CN1969158B - Cooling system for superconducting power equipment - Google Patents

Abstract

A cooling system for superconducting power equipment, comprising a storage tank for storing liquid gas, a circulation pump, a heat exchanger for cooling the liquid gas, and a circulation loop for circulating the liquefied gas, using the circulation pump to circulate the liquefied gas in a supercooled state , thereby cooling the superconducting power equipment, the cooling system of the superconducting power equipment is characterized in that it is further equipped with a pressurization mechanism, which pressurizes the storage tank with the same type of gas as the liquefied gas, and stores the liquefied gas in a pressurized state. The liquid level of the storage tank of the liquefied gas is located only higher than the outlet of the return line of the circulating liquefied gas, and at least the upper part of the melting depth of the pressurized gas + the correction amount of the liquid level movement.

Description

Cooling system for superconducting power equipment

technical field

The invention relates to a cooling system for cooling superconducting cables, superconducting bus lines, SMES, superconducting transformers, etc., which can be industrially utilized in a superconducting state by cooling with liquefied nitrogen such as liquid nitrogen, especially relates to a cooling system for cooling in a high-voltage state The superconducting power device that operates the device.

Background technique

As a kind of superconducting power device, a superconducting cable using nitrogen gas such as liquid nitrogen for cooling is taken as an example, and the prior art will be described with reference to FIG. 6 . As a cooling system for a superconducting cable, a structure described in JP-A-08-148044 is known. As shown in Figure 6, the existing cooling system is a system that repeats the following cycle: the liquefied gas in the supercooled state (the state in which the liquefied gas is cooled to a state lower than the saturation temperature of the liquefied gas) is cooled from the storage tank 101 through the pump 105 Pressurized, cooled by the heat exchanger 107 of the refrigerator 108, supplied to the cable 111, and returned to the storage tank 101 again.

When cooling a superconducting cable, if the circulating liquefied gas is in a gas-liquid mixed state, the pressure loss will increase, and the necessary amount of liquefied gas cannot be circulated stably. Therefore, it is necessary to prepare a large-scale circulation pump with a large capacity. In addition, since the superconducting cable adopts a very low-temperature electrical insulation method in which liquefied gas is impregnated into the insulator to maintain high electrical insulation performance, if air or air bubbles are mixed into the liquefied gas, there will be a problem that the electrical insulation performance will be significantly reduced .

Therefore, in the existing cooling system, in order to always maintain the liquefied gas in a supercooled state, it is circulated in a non-vaporized state. Gas hydrogen (H ₂ ) or helium (He) with a sufficiently low triple point of the liquefied gas makes the storage tank 101 reach a pressurized state and increases the boiling point of the liquefied gas so that the liquefied gas does not boil during circulation (that is, will not reach the state of gas-liquid mixing).

Patent Document 1: Japanese Unexamined Patent Application Publication No. 08-148044

As is known in the prior art: in a storage tank, when liquid nitrogen (for example, liquefied gas) is pressurized by gas helium (He) whose triple point is sufficiently lower than that of liquefied gas, a small amount of He gas is generated and dissolved into the liquid state. phenomenon in nitrogen. That is, helium (He) gas is well known as an inert gas, and it has been considered that it does not dissolve in liquid nitrogen. However, it has been clarified that He gas dissolves in liquid nitrogen in a small amount.

Although the amount dissolved in liquid nitrogen is very small, if the liquefied gas dissolved in He gas is circulated, for example, in the part where the piping is wide and the flow rate of the liquefied gas is slow, or from a storage tank by a valve, etc. In the portion where the pressure of the liquefied gas drops sharply after throttling, etc., the dissolved He gas cannot continue to be dissolved in the liquefied gas and becomes bubbles, and is mixed into the liquid nitrogen to form a gas-liquid mixed state.

In addition, it is known that, depending on the state of the installation and layout of superconducting cables or superconducting power equipment, when there is a part higher than the cooling system, the gas generated in this part remains in the upper part of the equipment, and finally the cooling system filled with liquid nitrogen In the piping, the circulation of liquid nitrogen cannot be continued.

