CN106847464A - The forced convertion high-temperature superconductor cooling device and method of a kind of pressure differential - Google Patents

Abstract

The invention discloses a forced convection high-temperature superconducting cooling device driven by pressure difference, which includes a low-temperature liquid immersion tank and a superconducting current limiter immersed in the low-temperature liquid immersion tank, and also includes: a low-temperature flow guide pipe arranged in the low-temperature liquid immersion tank In the low-temperature liquid immersion tank, the pipe body is provided with a plurality of diversion holes facing the surface of the superconducting current limiter; the low-pressure balance tank communicates with the low-temperature diversion pipe through a regulating valve, and is used for limiting the current. When the device loses superconductivity, the regulating valve is opened so that the liquid nitrogen in the low-temperature liquid immersion tank enters the low-pressure balance tank through the low-temperature diversion pipe, so that forced convection occurs on the surface of the superconducting restrictor near the diversion hole; The cryopump is used to pump the supercooled liquid in the low-pressure balance tank back to the cryogenic liquid immersion tank; the present invention also discloses a forced convection high-temperature superconducting cooling method driven by pressure difference; the device and method of the present invention The heat transfer characteristic of the surface of the superconducting current limiting unit can be greatly improved, and the recooling process of the superconducting current limiting unit can be accelerated.

Description

A pressure difference driven forced convection high temperature superconducting cooling device and method

technical field

The invention relates to the technical field of high-temperature superconducting cooling, in particular to a pressure-difference-driven forced convection high-temperature superconducting cooling device and method.

Background technique

With the increasing demand for electricity and the continuous improvement of power supply quality requirements, the scale of the transmission and distribution network is gradually expanding. While improving the transmission efficiency of the power grid, it also makes the short-circuit impedance of the power grid smaller and smaller, and the short-circuit current increases sharply. To solve the problem of excessive short-circuit current on the equipment, high-impedance transformers or current-limiting reactors are 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. Existing research and practice show that it is difficult to realize an ideal restrictor based on traditional materials and technologies. 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.

With the advent of high-temperature superconducting materials, the application of superconducting technology has risen from the original liquid helium temperature range to the liquid nitrogen temperature range. As one of the research hotspots of high-temperature superconductivity, the research of supercooled liquid nitrogen in high-temperature superconductivity has become an important research direction of high-temperature superconductivity technology. The working temperature of high-temperature superconducting materials must be maintained at a certain low temperature environment, so that superconducting materials can show unique properties, so the low-temperature cooling system of high-temperature superconducting materials is very critical. However, whether a sufficient low-temperature environment can be obtained and there is sufficient low-temperature cooling capacity in this low-temperature environment to balance the conduction and radiation heat leakage of the system and the AC loss of high-temperature superconducting materials due to operation is related to high-temperature superconducting materials. Whether it can run and work normally and stably.

At present, the low-temperature environment for superconducting magnet system operation is mainly provided by three methods, namely, cryogenic liquid immersion cooling, recondensation cooling, and cryocooler conduction cooling. The low-temperature liquid immersion cooling structure is simple, the temperature stability is good, and there is no mechanical vibration, but the liquid consumption is large; the recondensation cooling zero evaporation mode has a small liquid consumption, and the magnet is not subject to mechanical vibration, but the structure is complicated and the cost is high; the conduction cooling of the refrigerator has a simple structure 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 research on high temperature superconducting materials cooled by liquid nitrogen has been mature day by day. As for the lengthy recooling process of superconducting materials after quenching, 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 surface of the superconducting current limiter. On the surface, the heat dissipation thermal resistance increases sharply, 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, and its structure is relatively 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 liquid nitrogen in the liquid nitrogen tank 1, 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 4 are controlled by the automatic opening and closing valve 3 connected state.

When a short-circuit fault occurs in the equipment, the superconducting current limiter 2 quenches, and the automatic opening and closing valve 3 opens quickly, and part of the bubbles generated on the surface of the superconducting current limiter 2 rises to the upper nitrogen low-pressure area, and enters the nitrogen buffer tank driven by the pressure difference 4. The bubbles attached to the surface of the superconducting current limiter 2 can only be discharged naturally, and then the liquid nitrogen can flow back to the liquid nitrogen tank 1 to cool it down, resulting in a serious delay in rewarming and restarting the superconducting current limiter 2.

Contents of the invention

The invention provides a forced convection high-temperature superconducting cooling device driven by pressure difference, which can solve the problem of rapid recooling of superconducting materials with high heat capacity at the moment of quenching of superconducting current limiters.

