Neon circulation refrigerating machine for high-temperature superconductor

Abstract

The invention discloses a neon cycle refrigerator for a high-temperature superconductor. The neon cycle refrigerator comprises a centrifugal compressor, a supercharged neon turbo expander, a water-cooling heat exchanger, a liquid nitrogen precooling heat exchanger, a large-flow neon low-temperature heat exchanger, a throttling valve and a neon Dewar; an outlet of the centrifugal compressor is connected with the water-cooling heat exchanger through a pipeline, then connected with the pressurizing end of the pressurizing type turbo expander, then connected with the water-cooling heat exchanger at the pressurizing end, then connected with the liquid nitrogen precooling heat exchanger and the large-flow neon low-temperature heat exchanger, and divided into two paths after passing through the first-stage heat exchanger. One path is connected with the expansion end of the supercharged turbo expander and then returns to the inlet of the centrifugal compressor through the low-pressure sides of the second-stage heat exchanger and the first-stage heat exchanger; and the other path passes through the high-pressure sides of the second-stage heat exchanger and the third-stage heat exchanger and then becomes liquid through a throttling valve, the liquid enters a liquid neon Dewar, a heater is arranged in the liquid neon Dewar and used for maintaining the liquid level, and neon returns to an inlet of the centrifugal compressor through the low-pressure sides of the third-stage heat exchanger, the second-stage heat exchanger and the first-stage heat exchanger and the low-pressure side of the liquid nitrogen

Description

Technical Field

[0001] The present invention relates to a refrigerator, in particular to a neon cycle refrigerator for high-temperature superconductors, which is a neon cycle refrigerator integrating a high-speed and high-power centrifugal compressor, a large-flow neon low-temperature heat exchanger, a neon booster turbine expander and the like. Background Art

[0002] With the rapid development of high-temperature superconducting technology, high-temperature superconducting magnets (HTS) have been put into a series of practical applications, such as high-temperature superconducting cables, high-temperature superconducting magnets, high-temperature superconducting motors, high-temperature superconducting energy storage and high-temperature superconducting magnetic levitation. The cryogenic cooling system is an important component of superconducting equipment and has a significant impact on the success or failure of the application and industrial development of high-temperature superconducting magnets (HTS). The stability and cost of the cryogenic cooling system are largely determined by the performance and price of the refrigerator. High-temperature superconductivity has a relatively high critical temperature compared to other superconducting materials. The operating temperature of high-temperature superconducting magnets depends on the application and the size of the magnetic field, usually between 20 and 77K (i.e., liquid hydrogen to liquid nitrogen temperature). This is much higher than the 4.2K liquid helium temperature of low-temperature superconductivity, and its refrigeration cost is also greatly reduced accordingly, and the technical difficulty is reduced. Among them, cables, transformers and fault current limiters all operate in the liquid nitrogen temperature range (65-77K).

[0003] Neon is a colorless rare gas with a gas density of 0.901 kg / m 3 , boiling point 27.1K, critical temperature 44.5K, critical pressure 2.72×103kPa, triple point temperature 24.6K, triple point pressure 43.3kPa. The saturated vapor density at one atmosphere is 4.81kg / m 3 , saturated liquid density 1204kg / m 3 , latent heat of vaporization 85.7kJ / kg. It is safer than hydrogen and has higher latent heat than helium. It mainly comes from air separation. Although it is more expensive than helium, its source is more controllable, making it an attractive refrigerant for cooling high-temperature superconductors. Neon is an inert gas that is much safer than liquid hydrogen. The latent heat of vaporization per unit volume of neon is 40 times higher than that of liquid helium, and the operating temperature of HTS coils cooled by liquid neon is also very stable. However, neon refrigeration cycle machines using neon as a working fluid also face challenges in thermodynamic design and the research and development of key technologies, such as optimization of the system's thermal efficiency, design and integration of key components, and reliability and stability in actual operation. Summary of the invention

[0004] In order to solve the above existing technical problems, the present invention provides a neon cycle refrigerator for high-temperature superconductors, which belongs to an integrated neon cycle refrigerator. The focus of this patent is to provide a superior low-temperature environment for the engineering application of high-temperature superconductors. Specifically, it is to design a reasonable refrigeration cycle process, which not only meets the refrigeration needs, but also ensures the compactness, safety and reliability of the system.

