Ultra-low Temperature and High Pressure Environmental Material Mechanical Property Testing System and Method

Abstract

The present application discloses a mechanical property testing system and method for materials in an ultra-low temperature and high-pressure environment. The testing system includes: a medium circulation system and a cold source supply system. The medium circulation system includes a tube side of a heat exchanger, a circulation pump, and a test chamber. The tube side of the heat exchanger, the circulation pump, and the test chamber are connected in sequence. The medium outlet of the test chamber is connected to a vent pipe. The cold source supply system includes a shell side of the heat exchanger, a first valve group, a second valve group, a gas-liquid mixer, a liquefied gas pump, a normal temperature gas storage tank, and a first liquefied gas storage tank. The shell side of the heat exchanger houses the tube side of the heat exchanger. The outlet of the first liquefied gas storage tank is respectively connected to the first valve group and the liquefied gas pump. The liquefied gas pump is connected to the second valve group. Both the first valve group and the second valve group are connected to the inlet of the gas-liquid mixer. The second valve group is also connected to the pipeline where the circulation pump is located. The outlet of the gas-liquid mixer is connected to one end of the shell side of the heat exchanger. The other end of the shell side of the heat exchanger is connected to the vent pipe through a discharge pipeline.

Description

Technical Field

[0001] The present invention belongs to the field of testing the mechanical properties of materials, and particularly relates to a testing system and method for the mechanical properties of materials in an ultra-low temperature and high-pressure environment. Background Art

[0002] The liquefaction temperatures of industrial gases under normal pressure are very low. For example, the temperature of liquid nitrogen is -196°C, the temperature of liquefied natural gas is -163°C, and the temperature of liquid hydrogen is -253°C. When developing pressure-bearing equipment related to the production, storage, and transportation of these cryogenic liquefied gases, such as liquid hydrogen storage tanks, on-vehicle cryogenic high-pressure hydrogen storage tanks, high-pressure liquid nitrogen pumps, etc., the first thing to do is to study the mechanical properties of materials at ultra-low temperatures.

[0003] Existing experimental devices for the low-temperature mechanical properties of materials can generally be divided into two forms: liquid cooling and non-liquid cooling.

[0004] Liquid cooling means directly cooling the test environmental chamber with cryogenic liquefied gas. For example, the test environmental chamber is cooled with liquid nitrogen at -196°C, and the tensile specimen is immersed in the liquid nitrogen environment for tensile testing. The advantage of liquid cooling is that it can relatively stably control the temperature during the test process. The disadvantage is that the test can only be carried out at certain specific saturation temperature points corresponding to the liquefied gas, and the test temperature and pressure cannot be adjusted.

[0005] Non-liquid cooling means achieving the low-temperature environment of the test chamber in the form of an active refrigerator and refrigerant. For example, a GM refrigerator is usually used as the cold source. The advantage of non-liquid cooling is that it can conveniently adjust the temperature and pressure environment required for the test. Its disadvantage is that the temperature and pressure in the environmental chamber cannot be accurately controlled during the test process. For the test of a liquid hydrogen or liquid helium environment with a temperature lower than -196°C, another major defect of non-liquid cooling is that it takes a very long time to achieve the required temperature and pressure environment of the test chamber, resulting in low test efficiency. In addition, the non-liquid cooling method cannot also characterize the influence of the medium itself on the material properties. For example, for metal materials used to manufacture liquid hydrogen equipment, when tested in a non-liquid cooling device with helium as the refrigerant, the influence of the liquid hydrogen medium on the material, such as hydrogen embrittlement, cannot be characterized.

[0006] In addition, although a testing system for the mechanical properties of materials at low temperatures is mentioned in related designs, this system can use the liquefied gas in direct contact with the test material during actual application as the refrigeration cold source required for the experiment, solving the problem of low experimental efficiency existing in the traditional technology. However, due to the fact that this technical solution fails to consider the strong temperature-pressure coupling relationship of gases at low temperatures, it is difficult to accurately adjust the temperature and pressure simultaneously during the actual operation process because the temperature and pressure affect each other and the liquid filling is uneven. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a mechanical property testing system and method for materials in an ultra-low temperature and high-pressure environment.

[0008] To solve the technical problem, the solution of the present invention is as follows:

[0009] On the one hand, the present application provides a mechanical property testing system for materials in an ultra-low temperature and high-pressure environment, including: a medium circulation system and a cold source supply system. The medium circulation system includes a heat exchanger tube side, a circulation pump, and a test chamber. The test chamber is suitable for accommodating a universal testing machine for mechanical tests. The heat exchanger tube side, the circulation pump, and the test chamber are connected in sequence. The medium outlet of the test chamber is connected to a vent pipe. The cold source supply system includes a heat exchanger shell side, a first valve group, a second valve group, a gas-liquid mixer, a liquefied gas pump, a normal temperature gas storage tank, and a first liquefied gas storage tank. The heat exchanger shell side houses the heat exchanger tube side. The outlet of the first liquefied gas storage tank is respectively connected to the first valve group and the liquefied gas pump. The liquefied gas pump is connected to the second valve group. Both the first valve group and the second valve group are connected to the inlet of the gas-liquid mixer. The second valve group is also connected to the pipeline where the circulation pump is located. The outlet of the gas-liquid mixer is connected to one end of the heat exchanger shell side. The other end of the heat exchanger shell side is connected to the vent pipe through a discharge pipeline. The heat exchanger shell side and the heat exchanger tube side form countercurrent heat exchange.

[0010] According to an embodiment of the present application, the cold source supply system further includes a second liquefied gas storage tank. The outlets of the second liquefied gas storage tank and the first liquefied gas storage tank are both connected to a first reversing valve. The first reversing valve is also respectively connected to the first valve group and the liquefied gas pump. Among them, the second liquefied gas storage tank is equipped with a GM refrigerator and a low-temperature thermostat.

[0011] According to an embodiment of the present application, the media in the normal temperature gas storage tank, the first liquefied gas storage tank, and the second liquefied gas storage tank are the same substance.

[0012] According to an embodiment of the present application, the heat exchanger shell side has a cylindrical tank structure, and the heat exchanger tube side is configured as a spiral tube structure disposed inside the tank structure.

[0013] According to an embodiment of the present application, a fully enclosed hollow inner cylinder is provided inside the heat exchanger shell side, and the spiral tube structure is arranged around the hollow inner cylinder.

[0014] According to an embodiment of the present application, the test chamber includes a box body and a door body. The door body is connected to the box body through a dynamic sealing structure with three-stage spring energy storage.

[0015] According to an embodiment of the present application, a thermometer and a pressure sensor are provided inside the test chamber, a safety valve is provided on the test chamber, and the medium outlet of the test chamber is connected to a vent pipe through the safety valve.

[0016] According to an embodiment of the present application, a thermometer and a flowmeter are provided at the outlet of the normal temperature gas storage tank, and a pressure reducing valve is equipped at the outlet of the gas-liquid mixer.

[0017] According to an embodiment of the present application, a first pressure control valve is provided on the pipeline between the tube side of the heat exchanger and the vent pipe, a second pressure control valve is provided on the vent pipe, and a stop valve is provided on the pipeline between the test chamber and the tube side of the heat exchanger.

[0018] According to an embodiment of the present application, the end of the vent pipe is connected to an exhaust gas recovery device.

[0019] On the other hand, the present application proposes a method for testing the mechanical properties of materials in an ultra-low temperature and high-pressure environment. This testing method is applied to the above-mentioned testing system for the mechanical properties of materials in an ultra-low temperature and high-pressure environment. The testing method includes:

[0020] Adjust the first valve group to transport the normal temperature gaseous medium in the normal temperature gas storage tank to the test chamber through a liquefied gas pump to provide a circulating medium for the test chamber.

[0021] Adjust the second valve group to allow the liquid medium in the first liquefied gas storage tank to enter the shell side of the heat exchanger through a gas-liquid mixer.

[0022] Start the circulation pump, and the medium in the test chamber exchanges heat with the medium in the shell side of the heat exchanger in the tube side of the heat exchanger, so that the circulating medium in the test chamber becomes the experimental target medium.