A forced convection high-temperature superconducting cooling device driven by pressure difference, comprising a low-temperature liquid immersion tank and a superconducting current limiter immersed in the low-temperature liquid immersion tank, and further comprising:

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

A low-pressure balance tank, the internal pressure of which is lower than that of the low-temperature liquid immersion tank, is communicated with the low-temperature diversion pipe through a regulating valve, and is used to open the regulating valve when the flow limiter loses superconductivity so that the liquid in the low-temperature liquid immersion tank The low-temperature liquid enters the low-pressure balance tank through the low-temperature diversion pipe, causing forced convection on the surface of the superconducting restrictor near the diversion hole;

The cryogenic pump is used to pump the subcooled liquid in the low-pressure balance tank back to the cryogenic liquid immersion tank.

The invention greatly improves the heat transfer characteristics of the surface of the current limiter through the forced convection formed on the surface of the superconducting current limiter, thereby realizing rapid cooling of the surface of the current limiter.

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, and the cryogenic liquid immersion tank is a liquid nitrogen tank. There are two arrangements of the low-pressure balance tank: when the low-pressure balance tank is arranged in parallel with the liquid nitrogen tank, the pressure in the low-pressure balance tank is much lower than the pressure in the liquid nitrogen tank; when the low-pressure balance tank is located at the bottom of the liquid nitrogen tank, it can be With the help of the top potential energy of the liquid nitrogen tank, a certain pressure difference is provided through the top potential energy.

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 pipe area of the low-temperature diversion pipe close to the superconducting restrictor is uniformly provided with the diversion holes along the circumference. All bubble layers on the surface of the superconducting current limiter are disturbed by forced convection.

There are single-row arrangement and multi-row arrangement for the arrangement of the diversion holes, and the shapes of the diversion holes can be 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.

There is a certain angle θ in the guiding position of the diversion hole. When the diversion hole and the low-temperature diversion pipe are vertically arranged at θ=90°, the cryogenic liquid sweeps across the surface of the superconducting current limiter and enters the diversion hole; when the diversion hole is offset by a certain angle 0<θ<90°, the superconducting current limiting The velocity field on the surface of the container changes drastically, and the acceleration disturbs the bubble layer on the wall. Preferably, the diversion hole is an oblique hole, and the inclination angle relative to the axis of the low-temperature diversion pipe is 30°-60°.

Preferably, the regulating valve is an automatic opening and closing valve. The fast-response automatic opening and closing valve is selected to accurately and timely change the connection state of the low-temperature liquid immersion tank and the low-pressure balance tank.

In order to make the convection more uniform and the response faster, preferably, both ends of the low-temperature diversion pipe are connected to the same pipeline, which is provided with the regulating valve and connected to the liquid inlet of the low-pressure balance tank.

The present invention also provides a forced convection high temperature superconducting cooling method driven by pressure difference, which is characterized in that using the above pressure difference driven forced convection high temperature superconducting cooling device includes the following steps:

(1) When a short-circuit fault occurs, the superconducting current limiter loses its superconductivity, the surface of the superconducting current limiter vaporizes the low-temperature liquid, and a part of the formed bubbles rises to the upper space of the low-temperature liquid immersion tank A high-pressure gas zone is formed, a part of the bubbles cover the surface of the superconducting restrictor, and the regulating valve is opened;

(2) The cryogenic liquid in the cryogenic liquid immersion tank is driven by the pressure difference, and the cryogenic liquid enters the low-pressure balance tank through the diversion hole through the low-temperature diversion pipe; at the diversion hole, due to the reduction of the cross-sectional area, Under the action of pressure difference, forced convection is formed on the surface of the superconducting current limiter, which intensifies the disturbance of the bubble layer on the surface of the superconducting current limiter, accelerates the shedding of the bubbles and rises to the upper space of the low-temperature liquid immersion tank; Forced convection, changing the velocity field of the fluid on the surface of the superconducting current-limiting unit, accelerating the flow velocity of the fluid on the surface of the superconducting current-limiting unit, greatly improving the heat transfer characteristics of the surface of the superconducting current-limiting unit, and accelerating the recooling process of the superconducting current-limiting unit .

(3) After the reheating stage of the superconducting current limiter is completed, the cryogenic pump is used to replenish the cryogenic liquid in the low-pressure balance tank to the cryogenic liquid soaking tank, so as to realize the recycling of the cryogenic liquid.

Beneficial effects of the present invention:

(1) The present invention proposes a new high-temperature superconducting cooling technology, and innovatively proposes a forced convection cooling technology driven by pressure difference. When a short-circuit fault occurs, forced convection is generated on the surface of the superconducting current limiter through the pressure difference to aggravate the disturbance The bubble layer on the surface of the superconducting current limiter accelerates the shedding and discharge of bubbles.

(2) The present invention proposes a new high-temperature superconducting cooling technology. When a short-circuit fault occurs, after the superconducting current limiter loses its superconductivity, the forced convection generated by the pressure difference increases the surface fluid velocity of the superconducting current limiting unit, which is extremely The heat transfer characteristics of the surface of the superconducting current limiting unit are greatly improved, and the recooling process of the superconducting current limiting unit is accelerated.

(3) The present invention proposes a new high-temperature superconducting cooling technology. When a short-circuit fault occurs, after the superconducting current limiter loses its superconductivity, the low-temperature liquid in the low-pressure balance tank is replenished to the low-temperature liquid soaking tank by using a cryogenic pump , to realize the recycling of cryogenic liquid.

Description of drawings

Fig. 1 is a structural schematic diagram of a cryogenic cooling system of a superconducting current limiter in the prior art.

Fig. 2 is a structural schematic diagram of the differential pressure driven forced convection high temperature superconducting cooling device of the present invention.

Fig. 3 is a schematic diagram of a partial structure of a superconducting current limiter.

Among them: 1. Liquid nitrogen tank, 2. Superconducting current limiter, 3. Automatic opening and closing valve, 4. Nitrogen buffer tank, 5. Low temperature diversion pipe, 6. Diversion hole, 7. Low pressure balance tank, 8. cryopump.

detailed description

This embodiment takes liquid nitrogen as an example for illustration. As shown in FIG. 6 low temperature diversion pipeline 5, automatic opening and closing valve 3, low pressure balance tank 7 and cryogenic pump 8.

The superconducting current limiter 2 is completely submerged in the lower part of the liquid nitrogen tank 1, and the upper part is a high-pressure nitrogen gas zone. The low-temperature diversion pipe 5 passes through the central area of the superconducting current limiter 2, and the pipe area connected to the superconducting current limiter 2 is provided with diversion holes 6, and multiple diversion holes 6 are arranged and evenly distributed along the circumference, The diversion hole 6 is a chamfered hole with an angle θ=45°, as shown in FIG. 3 .

The low-temperature diversion pipe 5 connects the liquid nitrogen tank 1 and the low-pressure balance tank 7 . A fast-response automatic opening and closing valve 3 is used to control the communication state between the liquid nitrogen tank 1 and the low-pressure balance tank 7 . A pipeline is bypassed between the low-pressure balance tank 7 and the liquid nitrogen tank 1, and the cryopump 8 realizes the recovery and use of liquid nitrogen.

When the superconducting current limiter 2 is working normally, the automatic opening and closing valve 3 controlling the liquid nitrogen tank 1 and the low-pressure balance tank 7 is in a closed state, and the low-temperature diversion pipe 5 is filled with liquid nitrogen in the same state as that in the liquid nitrogen tank 1. The 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, a huge amount of Joule heat is generated on the surface of the superconducting current limiter 2, and the heat is transferred to the liquid nitrogen, and the liquid nitrogen is violently vaporized, and part of the formed bubbles rise to the upper space of the liquid nitrogen tank 1 to form a high-pressure nitrogen gas zone, and a part of the bubbles cover On the surface of the superconducting current limiter 2, its heat dissipation thermal resistance increases sharply. The automatic opening and closing valve 3 controlling the liquid nitrogen tank 1 and the low-pressure balance tank 7 is quickly switched to the open state by utilizing its fast response characteristics.

The liquid nitrogen enters the upper space of the liquid nitrogen tank 1 due to the bubbles generated by gasification, and a high-pressure nitrogen gas zone is rapidly formed in the upper space of the liquid nitrogen tank 1, while the liquid nitrogen in the liquid nitrogen tank 1 and the liquid nitrogen in the low-pressure balance tank 7 have a certain degree of existence. Pressure difference, driven by the above-mentioned pressure difference, the liquid nitrogen in the liquid nitrogen tank 1 passes through the diversion hole 6, and flows out of the liquid nitrogen tank 1 through the two ends of the low-temperature diversion pipe 5, and finally enters the low-pressure balance tank 7 after confluence. And at the diversion hole 6, due to the reduction of the cross-sectional area, forced convection is formed on the surface of the superconducting current limiter 2 under the action of the pressure difference, which aggravates the disturbance of the bubble layer on the surface of the superconducting current limiter 2, accelerates the shedding of the bubbles and rises to Liquid nitrogen tank 1 upper space. The forced convection generated by the pressure difference changes the velocity field of the fluid on the surface of the superconducting current-limiting unit, accelerates the flow velocity of the fluid on the surface of the superconducting current-limiting unit, greatly improves the heat transfer characteristics of the surface of the superconducting current-limiting unit, and accelerates the superconducting current-limiting unit surface. Flow cell recooling process.

