Automatic liquid nitrogen supply system for low-temperature test and recovery self-circulation device

Abstract

The invention belongs to the technical field of low-temperature engineering and electronic testing, and particularly discloses an automatic liquid nitrogen supply system for a low-temperature test, which comprises a liquid storage tank, a communicating pipeline, a liquid level sensor and an intelligent control module, the liquid storage tank is used for containing liquid nitrogen; one end of the communicating pipeline is connected to the liquid storage tank, and the other end of the communicating pipeline is connected to the testing tank; the communicating pipeline is sequentially provided with an electromagnetic valve and a mass flow controller in series in the liquid nitrogen flowing direction. The automatic liquid nitrogen supply system for the low-temperature test, provided by the invention, has the advantages of high automation degree, reduction of manual intervention, high control precision and high data reliability and traceability through the structural design and control logic of the system, and the automatic liquid nitrogen supply system has the advantages of high automation degree and reduction of manual intervention. And the safety risk caused by manual intervention is also reduced.

Description

Technical Field

[0001] This invention relates to the fields of cryogenic engineering and electronic testing technology, and in particular to an automatic liquid nitrogen replenishment system and a self-circulating recovery device for cryogenic testing. Background Technology

[0002] Applications in aerospace, polar exploration, and cryogenic quantum devices require rigorous cryogenic testing to verify their adaptability and reliability in extreme environments. Cryogenic testing uses liquid nitrogen as the cooling medium and relies on a Dewar container to maintain the cryogenic environment; however, existing liquid nitrogen replenishment methods have the following significant drawbacks.

[0003] High dependence on manual intervention: The existing replenishment method requires experimental personnel to be on duty at all times, continuously monitor the liquid nitrogen level in the test Dewar tank, and judge the replenishment time based solely on experience and manually complete the replenishment operation. In long-term continuous tests, this mode not only consumes a lot of manpower, but is also very prone to untimely replenishment (liquid level too low) or misjudgment of replenishment time due to human error such as personnel fatigue and judgment bias, which may lead to test interruption.

[0004] Poor accuracy of liquid level control: The flow rate and timing of manually pouring liquid nitrogen are difficult to control precisely, which can easily lead to "over-compensation" (liquid level overshoot, causing violent vaporization and thermal shock) or "under-compensation" (liquid level too low, temperature rise), thus disrupting the stability of the test environment.

[0005] Significant safety hazards exist: Laboratory personnel frequently come into contact with cryogenic liquids (liquid nitrogen temperature range, approximately -196°C) and containers, posing a serious risk of frostbite. Furthermore, there is a risk of physical damage if the Dewar flask experiences abnormal pressure or structural failure.

[0006] In summary, existing liquid nitrogen replenishment methods suffer from high reliance on manual intervention, poor accuracy in liquid level control, and significant safety hazards. Summary of the Invention

[0007] This invention provides an automatic liquid nitrogen replenishment system for cryogenic testing, which can solve the problems of high dependence on manual intervention, poor liquid level control accuracy, and prominent safety hazards in existing liquid nitrogen replenishment methods.

[0008] In a first aspect, the present invention provides an automatic liquid nitrogen replenishment system for cryogenic testing, comprising: A storage tank for containing liquid nitrogen; A connecting pipe, one end of which is connected to a storage tank and the other end of which is connected to a test tank; The connecting pipeline is equipped with a solenoid valve and a mass flow controller connected in series along the direction of liquid nitrogen flow. A liquid level sensor, used to detect the liquid level data inside the test tank; The intelligent control module is connected to the solenoid valve and the mass flow controller respectively, and is configured to execute the following control logic based on the liquid level data transmitted by the liquid level sensor: When the liquid level is below the first threshold, the intelligent control module controls the solenoid valve to open and controls the mass flow controller to replenish the liquid nitrogen flowing out of the storage tank to the test tank according to the preset flow rate. When the liquid level data value is higher than the second threshold, the intelligent control module controls the solenoid valve to close, stopping the replenishment of liquid nitrogen into the test tank; The second threshold is greater than the first threshold.

[0009] This invention provides an automatic liquid nitrogen replenishment system for cryogenic testing, which, compared to existing technologies, has, but is not limited to, the following beneficial effects: In this automatic liquid nitrogen replenishment system for cryogenic testing, the storage tank constitutes the liquid nitrogen storage component, providing a stable long-term supply of liquid nitrogen for continuous replenishment during cryogenic testing. The connecting pipeline serves as the liquid nitrogen delivery channel, establishing a fluid communication path between the storage tank and the test tank, ensuring smooth delivery of liquid nitrogen from the storage tank to the test tank. The solenoid valve controls the on / off operation of the liquid nitrogen replenishment process, controlled by signals from the intelligent control module. The mass flow controller precisely regulates the liquid nitrogen flow rate, maintaining a preset replenishment rate based on instructions from the intelligent control module. A level sensor, installed inside the test tank, collects real-time liquid nitrogen level data and transmits it to the intelligent control module. The intelligent control module is the core control component of the system. By receiving liquid level data transmitted from the liquid level sensor, the system sends control signals to the solenoid valve and mass flow controller according to preset control logic, thereby achieving automated control of the replenishment process. Simultaneously, it can record system operating parameters to ensure data traceability. The test tank, as the replenishment object of this system, is used to construct the low-temperature environment required for cryogenic testing and to house the devices under test.

[0010] This invention provides an automatic liquid nitrogen replenishment system for cryogenic testing. During the cryogenic test, a liquid level sensor continuously monitors the liquid nitrogen level in the test tank and transmits the data to an intelligent control module in real time. The data processing unit of the intelligent control module analyzes the received liquid level data in real time and compares it with preset first and second thresholds. When the detected liquid level is lower than the first threshold, it indicates that the liquid nitrogen in the test tank is insufficient and replenishment needs to be initiated. At this time, the intelligent control module sends an opening signal to the solenoid valve through the signal output unit and simultaneously sends a preset flow rate signal to the mass flow controller. Upon receiving the opening signal, the solenoid valve opens rapidly, and the liquid nitrogen in the storage tank enters the connecting pipeline. After flowing through the solenoid valve, under the regulation of the mass flow controller, it flows steadily to the test tank at a preset flow rate, thus achieving liquid nitrogen replenishment. During the replenishment process, the liquid level sensor continuously monitors changes in the liquid level, and the intelligent control module continuously receives and analyzes the data. When the detected liquid level data exceeds the second threshold, it indicates that the amount of liquid nitrogen in the test tank meets the experimental requirements. The intelligent control module immediately sends a shut-off signal to the solenoid valve, which quickly closes upon receiving the signal, stopping the replenishment of liquid nitrogen into the test tank and completing one automatic replenishment cycle. Through the above structural design and control logic, it has the advantages of high automation, reduced manual intervention, high control precision, and strong data reliability and traceability. Due to its high degree of automation and reduced manual intervention, it also reduces the safety risks caused by manual intervention.

[0011] Furthermore, the first threshold is 20% of the effective volume of the test tank; The second threshold is 80% of the effective volume of the test tank.

[0012] Furthermore, the liquid level sensor is any one or more of a capacitive liquid level sensor, an ultrasonic liquid level sensor, and a high-temperature superconducting liquid level sensor.

[0013] Furthermore, the high-temperature superconducting liquid level sensor includes a first substrate, a ReBCO tape layer, and a second substrate arranged sequentially from top to bottom; Electrodes are provided at both ends of the upper surface and both ends of the lower surface of the ReBCO tape layer.

[0014] Furthermore, the automatic liquid nitrogen replenishment system for low-temperature testing also includes a temperature sensor, which is located inside the test tank. The temperature sensor is used to detect the ambient temperature inside the test tank and send the ambient temperature to the intelligent control module. The intelligent control module is used to adjust the liquid nitrogen flow rate based on the difference between the ambient temperature and the liquid nitrogen temperature range. When the difference between the ambient temperature and the liquid nitrogen temperature range is greater than 5°C, the intelligent control module controls the mass flow controller to reduce the liquid nitrogen output flow rate.

[0015] Furthermore, the automatic liquid nitrogen replenishment system for cryogenic testing also includes a pressure sensor and an emergency shut-off valve. The pressure sensor is used to detect the pressure inside the test tank in real time and transmit it to the intelligent control module. The emergency shut-off valve is located on the connecting pipeline and is signal-connected to the intelligent control module. When the pressure inside the test tank exceeds 0.15 MPa, the intelligent control module controls the emergency shut-off valve to close, stopping the supply of liquid nitrogen to the test tank.

