WO2006001203A1

WO2006001203A1 - Cooling system for superconducting power apparatus

Info

Publication number: WO2006001203A1
Application number: PCT/JP2005/010936
Authority: WO
Inventors: Shinichi Mukoyama; Noboru Ishii; Masashi Yagi; Satoru Maruyama; Tatsuki Okamoto; Hiroshi Suzuki; Michiharu Ichikawa; Toshihiro Takahashi; Shirabe Akita
Original assignee: The Furukawa Electric Co., Ltd.; Central Research Institute Of Electric Power Industry
Priority date: 2004-06-28
Filing date: 2005-06-15
Publication date: 2006-01-05
Also published as: KR20070036027A; CN1969158B; EP1780482A4; KR101142901B1; CN1969158A; JP4728601B2; JP2006012654A; EP1780482A1; US20080202127A1

Abstract

A cooling system for a superconducting power apparatus, having a reservoir for storing liquid gas, a circulation pump, a heat exchanger for cooling the liquid gas, and a circulation loop in which a liquefied gas circulates, the liquefied gas being circulated in a subcooled state by using the circulation pump to cool the superconducting power apparatus, wherein the cooling system further has pressurizing means for pressurizing the reservoir by the same kind of gas as the liquefied gas, and the liquid level of the reservoir for storing the liquefied gas in a pressurized state is positioned above the exit of a return line of the circulating liquefied gas by at least an amount equal to the sum of the depth of dissolution of the pressurizing gas and of the amount of correction of liquid level movement.

Description

Specification

Cooling system for superconducting power equipment

Technical field

[0001] The present invention relates to a cooling system for cooling superconducting cables, superconducting bus lines, SMES, superconducting transformers, etc., which can be industrially used in a superconducting state after being cooled by a liquefied gas such as liquid nitrogen. In particular, the present invention relates to a cooling system for cooling superconducting power equipment in which equipment is operated in a high voltage state.

Background art

[0002] As one of superconducting power devices, a conventional technique will be described with reference to FIG. 6 by taking a superconducting cable using a liquefied gas such as liquid nitrogen for cooling as an example. As a cooling system for a superconducting cable, one described in Japanese Patent Laid-Open No. 08-148044 is known. As shown in FIG. 6, in the conventional cooling system, the liquid gas in the subcooled state (the liquid gas is cooled below the saturation temperature of the liquid gas) from the reservoir tank 101. The circulation cycle is repeated, in which the pressure is increased by the pump 105, cooled by the heat exchanger 107 of the refrigerator 108, supplied to the cable 111, and returned to the reservoir tank 101 again.

[0003] In the case of cooling a superconducting cable, if the liquefied gas to be circulated is in a gas-liquid mixed state, the pressure loss increases and the required amount of liquefied gas cannot be circulated stably, resulting in a large capacity. It is necessary to prepare a large circulation pump. In addition, the superconducting cable employs a cryogenic electrical insulation system that maintains high electrical insulation performance by impregnating the liquefied gas into the insulator, so that gases and bubbles are mixed in the liquid gas. If so, there is a problem that the electrical insulation performance is significantly lowered.

[0004] Therefore, in the conventional cooling system, the liquid gas is always maintained in the subcooled state and circulated without being vaporized. For example, when liquid nitrogen is used as the liquefied gas, the reservoir The tank 101 is pressurized by supplying hydrogen (H) or helium (He), which is a gas whose triple point is sufficiently lower than the liquid gas, with a cylinder 123, etc.

2

The boiling point of the gas is increased so that the liquid gas does not boil during circulation (ie, it does not become a gas-liquid mixed state). Patent Document 1: Japanese Patent Laid-Open No. 08-148044

Disclosure of the invention

Problems to be solved by the invention

[0005] As in the prior art, in a reservoir tank, a gas whose triple point is sufficiently lower than liquid gas, for example, liquid nitrogen as liquid gas is pressurized with helium (He) gas. However, the phenomenon that a small amount of He gas dissolves in liquid nitrogen occurs. In other words, helium (He) is widely known as an inert gas, and it was recognized that it does not dissolve in liquid nitrogen. In reality, it was found that a very small amount of He gas dissolves in liquid nitrogen.