It has been clarified by the experiments of the inventors that the above-mentioned phenomenon occurs over a very long period of several months. If the liquid nitrogen contains He gas, and the piping reaches a gas-liquid mixed state or the cooling piping is filled with a gas phase, the circulation of liquid nitrogen cannot be carried out smoothly. In addition, since He gas has very low withstand voltage characteristics compared to other liquefied petroleum gases, although liquid nitrogen originally has high insulation characteristics, the He gas contained in it will cause the insulation characteristics to decrease and cause insulation failure or insulation breakdown of superconducting power devices. .

As a countermeasure, it is conceivable to pressurize the storage tank with the same type of gas as liquefied gas, but since the liquid nitrogen stored in the storage tank is liquid nitrogen at a temperature below the boiling point, if the nitrogen used for pressurization is in the storage tank The nitrogen gas used for pressurization is cooled and liquefied when it comes into contact with liquid nitrogen below the boiling point. Therefore, there is the following problem: the pressure of pressurization decreases, and the pressure cannot be kept constant if the nitrogen gas is not continuously supplied from the gas cylinder all the time. As a result, the following problem occurs: a large amount of nitrogen is consumed, and a large amount of The introduction of heat of liquefaction into the cooling system causes an increased heat load.

Contents of the invention

An object of the present invention is to provide a cooling system for a superconducting power device in which a gas having a boiling point lower than that of the liquefied gas used for pressurization is dissolved in the liquefied gas without causing an instability factor for the circulation of the liquefied gas , or the failure of the insulation of electrical equipment, it can make the liquefied gas circulate smoothly for a long time in the supercooled state.

The inventors of the present invention conducted earnest research in order to solve the above-mentioned problems of the prior art. As a result, the storage tank is pressurized with the same type of gas as liquefied gas instead of helium (He) gas that has been conventionally used as a pressurized gas, and it is possible to eliminate the possibility of dissolving a small amount of He gas in liquid nitrogen. From this, it became clear that the problem that He gas becomes bubbles in the portion where the pressure of the liquefied gas drops rapidly and is mixed into the liquid nitrogen to form a gas-liquid mixed state makes it impossible to smoothly circulate the liquid nitrogen and deteriorates the insulating properties. deteriorating. Similarly, it has been clarified that the following problem can also be solved: if the height difference of the superconducting power equipment exceeds the specified value, the generated bubbles will stay in the upper part of the equipment, and then fill the cooling circuit, resulting in the problem that the liquid nitrogen cannot continue to circulate.

In addition, the liquid level of the storage tank storing the liquefied gas in a pressurized state is located only higher than the outlet of the return line of the circulating liquefied gas, at least the upper part of the depth of dissolution of the pressurized gas + the correction amount of the liquid level movement, thereby It was clarified that the problem that the nitrogen gas used for pressurization is liquefied and the pressure of pressurization decreases, and that the pressure cannot be maintained at a constant level unless the nitrogen gas is continuously supplied from the cylinder. Therefore, it is possible to solve the problem that a large amount of nitrogen gas is consumed, and at this time, a large amount of liquefied heat is introduced into the cooling system to cause an increase in heat load.

The present invention has been achieved based on the above research results. The first aspect of the cooling system for superconducting power equipment of the present invention is to include a storage tank for storing liquid gas, a circulation pump, a heat exchanger for cooling liquid gas, and a cycle for circulating liquefied gas. A cooling system for a superconducting power device that circulates the liquefied gas in a supercooled state using a circulation pump to thereby cool the superconducting power device, further comprising a pressurizing mechanism for the liquefied gas A gas of the same kind pressurizes a storage tank which is a sealed container with an outlet for a return line of circulating liquefied gas located at least below the level of the pressurized gas in the storage tank The position of the lower part of the melting depth+(plus) liquid level movement correction amount, the melting depth is at least 20cm.

A second aspect of the cooling system for superconducting power equipment according to the present invention is characterized in that the pressurizing mechanism for pressurizing the storage tank with the same type of gas as the liquefied gas is configured as follows: The cylinder of the gas of the same type as the liquefied gas is pressurized at a predetermined pressure via a pressure regulating valve.

A third aspect of the cooling system for a superconducting power device according to the present invention is characterized in that the pressurizing mechanism for pressurizing the storage tank with the same type of gas as the liquefied gas is configured as follows: The liquefied gas is sent from the outlet of the circulation pump of the storage tank, a part of the liquefied gas sent to the superconducting power device is branched and returned to the piping of the storage tank, and the storage tank is pressurized by the discharge pressure of the circulation pump.

