CN106782995A - The jetting type high-temperature superconductor cooling device and method of a kind of pressure differential - Google Patents

Abstract

The invention discloses a jet-type high-temperature superconducting cooling device driven by differential pressure, which comprises a low-temperature liquid immersion tank, a superconducting current limiter soaked in the low-temperature liquid immersion tank, and connected to the low-temperature liquid through a first regulating valve The gas buffer tank in the low-pressure gas area on the upper layer of the immersion tank also includes: a low-temperature diversion pipe arranged in the low-temperature liquid immersion tank, and a plurality of jet guides facing the surface of the superconducting flow limiter are opened on the pipe body hole; a high-pressure supercooled liquid tank, communicated with the low-temperature diversion pipeline through a second regulating valve, and passing supercooled liquid into the low-temperature diversion pipeline so that the supercooled liquid generates a high-speed jet liquid at the jet diversion hole; The invention also discloses a jet-type high-temperature superconducting cooling method driven by differential pressure; the device and method of the invention can greatly improve the heat transfer characteristics of the surface of the superconducting current limiter, and accelerate the recooling of the superconducting current limiter effectively The rewarming time of the superconducting current limiter is greatly shortened.

Description

A jet-type high-temperature superconducting cooling device and method driven by pressure difference

technical field

The invention relates to the field of high-temperature superconducting cooling, in particular to a jet-type high-temperature superconducting cooling device and method driven by differential pressure.

Background technique

With the increasing scale of the transmission and distribution network, the degree of grid interconnection is getting higher and higher. The interconnection of the grid improves the transmission efficiency of the grid, but it also makes the short-circuit impedance of the grid smaller and smaller, and the short-circuit current level increases sharply. At present, the short-circuit current level of many power grids has exceeded or is about to exceed the range that the existing circuit breakers can handle, and there are great hidden dangers in the operation safety of the power grid. To solve the problem of excessive short-circuit current on the equipment, high-impedance transformers or current-limiting reactors are traditionally used, but the use of these equipment increases the transmission loss and weakens the voltage regulation ability of the grid. At the same time, the loss of the power grid and the cost of power grid construction are increased. The current limiter made of superconducting technology can break the dilemma faced by the traditional current limiter and improve the efficiency and feasibility of the current limiter. Superconducting materials have two unique properties not found in other materials, namely zero resistance characteristics and complete diamagnetism, making it possible to make ideal fault current limiting devices, namely superconducting current limiters.

For low-temperature superconductivity, due to the limitation of the working temperature of the superconducting material used, helium must be used as the low-temperature cooling medium. However, if low-temperature helium is used as the cooling medium, its economy will be seriously affected. With the emergence of high-temperature superconducting materials, high-temperature superconducting technology continues to develop and progress, and the application of superconducting technology has risen from the original liquid helium temperature range to the liquid nitrogen temperature range. The study of supercooled liquid nitrogen in high temperature superconductivity has become an important research direction of high temperature superconductivity technology. The unique properties of high-temperature superconducting materials must be reflected in a certain low-temperature environment, so the low-temperature cooling system for high-temperature superconducting materials is very critical. However, whether a sufficient low-temperature environment can be maintained and sufficient low-temperature refrigeration capacity can be provided in this low-temperature environment to balance the AC loss of high-temperature superconducting materials due to operation and heat leakage due to conduction and radiation of the system is related to high-temperature superconductivity. Whether the material can run and work normally and stably. The low temperature environment for the operation of the superconducting magnet system is mainly provided by three methods, namely, conduction cooling of the refrigerator, recondensation cooling and cryogenic liquid immersion cooling. The conduction cooling structure of the refrigerator is simple and there is no low-temperature liquid delivery supplement, but the cooling uniformity is poor and the pre-cooling time is long and accompanied by the vibration of the refrigerator; the liquid consumption of the recondensation cooling zero evaporation mode is small, and the magnet is not subject to mechanical vibration, but the structure is complicated and the cost is high; Low temperature liquid immersion cooling structure is simple, good temperature stability and no mechanical vibration, when the liquid consumption is large.