[0006] The amount dissolved in the liquid nitrogen is very small. When the liquid gas in which the He gas is dissolved is circulated, for example, the portion where the flow rate of the liquefied gas that the pipe expands becomes relatively slow, or for example, In a part where the pressure of the liquid gas suddenly decreases, such as after being throttled by a valve from the reservoir tank, the dissolved He gas cannot be maintained in the liquid gas. As a result, bubbles are formed and mixed in liquid nitrogen to be in a gas-liquid mixed state.

[0007] Also, if there is a part of the superconducting cable or superconducting power equipment that is positioned higher than the cooling system depending on the state of the installation layout, the generated bubbles accumulate and stay in the upper part of the equipment. As a result, the liquid nitrogen cooling pipe was eventually filled and it was impossible to circulate the liquid nitrogen.

[0008] It has been clarified by experiments of the inventor that the phenomenon described above is a phenomenon that occurs in a very long time of several months. If the He gas is contained in liquid nitrogen and the gas-liquid mixed state in the piping or the cooling piping is filled as the gas phase, the circulation force of liquid nitrogen cannot be smooth. Furthermore, since the withstand voltage characteristic of He gas is very small compared to other liquid gases, the insulation characteristic is improved by the contained He gas even though liquid nitrogen originally has high insulation characteristics. Lowering may cause poor insulation or breakdown of superconducting power equipment.

[0009] As a countermeasure, it was considered to pressurize the reservoir tank with the same type of gas as the liquefied gas. However, liquid nitrogen stored in the reservoir tank is liquid nitrogen at a temperature below the boiling point. In addition, when the nitrogen gas used for pressurization touches liquid nitrogen having a boiling point or less in the reservoir tank, the nitrogen gas used for pressurization is cooled and becomes liquid. For that purpose, pressurize The pressure is reduced and the cylinder pressure cannot be kept constant unless nitrogen gas is constantly supplied. As a result, a large amount of nitrogen gas is consumed, and a large amount of liquid gas is consumed. There was a problem that heat was brought into the cooling system and the heat load increased.

[0010] Therefore, an object of the present invention is to provide an instability factor of the circulation of the liquid gas, because the gas having a lower boiling point than the liquid gas used for pressurization is dissolved in the liquid gas. It is an object to provide a cooling system for superconducting power equipment that can circulate liquid gas smoothly in a subcooled state for a long period of time without causing problems related to insulation.

Means for solving the problem

[0011] The present inventor has intensively studied to solve the above-described problems of the prior art. As a result, a small amount of He gas dissolves in liquid nitrogen by pressurizing the reservoir tank, which is conventionally not used as pressurized gas, with the same type of gas as liquid gas. Can be eliminated. As a result, in the part where the pressure of the liquefied gas suddenly decreases, the He gas becomes bubbles, mixed into the liquid nitrogen and becomes a gas-liquid mixed state, and the circulation of the liquid nitrogen cannot be smoothly performed, and the insulation characteristics are improved. It has been found that the problem of deterioration can be solved. Similarly, if the height difference due to the arrangement of superconducting power equipment exceeds the specified value, the generated bubbles will stay in the upper part of the equipment and fill the cooling loop, making it impossible to circulate liquid nitrogen. It turns out that it can be solved.

[0012] Further, the liquid level of the reservoir tank that stores the liquid gas in a pressurized state is at least the depth of the pressurized gas dissolved + the liquid level movement correction amount from the outlet of the return line of the circulating liquefied gas By being positioned only at the top, the nitrogen gas used for pressurization is liquefied, and the pressurized pressure is reduced. If the cylinder gas is not continuously supplied, the pressure is kept constant. It has been found that the problem of not being able to be solved can be solved. Therefore, the problem that a large amount of nitrogen gas is consumed and a large amount of liquid heat is brought into the cooling system and the heat load increases is solved.

