A neon cycle refrigerator for high-temperature superconductors

Abstract

The invention discloses a neon cycle refrigerator for high-temperature superconductors, comprising a centrifugal compressor, a supercharged turbine expander, a water-cooled heat exchanger, a liquid nitrogen pre-cooling heat exchanger, a large-flow neon low-temperature heat exchanger, a throttle valve, and a neon dewar. The outlet of the centrifugal compressor is connected to the water-cooled heat exchanger through a pipeline, and then connected to the supercharged end of the supercharged turbine expander, and then connected to the water-cooled heat exchanger at the supercharged end, and then connected to the liquid nitrogen pre-cooling heat exchanger and the large-flow neon low-temperature heat exchanger. After passing through the primary heat exchanger, the outlet is divided into two paths. One path is connected to the expansion end of the supercharged turbine expander, and then passes through the secondary heat exchanger and the low-pressure side of the primary heat exchanger to return to the inlet of the centrifugal compressor. The other path passes through the secondary heat exchanger and the high-pressure side of the tertiary heat exchanger, and then passes through the throttle valve to become liquid and enter the liquid neon dewar. The liquid neon dewar is provided with a heater for maintaining the liquid level. The neon gas passes through the low-pressure sides of the tertiary, secondary, and primary heat exchangers and the low-pressure side of the liquid nitrogen pre-cooling heat exchanger and returns to the inlet of the centrifugal compressor.

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 that integrates a high-speed, high-power centrifugal compressor, a large-flow neon low-temperature heat exchanger, a neon booster turbine expander, etc. Background Art

[0002] With the rapid development of high-temperature superconducting technology, high-temperature superconducting magnets (HTS) have found a range of practical applications, including HTS cables, HTS magnets, HTS motors, HTS energy storage, and HTS magnetic levitation. Cryogenic cooling systems are a crucial component of superconducting equipment and significantly impact the success and industrialization of HTS applications. The stability and cost of cryogenic cooling systems are largely determined by the performance and price of the cryocooler. Because HTS has a relatively high critical temperature compared to other superconducting materials, the operating temperature of HTS magnets depends on the application and magnetic field, typically ranging from 20 to 77 K (liquid hydrogen to liquid nitrogen). This temperature is significantly higher than the 4.2 K liquid helium temperature of low-temperature superconductors, significantly reducing refrigeration costs and simplifying the technical complexity. Cables, transformers, and fault current limiters all operate in the liquid nitrogen temperature range (65-77 K).

[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 is 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, which can solve the bottleneck problem of helium, making it an attractive refrigerant for cooling high-temperature superconductors. Neon is an inert gas, which 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 the HTS coil 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 thermal efficiency of the system, design and integration of key components, and reliability and stability in actual operation. Summary of the Invention

[0004] To address the aforementioned existing technical issues, the present invention provides a neon cycle refrigerator for high-temperature superconductors, specifically an integrated neon cycle refrigerator. This patent focuses on providing an optimal low-temperature environment for the engineering applications of high-temperature superconductors. Specifically, it involves designing a rational refrigeration cycle that not only meets cooling requirements but also ensures system compactness, safety, and reliability.

[0005] The present invention adopts a Kraut cycle with liquid nitrogen pre-cooling, and 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 through the following technical solutions:

[0007] A neon cycle refrigerator for high-temperature superconductors, characterized by comprising a centrifugal compressor unit, a supercharged 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;

[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 turbine 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 pre-cooling heat exchanger is used to use the input liquid nitrogen to exchange heat and cool the input neon gas, and input the neon gas after heat exchange and cooling 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, and then becomes 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 into 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 sequence through the low-pressure side of the first-stage heat exchanger and the low-pressure side of the liquid nitrogen pre-cooling 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 into 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 into 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 heat-exchanged neon gas inputted from the high-pressure side of the first-stage heat exchanger is heat exchanged 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 cooled to 40-50K and then divided into two paths, 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 is a two-stage compression unit.

[0019] The present invention provides a neon cycle refrigerator, which includes a high-speed and high-power centrifugal compressor, a supercharged turbine expander, a water-cooled heat exchanger, a liquid nitrogen pre-cooling heat exchanger, a large-flow neon low-temperature heat exchanger, a throttle valve, and a neon dewar. Two high-speed, high-power centrifugal compressors are connected in series. 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 boost end of a supercharged turbine expander, and then connected to the water-cooled heat exchanger at the boost end, and then connected to a liquid nitrogen pre-cooling 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 supercharged 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 pre-cooling 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 pre-cooling heat exchanger is a three-channel. The low-temperature, low-pressure gas enters the low-pressure side of the heat exchanger to cool the high-temperature, high-pressure gas entering the high-pressure side of the heat exchanger.