[0023] According to an embodiment of the present application, if the density of the experimental target medium is lower than the corresponding density of the normal temperature gas under the design pressure of the test chamber, by adjusting the pressure of the gas already filled in the circulation system, the gas density is made to be consistent with the density of the experimental target medium.

[0024] If the density of the experimental target medium is equal to or higher than the corresponding density of the normal temperature gas under the design pressure of the test chamber, then density adjustment needs to be carried out by combining temperature reduction and pressure supplementation.

[0025] According to an embodiment of the present application, the density adjustment by combining temperature reduction and pressure supplementation includes:

[0026] First, make the normal temperature gas storage tank and the liquefied gas storage tank communicate with the gas-liquid mixer at the same time to form a temperature-controllable cold source, introduce the cold source into the shell side of the heat exchanger to exchange heat with the circulating medium in the tube side of the heat exchanger to cool it down, and the pressure of the circulating medium will drop simultaneously with the temperature.

[0027] Use the normal-temperature gas in the normal-temperature gas storage tank to supplement the pressure of the circulating medium, and then continue to cool down. Through multiple pressure supplementation and cooling operations, the density of the medium in the circulation system is made consistent with the density of the experimental target medium.

[0028] According to an embodiment of the present application, the test method further includes a rewarming operation after the test:

[0029] Discharge the circulating medium from the test chamber to the vent pipe, and then connect the normal-temperature gas storage tank to the medium circulation system to inject normal-temperature gas into the medium circulation system;

[0030] Start the circulation pump to circulate the normal-temperature gas in the medium circulation system until the metal wall surface of the test chamber and the shell side of the heat exchanger are rewarmed.

[0031] Compared with the prior art, the beneficial effects of the present application are:

[0032] 1. Compared with the traditional liquidless cooling method, the present application can use the liquefied gas that comes into direct contact with the test material during actual application as the refrigeration cold source required for the test, thus solving the problem of low test efficiency existing in the active refrigerator in the liquidless cooling method. At the same time, since the test system can be placed in the medium corresponding to the service conditions, the influence of the medium on the material can be considered.

[0033] 2. Compared with the traditional liquid cooling method, the present invention controls the temperature and pressure conditions required for the test by setting a heat exchanger. Since the heat exchanger is large enough compared to the volume of the test chamber and has a large enough heat transfer area. If there are fluctuations in pressure and temperature during the test, the temperature control power can increase as the temperature rises. Although there is a coupling situation of temperature and pressure changes for high-pressure gas at low temperatures, this solution realizes a one-to-one mapping relationship between temperature and pressure at a specific density of the gas or liquefied gas by determining the density of the gas or liquefied gas in the test chamber, thus solving the problem that it is difficult to adjust temperature and pressure simultaneously. Therefore, the present invention can stably control the temperature and pressure of the test chamber and can withstand a large heat load, solving the problem of temperature and pressure coupling and instability in the existing liquid cooling low-temperature test device.

[0034] 3. The ultra-low temperature and high-pressure material performance test system provided by the present invention can use a gas-liquid mixer and a heat exchanger to regulate the temperature and pressure of the liquefied gas or the gas after gasification. Therefore, this system can not only cover most of the process conditions in the existing hydrogen liquefaction or helium liquefaction devices in research work, but also provide test conditions for low-temperature gaseous application scenarios. Thus, the test requirements of materials under various typical medium, temperature, and pressure combination conditions are realized, solving the problem that the existing liquid cooling test device can only conduct tests at specific temperature points and pressure points.

[0035] 4. In the ultra-low temperature and high-pressure material property testing system of the present invention, the configured equipment form, cold insulation technology, and liquefied gas circulation equipment can all adopt existing mature technologies; therefore, the overall system construction cost is relatively low, with very good feasibility and is suitable for widespread promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0037] Figure 1 is a schematic diagram of the mechanical property testing system of materials in an ultra-low temperature and high-pressure environment according to an embodiment of the present application;

[0038] Figure 2 is a schematic diagram of the structure of the shell side and the tube side of the heat exchanger according to an embodiment of the present application;

[0039] Figure 3 is a flowchart of the method for testing the mechanical properties of materials in an ultra-low temperature and high-pressure environment according to an embodiment of the present application.

[0040]

DESCRIPTION OF THE REFERENCE NUMERALS

[0041] 1: First liquefied gas storage tank; 2: Second liquefied gas storage tank; 3: Normal temperature gas storage tank; 4: First valve group; 5: Directional valve; 6: Liquefied gas pump; 7: Second valve group; 8: Gas-liquid mixer; 9: Check valve; 10: Circulation pump; 11: Shell side of the heat exchanger; 12: Tube side of the heat exchanger; 13: First pressure control valve; 14: Second pressure control valve; 15: Globe valve; 16: Exhaust gas recovery device; 17: Test chamber: 18: Vent pipe; 19: Hollow inner cylinder. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0043] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used in the description of this application in the specification are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the description and claims of this application and the above drawings are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the description and claims of this application or the above drawings are used to distinguish different objects and are not used to describe a specific order or primary-secondary relationship.

[0044] Reference to "embodiment" in this application means that a specific feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0045] In the description of this application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "joined", and "attached" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0046] The term "and / or" in this application is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this application generally represents an "or" relationship between the associated objects before and after.

[0047] The "multiple" mentioned in this application refers to two or more (including two). Similarly, "multiple groups" refers to two or more groups (including two groups), and "multiple pieces" refers to two or more pieces (including two pieces).

[0048] Description of the inventive principle:

[0049] 1. In the related technical solutions, the cold source in the cold source storage tank is first introduced into the temperature and pressure regulating chamber, and then the temperature and pressure are increased through the normal temperature gas storage tank. During the test process, the internal pressure is stabilized through the pressure control valve, and the temperature in the temperature and pressure regulating chamber is adjusted through the cold source storage tank. The most prominent drawback of this technical solution is that it does not consider the coupling relationship between the temperature and pressure of the low-temperature gas. During the actual operation process, due to the mutual influence of temperature and pressure, and the uneven filling of the liquid in the temperature and pressure regulating chamber (this unevenness is particularly obvious when far from the boiling point of the cold source), it is difficult to adjust the filling speed of the cold source storage tank, further resulting in unclear control logic of the liquid pump in the design process of the control system, and also posing high requirements for the arrangement method of the temperature sensor.

[0050] In the present application, the applicant proposes an innovative solution idea. First, connect the normal temperature gas storage tank to the tube side of the heat exchanger and fill the medium circulation system with normal temperature gas; rely on the pressure difference between the normal temperature gas storage tank, the test chamber and the tube side of the heat exchanger to pressurize the gas in the circulation system, adjust the density of the gas to be consistent with the working conditions required for the test, and then continue to cool; or, according to the situation that the pressure of the circulating medium decreases simultaneously with the temperature, supplement the pressure, and then adjust the density of the gas to be consistent with the working conditions required for the test, and then continue to cool; this solution considers and utilizes the coupling relationship between temperature and pressure. Based on the principle of mass conservation, when the temperature is adjusted, the pressure of the circulating medium is also adjusted simultaneously.

[0051] During the test process of the present application, by mixing the normal temperature gas and the liquid through the gas-liquid mixer, the cold source in the shell side of the heat exchanger can be maintained at the temperature required by the test, and large-range stepless temperature adjustment can be achieved through heat exchange with the circulating medium in the tube side; this temperature adjustment solution is simple and mature, and can maintain good accuracy.