As for the submerged cooling structure using cryogenic liquid, the recooling process of the superconducting material after quenching takes a long time, and no good solution has been found so far. When the power system fails, the ideal working state of the superconducting current limiter changes, losing its superconductivity, that is, showing resistance. When the current passes through the superconducting current limiter, a huge amount of Joule heat will be generated on its surface, and the heat will be transferred to the liquid nitrogen, causing the liquid nitrogen to gasify violently, and a large part of the formed bubbles will cover the superconducting current limiter. The contact surface with liquid nitrogen causes a sharp increase in heat dissipation thermal resistance, which delays the recooling process of the superconducting current limiter.

The cryogenic cooling system of a traditional superconducting current limiter is shown in Figure 1. Its structure is simple, including a liquid nitrogen tank 1, a superconducting current limiter 2, an automatic opening and closing valve 3 and a nitrogen buffer tank 4. The superconducting current limiter 2 is completely submerged in the lower liquid nitrogen of the liquid nitrogen tank 1, and the upper low-pressure nitrogen area of the liquid nitrogen tank 1 is connected with the nitrogen buffer tank 4, and the liquid nitrogen tank 1 and the nitrogen buffer tank are controlled by the automatic opening and closing valve 3 4 connected state. When the superconducting current limiter 2 quenches, the short-circuit current passes through the superconducting current limiter, generating a large amount of Joule heat, which is transferred to the liquid nitrogen, causing the liquid nitrogen to gasify violently, and the automatic opening and closing valve 3 opens quickly, and the superconducting limiter Part of the bubbles generated on the surface of the flow limiter 2 rises to the upper nitrogen area, and enters the nitrogen buffer tank 4 driven by the pressure difference, while the bubbles remaining on the surface of the superconducting flow limiter 2 can only be discharged naturally, and then the liquid nitrogen can flow back The liquid nitrogen tank 1 cools it down, causing the superconducting current limiter 2 to reheat and restart seriously lagging behind.

Contents of the invention

The invention provides a jet-type high-temperature superconducting cooling device driven by pressure difference, which effectively solves the problem of rapid recooling of high-heat-capacity superconducting materials at the quenching instant of a superconducting current limiter.

A jet-type high-temperature superconducting cooling device driven by pressure difference, comprising a low-temperature liquid immersion tank, a superconducting flow limiter immersed in the low-temperature liquid immersion tank, connected to the upper layer of the low-temperature liquid immersion tank through a first regulating valve Gas buffer tanks for low-pressure gas areas, also including:

A low-temperature diversion pipe arranged in the low-temperature liquid immersion tank, and a plurality of jet diversion holes facing the surface of the superconducting current limiter are opened on the pipe body;

A high-pressure supercooled liquid tank, the internal pressure of which is greater than that of the low-temperature liquid soaking tank, is communicated with the low-temperature diversion pipe through a second regulating valve, and the supercooled liquid is passed into the low-temperature diversion pipe so that the supercooled liquid A high-speed jet liquid is generated at the orifice, which breaks the bubble layer on the surface of the superconducting flow limiter due to the gasification of the liquid and accelerates the discharge of the bubbles into the gas buffer tank.

The present invention combines high-efficiency insulation methods, such as stack insulation, vacuum powder insulation or high-vacuum multi-layer insulation, to achieve good insulation performance.

The device of the present invention is suitable for a low-temperature liquid immersion cooling system. Preferably, the low-temperature liquid in the low-temperature liquid immersion tank is liquid nitrogen, liquid helium or liquid neon.

The following uses liquid nitrogen for illustration. The low-temperature liquid soaking tank is a liquid nitrogen tank, the gas buffer tank is a nitrogen buffer tank, and the high-pressure supercooled liquid tank is a high-pressure supercooled liquid nitrogen tank.

There are two arrangements of high-pressure supercooled liquid nitrogen tanks: when the high-pressure supercooled liquid nitrogen tank is arranged in parallel with the liquid nitrogen tank, the pressure of liquid nitrogen stored in the high-pressure supercooled liquid nitrogen tank is much higher than the pressure of liquid nitrogen in the liquid nitrogen tank; The high-pressure supercooled liquid nitrogen tank is located at the top of the liquid nitrogen tank, and can provide a certain pressure difference through the top potential energy of the high-pressure supercooled liquid nitrogen tank.

In order to better disperse the bubble layer, preferably, the low-temperature diversion pipe passes through the central region of the superconducting restrictor.