[0013] The present invention has been made based on the above research results, and the first aspect of the cooling system for a superconducting power device according to the present invention is a reservoir tank for storing liquid gas, a circulation pump, and liquid gas. And a circulation loop through which the liquefied gas circulates, and the liquid gas is circulated in a subcooled state using a circulation pump to superconducting power. A superconducting power equipment cooling system for cooling equipment, further comprising pressurizing means for pressurizing the reservoir tank with the same kind of gas as the liquid gas, and storing the liquefied gas in a pressurized state. The cooling system for a superconducting power device, characterized in that the surface is positioned at least above the outlet of the return line of the circulating liquid gas and gas by at least the penetration depth of the pressurized gas + the liquid level movement correction amount It is.

[0014] In the second aspect of the cooling system for superconducting power equipment according to the present invention, the pressurizing means for pressurizing the reservoir tank with the same kind of gas as the liquefied gas stores the same kind of gas as the liquefied gas at a high pressure. It is a cooling system for superconducting power equipment characterized by comprising pressurizing at a predetermined pressure from a gas cylinder through a pressure regulating valve.

[0015] In a third aspect of the cooling system for a superconducting power device according to the present invention, the pressurizing means for pressurizing the reservoir tank with the same kind of gas as the liquefied gas delivers the liquefied gas in a reservoir tank force subcooled state. It consists of pressurizing the reservoir tank using the discharge pressure of the circulation pump by piping returning from the outlet of the circulation pump to a part of the liquid gas sent to the superconducting power device and returning to the reservoir tank. This is a cooling system for superconducting power equipment.

[0016] In a fourth aspect of the cooling system for superconducting power equipment according to the present invention, the pressurizing means for pressurizing the reservoir tank with the same kind of gas as the liquefied gas sends out the liquefied gas in the subcooled state of the reservoir tank. Vaporizer that vaporizes liquid gas and pressure adjustment for pressure adjustment provided in piping that branches from a part of the liquid gas sent to the superconducting power equipment from the outlet of the circulation pump and returns to the reservoir tank It is a cooling system for superconducting power equipment, characterized by comprising a valve.

[0017] A fifth aspect of the cooling system for a superconducting power apparatus according to the present invention further includes auxiliary means for the pressurizing means, and the auxiliary means supplies the same kind of gas as the liquid gas from the gas cylinder. It is a cooling system for superconducting power equipment characterized by comprising pressurizing

[0018] A sixth aspect of the cooling system for a superconducting power device according to the present invention further comprises auxiliary means for the pressurizing means, and the auxiliary means has a heating device disposed in a gas phase portion of the reservoir tank, Consisting of superheated volume expansion of the gas in the gas phase of the reservoir tank This is a cooling system for superconducting power equipment.

The invention's effect

[0019] According to the present invention, the reservoir tank is pressurized with the same kind of gas as the liquid gas, so that the liquid nitrogen is smoothly circulated without bubbles being mixed in the liquid nitrogen, and the superconducting power device having excellent insulation characteristics Cooling system can be provided. Further, according to the present invention, the liquid level of the reservoir tank that stores the liquefied gas in a pressurized state is at least the depth of penetration of the pressurized gas plus the liquid level from the outlet of the return line of the circulating liquid gas. Since it is located at the top by the amount of movement correction, it is possible to provide a cooling system for superconducting power equipment in which the pressure used without pressurizing the gas used to pressurize the reservoir tank does not decrease. it can.

Brief Description of Drawings

FIG. 1 is a diagram illustrating a method of pressurizing a reservoir tank with a circulation pump outlet pressure according to the present invention.

FIG. 2 is a configuration diagram of a cooling system for explaining Example 1 of the present invention.

FIG. 3 is a configuration diagram in the vicinity of a reservoir tank for explaining Example 2 of the present invention.

FIG. 4 is a configuration diagram in the vicinity of a reservoir tank for explaining Example 3 of the present invention.

