JP2017089953A - Cooling system of superconductive cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling system of a superconductive cable capable of cooling the superconductive cable to a desired temperature without an excessive burden to a chiller even when the temperature of the superconductive cable is suddenly increased.SOLUTION: A cooling system of a superconductive cable comprises: a reservoir for storing liquid gas; a circulation pump for circulating the liquid gas stored in the reservoir; a circulation loop having a cooling part for cooling the circulating liquid gas; and a pressure adjustment part for controlling the pressure of evaporation gas in the reservoir constant, so that the superconductive cable is cooled by circulating the liquid gas in a sub-cooling state. A return pipe for returning the liquid gas which has cooled the superconductive cable to the reservoir and a delivery pipe for sending out the liquid gas which has been cooled within the reservoir from the reservoir are connected to the reservoir; and a convection flow prevention plate is provided within the reservoir at a position upper than a connection position in which the return pipe and the delivery pipe are respectively connected to the reservoir, the convection flow prevention plate being disposed in the stored liquid gas and extending in a width direction of the reservoir.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a superconducting cable cooling system that cools a superconducting cable while circulating a liquefied gas in a circulation loop in a subcooled state.

  There is a phenomenon called superconductivity in which the electrical resistance suddenly becomes zero when a material such as a specific metal, alloy, or compound is cooled to a very low temperature. Superconducting cables that apply superconducting technology to power transmission cables use superconducting wires as current-carrying conductors and can flow large currents with a small cross-sectional area. It has gained attention because of its advantages such as improved efficiency.

  The superconducting cable is cooled by circulating a liquefied gas such as liquid nitrogen in a circulation loop. Here, when the circulating liquefied gas is vaporized in the insulator constituting the superconducting cable, it becomes a starting point of dielectric breakdown. For this reason, in this kind of cooling system, it is necessary to circulate, maintaining liquefied gas in the state (subcool state) lower than saturation temperature. In general, the minimum pressure of the liquefied gas circulating in the cooling system is about 0.2 MPaG or more, which is a pressure at which partial discharge does not occur in the withstand voltage test.

  Cooling of the liquefied gas which circulates is performed by the cooler provided on the circulation loop for the liquefied gas sent out from the storage tank which stores liquefied gas, for example (refer to patent documents 1). The cooling system for a superconducting cable described in Patent Document 1 adjusts the liquefied gas that has cooled the superconducting cable to a constant pressure in the storage tank, and then cools the liquefied gas that has been sent from the storage tank and pressure-adjusted with a cooler. The superconducting cable is cooled with the cooled liquefied gas.

JP 2014-126283 A

  In the cooling system for the superconducting cable described in Patent Document 1, the liquefied gas whose temperature has been increased by cooling the superconducting cable is temporarily stored in a storage tank. Since there is a temperature difference with other liquefied gas stored in the tank, convection occurs in the storage tank in which the liquefied gas is directed in the vertical direction. When this convection occurs, a liquefied gas having a relatively high temperature is stored in the upper part of the storage tank, and a liquefied gas lower than the temperature of the liquefied gas staying in the upper part is stored in the lower part of the storage tank. Therefore, the liquefied gas whose temperature has been increased by cooling the superconducting cable cannot be cooled in the storage tank. For this reason, when the temperature of the superconducting cable suddenly rises and a large load fluctuation is applied to the cooler, if the load exceeds the cooling capacity of the cooler, the cooler may cool the superconducting cable to a desired temperature. There is a risk that it will not be possible.

  At least one embodiment of the present invention is an invention made on the basis of the state of the art as described above, and the object thereof is to supply a cooler even if the temperature of the superconducting cable is rapidly increased. It is an object of the present invention to provide a cooling system for a superconducting cable capable of cooling the superconducting cable to a desired temperature without causing an excessive load.

(1) A cooling system for a superconducting cable according to at least one embodiment of the present invention includes:
A storage tank for storing the liquefied gas, a circulation pump for circulating the liquefied gas stored in the storage tank, a circulation loop having a cooling unit for cooling the liquefied gas to be circulated, and a vaporization gas in the storage tank A superconducting cable cooling system comprising: a pressure adjusting unit configured to make the pressure constant; and cooling the superconducting cable by circulating the liquefied gas in a subcooled state,
The storage tank is connected to a return pipe that returns the liquefied gas that has cooled the superconducting cable into the storage tank, and a delivery pipe that delivers the liquefied gas cooled in the storage tank from the storage tank,
In the storage tank, each of the return pipe and the delivery pipe is positioned above the connection position connected to the storage tank and is stored in the liquefied gas to be stored in the width direction of the storage tank. It is comprised so that the convection prevention board extended may be provided.