[0052] 2. In the related technical solutions, to maintain the stability of the temperature and pressure in the test chamber, the designed volume of the temperature and pressure regulating chamber needs to be large enough. This temperature and pressure regulating chamber is essentially a spiral tube heat exchanger. If the shell side of the heat exchanger is to withstand high internal pressure and the tube side is to withstand high external pressure, when using S31608 material, the wall thickness is very thick. Not only is the spiral tube difficult to process, but also due to the large wall thickness of the temperature and pressure regulating chamber, a large amount of cold energy is required for cooling. If liquefied gas is used for cooling, a large amount of liquid hydrogen is required to make the temperature of the temperature and pressure regulating chamber reach the corresponding temperature range, and the cost of a single test is extremely high. And in fact, only the temperature and pressure conditions of hydrogen in the test chamber need to be maintained, and most of the cold energy in the temperature and pressure regulating chamber is wasted on the cooling wall surface, and it will also cause difficulties in the rewarming process after the test.

[0053] In the solution of this application, only the tube side of the heat exchanger bears high internal pressure; and due to its small diameter, the wall thickness does not need to be too thick; at the same time, the shell side of the heat exchanger only needs to bear a relatively low design pressure, and the wall thickness can be significantly reduced compared with the original solution under the consideration of a relatively conservative safety factor. On the other hand, since only the outlet temperature of the tube side of the heat exchanger needs to be controlled, the volume of the shell side of the heat exchanger does not need to be very large. Even a fully enclosed hollow inner cylinder with a relatively low wall thickness requirement can be placed inside it to reduce the volume of the shell side, which not only simplifies the processing technology but also avoids the waste of cooling capacity.

[0054] 3. In the related technical solutions, the influence of the work done by the high-pressure liquid pump on the liquid temperature is not considered, resulting in the inability to achieve most key working conditions. Taking liquid hydrogen as an example, in fact, when using a liquid hydrogen pump to pressurize liquid hydrogen to high pressure, a large amount of heat will be input into the liquid hydrogen. This influence is small in the scenario of a large flow rate and a high-power GM refrigerator in a hydrogen refueling station. However, in the circulating pump or liquid hydrogen pump in the laboratory test scenario, the flow rate is small, and the influence of the heat introduced by the pump operation cannot be ignored and will even become the main influence. Therefore, for the tests of a large number of key working conditions such as high-pressure tests in the range of temperature 33K - 50K and pressure 35 - 45MPa (this test corresponds to the use scenario of low-temperature high-pressure hydrogen in truck transportation), due to the influence of the circulating pump or liquid hydrogen pump, it has become impossible to achieve. Moreover, high-pressure small-flow pumps need to be customized and are expensive.

[0055] In this application, the circulating medium is not directly adjusted to high pressure by using a liquefied gas pump; instead, an innovative combination of a gas-liquid mixer and a heat exchanger is used to exchange heat between a cold source with controllable temperature and the hydrogen for high-pressure tests, ultimately achieving temperature and pressure regulation. Considering that even using a low-pressure liquefied gas pump will generate a certain amount of heat, this application further proposes to set up a liquefied gas storage tank equipped with a GM refrigerator and a low-temperature thermostat, and endow the liquefied gas in this storage tank with a certain degree of subcooling through a small-power GM refrigerator, so as to meet the requirements of tests under extreme conditions such as a temperature of 20K. At the same time, on the premise of maintaining circulation, the flow rate of the circulating pump is gradually reduced to reduce the introduced heat until the temperature of the medium in the test chamber reaches the experimental target value.

[0056] 4. The solution of this application breaks through the conventional technical thinking and is not restricted to the common experimental experience of adjusting the temperature and pressure of the test chamber simultaneously; instead, it uses the high-pressure gas in a normal-temperature gas storage tank to inject the experimental medium into the circulation system for pressure regulation and supplementary pressure, realizing the density control of the medium in the test chamber, and then further controlling the temperature of the experimental medium by using the temperature control in the heat exchanger, thus solving the problem of gas temperature and pressure coupling at low temperature that is difficult to avoid in traditional test technologies. Therefore, in the solution of this application, since the density of the medium remains unchanged, the medium pressure will decrease simultaneously with the temperature. When the temperature of the medium in the test chamber is adjusted, the pressure will definitely be adjusted simultaneously. Since the entire adjustment process undergoes a steady and smooth transition, the situation of frequently opening and closing the safety valve will not occur, reducing the problem of heat leakage in the test chamber.

[0057] 5. In the traditional temperature and pressure control scheme, whether using a temperature and pressure regulating chamber or a heat exchanger, the main purpose is only to consider achieving temperature reduction, and the pressure control is achieved by a separate liquid pump, without ever considering the temperature-pressure strong coupling relationship of the experimental medium under low-temperature conditions. Although the scheme of this application also uses a conventional shell-and-tube heat exchanger, while using the heat exchanger to achieve the conventional use of cooling high-temperature gas with low-temperature liquid, the present invention further breaks through the conventional thinking. By cooperating with a gas-liquid mixer and taking advantage of the large volume difference between the tube side and the shell side, during the cooling process, through the liquefied gas rapid cooling test chamber, and during the mechanical experiment, by changing the gas-liquid mixing ratio in the gas-liquid mixer to control the temperature of the shell side of the temperature and pressure regulating chamber, thereby realizing stepless regulation of the temperature of the test chamber during the experiment.

[0058] 6. In the traditional cooling scheme, there are also cases where a GM refrigeration unit and heating resistors are directly used to adjust the temperature of the experimental medium, but such schemes are not applicable to high-pressure gas environment tests. On the one hand, it is dangerous to electrically heat a part of the high-pressure gas. On the other hand, due to the need to achieve high-pressure conditions, the wall thickness of the test chamber is greatly increased, so the heat capacity is large. The disadvantage of the GM refrigerator is that the refrigeration efficiency is low when it is below the liquid temperature range, so the test time is further extended; if the time needs to be shortened, the existing schemes often increase the number of GM refrigerators or use liquid cooling, resulting in a further increase in the comprehensive experimental cost.

[0059] For the working condition where the temperature is close to or lower than the boiling point of the target medium, this scheme innovatively proposes to adopt a hierarchical cooling strategy. First, use the liquid in the low-pressure liquefied gas storage tank to cool the experimental medium; then use the liquid in the liquefied gas storage tank equipped with a GM refrigeration unit and a low-temperature thermostat to further cool the experimental medium. Since the heat leakage of the liquefied gas storage tank is much smaller than that of the cold source supply system and the medium circulation system, the scheme of this application can, while ensuring the cooling rate, greatly reduce the requirement for the refrigeration power of the GM refrigerator and further reduce the comprehensive experimental cost.

[0060] This application proposes a material mechanics performance test system for ultra-low temperature and high-pressure environment, which includes a medium circulation system and a cold source supply system. Among them, the medium circulation system includes the tube side 12 of the heat exchanger, a circulation pump 10, and a test chamber 17. The test chamber 17 is suitable for accommodating a universal testing machine for mechanical tests. The tube side 12 of the heat exchanger, the circulation pump 10, and the test chamber 17 are connected in sequence. The medium outlet of the test chamber 17 is connected to a vent pipe 18;

[0061] The test chamber 17 is suitable for carrying a universal testing machine for mechanical tests in its inner cavity. The test chamber 17 has a double-layer box structure inside and outside. There is a gap and a vacuum is maintained between the two layers of boxes. A medium outlet and a medium inlet are respectively provided on the top and bottom panels of the box structure. The universal testing machine carried inside the test chamber 17 can perform mechanical tests such as tension, compression, and fracture toughness by changing the fixtures.

[0062] As an optional solution, to reduce heat leakage and avoid air leakage, the door body of the test chamber 17 adopts a dynamic seal structure with three-stage spring energy storage. Specifically, the test chamber 17 can include a box body and a quick-opening flat cover, and the quick-opening flat cover can be connected to the box body through a dynamic seal structure with three-stage spring energy storage.

[0063] A thermometer and a pressure sensor are provided inside the test chamber 17, and a safety valve is provided on the test chamber 17. The medium outlet of the test chamber 17 can be connected to the safety valve, and the safety valve is connected to the vent pipe 18 through a pipeline. When the pressure inside the test chamber 17 exceeds the limit, the test medium will be quickly discharged through the safety valve to prevent the test chamber 17 from failing.