[FIG. 5] FIG. 5 is a diagram showing the relationship between the pressure gas penetration depth [m] and the pressure reduction rate [%].

FIG. 6 is a diagram for explaining a conventional superconducting cable cooling system.

Explanation of symbols

[0021] 1 Reservoir tank

lb inner reservoir tank

2 Liquid nitrogen liquid level in reservoir tank

3 Liquid inlet

4, 6, 9 Feed side liquid nitrogen circulation piping

5 Circulation pump 5a Circulation pump motor

5b circulation pump long shaft

5c fin

5e vacuum container

7 Refrigerator heat exchanger

8 Refrigerator

10 Entrance of superconducting power equipment

11 Superconducting cable

12 Superconducting cable outlet

13 Return side liquid nitrogen circulation piping

14 Nitrogen return piping in reservoir tank

15 Nitrogen return piping outlet

16, 18, 20 Branch piping for pressurization

17 Vaporizer

19 Valve

21 Pressurized external piping

22 High pressure nitrogen cylinder

23 Heater inside reservoir tank

BEST MODE FOR CARRYING OUT THE INVENTION

The cooling system for superconducting power equipment according to the present invention will be described in detail with reference to the drawings.

The cooling system for superconducting power equipment according to the present invention includes a reservoir tank for storing liquid gas, a circulation pump, a heat exchanger for cooling the liquid gas, and a circulation loop for circulating the liquid gas, , A superconducting power equipment cooling system that circulates in a subcooled state using a circulation pump to cool superconducting power equipment, further comprising pressurizing means for pressurizing the reservoir tank with the same kind of gas as the liquid gas. Liquid level force of reservoir tank that stores pressurized gas under pressure At least the depth of the pressurized gas dissolved + the level shift correction amount above the outlet of the return line of the circulating liquid gas Specially located This is a cooling system for superconducting power equipment.

[0023] The liquid level of the reservoir tank that stores the liquid gas in a pressurized state is at least higher than the outlet of the return line of the circulating liquefied gas by at least the penetration depth of the pressurized gas + the liquid level movement correction amount. The need to be located is explained below.

The relationship between the penetration depth of the pressurized gas and the pressure reduction rate was investigated by experiment. Figure 5 shows the relationship between the pressure gas penetration depth [m] and the pressure reduction rate [%].

[0024] In FIG. 5, the depth at which the pressurized gas melts into the liquid level of the reservoir tank (that is, the depth at which the pressurized gas penetrates) is plotted on the horizontal axis. The reduction rate is shown on the vertical axis. As experimental conditions, a reservoir tank having an inner diameter of lm and a height of lm was used, and the pressure was set to 0.3 MPa. As a result, as is clear from FIG. 5, when the penetration depth is up to 10 cm, the rate of decrease in pressure is remarkably large, and when the penetration depth is up to about 20 cm, the gaseous nitrogen gas used for pressurization becomes liquid. Condensed and pressurized pressure is still decreasing rapidly. On the other hand, if the penetration depth was kept at 20 cm or more, it was found that the pressure decrease could be kept at a small value of 1% or less. Actually, in addition to the penetration depth of the pressurized gas, the liquid level changes due to the influence of the temperature and pressure of liquid nitrogen, so it is necessary to consider the liquid level movement correction amount.

[0025] Accordingly, the liquid level force of the reservoir tank that stores the liquid gas in a pressurized state is at least the depth of penetration of the pressurized gas from the outlet of the return line of the circulating liquid gas + the liquid level movement correction amount It is only necessary to be located at the top. Specifically, the depth of penetration of the pressurized gas (20 cm) + the liquid level movement correction amount (30 cm) is preferably 50 cm or more. As described above, the required depth is almost the same even if the size of the reservoir tank depends on the container shape is small. Therefore, in the system of the present application, the container height of the reservoir tank needs to be high enough to ensure the required depth (preferably 50 cm or more).