  In the superconducting cable cooling system described in (1) above, the storage tank is supplied with a return pipe that returns the liquefied gas that has cooled the superconducting cable into the storage tank, and the liquefied gas cooled in the storage tank is sent from the storage tank. Connected to the delivery pipe. And in the storage tank, each of the return pipe and the delivery pipe is located above the connection position connected to the storage tank and is disposed in the stored liquefied gas and extends in the width direction of the storage tank. Is provided. For this reason, since the temperature of the liquefied gas flowing into the storage tank from the return pipe is relatively high, the liquefied gas stored in the storage tank rises, but the movement of the liquefied gas rising by the convection prevention plate is regulated. . In addition, the liquefied gas stored in the storage tank and having a relatively low temperature of the liquefied gas stored above the convection prevention plate tends to flow downward, but this flow is caused by the convection prevention plate. Be regulated. For this reason, the convection which moves to the up-down direction of liquefied gas is controlled by the convection prevention board. Therefore, the liquefied gas flowing into the storage tank from the return pipe is cooled while mixing and exchanging heat with the liquefied gas stored below the convection prevention plate, flows toward the delivery pipe, and is sent out from the delivery pipe. . For this reason, the liquefied gas flowing into the storage tank can be cooled by heat exchange with the liquefied gas stored in the storage tank. For this reason, the load which is provided in the ring loop and cools the liquefied gas by the cooling unit can be reduced. Therefore, when the temperature of the superconducting cable suddenly rises and the temperature of the liquefied gas that cools the superconducting cable rises, the liquefied gas that has risen in temperature can be cooled by the liquefied gas and the cooler in the storage tank. Compared with the case where the liquefied gas is cooled only by the cooler, the load on the cooler can be reduced. Therefore, even if the temperature of the superconducting cable suddenly increases, a superconducting cable cooling system capable of cooling the superconducting cable to a desired temperature can be realized without causing an excessive load on the cooler.

(2) In some embodiments, in the cooling system for a superconducting cable according to (1) above,
The cooling unit is configured to be disposed at a position for cooling the liquefied gas stored below the convection prevention plate.

  According to the superconducting cable cooling system described in (2) above, the cooling section is disposed at a position for cooling the liquefied gas stored below the convection prevention plate. For this reason, since the liquefied gas stored below the convection prevention plate is cooled by the cooling unit, the liquefied gas flowing into the liquefied gas stored below the convection prevention plate exchanges heat with the stored liquefied gas. And is also cooled by heat exchange with the cooler. For this reason, even if the temperature of the superconducting cable suddenly rises, the liquefied gas for cooling the superconducting cable can be reliably cooled without causing an excessive load on the cooler.

(3) In some embodiments, in the cooling system for a superconducting cable according to (2) above,
The position of the cooling unit is configured to cool a liquefied gas that is close to the convection preventing plate out of the liquefied gas stored below the convection preventing plate.

  According to the superconducting cable cooling system described in (3) above, the position of the cooling unit is a position for cooling the liquefied gas adjacent to the convection prevention plate among the liquefied gas stored below the convection prevention plate. When the liquefied gas whose temperature has been increased by cooling the superconducting cable flows into the liquefied gas stored below the convection prevention plate, the liquefied gas whose temperature has been increased generally decreases in density and moves upward. For this reason, when the liquefied gas whose temperature has risen flows into the storage tank below the convection prevention plate, the liquefied gas has a higher temperature than the stored liquefied gas. Move to. For this reason, the liquefied gas whose temperature has risen is effectively cooled by setting the position of the cooling part to a position for cooling the liquefied gas in the vicinity of the convection preventing plate among the liquefied gases stored below the convection preventing plate. can do.

(4) In some embodiments, in the cooling system for a superconducting cable according to (3) above,
A guide channel for guiding the liquefied gas discharged from the return pipe to the delivery pipe is formed in the storage tank below the convection prevention plate.

  According to the cooling system for a superconducting cable described in (4) above, a guide channel for guiding the liquefied gas discharged from the return pipe to the delivery pipe is formed in the storage tank below the convection prevention plate. ing. When the liquefied gas discharged from the return pipe flows through the guide flow path, there is no possibility that the liquefied gas stays in the storage tank. For this reason, the liquefied gas is cooled by reliably exchanging heat with the liquefied gas stored in the storage tank below the convection prevention plate during the flow of the guide channel. For this reason, liquefied gas can be cooled effectively.

(5) In some embodiments, in the cooling system for a superconducting cable according to (4),
The guide channel has a plurality of floor plates extending in the width direction of the storage tank and spaced apart in the vertical direction in the storage tank.

  According to the cooling system for a superconducting cable according to the above (5), the guide channel extends in the storage tank in the width direction and is arranged at intervals in the vertical direction in the storage tank. It has a floor plate. For this reason, a guide channel can be formed between the floor plates adjacent in the vertical direction. Therefore, it is possible to realize a storage tank having a guide channel with a simple configuration.

(6) In some embodiments, in the cooling system for a superconducting cable according to (5) above,
The return pipe is connected to the storage tank below the convection prevention plate,
The delivery pipe is configured to be connected to the storage tank below the convection prevention plate and above the return pipe.

  According to the cooling system for a superconducting cable described in (6) above, the return pipe is connected to the storage tank below the convection prevention plate, and the delivery pipe is below the convection prevention plate and is lower than the return pipe. It is connected to the upper storage tank. The liquefied gas whose temperature has increased generally has a lower density and moves upward. For this reason, when the liquefied gas whose temperature has risen flows into the liquefied gas stored below the convection prevention plate, the liquefied gas has a higher temperature than the stored liquefied gas. Moves upward. For this reason, by connecting the delivery pipe to a storage tank below the convection prevention plate and above the return pipe, the superconducting cable is cooled and the liquefied gas whose temperature has risen is reliably introduced into the delivery pipe. Can do.

