Liquid Hydrogen Valve Evaluation Apparatus and Valve Evaluation Method Using the Same

Abstract

The present invention relates to a technology for verifying the performance of cryogenic valves used in liquid hydrogen storage and transfer systems. More specifically, it relates to a liquid hydrogen valve evaluation device and a valve evaluation method using the same, which can safely and economically evaluate valve airtightness and operability in a liquid hydrogen environment by integrating a helium-based pre-cooling and hydrogen re-liquefaction system with precision sensors and safety logic. The invention provides an integrated system that maximizes the reliability and safety of airtightness and operability evaluation by organically combining a valve test specimen, a high-vacuum insulation chamber, a helium cooling loop, a liquid hydrogen supply system, and a control unit linked with vacuum and hydrogen detection sensors to evaluate the valve under cryogenic conditions identical to the actual operating environment, and by including a flow meter and a helium leak detector for measuring internal / external leakage, and a torque sensor for measuring the driving force during valve operation.

Description

Technology Field

[0001] The present invention relates to a technology for verifying the performance of cryogenic valves used in liquid hydrogen storage and transfer systems, and more specifically, to a liquid hydrogen valve evaluation device and a valve evaluation method using the same, which can safely and economically evaluate valve airtightness and operability in a liquid hydrogen environment by integrating a helium-based pre-cooling and hydrogen re-liquefaction system, precision sensors, and safety logic. Background Technology

[0002] Recently, as hydrogen has garnered attention as a key energy source for achieving carbon neutrality, the importance of liquid hydrogen technology for the efficient storage and transportation of hydrogen is emerging. Liquidizing gaseous hydrogen by cooling it to an ultra-low temperature of minus 253 degrees (20K) can reduce its volume to about 1 / 800th, making it advantageous for large-scale storage and long-distance transportation. However, to establish such a liquid hydrogen supply chain, ensuring the reliability of valves capable of stably controlling and shutting off fluid flow even in ultra-low temperature environments is a prerequisite.

[0003] Valves for liquid hydrogen are exposed to environments incomparably harsher than those for general cryogenic valves (e.g., for LNG, 111K). A temperature of 20K degrades the toughness of metal materials, hardens sealing materials to reduce airtightness, and causes dimensional deformation due to thermal shrinkage. Therefore, it is essential to verify performance under conditions identical to the actual operating environment during the valve development phase.

[0004] Conventional valve evaluation technology has primarily relied on using liquid nitrogen (77K) as a substitute refrigerant. Although liquid nitrogen is easy to handle and inexpensive, it has limitations in accurately simulating the shrinkage of the valve seat or changes in material properties due to the temperature difference (about 57K) compared to liquid hydrogen. This causes valves that pass the liquid nitrogen test to leak in an actual liquid hydrogen environment.

[0005] Furthermore, safety and economic feasibility issues are serious when conducting tests using actual liquid hydrogen. Hydrogen has a low lower explosive limit and a rapid diffusion rate, posing a high risk of major accidents in the event of a leak. Conventional test facilities lack active safety systems capable of detecting leaks and automatically shutting them off or replacing them with inert gases, posing a risk of requiring reliance on manual operation by workers in the event of an accident. In addition, simply venting out the Boolean Oxide (BOG) generated during testing can lead to fires and explosions due to the inherent properties of hydrogen; this not only wastes expensive hydrogen resources but also causes environmental problems.

[0006] Furthermore, another challenge that must be addressed is the issue of cross-contamination, where helium used in the pre-cooling process essential for cryogenic testing mixes with hydrogen, the test fluid, within the piping. This is because mixing of the two fluids can reduce hydrogen purity, thereby impairing re-liquefaction efficiency, or cause hydrogen to backflow into the helium line, leading to blockages caused by freezing.

[0007] Therefore, there is an urgent need to develop an integrated valve evaluation device and method that implements a real liquefied hydrogen environment of 20K, while also featuring precise sensor-based safety logic, cross-contamination prevention piping, a system for recovering and re-liquefying vaporized hydrogen, means to specifically measure the airtightness and operability of the valve, and a final vent piping network design for safe combustion treatment. Prior art literature

[0008] Republic of Korea Registered Patent Publication No. 10-2775001 The problem to be solved

[0009] The present invention has been devised to improve upon the aforementioned problems. The purpose of the present invention is to provide an integrated system that maximizes the reliability and safety of airtightness and operability evaluation by organically combining a valve test specimen, a high-vacuum insulation chamber, a helium cooling loop, a liquid hydrogen supply system, and a control unit linked with vacuum and hydrogen detection sensors to evaluate the valve under cryogenic conditions identical to the actual operating environment, and by including a flow meter and a helium leak detector for measuring internal / external leakage, and a torque sensor for measuring the driving force during valve operation.