[0026] As described above, the present invention is a system that cools a superconducting power device with liquid gas. A gas having a lower boiling point than the liquid gas used for pressurization is a liquid gas. It provides a cooling system that can circulate liquefied gas in a subcooled state for a long time without causing instability in the circulation of liquefied gas and troubles related to insulation of electrical equipment. . [0027] The pressurizing means for pressurizing in the above-described state consists of pressurizing the reservoir tank to a predetermined pressure with the same kind of gas as the liquid gas stored in the reservoir tank. In order to prevent the pressurized gas from being cooled by liquid gas, the reservoir tank liquid level is at least 20 cm above the outlet of the circulation pump return pipe in the reservoir tank. Preferably it is 50 cm or higher.

[0028] Furthermore, as means for pressurization, in addition to means for pressurization with a high-pressure gas cylinder, there is a means for pressurization by returning the circulation pump outlet pressure higher than the pressure of the reservoir tank to the reservoir tank. As a specific means of using the pressure at the outlet of the circulation pump, the outlet pipe of the circulation pump that pumps and pressurizes the reservoir tank fluid and feeds it to the superconducting power equipment is branched, and the liquid gas is discharged from the pressure of the reservoir tank. A part is taken out, the branched liquefied gas is gasified using a gasifier, and further the reservoir is connected via a pressure regulating valve that opens and closes according to the pressure for maintaining the pressure of the reservoir tank at a predetermined pressure. There is a means to return it to the tank.

In order to explain the operation of the present invention, the case where liquid nitrogen is used as the liquid gas will be described. The boiling point of liquid nitrogen at atmospheric pressure (1.013 MPa) is 77K. When this liquid nitrogen is pressurized to 0.3 MPa, the boiling point of liquid nitrogen becomes 90K or higher. Therefore, when 77K liquid nitrogen is pressurized to 0.3MPa, the liquid nitrogen enters a subcooled state where no bubbles are generated. The circulation pump's liquid withdrawal section is located at the bottom of the reservoir tank and is connected to the circulation pump by piping.

[0030] On the other hand, the return pipe of the circulation is a force connected to the reservoir tank. The position of the outlet of the pipe is lower than the liquid level. The liquid gas delivered from the circulation pump cools the superconducting power equipment and returns to the reservoir tank. At that time, since the piping outlet is located below the liquid level, the returned liquid gas does not touch the pressurized gas phase of the reservoir tank, moves to the liquid nitrogen inlet of the circulation pump, and circulates again. To do.

In the present invention, the position of the liquid level is set higher than a predetermined height (20 cm 2) of the liquid outlet of the piping outlet and the circulation pump (that is, a predetermined liquid gas layer is provided). The temperature of the liquid nitrogen above the subcooled cold liquid nitrogen at each piping port increases in order toward the liquid surface, and the liquid nitrogen temperature at the liquid surface is 0.3MPa liquid gas. Boiling temperature of It is almost the same as the degree. Therefore, in the past, when the pressure in the reservoir tank was pressurized with the same kind of gas, there was a problem that the gas was liquidated and the pressure dropped due to insufficient gas supply. As a result, it was found that almost no gas was liquefied.

[0032] In the present invention, a method other than the method of pressurizing with a cylinder was newly considered as a pressurizing method. The method of pressurizing with self pressure in the present invention will be described with reference to FIG. First, the reservoir internal force liquid nitrogen in the atmospheric pressure state (point a) is pumped out and pumped with a circulation pump. At the outlet of the circulation pump, liquid nitrogen flows at 50 L / min, and liquid nitrogen is pressurized to 0.2 MPa at the inlet (point b). When using the pressure at the outlet, the liquid nitrogen branched and pressurized from the outlet pipe is vaporized into gas by a vaporizer and returned to the reservoir tank to raise the pressure in the reservoir tank. . (Arrow.