A fourth aspect of the cooling system for a superconducting power device according to the present invention is characterized in that the pressurizing mechanism for pressurizing the storage tank with the same type of gas as the liquefied gas is composed of a vaporizer that vaporizes the liquefied gas and a pressure The gasifier and the pressure regulating valve are arranged at the outlet of the circulating pump that sends the supercooled liquefied gas from the storage tank to the outlet of the liquefied gas sent to the superconducting power equipment. A part of the piping that branches and returns to the storage tank.

A fifth aspect of the cooling system for superconducting power equipment according to the present invention is characterized in that it further includes an auxiliary mechanism for the pressurizing mechanism, and the auxiliary mechanism is configured as follows: pressurized gas.

A sixth aspect of the cooling system for a superconducting power device according to the present invention is characterized in that it further includes a heating device disposed in the gas phase portion of the storage tank, and the gas superheating volume of the gas phase portion of the storage tank is caused by the heating device. swell.

According to the present invention, it is possible to provide a cooling system for superconducting power equipment in which liquid nitrogen is smoothly circulated and has excellent insulation properties because the storage tank is pressurized with the same type of gas as liquefied gas, so that no air bubbles are mixed into the liquid nitrogen. . Furthermore, according to the present invention, it is possible to provide a cooling system for a superconducting power plant in which at least the solution of the pressurized gas is located above the outlet of the return line of the circulating liquefied gas because the liquid level of the storage tank storing the liquefied gas in a pressurized state is located The nitrogen gas used for pressurizing the storage tank will not be liquefied and the pressurizing pressure will not decrease.

Description of drawings

Fig. 1 is the diagram illustrating the method for pressurizing the storage tank by the circulation pump outlet pressure of the present invention;

Fig. 2 is a diagram for explaining the configuration of the cooling system of Embodiment 1 of the present invention;

Fig. 3 is a configuration diagram illustrating the vicinity of a storage tank according to Embodiment 2 of the present invention;

Fig. 4 is a configuration diagram illustrating the vicinity of a storage tank according to Embodiment 3 of the present invention;

Fig. 5 is a graph showing the relationship between the penetration depth [m] of the pressurized gas and the pressure decrease rate [%];

Fig. 6 is a diagram illustrating a conventional cooling system for a superconducting cable.

In the figure, 1-storage tank; 1b-container inside the storage tank; 2-liquid nitrogen level in the storage tank; 3-liquid intake port; 4, 6, 9-liquid nitrogen circulation piping on the discharge side; 5-circulation pump; 5a -circulating pump motor; 5b-long axis of circulating pump; 5c-radiating fin; 5e-vacuum vessel; 7-refrigerator heat exchanger; 8-refrigerating machine; 12-Exit of superconducting cable; 13-Liquid nitrogen circulation piping on the return side; 14-Nitrogen return piping in the storage tank; 15-Nitrogen return piping outlet; 16, 18, 20-Branch pipes for pressurization; 17-Vaporization 19-valve; 21-external piping for pressurization; 22-high pressure nitrogen cylinder; 23-heating rod inside the storage tank.

Detailed ways

The cooling system for a superconducting power device of the present invention will be described in detail with reference to the drawings.

The cooling system for superconducting power equipment of the present invention is equipped with: a storage tank for storing liquid gas, a circulation pump, a heat exchanger for cooling liquid gas, and a circulation circuit for circulating the liquefied gas, and the circulation pump is used to liquefy the liquid gas in a supercooled state. The cooling system of the superconducting power equipment for cooling the superconducting power equipment by gas circulation is characterized in that it further includes a pressurizing mechanism for pressurizing the storage tank with the same type of gas as the liquefied gas, and a mechanism for storing the liquefied gas in a pressurized state. The liquid level of the storage tank is located only higher than the outlet of the return line of the circulating liquefied gas, and at least the upper part of the penetration depth of the pressurized gas + the correction amount of the liquid level movement.

In the case where the liquid level of a storage tank storing liquefied gas in a pressurized state needs to be at least higher than the outlet of the return line of the circulating liquefied gas, at least the upper part of the penetration depth of the pressurized gas + liquid level movement correction amount, It will be explained below.

The relationship between the penetration depth of the pressurized gas and the pressure reduction rate is verified by experiments. Fig. 5 is a graph showing the relationship between the penetration depth [m] of the pressurized gas and the pressure decrease rate [%].