In order to better disperse the bubble layer, preferably, the jet guide holes are uniformly arranged along the circumference of the pipe area of the low temperature guide pipe close to the superconducting restrictor. There are single-row arrangement and multi-row arrangement in the arrangement of the jet diversion holes, and the shape of the diversion holes can be in different forms such as circle, ellipse or rectangle.

In order to better disperse the bubble layer, preferably, the superconducting current limiter is in the shape of a disk, and there are multiple vertical ones arranged separately.

Preferably, the jet guide hole is an oblique cut hole, and the inclination angle relative to the axis of the low temperature guide pipe is 30°-60°. The liquid nitrogen jet impinges on the surface of the superconducting current limiter, accelerating the disturbance of the bubble layer on the wall, and at the same time forming a stagnation point on the surface of the current limiter, where the thermal stress is relatively large. high demands.

Preferably, the first regulating valve and the second regulating valve are automatic opening and closing valves. The fast-response automatic opening and closing valve in the gas phase area and the automatic opening and closing valve in the liquid phase area are used to control the communication status of the low-temperature liquid immersion tank and the gas buffer tank, and the low-temperature liquid immersion tank and the high-pressure supercooled liquid tank respectively.

Preferably, both ends of the low-temperature diversion pipeline are connected to the same pipeline, which is provided with the second regulating valve and connected to a high-pressure subcooled liquid tank.

The present invention also provides a jet-type high-temperature superconducting cooling method driven by pressure difference. Using the above-mentioned jet-type high-temperature superconducting cooling device driven by pressure difference, when the superconducting current limiter quenches, the first regulating valve and the second regulating valve is opened, the supercooled liquid in the high-pressure supercooled liquid tank enters the low-temperature liquid soaking tank through the low-temperature diversion pipe driven by the pressure difference, and a high-speed jet liquid is generated at the jet diversion hole, Crush the bubble layer on the surface of the superconducting current limiter, accelerate the shedding of the bubbles and discharge them into the nitrogen buffer tank.

Beneficial effects of the present invention:

(1) Using the supercooled liquid nitrogen jet cooling technology driven by pressure difference, in the event of a short circuit fault, a high-speed jet of liquid nitrogen is generated at the jet diversion hole, crushing the bubble layer on the surface of the restrictor and accelerating the discharge of the bubbles.

(2) When a short-circuit fault occurs, after the superconducting current limiter loses its superconductivity, the fluid velocity field on the surface of the superconducting current limiter will change by generating a liquid jet, and the liquid in the supercooled state will accelerate the superconducting current limiter surface The flow rate of the fluid greatly improves the heat transfer characteristics of the surface of the superconducting current limiter, and accelerates the recooling process of the superconducting current limiter.

(3) When a short-circuit fault occurs, the superconducting current limiter loses its superconductivity, and a large amount of liquid nitrogen will be consumed due to liquid vaporization. By generating liquid jets, supercooled liquid is added to the liquid nitrogen tank, which is beneficial to superconductivity Continuous cooling process of the restrictor.

Description of drawings

FIG. 1 is a structural schematic diagram of a conventional cryogenic cooling system for a superconducting current limiter.

Fig. 2 is a structural schematic diagram of the jet-type high-temperature superconducting cooling device driven by pressure difference of the present invention.

Fig. 3 is a schematic structural view of a part of the low-temperature diversion pipeline of the present invention.

in:

1. Liquid nitrogen tank, 2. Superconducting current limiter, 3. Automatic opening and closing valve in gas phase area, 4. Nitrogen buffer tank, 5. Low temperature diversion pipe, 6. Jet diversion hole, 7. High pressure supercooled liquid nitrogen Tank, 8. Automatic opening and closing valve in the liquid phase area.

detailed description

This embodiment takes liquid nitrogen as an example for illustration. As shown in FIG. The low temperature diversion pipe 5 of the hole 6, the automatic opening and closing valve 3 of the gas phase area, the automatic opening and closing valve 8 of the liquid phase area, the nitrogen buffer tank 4 and the high pressure supercooled liquid nitrogen tank 7.