[0033] In response to this, the outlet pressure of the circulation pump also increases (arrow d), and the reservoir tank can be constantly pressurized. When the pressure in the reservoir tank exceeds the upper limit set pressure (P2) (point e), the valve attached to the pipe is closed and the gas supply to the reservoir tank is stopped. Thereafter, in the reservoir, the nitrogen gas in the gas phase is cooled with liquid nitrogen below the triple point of the nitrogen gas, and the nitrogen gas in the gas phase becomes liquid and becomes liquid nitrogen. The pressure in the reservoir tank decreases as the gas volume decreases due to liquefaction (arrow f). When the lower limit set pressure (P1) is reached (point g), the valve is opened, and nitrogen gas is again supplied to the interior of the reservoir tank by the pressure at the circulation pump outlet, increasing the pressure in the reservoir tank.

[0034] Since the low-temperature nitrogen gas flows through the piping, the piping and valves may be frozen. As a vaporizer, liquid nitrogen is gasified to raise the temperature to room temperature in order to prevent it. There are several ways to increase the temperature by placing a heater in the piping, passing the piping through water, etc., or attaching fins to the piping to exchange heat with the outside air. In addition, the role of the nozzle is simply to keep pumping the gas through the branched pipe, and the reservoir tank pressure will continue to rise, possibly exceeding the design pressure of the reservoir tank. When the pressure exceeds the specified pressure, it closes and pressurization with gas stops, and when the pressure falls below the specified pressure, it opens.

It has a function to automatically maintain a constant pressure by pressurizing.

[0035] When the capacity of the reservoir tank is large, it is necessary to pressurize to a predetermined pressure. Since an amount of nitrogen gas is required, a separate nitrogen cylinder can be prepared and the pressure of the reservoir tank can be increased to a predetermined pressure. It is also possible to use a method in which a heating device such as a heater is disposed in the gas phase inside the reservoir tank, and the gas in the reservoir tank is pressurized and expanded to pressurize it.

Hereinafter, the present invention will be described in more detail by way of examples.

Example

[0036] Example 1

FIG. 2 is a diagram showing one embodiment of a cooling system for a superconducting power device according to the present invention. Liquid nitrogen is used as the liquid gas. Liquid nitrogen is stored in reservoir tank 1. Reservoir tank 1 has a double container structure. Between the double containers, insulation is installed so as to surround the inner container lb, and it is maintained in a vacuum state to reduce heat intrusion. Yes. In addition, the reservoir tank is a sealed container, which can be made by pressurizing the inside.

[0037] At the bottom of the reservoir tank, there is a liquid inlet 3 connected to the circulation pump, which is connected to the inlet of the circulation pump 5 by a pipe 4 having a diameter of 3 cm. The circulation pump 5 is a vortex-type rotary pump. The motor 5a for rotating the fin 5c and the fin are connected by a long shaft 5b of about 50 cm in order to suppress heat inflow due to conduction!

[0038] Further, the fin itself is arranged in the inside 5e of the vacuum vessel so as to suppress heat intrusion from the outside. The rotary pump of the present invention can flow a flow rate of 30 L / min as the flow rate of liquid nitrogen at a rotation speed of 50 Hz, and obtain a discharge pressure of 0.2 MPa as a pressure difference between the inlet and the outlet. Can do. From the pump outlet, a pipe 6 with a diameter of 3 cm leads to the heat exchange 7 of the freezer.

[0039] The refrigerator 8 is powered by a GM refrigerator, a Stirling refrigerator, etc., and a heat exchanger is connected to a low-temperature head for generating cold, and the circulating liquid nitrogen is cooled to a low temperature. In the present invention, a Stirling refrigerator having an refrigeration capacity of 1 kW is used. By passing through a heat exchanger ^^ cooled by a 30 L / min liquid nitrogen power refrigerator, the one that was 77 K at the inlet is used. Can be cooled to 74K.

[0040] The liquid nitrogen cooled by the refrigerator is connected to the superconducting power equipment inlet 10 through a pipe 9 having a diameter of 3 cm. It is connected to water tightly. A cooling system for cooling the superconducting cable 11 of this embodiment.