(7) In some embodiments, in the cooling system for a superconducting cable according to (2) above,
The cooling unit is a cooling device disposed on an outer surface of the side wall of the storage tank that surrounds the liquid gas that is close to the convection prevention plate among the liquid gas stored in the storage tank below the convection prevention plate. It is configured to be a heat exchanger.

  According to the cooling system for a superconducting cable described in (7) above, the cooling unit includes a storage tank that surrounds the liquid gas adjacent to the convection prevention plate among the liquid gases stored in the storage tank below the convection prevention plate. It is the heat exchanger of the cooling device arrange | positioned at the outer surface of the side wall. The liquefied gas stored below the convection prevention plate and close to the convection prevention plate is cooled by heat exchange with the heat exchanger via the side wall of the storage tank. For this reason, it is possible to effectively cool the liquefied gas whose temperature rises in the vicinity of the convection prevention plate among the liquefied gas stored below the convection prevention plate.

(8) In some embodiments, in the cooling system for a superconducting cable according to (7) above,
The said storage tank is accommodated in an outer side tank, and the space between the said storage tank and the said outer side tank comprises the vacuum heat insulation layer.

  According to the superconducting cable cooling system described in (8) above, the storage tank is accommodated in the outer tank, and the space between the storage tank and the outer tank constitutes a vacuum heat insulating layer. Since the space between the storage tank and the outer tank forms a vacuum insulation layer, it eliminates the ingress of heat from the outside and the leakage of heat to the outside during the heat exchange between the heat exchanger and the liquefied gas. be able to.

(9) In some embodiments, in the cooling system for a superconducting cable according to (7) or (8) above,
The volume below the convection prevention plate in the storage tank is such that the liquefied gas delivered from the delivery pipe is cooled to a predetermined temperature in a subcooled state, and the cooling capacity of the heat exchanger of the cooling unit, It is configured to be set based on the heat storage amount of the liquefied gas stored in the storage tank below the convection prevention plate.

  According to the cooling system for a superconducting cable described in (9) above, the volume below the convection prevention plate in the storage tank is such that the liquefied gas delivered from the delivery pipe is cooled to a predetermined temperature in the subcooled state. It is set based on the cooling capacity of the heat exchanger of the cooling unit and the heat storage amount of the liquefied gas stored in the storage tank below the convection prevention plate. For this reason, when the temperature of the superconducting cable suddenly rises, the liquefied gas whose temperature has risen by cooling the superconducting cable is reliably cooled by cooling with a heat exchanger and heat exchange with the stored liquefied gas. can do. For this reason, even if the temperature of the superconducting cable suddenly rises, a cooling system for the superconducting cable that can cool the superconducting cable to a desired temperature without causing an excessive load on the cooler can be realized.

(10) In some embodiments, in the cooling system for a superconducting cable according to (1) above,
The cooling unit includes a lead-out pipe that leads out the liquid gas stored in the storage tank below the convection prevention plate, a cooling device that cools the liquid gas led out from the lead-out pipe, and the cooling device. A return pipe that returns the cooled liquefied gas into the storage tank below the convection prevention plate, and a lead-out pump that is provided in the lead-out pipe and sends the liquid gas in the storage tank to the lead-out pipe. Configured as follows.

  According to the superconducting cable cooling system described in (10) above, the liquefied gas W led out by the lead-out pump through the lead-out pipe is cooled by the cooling device and returned to the storage tank through the lead-in pipe. In this way, a circulation loop is formed by the outlet pipe and the outlet pipe, and the liquefied gas is circulated through the circulation loop by the outlet pump. For this reason, the liquefied gas stored in the storage tank below the convection prevention plate of the storage tank is forcibly cooled by the circulation loop. For this reason, the liquefied gas which cools a superconducting cable, raises temperature, and is returned in a storage tank is mixed with the liquefied gas forcedly cooled by the circulation loop, and is cooled. Therefore, even if the temperature of the superconducting cable rapidly increases, the superconducting cable can be cooled to a desired temperature without causing an excessive load on the cooling device.

(11) In some embodiments, in the superconducting cable cooling system according to any one of (1) to (10) above,
A space for storing the gas phase is formed above the liquefied gas stored in the storage tank.

  According to the superconducting cable cooling system described in (11) above, the space for storing the gas phase is formed above the liquefied gas stored in the storage tank. For this reason, even if the temperature of liquefied gas changes and a volume increases / decreases, the increase / decrease in the volume of liquefied gas can be absorbed by the space part in a storage tank. For this reason, it is possible to prevent inconvenience (for example, damage to the circulation path and the storage tank) due to an increase in pressure in the superconducting cable and the circulation loop.

(12) In some embodiments, in the cooling system for a superconducting cable according to (1),
The pressure adjusting unit is provided in a bypass line branched from the circulation loop, and heat exchanger for vaporizing the liquefied gas introduced through the bypass line; and the vaporized gas vaporized by the heat exchanger in the storage tank A flow rate adjusting valve that can be supplied to the space above the liquefied gas stored therein.