In FIG. 5 , the depth of pressurized gas dissolved from the liquid surface of the storage tank (that is, the depth of pressurized dissolution) and the decrease rate of the pressure in the storage tank based on liquefaction per hour are represented by the horizontal axis and the vertical axis, respectively. As the experimental conditions, a container with a diameter of 1 m and a height of 1 m was used as the internal volume of the storage tank, and the pressure was set at 0.3 MPa. As a result, as can be seen from Fig. 5, the rate of decrease in pressure is remarkably large until the penetration depth reaches 10 cm, and the gas-phase nitrogen gas used for pressurization condenses into a liquid before the penetration depth reaches approximately 20 cm, and the pressurized The reduction in pressure is still rapid. On the other hand, it can be seen that if the depth of dissolution is maintained at 20 cm or more, the reduction in pressure can be maintained at a small value of 1% or less. In fact, in addition to the penetration depth of the pressurized gas, the liquid level changes due to the influence of the temperature and pressure of the liquid nitrogen, so it is necessary to consider the liquid level movement correction amount.

Therefore, the liquid level of the storage tank storing the liquefied gas in a pressurized state needs to be at least higher than the outlet of the return line of the circulating liquefied gas, and at least the upper part of the depth of dissolution of the pressurized gas + the correction amount of the liquid level movement. Specifically, it is preferable that the penetration depth (20 cm) of the pressurized gas + the liquid level movement correction amount (30 cm) be 50 cm or more. The above case has little dependence on the shape of the container of the storage tank, and even if the size changes, the necessary depth is roughly the same. Therefore, in the system of the present application, as the container height of the storage tank, a height capable of securing a necessary depth (preferably 50 cm or more) is required.

As described above, the present invention provides that, in a system for cooling a superconducting power device with liquefied gas, a gas having a boiling point lower than that of the liquefied gas used for pressurization is dissolved in the liquefied gas without causing instability in circulation for the liquefied gas A cooling system that can circulate liquefied gas for a long time in a supercooled state due to permanent factors or insulation failures of electrical equipment.

The pressurizing means for pressurizing in the above-mentioned state is constituted by pressurizing the storage tank to a predetermined pressure with the same type of gas as the liquefied gas stored in the storage tank. In order to prevent the pressurized gas from being cooled and liquefied by the liquefied gas, the liquid level of the storage tank is at least 20 cm higher than the outlet of the return pipe of the circulation pump in the storage tank, preferably 50 cm or more.

In addition, as a pressurization mechanism, instead of a mechanism for pressurizing by a high-pressure gas cylinder, there is a mechanism for pressurizing by returning the outlet pressure of the circulation pump higher than the pressure of the storage tank to the storage tank. As a specific mechanism for using the pressure at the outlet of the circulation pump, there is a mechanism in which the outlet pipe of the circulation pump that draws and pressurizes the liquid from the storage tank and then sends the liquid to the superconducting power plant is branched, and the pressure from the outlet of the storage tank is branched. Part of the liquefied gas is separated by pressure, and the branched liquefied gas is vaporized using a vaporizer, and then returned to the storage tank through a pressure regulating valve that opens and closes according to the pressure used to maintain the pressure of the storage tank at a predetermined pressure. Can.

In order to explain the operation of the present invention, a case where liquid nitrogen is used as the liquefied gas will be described. The boiling point of liquid nitrogen at atmospheric pressure (1.013MPa) is 77K. When this liquid nitrogen is pressurized to 0.3 MPa, the boiling point of liquid nitrogen becomes 90K or more. Therefore, when the liquid nitrogen at 77K is pressurized to 0.3 MPa, the liquid nitrogen becomes a supercooled state without generation of bubbles. The liquid intake part of the circulation pump is located at the bottom of the storage tank, and is connected to the circulation pump by piping.

On the other hand, the piping for the return circulation is connected to the storage tank, but the position of the outlet of the piping is lower than the liquid level. The liquefied gas sent out by the circulating pump is returned to the storage tank after cooling the superconducting power equipment. At this time, since the outlet of the pipe is lower than the liquid level, the returned liquefied gas does not come into contact with the pressurized gas phase of the storage tank, but moves to the liquid nitrogen inlet of the circulation pump and circulates again.