[0064] The test chamber 17, the circulation pump 10, and the tube side 12 of the heat exchanger are connected by pipelines to form a circulation loop, thereby obtaining a medium circulation system. The medium outlet of the test chamber 17 can be connected to the vent pipe 18 through an outlet pipeline, and the end of the vent pipe 18 can be connected to the waste gas recovery device 16, and the waste gas recovery device 16 can carry an air-bath type vaporizer.

[0065] The cold source supply system can include the shell side 11 of the heat exchanger, the first valve group 4, the second valve group 7, the gas-liquid mixer 8, the liquefied gas pump 6, the normal temperature gas storage tank 3, and the first liquefied gas storage tank 1. The shell side 11 of the heat exchanger houses the tube side 12 of the heat exchanger. The shell side 11 of the heat exchanger housing the tube side 12 of the heat exchanger can form a complete heat exchanger, and this heat exchanger can be a spiral tube heat exchanger.

[0066] The outlet of the first liquefied gas storage tank 1 is respectively connected to the first valve group 4 and the liquefied gas pump 6. The liquefied gas pump 6 is connected to the second valve group 7. Both the first valve group 4 and the second valve group 7 are connected to the inlet of the gas-liquid mixer 8. The second valve group 7 is also connected to the pipeline where the circulation pump 10 is located. The outlet of the gas-liquid mixer 8 is connected to one end of the shell side 11 of the heat exchanger. The other end of the shell side 11 of the heat exchanger is connected to the vent pipe 18 through a discharge pipeline. The shell side 11 of the heat exchanger and the tube side 12 of the heat exchanger perform countercurrent heat exchange. That is to say, the flow direction of the medium inside the shell side 11 of the heat exchanger and the flow direction of the medium inside the tube side 12 of the heat exchanger can be opposite.

[0067] In some embodiments of the present application, the cooling supply system further includes a second liquefied gas storage tank 2. The outlet of the second liquefied gas storage tank 2 and the outlet of the first liquefied gas storage tank 1 are both connected to a first reversing valve 5, and the first reversing valve 5 is also respectively connected to a first valve group 4 and a liquefied gas pump 6; wherein, the second liquefied gas storage tank 2 is equipped with a GM refrigerator and a low-temperature thermostat.

[0068] The outlet pipeline of the first liquefied gas storage tank 1 and the outlet pipeline of the second liquefied gas storage tank 2 can be connected in parallel to the first reversing valve 5. The pipeline after the first reversing valve 5 can be divided into two paths. One path is connected to the first valve group 4 on the outlet pipeline of the normal-temperature gas storage tank 3, and the other path is connected to the second valve group 7 through the liquefied gas pump 6; the first valve group 4 is also respectively connected to the inlet of a gas-liquid mixer 8 through a pipeline; the second valve group 7 is also respectively connected to the inlet of the gas-liquid mixer 8 and the pipeline where a circulation pump 10 is located through a pipeline; the outlet of the gas-liquid mixer 8 is connected to one end of the shell side 11 of a heat exchanger through a pipeline, and the other end of the shell side 11 of the heat exchanger is connected to a vent pipe 18 through a discharge pipeline. The shell side 11 of the heat exchanger and the tube side 12 of the heat exchanger form a countercurrent heat exchange.

[0069] As an alternative, the shell side 11 of the heat exchanger has a cylindrical tank structure, and inlets and outlets are respectively arranged on the end heads at both ends. The tube side 12 of the heat exchanger is a spiral tube structure arranged inside the shell side 11 of the heat exchanger, and inlets and outlets connecting the tube side 12 of the heat exchanger are arranged on the shell side 11 of the heat exchanger in a centrally symmetric manner; a fully enclosed hollow inner cylinder 19 is nested inside the spiral tube structure, and the spiral tube structure can be arranged around the hollow inner cylinder 19 to further reduce the volume for accommodating the cold medium in the shell side 11 of the heat exchanger, reduce the consumption of the cold source, and can avoid short-circuit flow and uneven flow, improving the heat exchange efficiency. The tube thickness of the spiral tube type heat exchanger structure needs to meet the strength requirements, the radial dimension of the spiral coil needs to meet the design specifications, and the spiral tube needs to ensure a certain heat exchange area to achieve heat exchange of a certain power, ensuring that the test cooling time will not be too long. A first pressure control valve 13 can be arranged on the pipeline between the tube side 12 of the spiral tube type heat exchanger and the vent pipe 18; a second pressure control valve 14 can be arranged on the vent pipe 18; a stop valve 15 can be arranged on the pipeline between the test chamber 17 and the tube side 12 of the spiral tube type heat exchanger. The circulation pump 10 can adopt a plunger type high-pressure diaphragm pump to ensure the circulation of experimental media with different components; and the flow rate of the circulation pump should be adjustable, and during the mechanical test, the flow rate can be reduced while maintaining the circulation, minimizing the heat leakage during the test and reducing the consumption of the cold source.

[0070] As an alternative, the normal-temperature gas storage tank 3 can be a spherical storage tank, with the internal gas pressure much higher than the highest pressure required for the test, and the volume is sufficient to supply sufficient normal-temperature high-pressure gas to the test chamber 17; a thermometer and a flowmeter can be provided at the outlet of the normal-temperature gas storage tank 3, and the real-time density of the liquefied gas or gas in the test chamber 17 can be obtained through the flow formula by measuring the flow rate at the outlet. A pressure reducing valve can be equipped at the outlet of the gas-liquid mixer 8; the circulation pump 10 is a diaphragm reciprocating pump; a check valve 9 can be provided on the pipeline between the circulation pump and the tube side 12 of the heat exchanger. The pressure reducing valves inside the first valve group 4 and the second valve group 7 can be used to reduce the pressure of the gas or liquefied gas to the required pressure. The volumes of the first liquefied gas storage tank 1 and the second liquefied gas storage tank 2 are both much larger than the volume of the test chamber, and the liquefied gas in the tanks is directly provided by the liquefaction equipment, with low requirements for subcooling degree. The GM refrigeration unit can cool the liquefied gas within a certain period of time and overcome the heat leakage of the storage tank itself through the cryostat. When cooling the system, first, the liquefied gas storage tank at a higher temperature provides cold energy. When the temperature cannot continue to drop, the liquefied gas storage tank at a lower temperature equipped with a set of GM refrigerators and a cryostat further provides cold energy to reach the temperature required for the test. The temperature of the cold source at the outlet can be adjusted by regulating the pressure and flow rate of the liquefied gas and gas at the inlet of the gas-liquid mixer; by using the pressure reducing valves in the valve group and equipping a pressure reducing valve at the outlet of the liquefied gas pump, it can be ensured that the liquefied gas or gas flowing into the shell side 11 of the heat exchanger does not exceed the design pressure.

[0071] The present application also provides a method for testing the mechanical properties of materials in an ultra-low temperature and high-pressure environment. This testing method is applied to the above-mentioned testing system for the mechanical properties of materials in an ultra-low temperature and high-pressure environment, and the testing method includes:

[0072] Adjust the first valve group to transport the normal-temperature gaseous medium in the normal-temperature gas storage tank to the test chamber through the liquefied gas pump to provide a circulating medium for the test chamber;

[0073] Adjust the second valve group to allow the liquid medium in the first liquefied gas storage tank to enter the shell side of the heat exchanger through the gas-liquid mixer;

[0074] Start the circulation pump, and the medium in the test chamber exchanges heat with the medium in the shell side of the heat exchanger in the tube side of the heat exchanger, so that the circulating medium in the test chamber becomes the experimental target medium.

[0075] It should be noted that when the normal-temperature gaseous medium in the normal-temperature gas storage tank 3 first enters the test chamber 17, since the temperature and pressure do not meet the requirements, it is an ordinary medium at this time. After cooling and pressurization, the temperature and pressure meet the conditions, and the medium in the test chamber 17 becomes the experimental target medium. At this time, various performance manifestations of the material in the test chamber 17 can be tested.