[0016] Furthermore, a one-way valve is also provided on the connecting pipeline, and the conduction direction of the one-way valve is consistent with the flow direction of liquid nitrogen; The one-way valve is located between the mass flow controller and the test tank.

[0017] Secondly, the present invention also provides a recycling device, including a test tank and an intelligent automatic liquid nitrogen replenishment system for cryogenic testing provided in the first aspect of the present invention, wherein the test tank is provided with a sample rack for placing test devices.

[0018] Furthermore, the test container is also equipped with a lifting device, which is driven and connected to the sample rack.

[0019] Furthermore, the recycling self-circulation device also includes a nitrogen cylinder; The outlet of the nitrogen cylinder is connected to the storage tank via a high-pressure gas pipeline, and the high-pressure gas pipeline is also equipped with an adsorber for purifying nitrogen. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram of an automatic liquid nitrogen replenishment system for cryogenic testing provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a recycling self-circulation device provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a heat exchanger for a self-circulating recycling device provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of the fins of a recycling self-circulating device provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the structure of the high-temperature superconducting liquid level sensor provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the structure of a high-temperature superconducting liquid level sensor provided in another embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures: 1. Storage tank; 2. Connecting pipeline; 3. Emergency shut-off valve; 4. Solenoid valve; 5. Mass flow controller; 6. Check valve; 7. Temperature sensor; 8. Pressure sensor; 9. Liquid level sensor; 10. Test tank; 11. Sample rack; 12. Intelligent control module; 13. Lifting device; 100. Heat exchanger; 200. Recovery air bag; 300. Gas compression pump; 400. Nitrogen cylinder; 500. Liquefaction device; 600. Fin; 700. First side; 800. Second side; 900. Adsorber; 701. Raised arc segment; 702. Transition arc segment; 101. ReBCO strip layer; 102. First substrate; 103. Second substrate; 104. First insulation layer; 105. Second insulation layer; 106. Hole; 201. Third insulation layer. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings showing multiple embodiments according to this application. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments described in this application without creative effort will fall within the scope of protection of this application.

[0023] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing specific embodiments only and is not intended to limit this application; the terms "comprising," "including," "having," "containing," etc., in the description, claims, and accompanying drawings of this application are open-ended terms. Therefore, "comprising," "including," or "having" refers to, for example, a method or apparatus having one or more steps or elements, but is not limited to having only these one or more elements. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0024] In the description of this invention, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0026] It should be emphasized that when the term "comprising / including" is used in this specification, it is used to explicitly indicate the presence of the stated feature, integer, step, or component, but does not exclude the presence or addition of one or more other features, integers, steps, parts, or groups of features, integers, steps, or parts.

[0027] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, B and / or C can represent: B existing alone, B and C existing simultaneously, or C existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0028] like Figure 1 As shown in the figure, an automatic liquid nitrogen replenishment system for cryogenic testing is provided in this embodiment of the invention. The system specifically includes a liquid storage tank 1, a connecting pipeline 2, a liquid level sensor 9, and an intelligent control module 12. The liquid storage tank 1 is used to contain liquid nitrogen; one end of the connecting pipe 2 is connected to the liquid storage tank 1, and the other end of the connecting pipe 2 is connected to the test tank 10; and along the liquid nitrogen flow direction from the liquid storage tank 1 to the test tank 10, a solenoid valve 4 and a mass flow controller 5 are connected in series on the connecting pipe 2. Liquid level sensor 9 is used to detect liquid level data inside test tank 10; The intelligent control module 12 is connected to the solenoid valve 4 and the mass flow controller 5 respectively, and the intelligent control module 12 is configured to execute the following control logic based on the liquid level data transmitted by the liquid level sensor 9: When the liquid level is lower than the first threshold, the intelligent control module 12 controls the solenoid valve 4 to open and controls the mass flow controller 5 to replenish the liquid nitrogen flowing out of the storage tank 1 to the test tank 10 according to the preset flow rate. When the liquid level data is higher than the second threshold, the intelligent control module 12 controls the solenoid valve 4 to close, stopping the replenishment of liquid nitrogen into the test tank 10. The second threshold is greater than the first threshold.

[0029] Specifically, the storage tank 1, which constitutes the liquid nitrogen storage component of the automatic liquid nitrogen replenishment system, is used to stably contain liquid nitrogen for a long period of time, providing a continuous liquid nitrogen source for cryogenic experiments. It typically employs a container structure with cryogenic insulation properties, which can effectively reduce liquid nitrogen evaporation loss and ensure continuous replenishment.

[0030] Connecting pipe 2 serves as the liquid nitrogen transport channel, establishing a fluid connection between the storage tank 1 and the test tank 10, allowing the liquid nitrogen in the storage tank 1 to be smoothly transported to the test tank 10. Specifically, connecting pipe 2 is a vacuum-insulated transport pipe, designed with insulating materials to effectively reduce heat transfer during transport and minimize vaporization loss, thereby ensuring that the liquid nitrogen is delivered to the test tank in a relatively stable state and with high purity, meeting the requirements for liquid nitrogen quality and stability in cryogenic testing.

[0031] Solenoid valve 4, as the on / off control component for liquid nitrogen replenishment, is controlled by the signal from intelligent control module 12 to realize the opening and closing of the liquid nitrogen replenishment process. The valve can be opened and closed by switching on and off the electrical signal, with precise response and rapid action, providing basic on / off control function for automated replenishment.

[0032] The mass flow controller 5, as a precise regulating component for liquid nitrogen flow, is used to stabilize the liquid nitrogen supply flow rate at a preset value according to the instructions of the intelligent control module 12. It can also monitor and adjust the liquid nitrogen flow rate through the pipeline in real time, ensuring the stability and accuracy of the flow rate during the supply process and avoiding deviations in liquid level control.

[0033] The liquid level sensor 9, as a liquid level detection component, is installed inside the test tank 10 to collect real-time liquid nitrogen level data within the test tank 10 and transmit the collected liquid level data to the intelligent control module 12. This provides the core data basis for the intelligent control module 12 to determine the replenishment timing and execute control logic.

[0034] The intelligent control module 12 serves as the core control component of the system. By receiving liquid level data transmitted from the liquid level sensor 9, it sends control signals to the solenoid valve 4 and the mass flow controller 5 according to preset control logic, thereby achieving automated control of the replenishment process. At the same time, it can record system operating parameters to ensure data traceability.

[0035] Test container 10, serving as the resupply target of this system, is used to construct the cryogenic environment required for cryogenic testing and to house the device under test. This system maintains the stability of the internal cryogenic environment of test container 10 by precisely supplying liquid nitrogen into it.

[0036] The automatic liquid nitrogen replenishment system for cryogenic testing provided in this embodiment of the invention achieves automated and precise liquid nitrogen replenishment through the coordinated operation of a storage tank 1, connecting pipeline 2, various valves, a level sensor 9, and an intelligent control module 12. Specifically, the storage tank 1 can be a Dewar flask or a dedicated cryogenic storage tank that meets cryogenic storage standards. Its volume can be selected according to the length of the test cycle to meet the liquid nitrogen requirements of cryogenic tests of different durations. The connecting pipeline 2 can be made of cryogenic-resistant metals such as stainless steel or copper alloy. The diameter of the pipeline can be matched according to the preset replenishment flow rate to ensure smooth liquid nitrogen delivery. One end of the connecting pipeline 2 can be sealed to the outlet of the storage tank 1 through flange connection, welding, or quick coupling, and the other end can also be sealed to the inlet of the test tank 10 to ensure the sealing of the entire delivery path and prevent liquid nitrogen leakage.

[0037] In addition, along the liquid nitrogen flow direction from the storage tank 1 to the test tank 10, a solenoid valve 4 and a mass flow controller 5 are connected in series on the connecting pipeline 2. The advantage of this series sequence is that the solenoid valve 4 is used for on / off control during the routine replenishment process, realizing the regular start and stop of replenishment; the mass flow controller 5 is located after the solenoid valve 4, and can precisely adjust the flow rate of liquid nitrogen after the solenoid valve 4 is opened, ensuring that the replenishment flow rate meets the preset requirements. The above-mentioned valves and controllers can be fixed to the connecting pipeline 2 by bolt connection or flange connection, and the connection parts can be sealed with cryogenic gaskets to prevent liquid nitrogen leakage.

[0038] The liquid level sensor 9 is installed at a preset position inside the test tank 10. Its installation height should ensure that it can completely detect the liquid level change range from the first threshold to the second threshold inside the test tank 10. The liquid level sensor 9 can be connected to the test tank 10 by fixing with a bracket or mounting with a flange, collect liquid level data in real time, and transmit the data to the intelligent control module 12 via wired or wireless communication.