The superconducting current limiter 2 is completely submerged in the liquid nitrogen at the lower part of the liquid nitrogen tank 1, and the upper high-pressure nitrogen zone is connected with the nitrogen buffer tank 4 through pipelines. The low-temperature diversion pipe 5 passes through the central area of the superconducting flow limiter 2, and the pipeline area connected to the superconducting flow limiter 2 is provided with jet diversion holes 6, and the jet diversion holes 6 are provided with multiple and uniform along the circumferential direction. distribution, the jet guide hole 6 is an oblique cut hole, and the angle θ=45°, as shown in FIG. 3 .

The low-temperature diversion pipe 5 connects the liquid nitrogen tank 1 and the high-pressure supercooled liquid nitrogen tank 7 . The fast-response automatic opening and closing valve 3 in the gas phase area and the automatic opening and closing valve 8 in the liquid phase area are used to control the communication status of the liquid nitrogen tank 1 and the nitrogen buffer tank 4, and the connection between the liquid nitrogen tank 1 and the high-pressure supercooled liquid nitrogen tank 7.

When the superconducting current limiter 2 is working normally, the two automatic opening and closing valves controlling the liquid nitrogen tank 1 and the nitrogen buffer tank 4, the liquid nitrogen tank 1 and the high-pressure supercooled liquid nitrogen tank 7 are in the closed state, and the low-temperature diversion pipe 5 Filled with liquid nitrogen in the same state as in the liquid nitrogen tank 1, the whole system is in a state of dynamic equilibrium.

When a short-circuit fault occurs, the ideal working state of the superconducting current limiter 2 changes and loses its superconductivity, that is, it presents resistance. As a result, the huge amount of Joule heat generated on the surface of the superconducting current limiter 2 is transferred to the liquid nitrogen, causing the liquid nitrogen to gasify violently. Part of the formed bubbles rise to the upper high-pressure nitrogen area, and some of the bubbles cover the superconducting current limiter. The surface of device 2 makes its heat dissipation thermal resistance increase sharply. The two automatic opening and closing valves controlling the liquid nitrogen tank 1 and the nitrogen buffer tank 4, the liquid nitrogen tank 1 and the high-pressure supercooled liquid nitrogen tank 7 are quickly switched to the open state by using their fast response characteristics.

Now, the liquid nitrogen enters the upper space of the liquid nitrogen tank 1 due to the bubbles generated by gasification, and forms a high-pressure nitrogen zone rapidly in the upper space of the liquid nitrogen tank 1, so that the low-pressure nitrogen in the nitrogen buffer tank 4 and the liquid nitrogen tank 1 upper space The high-pressure nitrogen generates a certain pressure difference, and the nitrogen gas in the upper space of the liquid nitrogen tank 1 enters the nitrogen buffer tank 4 driven by the pressure difference.

The high-pressure supercooled liquid nitrogen in the high-pressure supercooled liquid nitrogen tank 7 passes through the low-temperature diversion pipe 5 driven by the pressure difference, and enters the liquid nitrogen tank 1 at both ends. At the jet diversion hole 6, due to the sudden reduction of the cross-sectional area, High-speed jet flow is generated, and the high-speed, high-pressure supercooled liquid nitrogen smashes the bubble layer on the surface of the superconducting current limiter 2 due to gasification, accelerates the bubbles to fall off and discharges to the upper space of the liquid nitrogen tank 1 . Liquid nitrogen in a high-pressure, high-speed supercooled state changes the velocity field on the surface of the superconducting current limiter and accelerates the flow velocity of the fluid on the surface of the superconducting current limiter. This forced convection can greatly improve the heat transfer characteristics of the surface of the superconducting current limiter and accelerate Recooling process of a superconducting current limiter. Due to the vaporization of liquid nitrogen, the amount of liquid nitrogen in the liquid nitrogen tank 1 decreases sharply. The liquid nitrogen jet in the high-pressure supercooled liquid nitrogen tank 7 enters the liquid nitrogen tank 1 , and supercooled liquid nitrogen is added to the liquid nitrogen tank 1 , which is beneficial to the continuous cooling of the superconducting current limiter 2 .