Due to the vaporization of the liquid nitrogen, a large amount of liquid nitrogen in the liquid nitrogen tank 1 is consumed. After the reheating stage of the superconducting current limiter 2 is completed, the liquid nitrogen in the low-pressure balance tank 7 is replenished into the liquid nitrogen tank 1 by using the cryopump 8 to realize the recycling of liquid nitrogen.

In summary, the differential pressure-driven forced convection high-temperature superconducting cooling device of this embodiment utilizes the differential pressure-driven forced convection cooling technology to generate forced convection on the surface of the superconducting current limiter 2 through the action of the differential pressure in the event of a short-circuit fault. , aggravate the disturbance of the bubble layer on the surface of the superconducting current limiter 2, and accelerate the shedding and discharge of the bubbles; in the case of a short-circuit fault, after the superconducting current limiter 2 loses its superconductivity, the forced convection generated by the pressure difference increases the superconductivity The fluid velocity on the surface of the current limiting unit greatly improves the heat transfer characteristics on the surface of the superconducting current limiter 2 and accelerates the recooling process of the superconducting current limiter 2; at the same time, the liquid nitrogen in the low-pressure balance tank 7 is replenished by using the cryopump 8 into the liquid nitrogen tank 1 to realize the recycling of liquid nitrogen.

Claims (9)

1. a kind of forced convertion high-temperature superconductor cooling device of pressure differential, including cryogenic liquid soaking compartment and it is immersed in described Superconductive current limiter in cryogenic liquid soaking compartment, it is characterised in that also include：

Low temperature conduction pipe, is arranged in the cryogenic liquid soaking compartment, is offered on body multiple towards the superconducting current-limiting The pod apertures on device surface；

Low-pressure balance tank, internal pressure is less than the cryogenic liquid soaking compartment, is connected with the low temperature conduction pipe by regulating valve It is logical, for opening regulating valve when current limiter loses superconductivity so that the cryogenic liquid in the cryogenic liquid soaking compartment is by low Warm conduction pipe enters the low-pressure balance tank, the superconductive current limiter surface near pod apertures is produced forced convertion；

Cryogenic pump, for by cryogenic liquid soaking compartment described in the subcooled liquid blowback in the low-pressure balance tank.

2. the forced convertion high-temperature superconductor cooling device of pressure differential as claimed in claim 1, it is characterised in that the low temperature Cryogenic liquid in liquid soaking compartment is liquid nitrogen, liquid helium or liquid neon.

3. the forced convertion high-temperature superconductor cooling device of pressure differential as claimed in claim 1, it is characterised in that described is low The central area of superconductive current limiter of the warm conduction pipe described in.

4. the forced convertion high-temperature superconductor cooling device of pressure differential as claimed in claim 3, it is characterised in that described is low Warm conduction pipe is circumferentially evenly arranged with described pod apertures near the conduit region of the superconductive current limiter.

5. the forced convertion high-temperature superconductor cooling device of pressure differential as claimed in claim 4, it is characterised in that described is super Current limiter is led for plate-like, setting has multiple and spaced apart arrangement.

6. the forced convertion high-temperature superconductor cooling device of the pressure differential as described in claim 1 or 5, it is characterised in that described Pod apertures be beveling hole, the angle of inclination of relatively described low temperature conduction pipe axis is 30 °~60 °.

7. the forced convertion high-temperature superconductor cooling device of pressure differential as claimed in claim 1, it is characterised in that described tune Section valve uses automatic open and close valve.

8. the forced convertion high-temperature superconductor cooling device of pressure differential as claimed in claim 1, it is characterised in that the low temperature The two ends of conduction pipe are connected to same pipeline, and described regulating valve is provided with the pipeline and entering for low-pressure balance tank is connected to Liquid mouthful.

9. the forced convertion high-temperature superconductor cooling means of a kind of pressure differential, it is characterised in that using as in claim 1~8 The forced convertion high-temperature superconductor cooling device of any described pressure differential, comprises the following steps：

(1) when failure is short-circuited, the superconductive current limiter loses its superconductivity, and the surface of the superconductive current limiter makes low temperature Liquid gasifies, and a bubble part for formation rises to cryogenic liquid soaking compartment upper space and forms high pressure gas area, a part Bubble is covered in the surface of superconductive current limiter, opens the regulating valve；

(2) under the driving of pressure difference, cryogenic liquid is by pod apertures by low for the cryogenic liquid in the cryogenic liquid soaking compartment Warm conduction pipe enters low-pressure balance tank；At the pod apertures, due to the diminution of sectional area, in superconducting current-limiting under differential pressure action Device surface forms forced convertion, the bubble layer on disturbance superconductive current limiter surface；

(3) after the completion of the superconductive current limiter rewarming stage, cryogenic liquid in low-pressure balance tank is added to again using cryogenic pump In the cryogenic liquid soaking compartment, recycling for cryogenic liquid is realized.