A low-temperature refrigeration system and method combining pressure reduction pre-cooling and a vortex tube

Abstract

The application provides a low-temperature refrigeration system combined with pressure reduction pre-cooling and a vortex tube, comprising a liquid nitrogen pressure reduction pre-cooling device, wherein the inside of the liquid nitrogen pressure reduction pre-cooling device is provided with a pre-cooling heat exchanger, the gas inlet end of the pre-cooling heat exchanger is connected with a compressor, the gas outlet end of the pre-cooling heat exchanger is connected with a vortex tube, the cold gas outlet end of the vortex tube is connected with a cooling cabin, the hot gas outlet end of the vortex tube and the gas outlet end of the cooling cabin are jointly connected with a mixed heating chamber, and the gas outlet end of the mixed heating chamber is connected with the compressor. The application also simultaneously provides a refrigeration method based on the refrigeration system. The low-temperature refrigeration system combined with pressure reduction pre-cooling and the vortex tube and the refrigeration method provided by the application combine liquid nitrogen pressure reduction refrigeration and vortex tube refrigeration, realize refrigeration in a temperature range of 30K-60K, and have the characteristics of simple equipment, stable operation and high reliability.

Description

Technical Field

[0001] This invention relates to a refrigeration system and refrigeration method, and more particularly to a low-temperature refrigeration system and refrigeration method combining pressure reduction precooling and vortex tube. Background Technology

[0002] Cryogenic refrigeration and cooling technology are crucial for superconductivity. Superconducting materials only exhibit superconducting properties below their critical temperature. Due to heat loads caused by factors such as AC losses and environmental heat leakage, superconducting devices must be equipped with reliable and continuous cryogenic refrigeration and cooling systems. Furthermore, even lower refrigeration temperatures can further enhance the performance of superconducting materials. Currently, refrigeration methods in the superconducting field include closed-loop refrigeration and open-loop refrigeration, which involves heat absorption through the vaporization of a medium. Closed-loop refrigeration has a wide cooling temperature range, but its refrigeration efficiency is low and its cost is high, with efficiency decreasing at lower temperatures. Therefore, open-loop refrigeration remains an irreplaceable cooling method. Commonly used open-loop refrigerants include liquid nitrogen, liquid hydrogen, liquid neon, and liquid helium. At atmospheric pressure, the boiling points of liquid nitrogen, liquid hydrogen, liquid neon, and liquid helium are 77K, 27K, 20K, and 5K, respectively. Among them, liquid nitrogen, after applying the principle of decompression and cooling, can only reach a minimum cooling temperature of 65K. Therefore, there is no suitable open-loop refrigerant in the temperature range of 30K to 60K.

[0003] In summary, due to the lack of suitable media, refrigeration in the 30K–60K temperature range cannot be achieved using open-loop refrigeration methods. Instead, it relies solely on closed-loop refrigeration units, which offer limited options. However, commonly used closed-loop refrigeration units suffer from low refrigeration efficiency.

[0004] Vortex tube refrigeration technology has been widely applied in various fields. Compressed gas undergoes energy separation within the vortex tube, resulting in a low-temperature flow and a high-temperature flow. The cold-end temperature drop can be adjusted by regulating the inlet pressure and cold flow rate. As a static device, the vortex tube contains no moving parts, has a simple structure, stable operation, and fast response, and its refrigeration efficiency is higher than that of throttling refrigeration.

[0005] Based on the above technical background, in order to solve the problems of the single cooling method and low cooling efficiency in the current 30K-60K temperature range, this invention combines liquid nitrogen depressurization refrigeration with vortex tube refrigeration, and proposes a low-temperature cooling system that combines depressurization refrigeration and vortex tube, providing a feasible solution for low-temperature refrigeration in the 30K-60K temperature range, which has the advantages of simple equipment, stable operation and high reliability. Summary of the Invention

