of the heat exchanger 26. Switching valves 54 and 56 are provided on the branch path 14c that connects the cooling medium circulation path 14 and the refrigerator 38 with the switching valve 52 interposed therebetween. The suction path 32a is provided with a pressure control valve 58a, and the suction path 32b is provided with a pressure control valve 58b.

FIG. 1 shows a steady operation in which the cooling medium r1 is cooled by the refrigerator 38. In the figure, the white valve indicates an open state, and the black valve indicates a closed state. That is, the switching valves 48b, 50b, 54, 56 and the pressure control valve 58b are opened, and the switching valves 48a, 50a, 52 and the pressure control valve 58a are closed.
The cooling medium r1 flowing out from the outlet 12a to the cooling medium circulation path 14 is once stored in the reservoir tank 16, and then introduced into the heat exchanger 26 by the circulation mechanism 18. The cooling medium r1 is introduced into the heat exchanger 26 from the backup tank 28b via the liquid refrigerant circulation path 30b, and heat is exchanged between the cooling medium r1 and the liquid refrigerant r2. In the heat exchanger 26, the liquid refrigerant r2 is cooled along the saturated vapor pressure line by the subcooled cooling medium r1, thereby maintaining the liquefied state.

  FIG. 2 is an enlarged view of the heat exchanger 26 and the backup tank 28b. In FIG. 2, a heat exchange pipe 60 connected to the cooling medium circulation path 14 is provided inside the heat exchanger 26. As shown in FIG. 2, the heat exchanger 26 is arranged at the same height level as the backup tank 28b. The liquid level of the liquid refrigerant r2 in the backup tank 28b is located above the heat exchanger 26. Therefore, the forward path 30b1 for sending the liquid refrigerant r2 from the backup tank 28b to the heat exchanger 26 is connected to the backup tank 28b at a height above the heat exchanger 26, and descends and is connected to the upper part of the heat exchanger 26. ing. The return path 30b2 for returning the liquid refrigerant r2 after the heat exchange from the heat exchanger 26 to the backup tank 28b is arranged substantially horizontally in the lower part of the heat exchanger 26 and the backup tank 28b, and is connected to both. ing.

  With this configuration, by setting the inside of the backup tank 28b and the inside of the heat exchanger 26 to the same pressure, the liquid refrigerant r2 can flow into the heat exchanger 26 by gravity from the backup tank 28b through the forward path 30b1. Thereby, the flow of the liquid refrigerant r2 flowing into the heat exchanger 26 from the backup tank 28b and returning to the backup tank 28b through the return path 30b2 is naturally circulated, and the liquid refrigerant r2 can be automatically supplied to the heat exchanger 26. The backup tank 28a has the same configuration as the heat exchanger 26. The heat exchange tube 60 is a coil-type heat exchange tube, and is easy to manufacture and has an advantage that the cost can be reduced.

  FIG. 3 shows a configuration of a heat exchange tube that can replace the heat exchange tube 60. FIG. 3A shows a meandering heat exchange pipe 62, which is easy to manufacture and can be reduced in cost, like the heat exchange pipe 60. FIG. The heat exchange pipe 64 shown in FIG. 3B is a linear heat exchange pipe, but a large number of fins 66 project radially from the outer peripheral surface. Since the heat exchange pipe 64 can increase the heat transfer area, the amount of heat exchange can be increased.

The cooling medium r1 exiting the heat exchanger 26 is cooled by the refrigerator 38 and then returned to the high temperature superconducting cable 12 from the inlet 12b.
When the detected value of the temperature sensor 46 exceeds the threshold value, the controller 40 determines that an abnormality has occurred in the refrigerator 38, stops the refrigerator 38, and the controller 40 shows the open / close state of each valve in FIG. State shown. That is, the switching valve 52 is opened and the switching valves 54 and 56 are closed. At the same time, the alarm device 44 is operated by the control device 40 and the heater 34 and the vacuum pump 36 are operated. By the operation of the vacuum pump 36, the gas inside the backup tank 28a is sucked into the suction path 32b. The gas sucked into the suction path 32b is heated to 0 ° C. or higher by the heater 34 and then released to the atmosphere. The refrigerator 38 in which the abnormality has occurred is heated for maintenance, and the failed device is replaced over a period of about 2 to 3 days.