The superconducting cable is cooled by circulating the liquid nitrogen cooled by the refrigerator in the superconducting cable. The temperature of liquid nitrogen that has cooled the superconducting cable rises, but since the increased temperature is below the boiling point, a subcooled state in which no bubbles are generated in the liquid nitrogen is maintained. For this reason, even with a 500 m superconducting cable, the pressure loss is less than O.lMPa, and it is sufficiently small and allows liquid nitrogen to flow stably.

[0041] In addition, since liquid nitrogen permeates into the electric insulation layer of the superconducting cable without causing bubbles, the electric insulation can be maintained. Liquid nitrogen that has exited the outlet 12 of the superconducting cable returns to the reservoir tank 1 through the pipe 13 to form a circulation loop. The reservoir tank 1, the circulation pump 2, the heat exchange 3 of the refrigerator, the superconducting cable 4, and the nitrogen piping connecting these devices are all double containers that use vacuum insulation to reduce the intrusion heat from external forces. It has a structure.

[0042] The pipe 13 returned to the reservoir tank is a pipe 14 that reaches from the top to the bottom of the reservoir tank, and returns the liquid to the reservoir tank from the outlet 15 to the bottom of the reservoir tank. Also, the liquid connected to the circulation pump Inlet 3 is also located at the bottom of the reservoir tank. During the circulation, the liquid nitrogen in the reservoir tank is stored so that it is at least 20 cm higher than the outlet 15 position and the liquid level 2 is at the position.

[0043] In the method of pressurizing the reservoir tank by the outlet pressure of the circulation pump of the present invention, a stainless steel pipe 16 having a diameter of 6 mm is branched and taken out from the pipe 6 at the pump outlet. The liquid nitrogen passing through the inside of the pipe 16 exits from the vacuum vessel of the circulation pump, and then passes through the vaporizer 17 where everything is changed from liquid nitrogen to room temperature nitrogen gas.

[0044] As the vaporizer, in this embodiment, a copper hot water container with a copper 6mm piping force wound in a 6m coil shape is used, and the liquid nitrogen inside is heated by being immersed in the hot water. ing. As a vaporizer, in addition to this embodiment, for example, a heater is wound around the outside of the coil and the temperature is increased by heating the heater by energization, or fins are attached to the piping to exchange heat with the atmosphere. It is sufficient if the liquid nitrogen inside can be turned into room temperature gas, such as a heating method. The pipe 18 exiting the vaporizer 17 is filled with gas when the outlet pressure falls below a predetermined pressure. A nozzle 19 is installed that has a pressure control function that stops the gas when the pressure exceeds the specified pressure. The pipe 20 exiting the valve 19 is attached to the upper part of the reservoir tank so that the reservoir tank can be pressurized.

[0045] The pipes 18 and 20 after passing through the vaporizer 17 are at room temperature, so there is no need for a heat insulation structure. However, the circulation pump outlet force and the pipe 16 up to the vaporizer are made of a heat insulating material such as urethane foam. It is more aesthetically preferable that the pipe 16 is not frosted. Note that if the valve 19 is operated at a low temperature, the position of the valve 19 and the vaporizer 17 can be reversed. The low temperature valve is more expensive than the normal temperature, and economically. It is not an appropriate arrangement. In this example, the pressure extraction pipe 16 was taken out from the pump outlet pipe 6. However, the pressure in the reservoir tank could be from the refrigerant heat exchanger outlet pipe 9 or the superconducting equipment inlet 10. As long as it is higher, the object of the present invention can be achieved no matter where it is taken out. In this sense, the pump outlet is not simply indicated as the immediate vicinity of the pump outlet, but all downstream from the pump outlet is collectively referred to. Yes.

[0046] Example 2

In the first embodiment, the case where the circulation pump is outside the reservoir tank has been described. However, the present invention can be implemented even when the circulation pump is inside the reservoir tank. FIG. 3 is a diagram showing one part of another embodiment of the cooling system for a superconducting power device according to the present invention. That is, FIG. 3 shows an extraction diagram of the reservoir tank portion in order to explain the present embodiment in the cooling system. Of the circulation pump 5, the fin portion 5c for sending the liquid is in the liquid in the reservoir tank, and the rotation of the motor 5a is transmitted by the long shaft 5b. Liquid nitrogen is pumped out of the reservoir tank, passes through pipe 6, exits the reservoir tank, and cools the liquid nitrogen.