[0020] This invention utilizes the braking end of a supercharged turboexpander to boost pressure, employing neon as the working fluid in a refrigerator to liquefy neon. The purpose of liquefying neon is to produce liquid neon for cooling high-temperature superconductors. In principle, a centrifugal compressor is used to improve compression efficiency, reduce footprint, and make the refrigerator more compact. The supercharged turboexpander recovers expansion work, improving refrigerator efficiency. A liquid nitrogen heat exchanger lowers the temperature of the high-pressure neon entering the primary heat exchanger, reducing the size of the refrigerator. A high-flow neon low-temperature heat exchanger recovers the cooling energy of the return air, completing the 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 neon gas is used as the refrigerant, the system's primary components are an integrated centrifugal compressor, a supercharged turboexpander, and a high-flow neon cryogenic heat exchanger. This system's simple structure reduces initial investment and eases maintenance, eliminating the need for fans and other devices that enhance heat exchange, thus saving energy. The addition of a high-flow neon cryogenic heat exchanger increases the centrifugal compressor inlet temperature and reduces the turboexpander inlet temperature by exchanging heat between the cooling unit's exhaust and the centrifugal compressor's exhaust, thereby improving the overall thermal efficiency of the system. The addition of a supercharged turboexpander, whose expansion end shares a common shaft with the booster section, leverages the expansion work of the expander to enhance the efficiency of the refrigerator.

[0023] A supercharged turboexpander consists of a shaft with an impeller at each end: one impeller for expansion (i.e., the expansion end) and the other impeller for braking (i.e., the supercharged end). Traditional turboexpanders use a screw compressor and fan braking, meaning the fan brakes the braking end of the turboexpander, wasting this work. To address this issue, the supercharged turboexpander used in this system uses a supercharged brake at the braking end. This means the gas involved in braking is high-pressure neon gas that has passed through a high-speed, high-power centrifugal compressor. The expansion work at 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 will be described in further detail below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0026] according to Figure 1 The integrated neon cycle refrigerator shown in this illustration includes a centrifugal compressor, a water-cooled heat exchanger, a liquid nitrogen pre-cooling heat exchanger, a high-flow neon cryogenic heat exchanger, a booster turboexpander, a throttle valve, and a liquid neon dewar. The refrigerator also includes a control system for data acquisition at system measurement points and monitoring system operation. The auxiliary control system is equipped with a touchscreen for easy operator operation and monitoring of system 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] This equipment utilizes an integrated design. The liquid nitrogen pre-cooling heat exchanger lowers the temperature of the gas entering the high-flow neon cryogenic heat exchanger, reducing the chiller's cool-down time. The high-flow neon cryogenic heat exchanger raises the inlet temperature of the centrifugal compressor while simultaneously lowering the inlet temperature of the turbine expander. This results in a higher thermal efficiency and greater energy savings for the entire system compared to traditional refrigerators. The water-cooled heat exchanger cools the compressor outlet gas and lowers the inlet gas temperature of the turbine expander.

[0029] During operation: neon gas first enters the centrifugal compressor for supercharging, 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 then 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 exchanges heat with the low-temperature return gas 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 path enters the supercharged At the expansion end of the turboexpander, the gas expands isentropically in the expander, and the low-temperature neon gas cooled to about 30-35K by the expansion end of the supercharged turboexpander 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, 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, then enters the high-pressure side of the tertiary heat exchanger, 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 turboexpander. After passing 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, it returns to the low-pressure side of the centrifugal compressor, completing a cycle.

[0030] While specific embodiments of the present invention have been disclosed for illustrative purposes, intended to facilitate understanding and implementation of the present invention, those skilled in the art will appreciate that various substitutions, variations, 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 disclosure of the preferred embodiments, and the scope of protection claimed in the present invention shall be determined by the scope of the claims.

Claims

1. A neon cycle refrigerator for high-temperature superconductors, characterized in that: It includes a centrifugal compressor unit, a supercharged turbo expander, two water-cooled heat exchangers, a liquid nitrogen pre-cooling heat exchanger, a first-stage heat exchanger, a second-stage heat exchanger, a third-stage heat exchanger, a throttle valve, and a liquid nitrogen 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 turbine 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 pre-cooling heat exchanger is used to use the input liquid nitrogen to exchange heat and cool the input neon gas, and input the neon gas after heat exchange and cooling 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, and then becomes 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 into 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 sequence through the low-pressure side of the first-stage heat exchanger and the low-pressure side of the liquid nitrogen pre-cooling 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, wherein: 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 into 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 into 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 first-stage heat exchanger is heat exchanged 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 cooled to 40-50K and then divided into two paths. 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 then cooled to 27.1K through the high-pressure side of the third-stage heat exchanger and the throttle valve and enters the liquid neon dewar.

4. The neon cycle refrigerator for high-temperature superconductors according to claim 1, wherein: 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 is a two-stage compression compressor.

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