System and method for testing apparent heat conductivity coefficient of thermal insulation material of liquid hydrogen storage tank

Abstract

The invention provides a system and a method for testing the apparent heat conductivity coefficient of a liquid hydrogen storage tank thermal insulation material. A water cooling coil is arranged on the side wall of a calorimeter, and thermal boundary temperature controllers are arranged on the peripheries of an upper protection cavity, a test cavity and a lower protection cavity; low-temperature thermal boundary temperature control can be achieved through the thermal boundary temperature controller, thermal boundary temperature control over 0 DEG C can be achieved through the water cooling coil, and large consumption of low-temperature working media is avoided. Therefore, the system can measure the apparent heat conductivity coefficient of the thermal insulation material at different thermal boundary temperatures.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal property measurement of thermal insulation materials for cryogenic storage tanks, and in particular relates to a system and method for testing the apparent thermal conductivity of thermal insulation materials for liquid hydrogen storage tanks. Background Art

[0002] Cryogenic fluids such as liquid hydrogen, liquid nitrogen, and liquid helium have extremely low storage temperatures. For example, liquid hydrogen can be stored at temperatures as low as 20 K at 1 atmosphere. The significant difference between the storage temperature and ambient temperature can lead to heat leakage, compromising the safety of cryogenic tanks during storage and transportation. The addition of insulating materials can significantly reduce heat leakage. As a core parameter for evaluating insulation material performance, the precise measurement of apparent thermal conductivity is crucial for optimizing tank structural design and reducing evaporation losses.

[0003] There are four main types of passive insulation for cryogenic storage tanks: conventional bulk insulation, hollow powder insulation, vacuum insulation, and high-vacuum multilayer insulation. High-vacuum multilayer insulation and hollow glass microsphere insulation are the most widely used in cryogenic storage tanks. Furthermore, adding air cooling screens to the passive insulation structure can further utilize the cooling energy from the evaporation of cryogenic liquids and reduce heat leakage losses. Existing literature primarily uses two approaches to measure the apparent thermal conductivity of cryogenic tank insulation materials.

[0004] One is to use the evaporation calorimetry method mentioned in the Chinese patent application with publication number CN111307485A. This patent application provides a simplified apparent thermal conductivity test system. The main equipment of the experimental system includes an upper protective chamber, a lower protective chamber and a test chamber. During the test, the upper protective chamber and the lower protective chamber are interconnected, and the chambers are filled with a low-temperature working fluid to reduce the influence of heat leakage at the upper and lower ends of the test chamber, thereby improving the reliability of the measurement results of the thermal insulation material. The amount of heat leakage can be calculated by the mass flow rate of the gas evaporated out of the test chamber. In order to obtain the amount of heat leakage at different thermal boundary temperatures, a thermal conductive copper tape is used to connect the upper protective chamber and the thermal boundary temperature simulation screen, thereby utilizing the cooling capacity of the low-temperature working fluid in the upper protective chamber, combined with the electric heating film configured on the thermal boundary temperature simulation screen to achieve temperature control. This method is mostly used for the apparent thermal conductivity test of multi-layer thermal insulation materials.

[0005] The second method utilizes the steady-state method described in Chinese patent application publication number CN119470552A. During the test, a GM refrigerator provides the cold boundary temperature, while a heater with known heating power is inserted into the center of the sample to provide the hot boundary temperature. After heat transfer reaches steady state, the apparent thermal conductivity of the test sample can be calculated based on the stable temperature distribution. This method can be used to test the apparent thermal conductivity of hollow glass microspheres.

[0006] The devices for measuring apparent thermal conductivity using evaporation calorimetry in the aforementioned existing literature are mostly applicable to the liquid nitrogen temperature range. Expanding this to the liquid hydrogen temperature range requires further refinement of the liquid hydrogen filling and discharge processes. Furthermore, the temperature control method for the thermal boundary temperature simulation screen results in significant consumption of cryogenic fluid, especially when the thermal boundary temperature is above 0°C. The devices for measuring apparent thermal conductivity using the steady-state method in the aforementioned existing literature are only applicable to hollow glass microspheres and cannot be expanded to different types of insulation materials. Summary of the Invention

[0007] In order to solve the above-mentioned problems of the prior art, the present invention provides a system and method for testing the apparent thermal conductivity of liquid hydrogen storage tank insulation materials, which realizes the measurement of the apparent thermal conductivity of different types of insulation materials of liquid hydrogen storage tanks at different thermal boundary temperatures.

[0008] The present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a system for testing the apparent thermal conductivity of thermal insulation materials of liquid hydrogen storage tanks, comprising a calorimeter, a vacuum pumping device, a displacement device, a liquid hydrogen injection device, an exhaust device, and a data acquisition device. An upper protective chamber (32), a test chamber (33), and a lower protective chamber (34) are sequentially arranged in a closed space in the calorimeter from top to bottom; the upper protective chamber (32) and the lower protective chamber (34) are connected by a pipeline; the side walls of the upper protective chamber (32), the test chamber (33), and the lower protective chamber (34) as well as the top of the upper protective chamber (32) and the bottom of the lower protective chamber (34) are all covered with a thermal insulation material (31); a thermal boundary temperature controller (28) is arranged on the periphery of the upper protective chamber (32), the test chamber (33), and the lower protective chamber (34); a copper block (37) is arranged in the upper protective chamber (32), and the copper block (37) is connected to the thermal boundary temperature controller (28) through a copper wire (36); a water cooling coil (35) is arranged on the side wall of the calorimeter; The vacuuming device is used to vacuum the enclosed space in the calorimeter; the replacement device is used to replace the air in the upper protection chamber (32), the test chamber (33) and the lower protection chamber (34) with hydrogen; the liquid hydrogen injection device is used to inject liquid hydrogen into the upper protection chamber (32), the test chamber (33) and the lower protection chamber (34); the exhaust device is used to discharge the gas exhausted from the protection chamber (32), the test chamber (33) and the lower protection chamber (34); and the data acquisition device is used to measure the flow rate of the volatilized hydrogen in the test chamber (33), the temperature of the outer wall of the test chamber (33) and the temperature of the outer wall of the insulation material or the inner wall of the thermal boundary temperature controller.

[0009] Preferably, the width of the interlayer space between the test cavity (33) and the thermal boundary temperature controller (28) is greater than 0.3 m; and the thermal insulation material (31) is a multilayer thermal insulation material or hollow glass microspheres.

[0010] Preferably, the liquid hydrogen injection device comprises a liquid hydrogen storage tank (8), a first cryogenic shut-off valve (9), a second cryogenic shut-off valve (16), and a third cryogenic shut-off valve (17); the outlet of the liquid hydrogen storage tank (8) is connected to the inlet of the upper protection chamber (32) via the first cryogenic shut-off valve (9) and the second cryogenic shut-off valve (16) in sequence; and the outlet of the liquid hydrogen storage tank (8) is connected to the inlet of the test chamber (33) via the first cryogenic shut-off valve (9) and the third cryogenic shut-off valve (17) in sequence.

[0011] Furthermore, the outlet of the first low-temperature stop valve (9) is connected to the exhaust device via the second gate valve (10) and the first safety valve (11), respectively, and the second gate valve (10) and the first safety valve (11) are connected in parallel.

[0012] Preferably, the replacement device comprises a hydrogen cylinder (13), a third gate valve (12), a fourth gate valve (14) and a first nitrogen cylinder (15); the outlet of the hydrogen cylinder (13) is connected to the inlet of the upper protection chamber (32) and the inlet of the test chamber (33) respectively through the third gate valve (12); and the outlet of the first nitrogen cylinder (15) is connected to the inlet of the upper protection chamber (32) and the inlet of the test chamber (33) respectively through the fourth gate valve (14).

[0013] Furthermore, the replacement device further comprises a gas collecting bottle (4), a first gate valve (3) and a hydrogen concentration detector (5), wherein the inlet of the gas collecting bottle (4) is connected to the exhaust device via the first gate valve (3), and the hydrogen concentration detector (5) is used to measure the concentration of hydrogen in the gas collecting bottle (4).

[0014] Preferably, the data acquisition device includes a thermometer group (29) and a mass flow meter (42); the thermometer group (29) is used to measure the temperature of the outer wall of the test cavity (33) and the temperature of the outer wall of the insulation material or the inner wall of the thermal boundary temperature controller; the mass flow meter (42) is used to measure the flow rate of the volatilized hydrogen in the test cavity (33).

[0015] Furthermore, the exhaust device includes: a second pressure sensor (43), a sixth gate valve (44), a fifth safety valve (45), a second safety valve (38), a fifth gate valve (39), a first pressure sensor (40), a gas heater (41), a mass flow meter (42) and a high-altitude exhaust tower (2); The outlet of the upper protection chamber (32) is connected to the high-altitude discharge tower (2) via the second pressure sensor (43) and the sixth gate valve (44), and the fifth safety valve (45) is connected in parallel with the sixth gate valve (44); the outlet of the test chamber (33) is connected to the high-altitude discharge tower (2) via the fifth gate valve (39), the first pressure sensor (40), the gas heater (41), and the mass flow meter (42) in sequence, and the outlet of the test chamber (33) is also connected to the high-altitude discharge tower (2) via the second safety valve (38).

[0016] Furthermore, a molecular sealer (1) is installed on the top of the high-altitude discharge tower (2).

[0017] In a second aspect, the present invention provides a method for testing the apparent thermal conductivity of insulation materials for liquid hydrogen storage tanks, based on the system described above, comprising the following steps: S1, using a vacuum device to evacuate the sealed space in the calorimeter; S2, using a replacement device to replace the air in the upper protection chamber (32), the test chamber (33), and the lower protection chamber (34) with hydrogen; S3, injecting liquid hydrogen into the upper protection cavity (32), the lower protection cavity (34), and the test cavity (33) using a liquid hydrogen injection device; controlling the thermal boundary temperature using a thermal boundary temperature controller (28) or a water cooling coil (35); S4, measuring the flow rate of volatilized hydrogen in the test chamber (33), measuring the temperature of the outer wall of the insulation material or the inner wall of the thermal boundary temperature controller (18), and measuring the temperature of the outer wall of the test chamber (33); and calculating the apparent thermal conductivity of the liquid hydrogen storage tank insulation material based on the measured flow rate and temperature.

[0018] Compared with the prior art, the present invention has the following beneficial effects: The present invention's system for testing the apparent thermal conductivity of insulation materials for liquid hydrogen storage tanks includes a water-cooling coil installed on the sidewalls of the calorimeter and thermal boundary temperature controllers installed on the peripheries of the upper protective chamber, the test chamber, and the lower protective chamber. The thermal boundary temperature controller enables low-temperature thermal boundary temperature control, while the water-cooling coil enables thermal boundary temperature control above 0°C, without causing significant consumption of cryogenic fluid. Therefore, the system of the present invention is capable of measuring the apparent thermal conductivity of insulation materials at different thermal boundary temperatures. Furthermore, the thermal boundary temperature controller of the present invention is connected to the liquid hydrogen in the upper protective chamber via copper wires, enabling utilization of cooling capacity.

[0019] Furthermore, the present invention takes into account the testing requirements of hollow glass microspheres and adjusts the distance between the test cavity and the thermal boundary so that it can accommodate both multi-layer insulation materials and hollow glass microspheres, thereby meeting both the requirements of multi-layer insulation materials and the measurement requirements of hollow glass microspheres, and realizing performance testing of different types of insulation materials.

[0020] Furthermore, in the liquid hydrogen injection device of the present invention, the outlet of the first cryogenic stop valve is connected to the exhaust device via the second gate valve and the first safety valve respectively. After the injection of liquid hydrogen into the upper protection chamber, the lower protection chamber and the test chamber is completed, the gas evaporated from the liquid hydrogen between the first cryogenic stop valve and the second cryogenic stop valve and the third cryogenic stop valve can be discharged through the exhaust device, thereby avoiding the risk of excessive pressure caused by continuous evaporation of liquid hydrogen in this section of the pipeline, resulting in leakage of the pipeline.

[0021] Furthermore, the replacement device of the present invention includes a hydrogen cylinder and a first nitrogen cylinder. Before the liquid hydrogen is injected, nitrogen is introduced into the upper protection cavity, the lower protection cavity and the test cavity through the first nitrogen cylinder to achieve air replacement. After that, the nitrogen injection is stopped and hydrogen is injected through the hydrogen cylinder to complete the nitrogen replacement, and finally the air is replaced by hydrogen. If hydrogen is directly used to replace the air, the hydrogen concentration in the cavity will inevitably pass through the explosion concentration range (such as the hydrogen concentration in a local area of the air reaches 4% to 75%). At this time, if there is static electricity, metal friction sparks or high temperature, it will cause a violent explosion. Nitrogen is an inert gas with stable chemical properties and is non-flammable. The present invention first replaces the air with nitrogen, which can reduce the oxygen (O2) concentration to a safe level (usually <1%), eliminating the possibility of explosion at the source.

[0022] Furthermore, the hydrogen generated during the liquid hydrogen experiment of the present invention can be discharged through a high-altitude discharge tower. A molecular sealer is provided at the top of the high-altitude discharge tower to prevent air from flowing back into the high-altitude discharge tower. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 Schematic diagram of the apparent thermal conductivity testing system for liquid hydrogen storage tank insulation materials of the present invention.

[0025] 1—Molecular sealer; 2—High-altitude discharge tower; 3—First gate valve; 4—Gas collecting bottle; 5—Hydrogen concentration detector; 6—First cryogenic refrigerator; 7—Second cryogenic refrigerator; 8—Liquid hydrogen storage tank; 9—First cryogenic stop valve; 10—Second gate valve; 11—First safety valve; 12—Third gate valve; 13—Hydrogen bottle; 14—Fourth gate valve; 15—First nitrogen bottle; 16—Second cryogenic stop valve; 17—Third cryogenic stop valve; 18—Vacuum pump; 19—First high vacuum gate valve; 20—Second nitrogen bottle; 21—Nitrogen heater; 22—Second high vacuum gate valve Valve; 23—first vacuum gauge; 24—neck tube; 25—second vacuum gauge; 26—calorimeter cover; 27—calorimeter housing; 28—thermal boundary temperature controller; 29—thermometer group; 30—air cooling screen; 31—insulation material; 32—upper protection chamber; 33—test chamber; 34—lower protection chamber; 35—water cooling coil; 36—copper wire; 37—copper block; 38—fifth gate valve; 39—second safety valve; 40—sixth gate valve; 41—first pressure sensor; 42—gas heater; 43—sixth gate valve; 44—mass flowmeter; 45—eighth gate valve.

[0026] Figure 2 This is a schematic diagram of the multi-layer thermal insulation material for liquid hydrogen storage tanks of the present invention.

[0027] 46—Multi-layer insulation material.

[0028] Figure 3 Schematic diagram of the hollow glass microsphere insulation material for the liquid hydrogen storage tank of the present invention; (a) is a schematic diagram of the filling of the hollow glass microsphere insulation material; (b) is an enlarged view of the hollow glass microsphere insulation material.

[0029] 47—Filter; 48—Hollow glass microspheres. DETAILED DESCRIPTION

[0030] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0031] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0032] It should be noted that the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Furthermore, unless otherwise specified, the numbering of each method step is merely a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or to define the scope of the invention. Changes or adjustments to their relative relationships, without substantially changing the technical content, should also be considered within the scope of the invention.

[0033] Furthermore, it should be noted that the terms "first," "second," and the like are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than that illustrated or described herein. The terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" and the like, indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended solely for the purpose of facilitating the description of the present invention and simplifying the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present invention. Furthermore, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly, for example, to mean a fixed connection or a detachable connection; a direct connection or an indirect connection through an intermediate medium; or internal communication between two components.

[0034] The system for testing the apparent thermal conductivity of insulation materials for liquid hydrogen storage tanks disclosed herein comprises a calorimeter, a vacuum pump, a displacement device, a liquid hydrogen injection device, an exhaust device, and a data acquisition device. An upper protective chamber 32, a test chamber 33, and a lower protective chamber 34 are sequentially arranged in the enclosed space within the calorimeter from top to bottom. The upper protective chamber 32 and the lower protective chamber 34 are connected by a pipe. The side walls of the upper protective chamber 32, the test chamber 33, and the lower protective chamber 34, as well as the top of the upper protective chamber 32 and the bottom of the lower protective chamber 34 are all coated with insulating material 31. A thermal boundary temperature controller 28 is arranged on the periphery of the upper protective chamber 32, the test chamber 33, and the lower protective chamber 34. A copper block 37 is arranged in the upper protective chamber 32, and the copper block 37 is connected to the thermal boundary temperature controller 28 via a copper wire 36. A water cooling coil 35 is provided on the side wall of the calorimeter. The vacuuming device is used to vacuum the enclosed space in the calorimeter; the replacement device is used to replace the air in the upper protection cavity 32, the test cavity 33 and the lower protection cavity 34 with hydrogen; the liquid hydrogen injection device is used to inject liquid hydrogen into the upper protection cavity 32, the test cavity 33 and the lower protection cavity 34; the exhaust device is used to discharge the gas discharged from the protection cavity 32, the test cavity 33 and the lower protection cavity 34; the data acquisition device is used to measure the flow rate of the volatilized hydrogen in the test cavity 33, the temperature of the outer wall of the test cavity (33) and the temperature of the outer wall of the insulation material or the inner wall of the thermal boundary temperature controller.

[0035] The present invention's apparent thermal conductivity testing system for liquid hydrogen storage tank insulation materials includes a water-cooling coil 35 installed on the sidewall of the calorimeter and a thermal boundary temperature controller 28 installed around the upper protective chamber 32, the test chamber 34, and the lower protective chamber 34. The water-cooling coil enables normal-temperature thermal boundary temperature control. During the experiment, the mass flow rate is adjusted to maintain the temperature difference between the inlet and outlet of the water-cooling coil within 2°C. Low-temperature thermal boundary temperature control is achieved through the thermal boundary temperature controller. The thermal boundary temperature controller is connected to the liquid hydrogen in the upper protective chamber via copper wires to utilize cooling energy. Furthermore, an electric heating plate is installed on the thermal boundary temperature controller. The combination of the two enables thermal boundary temperature control. Therefore, the present invention's system is capable of measuring the apparent thermal conductivity of insulation materials at different thermal boundary temperatures.

[0036] To better accommodate different insulation materials, the interlayer space between the test chamber 33 and the thermal boundary temperature controller 28 is preferably set to a width of at least 0.3 m. This is because multilayer insulation materials require less interlayer space, while hollow glass microspheres require more. To test the performance of different insulation materials, control of the interlayer space is necessary. Consequently, the system of the present invention is capable of measuring the apparent thermal conductivity of different insulation materials (multilayer insulation materials and hollow glass microspheres).

[0037] In order to adapt to the measurement of hollow glass microspheres, the inlet position of the vacuum pump 18 of the present invention is designed with a filter 47 to prevent the hollow glass microspheres from being sucked into the vacuum pump 18. Since the particle size of the hollow glass microspheres can be as low as 30 μm, the mesh number of the filter 48 needs to be as high as 500 mesh or more. At this time, the vacuum pump 18 can meet the vacuum requirements by using a mechanical pump, and the pressure requirement is less than 10 Pa. When the insulation material uses multi-layer insulation material 46, the vacuum pump 18 can meet the vacuum requirements by using a mechanical pump combined with a molecular pump, and the pressure requirement is less than 10 Pa. -2 Pa.

[0038] In some preferred embodiments of the present invention, the calorimeter includes a calorimeter housing 27 and a calorimeter cover 26. The calorimeter cover 26 is attached to the top of the calorimeter housing 27 to form a sealed space. The upper protective cavity 32 is connected to the calorimeter cover 26 via a neck tube 24. A first vacuum gauge 23 and a second vacuum gauge 25 are mounted on the calorimeter cover 26. The first vacuum gauge 23 is used to measure the pressure between the insulation layers, and the second vacuum gauge 25 is used to measure the pressure within the sealed space.

[0039] In some preferred embodiments of the present invention, the vacuum pumping device includes: a vacuum pump 18, a first high vacuum gate valve 19, a second nitrogen bottle 20, a nitrogen heater 21 and a second high vacuum gate valve 22; the outlet of the second nitrogen bottle 20 is connected to the calorimeter via the nitrogen heater 21 and the second high vacuum gate valve 22 in sequence, and the outlet of the vacuum pump 18 is connected to the side wall of the calorimeter via the first high vacuum gate valve 19.

[0040] The vacuum pump 18 is used to evacuate the enclosed space, and the nitrogen heater 21 is used to heat the nitrogen flowing out of the second nitrogen bottle 20 and enter the enclosed space through the second high vacuum gate valve 22, thereby replacing the enclosed space with hot gas and shortening the vacuuming time.

[0041] In some preferred embodiments of the present invention, the liquid hydrogen injection device includes a liquid hydrogen storage tank 8, a first cryogenic shut-off valve 9, a second cryogenic shut-off valve 16, and a third cryogenic shut-off valve 17. The outlet of the liquid hydrogen storage tank 8 is connected to the inlet of the upper protective chamber 32 via the first cryogenic shut-off valve 9 and the second cryogenic shut-off valve 16, respectively. The outlet of the liquid hydrogen storage tank 8 is connected to the inlet of the test chamber 33 via the first cryogenic shut-off valve 9 and the third cryogenic shut-off valve 17, respectively. The liquid hydrogen storage tank 8 is provided with a first cryogenic refrigerator 6 and a second cryogenic refrigerator 7 for preparing cryogenic liquid hydrogen.

[0042] The liquid hydrogen in the liquid hydrogen storage tank 8 is injected into the upper protection chamber 32 through the first cryogenic shut-off valve 9 and the second cryogenic shut-off valve 16, and is injected into the test chamber 33 through the first cryogenic shut-off valve 9 and the third cryogenic shut-off valve 17, thereby realizing the injection of liquid hydrogen. Preferably, the outlet of the first cryogenic shut-off valve 9 is connected to the exhaust device through the second gate valve 10 and the first safety valve 11, respectively, and the second gate valve 10 and the first safety valve 11 are connected in parallel. After the injection of liquid hydrogen is completed, in order to avoid the risk of leakage caused by excessive pipeline pressure due to the evaporation of liquid hydrogen in the liquid hydrogen filling pipeline between the first cryogenic shut-off valve 9, the second cryogenic shut-off valve 16 and the third cryogenic shut-off valve 17, the evaporated gas of liquid hydrogen is discharged through the second gate valve 10 and the exhaust device.

[0043] In some preferred embodiments of the present invention, the replacement device includes a hydrogen cylinder 13, a third gate valve 12, a fourth gate valve 14 and a first nitrogen cylinder 15; the outlet of the hydrogen cylinder 13 is connected to the inlet of the upper protection chamber 32 and the inlet of the test chamber 33 respectively through the third gate valve 12; the outlet of the first nitrogen cylinder 15 is connected to the inlet of the upper protection chamber 32 and the inlet of the test chamber 33 respectively through the fourth gate valve 14.

[0044] During implementation, the air in the upper protection chamber 32 , the lower protection chamber 34 and the test chamber 33 is first replaced with nitrogen, and then the nitrogen is replaced with hydrogen.

[0045] In some specific embodiments, the replacement device also includes a gas collecting bottle 4, a first gate valve 3 and a hydrogen concentration detector 5. The inlet of the gas collecting bottle 4 is connected to the exhaust device through the first gate valve 3. The hydrogen concentration detector 5 is used to measure the concentration of hydrogen in the gas collecting bottle 4.

[0046] During implementation, after replacing nitrogen with hydrogen, the gas in the exhaust device is collected by a gas collecting bottle 4 to measure the concentration of hydrogen, thereby determining whether the hydrogen concentrations in the upper protection chamber 32, the lower protection chamber 34 and the test chamber 33 meet the requirements.

[0047] In some preferred embodiments of the present invention, the data acquisition device includes a thermometer group 29 and a mass flowmeter 42; the thermometer group 29 is used to measure the temperature of the outer wall of the test chamber 33 and the temperature of the outer wall of the insulation material (when using multi-layer insulation material) or the inner wall of the thermal boundary temperature controller (when using hollow glass microspheres); the mass flowmeter 42 is used to measure the flow rate of volatilized hydrogen in the test chamber 33, and calculate the apparent thermal conductivity of the liquid hydrogen storage tank insulation material based on the measured flow rate and temperature.

[0048] In some preferred embodiments of the present invention, the exhaust device includes: a second pressure sensor 43, a sixth gate valve 44, a fifth safety valve 45, a second safety valve 38, a fifth gate valve 39, a first pressure sensor 40, a gas heater 41, and a high-altitude exhaust tower 2. The outlet of the upper protection chamber 32 is connected to the high-altitude exhaust tower 2 via the second pressure sensor 43 and the sixth gate valve 44, and the third safety valve 45 is connected in parallel with the sixth gate valve 44. The outlet of the test chamber 33 is connected to the high-altitude exhaust tower 2 via the fifth gate valve 39, the first pressure sensor 40, the gas heater 41, and the mass flowmeter 42 in sequence. The outlet of the test chamber 33 is also connected to the high-altitude exhaust tower 2 via the second safety valve 38. The gas in the upper and lower protection chambers 32 and 34 is discharged to the high-altitude exhaust tower 2 via the second pressure sensor 43 and the sixth gate valve 44, and then discharged through the high-altitude exhaust tower 2. The third safety valve 45 is used to prevent the sixth gate valve 44 from failing to open due to experimental misoperation, which would cause excessive gas pressure in the upper protection chamber and pose a risk of leakage. When the pressure in the upper protection chamber reaches 0.4 MPa, the third safety valve 45 automatically opens. The gas in the test chamber 33 is discharged through the fifth gate valve 39, the first pressure sensor 40, the gas heater 41, the mass flow meter 42 and the high-altitude discharge tower 2.

[0049] In some specific embodiments, a molecular sealer 1 is installed on the top of the high-altitude discharge tower 2 , and a slight positive pressure is formed in the molecular sealer 1 to prevent air from flowing back into the high-altitude discharge tower 2 .

[0050] In some preferred embodiments of the present invention, an air-cooling shield 30 is provided outside the test chamber 33. The air-cooling shield 30 is arranged around the test chamber 33 and is connected to the top outlet of the test chamber 33. At this time, the outlet of the air-cooling shield 30 is connected to the fifth gate valve 39 and the second safety valve 38 in the exhaust device.

[0051] The method for testing the apparent thermal conductivity of the liquid hydrogen storage tank insulation material of the present invention comprises the following steps: S1, using a vacuum device to evacuate the sealed space in the calorimeter; S2, using a replacement device to replace the air in the upper protection chamber 32, the test chamber 33 and the lower protection chamber 34 with hydrogen; S3, using a liquid hydrogen injection device to inject liquid hydrogen into the upper protection cavity 32, the lower protection cavity 34 and the test cavity 33; controlling the thermal boundary temperature by a thermal boundary temperature controller or a water cooling coil; S4, measuring the flow rate of volatilized hydrogen in the test chamber 33, measuring the temperature of the outer wall of the insulation material or the inner wall of the thermal boundary temperature controller, and measuring the temperature of the outer wall of the test chamber; calculating the apparent thermal conductivity of the liquid hydrogen storage tank insulation material based on the measured flow rate and temperature.

[0052] Example refer to Figure 1 In the embodiment of the present invention, the apparent thermal conductivity test system of the insulation material of the liquid hydrogen storage tank includes: a molecular sealer 1; a high-altitude discharge tower 2; a first gate valve 3; a gas collecting bottle 4; a hydrogen concentration detector 5; a first low-temperature refrigerator 6; a second low-temperature refrigerator 7; a liquid hydrogen storage tank 8; a first low-temperature stop valve 9; a second gate valve 10; a first safety valve 11; a third gate valve 12; a hydrogen bottle 13; a fourth gate valve 14; a first nitrogen bottle 15; a second low-temperature stop valve 16; a third low-temperature stop valve 17; a vacuum pump 18; a first high-vacuum gate valve 19; a second nitrogen bottle 20; a nitrogen pump Calorimeter 21; second high vacuum gate valve 22; first vacuum gauge 23; neck tube 24; second vacuum gauge 25; calorimeter cover 26; calorimeter housing 27; thermal boundary temperature controller 28; thermometer assembly 29; air cooling shield 30; insulation material 31; upper protective chamber 32; test chamber 33; lower protective chamber 34; water cooling coil 35; copper wire 36; copper block 37; second safety valve 38; fifth gate valve 39; first pressure sensor 40; gas heater 41; mass flow meter 42; second pressure sensor 43; sixth gate valve 44; third safety valve 45; filter 46.

[0053] The water-cooling coil 35, vacuum pump 18, first high-vacuum gate valve 19, second nitrogen bottle 20, nitrogen heater 21, and second high-vacuum gate valve 22 are mounted on the calorimeter housing 27. The outlet of the second nitrogen bottle 20 is connected to the calorimeter housing 27 via the nitrogen heater 21 and second high-vacuum gate valve 22, respectively. The outlet of the vacuum pump 18 is connected to the calorimeter housing 27 via the first high-vacuum gate valve 19. The first and second vacuum gauges 23 and 25 are mounted on the calorimeter cover 26. The calorimeter housing 27 and the calorimeter cover 26 form a sealed space. The upper protective chamber 32, test chamber 33, lower protective chamber 34, thermal boundary temperature controller 28, and air cooling shield 30 are mounted within this sealed space. The upper protective chamber 32 is connected to the calorimeter cover 26 via the neck tube 24. The vacuum pump 18 is used to evacuate the sealed space. The second nitrogen cylinder 20 and the second high vacuum gate valve 22 are used to replace hot gas in the enclosed space, accelerating the vacuum pumping process. The first vacuum gauge 23 is used to measure the pressure between the insulation layers; the second vacuum gauge 25 is used to measure the pressure in the enclosed space. The upper protective chamber 32 and the lower protective chamber 34 are connected by a pipe; the air cooling shield 30 is arranged around the test chamber 33 and connected to the top of the test chamber 33. The copper block 37 is installed in the upper protective chamber 32. The thermal boundary temperature controller 28 is located outside the upper protective chamber 32, the test chamber 33, and the lower protective chamber 34 and is connected to the copper block 37 via copper wire 36.

[0054] The side walls of the upper protection cavity 32, the test cavity 33 and the lower protection cavity 34 as well as the top of the upper protection cavity 32 and the bottom of the lower protection cavity 34 are all covered with a heat insulating material 31. The heat insulating material 31 can be made of multiple layers of heat insulating material 46 (such as Figure 2 As shown) or hollow glass microspheres 48 (as Figure 3 When installing the hollow glass microspheres 48, a filter 47 is installed at the air inlet of the vacuum pump 18 to prevent the hollow glass microspheres 48 from being sucked back into the vacuum pump 18. At this time, the vacuum pump 18 can use a mechanical pump to meet the vacuum requirements, and the pressure requirement is less than 10 Pa. When installing the multi-layer insulation material 46, the vacuum pump 18 can use a mechanical pump combined with a molecular pump to meet the vacuum requirements, and the pressure requirement is less than 10 -2 Pa.

[0055] The upper protection chamber 32 and the test chamber 33 of the present invention are both connected to liquid hydrogen filling pipelines. The liquid hydrogen storage tank 8 is connected to the upper protection chamber 32 and the test chamber 33 via the liquid hydrogen filling pipelines. The liquid hydrogen filling pipelines include a main liquid hydrogen filling pipeline, a first branch liquid hydrogen filling pipeline, and a second branch liquid hydrogen filling pipeline. The outlet of the liquid hydrogen storage tank 8 is connected to the inlets of the first branch liquid hydrogen filling pipeline and the second branch liquid hydrogen filling pipeline via the main liquid hydrogen filling pipeline. The outlet of the first branch liquid hydrogen filling pipeline is connected to the upper protection chamber 32, and the outlet of the second branch liquid hydrogen filling pipeline is connected to the test chamber 33. The main liquid hydrogen filling pipeline is provided with a first cryogenic shut-off valve 9. The first branch liquid hydrogen filling pipeline is provided with a second cryogenic shut-off valve 16, and the second branch liquid hydrogen filling pipeline is provided with a third cryogenic shut-off valve 17. The first and second cryogenic refrigerators 6 and 7 are installed on the liquid hydrogen storage tank 8 to prepare cryogenic liquid hydrogen. The outlet of the hydrogen cylinder 13 is connected to the outlet of the first cryogenic shut-off valve 9 via the third gate valve 12, and the outlet of the first nitrogen cylinder 15 is connected to the outlet of the first cryogenic shut-off valve 9 via the fourth gate valve 14. The first nitrogen cylinder 15 and the hydrogen cylinder 13 are used to replace air and hydrogen in the upper protection chamber 32, the test chamber 33, and the lower protection chamber 34 before filling with liquid hydrogen.

[0056] The outlet of the first cryogenic shut-off valve 9 is connected to the high-altitude discharge tower 2 via the second gate valve 10 and the first safety valve 11. The second gate valve 10 and the first safety valve 11 are connected in parallel. The second gate valve 10 is used to discharge hydrogen from the liquid hydrogen filling pipeline between the first cryogenic shut-off valve 9, the second cryogenic shut-off valve 16, and the third cryogenic shut-off valve 17 after liquid hydrogen filling is completed.

[0057] The second pressure sensor 43, sixth gate valve 44, and fifth safety valve 45 of the present invention connect the upper protection chamber 32 to the high-altitude discharge tower 2 via an exhaust duct. Specifically, the outlet of the upper protection chamber 32 is connected to the high-altitude discharge tower 2 via the second pressure sensor 43 and sixth gate valve 44, with the fifth safety valve 45 and sixth gate valve 44 connected in parallel. During experiments, evaporated hydrogen within the upper protection chamber 32 was discharged into the high-altitude discharge tower 2 via the sixth gate valve 44. A molecular seal 1 is installed at the top of the high-altitude discharge tower 2, creating a slight positive pressure within the seal to prevent air from flowing back into the high-altitude discharge tower 2.

[0058] The second safety valve 38, fifth gate valve 39, first pressure sensor 40, gas heater 41, and mass flowmeter 42 of the present invention connect the test chamber 33 to the high-altitude discharge tower 2 via an exhaust duct. Specifically, the outlet of the air-cooled shield 30 outside the test chamber 33 is connected to the high-altitude discharge tower 2 via the fifth gate valve 39, first pressure sensor 40, gas heater 41, and mass flowmeter 42. The outlet of the air-cooled shield 30 outside the test chamber 33 is also connected to the high-altitude discharge tower 2 via the second safety valve 38. The gas heater 41 heats the low-temperature hydrogen to room temperature, preventing it from affecting the mass flowmeter 42; the mass flowmeter 42 measures the flow rate of hydrogen evaporated within the test chamber 33.

[0059] The gas collecting bottle 4 of the present invention is connected to the inlet of the high-altitude exhaust tower 2 via the first gate valve 3. The hydrogen concentration detector 5 is used to measure the hydrogen concentration in the gas collecting bottle 4. After the hydrogen exchange is completed, the gas collecting bottle 4 collects the gas in the exhaust pipe, and the hydrogen concentration in the gas collecting bottle 4 is measured using the hydrogen concentration detector 5. If the hydrogen concentration in the hydrogen concentration detector 5 reaches 96%, the hydrogen exchange is stopped; otherwise, the hydrogen exchange is continued.

[0060] The water-cooling coil 35 of the present invention is used to control the normal temperature thermal boundary. During the experiment, the mass flow rate is adjusted to control the temperature difference between the inlet and outlet of the water-cooling coil within 2°C. The thermal boundary temperature controller 28 is used for low-temperature thermal boundary control. During the experiment, the thermal boundary temperature controller 28 is connected to the liquid hydrogen in the upper protective cavity 32 through the copper wire 36 and the copper block 37 to realize the utilization of the cooling capacity. The power of the electric heating plate on the surface of the thermal boundary temperature controller 28 is adjusted to control the temperature of the thermal boundary temperature controller. In addition, in order to achieve thermal boundary temperature control at the required temperature, the number of copper wires required for the thermal boundary temperature controller can be calculated and determined by the commercial software ANSYS FLUENT.

[0061] In the embodiment of the present invention, the first vacuum gauge 23 is preferably an ionization gauge, and the second vacuum gauge 25 is preferably a full-range gauge.

[0062] In the embodiment of the present invention, the thermal boundary temperature controller 28 is preferably made of copper.

[0063] In the embodiment of the present invention, the vacuum pump 18 is preferably a mechanical pump combined with a molecular pump. When the insulating material is hollow glass microspheres, preferably, the molecular pump is turned off and only the mechanical pump is turned on.

[0064] The method for testing the apparent thermal conductivity of the liquid hydrogen storage tank insulation material of the present invention, when using a multi-layer insulation material, comprises the following steps: Step 1: Close all valves, adjust the temperature of the thermal boundary temperature controller 28 to 100°C, open the first high-altitude gate valve 19, the second high-altitude gate valve 22, and the second nitrogen bottle 20, use the nitrogen heater 21 to heat the nitrogen to 100°C, start the vacuum pump 18, and combine the 100°C high-temperature nitrogen purge to evacuate the closed space formed by the calorimeter housing 27 and the calorimeter cover 26. Repeat the high-temperature nitrogen purge and evacuate the closed space 5 times, close the second nitrogen bottle 20, the nitrogen heater 21, and the second high vacuum valve 22, and evacuate to 10 -2 Pa below for at least 24 hours; Step 2: Open the first nitrogen cylinder 15, the fourth gate valve 14, the second cryogenic shut-off valve 16, the third cryogenic shut-off valve 17, the fifth gate valve 39, and the sixth gate valve 44 to replace the air in the upper protection chamber 32, the test chamber 33, and the lower protection chamber 34. Close the first nitrogen cylinder 15, the fourth gate valve 14, the fifth gate valve 39, and the sixth gate valve 44. Open the hydrogen cylinder 13 and the third gate valve 12. When the pressure values of the first pressure sensor 40 and the second pressure sensor 43 reach 0.3 MPa, close the hydrogen cylinder 13 and the third gate valve 12 and maintain pressure for 5 minutes. Open the fifth gate valve 39 and the sixth gate valve 44 to release the gas from the upper protection chamber 32, the test chamber 33, the lower protection chamber 34, and the pipeline. Repeat this process 10 times. Open the first gate valve 7 and use the gas collecting cylinder 4 to collect hydrogen. Close the first gate valve 3 and use the hydrogen concentration detector 5 to test the hydrogen purity in the gas collecting cylinder 4.

[0065] Step 3: When the hydrogen purity detected by the hydrogen concentration detector 5 reaches above 96%, close the third cryogenic shut-off valve 17, open the first cryogenic shut-off valve 9 and the liquid hydrogen storage tank 8, and inject liquid hydrogen into the upper protection chamber 32 and the lower protection chamber 34. When the liquid hydrogen filling rate of the upper protection chamber reaches 50%, let it stand for 60 minutes, and then continue to add liquid hydrogen until the filling rate reaches 95%.

[0066] Step 4: Close the second cryogenic shut-off valve 16, open the third cryogenic shut-off valve 17, and inject liquid hydrogen into the test chamber 33. After the liquid hydrogen filling rate reaches 50%, let it stand for 60 minutes. Then continue to add liquid hydrogen until the filling rate reaches 95%. Close the first and third cryogenic shut-off valves 9 and 17, and open the second gate valve 10. After standing for 24 hours, close the second gate valve 10.

[0067] Step 5: When the liquid level in the upper protection chamber 32 falls below 20%, open the first and second cryogenic shut-off valves 9 and 16 to inject liquid hydrogen into the upper protection chamber 32. Repeat this process to ensure that liquid hydrogen is always present in both the upper and lower protection chambers. When the liquid hydrogen filling rate in the upper protection chamber 32 reaches 95%, close the first and second cryogenic shut-off valves 9 and 16.

[0068] Step 6: Record the reading of mass flow meter 42 every 10 minutes. When the flow rate variation range is less than 5% within one hour, the system is considered to have reached a steady state, and the average flow rate is calculated based on the recorded data. m , the apparent thermal conductivity of the insulation material can be further calculated according to formula (1).

[0069] (1) Where, h fg is the latent heat of vaporization of liquid hydrogen, J / Kg; d 0 is the outer diameter of the multi-layer insulation material 46, m; d i is the outer diameter of the test cavity 33, m; l is the length of the test cavity 33, m; is the temperature difference between the outer wall of the multi-layer insulation material and the outer wall of the test chamber, K.

[0070] The method for testing the apparent thermal conductivity of the liquid hydrogen storage tank insulation material of the present invention, when hollow glass microspheres are used, comprises the following steps: Step 1: Close all valves, adjust the temperature of the thermal boundary temperature controller 28 to 100°C, open the first high-altitude gate valve 19, the second high-altitude gate valve 22, and the second nitrogen cylinder 20, heat the nitrogen to 100°C using the nitrogen heater 21, start the vacuum pump 18, and evacuate the enclosed space formed by the calorimeter housing 27 and the calorimeter cover 26 by purging with 100°C high-temperature nitrogen. Repeat the high-temperature nitrogen purge process five times to evacuate the enclosed space. Close the second nitrogen cylinder 20, nitrogen heater 21, and the second high-vacuum valve 22, and evacuate to below 10 Pa and maintain for at least 24 hours.

[0071] Step 2: Open the first nitrogen cylinder 15, the fourth gate valve 14, the second cryogenic shut-off valve 16, the third cryogenic shut-off valve 17, the fifth gate valve 39, and the sixth gate valve 44 to replace the air. Close the first nitrogen cylinder 15, the fourth gate valve 14, the fifth gate valve 39, and the sixth gate valve 44. Open the hydrogen cylinder 13 and the third gate valve 12. When the pressure values of the first pressure sensor 40 and the second pressure sensor 43 reach 0.3 MPa, close the hydrogen cylinder 13 and the third gate valve 12 and maintain pressure for 5 minutes. Open the fifth gate valve 39 and the sixth gate valve 44 to release the gas from the upper protection chamber 32, the test chamber 33, the lower protection chamber 34, and the pipeline. Repeat this process 10 times. Open the first gate valve 3 and use the gas collecting cylinder 4 to collect hydrogen. Close the first gate valve 3 and use the hydrogen concentration detector 5 to test the purity of the hydrogen in the gas collecting cylinder 4.

[0072] Step 3: When the hydrogen purity detected by the hydrogen concentration detector 5 reaches above 96%, close the third cryogenic shut-off valve 17, open the first cryogenic shut-off valve 9 and the liquid hydrogen storage tank 8, and inject liquid hydrogen into the upper protection chamber 32 and the lower protection chamber 34. When the liquid hydrogen filling rate of the upper protection chamber reaches 50%, let it stand for 60 minutes, and then continue to add liquid hydrogen until the filling rate reaches 95%.

[0073] Step 4: Close the second cryogenic shut-off valve 16, open the third cryogenic shut-off valve 17, and inject liquid hydrogen into the test chamber 33. After the liquid hydrogen filling rate reaches 50%, let it stand for 60 minutes. Then continue to add liquid hydrogen until the filling rate reaches 95%. Close the first and third cryogenic shut-off valves 9 and 17, and open the second gate valve 10. After standing for 24 hours, close the second gate valve 10.

[0074] Step 5: When the liquid level in the upper protection chamber 32 falls below 20%, open the first and second cryogenic shut-off valves 9 and 16 to inject liquid hydrogen into the upper protection chamber 32. Repeat this process to ensure that liquid hydrogen is always present in both the upper and lower protection chambers. When the liquid hydrogen filling rate in the upper protection chamber 32 reaches 95%, close the first and second cryogenic shut-off valves 9 and 16.

[0075] Step 6: Record the reading of mass flow meter 42 every 10 minutes. When the flow rate variation range is less than 5% within one hour, the system is considered to have reached a steady state, and the average flow rate is calculated based on the recorded data. m , the apparent thermal conductivity of the insulation material can be further calculated according to formula (1).

[0076] (1) Where, h fg is the latent heat of vaporization of liquid hydrogen, J / Kg; d 0 is the inner diameter of the thermal boundary temperature controller 28, m; d i is the outer diameter of the test cavity 33, m; l is the length of the test cavity 33, m; is the temperature difference between the inner wall of the thermal boundary temperature controller and the outer wall of the test chamber, K.

[0077] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A liquid hydrogen storage tank insulation material apparent thermal conductivity test system, characterized in that: The invention comprises a calorimeter, a vacuum pumping device, a replacement device, a liquid hydrogen injection device, an exhaust device and a data acquisition device. An upper protection chamber (32), a test chamber (33) and a lower protection chamber (34) are sequentially arranged in a closed space in the calorimeter from top to bottom; the upper protection chamber (32) and the lower protection chamber (34) are connected by a pipeline; the side walls of the upper protection chamber (32), the test chamber (33) and the lower protection chamber (34) as well as the top of the upper protection chamber (32) and the bottom of the lower protection chamber (34) are all covered with a heat insulating material (31); a thermal boundary temperature controller (28) is arranged on the periphery of the upper protection chamber (32), the test chamber (33) and the lower protection chamber (34); a copper block (37) is arranged in the upper protection chamber (32), and the copper block (37) is connected to the thermal boundary temperature controller (28) through a copper wire (36); a water cooling coil (35) is arranged on the side wall of the calorimeter; The vacuuming device is used to vacuum the enclosed space in the calorimeter; the replacement device is used to replace the air in the upper protection chamber (32), the test chamber (33) and the lower protection chamber (34) with hydrogen; the liquid hydrogen injection device is used to inject liquid hydrogen into the upper protection chamber (32), the test chamber (33) and the lower protection chamber (34); the exhaust device is used to discharge the gas exhausted from the protection chamber (32), the test chamber (33) and the lower protection chamber (34); and the data acquisition device is used to measure the flow rate of the volatilized hydrogen in the test chamber (33), the temperature of the outer wall of the test chamber (33) and the temperature of the outer wall of the insulation material or the inner wall of the thermal boundary temperature controller.

2. The liquid hydrogen storage tank insulation material apparent thermal conductivity testing system according to claim 1 is characterized in that: The width of the interlayer space between the test cavity (33) and the thermal boundary temperature controller (28) is greater than 0.3 m; and the thermal insulation material (31) is a multilayer thermal insulation material or hollow glass microspheres.

3. The apparent thermal conductivity testing system for liquid hydrogen storage tank insulation materials according to claim 1 is characterized in that: The liquid hydrogen injection device comprises a liquid hydrogen storage tank (8), a first cryogenic stop valve (9), a second cryogenic stop valve (16), and a third cryogenic stop valve (17); the outlet of the liquid hydrogen storage tank (8) is connected to the inlet of the upper protection chamber (32) via the first cryogenic stop valve (9) and the second cryogenic stop valve (16) in sequence; and the outlet of the liquid hydrogen storage tank (8) is connected to the inlet of the test chamber (33) via the first cryogenic stop valve (9) and the third cryogenic stop valve (17) in sequence.

4. The apparent thermal conductivity testing system for liquid hydrogen storage tank insulation materials according to claim 3 is characterized in that: The outlet of the first low-temperature stop valve (9) is connected to the exhaust device via the second gate valve (10) and the first safety valve (11), respectively. The second gate valve (10) and the first safety valve (11) are connected in parallel.

5. The apparent thermal conductivity testing system for liquid hydrogen storage tank insulation materials according to claim 1 is characterized in that: The replacement device comprises a hydrogen cylinder (13), a third gate valve (12), a fourth gate valve (14) and a first nitrogen cylinder (15); the outlet of the hydrogen cylinder (13) is connected to the inlet of the upper protection chamber (32) and the inlet of the test chamber (33) respectively through the third gate valve (12); the outlet of the first nitrogen cylinder (15) is connected to the inlet of the upper protection chamber (32) and the inlet of the test chamber (33) respectively through the fourth gate valve (14).

6. The apparent thermal conductivity testing system for liquid hydrogen storage tank insulation materials according to claim 5 is characterized in that: The replacement device further comprises a gas collecting bottle (4), a first gate valve (3) and a hydrogen concentration detector (5). The inlet of the gas collecting bottle (4) is connected to the exhaust device via the first gate valve (3). The hydrogen concentration detector (5) is used to measure the concentration of hydrogen in the gas collecting bottle (4).

7. The liquid hydrogen storage tank insulation material apparent thermal conductivity testing system according to claim 1 is characterized in that: The data acquisition device includes a thermometer group (29) and a mass flow meter (42); the thermometer group (29) is used to measure the temperature of the outer wall of the test cavity (33) and the temperature of the outer wall of the insulation material or the inner wall of the thermal boundary temperature controller; The mass flow meter (42) is used to measure the flow rate of the volatilized hydrogen in the test chamber (33).

8. The apparent thermal conductivity testing system for liquid hydrogen storage tank insulation materials according to claim 7 is characterized in that: The exhaust device comprises: a second pressure sensor (43), a sixth gate valve (44), a fifth safety valve (45), a second safety valve (38), a fifth gate valve (39), a first pressure sensor (40), a gas heater (41), a mass flow meter (42) and a high-altitude exhaust tower (2); The outlet of the upper protection chamber (32) is connected to the high-altitude discharge tower (2) via the second pressure sensor (43) and the sixth gate valve (44), and the fifth safety valve (45) is connected in parallel with the sixth gate valve (44); the outlet of the test chamber (33) is connected to the high-altitude discharge tower (2) via the fifth gate valve (39), the first pressure sensor (40), the gas heater (41), and the mass flow meter (42) in sequence, and the outlet of the test chamber (33) is also connected to the high-altitude discharge tower (2) via the second safety valve (38).

9. The liquid hydrogen storage tank insulation material apparent thermal conductivity testing system according to claim 8, characterized in that: A molecular sealer (1) is installed on the top of the high-altitude discharge tower (2).

10. A method for testing the apparent thermal conductivity of liquid hydrogen storage tank insulation materials, characterized in that: Based on the system according to claim 1, The following steps are involved: S1, using a vacuum device to evacuate the sealed space in the calorimeter; S2, using a replacement device to replace the air in the upper protection chamber (32), the test chamber (33), and the lower protection chamber (34) with hydrogen; S3, injecting liquid hydrogen into the upper protection cavity (32), the lower protection cavity (34), and the test cavity (33) using a liquid hydrogen injection device; controlling the thermal boundary temperature using a thermal boundary temperature controller (28) or a water cooling coil (35); S4, measuring the flow rate of volatilized hydrogen in the test chamber (33), measuring the temperature of the outer wall of the insulation material or the inner wall of the thermal boundary temperature controller (18), and measuring the temperature of the outer wall of the test chamber (33); and calculating the apparent thermal conductivity of the liquid hydrogen storage tank insulation material based on the measured flow rate and temperature.

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