  As shown in FIG. 5, the backup tanks 28a and 28b have a temperature sensor 70 for detecting the temperature of the stored liquid refrigerant r2, and a pressure sensor 72 for detecting the saturated vapor pressure of the liquid refrigerant r2 in the backup tank. Is provided. The detection values of these sensors are sent to the control device 40, and the control device 40 controls the saturated vapor pressure of the backup tank 28a or 28b by controlling the opening degree of the pressure control valve 58a or 58b based on these detection values. Then, the temperature of the liquid refrigerant r2 stored in the backup tank is controlled. That is, the temperature of the liquid refrigerant r2 in the backup tank is controlled by controlling the opening degree of the pressure control valve 58a or 58b so that the temperature of the cooling medium r1 at the outlet of the heat exchanger 26 becomes a target value (for example, 70K). To control.

At that time, as shown in FIG. 6, first, the control device 40 controls the pressure control valve 58a or 58b so that the temperature of the liquid refrigerant r2 in the backup tank falls within a certain range (T _{1 to} T ₂ ). . Next, the pressure control valve is controlled so that the saturated vapor pressure in the backup tank falls within a certain range (P _{1 to} P ₂ ). This is because the amount of liquid refrigerant r2 in the backup tank is large and the temperature change of the liquid refrigerant r2 is slow, so that temperature control is speeded up by performing two-stage control.

For example, in the range of temperature of the liquid refrigerant r2 in the backup tank _(T 1 _{~T 2),} the temperature as a control parameter to control the opening degree of the pressure control valve 58a or 58b, the liquid refrigerant r2 in the backup tank When the saturated vapor pressure is in the range of (P _{1 to} P ₂ ), the pressure control valve is controlled using the saturated vapor pressure as a control parameter.
As a result, the temperature of the liquid refrigerant r2 in the backup tank can be quickly controlled.

By this operation, the inside of the backup tank 28b is decompressed, and the liquid refrigerant r2 evaporates. At this time, since the latent heat of vaporization is taken from the remaining liquid refrigerant r2, the remaining liquid refrigerant r2 can be cooled. Thus, by circulating the cooled liquid refrigerant r2 to the heat exchanger 26, cooling of the cooling medium r1 can be continued. When the liquid refrigerant r2 stored in the backup tank 28b is exhausted by discharging the evaporated liquid refrigerant r2 to the outside from the backup tank 28b, the control valve 40 causes the switching valves 48a, 50a, 58a, 48b, 50b, and The pressure control valve 58b is operated to close the liquid refrigerant circulation path 30b and the suction path 32b and open the liquid refrigerant circulation path 30a and the suction path 32a.
Thus, the liquid refrigerant r2 stored in the backup tank 28a can be circulated to the heat exchanger 26 via the liquid refrigerant circulation path 30a.

  When the liquid refrigerant r2 stored in the backup tank 28a or 28b is exhausted, the liquid refrigerant r2 is replenished from the tank truck that transports the liquid refrigerant r2.

According to the present embodiment, since the cooling medium r1 can be cooled for a long time even when the refrigerator 38 is stopped due to a failure or the like, the cooling of the superconducting cable 12 can be continued. In addition, by providing two backup tanks, the size of each backup tank can be reduced.
Furthermore, by providing the heat exchanger 26 outside the backup tanks 28a and 28b, the heat exchanger 26 can be integrated into one heat exchanger, the configuration of the heat exchanger 26 can be simplified and reduced in cost, and the heat exchanger 26 Easy installation and maintenance. Further, by separating the heat exchanger 26, the configuration inside the backup tank can be simplified and reduced in cost.

Further, by providing the heat exchanger 26 in the cooling medium circulation path 14 on the upstream side of the refrigerator 38, the heat exchanger 26 is circulated from one of the backup tanks 28 a and 28 b to the heat exchanger 26 during steady operation by the refrigerator 38. The liquid refrigerant r2 can be cooled by the subcooled cooling medium r1 circulated from the superconducting cable 12. As a result, the liquid refrigerant r2 stored in the backup tanks 28a and 28b can be held in a cooled state.
Furthermore, since the liquid refrigerant r2 in the backup tanks 28a and 28b is always cooled, it is not necessary to supply the liquid refrigerant r2 during steady operation, and unattended continuous operation is possible.