[0039] The intelligent control module 12 can be installed in the control box at the test site or in a remote control room. It establishes signal connections with the solenoid valve 4, the mass flow controller 5, and the level sensor 9 via signal cables or wireless communication modules. The intelligent control module 12 integrates a data processing unit, a signal output unit, and a data storage unit. The data processing unit receives and analyzes the level data transmitted by the level sensor 9 and determines whether to open or close the supply based on preset control logic. The signal output unit sends corresponding control signals to each actuator (solenoid valve 4, mass flow controller 5). The data storage unit records real-time operating information such as level data, valve status, and flow parameters, providing data support for subsequent data analysis and traceability.

[0040] The core working process of this system is based on the control logic of the intelligent control module 12, as detailed below: During the cryogenic test, the liquid level sensor 9 continuously monitors the liquid nitrogen level in the test tank 10 and transmits the data to the intelligent control module 12 in real time. The data processing unit of the intelligent control module 12 analyzes the received liquid level data in real time and compares it with a preset first threshold and a preset second threshold. When the liquid level is detected to be lower than the first threshold, it indicates that the liquid nitrogen in the test tank 10 is insufficient and replenishment needs to be initiated. At this time, the intelligent control module 12 sends an opening signal to the solenoid valve 4 through the signal output unit, and simultaneously sends a preset flow rate signal to the mass flow controller 5. After receiving the opening signal, the solenoid valve 4 opens rapidly, and the liquid nitrogen in the storage tank 1 enters the connecting pipe 2. After flowing through the solenoid valve 4, under the regulation of the mass flow controller 5, it flows steadily to the test tank 10 at a preset flow rate, thus achieving liquid nitrogen replenishment. During the replenishment process, the liquid level sensor 9 continuously monitors the liquid level change, and the intelligent control module 12 continuously receives and analyzes the data. When the liquid level data is detected to be higher than the second threshold, it indicates that the amount of liquid nitrogen in the test tank 10 has met the test requirements. The intelligent control module 12 immediately sends a closing signal to the solenoid valve 4. After receiving the signal, the solenoid valve 4 quickly closes, stopping the replenishment of liquid nitrogen into the test tank 10, thus completing one automatic replenishment cycle.

[0041] The automatic liquid nitrogen replenishment system for cryogenic testing provided in this invention achieves the following technical effects through the above-mentioned structural design and control logic: 1. High degree of automation, reducing manual intervention: The system can completely replace manual inspection and operation. Through the synergistic effect of the liquid level sensor 9 and the intelligent control module 12, the replenishment process is fully automated, supporting continuous testing for several days without manual intervention, significantly reducing labor costs and eliminating human error; 2. High control precision: The liquid level sensor 9 detects liquid level data in real time, and the mass flow controller 5 precisely adjusts the replenishment flow rate. At the same time, by reasonably setting the first threshold and the second threshold, high-precision control of the liquid level is achieved, fully meeting the demanding requirements of high-end cryogenic testing; 3. Strong data reliability and traceability: The intelligent control module 12 can record all operating parameters such as liquid level data, valve status, and flow parameters throughout the process, supporting historical data query and analysis. Test results are traceable and reproducible, and can be synchronized to the host computer for data analysis, fault diagnosis, and performance optimization; 4. Multiple safety protections and high reliability: By installing a solenoid valve 4 on the connecting pipe 2, the safety of the experimental environment is significantly improved. Thus, this system effectively solves many shortcomings of existing technologies, providing a reliable liquid nitrogen supply guarantee for the smooth conduct of high-end cryogenic experiments.

[0042] like Figure 1As shown, in some embodiments of the present invention, the first threshold is 20% of the effective volume of the test tank 10; the second threshold is 80% of the effective volume of the test tank 10.

[0043] In practical applications, the first threshold refers to the critical liquid level standard that triggers the start of liquid nitrogen replenishment. This can be quantified using the percentage of the effective volume of the test tank 10. The purpose is to provide the system with a clear and unified basis for determining the start of replenishment, avoiding insufficient liquid nitrogen due to late replenishment. The second threshold refers to the critical liquid level standard that triggers the cessation of liquid nitrogen replenishment. This is also quantified using the percentage of the effective volume, aiming to prevent excessive liquid nitrogen due to over-replenishment by providing a clear cessation determination.

[0044] Setting the first and second thresholds as a fixed ratio of the effective volume of the test tank 10 ensures the rationality of the replenishment timing: setting the first threshold to 20% avoids insufficient liquid nitrogen due to late replenishment, which could cause the temperature inside the test tank 10 to rise and disrupt the stability of the test environment; setting the second threshold to 80% avoids excessive liquid nitrogen due to over-replenishment, which could cause violent vaporization of liquid nitrogen, resulting in overpressure or thermal shock, while also reserving sufficient gas phase space for the normal evaporation of liquid nitrogen.

[0045] Specifically, this solution constructs a precise and controllable closed-loop liquid level control mechanism by pre-setting a first and a second quantified threshold in the intelligent control module 12. The first threshold is set at 20% of the effective volume of the test tank 10. When the liquid level data detected by the liquid level sensor 9 is lower than this threshold, it indicates that the amount of liquid nitrogen in the test tank 10 can no longer maintain a stable low-temperature test environment. The intelligent control module 12 immediately triggers the replenishment start logic, controls the solenoid valve 4 to open, and adjusts the flow rate to the preset speed through the mass flow controller 5 to ensure timely replenishment of liquid nitrogen. The second threshold is set at 80% of the effective volume of the test tank 10. When the liquid level data is higher than this threshold, it indicates that the amount of liquid nitrogen in the test tank 10 has met the test requirements. The intelligent control module 12 triggers the replenishment stop logic, controls the solenoid valve 4 to close, and terminates the replenishment process. This method of setting quantified thresholds frees the determination of replenishment timing from subjective experience dependence, realizes standardized control, and, together with the liquid level sensor 9, mass flow controller 5, and solenoid valve 4, forms a complete control process of "detection-determination-execution".

[0046] like Figure 1 As shown, in some embodiments of the present invention, the second threshold is a range value, the range of which is 75%–79%; When the liquid level is higher than 80% of the effective volume of test tank 10, the amount of liquid nitrogen in test tank 10 meets the test requirements.

[0047] In practical applications, the second threshold is set to a range of 75% to 79%, which is a reasonable range determined by comprehensively considering the effective volume of the test tank 10, the vaporization and expansion characteristics of liquid nitrogen, and the safety redundancy requirements of the test. This range not only ensures the sufficient amount of liquid nitrogen required for the test, but also reserves a safe buffer space for liquid level fluctuations, avoiding the control rigidity problem caused by a single fixed threshold.

[0048] In practical applications, when the liquid level exceeds 78% of the range, the intelligent control module 12 can control the solenoid valve 4 to close. 78% serves as the specific threshold for triggering the closure of the solenoid valve 4, representing the optimal safety control point within this range. The purpose is to terminate replenishment early when the liquid level approaches the upper limit, preventing liquid nitrogen from overflowing or causing a sudden increase in tank pressure due to subsequent vaporization and expansion. The intelligent control module 12 controls the solenoid valve 4 to close based on this threshold, implementing a liquid level upper limit protection mechanism. The aim is to achieve precise termination of liquid nitrogen replenishment through refined threshold settings, ensuring safe system operation.

[0049] Specifically, the solution improves the precise control system for the upper limit of the liquid level by optimizing the second threshold to a range of 75%–79% and clarifying the shutdown trigger condition at 78%. During operation, the liquid level sensors (capacitive and ultrasonic) continuously collect liquid nitrogen level data in the test tank 10 and transmit it to the intelligent control module 12. The intelligent control module 12 compares the effective liquid level data with the second threshold range of 75%-79% and the shut-off threshold of 78% in real time. When the liquid level data is between 75% and 78%, the system maintains normal replenishment or gradually reduces the replenishment flow rate. When the liquid level data is higher than 78%, the intelligent control module 12 immediately sends a shut-off signal to the solenoid valve 4. The solenoid valve 4 quickly closes the pipeline, terminating the liquid nitrogen replenishment. At this time, the small amount of liquid nitrogen still in the pipeline flows into the test tank 10 under the action of inertia, and the liquid level can be stabilized at about 80% of the effective volume of the test tank 10. This effectively offsets the effects of detection delay and flow inertia, completely solves the liquid level overshoot problem caused by "over-replenishment", avoids the risks of violent vaporization of liquid nitrogen, overpressure and thermal shock caused by overshoot, and ensures the stability of the low temperature test environment in the test tank 10.