  According to the cooling system for a superconducting cable described in the above (12), the pressure adjusting unit is provided in a bypass line branched from the circulation loop and heat exchanger that vaporizes the liquefied gas introduced through the bypass line; And a flow rate adjusting valve capable of supplying the vaporized gas vaporized by the exchanger to the space above the liquefied gas for storing in the storage tank. When the pressure in the storage tank drops, the flow control valve is opened, liquefied gas is flowed from the circulation loop to the bypass line, vaporized by the heat exchanger, and the vaporized vaporized gas is supplied to the space of the storage tank To do. For this reason, the pressure in a storage tank can be raised. For this reason, generation | occurrence | production of the discharge within a superconducting cable can be prevented reliably.

(13) In some embodiments, in the cooling system for a superconducting cable according to (9) or (10) above,
A pressure detector for detecting the pressure of the space above the liquefied gas in the storage tank;
A temperature detector for detecting the temperature of the liquefied gas delivered from the delivery pipe;
Based on the detection values detected by the pressure detection unit and the temperature detection unit, the operations of the pressure adjustment unit and the cooling unit are controlled so that the liquefied gas flowing through the circulation loop is maintained in a subcooled state. And a control unit.

  According to the cooling system for a superconducting cable described in (13) above, a pressure detection unit that detects the pressure in the space above the liquefied gas in the storage tank, and the temperature of the liquefied gas delivered from the delivery pipe are detected. And the operation of the pressure adjusting unit and the cooling unit so that the liquefied gas flowing through the circulation loop is maintained in the subcooled state based on the detected values detected by the temperature detecting unit and the pressure detecting unit and the temperature detecting unit. And a control unit for controlling. When the liquefied gas circulating in the circulation loop is vaporized, there is a risk that the dielectric breakdown starts in the insulator constituting the superconducting cable. For this reason, since the temperature of the liquefied gas needs to be lower than the saturation temperature, it is necessary to detect the temperature of the liquefied gas. Moreover, since dielectric breakdown also occurs due to electric discharge, it is necessary to detect the pressure of the liquefied gas circulating in the circulation loop so that electric discharge does not occur. For this reason, it is possible to maintain the liquefied gas flowing through the circulation loop in the subcooled state by controlling the operation of the pressure adjusting unit and the cooling unit based on the detection values of the pressure detecting unit and the temperature detecting unit. it can.

  According to at least some embodiments of the present invention, a superconducting cable capable of cooling the superconducting cable to a desired temperature without excessive load on the cooler even if the temperature of the superconducting cable suddenly increases. A cooling system can be provided.

It is a conceptual diagram which shows the whole structure of the cooling system of the superconducting cable concerning one Embodiment of this invention. It is a partial explanatory view of a storage tank for explaining cooling of liquefied gas stored in a storage tank concerning one embodiment of the present invention. It is a partial expanded sectional view shown to A arrow of FIG. It is a graph which shows the relationship in the cooling system of the superconducting cable concerning one Embodiment of this invention, the temperature of liquefied gas, and calorie | heat amount. It is a conceptual diagram which shows the whole structure of the cooling system of the superconducting cable concerning other embodiment of this invention.

  Embodiments of the present invention will be described below with reference to FIGS. 1 to 5 with reference to the accompanying 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.

  For example, expressions expressing relative or absolute arrangements such as “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial” are strictly In addition to such an arrangement, it is also possible to represent a state of relative displacement with an angle or a distance such that tolerance or the same function can be obtained.

  For example, an expression indicating that things such as “identical”, “equal”, and “homogeneous” are in an equal state not only represents an exactly equal state, but also has a tolerance or a difference that can provide the same function. It also represents the existing state.

  For example, expressions representing shapes such as quadrangular shapes and cylindrical shapes represent not only geometrically strict shapes such as quadrangular shapes and cylindrical shapes, but also irregularities and chamfers as long as the same effects can be obtained. A shape including a part or the like is also expressed.

  On the other hand, the expressions “comprising”, “comprising”, “comprising”, “including”, or “having” one constituent element are not exclusive expressions for excluding the existence of the other constituent elements.

  In the following description, the same components may be denoted by the same reference numerals and detailed description thereof may be omitted.

  FIG. 1 is a conceptual diagram showing the overall configuration of a cooling system for a superconducting cable according to an embodiment of the present invention. As shown in FIG. 1, the cooling system for a superconducting cable according to this embodiment includes a storage tank 1 that stores a liquefied gas W (for example, liquid nitrogen), and a circulation pump that circulates the liquefied gas W stored in the storage tank 1. P, a circulation loop 30 having a cooling unit 31 for cooling the circulating liquefied gas W, and a pressure adjusting unit 40 for making the pressure of the vaporized gas A in the storage tank 1 constant, the liquefied gas W being in a subcooled state The superconducting cable C is cooled by circulating it. And in the storage tank 1, the return pipe 33 which returns the liquefied gas W which cooled the superconducting cable C in the storage tank 1, and the sending pipe 35 which sends out the liquefied gas W cooled in the storage tank 1 from the storage tank 1 In the storage tank 1, the return pipe 33 and the delivery pipe 35 are arranged above the connection positions P <b> 1 and P <b> 2 connected to the storage tank 1 and stored in the liquefied gas W to be stored. A convection prevention plate 5 extending in the width direction of the storage tank 1 is provided.