In the present invention, since the position of the liquid surface is higher than the specified height (20cm) of the pipe outlet or the liquid intake port of the circulating pump (that is, a predetermined liquefied gas layer is provided), the supercooled parts respectively located at the pipe ports Cool the liquid nitrogen so that the temperature of the liquid nitrogen above it increases sequentially toward the liquid surface, and the temperature of the liquid nitrogen on the liquid surface becomes approximately the same as the boiling point temperature of 0.3MPa liquefied gas. Therefore, in the past, when pressurizing the storage tank with the same type of gas, the gas liquefied and the pressure dropped due to the lack of time to supply the gas. However, by installing the liquefied gas layer this time, it has been clarified that most of the gas will not be liquefied.

In the present invention, methods other than the method of pressurizing from a gas cylinder were also reconsidered as methods of pressurization. The method of pressurizing by its own pressure in the present invention will be described with reference to FIG. 1 . Initially, liquid nitrogen is pumped from the interior of the reservoir at atmospheric pressure (point a), and the liquid is then pumped out by a circulation pump. At the outlet of the circulation pump, liquid nitrogen flows at 50 L/min, and for the inlet, the liquid nitrogen is pressurized by 0.2 MPa (point b). The liquid nitrogen pressurized by branching from the outlet pipe when utilizing the pressure at the outlet is vaporized by the intermediate vaporizer into a gas and returned to the storage tank, thereby increasing the pressure of the storage tank. (arrow c).

Corresponding to this, the outlet pressure of the circulation pump also rises (arrow d), so that the storage tank can always be pressurized. If the pressure of the storage tank exceeds the upper limit set pressure (P2) (point e), the valve attached to the piping is closed, and the supply of gas to the storage tank is stopped. Then, inside the water storage tank, the nitrogen gas in the gas phase is refrigerated by the liquid nitrogen below the triple point of nitrogen gas, and the nitrogen gas in the gas phase is liquefied into liquid nitrogen. The reduction in pressure of the storage tank (arrow f) corresponds to the amount of the portion that is liquefied with a reduction in the volume of the gas. When the lower limit set pressure (P1) (point g) is reached, the valve is opened, and the pressure at the outlet of the circulating pump is used to supply nitrogen gas to the inside of the storage tank to pressurize the pressure of the storage tank.

Since the low-temperature nitrogen gas flows through the pipes, there is a possibility that the pipes or valves may freeze, and as a function of the vaporizer, the liquid nitrogen is nitrogenized and the temperature is raised to room temperature in order to prevent this. As the vaporizer, there are methods of winding a heating rod around the pipe, passing the pipe through water, etc., and attaching fins to the pipe to increase the temperature by exchanging heat with the outside air. In addition, the function of the valve has the effect that if the gas is only sent out from the piping branched from the pump, the pressure of the storage tank will continue to rise and may reach the design pressure of the storage tank. Therefore, if the pressure of the storage tank reaches the specified pressure Above, it will be in the closed state to stop the pressurization of the gas, and if it reaches the predetermined pressure or lower, it will be in the open state, pressurized and automatically maintained at a constant pressure.

In addition, when the capacity of the storage tank is large, since a large amount of nitrogen gas is required to pressurize to a predetermined pressure, it is necessary to separately prepare a nitrogen cylinder so that the pressure of the storage tank can also be pressurized to a predetermined pressure. In addition, a method of arranging a heating device such as a heating rod in the gas phase portion inside the storage tank to pressurize and expand the gas in the storage tank to pressurize can also be used.

Hereinafter, the present invention will be described in more detail through examples.

Example

Example 1

FIG. 2 is a diagram illustrating an embodiment of a cooling system for a superconducting power device of the present invention. Liquid nitrogen was used as the liquefied gas. Liquid nitrogen is stored in storage tank 1. The storage tank 1 has a double-layer container structure, and a heat insulating material is constructed between the double-layer containers to surround the inner container 1b, and is maintained in a vacuum state to reduce heat conduction. Also, storage tanks are airtight containers used to pressurize the interior.

A liquid intake port 3 connected to a circulation pump was provided at the bottom of the storage tank, and from there, a pipe 4 with a diameter of 3 cm was connected to an inlet of a circulation pump 5 . The circulation pump 5 is a vortex type rotary pump. The motor 5a for rotating the heat sink 5c and the heat sink are connected by a shaft 5b having a long axis of about 50 cm in order to suppress the inflow of heat due to conduction.