[0076] According to some embodiments of the present application, if the density of the experimental target medium is lower than the corresponding density of the normal-temperature gas at the designed pressure of the test chamber 17, the pressure of the gas filled in the circulation system is adjusted to make the gas density consistent with the density of the experimental target medium; if the density of the experimental target medium is equal to or higher than the corresponding density of the normal-temperature gas at the designed pressure of the test chamber 17, density adjustment needs to be carried out by combining temperature reduction and pressure compensation.

[0077] According to some embodiments of the present application, the density adjustment by combining temperature reduction and pressure compensation includes:

[0078] First, the normal-temperature gas storage tank 3 and the first liquefied gas storage tank 1 are simultaneously connected to the gas-liquid mixer 8 to form a cold source with controllable temperature. The cold source is introduced into the shell side 11 of the heat exchanger to exchange heat with the circulating medium in the tube side 12 of the heat exchanger to cool it down. The pressure of the circulating medium will decrease simultaneously with the temperature.

[0079] The normal-temperature gas in the normal-temperature gas storage tank 3 is used to compensate the pressure of the circulating medium, and then continue to cool down. Through multiple operations of pressure compensation and temperature reduction, the density of the medium in the circulation system is made consistent with the density of the experimental target medium.

[0080] According to some embodiments of the present application, the testing method further includes the rewarming operation after the experiment:

[0081] The circulating medium is discharged from the test chamber 17 to the vent pipe 18, and then the normal-temperature gas storage tank 3 is connected to the medium circulation system to fill the medium circulation system with normal-temperature gas.

[0082] The circulation pump 10 is started to make the normal-temperature gas circulate in the medium circulation system until the metal wall surface of the test chamber 17 and the shell side of the heat exchanger are rewarmed.

[0083] A cold source supply system is constructed by using the shell side 11 of the heat exchanger, the gas-liquid mixer 8, the normal-temperature gas storage tank 3, the liquefied gas pump 6 and at least one liquefied gas storage tank (the first liquefied gas storage tank 1 and / or the second liquefied gas storage tank 2) to provide the experimental target medium and the cold source for heat exchange; a medium circulation system is constructed by using the test chamber 17, the circulation pump 10 and the tube side 12 of the heat exchanger to cool down the circulating medium through heat exchange; the experimental target medium and the cold source are the same substance, and its state is gaseous, liquid or supercritical fluid.

[0084] The normal-temperature gas storage tank 3 is connected to the tube side 12 of the heat exchanger and the test chamber 17 to fill the medium circulation system with normal-temperature gas, and the filled gas is pressurized by relying on the pressure difference between the normal-temperature gas storage tank 3 and the medium circulation system.

[0085] If the density of the experimental target medium is lower than the corresponding density of the normal-temperature gas at the design pressure of the test chamber, adjust the pressure of the gas already filled in the circulation system to make the gas density consistent with the density of the experimental target medium; if the density of the experimental target medium is equal to or higher than the corresponding density of the normal-temperature gas at the design pressure of the test chamber 17, density adjustment needs to be carried out by combining temperature reduction and pressure compensation: first, connect the normal-temperature gas storage tank 3 and the liquefied gas storage tank (the first liquefied gas storage tank 1 or / and the second liquefied gas storage tank 2) to the gas-liquid mixer 8 simultaneously to form a cold source with controllable temperature, introduce the cold source into the shell side 11 of the heat exchanger to exchange heat with the circulating medium in the tube side 12 of the heat exchanger to cool it down; the pressure of the circulating medium will decrease simultaneously with the temperature; use the normal-temperature gas in the normal-temperature gas storage tank 3 to compensate the pressure of the circulating medium, and then continue to cool down; through multiple pressure compensation and temperature reduction operations, the density of the medium in the circulation system is finally made consistent with the density of the experimental target medium;

[0086] Control the ratio of the gas and liquefied gas entering the gas-liquid mixer 8 to keep the temperature in the shell side 11 of the heat exchanger consistent with the experimental target temperature; gradually reduce the flow rate of the circulation pump 10 under the premise of maintaining circulation to reduce the introduced heat until the temperature of the medium in the test chamber 17 reaches the experimental target value; since the density of the medium in the circulation system remains unchanged, based on the principle of mass conservation, the adjustment of the medium temperature and pressure can be completed simultaneously.

[0087] The rewarming operation after the experiment: first, discharge the circulating medium from the test chamber 17 to the vent pipe 18; then connect the normal-temperature gas storage tank 3 to the medium circulation system and fill the system with normal-temperature gas; start the circulation pump 10 to make the normal-temperature gas circulate in the medium circulation system until the rewarming of the metal wall of the test chamber 17 and the shell side of the heat exchanger is completed.

[0088] The present invention is applicable to a variety of experimental conditions, and the experimental target medium can be hydrogen, liquid hydrogen or supercritical hydrogen fluid, or nitrogen, liquid nitrogen or supercritical nitrogen fluid. During the process of adjusting the density of the experimental medium, when pressurizing or compensating the pressure, hydrogen or nitrogen stored in the normal-temperature gas storage tank is used, and the pressure range can be selected from 50 to 98 MPa. There are two liquefied gas storage tanks, one of which provides liquid hydrogen (such as temperature 22K), liquid nitrogen (such as temperature 80K) or liquefied natural gas (such as temperature 115K); the other is equipped with a GM refrigerator and a low-temperature thermostat, and provides liquid with a relatively lower temperature, such as liquid hydrogen (such as temperature 18K), liquid nitrogen (such as temperature 75K) or liquefied natural gas (such as temperature 105K); in the case of extremely low-temperature experimental conditions, first use the liquid with a higher temperature to cool down the medium in the circulation system, and then use the liquid with a lower temperature to cool down.

[0089] Specific application examples under different experimental conditions.

[0090] Example 1:

[0091] Target medium and conditions: medium is hydrogen gas, pressure is 5 MPa, temperature is 100 K;

[0092] 1. Preparation stage:

[0093] (1) Standby of normal temperature high-pressure gas: Hydrogen gas is replenished into the normal temperature gas storage tank 3 through an external compressor to reach the design pressure.

[0094] (2) Purge and discharge air: Adjust the first valve group 4 and the second valve group 7, open the first pressure control valve 13 and the second pressure control valve 14, and use the normal temperature hydrogen gas in the normal temperature gas storage tank 3 to purge the gas-liquid mixer 8, the shell side 11 of the heat exchanger, the tube side 12 of the heat exchanger, and the test chamber 17. The purge gas is finally discharged to the waste gas recovery device 16 through the vent pipe 18.

[0095] 2. Adjust the density of the test hydrogen gas:

[0096] Adjust the first valve group 4 to connect the normal temperature gas storage tank 3 to the tube side 12 of the heat exchanger and the test chamber 17 through the liquefied gas pump 6. Use the pressure reducing valve in the first valve group 4 to adjust the outlet pressure to 16.2 MPa, that is, maintain the pressure of the hydrogen gas in the test chamber 17 at 16.2 MPa. The density of hydrogen gas with a pressure of 5 MPa and a temperature of 100 K is the same as that of hydrogen gas with a pressure of 16.2 MPa and a temperature of 298 K, both being 12 kg / m³.

[0097] When adjusting the temperature under the condition of maintaining the same density, the coupling relationship between temperature and pressure can be utilized; when adjusting the temperature subsequently, the pressure can be adjusted simultaneously. Use the first pressure control valve 13 to maintain the pressure not exceeding the design pressure of the shell and tube side of the heat exchanger.

[0098] 3. Temperature adjustment stage:

[0099] (1) Adjust the reversing valve 5 and use the liquid hydrogen in the first liquefied gas storage tank 1 to cool down the system. Specifically, adjust the second valve group 7 so that the liquid hydrogen enters the shell side 11 of the heat exchanger through the gas-liquid mixer 8, use the second pressure control valve 14 on the vent pipe to maintain the pressure of the shell side of the heat exchanger not exceeding the design pressure, and discharge the excess liquid hydrogen. Start the circulation pump 10 to circulate the hydrogen gas in the test chamber 17 and the tube side 12 of the heat exchanger, and conduct convective heat exchange with the low-temperature liquid hydrogen in the shell side 11 of the heat exchanger to achieve a stable temperature drop until the temperature approaches 100 K.