  In the illustrated embodiment, the storage tank 1 is connected to a cylindrical body 1a extending in the vertical direction, a bottom 1b that is connected to the lower part of the body 1a and protrudes downward and curves, and an upper part of the body 1a. The top part 1c which protrudes upwards and curves is formed, and the inside is formed in hollow. The storage tank 1 is accommodated in an outer tank 7 disposed on the outside, and the space between the storage tank 1 and the outer tank 7 is decompressed by a vacuum pump (not shown) to form a vacuum heat insulating layer 8. . A space 10 is formed in the storage tank 1 above the liquid level of the liquefied gas W, and the space 10 is filled with vaporized gas A (nitrogen gas).

  A delivery pipe 35 is connected to one end of the bottom 1 b of the storage tank 1, and a return pipe 33 is connected to the other end of the bottom 1 b of the storage tank 1. A circulation pump P is provided in the delivery pipe 35 extending from the storage tank 1. The circulation pump P pumps the cooled liquefied gas W to the superconducting cable C via the delivery pipe 35 to cool the superconducting cable C. The liquefied gas W (liquid nitrogen) after cooling the superconducting cable C is returned to the storage tank 1 via the return pipe 33. Thus, the return pipe 33 and the delivery pipe 35 form a circulation loop 30, and the liquefied gas W is configured to circulate through the circulation loop 30 by the circulation pump P.

  In the illustrated embodiment, the convection prevention plate 5 provided in the liquefied gas W stored in the storage tank 1 is disposed below the trunk 1 a above the bottom 1 b of the storage tank 1. The convection prevention plate 5 is a plate-like member having a shape similar to the cross-sectional shape of the body portion 1a in plan view, and a gap 12 is formed between the outer edge portion of the convection prevention plate 5 and the inner surface of the body portion 1a. Yes. This gap 12 makes it easy to insert the convection prevention plate 5 into the body 1a. Further, the convection prevention plate 5 is formed of a material having heat insulation properties. Therefore, the heat of the liquefied gas W ′ stored above the convection prevention plate 5 is prevented from being transferred to the liquefied gas W stored below the convection prevention plate 5 and causing the temperature of the liquefied gas W to rise. . The specific gravity of the convection prevention plate 5 is preferably the same as or slightly larger than that of the liquefied gas W.

  Although the delivery pipe 35 and the return pipe 33 are connected to the storage tank at a position below the convection prevention plate 5, in the illustrated embodiment, the return pipe 33 is the other end of the bottom 1 b of the storage tank 1. The delivery pipe 35 is connected to the upper part of the one end of the bottom 1b of the storage tank 1 above the return pipe 33.

  Here, since the liquefied gas W flowing into the storage tank 1 from the return pipe 33 is the liquefied gas W after cooling the superconducting cable C, its temperature becomes higher than the temperature of the liquefied gas W before cooling. . For this reason, when the convection prevention plate 5 is not provided in the storage tank 1, when the liquefied gas W whose temperature has increased flows into the storage tank 1, the liquefied gas W stored in the storage tank 1 Due to the temperature difference between them, the liquefied gas W generates convection that moves in the vertical direction in the storage tank 1. Accordingly, since the liquefied gas W having a relatively high temperature is stored in the upper part of the liquefied gas W stored in the storage tank 1, and the liquefied gas W having a relatively low temperature is stored in the lower part of the storage tank 1, the superconducting cable C There is a possibility that the liquefied gas W after being cooled cannot be cooled. However, in the present embodiment, by providing the convection prevention plate 5 extending in the storage tank width direction in the storage tank 1, the convection of the liquefied gas moving in the vertical direction is prevented, so that the convection of the liquefied gas W is prevented. can do. Therefore, heat exchange is performed between the liquefied gas W after cooling the superconducting cable C and the liquefied gas W stored in the storage tank 1 to cool the liquefied gas W after cooling the superconducting cable C. Can do.

  Superconducting cable C is formed in a double tube structure including an inner tube (not shown) and an outer tube disposed so as to surround the outer side of the inner tube. A refrigerant forward path Ca is formed in the internal space of the inner pipe, a refrigerant return path Cb is formed in the space between the inner pipe and the outer pipe, a thermal insulator is formed between the refrigerant forward path Ca and the refrigerant return path Cb, A superconducting conductor is provided on the outer peripheral side, and the superconducting cable C is cooled by the liquefied gas W flowing in the refrigerant return path.

  FIG. 2 is a partial explanatory view of the storage tank 1 for explaining cooling of the liquefied gas W stored in the storage tank 1 according to the embodiment of the present invention, and FIG. It is a partial expanded sectional view shown. As shown in FIG. 2, the cooling unit 31 cools the liquefied gas W stored below the convection preventing plate 5, that is, the convection preventing plate among the liquefied gas W stored below the convection preventing plate 5. 5 is disposed at a position for cooling the liquefied gas W adjacent to 5.