[0005] The present invention adopts a Kraut cycle with liquid nitrogen precooling, uses a high-speed, high-power centrifugal compressor, a large-flow neon low-temperature heat exchanger and a booster turbine expander to improve the efficiency of the system, thereby saving the power consumption of the refrigeration system and improving the efficiency and stability of the entire system.

[0006] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0007] A neon cycle refrigerator for high-temperature superconductors, characterized in that it comprises a centrifugal compressor unit, a supercharged neon turbo expander, two water-cooled heat exchangers, a liquid nitrogen precooling heat exchanger, a primary heat exchanger, a secondary heat exchanger, a tertiary heat exchanger, a throttle valve, and a liquid neon dewar;

[0008] The outlet of the centrifugal compressor unit is connected to the first water-cooled heat exchanger through a pipeline, so as to pressurize the input neon gas and then input it into the first water-cooled heat exchanger;

[0009] The output end of the first water-cooled heat exchanger is connected to the boost end of the booster turbo expander, and is used to cool the input neon gas before inputting it into the boost end of the booster turbo expander;

[0010] The boosting end of the booster turbo expander is connected to the second water-cooled heat exchanger, and is used to boost the input cooling neon gas and then input it into the second water-cooled heat exchanger;

[0011] The output end of the second water-cooled heat exchanger is connected to the high-pressure side of the liquid nitrogen pre-cooling heat exchanger, and is used to cool the input pressurized neon gas before inputting it into the liquid nitrogen pre-cooling heat exchanger;

[0012] The high-pressure side of the liquid nitrogen precooling heat exchanger is used to use the input liquid nitrogen to perform heat exchange and temperature reduction on the input neon gas, and input the neon gas after heat exchange and temperature reduction into the high-pressure side of the first-stage heat exchanger;

[0013] The high-pressure side of the first-stage heat exchanger is used to cool the input neon gas and then divide it into two paths. One path is input to the expansion end of the booster turbine expander for expansion and cooling and then input to the low-pressure side of the second-stage heat exchanger; the other path passes through the high-pressure side of the second-stage heat exchanger, the high-pressure side of the third-stage heat exchanger, and the throttle valve in sequence to become liquid and input to the liquid neon dewar;

[0014] The liquid neon dewar is used to store liquid neon and detect the liquid neon level. When the liquid level reaches a set value, the liquid neon is heated. The neon gas in the liquid neon dewar is cooled by the low-pressure side of the three-stage heat exchanger and then input to the low-pressure side of the second-stage heat exchanger.

[0015] The low-pressure side of the second-stage heat exchanger is used to cool the input neon gas, which is then cooled in turn through the low-pressure side of the first-stage heat exchanger and the low-pressure side of the liquid nitrogen precooling heat exchanger before being input to the low-pressure side of the centrifugal compressor unit.

[0016] Furthermore, the centrifugal compressor unit compresses the 1.01 bar neon gas input from the low-pressure side to 9.1 bar and then inputs it to the first water-cooled heat exchanger; the boosting end of the booster turbine expander pressurizes the input neon gas to 10 bar and then inputs it to the second water-cooled heat exchanger.

[0017] Furthermore, the high-pressure side of the liquid nitrogen pre-cooling heat exchanger uses the input liquid nitrogen to exchange heat with the input neon gas and cool it down to 80-90K; the neon gas after heat exchange inputted from the high-pressure side of the first-stage heat exchanger exchanges heat with the 35-45K low-temperature return gas inputted from the low-pressure side of the first-stage heat exchanger, and the neon gas on the high-pressure side of the first-stage heat exchanger is divided into two paths after the temperature is reduced to 40-50K. One path enters the expansion end of the booster turbine expander for expansion and cooling to obtain 30-35K low-temperature neon gas, which enters the low-pressure side of the second-stage heat exchanger for heat exchange with the high-pressure side gas of the second-stage heat exchanger; the other path enters the high-pressure side of the second-stage heat exchanger for heat exchange with the low-pressure return gas inputted from the low-pressure side of the second-stage heat exchanger to obtain 35-40K low-temperature neon gas, which is cooled to 27.1K through the high-pressure side of the third-stage heat exchanger and the throttle valve in turn and enters the liquid neon Dewar.

[0018] Furthermore, the centrifugal compressor unit includes two high-speed and high-power centrifugal compressors connected in series, and each high-speed and high-power centrifugal compressor has two-stage compression.

[0019] The invention provides a neon cycle refrigerator, which comprises a high-speed and high-power centrifugal compressor, a supercharged neon turbine expander, a water-cooled heat exchanger, a liquid nitrogen precooling heat exchanger, a large-flow neon low-temperature heat exchanger, a throttle valve, and a neon dewar. Two high-speed and high-power centrifugal compressors are connected in series, and each centrifugal compressor has two-stage compression. The outlet of the centrifugal compressor is connected to a water-cooled heat exchanger through a pipeline, and then connected to the boosting end of a booster turbine expander, and then connected to the water-cooled heat exchanger at the boosting end, and then connected to a liquid nitrogen precooling heat exchanger and a large-flow neon low-temperature heat exchanger. After passing through the first-stage heat exchanger, it is divided into two paths. One path is connected to the expansion end of the booster turbine expander for expansion and cooling, and then passes through the second-stage heat exchanger and the low-pressure side of the first-stage heat exchanger to return to the inlet of the centrifugal compressor; the other path passes through the high-pressure side of the second-stage heat exchanger and the third-stage heat exchanger, and then passes through a throttle valve to become liquid and enter the liquid neon dewar. There is a heater in the liquid neon dewar. After the liquid level reaches the target value, the heater is turned on to maintain the liquid level. The neon gas passes through the low-pressure sides of the third, second, and first-stage heat exchangers and the low-pressure side of the liquid nitrogen precooling heat exchanger and returns to the inlet of the centrifugal compressor. The large-flow neon low-temperature heat exchanger is a dual-channel, and the liquid nitrogen precooling heat exchanger is a three-channel. The low-temperature and low-pressure gas enters the low-pressure side of the heat exchanger to cool the high-temperature and high-pressure gas entering the high-pressure side of the heat exchanger.

[0020] The present invention utilizes the brake end of the booster turbine expander for boosting, and uses neon as the working fluid of the refrigerator to liquefy neon. The purpose of liquefying neon is to produce liquid neon to cool high-temperature superconductors. In principle, a centrifugal compressor is used to improve compression efficiency, reduce floor space, and make the refrigerator more compact as a whole; a booster turbine expander is used to recover expansion work to improve the efficiency of the refrigerator; a liquid nitrogen heat exchanger reduces the temperature of neon on the high-pressure side entering the primary heat exchanger, reducing the volume of the refrigerator; a large-flow neon low-temperature heat exchanger recovers and utilizes the coldness of the return air, thereby completing a cycle and improving energy utilization.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] In this neon cycle refrigerator, since this system uses neon as its refrigerant, the most important equipment of this refrigeration system is only an integrated centrifugal compressor, a supercharged turbine expander and a large-flow neon low-temperature heat exchanger. Therefore, this system has a simple structure, saving the initial investment for installing this system, and is easy to maintain. It does not require devices such as fans to enhance heat exchange, thereby saving electricity. This system has added a large-flow neon low-temperature heat exchanger. By exchanging heat between the outlet air of the cold unit and the outlet air of the centrifugal compressor, the inlet temperature of the centrifugal compressor is increased and the inlet temperature of the turbine expander is reduced, thereby improving the thermal efficiency of the whole machine. This system has added a supercharged turbine expander, whose expansion end and the supercharged section share a shaft, and the expansion work of the expander can be used to improve the efficiency of the refrigerator.

[0023] The supercharged turbo expander includes a shaft with an impeller at each end of the shaft, one impeller is used for expansion (i.e. as the expansion end), and the other impeller is used for braking (i.e. the supercharged end). The traditional turbo expander uses a screw compressor and fan braking, that is, the braking end of the turbo expander uses fan braking, so this part of the work is wasted. To address this problem, the braking end of the supercharged turbo expander used in this system is a supercharged brake, that is, the gas involved in the braking is a high-pressure neon gas that has passed through a high-speed, high-power centrifugal compressor, and the expansion work of this expansion end can be used for supercharging, thereby improving the efficiency of the refrigerator. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a structural diagram of the neon cycle refrigerator for high-temperature superconductors of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention but not to limit the scope of the present invention.

[0026] according to Figure 1 An integrated neon cycle refrigerator shown includes a centrifugal compressor, a water-cooled heat exchanger, a liquid nitrogen pre-cooling heat exchanger, a large-flow neon low-temperature heat exchanger, a booster turbine expander, a throttle valve, and a liquid neon dewar. In addition, the entire refrigerator also includes a control system for data collection at system measurement points and monitoring system operation. The auxiliary control system is equipped with a touch screen to facilitate operator operation and monitoring of system operation status.

[0027] The centrifugal compressor is equipped with a frequency converter for adjusting the speed of the compressor, that is, the power of the compressor.

[0028] The equipment is manufactured in an integrated manner. The function of the liquid nitrogen pre-cooling heat exchanger is to reduce the temperature of the gas entering the large-flow neon low-temperature heat exchanger and reduce the cooling time of the refrigerator. The function of the large-flow neon low-temperature heat exchanger is to increase the inlet temperature of the centrifugal compressor and reduce the inlet temperature of the turbine expander, so that the whole system has higher thermal efficiency and saves more electricity compared with the traditional refrigerator. The water-cooled heat exchanger is used to cool the temperature of the compressor outlet gas and reduce the temperature of the turbine expander inlet gas.

[0029] During operation: neon gas first enters the centrifugal compressor for pressurization, and the 1.01bar neon gas is compressed to 9.1bar by the high-speed and high-power centrifugal compressor, and then enters the water-cooled heat exchanger to cool the centrifugal compressor outlet gas. Subsequently, it enters the supercharging end of the supercharged turbine expander to be pressurized to 10bar, and then enters the water-cooled heat exchanger at the supercharging end and enters the high-pressure side of the liquid nitrogen pre-cooling heat exchanger. The liquid nitrogen input from the liquid nitrogen tower exchanges heat with the neon gas entering the high-pressure side of the liquid nitrogen pre-cooling heat exchanger and cools the neon gas to 80-90K. The liquid nitrogen is heated from 80K to room temperature and is discharged. After cooling to 80-90K, the neon gas enters the high-pressure side of the first-stage heat exchanger of the large-flow neon low-temperature heat exchanger, and heat exchanges with the low-temperature return air of about 35-45K on the low-pressure side of the first-stage heat exchanger to reduce the temperature to about 40-50K, and then is divided into two paths, one entering the supercharged At the expansion end of the turbo expander, the gas is isentropically expanded in the expander, and the low-temperature neon gas cooled to about 30-35K through the expansion end of the supercharged turbo expander enters the low-pressure side of the secondary heat exchanger for heat exchange with the high-pressure side gas of the secondary heat exchanger; the other way enters the high-pressure side of the secondary heat exchanger, and the neon gas entering the high-pressure side of the secondary heat exchanger exchanges heat with the low-temperature return gas input from the low-pressure side of the secondary heat exchanger and cools down to about 35-40K, and then enters the high-pressure side of the tertiary heat exchanger, and is cooled to the temperature of 27.1K liquid neon through the throttle valve, and then enters the liquid neon dewar. The neon vapor of the liquid neon dewar returns to the low-pressure side of the tertiary heat exchanger and merges with the low-temperature neon gas expanded from the turbo expander, and passes through the low-pressure sides of the secondary heat exchanger, the primary heat exchanger and the liquid nitrogen pre-cooling heat exchanger to cool the cold neon gas on the high-pressure side, and then returns to the low-pressure side of the centrifugal compressor to complete a cycle.

[0030] Although the specific embodiments of the present invention are disclosed for the purpose of illustration, the purpose is to help understand the content of the present invention and implement it accordingly, those skilled in the art will understand that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the best embodiment, and the scope of the present invention is subject to the scope defined in the claims.

Claims

1. A neon cycle refrigerator for high temperature superconductors, characterized in that: It includes a centrifugal compressor unit, a supercharged neon turbine expander, two water-cooled heat exchangers, a liquid nitrogen pre-cooling heat exchanger, a primary heat exchanger, a secondary heat exchanger, a tertiary heat exchanger, a throttle valve, and a liquid neon dewar; The outlet of the centrifugal compressor unit is connected to the first water-cooled heat exchanger through a pipeline, so as to pressurize the input neon gas and then input it into the first water-cooled heat exchanger; The output end of the first water-cooled heat exchanger is connected to the boost end of the booster turbo expander, and is used to cool the input neon gas before inputting it into the boost end of the booster turbo expander; The boosting end of the booster turbo expander is connected to the second water-cooled heat exchanger, and is used to boost the input cooling neon gas and then input it into the second water-cooled heat exchanger; The output end of the second water-cooled heat exchanger is connected to the high-pressure side of the liquid nitrogen pre-cooling heat exchanger, and is used to cool the input pressurized neon gas before inputting it into the liquid nitrogen pre-cooling heat exchanger; The high-pressure side of the liquid nitrogen precooling heat exchanger is used to use the input liquid nitrogen to perform heat exchange and temperature reduction on the input neon gas, and input the neon gas after heat exchange and temperature reduction into the high-pressure side of the first-stage heat exchanger; The high-pressure side of the first-stage heat exchanger is used to cool the input neon gas and then divide it into two paths. One path is input to the expansion end of the booster turbine expander for expansion and cooling and then input to the low-pressure side of the second-stage heat exchanger; the other path passes through the high-pressure side of the second-stage heat exchanger, the high-pressure side of the third-stage heat exchanger, and the throttle valve in sequence to become liquid and input to the liquid neon dewar; The liquid neon dewar is used to store liquid neon and detect the liquid neon level. When the liquid level reaches a set value, the liquid neon is heated. The neon gas in the liquid neon dewar is cooled by the low-pressure side of the three-stage heat exchanger and then input to the low-pressure side of the second-stage heat exchanger. The low-pressure side of the second-stage heat exchanger is used to cool the input neon gas, which is then cooled in turn through the low-pressure side of the first-stage heat exchanger and the low-pressure side of the liquid nitrogen precooling heat exchanger before being input to the low-pressure side of the centrifugal compressor unit.

2. The neon cycle refrigerator for high temperature superconductors according to claim 1, characterized in that: The centrifugal compressor unit compresses the 1.01 bar neon gas input from the low-pressure side to 9.1 bar and then inputs it to the first water-cooled heat exchanger; the boosting end of the booster turbine expander pressurizes the input neon gas to 10 bar and then inputs it to the second water-cooled heat exchanger.

3. The neon cycle refrigerator for high temperature superconductors according to claim 1 or 2, characterized in that: The high-pressure side of the liquid nitrogen pre-cooling heat exchanger uses the input liquid nitrogen to exchange heat with the input neon gas and cool it down to 80-90K; the neon gas after heat exchange inputted from the high-pressure side of the primary heat exchanger exchanges heat with the 35-45K low-temperature return gas inputted from the low-pressure side of the primary heat exchanger, and the neon gas on the high-pressure side of the primary heat exchanger is divided into two paths after the temperature is reduced to 40-50K. One path enters the expansion end of the booster turbine expander for expansion and cooling to obtain 30-35K low-temperature neon gas, which enters the low-pressure side of the secondary heat exchanger for heat exchange with the high-pressure side gas of the secondary heat exchanger; the other path enters the high-pressure side of the secondary heat exchanger for heat exchange with the low-pressure return gas inputted from the low-pressure side of the secondary heat exchanger to obtain 35-40K low-temperature neon gas, which is cooled to 27.1K through the high-pressure side of the tertiary heat exchanger and the throttle valve in turn and enters the liquid neon Dewar.

4. The neon cycle refrigerator for high temperature superconductors according to claim 1, characterized in that: The centrifugal compressor unit comprises two high-speed and high-power centrifugal compressors connected in series, and each high-speed and high-power centrifugal compressor has two-stage compression.

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