To sum up, the jet-type high-temperature superconducting cooling device driven by pressure difference in this embodiment uses the supercooled liquid nitrogen jet cooling technology driven by pressure difference. When a short-circuit fault occurs, a high-speed jet of liquid nitrogen is generated at the jet guide hole, Break the bubble layer on the surface of the current limiter and accelerate the discharge of the bubbles; in the case of a short circuit fault, after the superconducting current limiter loses its superconductivity, the liquid nitrogen jet is generated to cause the change of the fluid velocity field on the surface of the superconducting current limiter. The liquid nitrogen in the supercooled state accelerates the flow velocity of the surface fluid of the superconducting current limiter, greatly improves the heat transfer characteristics of the surface of the superconducting current limiter, and accelerates the recooling process of the superconducting current limiter; The flow limiter loses its superconductivity, and a large amount of liquid nitrogen will be consumed due to the gasification of liquid nitrogen; through the generation of liquid nitrogen jets, supercooled liquid nitrogen is added to the liquid nitrogen tank, which is beneficial to the continuous cooling process of the superconducting flow limiter; through The jet cooling technology generated by pressure difference is not only suitable for liquid nitrogen immersion, but also suitable for other low-temperature liquid immersion cooling systems, such as liquid helium immersion and liquid neon immersion.

Claims (9)

1. A jet-type high-temperature superconducting cooling device driven by differential pressure, comprising a low-temperature liquid immersion tank, a superconducting current limiter immersed in the low-temperature liquid immersion tank, connected to the low-temperature liquid immersion tank by a first regulating valve The gas buffer tank of the upper low-pressure gas area is characterized in that it also includes: A low-temperature diversion pipe arranged in the low-temperature liquid immersion tank, and a plurality of jet diversion holes facing the surface of the superconducting current limiter are opened on the pipe body; A high-pressure supercooled liquid tank, the internal pressure of which is greater than that of the low-temperature liquid soaking tank, is communicated with the low-temperature diversion pipe through a second regulating valve, and the supercooled liquid is passed into the low-temperature diversion pipe so that the supercooled liquid A high-speed jet liquid is generated at the orifice, crushing the bubble layer on the surface of the superconducting flow limiter due to cooling, and accelerating the discharge of the bubbles into the gas buffer tank. 2 . The jet-type high-temperature superconducting cooling device driven by pressure difference according to claim 1 , wherein the cryogenic liquid in the cryogenic liquid immersion tank is liquid nitrogen, liquid helium or liquid neon. 3 . The jet-type high-temperature superconducting cooling device driven by pressure difference according to claim 1 , wherein the low-temperature conduction pipe passes through the central area of the superconducting flow limiter. 4 . 4. the jet type high-temperature superconducting cooling device driven by differential pressure as claimed in claim 3, is characterized in that, described low-temperature conduction pipeline is arranged evenly along the circumferential direction by a certain amount near the pipeline area of the superconducting flow limiter. The jet guide hole described above. 5 . The jet-type high-temperature superconducting cooling device driven by pressure difference as claimed in claim 4 , wherein the superconducting current limiter is disk-shaped, and there are a plurality of them erected and arranged separately. 6 . 6. The jet-type high-temperature superconducting cooling device driven by differential pressure as claimed in claim 1 or 5, wherein the jet diversion hole is an oblique cut hole, and the inclination relative to the axis of the low-temperature diversion pipeline The angle is 30°～60°. 7. The differential-pressure-driven jet-type high-temperature superconducting cooling device according to claim 4, wherein the first regulating valve and the second regulating valve are automatic opening and closing valves. 8. The jet-type high-temperature superconducting cooling device driven by differential pressure as claimed in claim 1, wherein the two ends of the low-temperature guiding pipeline are connected to the same pipeline, and the pipeline is provided with the second adjustment valve and connect to the high pressure subcooled liquid tank. 9. A jet-type high-temperature superconducting cooling method driven by differential pressure, characterized in that, using the jet-type high-temperature superconducting cooling device driven by differential pressure as claimed in any one of claims 1 to 8, when the superconducting When the guide flow limiter fails, the first regulating valve and the second regulating valve are opened, and the supercooled liquid in the high-pressure supercooled liquid tank is driven by the pressure difference into the low-temperature liquid soaking tank through the low-temperature diversion pipe, The high-speed jet liquid is generated at the jet diversion hole, the bubble layer on the surface of the superconducting flow limiter is broken, and the bubbles are accelerated to fall off and discharged into the nitrogen buffer tank.