[0100] (2)Control the first valve group 4 and the second valve group 7 to adjust the flow rate and pressure of hydrogen and liquid hydrogen flowing into the gas-liquid mixer 8. Mix the liquid hydrogen from the first liquefied gas storage tank 1 and the normal-temperature hydrogen from the normal-temperature gas storage tank 3 in a certain proportion so that the temperature of hydrogen at the outlet of the gas-liquid mixer 8 remains at 100K, and finally make the temperature of the shell side 11 of the heat exchanger stable at 100K. Gradually reduce the flow rate of the circulation pump 10 to reduce the heat introduced by the pump operation, and precisely control the temperature of hydrogen in the test chamber 17 until the temperature in the test chamber 17 reaches the set test temperature.

[0101] Since the density of hydrogen in the test chamber 17 and the tube side 12 of the heat exchanger remains unchanged and mass is conserved, the pressure is adjusted simultaneously. And because the tube side 12 of the heat exchanger is designed as a spiral tube, it has a large heat transfer area and can be moderately deformed, and can withstand the heat leakage of the system environment and the heat generated due to the change of the specimen shape during the test.

[0102] 4. Rewarming stage:

[0103] (1)Discharge the low-temperature hydrogen for the test: Open the first pressure control valve 13, the second pressure control valve 14 and the stop valve 15 to gradually discharge the low-temperature hydrogen in the test chamber 17.

[0104] (2)Introduce normal-temperature hydrogen to rewarm the metal wall surface: Close the second pressure control valve 14, adjust the first valve group 4 so that the normal-temperature low-pressure hydrogen enters the shell side 11 of the heat exchanger and the test chamber 17 through the liquid hydrogen pump (i.e., the liquefied gas pump 6), and complete the rewarming of the metal wall surface of the test chamber 17 through the circulation of hydrogen by the circulation pump 10. On the other hand, because the tube side 12 of the heat exchanger is a spiral tube structure, the shell side 11 of the heat exchanger can also be rewarmed simultaneously during the circulation process.

[0105] Implementation case two:

[0106] Target medium and conditions: Medium is nitrogen, pressure is 5MPa, temperature is 250K;

[0107] 1. Preparation stage:

[0108] (1)Reserve normal-temperature high-pressure gas: Supplement nitrogen to the normal-temperature gas storage tank 3 through an external compressor to reach the design pressure.

[0109] (2)Purge and discharge air: Adjust the first valve group 4 and the second valve group 7, open the first pressure control valve 13 and the second pressure control valve 14, and use normal-temperature nitrogen to purge the gas-liquid mixer 8, the shell side 11 of the heat exchanger, the tube side 12 of the heat exchanger and the test chamber 17, and the purge gas is finally discharged through the vent pipe 18.

[0110] 2. Adjust the density of the nitrogen for the test:

[0111] Adjust the first valve group 4 to connect the normal-temperature gas storage tank 3 to the heat exchanger tube side 12 and the test chamber 17 through the liquid hydrogen pump 6. Use the pressure reducing valve in the first valve group 4 to adjust the outlet pressure to 6.1 MPa, that is, maintain the nitrogen pressure in the test chamber 17 at 6.1 MPa (the density of nitrogen at a pressure of 5 MPa and a temperature of 250 K is the same as that of nitrogen at a pressure of 6.1 MPa and a temperature of 298 K, both being 70 kg / m³).

[0112] 3. Temperature adjustment stage:

[0113] (1) Adjust the reversing valve 5 and use the low-pressure liquid nitrogen in the first liquefied gas storage tank 1 to cool down the system. Adjust the second valve group 2 to make the liquid nitrogen enter the heat exchanger shell side 11 through the gas-liquid mixer 8. Turn on the circulation pump 10 to make the nitrogen in the test chamber 17 and the heat exchanger tube side 12 circulate, and conduct convective heat exchange with the low-temperature and low-pressure liquid nitrogen in the heat exchanger shell side 11 to achieve a stable temperature drop until the temperature approaches 250 K.

[0114] (2) Adjust the first valve group 4 and the second valve group 7, and adjust the flow rate and pressure of the nitrogen and liquid nitrogen flowing into the gas-liquid mixer 8, so that the low-pressure liquid nitrogen from the first liquefied gas storage tank 1 and the normal-temperature nitrogen from the normal-temperature gas storage tank 3 are mixed in a certain proportion, so that the nitrogen temperature at the outlet of the gas-liquid mixer 8 reaches 250 K, and finally make the temperature of the heat exchanger shell side 11 stable at 250 K. Reduce the flow rate of the circulation pump 10 to reduce the input heat, so that the nitrogen in the test chamber 17 is accurately temperature-adjusted to the corresponding test temperature.

[0115] Since the hydrogen density in the test chamber 17 and the heat exchanger tube side 12 remains unchanged and mass is conserved, the medium pressure is also adjusted simultaneously during the temperature adjustment process. And because the heat exchanger tube side 12 is a spiral tube structure, it has a large heat exchange area and can be moderately deformed, and can withstand the heat leakage of the system environment and the heat generated due to the change in the shape of the specimen during the test.

[0116] 4. Rewarming stage:

[0117] (1) Drain the low-temperature nitrogen for the test: Open the second pressure control valve 14 and gradually drain the low-temperature nitrogen in the test chamber 17.

[0118] (2) Introduce normal-temperature hydrogen to rewarm the metal wall surface: Close the second pressure control valve 14, adjust the first valve group 4 to make the normal-temperature low-pressure nitrogen enter the heat exchanger tube side 11 and the test chamber 17 through the liquid nitrogen pump (i.e., the liquefied gas pump 6), and complete the rewarming of the metal wall surface of the test chamber 17 through the circulation of nitrogen by the circulation pump 10. On the other hand, since the heat exchanger tube side 12 is a spiral tube structure, the rewarming of the heat exchanger shell side 11 is also completed simultaneously.

[0119] Embodiment 3:

[0120] Target medium and conditions: The medium is supercritical hydrogen, with a pressure of 50 MPa and a temperature of 50 K;

[0121] 1. Preparation stage:

[0122] (1) Standby of normal-temperature high-pressure gas: Hydrogen is supplemented to the normal-temperature gas storage tank 3 through an external compressor until the designed pressure is reached.

[0123] (2) Purge and expel air: Adjust the first valve group and the second valve group, open the first pressure control valve 13 and the second pressure control valve 14, and use normal-temperature hydrogen to purge the gas-liquid mixer 8, the shell side 11 of the heat exchanger, the tube side 12 of the heat exchanger, and the test chamber 17. The purge gas is finally discharged through the vent pipe 18.

[0124] 2. Adjust the density of the supercritical hydrogen for the test:

[0125] (1) Adjust the first valve group 4 to connect the normal-temperature gas storage tank 3 to the tube side 12 of the heat exchanger through the liquid hydrogen pump (i.e., the liquefied gas pump 6). The pressure reducing valve in the first valve group adjusts the outlet pressure to 50 MPa, and 50 Mpa is the maximum pressure that the shell of the test chamber 17 can withstand.

[0126] (2) Adjust the reversing valve 5 to cool down the system using the liquid hydrogen in the first liquefied gas storage tank 1. Adjust the second valve group 7 to make the liquid hydrogen enter the shell side 11 of the heat exchanger through the gas-liquid mixer 8. Start the circulation pump 10 to circulate the hydrogen (i.e., the circulating medium) in the test chamber 17 and the tube side 12 of the heat exchanger, and conduct convective heat exchange with the low-temperature liquid hydrogen in the shell side 11 of the heat exchanger to achieve a stable temperature drop. At this time, due to the law of conservation of mass, the temperature and pressure of the hydrogen in the test chamber 17 decrease simultaneously. When the pressure drops to 5 MPa, stop cooling. At this time, the gas pressure in the test chamber 17 is lower than the maximum pressure that the shell of the test chamber 17 can withstand. Adjust the first valve group 4 to continue connecting the normal-temperature gas storage tank 3 to the tube side 12 of the heat exchanger through the liquid hydrogen pump (i.e., the liquefied gas pump 6), and use the pressure reducing valve in the first valve group 4 to adjust the outlet pressure to 50 MPa to pressurize the test chamber 17 and the tube side 12 of the heat exchanger. After the pressurization is completed, continue to cool down. Through multiple operations of pressurization and cooling, the density of the supercritical hydrogen in the test chamber 17 finally reaches the density corresponding to the supercritical hydrogen with a pressure of 50 MPa and a temperature of 50 K.