[0006] The purpose of this invention is to overcome existing defects and provide a low-temperature refrigeration system and refrigeration method that combines depressurization precooling and vortex tube, solving the problem that open-loop refrigeration cannot be achieved in the current temperature range of 30K to 60K.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A cryogenic refrigeration system combining depressurization precooling and vortex tube technology includes a liquid nitrogen depressurization precooling device. The liquid nitrogen depressurization precooling device has a precooling heat exchanger internally. The inlet end of the precooling heat exchanger is connected to a compressor, and the outlet end of the precooling heat exchanger is connected to a vortex tube. The cold outlet end of the vortex tube is connected to a cooling chamber, and the hot outlet end of the vortex tube and the outlet end of the cooling chamber are both connected to a mixing heating chamber. The outlet end of the mixing heating chamber is connected to the compressor. The inlet end of the liquid nitrogen depressurization precooling device is connected to a liquid nitrogen tank, and the outlet end of the liquid nitrogen depressurization precooling device is connected to a vacuum pump via a heater.

[0009] Furthermore, a total flow control valve is provided between the precooling heat exchanger and the vortex tube, and a cold air flow control valve is provided between the cold air outlet end of the vortex tube and the cooling chamber.

[0010] Furthermore, the mixing heating chamber includes an air inlet section and a pressurization section. The air inlet section is provided with a central channel, and swirling channels are evenly distributed around the outer periphery of the central channel. The air inlet end of the central channel is connected to the hot air outlet end of the vortex tube, and the air inlet end of the swirling channel is connected to the air outlet end of the cooling chamber. The pressurization section is provided with a pressurization cavity with a gradually increasing inner diameter in the shape of a trumpet. The air outlet ends of the central channel and the swirling channels are connected to the pressurization cavity.

[0011] Furthermore, the calculation formula for the refrigeration power of the liquid nitrogen depressurization precooling device is as follows:

[0012]

[0013] Wherein, Q0 is the heat leakage generated between the liquid nitrogen decompression precooling device and the environment, and c p0 T1 is the specific heat at constant pressure of helium, the working medium in the liquid nitrogen depressurization precooling device; T2 is the helium temperature at the inlet of the liquid nitrogen depressurization precooling device; Q is the refrigeration power required by the cooling chamber; and T is the specific heat at constant pressure of helium. 71 and T 72 The temperatures of the helium gas at the inlet and outlet of the cooling chamber are c, respectively. p7 denoted as μ, where μ is the average isobaric specific heat of helium gas in the cooling chamber, and μ is the cold flow rate of the vortex tube.

[0014] Furthermore, the formula for calculating the heating power of the heater is as follows:

[0015]

[0016] Where Q2 is the cooling power of the liquid nitrogen depressurization precooling device, r satc represents the latent heat of vaporization of liquid nitrogen in the liquid nitrogen decompression precooling device under operating conditions. pg T is the average isobaric specific heat of nitrogen gas in the heater under operating conditions. v T is the allowable temperature of the vacuum pump. sat The saturation temperature of liquid nitrogen in the cavity of the liquid nitrogen decompression and precooling device under working conditions.

[0017] Furthermore, the pumping speed of the vacuum pump under the working pressure inside the liquid nitrogen decompression and precooling device cavity should not be less than the design pumping speed S1 of the vacuum pump. The calculation formula for the design pumping speed of the vacuum pump is as follows:

[0018]

[0019] Where Q2 is the cooling power of the liquid nitrogen depressurization precooling device, r sat The latent heat of vaporization of liquid nitrogen in the cavity of the liquid nitrogen decompression and precooling device under working conditions, ρ g The density of nitrogen gas at the heater outlet.

[0020] Furthermore, the mixed helium gas flow is decelerated and pressurized within the pressurization section of the mixing heating chamber. The formula for calculating the inlet and outlet pressure difference is as follows:

[0021]

[0022] Where Q is the cooling power required by the cooling chamber, ρ8 is the average density of helium in the pressurization section of the mixing heating chamber, and T 71 and T 72 The temperatures of the helium gas at the inlet and outlet of the cooling chamber are c, respectively. p7 The average isobaric specific heat of helium gas in the cooling chamber, μ is the cold flow rate of the vortex tube, and d is the average isobaric specific heat of helium gas in the cooling chamber. i d0 is the diameter at the inlet of the pressurization section of the mixing heating chamber, and d0 is the diameter at the outlet of the pressurization section of the mixing heating chamber.

[0023] Furthermore, the power calculation formula for the compressor is as follows:

[0024]

[0025] Where Q is the cooling power required by the cooling chamber, and T 71 and T 72 The temperatures of the helium gas at the inlet and outlet of the cooling chamber are c, respectively. p7 The average isobaric specific heat of helium gas in the cooling chamber, μ is the cold flow rate of the vortex tube, k is the Boltzmann constant, R is the molar gas constant, and T is the average isobaric specific heat of helium gas in the cooling chamber. * π represents the total temperature of the helium gas at the outlet of the mixing heating chamber. * η is the boost ratio of the compressor, and η is the compressor efficiency.

[0026] The refrigeration method based on the above-mentioned cryogenic refrigeration system combining depressurization precooling and vortex tubes uses helium as the working medium for cooling the equipment to be cooled. The helium is cooled to about 65K in a liquid nitrogen depressurization precooling device, and then enters the vortex tube where it is separated into two streams of cold and hot helium. The cold helium has a temperature between 30K and 60K and enters the cooling chamber to cool the equipment to be cooled. Afterward, the cold helium is mixed with the hot helium in a mixing and heating chamber. The temperature of the mixed helium rises to the allowable inlet temperature of the compressor, and then it enters the compressor for pressurization before entering the liquid nitrogen depressurization precooling device, thus forming a refrigeration cycle with helium as the working medium.

[0027] This invention discloses a cryogenic refrigeration system and method that combines depressurization precooling with vortex tube refrigeration. It combines liquid nitrogen depressurization refrigeration with vortex tube refrigeration to achieve refrigeration in the temperature range of 30K to 60K. It features simple equipment, stable operation, and high reliability. Attached Figure Description

[0028] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0029] Figure 1 This is a schematic diagram of the refrigeration system in this invention;

[0030] Figure 2 This is a three-dimensional schematic diagram of the mixing heating chamber in this invention;

[0031] Figure 3 This is a front sectional view of the mixing heating chamber in this invention. Detailed Implementation

[0032] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0033] like Figure 1-3 As shown, a cryogenic refrigeration system combining depressurization precooling and vortex tube is provided, including a liquid nitrogen depressurization precooling device 2. A precooling heat exchanger 3 is installed inside the liquid nitrogen depressurization precooling device 2. The inlet end of the precooling heat exchanger 3 is connected to a compressor 9. The outlet end of the precooling heat exchanger 3 is connected to a vortex tube 6. The cold outlet end of the vortex tube 6 is connected to a cooling chamber 7. The hot outlet end of the vortex tube 6 and the outlet end of the cooling chamber 7 are connected to a mixing heating chamber 8. The outlet end of the mixing heating chamber 8 is connected to the compressor 9.

[0034] Working principle:

[0035] Helium is used as the working medium for cooling the equipment to be cooled. The helium is cooled to about 65K in a liquid nitrogen decompression precooling device, and then enters the vortex tube where it is separated into two streams of cold and hot helium. The cold helium has a temperature between 30K and 60K and enters the cooling chamber to cool the equipment to be cooled. After that, the cold helium is mixed with the hot helium in the mixing heating chamber. The temperature of the mixed helium rises to the allowable inlet temperature of the compressor and enters the compressor for pressurization before entering the liquid nitrogen decompression precooling device. This forms a refrigeration cycle with helium as the working medium.

[0036] The inlet of the liquid nitrogen depressurization precooling device 2 is connected to a liquid nitrogen tank 1, and the outlet of the liquid nitrogen depressurization precooling device 2 is connected to a vacuum pump 5 via a heater 4. The liquid nitrogen tank provides liquid nitrogen as the cooling medium for the liquid nitrogen depressurization precooling device, and the vacuum pump provides a low-pressure environment for the cavity of the liquid nitrogen depressurization precooling device. The liquid nitrogen in the cavity of the liquid nitrogen depressurization precooling device absorbs heat and vaporizes under low pressure to precool the helium flowing through the precooling heat exchanger. The nitrogen gas generated after vaporization is heated to the allowable inlet temperature of the vacuum pump by the heater and is finally discharged by the vacuum pump.

[0037] A total flow control valve v1 is installed between the precooling heat exchanger 3 and the vortex tube 6, and a cold air flow control valve v2 is installed between the cold air outlet end of the vortex tube 6 and the cooling chamber 7. By controlling the total flow control valve and the cold air flow control valve, the cold flow rate of the vortex tube is adjusted, thereby changing the cooling temperature and cooling capacity of the cooling chamber.

[0038] The mixing and heating chamber 8 includes an inlet section 81 and a pressurization section 82. The inlet section has a central channel, and swirling channels are evenly distributed circumferentially around the outer side of the central channel. The inlet end of the central channel is connected to the hot outlet end of the vortex tube, and the inlet end of the swirling channels is connected to the outlet end of the cooling chamber. The pressurization section has a flared chamber with a gradually increasing inner diameter. The outlet ends of the central channel and the swirling channels are connected to the pressurization chamber. Cold helium gas generates circumferential velocity in the swirling channels, forming a reflux zone, which enables the cold and hot helium gas to be fully and uniformly mixed. The velocity of the mixed gas decreases in the pressurization chamber, and according to Bernoulli's principle, the static pressure of the fluid increases.

[0039] The formula for calculating the refrigeration power of a liquid nitrogen vacuum precooling device is as follows:

[0040]

[0041] Where Q0 is the heat loss generated between the liquid nitrogen decompression precooling device and the environment, and c p0 T1 is the isobaric specific heat of helium, the working medium in the liquid nitrogen depressurization precooling device; T2 is the inlet temperature of the liquid nitrogen depressurization precooling device; Q is the required cooling power of the cooling chamber; and T is the temperature of the liquid nitrogen depressurization precooling device. 71 and T 72 These are the helium temperatures at the inlet and outlet of the cooling chamber, respectively, c p7denoted as , where is the average isobaric specific heat of helium in the cooling chamber, and μ is the cold flow rate of the vortex tube.

[0042] This formula establishes the relationship between the heat exchange power of the liquid nitrogen decompression precooling device and the parameters of the cooling chamber.

[0043] The formula for calculating the heating power of a heater is:

[0044]

[0045] Where Q2 is the cooling power of the liquid nitrogen vacuum precooling device, r sat c represents the latent heat of vaporization of liquid nitrogen in the liquid nitrogen decompression precooling device under operating conditions. pg T is the average isobaric specific heat of nitrogen gas in the heater under operating conditions. v T is the allowable temperature for the vacuum pump. sat The saturation temperature of liquid nitrogen in the chamber of the liquid nitrogen decompression and precooling device under working conditions.

[0046] Because the vaporized nitrogen cannot be immediately discharged from the system after heat exchange between the liquid nitrogen depressurization precooling device and the helium in the main flow path, it needs to be heated to the allowable operating temperature of the vacuum pump before the pump can operate normally. Therefore, this formula establishes the relationship between the cooling power of the liquid nitrogen depressurization precooling device and the heating power of the heater.

[0047] The pumping speed of the vacuum pump under the working pressure inside the liquid nitrogen decompression and precooling device should not be less than the design pumping speed S1. The formula for calculating the design pumping speed of the vacuum pump is as follows:

[0048]

[0049] Where Q2 is the cooling power of the liquid nitrogen vacuum precooling device, r sat The latent heat of vaporization of liquid nitrogen in the working state of the liquid nitrogen decompression precooling device chamber, ρ g This represents the density of nitrogen gas at the heater outlet.

[0050] This formula reflects the relationship between the heating power of the heater and the pumping speed of the vacuum pump.

[0051] The mixed helium gas flow is decelerated and pressurized in the pressurization section of the mixing heating chamber. The formula for calculating the pressure difference between the inlet and outlet is as follows:

[0052]

[0053] Where Q is the cooling power required by the cooling chamber, ρ8 is the average density of helium in the pressurization section of the mixing heating chamber, and T 71 and T 72 These are the temperatures of the helium gas at the inlet and outlet of the cooling chamber, respectively, c p7The average isobaric specific heat of helium in the cooling chamber is given by μ, where μ is the cold flow rate of the vortex tube, and d is the cold flow rate of the vortex tube. i d0 is the diameter at the inlet of the pressurization section of the mixing heating chamber, and d0 is the diameter at the outlet of the pressurization section of the mixing heating chamber.

[0054] This formula combines the cooling capacity required by the pressurization section and the cooling chamber, the temperature difference between the inlet and outlet, and the cold flow rate of the vortex tube to obtain a pressurization calculation formula for the pressurization section affected by multiple component parameters.

[0055] The compressor is a centrifugal compressor, and its power calculation formula is as follows:

[0056]

[0057] Where Q is the cooling power required by the cooling chamber, and T 71 and T 72 These are the temperatures of the helium gas at the inlet and outlet of the cooling chamber, respectively, c p7 The average isobaric specific heat of helium in the cooling chamber, μ is the cold flow rate of the vortex tube, k is the Boltzmann constant, R is the molar gas constant, and T is the average isobaric specific heat of helium in the cooling chamber. * π represents the total temperature of the helium gas at the outlet of the mixing heating chamber. * η is the compressor boost ratio, and η is the compressor efficiency.

[0058] This formula reflects the relationship between compressor power and the parameters of the vortex tube and cooling chamber.

[0059] The calculation formulas listed above are all mathematical manifestations of the system principle. Starting from the cooling capacity required by the cooling chamber in the system, the performance parameters of other equipment are derived as a basis for design or selection.

[0060] This invention discloses a cryogenic refrigeration system and method that combines depressurization precooling with vortex tube refrigeration. It combines liquid nitrogen depressurization refrigeration with vortex tube refrigeration to achieve refrigeration in the temperature range of 30K to 60K. It features simple equipment, stable operation, and high reliability.

[0061] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cryogenic refrigeration system combining pressure reduction precooling and vortex tube cooling, characterized in that: The device includes a liquid nitrogen depressurization and precooling unit, which has a precooling heat exchanger inside. The inlet end of the precooling heat exchanger is connected to a compressor, and the outlet end of the precooling heat exchanger is connected to a vortex tube. The cold outlet end of the vortex tube is connected to a cooling chamber, and the hot outlet end of the vortex tube and the outlet end of the cooling chamber are connected to a mixing heating chamber. The outlet end of the mixing heating chamber is connected to the compressor. The inlet of the liquid nitrogen decompression and precooling device is connected to a liquid nitrogen tank, and the outlet of the liquid nitrogen decompression and precooling device is connected to a vacuum pump via a heater.

2. The cryogenic refrigeration system combining pressure reduction precooling and vortex tube as described in claim 1, characterized in that: A total flow control valve is installed between the precooling heat exchanger and the vortex tube, and a cold air flow control valve is installed between the cold air outlet end of the vortex tube and the cooling chamber.

3. The cryogenic refrigeration system combining pressure reduction precooling and vortex tube as described in claim 1, characterized in that: The mixing heating chamber includes an air intake section and a pressurization section. The air intake section is provided with a central channel, and swirling channels are evenly distributed around the outer periphery of the central channel. The air intake end of the central channel is connected to the hot air outlet end of the vortex tube, and the air intake end of the swirling channel is connected to the air outlet end of the cooling chamber. The pressurization section is provided with a flared pressurization cavity with a gradually increasing inner diameter, and the outlets of the central channel and the swirl channel are connected to the pressurization cavity.