In addition, the heat sink itself is arranged inside the vacuum container 5e to suppress heat conduction from the outside. The rotary pump of the present invention has a rotational speed of 50 Hz, can flow a flow rate of 30 L/min as a flow rate of liquid nitrogen, and can obtain a discharge pressure of 0.2 MPa as a pressure difference between an inlet and an outlet. A pipe 6 with a diameter of 3 cm was connected from the outlet of the pump to the heat exchanger 7 of the refrigerator in front of it.

The freezer 8 is composed of a GM freezer or a Stirling freezer, etc., and the heat exchanger is connected with the cold head to cool the circulating liquid nitrogen to a low temperature. In the present invention, a Stirling freezer having a refrigerating capacity of 1 kW was used, and by passing 30 L/min of liquid nitrogen through a heat exchanger cooled by the freezer, it was possible to cool a substance at 77k to 74k at the inlet.

Liquid nitrogen cooled by a freezer was watertightly connected to the inlet 10 of the superconducting power device through a pipe 9 with a diameter of 3 cm. In the cooling system for cooling the superconducting cable 11 of the present embodiment, the superconducting cable is cooled by circulating liquid nitrogen refrigerated by a refrigerator in the superconducting cable. The temperature of the liquid nitrogen that cooled the superconducting cable rises, but since the raised temperature is below the boiling point, a supercooled state in which no bubbles are generated in the liquid nitrogen is maintained. Therefore, even for a superconducting cable of 500 m, the pressure loss is less than 0.1 MPa, which is small enough to allow stable flow of liquid nitrogen.

In addition, good electrical insulation can be maintained because liquid nitrogen without generating bubbles penetrates into the electrical insulation layer of the superconducting cable. The liquid nitrogen leaving the outlet 12 of the superconducting cable is returned to the storage tank 1 through the pipe 13, thereby forming a circulation loop. The storage tank 1, the circulation pump 2, the heat exchanger 3 of the refrigerator, the superconducting cable 4, and the nitrogen piping connecting these devices are all formed in a double-layer container structure using vacuum insulation in order to reduce the conduction heat from the outside.

Return piping 13 to the storage tank, ie piping 14 from the top to the bottom of the storage tank, returns liquid from the outlet 15 to the storage tank at the bottom of the storage tank.

In addition, the liquid intake port 3 connected with the circulation pump is also located at the bottom of the storage tank. During the circulation, nitrogen remains in the liquid nitrogen in the storage tank such that the liquid level 2 is at least 20 cm above the outlet 15 .

In the method of pressurizing the storage tank by the outlet pressure of the circulation pump in the present invention, the pipe 6 made of stainless steel with a diameter of 6 mm is branched from the pipe 6 at the outlet of the pump. The liquid nitrogen passing through the inside of the piping 16 leaves the vacuum container of the circulation pump, passes through the vaporizer 17, and changes from liquid nitrogen to nitrogen gas at room temperature.

As the vaporizer, in this example, a 6mm copper pipe was wound into a 6m coil shape inside the warm water container, and it was immersed in warm water to raise the temperature of the liquid nitrogen inside. As the vaporizer, in addition to this embodiment, for example, a method of winding a heating rod outside the coil to heat up the heating rod based on energization, or installing a cooling fin on the piping and heating by exchanging heat with the atmosphere can also be used. Any method such as a warm method can be used as long as it can convert the internal liquid into a gas at room temperature. A valve 19 having a pressure control function is attached to the pipe 18 leaving the vaporizer 17, and it allows the gas whose outlet pressure is below a predetermined pressure to flow, and blocks the gas above a predetermined pressure. The piping 20 which exits the valve 19 is attached to the upper part of a storage tank, and can pressurize a storage tank.

In addition, the pipes 18 and 20 after passing through the vaporizer 17 are not necessarily insulated because they are at room temperature. It is suitable for preventing frost from forming on the piping 16 and for aesthetics. In addition, if the valve 19 operates at low temperature, the position of the valve 19 and the vaporizer 17 can be switched, but the valve for low temperature is more expensive than the valve for normal temperature, and it is not an economically appropriate arrangement. Furthermore, as the present embodiment, the piping 16 for pressure separation is branched from the piping 6 of the pump outlet, but it may also be branched from the piping 9 of the outlet of the heat exchanger of the refrigerating machine from the inlet 10 of the superconducting equipment. , as long as it is a part higher than the pressure of the storage tank, no matter where it is separated from, the purpose of the present invention can be achieved. In this sense, the pump outlet does not only mean the vicinity of the pump outlet, but more downstream than the pump outlet. All in general.