Further, by providing the temperature sensor 46 and the alarm device 44, it is possible to quickly detect an operation stop due to a failure of the refrigerator 38 or the like, and it is possible to start the cooling operation using the backup tank without delay. Therefore, there is no possibility that the cooling of the superconducting cable 12 is interrupted.
Moreover, by arranging the backup tanks 28a and 28b and the heat exchanger 26 at the same height level, the circulation of the liquid refrigerant r2 between them can be naturally circulated. Thereby, power for circulating the liquid refrigerant r2 becomes unnecessary, and the circulation mechanism of the liquid refrigerant r2 can be simplified and reduced in cost.

(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to FIGS. The cooling system 10B of the present embodiment is configured by a portable tank in which the backup tanks 28a and 28b are detachable from the installation surface. Other configurations are the same as those of the first embodiment. FIG. 7 shows the time when the refrigerator 38 is in steady operation. At this time, only the backup tank 28a is installed, and the liquid refrigerant r2 is stored therein. FIG. 8 shows the time when the operation of the refrigerator 38 is stopped and the cooling operation by the backup tank 28a is performed. In the state of FIG. 8, the backup tank 28b is transported from the installation surface, and the liquid refrigerant r2 is supplied at a place where the liquid refrigerant r2 can be supplied.

In FIG. 9, the backup tank 28b in which the liquid refrigerant r2 is stored is installed at the installation position. On the other hand, since the liquid refrigerant r2 stored in the backup tank 28a has been consumed, the backup tank 28a is detached from the installation surface and is transported to the supply location of the liquid refrigerant r2. The backup tanks 28a and 28b are alternately filled with the liquid refrigerant r2 until the maintenance of the refrigerator 38 is completed.
According to the present embodiment, in addition to the operational effects obtained in the first embodiment, the backup tank 28a can be used even when the cooling system 10B is located in a small space such as a city or in the mountains where the tank lorry for transporting the liquid refrigerant r2 cannot be stopped. And 28b can be replenished with the liquid refrigerant r2.

(Comparative example)
Next, as described above, a cooling system as an intermediate technique (undisclosed) considered by the present inventors before reaching the present invention will be described with reference to FIG. In the cooling system 10C of this comparative example, heat exchangers 26a and 26b are arranged inside backup tanks 28a and 28b, respectively. The heat exchangers 26 a and 26 b are connected in parallel to the cooling medium circulation path 14. That is, the heat exchanger 26a is connected to the cooling medium circulation path 14 via the branch paths 80a and 82a, and the heat exchanger 26b is connected to the cooling medium circulation path 14 via the branch paths 80b and 82b.

A switching valve 84a is provided in the branch path 80a, and a switching valve 86a is provided in the branch path 82a. A switching valve 84b is provided in the branch path 80b, and a switching valve 86b is provided in the branch path 82b. The operation of the switching valves 84a, 86a, 84b and 84b is controlled by the control device 40.
In this comparative example, by controlling the operation of the switching valve by the control device 40, the cooling medium r1 flowing through the cooling medium circulation path 14 can be selectively introduced into the heat exchanger 26a or 26b.
Other configurations are the same as those in the first embodiment and the second embodiment, and the same components and the same parts are denoted by the same reference numerals.

FIG. 10 shows the steady state operation of the refrigerator 38. When the refrigerator 38 stops due to a failure or the like, the switching valves 52, 54, and 56 are switched by the control device 40, and the operation is switched to the operation of cooling the cooling medium r1 by the backup tank 28a. When the liquid refrigerant r2 in the backup tank 28a is exhausted, the control device 40 switches the switching mechanism such as the pressure control valves 58a and 58b and the switching valves 84a, 86a, 84b and 86b to switch to the cooling operation by the backup tank 28b.

  According to this comparative example, even when the refrigerator 38 is stopped due to a failure or the like, the cooling medium r1 can be cooled over a long period of time by switching the cooling medium r1 to the heat exchanger 26a or 26b, and the superconducting cable 12 can be cooled. Cooling can be continued and individual backup tanks can be downsized. Further, by providing the temperature sensor 46 and the alarm device 44, it is possible to quickly detect an operation stop due to a failure of the refrigerator 38 or the like, and it is possible to start the cooling operation using the backup tank without delay. Therefore, there is no possibility that the cooling of the superconducting cable 12 is interrupted.