Connected to the freezer.

In this case, the piping for pressurization is attached to the portion of the piping 6 coming out from the reservoir tank, and then returns to the reservoir tank through the same vaporizer 17 and valve 19 as in the first embodiment.

[0047] Example 3

In Example 1, the pressurizing means of the reservoir tank is only by gas from the pump outlet. In this case, the pipe is as thin as 6 mm and the pressure is divided by the pump discharge pressure. For this reason, it takes a very long time to reach a predetermined pressure with less gas supply. Especially when the reservoir tank is large, it takes tens of hours. Therefore, as shown in FIG. 4, as a supplementary means, an external pipe 21 is attached to the reservoir tank to supply gas to the high-pressure nitrogen cylinder 22 or nitrogen curdka. Further, when the gas phase portion inside the reservoir tank is cooled to a low temperature, the liquid is promoted. Therefore, the heater 23 may be disposed in the gas phase to suppress the liquid.

Industrial applicability

According to the present invention, the boiling point is lower than that of the liquid gas used for pressurization, and the gas dissolves in the liquid gas, causing instability in the circulation of the liquefied gas and troubles related to insulation of the electrical equipment. In addition, it is possible to provide a cooling system for superconducting power equipment that can circulate liquid gas in a subcooled state for a long period of time.

Claims

The scope of the claims

[1] A reservoir tank for storing liquid gas, a circulation pump, a heat exchanger for cooling the liquefied gas, and a circulation loop for circulating the liquid gas, and using the circulation pump A cooling system for superconducting power equipment that circulates in a subcooled state and cools the superconducting power equipment,

The reservoir tank further includes pressurizing means for pressurizing the reservoir tank with the same kind of gas as the liquid gas, and the liquid level of the reservoir tank that stores the liquid gas in a pressurized state is the return of the circulating liquid gas. Cooling system for superconducting power equipment, characterized in that it is positioned at least the depth of the pressurized gas + (plus) liquid level movement correction amount!

[2] The pressurizing means for pressurizing the reservoir tank with the same kind of gas as the liquid gas is pressurized by a predetermined pressure via a pressure regulating valve from a gas cylinder storing the same kind of gas as the liquefied gas at a high pressure. The cooling system for a superconducting power device according to claim 1, characterized in that it consists of

[3] The pressurizing means for pressurizing the reservoir tank with the same kind of gas as the liquid gas is a liquid tank that is supplied to the superconducting power device from the outlet of the circulation pump that sends the liquid gas in the reservoir tank force subcooled state. The superconducting power equipment according to claim 1, characterized in that the reservoir tank is pressurized using the discharge pressure of the circulating pump by a pipe branching off from a part of the gas and returning to the reservoir tank. Cooling system.

[4] The pressurizing means for pressurizing the reservoir tank with the same kind of gas as the liquid gas is a liquid tank that is supplied to the superconducting power device from the outlet of the circulation pump that sends the liquid gas in the reservoir tank force subcooled state. 4. The method according to claim 3, comprising a vaporizer for vaporizing liquefied gas and a pressure regulating valve for regulating pressure, which are provided in a pipe branched from a part of the gas and returned to the reservoir tank. Cooling system for superconducting power equipment.

[5] The auxiliary means of the pressurizing means is further provided, and the auxiliary means is configured to pressurize the same kind of gas as the liquefied gas by supplying a gas cylinder force. Or a cooling system for a superconducting power device according to claim 4.

[6] The apparatus further includes auxiliary means for the pressurizing means, and the auxiliary means arranges a heating device in the gas phase part of the reservoir tank to superheat and expand the gas in the gas phase part of the reservoir tank. The cooling system for a superconducting electric power device according to any one of claims 1 to 5, characterized by comprising: