Extremely low temperature environment obtaining device for inert mixed gas

Abstract

The invention discloses an extremely low temperature environment obtaining device for inert mixed gas. Comprising a compressor, a helium pipe, a refrigerating machine, a low-temperature temperature sensor, a heat insulation sleeve, a cooling cavity, a cooling vacuum valve, a pressure measuring cavity, a full-scale vacuum gauge, a gas mixing cavity, a gas extraction vacuum valve, a ventilation vacuum valve, a gas outlet vacuum valve, a molecular pump set, a mass flow controller, a connecting pipe and a gas cylinder. The low temperature obtaining device provided by the invention is high in reliability, easy to operate and relatively low in cost. The experiment process is divided into an inflation part and a cooling part, the difficulty of obtaining the low-temperature environment of the mixed gas is simplified, and the density of the mixed gas in different proportions can be obtained at low temperature. And the heat insulation sleeve is wrapped outside the cooling cavity, so that the loss of cooling capacity can be reduced to obtain a lower mixed gas temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of cryogenic engineering, and particularly to a device for obtaining an extremely low temperature environment for inert mixed gases. Background Art

[0002] In the field of extremely low temperatures, there is an increasing demand for new refrigerants with excellent performance. Helium-neon mixed gas is considered a promising extremely low temperature refrigerant due to its low theoretical minimum temperature and potential high refrigeration efficiency. Compared with traditional single-component refrigerants, helium-neon mixed gas may have higher energy efficiency and a wider temperature application range in some extremely low temperature applications. Therefore, in-depth exploration and research on it have important scientific and engineering values. To better apply helium-neon mixed gas as a refrigerant, it is crucial to accurately master its thermodynamic and physical properties at extremely low temperatures. And to obtain the thermophysical property data of helium-neon mixed gas at extremely low temperatures, a device that can stably and reliably provide an extremely low temperature environment is required first. However, there are still challenges in the prior art in effectively cooling helium-neon mixed gas and maintaining its stable state at extremely low temperatures, and specifically optimizing the device for such mixed gas research. Summary of the Invention

[0003] In order to meet the needs of researching helium-neon mixed gas as a new extremely low temperature refrigerant and solve the deficiencies in the prior art, the purpose of the present invention is to provide a device for obtaining an extremely low temperature environment for inert mixed gases. Based on a refrigerator and a compressor device, this device can efficiently and stably achieve an extremely low temperature environment through an innovative process of segmented gas filling and cooling, providing the necessary technical means for measuring the thermophysical properties of helium-neon mixed gas at extremely low temperatures, thereby laying a foundation for further developing and applying helium-neon mixed gas as an extremely low temperature refrigerant.

[0004] The present invention realizes the solution to the above technical problems through the following technical means:

[0005] A device for obtaining an extremely low temperature environment for inert mixed gases, comprising:

[0006] A test gas supply component for supplying test gas;

[0007] A gas mixing cavity connected to the test gas supply component, and one end of the gas mixing cavity is fixedly connected to an outlet vacuum valve;

[0008] A molecular pump group fixedly connected to an evacuation vacuum valve, and the other end of the evacuation vacuum valve is connected to the gas mixing cavity;

[0009] A pressure measurement cavity connected to one end of the outlet vacuum valve, one end of the pressure measurement cavity is fixedly connected to a full-range vacuum gauge, and the other end is connected to a cooling vacuum valve;

[0010] A cooling vacuum valve, the other end of which is fixedly connected to a cooling cavity;

[0011] A refrigerator, which is connected to a compressor through a helium pipe, and the cooling cavity and the refrigerator are fixedly connected through a flange and bolts.

[0012] As a further technical solution of the present invention, the test gas supply assembly includes:

[0013] A first gas cylinder, a first connecting pipe is fixedly connected to the gas outlet end thereof, a first mass flow controller is installed at one end of the first connecting pipe, a first ventilation vacuum valve is fixedly connected to one end of the first mass flow controller, and the other end of the first ventilation vacuum valve is connected to the mixing cavity;

[0014] A second gas cylinder, a second connecting pipe is fixedly connected to the gas outlet end thereof, a second mass flow controller is installed at one end of the second connecting pipe, a second ventilation vacuum valve is fixedly connected to one end of the second mass flow controller, and the other end of the second ventilation vacuum valve is connected to the mixing cavity.

[0015] As a further technical solution of the present invention, the refrigerator is a GM refrigerator, including a refrigerator motor part and a refrigerator cold head part, and the two are connected through a flange and bolts to form an integral refrigerator; the compressor is a helium compressor, and the helium compressor is connected to the refrigerator through the helium pipe, and the refrigerator cold head part is a cold source, which is located inside the cooling cavity.

[0016] As a further technical solution of the present invention, the outside of the cooling cavity is wrapped with a heat insulation sleeve, and the heat insulation sleeve uses aluminum silicate as a heat insulation material.

[0017] As a further technical solution of the present invention, it further includes a low-temperature temperature sensor, and the probe position of the low-temperature temperature sensor is fixed below the refrigerator cold head part, and can measure the gas temperature during the cooling process.

[0018] As a further technical solution of the present invention, the cooling vacuum valve, the air extraction vacuum valve, the air outlet vacuum valve, the first and second ventilation vacuum valves are all angle valves, and are all sealed through gaskets.

[0019] The beneficial effects achieved by the present invention:

[0020] (1) In the present invention, the inflation process and the cooling process are separated. First, a certain amount of mixed gas is introduced. The cooling cavity and the pressure measurement cavity form a closed space, and then the temperature of the mixed gas is reduced by a refrigerator and a compressor, which simplifies the difficulty of obtaining a low-temperature environment for the mixed gas. From a thermodynamics perspective, by separating the inflation process from the cooling process, the present invention aims to optimize the entropy change of the system and improve the energy utilization efficiency. In the traditional continuous inflation and cooling method, the continuously incoming high-temperature gas needs to be continuously cooled, which introduces additional heat load, increases the entropy generation of the system, and may lead to a reduction in the efficiency of the refrigeration cycle. In the present invention, a certain mass of mixed gas is pre-restricted in the closed cooling cavity and pressure measurement cavity to form a relatively stable thermodynamic system. Subsequently, an isochoric cooling process is performed on this closed system by a refrigerator and a compressor. This method avoids the heat fluctuations caused by continuous gas flow, enabling the refrigeration cycle to more effectively reduce the temperature of the gas in the cavity. In addition, for real gases, their equations of state deviate from the ideal gas behavior, especially under low-temperature and high-pressure conditions. Determining the amount and pressure of the gas in advance helps to more accurately predict and control its thermodynamic behavior during the cooling process, such as the phase transition point and the change in heat capacity, thereby more effectively achieving the required extremely low-temperature state.

[0021] (2) In the present invention, the introduction of a mass flow controller enables precise control of the number of moles of the inert mixed gas entering the system. According to the ideal gas law (PV = nRT), at a given temperature and volume, the density of the gas is directly related to the number of moles. By precisely adjusting the mass flow controller, the number of moles of the mixed gas entering the cooling cavity can be accurately controlled, thereby precisely controlling the gas density in the cavity. This is crucial for studying the physical and chemical properties of inert mixed gases at different densities. For example, in the study of low-temperature condensed matter physics, precisely controlling the number density of atoms or molecules is a prerequisite for achieving specific quantum states. In addition, the behavior of mixed gases with different components at low temperatures is affected by their partial molar volumes. Precisely controlling the flow rate ratio and total flow rate of each component helps to obtain a low-temperature mixture with a specific composition and density, thus meeting the requirements of different experiments.

[0022] (3) In the present invention, the cooling cavity is externally wrapped with a heat insulation sleeve, which can reduce the loss of cold energy to obtain a lower temperature of the mixed gas. The design principle of the heat insulation sleeve is to use materials with low thermal conductivity to hinder the transfer of heat. In the present invention, the heat insulation sleeve uses aluminum silicate as the heat insulation material. Aluminum silicate is an excellent refractory heat insulation material, with characteristics such as low thermal conductivity, high temperature resistance, and good chemical stability. In a low-temperature environment, aluminum silicate fibers can effectively reduce the transfer of heat, and its internal porous structure and fiber-interwoven network can significantly reduce solid heat conduction and gas heat convection. In addition, the aluminum silicate material also has a certain flexibility, which is easy to wrap around the outside of the cooling cavity to form a good heat insulation layer. By using the aluminum silicate heat insulation sleeve, the heat leakage from the surrounding environment to the cooling cavity can be effectively reduced, the load of the refrigerator can be reduced, and it is helpful to obtain a lower temperature of the mixed gas.

[0023] (4) In the present invention, the molecular pump group, as a high-vacuum pump, can effectively remove the residual gas molecules in the system, thereby significantly improving the purity of the introduced inert mixed gas. In low-temperature experiments, the presence of impurity gases may have unpredictable effects on the experimental results, such as changing the phase transition temperature of the mixed gas, etc. By pre-pumping the system to a high vacuum with the molecular pump group, the influence of these impurities can be minimized to ensure the cleanliness and controllability of the experimental environment, thereby improving the reliability and accuracy of the experimental data. At the same time, the extremely high vacuum degree that the molecular pump group can achieve effectively prevents the leakage of foreign gases and maintains the low-pressure environment of the system, which is crucial for obtaining and maintaining an extremely low-temperature environment because gases have lower thermal conductivity under low pressure, which helps to reduce heat transfer. Description of the Drawings

[0024] Figure 1 It is a schematic structural diagram of an extremely low-temperature environment obtaining device for inert mixed gases.

[0025] Figure 2 It is a result graph of the change curve of gas temperature over time.

[0026] Figure 3 It is a field physical picture of an extremely low-temperature environment obtaining device for inert mixed gases.

[0027] Annotation of reference numerals: 1 - compressor, 2 - helium pipe, 3 - motor part of the refrigerator, 4 - cold head part of the refrigerator, 5 - heat insulation sleeve, 6 - low-temperature temperature sensor, 7 - cooling cavity, 8 - cooling vacuum valve, 9 - full-range vacuum gauge, 10 - pressure measurement cavity, 11 - outlet vacuum valve, 12 - first molecular pump, 13 - second molecular pump, 14 - pumping vacuum valve, 15 - gas mixing cavity, 16 - first ventilation vacuum valve, 17 - first mass flow controller, 18 - first connecting pipe, 19 - first gas cylinder, 20 - second ventilation vacuum valve, 21 - second mass flow controller, 22 - second connecting pipe, 23 - second gas cylinder. Detailed implementation mode

[0028] The technical solution of the present invention will be described in detail below with reference to specific drawings.

[0029] Please refer to Figure 1 , this embodiment provides an extremely low temperature environment obtaining device for inert mixed gases, including:

[0030] A test gas providing component for providing test gas;

[0031] The gas mixing cavity 15 is connected to the test gas providing component, and one end of the gas mixing cavity 15 is fixedly connected to the outlet vacuum valve 11;

[0032] The molecular pump group is fixedly connected to the pumping vacuum valve 14, the other end of the pumping vacuum valve 14 is connected to the gas mixing cavity 15, and the molecular pump group is composed of a first molecular pump 12 and a second molecular pump 13;

[0033] The pressure measurement cavity 10 is connected to one end of the outlet vacuum valve 11, one end of the pressure measurement cavity 10 is fixedly connected to the full-range vacuum gauge 9, and the other end is fixedly connected to the cooling vacuum valve 8. The upper limit of the full-range vacuum gauge 9 is the atmospheric pressure; the full-range vacuum gauge 9 usually combines multiple sensing technologies, such as Pirani gauges and cold cathode ionization gauges, to cover a wide pressure range from high vacuum to atmospheric pressure. Its advantage is that it can monitor the pressure throughout the entire experimental process on one instrument, simplifying the operation, avoiding the trouble and potential errors of range switching, and can provide real-time system pressure information, which is crucial for judging the system state, controlling gas filling, and monitoring the cooling process, thereby improving the reliability of pressure data and the controllability of the experiment;

[0034] The cooling vacuum valve 8, the other end of which is fixedly connected to the cooling cavity 7;

[0035] The refrigerator is connected to the compressor 1 through the helium pipe 2, and the cooling cavity 7 is fixedly connected to the refrigerator through a flange and bolts.

[0036] In this embodiment, the test gas supply component includes:

[0037] A first gas cylinder 19, the outlet end of which is fixedly connected with a first connecting pipe 18. One end of the first connecting pipe 18 is provided with a first mass flow controller 17. One end of the first mass flow controller 17 is fixedly connected with a first ventilation vacuum valve 16, and the other end of the first ventilation vacuum valve 16 is connected to the gas mixing cavity 15;

[0038] A second gas cylinder 23, the outlet end of which is fixedly connected with a second connecting pipe 22. One end of the second connecting pipe 22 is provided with a second mass flow controller 21. One end of the second mass flow controller 21 is fixedly connected with a second ventilation vacuum valve 20, and the other end of the second ventilation vacuum valve 20 is connected to the gas mixing cavity 15.

[0039] In this embodiment, the refrigerator is a GM refrigerator, which includes a refrigerator motor part 3 and a refrigerator cold head part 4. The two are connected by a flange and bolts to form the whole refrigerator; the compressor 1 is a helium compressor. The helium compressor is connected to the refrigerator through the helium pipe 2. The refrigerator cold head part 4 is a cold source, which is located inside the temperature reduction cavity 7. The GM refrigerator (Gifford-McMahon Refrigerator) is a commonly used low-temperature refrigeration device, and its working principle is based on the Gifford-McMahon cycle. This cycle mainly includes four processes: compression, cooling, expansion and exhaust. First, high-pressure helium gas is precooled through a heat exchanger. Then, the high-pressure helium gas enters the expander and does work by expansion, causing its temperature to drop significantly. The expanded low-pressure helium gas flows back to the heat exchanger to cool the newly entered high-pressure helium gas. By repeating this cycle, the refrigerator cold head part 4 can reach an extremely low temperature. As the cold source of the present invention, it transfers the cold quantity to the mixed gas in the cavity through heat conduction, gradually reducing its temperature. The reason for choosing the GM refrigerator is that its structure is relatively simple, it runs reliably, can stably provide the required extremely low temperature, and is widely used in laboratory environments. The compressor 1 is a helium compressor. Helium is selected as the working medium of the refrigeration cycle mainly because helium has an extremely low boiling point (about 4.2K) and has good thermodynamic properties at low temperatures, such as a relatively high specific heat capacity and a low viscosity, which is conducive to efficient energy conversion and heat transfer in the refrigeration cycle. The main function of the compressor 1 is to provide high-pressure helium gas as the power source for the GM refrigerator cycle. Through the expansion work of the high-pressure helium gas, low temperature is generated. The helium pipe 2, as a key component connecting the compressor 1 and the refrigerator, mainly functions to transport high-pressure and low-pressure helium gas. In order to reduce heat loss and ensure the purity of helium gas, the helium pipe 2 is usually made of a material with good heat insulation performance and undergoes strict sealing treatment to ensure the efficiency and stability of the refrigeration cycle.

[0040] In this embodiment, the cooling cavity 7 is externally wrapped with a heat insulation sleeve 5, and the heat insulation sleeve 5 uses aluminum silicate as the heat insulation material, reducing the loss of cold quantity.

[0041] In this embodiment, it further includes a low-temperature temperature sensor 6, and the probe position of the low-temperature temperature sensor 6 is fixed below the cold head part 4 of the refrigerator, and can measure the gas temperature during the cooling process.

[0042] In this embodiment, the cooling vacuum valve 8, the pumping vacuum valve 14, the air outlet vacuum valve 11, and the first and second ventilation vacuum valves are all angle valves, and are all sealed by gaskets, reducing leakage.

[0043] The present invention also provides a method for obtaining a low-temperature environment of an inert gas mixture through the above device, including the following steps:

[0044] Step (1): Before using the measurement system, first perform leak detection. After ensuring that the leak rate of the system meets the requirements, open all the vacuum valves in the system, start the molecular pump group to pump the system to the base vacuum, and then close the pumping vacuum valve 14. The leak rate of the vacuum system is directly related to the purity of the mixed gas and the low-temperature maintenance ability. Any leakage will cause external gases (such as air and water vapor) to enter the system, pollute the inert mixed gas required for the experiment, and increase the thermal conductivity of the system, making it more difficult to maintain the low-temperature environment. Through strict leak detection, the leak rate of the system can be ensured to be controlled within an acceptable range.

[0045] Step (2): By setting the first and second mass flow controllers, gases can be introduced after setting the composition ratio of the mixed gas. The gases will be mixed evenly in the gas mixing cavity 15, and then introduced into the cooling cavity 5, causing the pressure in the cavity to continuously increase. The full-range vacuum gauge 9 can be used to measure the gas pressure introduced into the cooling cavity 5. After reaching the required pressure, close the air outlet vacuum valve 11. By precisely controlling the flow rate of the introduced gases through the first and second mass flow controllers, the component ratio of the mixed gas can be ensured to meet the experimental requirements. In the gas mixing cavity, the composition of the mixed gas will tend to be uniform after a certain period of time. Introducing the mixed gas into the cooling cavity and monitoring the pressure is to ensure that the gas density in the cavity reaches the preset value. According to the ideal gas law, a certain pressure and volume correspond to a certain number of gas molecules, thus determining the gas density, which is crucial for subsequent low-temperature experiments because the thermodynamic properties of the gas largely depend on its density.

[0046] Step (3): Run the compressor 1 and the refrigerator. The cooling capacity is continuously transferred in the cooling chamber 5, causing the temperature of the mixed gas to gradually decrease to the low temperature. After starting the compressor 1 and the refrigerator, the refrigeration system starts to work. Through the GM cycle, heat is transferred from the cold head part 4 of the refrigerator, causing the temperature of the cold head to gradually decrease. The mixed gas in the chamber transfers heat to the cold head through heat conduction and heat convection, causing its own temperature to gradually decrease. This process follows the second law of thermodynamics, where heat always spontaneously transfers from a high-temperature object to a low-temperature object. As time passes, when the system reaches thermal equilibrium, the temperature of the mixed gas will reach a stable extremely low value, thereby obtaining the required low-temperature environment. The function of the heat insulation sleeve 5 is to reduce the transfer of external heat to the cooling chamber 7, thereby reducing the load of the refrigeration system and helping to obtain a lower equilibrium temperature.

[0047] By the above method, a certain amount of extremely low-temperature mixed gas environment can be obtained.

[0048] To better illustrate the technical solution of the present invention, taking the mixed gas of helium and neon as an example, a low-temperature temperature sensor 6 is installed 2 cm below the cold head part 4 of the refrigerator to monitor the cooling process of the mixed gas with different gas ratios (helium to neon) and different initial gas pressures. The results of the curve showing the change in the gas temperature measured at the temperature sensor measurement point over time are as Figure 2 shown, and the on-site physical diagram of the system is as Figure 3 shown. The experimental data clearly demonstrates the ability of the device to obtain a low-temperature inert mixed gas environment, providing strong evidence for the effectiveness of the technical solution.

[0049] It should be noted that in this article, the term "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or device including a series of elements not only includes those elements but also includes other elements not explicitly listed, or elements inherent to such process, method, article, or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article, or device including that element.

[0050] The above is only the preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. An extremely low temperature environment obtaining device for inert mixed gases, characterized in that, Comprising: A test gas supply component for supplying test gas; A gas mixing cavity, which is connected to the test gas supply component, and one end of the gas mixing cavity is fixedly connected to an outlet vacuum valve; A molecular pump set, which is fixedly connected to a pumping vacuum valve, and the other end of the pumping vacuum valve is connected to the gas mixing cavity; A pressure measurement cavity, which is connected to one end of the outlet vacuum valve, one end of the pressure measurement cavity is fixedly connected to a full-range vacuum gauge, and the other end is fixedly connected to a cooling vacuum valve; The cooling vacuum valve, the other end of which is fixedly connected to a cooling cavity; A refrigerator, which is connected to a compressor through a helium pipe, and the cooling cavity is fixedly connected to the refrigerator through a flange and bolts.

2. The cryogenic environment obtaining device for inert mixed gas according to claim 1, characterized in that, The test gas supply component includes: A first gas cylinder, the outlet end of which is fixedly connected to a first connecting pipe, one end of the first connecting pipe is equipped with a first mass flow controller, one end of the first mass flow controller is fixedly connected to a first ventilation vacuum valve, and the other end of the first ventilation vacuum valve is connected to the gas mixing cavity; A second gas cylinder, the outlet end of which is fixedly connected to a second connecting pipe, one end of the second connecting pipe is equipped with a second mass flow controller, one end of the second mass flow controller is fixedly connected to a second ventilation vacuum valve, and the other end of the second ventilation vacuum valve is connected to the gas mixing cavity.

3. The device for obtaining an extremely low temperature environment for inert mixed gases according to claim 1, wherein The refrigerator is a GM refrigerator, including a refrigerator motor part and a refrigerator cold head part, which are connected by a flange and bolts to form the whole refrigerator; the compressor is a helium compressor, and the helium compressor is connected to the refrigerator through the helium pipe. The refrigerator cold head part is a cold source and is located inside the cooling cavity.

4. The device for obtaining an extremely low temperature environment for inert mixed gases according to claim 1, characterized in that, The outside of the cooling cavity is wrapped with a heat insulation sleeve.

5. An apparatus for obtaining an extremely low temperature environment for an inert mixed gas according to claim 4, characterized in that, The heat insulation sleeve uses aluminum silicate as the heat insulation material.

6. The cryogenic environment obtaining device for inert mixed gas according to claim 3, wherein, It also includes a low-temperature temperature sensor, and the probe position of the low-temperature temperature sensor is fixed below the refrigerator cold head part to measure the gas temperature during the cooling process.

7. An apparatus for obtaining an extremely low temperature environment for inert mixed gases according to claim 2, characterized in that, The cooling vacuum valve, the pumping vacuum valve, the outlet vacuum valve, the first and second ventilation vacuum valves are all angle valves and are all sealed by gaskets.

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