  In the illustrated embodiment, the cooling unit 31 includes the body 1a of the storage tank 1 that surrounds the liquefied gas W that is close to the convection prevention plate 5 among the liquefied gas W stored in the storage tank 1 below the convection prevention plate 5. It is arranged so as to surround the outer surface of the side wall 1d. The cooling unit 31 is configured as a heat exchanger 31 ′ of the cooling device 32. As shown in FIG. 3, the heat exchanger 31 ′ has a plurality of pipes 37 that form flow paths through which the refrigerant flows. The plurality of pipes 37 are arranged so as to be wound while being in contact with each other along the circumferential direction of the outer side surface of the trunk portion 1 a of the storage tank 1. This heat exchanger 31 ′ constitutes a part of a cooling device 32 (see FIG. 1) capable of cooling the refrigerant. The operation of the cooling device 32 is controlled by the control unit 45.

  Thus, since the heat exchanger 31 ′ is disposed so as to cool the liquefied gas W stored below the convection prevention plate 5 and close to the convection prevention plate 5, the convection prevention plate 5. In the liquefied gas W stored below, the liquefied gas W whose temperature has increased in the vicinity of the convection prevention plate 5 can be effectively cooled.

  A guide channel 47 for guiding the liquefied gas W discharged from the return pipe 33 to the delivery pipe 35 is formed in the storage tank 1 below the convection prevention plate 5 as shown in FIG. The guide channel 47 is configured to have a plurality of floor plates 49 that extend in the width direction of the storage tank 1 and are spaced apart in the vertical direction in the storage tank 1.

  In the illustrated embodiment, the plurality of floor boards 49 are arranged with a certain interval in the vertical direction, and the two floor boards 49 adjacent in the vertical direction are staggered in the storage tank width direction. . For this reason, the liquefied gas W discharged from the return pipe 33 flows along the guide flow path 47 formed below the floor plate 49 and exceeds the width direction end of the floor plate 49 above the floor plate 49. A direction changing flow path 47a for changing the direction of the flow of the liquefied gas W is formed by another extending slat 49 '. The volume of the direction changing flow path 47a is formed so as to increase as it is positioned upward. For this reason, in the direction change flow path 47a located in the upper direction, the flow of the liquefied gas W becomes comparatively slow compared with the direction change flow path 47a located in the lower direction. Accordingly, since the liquefied gas W flowing inside the heat exchanger 31 ′ flows through the direction change flow path 47a having a relatively large volume, sufficient heat exchange can be performed with the heat exchanger 31 ′. For this reason, the liquefied gas W can be effectively cooled to a desired temperature.

  In the illustrated embodiment, the plurality of laying plates 49 are provided so as to extend in a substantially horizontal direction, but the plurality of laying plates 49 may extend in an inclined state.

  The pressure of the vaporized gas A in the space 10 formed in the upper part of the storage tank 1 is controlled by a pressure adjusting unit 40 as shown in FIG. The pressure adjusting unit 40 is provided in a bypass line 51 branched from the circulation loop 30 and vaporizes the liquefied gas W introduced through the bypass line 51, and the vaporized gas A vaporized by the heat exchanger 52 And a flow rate adjusting valve 55 capable of supplying the gas to the space 10 in the storage tank 1.

  In the illustrated embodiment, the bypass line 51 is provided between the return pipe 33 and the space 10 of the storage tank 1 so as to branch a part of the liquefied gas W (liquid nitrogen) flowing through the return pipe 33 of the circulation loop 30. Are connected to communicate. The bypass line 51 is provided with an evaporator 52 ′ (heat exchanger 52) that vaporizes the liquefied gas W. The bypass line 51 upstream of the evaporator 52 ′ is provided with a flow rate adjusting valve 55 that can adjust the flow rate of the liquefied gas W flowing to the evaporator 52 ′ side. The pressure of the vaporized gas A in the space 10 of the storage tank 1 can be adjusted by adjusting the opening degree of the flow rate adjustment valve 55. The opening degree of the flow rate adjustment valve 55 is adjusted by the control unit 45.

  The cooling system for the superconducting cable C configured as described above includes a pressure detector 15 that detects the pressure in the space 10 above the liquefied gas W in the storage tank 1 and a liquefied gas that is sent out from the delivery pipe 35. Based on the temperature detection unit 17 that detects the temperature of W, and the respective detection values detected by the pressure detection unit 15 and the temperature detection unit 17, the liquefied gas W flowing through the circulation loop 30 is maintained in the subcooled state. And a control unit 45 that controls the operation of the pressure adjustment unit 40 and the cooling unit 31.

  In the illustrated embodiment, the temperature detection unit 17 is provided in a delivery pipe 35 extending to a position close to the heat exchanger 31 ′ in the delivery pipe 35 extending from the storage tank 1. For this reason, it is possible to detect the temperature of the liquefied gas W immediately after being cooled by the heat exchanger 31 ′. The control unit 45 is electrically connected to the pressure detection unit 15, the temperature detection unit 17, the cooling device 32, and the flow rate adjustment valve 55.

  The control unit 45 controls the operation of the cooling device 32 so that the temperature of the liquefied gas W delivered from the delivery pipe 35 is lower than the saturation temperature. Further, the control unit 45 controls the opening degree of the flow rate adjusting valve 55 so that the pressure of the vaporized gas A in the space 10 in the storage tank 1 does not become smaller than the pressure at which no discharge occurs in the superconducting cable C.

  Here, the temperature of the liquefied gas W delivered from the delivery pipe 35 can be adjusted by changing the operating conditions of the cooling device 32 (for example, the cooling temperature of the refrigerant and the flow rate of the refrigerant). it can. However, when the temperature fluctuation of the superconducting cable C becomes relatively large, it is necessary to lower the cooling temperature of the refrigerant in the cooling device 32 or increase the flow rate of the refrigerant, and the load on the cooling device 32 May increase and the superconducting cable C may not be efficiently cooled.

  Therefore, even when the temperature fluctuation of the superconducting cable C is relatively large, the cooling device 32 enables the superconducting cable C to be efficiently cooled, so that the storage tank 1 below the convection prevention plate 5 in the storage tank 1 can be cooled. The volume is set. That is, the volume of the storage tank 1 below the convection prevention plate 5 in the storage tank 1 is stored in the storage tank 1 below the convection prevention plate 5 and the cooling capacity of the heat exchanger 31 ′ of the cooling unit 31. It is set based on the heat storage amount of the liquefied gas W to be performed.

  For this reason, when the temperature of the superconducting cable C suddenly increases, the liquefied gas W whose temperature has been increased by cooling the superconducting cable C is cooled by the heat exchanger 31 ′ and heat exchange with the stored liquefied gas W. Cooling can ensure cooling. For this reason, even if the temperature of the superconducting cable C rises rapidly, the superconducting cable C can be efficiently cooled to a desired temperature without causing an excessive load on the cooling device 32.

  FIG. 4 is a graph showing the relationship between the time in the cooling system of the superconducting cable C according to the embodiment of the present invention, the temperature of the liquefied gas W, and the cooling capacity. One vertical axis of the graph shown in FIG. 4 indicates the temperature of the liquefied gas W, the other vertical axis indicates the cooling capacity of the liquefied gas W, and the horizontal axis of the graph indicates the elapsed time. As shown in FIG. 4, the solid line A represents the heat storage tank inlet temperature, and the broken line B represents the heat storage tank outlet temperature. A one-dot chain line C represents cooling capacity, and a two-dot chain line D represents total cable heat loss. When the total heat loss of the superconducting cable (two-dot chain line D) increases rapidly, the heat storage tank inlet temperature (solid line A) increases rapidly. Corresponding to this load, the cooling device 32 exhibits the cooling capacity indicated by the alternate long and short dash line C, and the storage tank 1 is cooled by the heat exchanging portion 31, so that the liquefied gas W delivered from the delivery pipe 35 of the storage tank 1 It can be seen that the temperature change is small (see broken line B). It can also be seen that when the cooling capacity changes rapidly, the time until the temperature of the liquefied gas W stabilizes is also relatively short (see broken line B).

  As mentioned above, although the preferable form of this invention was demonstrated, this invention is not limited to said form, A various change in the range which does not deviate from the objective of this invention is possible.

  FIG. 5 is a conceptual diagram showing an overall configuration of a cooling system for a superconducting cable according to another embodiment of the present invention. In other embodiments, only differences from the above-described embodiment will be described, and the same reference numerals will be given to the same aspects as the above-described embodiment, and description thereof will be omitted.

  As shown in FIG. 5, the cooling unit 60 includes a lead-out pipe 61 that leads out the liquefied gas W stored in the storage tank 1 below the convection prevention plate 5, and a liquefied gas W that is led out by the lead-out pipe 61. A cooling device 32 for cooling, an introduction pipe 62 for returning the liquefied gas W cooled by the cooling device 32 into the storage tank 1 below the convection prevention plate 5, and a liquefaction in the storage tank 1 provided in the outlet pipe 61. A derivation pump 63 that sends out the gas W to the derivation pipe 61.

  In the illustrated embodiment, the return pipe 33 for returning the liquefied gas whose temperature has been raised by cooling the superconducting cable C to the storage tank 1 is connected to the upper part on one side of the storage tank 1 below the convection prevention plate 5. Has been. The delivery pipe 35 is connected to one side of the bottom of the storage tank 1. On the other hand, the end of the introduction pipe 62 on the side where the liquefied gas is introduced is connected to the upper part on the other side of the storage tank 1 below the convection prevention plate 5. The lead-out pipe 61 is connected to the other side of the bottom of the storage tank 1 at the end on the lead-out side of the liquefied gas.

  The liquefied gas W in the storage tank 1 led out by the lead-out pump 63 through the lead-out pipe 61 is cooled by the cooling device 32 and returned to the storage tank 1 through the introduction pipe 62. Thus, the outlet pipe 61 and the inlet pipe 62 form a circulation loop 64, and the liquefied gas W is configured to circulate through the circulation loop 64 by the outlet pump P.

  Thus, the liquefied gas W stored in the storage tank 1 below the convection prevention plate 5 of the storage tank 1 is forcibly cooled by the circulation loop 64. For this reason, the liquefied gas that has cooled the superconducting cable C and increased in temperature and returned to the storage tank 1 is mixed with the liquefied gas that has been forcibly cooled by the circulation loop 64 and cooled. For this reason, even if the temperature of the superconducting cable C rapidly rises, the superconducting cable C can be cooled to a desired temperature without causing an excessive load on the cooling device 32.

DESCRIPTION OF SYMBOLS 1 Storage tank 1a Body part 1b Bottom part 1c Top part 1d Side wall 5 Convection prevention board 7 Outer tank 8 Vacuum heat insulation layer 10 Space part 12 Crevice 15 Pressure detection part 17 Temperature detection part 30, 64 Circulation loop 31, 60 Cooling part 31 ', 52 Heat exchange section 32 Cooling device 33 Return pipe 35 Delivery pipe 37 Pipe 40 Pressure adjustment section 45 Control section 47 Guide flow path 47a Direction change flow path 49 Base plate 51 Bypass line 52 'Evaporator 55 Flow rate adjustment valve 61 Outlet pipe 62 Introduction pipe 63 Introduced pump A Vaporized gas C Superconducting cable Ca Refrigerant forward path Cb Refrigerant return path P Circulation pump P1, P2 Connection position W, W 'Vaporized gas

Claims (13)

A storage tank for storing the liquefied gas, a circulation pump for circulating the liquefied gas stored in the storage tank, a circulation loop having a cooling unit for cooling the liquefied gas to be circulated, and a vaporization gas in the storage tank A superconducting cable cooling system comprising: a pressure adjusting unit configured to make the pressure constant; and cooling the superconducting cable by circulating the liquefied gas in a subcooled state,
The storage tank is connected to a return pipe that returns the liquefied gas that has cooled the superconducting cable into the storage tank, and a delivery pipe that delivers the liquefied gas cooled in the storage tank from the storage tank,
In the storage tank, each of the return pipe and the delivery pipe is positioned above the connection position connected to the storage tank and is stored in the liquefied gas to be stored in the width direction of the storage tank. A superconducting cable cooling system, characterized in that an extended convection prevention plate is provided. The cooling system for a superconducting cable according to claim 1, wherein the cooling unit is disposed at a position for cooling the liquefied gas stored below the convection prevention plate. The position of the said cooling part is a position which cools the liquefied gas adjacent to the said convection prevention board among the liquefied gas stored below the said convection prevention board. The superconducting cable of Claim 2 characterized by the above-mentioned. Cooling system. The guide channel for guiding the liquefied gas discharged from the return pipe to the delivery pipe is formed in the storage tank below the convection prevention plate. Superconducting cable cooling system. In the storage tank, the guide flow path is configured to include a plurality of floor plates extending in the width direction of the storage tank and arranged with an interval in the vertical direction. The cooling system for a superconducting cable according to claim 4. The return pipe is connected to the storage tank below the convection prevention plate,
The cooling system for a superconducting cable according to claim 5, wherein the delivery pipe is connected to the storage tank below the convection prevention plate and above the return pipe. The cooling unit is a cooling device disposed on an outer surface of the side wall of the storage tank that surrounds the liquid gas that is close to the convection prevention plate among the liquid gas stored in the storage tank below the convection prevention plate. The cooling system for a superconducting cable according to claim 2, wherein the cooling system is a heat exchanger. The cooling system for a superconducting cable according to claim 7, wherein the storage tank is accommodated in an outer tank, and a space between the storage tank and the outer tank constitutes a vacuum heat insulating layer. The volume below the convection prevention plate in the storage tank is such that the liquefied gas delivered from the delivery pipe is cooled to a predetermined temperature in a subcooled state, and the cooling capacity of the heat exchanger of the cooling unit, The cooling system for a superconducting cable according to claim 7 or 8, wherein the cooling system is set based on a heat storage amount of a liquefied gas stored in the storage tank below the convection prevention plate.
The cooling unit includes a lead-out pipe that leads out the liquefied gas stored in the storage tank below the convection prevention plate, a cooling device that cools the liquid gas led out from the lead-out pipe, and the cooling device. A return pipe that returns the cooled liquefied gas into the storage tank below the convection prevention plate, and a lead-out pump that is provided in the lead-out pipe and sends the liquid gas in the storage tank to the lead-out pipe. The cooling system for a superconducting cable according to claim 1. The cooling system for a superconducting cable according to any one of claims 1 to 10, wherein a space for storing a gas phase is formed above the liquefied gas stored in the storage tank. The pressure adjusting unit is provided in a bypass line branched from the circulation loop, and heat exchanger for vaporizing the liquefied gas introduced through the bypass line; and the vaporized gas vaporized by the heat exchanger in the storage tank The cooling system for a superconducting cable according to claim 1, further comprising a flow rate adjustment valve that can be supplied to a space above the liquefied gas stored therein. A pressure detector for detecting the pressure of the space above the liquefied gas in the storage tank;
A temperature detector for detecting the temperature of the liquefied gas delivered from the delivery pipe;
Based on the detection values detected by the pressure detection unit and the temperature detection unit, the operations of the pressure adjustment unit and the cooling unit are controlled so that the liquefied gas flowing through the circulation loop is maintained in a subcooled state. The superconducting cable cooling system according to claim 9 or 10, further comprising:

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