[0050] This design, which combines a range threshold with a precise shut-off point, avoids the problem of a single threshold potentially triggering the shut-off due to liquid level fluctuations, while ensuring that the liquid level does not exceed the limit through 78% of the precise control points.

[0051] Through the above technical solution, the range-based setting of the second threshold improves the adaptability and fault tolerance of the liquid level control. The 75%-79% range provides flexible space for liquid level adjustment under different experimental scenarios; the precise 78% shut-off threshold specifically addresses the safety protection issue when the liquid level is close to the upper limit, effectively preventing safety risks such as liquid nitrogen overflow and sudden pressure rise. The precise shut-off control implemented by the intelligent control module 12 based on this setting ensures sufficient liquid nitrogen for the experiment while avoiding safety hazards caused by over-supply, further improving the precision of liquid nitrogen supply control and system operational safety, and providing more accurate liquid level assurance for the stable conduct of cryogenic experiments.

[0052] like Figure 1 , Figure 5 , Figure 6 As shown, in some embodiments of the present invention, the liquid level sensor 9 is a high-temperature superconducting liquid level sensor, which includes a first substrate 102, a ReBCO tape layer 101 and a second substrate 103 arranged sequentially from top to bottom, wherein electrodes are provided at both ends of the upper surface and both ends of the lower surface of the ReBCO tape layer. Both the first substrate 102 and the second substrate 103 can be one or more of the following: copper layer, copper-silver multilayer, copper and other conductive composite layer; Several holes 106 are also provided on the first base 102 along its length.

[0053] In the liquid level measurement of high-temperature superconducting liquid level sensors, the core of its operation is the high-temperature superconducting zero-resistance characteristic of ReBCO tape layer. When the temperature of the ReBCO tape drops below its critical temperature, the material enters a superconducting state and exhibits zero resistance. When the temperature is above the critical temperature, the material is in a non-superconducting state and has normal resistance.

[0054] Because the critical temperature of ReBCO tape (i.e., the transition temperature of 89K) is typically higher than the liquid nitrogen temperature (77K), ReBCO tape maintains a superconducting state at the liquid nitrogen temperature range (77K). Therefore, the portion of the ReBCO tape layer immersed in liquid nitrogen will trigger superconductivity, while the unimmersed portion will remain in a non-superconducting state.

[0055] Based on this, since electrodes are provided at both ends of the upper surface and both ends of the lower surface of the ReBCO tape layer, the following functions can be achieved through these electrodes: first, to apply a stable working voltage to the ReBCO tape layer; second, to collect the voltage signals at both ends of the ReBCO tape layer in real time, and to transmit the signals to the intelligent control module 12 for resistance value conversion (Ohm's law).

[0056] Therefore, when the sensor is placed inside the test tank 10, a differentiated state of submerged superconductivity and above-liquid non-superconductivity will be formed: The portion of the ReBCO tape layer submerged below the liquid surface enters a superconducting state due to the cryogenic environment of liquid nitrogen, resulting in zero resistance. The portion of the ReBCO tape above the liquid surface that is not submerged is in a non-superconducting state at room temperature (or above the critical temperature) and has electrical resistance.

[0057] This differential state means that the overall resistance value of the sensor is directly related to the liquid level—the higher the liquid level, the longer the submerged superconducting part, and the smaller the total resistance; the lower the liquid level, the longer the unsubmerged non-superconducting part, and the greater the total resistance.

[0058] Based on the above, after the intelligent control module 12 receives the voltage signal collected by the electrode, it calculates the total resistance value of the sensor and then, according to the preset correspondence between the resistance value and the liquid level height, it can deduce the current liquid level data in the test tank 10. Because the resistance of the high-temperature superconducting tape ReBCO differs greatly between its superconducting and non-superconducting (zero resistance) states, even a small change in liquid level will trigger significant feedback in resistance and voltage. Therefore, this high-temperature superconducting liquid level sensor is not only suitable for liquid level testing in low-temperature environments but also possesses detection sensitivity far exceeding that of traditional liquid level sensors.

[0059] like Figure 1 As shown, in some embodiments of the present invention, at least one side of the ReBCO tape layer 101 is provided with an insulating layer.

[0060] Specifically, the side of the ReBCO tape layer 101 that is close to the first substrate 102 is marked as side A, and the side of the ReBCO tape layer 101 that is close to the second substrate 103 is marked as side B. An insulating layer is provided on side A and / or side B.

[0061] like Figure 5 As shown, in some embodiments of the present invention, a first insulating layer 104 and a second insulating layer 105 may be provided on the A and B surfaces of the ReBCO tape layer 101, respectively, for insulating isolation between the tape layer and the substrate.

[0062] like Figure 6 As shown, in some embodiments of the present invention, a third insulating layer 201 may be provided on surface A of the ReBCO tape layer 101 for insulating isolation between the ReBCO tape layer 101 and the first substrate 102.

[0063] Furthermore, the ReBCO tape layer 101 has two electrodes on each side of the side closest to the first substrate 102, which are used to apply a stable working voltage to the ReBCO tape layer and to collect the voltage signals at both ends of the ReBCO tape layer in real time.

[0064] In some embodiments of the present invention, an insulating layer may be provided on the B surface of the ReBCO tape layer 101 for insulating isolation between the ReBCO tape layer 101 and the second substrate 103.

[0065] Furthermore, the ReBCO tape layer 101 has two electrodes on each side near the second substrate 103, which are used to apply a stable working voltage to the ReBCO tape layer and to collect the voltage signals at both ends of the ReBCO tape layer in real time.

[0066] In some embodiments, an insulating layer is provided to completely cover the ReBCO tape layer 101, preventing it from being exposed to environments such as air, liquid nitrogen, and moisture, thus avoiding performance degradation caused by possible hydrolysis of the ReBCO tape layer 101. In some embodiments, the insulating layer may be aluminum oxide, aluminum nitride, silicon nitride, silicon oxide, silicon oxynitride, epoxy resin, polyimide, etc.

[0067] In some embodiments, a plurality of holes are also formed on the substrate along its length to allow liquid nitrogen to quickly conduct cold energy to the ReBCO tape layer, causing a rapid transition between the superconducting and non-superconducting states, thereby further improving the sensitivity of the liquid level sensor.

[0068] like Figure 1 As shown, in some embodiments of the present invention, the liquid level sensor 9 may also be a capacitive liquid level sensor and / or an ultrasonic liquid level sensor. Specifically, the liquid level sensor 9 includes a capacitive liquid level sensor and an ultrasonic liquid level sensor.

[0069] In practical applications, capacitive level sensors are devices that detect liquid levels based on the principle of capacitance change. They calculate the liquid nitrogen level by detecting changes in capacitance between the sensor probe and the inner wall of the test tank 10. They are characterized by low-temperature resistance and strong anti-interference capabilities, aiming to provide stable liquid level detection data for the system. Ultrasonic level sensors, on the other hand, are devices that detect liquid levels based on the principle of ultrasonic wave reflection. They calculate the distance to the liquid nitrogen surface by emitting and receiving reflected ultrasonic signals, thus obtaining the liquid level height. They offer the advantage of non-contact detection, avoiding performance loss caused by direct contact with cryogenic liquid nitrogen. Their purpose is to complement capacitive level sensors and improve the redundancy of the detection system.

[0070] Specifically, this scheme constructs a dual-sensor redundant detection system by installing a capacitive liquid level sensor and an ultrasonic liquid level sensor in parallel within the test tank 10. During operation, the two sensors synchronously collect liquid nitrogen level data within the test tank 10 in real time and transmit their respective detection data synchronously to the intelligent control module 12. The intelligent control module 12 cross-validates the two sets of data. If the difference between the two sets of data is within a preset error range, the detection data is deemed valid, and the average value is used as the final liquid level data for subsequent control logic. If the difference between the two sets of data exceeds the preset error range, at least one sensor is deemed faulty, and the system immediately issues an alarm signal. Simultaneously, the system ensures temporary stability of the test based on historical data trends and preset safety thresholds. This dual-sensor collaborative detection design not only compensates for potential detection blind spots or performance defects of a single sensor but also improves the reliability of the liquid level data through a cross-validation mechanism, while also possessing fault self-diagnosis capabilities.

[0071] Through the above technical solution, during the cryogenic test, dual sensors can continuously and synchronously monitor the liquid nitrogen level and perform data cross-validation, effectively avoiding level detection failure caused by the malfunction of a single sensor and ensuring the real-time nature and accuracy of the level data. This not only provides reliable data support for the precise control of the intelligent control module and ensures the rationality of liquid nitrogen replenishment timing and flow rate adjustment, but also enables timely detection and alarm of sensor malfunctions, reducing the risk of test interruption or environmental loss of control.

[0072] like Figure 1 As shown, in some embodiments of the present invention, the automatic liquid nitrogen replenishment system for low-temperature testing further includes a temperature sensor 7, which is used to detect the ambient temperature inside the test tank 10 and send the ambient temperature to the intelligent control module 12. The intelligent control module 12 is used to adjust the liquid nitrogen flow rate based on the difference between the ambient temperature and the liquid nitrogen temperature range; When the difference between the ambient temperature and the liquid nitrogen temperature zone is greater than 5°C, the intelligent control module 12 controls the mass flow controller 5 to reduce the liquid nitrogen output flow rate.

[0073] In practical applications, temperature sensor 7 refers to a detection device used to collect real-time ambient temperature data inside the test tank 10. It can be implemented using low-temperature resistant temperature detection elements such as platinum resistance thermometers or thermocouples. Preferably, temperature sensor 7 uses a high-precision Pt100 platinum resistance sensor to provide accurate temperature monitoring data for the intelligent control module 12 and to provide real-time feedback on the test environment temperature status. The liquid nitrogen temperature zone refers to the preset stable temperature range (approximately -196℃) required for the low-temperature test, and its specific value can be set to -196℃ ± 0.5℃. The intelligent control module 12 uses a control logic based on temperature difference to adjust the flow rate, aiming to suppress temperature fluctuations, ensure the stability of the test environment, and avoid affecting the accuracy of test data due to temperature deviations.

[0074] Specifically, during operation, temperature sensor 7 continuously monitors the ambient temperature inside test tank 10 and synchronously transmits the real-time temperature data to intelligent control module 12. Intelligent control module 12 compares the received ambient temperature with the preset liquid nitrogen temperature range and calculates the temperature difference. If the calculated temperature difference is greater than 5°C, it indicates that the test environment temperature deviates from the standard range and needs to be corrected by adjusting the liquid nitrogen flow rate. At this point, intelligent control module 12 immediately sends a flow rate adjustment signal to mass flow controller 5, controlling it to reduce the liquid nitrogen output flow rate. This design dynamically optimizes the replenishment flow rate through temperature feedback, avoiding potential localized temperature drops or other temperature changes that might occur with fixed flow rate replenishment.

[0075] Through the above technical solution, when the difference between the ambient temperature inside the test tank 10 and the liquid nitrogen temperature zone is greater than 5℃ during the low temperature test, the system can respond in time and reduce the output flow of liquid nitrogen through the mass flow controller 5, effectively suppressing temperature fluctuations and avoiding test data deviations caused by excessive temperature difference.

[0076] like Figure 1 As shown, in some embodiments of the present invention, the automatic liquid nitrogen replenishment system for cryogenic testing also includes a pressure sensor 8 and an emergency shut-off valve 3. The pressure sensor 8 is used to detect the pressure inside the test tank 10 in real time and transmit it to the intelligent control module 12. The emergency shut-off valve 3 is located on the connecting pipeline 2 and is connected to the intelligent control module 12 via signal. Specifically, the emergency shut-off valve 3 is located at one end of the connecting pipeline 2 near the liquid storage tank 1. When the pressure inside the test tank 10 exceeds 0.15 MPa, the intelligent control module 12 controls the emergency shut-off valve 3 to close, stopping the supply of liquid nitrogen to the test tank 10.

[0077] In practical applications, the pressure sensor 8 can be installed on the top of the test tank 10. The pressure sensor 8 refers to the detection device used to collect pressure data inside the test tank 10 in real time. It can be implemented by low-temperature and high-pressure resistant detection elements such as piezoelectric pressure sensors and strain gauge pressure sensors. The purpose is to provide accurate pressure monitoring data for the intelligent control module 12 and provide real-time early warning of abnormal pressure conditions inside the tank.

[0078] Emergency shut-off valve 3, as a key safety component of the system, is used to quickly cut off the liquid nitrogen delivery link in the event of sudden abnormal operating conditions. This valve features fast response and excellent sealing performance, preventing the continued flow of liquid nitrogen in emergencies and reducing safety risks. Furthermore, the emergency shut-off valve 3 is located close to the storage tank 1, allowing for immediate cut-off of the liquid nitrogen source in case of emergencies, maximizing the reduction of safety risks.

[0079] The 0.15MPa pressure threshold is a safety threshold determined by comprehensively considering the pressure resistance performance of the test tank 10, the vaporization characteristics of liquid nitrogen, and the test safety requirements. It serves as the safety line for triggering an emergency shutdown. The intelligent control module 12 controls the emergency shut-off valve 3 based on the pressure threshold. It is a rapid response mechanism for pressure safety protection. Its purpose is to prevent safety accidents such as overpressure leakage and tank damage caused by the continuous increase in pressure inside the tank by timely cutting off the liquid nitrogen supply link.

[0080] Specifically, during operation, pressure sensor 8 continuously monitors the pressure data inside test tank 10 and synchronously transmits the real-time pressure signal to intelligent control module 12. Intelligent control module 12 compares the received pressure data with a preset safety threshold of 0.15 MPa. If the detected pressure data exceeds 0.15 MPa, it indicates that the pressure inside test tank 10 has exceeded the safe range, posing a safety hazard. At this point, intelligent control module 12 immediately sends a shut-off signal to emergency shut-off valve 3. Upon receiving the signal, emergency shut-off valve 3 quickly activates, cutting off the liquid nitrogen supply to connecting pipeline 2 and terminating the replenishment of liquid nitrogen to test tank 10. This design, through the linkage of real-time pressure monitoring and emergency shut-off, achieves rapid response and handling of pressure anomalies.

[0081] like Figure 1 As shown, in some embodiments of the present invention, a one-way valve 6 is also provided on the connecting pipe 2, and the conduction direction of the one-way valve 6 is consistent with the liquid nitrogen flow direction. One-way valve 6 is located between mass flow controller 5 and test tank 10.

[0082] In practical applications, the one-way valve 6 refers to a valve component that allows fluid to flow in only one direction and prevents reverse flow. It can be implemented using cryogenic one-way valve structures such as spring-loaded or gravity-operated one-way valves. Its purpose is to create a one-way channel for liquid nitrogen transport, preventing liquid nitrogen or vaporized nitrogen in the test tank 10 from flowing back to the mass flow controller 5 and the upstream pipeline. Placing the one-way valve 6 between the mass flow controller 5 and the test tank 10 is a reasonable layout that comprehensively considers both flow regulation accuracy and backflow prevention. It directly blocks the influence of reverse fluid from the test tank 10 side on the mass flow controller 5, ensuring the stable operation of the flow regulation component.

[0083] Specifically, during operation, when the system is replenishing liquid nitrogen normally, liquid nitrogen flows out from the storage tank 1, passes sequentially through the emergency shut-off valve 3, solenoid valve 4, and mass flow controller 5, and then flows smoothly into the test tank 10 along the conduction direction of the one-way valve 6. The one-way valve 6 remains open under the positive pressure of the liquid nitrogen, without affecting the normal replenishment flow rate. If an abnormal situation such as a sudden pressure increase occurs in the test tank 10, causing the liquid nitrogen or vaporized gas in the tank to have a reverse flow tendency, the one-way valve 6 will quickly close under the reverse pressure, blocking the backflow of the reverse fluid to the mass flow controller 5 and the upstream pipeline. This design achieves passive protection through the unidirectional conduction characteristic, without the need for active control by the intelligent control module 12, and has high reliability.

[0084] like Figure 1 As shown, in some embodiments of the present invention, the connecting pipe 2 is a vacuum-insulated transmission pipe, and an electric heating wire can be installed on the vacuum-insulated transmission pipe. The electric heating wire is controlled by the intelligent control module 12.

[0085] In practical applications, vacuum-insulated transmission pipelines refer to cryogenic fluid transport pipelines with a vacuum-jacketed insulation structure. They utilize a double-layer structure with an inner and outer layer and an intermediate vacuum layer to block heat conduction and convection. This can be achieved using a stainless steel inner liner + vacuum jacket + outer protective layer structure. The purpose is to reduce the cooling loss of liquid nitrogen during transport, prevent pressure fluctuations caused by the violent vaporization of liquid nitrogen due to temperature increases, and prevent frost and ice formation on the outer wall of the pipeline. The electric heating wire is a low-temperature resistant heating component adapted to low-temperature environments, which can be made of low-temperature resistant heating materials such as nickel-chromium alloys. Its purpose is to remove frost formed after the vaporization of residual liquid nitrogen in the pipeline through low-power heating. The intelligent control module 12 controls the heating wire, specifically addressing pipeline blockage issues during resupply intervals without affecting the cooling capacity of the liquid nitrogen transport.