4. The cryogenic refrigeration system combining pressure reduction precooling and vortex tube according to claim 1, characterized in that: The formula for calculating the refrigeration power of the liquid nitrogen depressurization precooling device is as follows: Wherein, Q0 is the heat leakage generated between the liquid nitrogen decompression precooling device and the environment, and c p0 T1 is the specific heat at constant pressure of helium, the working medium in the liquid nitrogen depressurization precooling device; T2 is the helium temperature at the inlet of the liquid nitrogen depressurization precooling device; Q is the refrigeration power required by the cooling chamber; and T is the specific heat at constant pressure of helium. 71 and T 72 The temperatures of the helium gas at the inlet and outlet of the cooling chamber are c, respectively. p7 denoted as μ, where μ is the average isobaric specific heat of helium gas in the cooling chamber, and μ is the cold flow rate of the vortex tube.

5. The cryogenic refrigeration system combining pressure reduction precooling and vortex tube according to claim 2, characterized in that: The formula for calculating the heating power of the heater is: Where Q2 is the cooling power of the liquid nitrogen depressurization precooling device, r sat c represents the latent heat of vaporization of liquid nitrogen in the liquid nitrogen decompression precooling device under operating conditions. pg T is the average isobaric specific heat of nitrogen gas in the heater under operating conditions. v T is the allowable temperature of the vacuum pump. sat The saturation temperature of liquid nitrogen in the cavity of the liquid nitrogen decompression and precooling device under working conditions.

6. The cryogenic refrigeration system combining pressure reduction precooling and vortex tube according to claim 1, characterized in that: The pumping speed of the vacuum pump under the working pressure inside the liquid nitrogen decompression and precooling device should not be less than the design pumping speed S1. The calculation formula for the design pumping speed of the vacuum pump is as follows: Where Q2 is the cooling power of the liquid nitrogen depressurization precooling device, r sat The latent heat of vaporization of liquid nitrogen in the cavity of the liquid nitrogen decompression and precooling device under working conditions, ρ g The density of nitrogen gas at the heater outlet.

7. A cryogenic refrigeration system combining pressure reduction precooling and vortex tube according to claim 3, characterized in that: The mixed helium gas flow is decelerated and pressurized in the pressurization section of the mixing heating chamber. The formula for calculating the pressure difference between the inlet and outlet is as follows: Where Q is the cooling power required by the cooling chamber, ρ8 is the average density of helium in the pressurization section of the mixing heating chamber, and T 71 and T 72 The temperatures of the helium gas at the inlet and outlet of the cooling chamber are c, respectively. p7 The average isobaric specific heat of helium gas in the cooling chamber, μ is the cold flow rate of the vortex tube, and d is the average isobaric specific heat of helium gas in the cooling chamber. i d0 is the diameter at the inlet of the pressurization section of the mixing heating chamber, and d0 is the diameter at the outlet of the pressurization section of the mixing heating chamber.

8. The cryogenic refrigeration system combining pressure reduction precooling and vortex tube according to claim 1, characterized in that: The power calculation formula for the compressor is as follows: Where Q is the cooling power required by the cooling chamber, and T 71 and T 72 The temperatures of the helium gas at the inlet and outlet of the cooling chamber are c, respectively. p7 The average isobaric specific heat of helium gas in the cooling chamber, μ is the cold flow rate of the vortex tube, k is the Boltzmann constant, R is the molar gas constant, and T is the average isobaric specific heat of helium gas in the cooling chamber. * π represents the total temperature of the helium gas at the outlet of the mixing heating chamber. * η is the boost ratio of the compressor, and η is the compressor efficiency.

9. A refrigeration method based on the low-temperature refrigeration system combining depressurization precooling and vortex tube as described in any one of claims 1-8, characterized in that: Helium is used as the working medium for cooling the equipment to be cooled. The helium is cooled to about 65K in a liquid nitrogen decompression precooling device, and then enters the vortex tube where it is separated into two streams of cold and hot helium. The cold helium has a temperature between 30K and 60K and enters the cooling chamber to cool the equipment to be cooled. After that, the cold helium is mixed with the hot helium in the mixing heating chamber. The temperature of the mixed helium rises to the allowable inlet temperature of the compressor and enters the compressor for pressurization before entering the liquid nitrogen decompression precooling device. This forms a refrigeration cycle with helium as the working medium.

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