  Furthermore, by arranging the backup tanks 28a and 28b and the heat exchanger 26 at the same height level, the circulation of the liquid refrigerant r2 between them can be naturally circulated, whereby the liquid refrigerant r2 is circulated. Power is not required, and the circulation mechanism of the liquid refrigerant r2 can be simplified and reduced in cost. Furthermore, by enabling the backup tanks 28a and 28b to be transported, even when the cooling system 10C is located in a place where the tank lorry for transporting the cooling medium r1 cannot be stopped, the cooling medium r1 is supplied to the backup tanks 28a and 28b. Effects such as being able to be replenished can be obtained.

  As described above, the present inventors have reached the present invention for the purpose of further reducing the configuration of the backup tank and the heat exchanger and reducing the cost.

  According to the present invention, the cooling of the superconducting cable can be continued for a long time even when the operation of the cooling medium is stopped, and the backup tank can be reduced in size and cost.

10A, 10B, 10C, 100 Cooling system 12, 102 Superconducting cable 12a Outlet part 12b Inlet part 14, 104 Cooling medium circulation path 14c Branch path 16 Reservoir tank 18 Circulation mechanism 20a, 20b On-off valve 22a, 22b Circulation pump 24a, 24b Flow rate Regulating valve 26, 26a, 26b, 112 Heat exchanger 28a, 28b, 110 Backup tank 30a, 30b Liquid refrigerant circulation path 30b1 Outward path 30b2 Return path 32a, 32b, 114 Suction path 34, 118 Heater 36, 116 Vacuum pump 38, 108 Refrigerator 40 Control device 42 Monitoring room 44 Alarm 46, 70 Temperature sensor 48a, 48b, 50a, 50b, 52, 54, 56, 84a, 84b, 86a, 86b Switching valve 58a, 58b Pressure control valve 60, 62, 64 Heat exchange tube 66 Fin 72 Pressure sensor 80a, 80b, 82a, 82b Branch path 106 Circulating pump 120 Storage tank 122, 124 Supply path r1 Cooling medium r2 Liquid refrigerant

Claims (5)

A cooling medium circulation path for taking out the cooling medium cooling the superconducting cable from one end of the superconducting cable and returning it to the other end of the superconducting cable;
A refrigerator provided in the cooling medium circulation path for cooling the cooling medium flowing through the cooling medium circulation path;
A backup tank having a decompression mechanism in which liquid refrigerant is stored and decompresses the interior;
A cooling system for a superconducting cable comprising a heat exchanger that exchanges heat between the cooling medium flowing through the cooling medium circulation path and the liquid refrigerant stored in the backup tank,
A plurality of the backup tanks are provided in parallel to the heat exchanger, and the heat exchanger is provided outside the plurality of backup tanks,
A plurality of liquid refrigerant circulation paths that respectively introduce the liquid refrigerant stored in the plurality of backup tanks into the heat exchanger;
A switching mechanism that allows the liquid refrigerant to circulate to the heat exchanger selectively from one backup tank among the plurality of backup tanks via the liquid refrigerant circulation path;
The cooling system for a superconducting cable, wherein the heat exchanger is provided in the cooling medium circulation path upstream of the refrigerator. A temperature sensor provided in the cooling medium circulation path downstream from the refrigerator;
2. The apparatus according to claim 1, further comprising: a controller for operating the pressure reducing mechanism of the backup tank and the alarm when the detected value of the temperature sensor is input and the detected value exceeds the threshold value. The cooling system for superconducting cables described in 1. The backup tank and the heat exchanger are arranged at the same height level or more,
The cooling system for a superconducting cable according to claim 1, wherein the liquid refrigerant can be naturally circulated from the backup tank to the heat exchanger through a liquid refrigerant circulation path. An alarm device that issues an alarm when a detected value of the temperature sensor exceeds a threshold value;
3. The cooling for a superconducting cable according to claim 2, wherein when the detection value of the temperature sensor is input and the detection value exceeds the threshold value, the control device activates the alarm device. system.   The cooling system for a superconducting cable according to claim 1, wherein the plurality of backup tanks are configured as portable tanks that are removable from an installation surface.

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