[0086] Specifically, during operation, during the normal liquid nitrogen replenishment phase, the vacuum-insulated transmission pipeline effectively blocks external heat transfer through the vacuum jacket, reducing the loss of cold energy of liquid nitrogen in the pipeline and ensuring that liquid nitrogen is delivered to the test tank 10 in a stable state. When the system enters the replenishment interval (i.e., the phase when liquid nitrogen replenishment stops), the intelligent control module 12 automatically identifies the operating conditions and sends a start signal to the electric heating wire to start a short-term low-power heating mode. The heat generated by the heating wire can quickly melt the frost formed after the residual liquid nitrogen in the pipeline vaporizes, avoiding frost accumulation that could cause pipeline blockage. After heating is completed, the intelligent control module 12 automatically turns off the heating wire to prevent continuous heating from affecting the insulation performance of the pipeline.

[0087] like Figure 2 As shown, an embodiment of the present invention also provides a recycling device, including a test tank 10 and the above-mentioned intelligent automatic liquid nitrogen replenishment system for low-temperature testing. The test tank 10 is provided with a sample rack 11 for placing test devices.

[0088] This self-circulating recycling device integrates the aforementioned automated, high-precision, and high-safety intelligent automatic liquid nitrogen replenishment system with the test tank 10 and sample rack 11 to form an integrated device that combines the function of ensuring a stable low-temperature test environment with the basic architecture of liquid nitrogen recovery and circulation.

[0089] Among them, the test tank 10 serves as the core cavity for the low-temperature test, providing a closed low-temperature environment for the test device. It is connected to the connecting pipe 2 of the intelligent automatic liquid nitrogen supply system to receive precisely supplied liquid nitrogen. The sample rack 11 is located inside the test tank 10 and serves as a support component for the test device. It can be made of low-temperature resistant, high-strength metal or ceramic materials, which can provide a stable placement position for the test device and prevent the device from shifting due to liquid nitrogen flow or fluctuations in the tank environment.

[0090] As a preferred embodiment, the sample holder 11 can adopt a hollow frame structure, which allows liquid nitrogen to circulate evenly within the test tank 10, ensuring that all parts of the test device are in a stable low-temperature environment and improving the accuracy of the test data. Simultaneously, the sample holder 11 can be designed as an adjustable structure, allowing for the adjustment of the layer spacing to accommodate test devices of different sizes and types, thus enhancing the versatility of the device. The connection between the intelligent automatic liquid nitrogen replenishment system and the test tank 10 can be secured with a low-temperature resistant sealing flange to ensure the sealing of the connection and prevent liquid nitrogen leakage or the entry of outside air from affecting the stability of the test environment.

[0091] The working principle of this embodiment is as follows: The device integrates an intelligent automatic liquid nitrogen replenishment system with the test tank 10 and the sample rack 11, ensuring the stable conduct of the low-temperature test while laying the foundation for subsequent liquid nitrogen recovery and recycling. Specifically, before the test, the test personnel place the device to be tested on the sample rack 11 inside the test tank 10, and fix the position of the device through the stable structure of the sample rack 11; then, the intelligent automatic liquid nitrogen replenishment system is started. The system accurately replenishes liquid nitrogen into the test tank 10 according to the preset liquid level control logic through the storage tank 1, the connecting pipeline 2 and various valves, maintaining a stable low-temperature test environment inside the tank.

[0092] like Figure 2 As shown, in some embodiments of the present invention, the test tank 10 is further provided with a lifting device 13, which drives the sample rack 11.

[0093] The purpose of the lifting device 13 is to ensure that the test device in the sample holder 11 is always immersed in the liquid nitrogen environment, or continuously undergoes temperature cycling tests in a liquid nitrogen environment at -196℃ and a nitrogen gas environment. In other words, through this setup, whether the test device needs to be stably kept in a liquid nitrogen environment for a long time, or the test device needs to be frequently alternated between liquid nitrogen and nitrogen gas environments for temperature cycling tests, the lifting device 13 can function effectively, ensuring that the test device is in the corresponding ambient temperature as preset, meeting the diverse temperature requirements of different low-temperature tests, and thus ensuring the accuracy and reliability of the low-temperature tests.

[0094] In practical applications, the lifting device 13 can be implemented using a spring. This spring has low-temperature resistance and can be made of materials such as low-temperature alloy springs. The purpose is to drive the sample holder 11 to rise and fall through the elastic extension and contraction characteristics of the spring, while using the spring's restoring ability to ensure the positional stability of the sample holder 11. The sample holder 11 can be made of low-temperature resistant foamed materials, lightweight alloys, etc., to utilize the material's own buoyancy to offset part of the gravity, combined with the elastic driving force of the spring, enabling the sample holder 11 to rise and fall more smoothly.

[0095] In addition, the lifting mechanism can also adopt a ball screw structure, driven by a low-temperature resistant stepper motor to achieve the lifting of the sample holder 11. The stepper motor can be installed on the top of the test tank 10. If the lifting mechanism adopts a ball screw structure, the sample holder 11 can also be made of low-temperature resistant foaming material, lightweight alloy, etc.

[0096] Specifically, when a spring is used as the lifting device 13, the spring and the sample holder 11 are connected in a driving manner. Before the test, the initial position of the sample holder 11 can be adjusted by compressing or stretching the spring according to the weight of the device under test and the required height. The elastic force of the spring can stably support the sample holder 11 and the test device. During the test, if a fine adjustment of the height is required, the synergistic effect of the buoyancy of the sample holder 11 material and the spring force can be used to make the sample holder 11 adaptively adjust to a suitable position. When a ball screw structure is used, it can establish a signal connection with the intelligent control module 12, and the height can be precisely adjusted through intelligent control without manual intervention. This multi-form design takes into account both the simple and low-cost spring-type solution and the high-precision motor-driven solution, adapting to different test requirements.

[0097] like Figure 2 As shown, in some embodiments of the present invention, the recycling self-circulation device further includes a heat exchanger 100, a recycling air bag 200, a gas compression pump 300, a nitrogen cylinder 400, and a liquefaction device 500, which are connected in series via pipelines. The top of the liquid storage tank 1 and the top of the test tank 10 are both connected to the air inlet of the heat exchanger 100 via pipes; The liquid outlet of the liquefaction unit 500 is connected to the storage tank 1 via a pipeline; The outlet of the nitrogen cylinder 400 is connected to the liquid storage tank 1 through a high-pressure gas transmission pipe, and an adsorber 900 is also installed on the high-pressure gas transmission pipe.

[0098] In practical applications, heat exchanger 100 refers to a heat exchange device used for pre-cooling vaporized nitrogen. It can be implemented using shell-and-tube or plate-type low-temperature heat exchanger structures. Its purpose is to reduce the temperature of vaporized nitrogen and reduce energy consumption for subsequent compression and liquefaction processes. The recovery gas bladder 200 is a buffer component used for temporary storage of vaporized nitrogen. It has a certain degree of flexibility and pressure resistance, aiming to balance pressure fluctuations during nitrogen recovery and prevent gas backflow. The gas compression pump 300 is a power device used to pressurize nitrogen. It can be implemented using a low-temperature compressor, aiming to compress low-pressure vaporized nitrogen to the pressure required for liquefaction. The nitrogen cylinder 400 is a high-pressure storage container used to temporarily store compressed nitrogen, aiming to ensure pressure stability before liquefaction and provide a stable gas source for the liquefaction process. The liquefaction device 500 is the core device for cooling and liquefying compressed nitrogen. It can be implemented using throttling expansion refrigeration, low-temperature refrigeration, etc., aiming to convert gaseous nitrogen into liquid nitrogen and achieve resource recovery. The Adsorber 900 refers to a purification component used to filter impurities in nitrogen. It can be made using adsorption materials such as activated carbon and molecular sieves. Its purpose is to remove impurities such as moisture and oil from nitrogen, so as to avoid impurities affecting the purity of liquid nitrogen and the life of system components.