[0127] 3. Temperature adjustment stage:

[0128] Adjust the first valve group 4 and the second valve group 7, and adjust the flow rate and pressure of hydrogen and liquid hydrogen flowing into the gas-liquid mixer 8, so that the liquid hydrogen from the first liquefied gas storage tank 1 and the hydrogen from the normal temperature gas storage tank 3 are mixed in a certain proportion, so that the temperature of the hydrogen at the outlet of the gas-liquid mixer 8 reaches 50K, and finally the temperature of the shell side 11 of the heat exchanger is stabilized at 50K. Reduce the flow rate of the circulation pump 10 to reduce the input heat, so that the supercritical hydrogen in the test chamber 17 is accurately temperature-controlled to reach the corresponding test temperature.

[0129] Since the density of the supercritical hydrogen in the test chamber 17 and the tube side 12 of the heat exchanger remains unchanged, that is, the mass is conserved, the pressure is also adjusted simultaneously. And because the tube side 12 of the heat exchanger is a spiral tube structure, the heat transfer area is large and can be moderately deformed, and it can withstand the heat leakage of the system environment and the heat generated due to the change of the sample shape during the test.

[0130] 4. Rewarming stage:

[0131] (1) Drain the supercritical hydrogen for testing: Open the second pressure control valve 14 to gradually drain the supercritical hydrogen inside the test chamber 17.

[0132] (2) Pass in normal temperature hydrogen to rewarm the metal wall: Close the second pressure control valve 14, adjust the first valve group 4 so that the normal temperature low-pressure hydrogen enters the shell side 11 of the heat exchanger and the test chamber 17 through the liquid hydrogen pump (that is, the liquefied gas pump 6), and complete the rewarming of the metal wall of the test chamber 17 through the circulation of the hydrogen by the circulation pump 10. On the other hand, because the tube side 12 of the heat exchanger is a spiral tube structure, the rewarming of the shell side 11 of the heat exchanger is also completed at the same time.

[0133] Implementation case four:

[0134] Target medium and conditions: Medium is liquid hydrogen, pressure is 0.4MPa, temperature is 20K;

[0135] 1. Preparation stage:

[0136] (1) Reserve normal temperature high-pressure gas: Supplement hydrogen to the normal temperature gas storage tank 3 through an external compressor to reach the design pressure.

[0137] (2) Purge and discharge air: Adjust the first valve group 4 and the second valve group 7, open the first pressure control valve 13, the second pressure control valve 14 and the stop valve 15, and use normal temperature hydrogen to purge the gas-liquid mixer 8, the shell side 11 of the heat exchanger, the tube side 12 of the heat exchanger and the test chamber 17, and the purge gas is finally discharged through the vent pipe 18.

[0138] 2. Adjust the density of the liquid hydrogen for testing

[0139] (1)Adjust the first valve group 4 to connect the normal-temperature gas storage tank 3 to the tube side 12 of the heat exchanger through the liquid hydrogen pump (i.e., the liquefied gas pump 6), and use the pressure reducing valve in the first valve group 4 to adjust the outlet pressure to 50 MPa, which is the maximum pressure that the shell of the test chamber 17 can withstand.

[0140] (2)Adjust the reversing valve 5. First, use the liquid hydrogen in the first liquefied gas storage tank 1 to cool down the system. Adjust the second valve group 4 so that the liquid hydrogen enters the shell side 11 of the heat exchanger through the gas-liquid mixer 8. Turn on the circulation pump 10 to make the hydrogen gas (i.e., the circulating medium) in the test chamber 17 and the tube side 12 of the heat exchanger circulate, and conduct convective heat exchange with the low-temperature liquid hydrogen in the shell side 11 of the heat exchanger to achieve a stable temperature drop. At this time, due to the law of conservation of mass, the temperature and pressure of the hydrogen gas in the test chamber 17 decrease simultaneously. When the pressure drops to 5 MPa, stop cooling. At this time, the gas pressure in the test chamber 17 is lower than the maximum pressure that the shell of the test chamber 17 can withstand. Adjust the first valve group 4 to continue connecting the normal-temperature gas storage tank 3 to the tube side 12 of the heat exchanger, and use the pressure reducing valve in the first valve group 4 to adjust the outlet pressure to 50 MPa to replenish the pressure of the test chamber 17 and the tube side 11 of the heat exchanger. After the pressure replenishment is completed, continue to cool down. Through multiple pressure replenishment and cooling operations, the hydrogen density in the test chamber 17 reaches the density corresponding to the liquid hydrogen with a pressure of 0.4 MPa and a temperature of 20 K. And through this operation, the temperature inside the test chamber 17 can be stabilized at 22 K. Relatively speaking, in the prior art, due to the heat leakage of the relevant temperature and pressure regulation system being much higher than that of the liquefied gas storage tank, in order to achieve a strict temperature of 20 K in the liquid hydrogen temperature range, it is necessary to use a more expensive and more powerful refrigerator or use a large amount of scarce liquid helium in a single test to offset the heat leakage of the relevant equipment of the system and the heat input by the liquid hydrogen pump.

[0141] 3. Temperature adjustment stage:

[0142] Adjust the first reversing valve 5, use the second liquefied gas storage tank 2 equipped with a set of GM refrigerators and a cryostat as the cold source, adjust the first valve group 4 and the second valve group 7, directly introduce 20 K liquid hydrogen into the shell side 11 of the heat exchanger, and finally make the temperature of the shell side 11 of the heat exchanger stable at 20 K. Gradually reduce the flow rate of the circulation pump 10 to reduce the input heat, so that the liquid hydrogen in the test chamber 17 reaches the corresponding test temperature through precise temperature adjustment.

[0143] Since the liquid hydrogen density in the test chamber 17 and the tube side 12 of the heat exchanger remains unchanged, that is, the law of conservation of mass, the pressure is also adjusted simultaneously. And because the tube side 12 of the heat exchanger is a spiral tube structure with a large heat exchange area and can be moderately deformed, it can withstand the heat leakage of the system environment and the heat generated due to the change of the specimen shape during the test.

[0144] That is to say, in this application, the circulating medium in the experimental chamber 17 is first cooled by the medium in the first liquefied gas storage tank 1. When the temperature drops to a certain level, the medium in the second liquefied gas storage tank 2 is then used to cool the circulating medium in the experimental chamber 17. Thus, the cooling cost is greatly reduced.

[0145] 4. Rewarming stage:

[0146] (1) Drain the liquid hydrogen for the test: Open the second pressure control valve 14 to gradually drain the liquid hydrogen in the test chamber 17.

[0147] (2) Introduce normal-temperature hydrogen to rewarm the metal wall surface: Close the second pressure control valve 14, and adjust the first valve group 4 so that normal-temperature low-pressure hydrogen enters the tube side 11 of the heat exchanger and the test chamber 17 through the liquid hydrogen pump (i.e., the liquefied gas pump 6), and the circulation of hydrogen is completed through the circulation pump 10 to rewarm the metal wall surface of the test chamber 17. On the other hand, since the tube side 12 of the heat exchanger is of a spiral tube structure, the shell side 11 of the heat exchanger is also rewarmed simultaneously.