Example 2

In Embodiment 1, the case where the circulation pump is located outside the storage tank has been described, but the present invention can also be implemented when the circulation pump is located inside the storage tank. Fig. 3 is a partial view showing another mode of the cooling system of the superconducting power device of the present invention. That is, FIG. 3 is a diagram showing a storage tank part in the extraction cooling system of the present embodiment for explanation. The cooling fin part 5c which sends out the liquid in the circulation pump 5 is located in the liquid in the storage tank, and the rotation of the motor 5a is transmitted by the long shaft 5b. Liquid nitrogen is drawn from the storage tank and leaves the storage tank through piping 6, which is connected to a freezer which cools the liquid nitrogen.

In this case, the piping for pressurization is attached to the portion of the piping 6 away from the storage tank, and then returns to the storage tank through the vaporizer 17 and the valve 19 in the same manner as in Example 1.

Example 3

In Embodiment 1, as the pressurization mechanism of the storage tank, only the mechanism based on the gas from the outlet of the pump is used. In this case, since the pipe is as thin as 6mm, the pressure is only part of the discharge pressure, so the gas supply is also reduced, and it takes a very long time to reach the specified pressure. In particular, when the storage tank is enlarged, tens of hours are required. Therefore, as shown in FIG. 4 , an external pipe 21 is attached to the storage tank as an auxiliary mechanism, and gas is supplied from a high-pressure nitrogen cylinder 22 or a nitrogen curdle. In addition, if the gas phase part inside the storage tank is cooled to a low temperature, liquefaction will be accelerated, so the heating rod 23 may be arranged in the gas phase part to suppress liquefaction.

According to the present invention, gas having a boiling point lower than that of the liquefied gas used for pressurization can be dissolved in the liquefied gas without causing instability factors for the circulation of the liquefied gas or failure of the insulation of electrical equipment, and can Cooling system for superconducting power equipment that circulates liquefied gas in a cold state for a long time.

Claims (4)

1. the cooling system of a superconducting power apparatus, the heat exchanger, and the closed circuit that circulates of the liquefied gas of supercooled state that possess the hold-up tank of storing liquefied gas, circulating pump, cooling fluid gasification, the liquefied gas cooling superconducting power apparatus that utilization circulates in described closed circuit, it is characterized in that

Possess pressing mechanism, this pressing mechanism is used with the congener gas of described liquefied gas described hold-up tank is pressurizeed,

Described hold-up tank is the airtight container of outlet of return line with liquefied gas of circulation,

The degree of depth+(adding) liquid level that dissolves in that the outlet of described return line is positioned at than the low at least gas-pressurized of liquid level of described hold-up tank moves the position of the bottom of revisal amount, and the described degree of depth of dissolving in is at least 20cm.

2. the cooling system of superconducting power apparatus according to claim 1 is characterized in that,

Also possesses by the gas bomb that stores with high pressure with the congener gas of described liquefied gas the mechanism of pressurizeing with authorized pressure via pressure-regulating valve with the described pressing mechanism that hold-up tank is pressurizeed with the congener gas of liquefied gas.

3. the cooling system of superconducting power apparatus according to claim 1 is characterized in that,

Possesses the described outlet of circulating pump of sending by hold-up tank from the liquefied gas of supercooled state with the described pressing mechanism that hold-up tank is pressurizeed with the congener gas of liquefied gas, be sent to superconducting power apparatus liquefied gas a part of branch and turn back to the pipe arrangement of hold-up tank and make the gasifier of LNG gasifaction and pressure is regulated the pressure-regulating valve of usefulness, described gasifier and pressure-regulating valve are located at this pipe arrangement.

4. the cooling system of superconducting power apparatus according to claim 1 is characterized in that,

Also have the heating apparatus that the gas phase at described hold-up tank partly disposes, and make the gas superheat volumetric expansion of hold-up tank gas phase portion by described heating apparatus.

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