[0099] Specifically, this scheme connects components such as the heat exchanger 100 and the recovery gas bladder 200 in series, and establishes connections with the storage tank 1 and the test tank 10, forming a complete liquid nitrogen recovery self-circulation system. During operation, the nitrogen gas volatilized at the top of the storage tank 1 and the nitrogen gas vaporized during the test in the test tank 10 are simultaneously drawn into the inlet of the heat exchanger 100 through their respective pipelines. After being pre-cooled by the heat exchanger 100, the nitrogen gas enters the recovery gas bladder 200 for buffer storage. Subsequently, the gas compression pump 300 extracts the low-pressure nitrogen gas from the recovery gas bladder 200 and pressurizes it. The pressurized nitrogen gas is then sent to the nitrogen cylinder 400 for temporary storage and pressure stabilization. When the pressure in the nitrogen cylinder 400 reaches a preset value, the nitrogen gas is sent to the liquefaction device 500, where it is liquefied and converted into liquid nitrogen. Finally, the liquefied liquid nitrogen flows back to the storage tank 1 through pipelines and is reused for replenishing the cryogenic test.

[0100] In addition, when the pressure inside the storage tank 1 is insufficient or the amount of liquid nitrogen is short, the nitrogen cylinder 400 can replenish the nitrogen to the storage tank 1 through the high-pressure gas transmission pipe. During the replenishment process, the adsorber 900 on the high-pressure gas transmission pipe purifies the nitrogen to ensure the purity of the nitrogen entering the storage tank 1.

[0101] A gas valve is installed on the pipeline between the nitrogen cylinder 400 and the liquefaction unit 500. This valve controls the flow of nitrogen. When the liquefaction unit 500 is operating normally and the nitrogen cylinder 400 contains sufficient pressurized nitrogen, the valve opens, allowing nitrogen to smoothly enter the liquefaction unit 500 for liquefaction. If the liquefaction unit 500 malfunctions or requires maintenance, the valve can be closed, cutting off the nitrogen flow and preventing waste and potential damage to the equipment. Furthermore, by appropriately controlling the valve opening, the flow rate of nitrogen into the liquefaction unit 500 can be adjusted to accommodate different liquefaction needs and process conditions, further ensuring the stable and efficient operation of the entire liquid nitrogen recovery self-circulation system.

[0102] Through the above technical solutions, the self-circulating recovery device achieves efficient recovery and reuse of liquid nitrogen, effectively solving the problem of large-scale evaporation and waste of liquid nitrogen in existing cryogenic experiments, significantly reducing experimental costs, and meeting the requirements of green and environmentally friendly experiments. Simultaneously, this self-circulating recovery device ensures the airtightness of the experimental environment, preventing nitrogen leakage from impacting the surrounding environment; the adsorber 900 improves the purity of the recovered liquid nitrogen, ensuring the reliability of cryogenic experiments. Furthermore, the dual-function nitrogen cylinder 400 (temporarily storing recovered nitrogen and replenishing nitrogen) further enhances the system's stability and emergency response capabilities, enabling the entire device to not only provide precise experimental support but also possess efficient resource recovery capabilities, significantly expanding the device's practicality and application value.

[0103] In some embodiments of the present invention, the outlet end of the high-pressure gas transmission pipe can be connected to the top of the liquid storage tank 1, and the inlet end of the connecting pipe 2 is connected to one end of the liquid storage tank 1 near its bottom, which can be used to press out liquid nitrogen from the liquid storage tank 1 into the test tank 10.

[0104] In practical applications, the outlet of the high-pressure gas pipeline is connected to the top of the liquid storage tank 1. This connection allows the high-pressure nitrogen output from the nitrogen cylinder 400 to directly act on the gas phase space within the liquid storage tank 1. The purpose is to generate driving force through the pressure difference of the high-pressure nitrogen, propelling the liquid nitrogen in the liquid storage tank 1 towards the test tank 10. This solution ensures the continuity and stability of liquid nitrogen replenishment and avoids valves (such as the emergency shut-off valve 3, solenoid valve 4, and other core valve components) from being subjected to the combined conditions of high pressure and extreme low temperature for extended periods.

[0105] In some embodiments of the present invention, the outer shell of the adsorber 900 may be made of low-temperature stainless steel, and the internal flow channel may be a corrugated flow channel. The adsorber 900 has three adsorption layers arranged sequentially along the gas flow direction: a pre-dust removal layer, a deep dehydration layer, and an oil removal layer. Each of the three layers contains an adsorption material. The adsorption material can be an adsorption material that can withstand extreme low temperatures of -196℃ (such as low-temperature modified molecular sieves, low-temperature activated carbon, etc.), and the types of adsorption materials in adjacent adsorption layers are different. In addition, the adsorber 900 can be equipped with a low-temperature resistant temperature sensor and a low-temperature resistant pressure sensor to monitor the internal status in real time.

[0106] In practical applications, adsorption materials resistant to extreme low temperatures of -196℃ (such as low-temperature modified molecular sieves, low-temperature activated carbon, and low-temperature adsorption resins) and low-temperature stainless steel shells are selected to avoid adsorbent activity decay, structural embrittlement, and shell damage at low temperatures, ensuring stable operation of the 900 adsorber in low-temperature environments. Furthermore, the multi-level adsorption structure consists of a pre-dust removal layer, a deep dehydration layer, and an oil removal layer, aiming to achieve precise, graded removal of impurities and improve adsorption targeting. The optimized flow channel design (i.e., using a wave-shaped flow channel) ensures uniform nitrogen flow through the adsorption layers, reducing flow resistance and adsorption dead zones. Low-temperature and low-temperature pressure sensors enable adsorption status monitoring and regeneration control, restoring adsorbent activity and ensuring long-term stable operation of the 900 adsorber.

[0107] Specifically, during operation, when nitrogen from nitrogen cylinder 400 is supplied to storage tank 1 via a high-pressure gas pipeline, the nitrogen first enters the pre-dust removal layer of the high-purity nitrogen adsorber 900. Solid impurities in the nitrogen are removed through a filter medium (such as low-temperature resistant activated carbon), preventing impurities from scratching the surface of the subsequent adsorbent and affecting the adsorption effect. Then, the nitrogen enters the deep dehydration layer, where low-temperature modified molecular sieves adsorb moisture, preventing water from freezing and clogging the pipeline or affecting the purity of the liquid nitrogen at low temperatures. Next, the nitrogen enters the oil removal layer, where low-temperature resistant adsorption resin adsorbs oil and other organic impurities, preventing oil contamination of the liquid nitrogen. Simultaneously, the wave-shaped flow ensures that the nitrogen flows evenly through each adsorption layer, eliminating adsorption dead zones caused by excessively high local flow rates, ensuring that each part of the adsorbent functions fully. During adsorption, a low-temperature resistant temperature / pressure sensor monitors the internal state of the adsorber 900 in real time and can transmit the data to the intelligent control module 12 for recording, facilitating subsequent processing.

[0108] like Figure 2 As shown, in some embodiments of the present invention, one-way pressure relief valves are provided on the pipe between the top of the liquid storage tank 1 and the air inlet of the heat exchanger 100, and on the pipe between the top of the test tank 10 and the air inlet of the heat exchanger 100.

[0109] In practical applications, a one-way pressure relief valve is a valve component that allows fluid to flow only in the direction of nitrogen recovery and automatically relieves pressure when the pressure in the pipeline exceeds a preset threshold. It can be implemented using low-temperature resistant structures such as spring-loaded one-way pressure relief valves and pilot-operated one-way pressure relief valves. The purpose is to create a one-way flow channel for nitrogen recovery while simultaneously achieving automatic overpressure relief protection. Specifically, two sets of one-way pressure relief valves correspond to the two recovery branches from the storage tank 1 and test tank 10 to the heat exchanger 100, respectively. The purpose of these valves is twofold: firstly, to prevent high-pressure nitrogen from the heat exchanger 100 side from flowing back into the storage tank 1 or test tank 10, thus avoiding abnormal pressure increases within the tanks; secondly, to automatically open and relieve pressure when either recovery branch experiences pressure exceeding the limit due to pipeline blockage or poor recovery, preventing pipeline damage due to overpressure and providing independent pressure safety assurance for the two recovery branches.