[0148] Based on the above description and application examples, it can be seen that the cryogenic high-pressure environment material performance testing system provided by the present invention uses the liquefied gas required for the test as the refrigeration cold source, which can solve the problem of low test efficiency existing in the active refrigerator in the liquid-free cooling method. By controlling the temperature and pressure conditions required for the test through the heat exchanger, the problems of unstable temperature and pressure in the existing liquid-cooled or liquid-free cooled low-temperature test devices are solved. By ensuring a certain density of the test gas or liquefied gas, the temperature-pressure coupling problem in the test is solved. The cryogenic high-pressure material performance testing system provided by the present invention can cover most of the process conditions in the existing hydrogen liquefaction or liquefied gas storage and transportation devices, realize the test requirements of materials under typical medium, temperature, and pressure combination conditions, and solve the problem that the existing liquid-cooled test devices can only conduct tests at specific temperature points and pressures. At the same time, the temperature-pressure coupling problem during the temperature and pressure adjustment process is solved, and the test cost is reduced and the required refrigeration power is reduced by using a liquefied gas storage tank and a low-pressure liquefied gas storage tank equipped with a set of GM refrigerators and a low-temperature thermostat. The cryogenic test chamber and heat exchanger configured in the present invention can adopt vacuum-wrapped insulation, which is a mature insulation technology. Therefore, the present invention has very high feasibility.

[0149] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a process, method, commodity or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, commodity or device. Without further limitation, an element defined by the phrase "comprising an..." does not exclude the presence of additional identical elements in the process, method, commodity or device comprising said element.

[0150] Each embodiment in this specification is described in a progressive manner, and the same or similar parts among the embodiments can be referred to each other. The key point of each embodiment is to illustrate the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiment.

[0151] The above are only the embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

[0152] Although the embodiments of the present application are described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A mechanical property testing system for materials in an ultra-low temperature and high pressure environment, characterized in that, Comprising: A medium circulation system, including a heat exchanger tube side, a circulation pump, and a test chamber. The test chamber is suitable for accommodating a universal testing machine for mechanical tests. The heat exchanger tube side, the circulation pump, and the test chamber are connected in sequence. The medium outlet of the test chamber is connected to a vent pipe. A cold source supply system, including a heat exchanger shell side, a first valve group, a second valve group, a gas-liquid mixer, a liquefied gas pump, a normal temperature gas storage tank, and a first liquefied gas storage tank. The heat exchanger shell side houses the heat exchanger tube side. The outlet of the normal temperature gas storage tank is connected to the first valve group. The first valve group includes a pressure reducing valve. The outlet of the first liquefied gas storage tank is respectively connected to the first valve group and the liquefied gas pump. The liquefied gas pump is connected to the second valve group. Both the first valve group and the second valve group are connected to the inlet of the gas-liquid mixer. The second valve group is also connected to the pipeline where the circulation pump is located. The outlet of the gas-liquid mixer is connected to one end of the heat exchanger shell side. The other end of the heat exchanger shell side is connected to the vent pipe through a discharge pipeline. The heat exchanger shell side and the heat exchanger tube side form countercurrent heat exchange.

2. The mechanical property testing system for materials in an ultra-low temperature and high pressure environment according to claim 1, characterized in that, The cold source supply system further includes a second liquefied gas storage tank. The outlets of the second liquefied gas storage tank and the first liquefied gas storage tank are both connected to a first reversing valve. The first reversing valve is also respectively connected to the first valve group and the liquefied gas pump. Wherein, the second liquefied gas storage tank is equipped with a GM refrigerator and a low temperature thermostat.

3. The mechanical property testing system for materials in an ultra-low temperature and high pressure environment according to claim 2, wherein The media in the normal temperature gas storage tank, the first liquefied gas storage tank, and the second liquefied gas storage tank are the same substance.

4. The mechanical property testing system for materials in an ultra-low temperature and high pressure environment according to claim 1, characterized in that, The heat exchanger shell side has a cylindrical tank structure, and the heat exchanger tube side is configured as a spiral tube structure arranged inside the tank structure.

5. The super-low temperature and high pressure environmental material mechanical property testing system according to claim 4, characterized in that, A fully enclosed hollow inner cylinder is arranged inside the heat exchanger shell side, and the spiral tube structure is arranged around the hollow inner cylinder.

6. The mechanical property testing system for materials in an ultra-low temperature and high pressure environment according to claim 1, wherein, The test chamber includes a box body and a door body. The door body is connected to the box body through a dynamic sealing structure with three-stage spring energy storage.

7. The mechanical property testing system for materials in an ultra-low temperature and high pressure environment according to claim 6, wherein A temperature measuring instrument and a pressure sensor are arranged inside the test chamber. A safety valve is arranged on the test chamber. The medium outlet of the test chamber is connected to the vent pipe through the safety valve.

8. The mechanical property testing system for materials in an ultra-low temperature and high pressure environment according to claim 1, characterized in that, A thermometer and a flow meter are arranged at the outlet of the normal temperature gas storage tank, and a pressure reducing valve is equipped at the outlet of the gas-liquid mixer.

9. The mechanical property testing system for materials in an ultra-low temperature and high pressure environment according to claim 1, wherein, A first pressure control valve is arranged on the pipeline between the heat exchanger tube side and the vent pipe. A second pressure control valve is arranged on the vent pipe. A stop valve is arranged on the pipeline between the test chamber and the heat exchanger tube side.

10. The mechanical property testing system for materials in an ultra-low temperature and high pressure environment according to claim 1, characterized in that, The end of the vent pipe is connected to an exhaust gas recovery device.

11. A testing method for the mechanical properties of materials in an ultra-low temperature and high-pressure environment, characterized in that, This testing method uses the cryogenic high-pressure environment material mechanical property testing system described in any one of claims 1-10. The testing method includes: Determining the pressure at which the medium enters the test chamber at normal temperature according to the pressure and temperature of the target medium in the test chamber. Adjusting the first valve group, reducing the pressure of the normal temperature gaseous medium in the normal temperature gas storage tank, and then transporting it to the test chamber through the liquefied gas pump to provide a circulating medium for the test chamber. Adjusting the second valve group, enabling the liquid medium in the first liquefied gas storage tank to enter the heat exchanger shell side through the gas-liquid mixer. Turn on the circulation pump. The medium in the test chamber exchanges heat with the medium in the shell side of the heat exchanger in the tube side of the heat exchanger. When adjusting the temperature under the condition of keeping the density the same, the coupling relationship between temperature and pressure is utilized to realize the adjustment of pressure at the same time.

12. The method for testing the mechanical properties of materials in an ultra-low temperature and high-pressure environment according to claim 11, characterized in that if the density of the experimental target medium is lower than the corresponding density of the normal-temperature gas under the design pressure of the test chamber, the pressure of the gas charged in the circulation system is adjusted to make the gas density consistent with the density of the experimental target medium; if the density of the experimental target medium is equal to or higher than the corresponding density of the normal-temperature gas under the design pressure of the test chamber, density adjustment needs to be carried out by combining temperature reduction and pressure compensation.

13. The method for testing the mechanical properties of materials in an ultra-low temperature and high-pressure environment according to claim 12, wherein The density adjustment by combining temperature reduction and pressure compensation includes: first, the normal-temperature gas storage tank and the first liquefied gas storage tank are simultaneously connected to the gas-liquid mixer to form a cold source with controllable temperature, and the cold source is introduced into the shell side of the heat exchanger to exchange heat with the circulating medium in the tube side of the heat exchanger to cool it down, and the pressure of the circulating medium will drop simultaneously with the temperature; the normal-temperature gas in the normal-temperature gas storage tank is used to compensate the pressure of the circulating medium, and then the temperature is continuously reduced. Through multiple pressure compensation and temperature reduction operations, the density of the medium in the circulation system is made consistent with the density of the experimental target medium.

14. The method for testing the mechanical properties of materials in an ultra-low temperature and high-pressure environment according to claim 11, wherein The test method further includes the rewarming operation after the test: discharge the circulating medium from the test chamber to the vent pipe, and then connect the normal-temperature gas storage tank to the medium circulation system to charge the normal-temperature gas into the medium circulation system; start the circulation pump to make the normal-temperature gas circulate in the medium circulation system until the metal wall surface of the test chamber and the shell side of the heat exchanger are rewarmed.

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