[0110] Specifically, during operation, when nitrogen vaporized at the top of storage tank 1 is supplied to heat exchanger 100, the corresponding one-way pressure relief valve remains open under the positive pressure of nitrogen, allowing nitrogen to flow smoothly into heat exchanger 100. If a sudden pressure increase occurs on the heat exchanger 100 side, generating reverse pressure, the one-way pressure relief valve quickly closes, blocking the nitrogen return path and preventing abnormal pressure within storage tank 1. Similarly, when vaporized nitrogen at the top of test tank 10 is supplied to heat exchanger 100, the corresponding one-way pressure relief valve simultaneously performs unidirectional conduction and reverse blocking functions. When the pressure in any recovery branch exceeds the preset threshold of the one-way pressure relief valve due to blockage or other faults, the corresponding one-way pressure relief valve automatically opens the pressure relief channel, safely releasing (or introducing into a preset buffer space) the high-pressure nitrogen in the branch. After the pressure drops to a safe range, it automatically closes, ensuring stable pressure in the pipeline branch, storage tank 1, and test tank 10.

[0111] Through the above technical solution, the one-way pressure relief valves on the two recovery branches can effectively realize the one-way recovery and delivery of nitrogen, completely avoiding the risks of abnormal tank pressure and pipeline impact caused by nitrogen backflow. At the same time, the automatic overpressure relief function can quickly handle pressure rise problems caused by branch blockages and other faults, preventing pipeline damage due to overpressure and ensuring the operational safety of the recovery self-circulation system. The dual one-way pressure relief protection design provides independent safety protection for the two recovery branches, ensuring that an abnormality in one branch will not affect the normal recovery of the other branch, further improving the stability and fault tolerance of the recovery self-circulation system.

[0112] like Figures 3 to 4 As shown, in some embodiments of the present invention, the heat exchange tube in the heat exchanger 100 has a plate-shaped fin group evenly distributed along the axial direction on its outer wall. The plate-shaped fin group includes a plurality of fins 600 arranged in a circumferential array. Specifically, the plurality of fins 600 are evenly distributed along the circumference of the heat exchange tube to form a radial fin group. The central angles between adjacent fins 600 are the same.

[0113] In addition, the fin 600 has a long strip structure, and its cross section perpendicular to its own (fin 600) extension direction is a continuous arc protrusion in the shape of a candied hawthorn. The cross section has a first side 700 and a second side 800 arranged opposite to each other. The first side 700 is composed of alternating protruding arc segments 701 and transition arc segments 702. The protruding arc segments 701 form radially protruding enhanced heat exchange units, and the transition arc segments 702 realize the smooth connection of adjacent protrusions.

[0114] In practical applications, the plate-shaped fins on the outer wall of the heat exchanger tube refer to extended heat-receiving components used to increase the contact area between the heat exchanger tube and the fluid, and enhance the heat exchange effect. They are evenly distributed along the axial direction of the heat exchanger tube to improve the heat exchange rate between vaporized nitrogen and the cooling medium, ensuring that the vaporized nitrogen can be cooled quickly, thus reducing energy consumption for subsequent compression and liquefaction processes. Specifically, the fins 600, arranged in a circumferential array, form a radial fin group, with adjacent fins 600 having the same central angle. This design ensures a uniform fluid flow field distribution around the heat exchanger tube, avoiding localized heat exchange dead zones and guaranteeing heat exchange uniformity. The fins 600 have a candied hawthorn-shaped cross-section, with their raised arc segments 701 further increasing the contact area between the fins and the fluid, while simultaneously disrupting the fluid boundary layer, enhancing fluid turbulence, and strengthening the heat exchange effect. The smooth connection design of the transition arc segments 702 reduces fluid flow resistance, lowers system energy consumption, and prevents structural damage caused by stress concentration at sharp edges in low-temperature environments, ensuring the structural stability of the fins in extreme low-temperature environments.

[0115] In addition to enhancing heat exchange and ensuring low-temperature stability, the structural design of the fin 600 also provides a basis for shortening the pipe length between the heat exchanger 100 and the recovery bladder 200 due to its optimized hydrodynamic characteristics. Specifically, the transition arc segment 701 of the fin 600 cross-section achieves smooth fluid flow guidance, reducing nitrogen flow resistance and enabling stable nitrogen delivery within a shorter pipe without the need to extend the pipe to mitigate pressure fluctuations. Furthermore, the radially distributed, uniformly distributed fin group ensures a uniform flow field around the heat exchange tubes, avoiding pipe impact caused by excessively high local flow velocities, further supporting stable operation of the short-distance pipe. The shortened pipe length reduces pipe material consumption, lowers system construction costs, and simultaneously reduces nitrogen residence time in the pipe, reducing cold loss and improving recovery efficiency.

[0116] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. An automatic liquid nitrogen replenishment system for cryogenic testing, characterized in that, include: A liquid storage tank (1) is used to contain liquid nitrogen; A connecting pipe (2) is provided, one end of which is connected to a storage tank (1), and the other end of which is connected to a test tank (10). The connecting pipeline (2) is connected in series with a solenoid valve (4) and a mass flow controller (5) along the liquid nitrogen flow direction. A liquid level sensor (9) is used to detect the liquid level data in the test tank (10); The intelligent control module (12) is connected to the solenoid valve (4) and the mass flow controller (5) respectively, and the intelligent control module (12) is configured to execute the following control logic based on the liquid level data transmitted by the liquid level sensor (9): When the liquid level is lower than the first threshold, the intelligent control module (12) controls the solenoid valve (4) to open and controls the mass flow controller (5) to replenish the liquid nitrogen flowing out of the storage tank (1) to the test tank (10) according to the preset flow rate. When the liquid level data is higher than the second threshold, the intelligent control module (12) controls the solenoid valve (4) to close and stop replenishing liquid nitrogen into the test tank (10); The second threshold is greater than the first threshold.

2. The automatic liquid nitrogen replenishment system for cryogenic testing according to claim 1, characterized in that, The first threshold is 20% of the effective volume of the test tank (10); The second threshold is 80% of the effective volume of the test tank (10).

3. The automatic liquid nitrogen replenishment system for cryogenic testing according to claim 1, characterized in that, The liquid level sensor (9) is any one or more of the following: capacitive liquid level sensor, ultrasonic liquid level sensor, and high-temperature superconducting liquid level sensor.

4. The automatic liquid nitrogen replenishment system for cryogenic testing according to claim 3, characterized in that, The high-temperature superconducting liquid level sensor includes a first substrate (102), a ReBCO tape layer (101), and a second substrate (103) arranged sequentially from top to bottom. Electrodes are provided at both ends of the upper surface and both ends of the lower surface of the ReBCO tape layer (101); The upper and / or lower surfaces of the ReBCO tape layer (101) are provided with an insulating layer.

5. The automatic liquid nitrogen replenishment system for cryogenic testing according to claim 1, characterized in that, It also includes a temperature sensor (7), which is located inside the test tank (10). The temperature sensor (7) is used to detect the ambient temperature inside the test tank (10) and send the ambient temperature to the intelligent control module (12). The intelligent control module (12) is used to adjust the liquid nitrogen flow rate according to the difference between the ambient temperature and the liquid nitrogen temperature range; When the difference between the ambient temperature and the liquid nitrogen temperature zone is greater than 5°C, the intelligent control module (12) controls the mass flow controller (5) to reduce the liquid nitrogen output flow.

6. The automatic liquid nitrogen replenishment system for cryogenic testing according to claim 1, characterized in that, It also includes a pressure sensor (8) and an emergency shut-off valve (3). The pressure sensor (8) is used to detect the pressure inside the test tank (10) in real time and transmit it to the intelligent control module (12). The emergency shut-off valve (3) is located on the connecting pipeline (2) and is connected to the intelligent control module (12) via signal. When the pressure inside the test tank (10) is greater than 0.15 MPa, the intelligent control module (12) controls the emergency shut-off valve (3) to close, stopping the supply of liquid nitrogen to the test tank (10).

7. The automatic liquid nitrogen replenishment system for cryogenic testing according to claim 1, characterized in that, The connecting pipeline (2) is also equipped with a one-way valve (6), and the conduction direction of the one-way valve (6) is consistent with the liquid nitrogen flow direction; The one-way valve (6) is located between the mass flow controller (5) and the test tank (10).

8. A recycling self-circulation device, characterized in that, Includes a test tank (10) and an intelligent automatic liquid nitrogen supply system for cryogenic testing as described in any one of claims 1-7, wherein the test tank (10) is provided with a sample rack (11) for placing test devices.

9. A recycling self-circulation device according to claim 8, characterized in that, The test tank (10) is also equipped with a lifting device (13), which is driven and connected to the sample rack (11).

10. A recycling self-circulation device according to claim 8, characterized in that, It also includes nitrogen cylinders (400); The outlet of the nitrogen cylinder (400) is connected to the storage tank (1) via a high-pressure gas transmission pipe, and the high-pressure gas transmission pipe is also equipped with an adsorber (900) for purifying nitrogen.

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