[0010] In addition, the present invention aims to provide a piping structure that fundamentally prevents mixing of different fluids and backflow accidents by configuring a double block and discharge (DBB) unit in each of the helium supply unit and the liquid hydrogen supply unit, and controlling the discharge of leaked fluid through a bleed valve.

[0011] In addition, the present invention aims to provide a device for recovering vaporized hydrogen generated during testing by re-liquefying it using a condenser comprising a gas-liquid separator and a plate heat exchanger.

[0012] In addition, the present invention aims to provide an emergency operation logic that completely eliminates the risk of explosion by designing a final vent piping network that forcibly purges the inside of the system upon detection of abnormal signs and performs safe combustion treatment (Flare stack) or discharge into a safe zone after dilution with inert gas, rather than simple external discharge when overpressure occurs.

[0013] In addition, the present invention aims to provide a standardized liquid hydrogen valve evaluation method extending from vacuum formation to the recovery of vaporized hydrogen.

[0014] In addition, the present invention aims to provide a method for feedback-controlling the helium flow rate so that the cooling rate is maintained within the allowable thermal stress limit, based on a user interface (UI) that has a built-in database of thermal shrinkage rates and thermal stress characteristics for various valve materials or allows the user to input this information during the pre-cooling stage.

[0015] In addition, the present invention aims to provide a valve opening and closing sequence that prevents cross-contamination by removing residual helium pressure immediately before supplying liquid hydrogen.

[0016] In addition, the present invention aims to provide an intelligent recovery method that controls the branching of the flow path to a re-liquefaction section or a bypass line depending on whether the temperature of the discharged fluid is above or below the vaporization point during the recovery stage.

[0017] In addition, the present invention aims to provide an emergency stop step that cuts off the hydrogen supply and injects an inert gas to eliminate hazardous elements when an abnormality is detected during testing.

[0018] Finally, the present invention aims to provide a pretreatment method that prevents valve malfunction caused by freezing by introducing a cycle purging method that repeats vacuum suction and pressurized helium washing during the preparation stage, thereby completely removing fine moisture and impurities adsorbed inside the valve and piping. means of solving the problem

[0019] To solve the aforementioned problem, the present invention is a liquefied hydrogen valve evaluation device comprising: a high-vacuum insulation chamber in which a valve test specimen to be evaluated is mounted; a vacuum sensor and a hydrogen detection sensor for detecting internal pressure; a flow meter and a helium leak detector at the downstream end of the valve for measuring internal / external leakage of the valve; a torque sensor for measuring torque required when operating the valve; a cooling system including a helium refrigerant compressor and a liquefier; a hydrogen supply system including a liquefied hydrogen dewar and a PBC; an inert gas supply line; a final vent piping network for performing safe combustion treatment (flare stack) or discharge after inert gas dilution when overpressure is discharged through a rupture disc or relief valve; and a control unit for controlling the entire system based on sensor data.

[0020] To solve the above-mentioned problem, the present invention comprises a DBB unit in which a helium supply unit and a liquid hydrogen supply unit each consist of a first and second shut-off valve and a bleed valve between them, and a control unit is configured to prevent cross-contamination by opening the valve according to the test mode to discharge the leaked fluid.

[0021] To solve the aforementioned problem, the present invention comprises a re-liquefaction unit including a gas-liquid separator, a condenser including a plate heat exchanger that exchanges heat with a helium refrigerant, and a cryogenic liquid pump that pumps the re-liquefied hydrogen to a Dewar.

[0022] To solve the aforementioned problem, the present invention is configured to perform an emergency operation logic in which, when the control unit receives an abnormal signal from a vacuum sensor or a hydrogen detection sensor, it closes the emergency shut-off valve of the liquid hydrogen supply unit and opens the inert gas supply line to forcibly purge the inside of the system, and safely processes the discharged gas through the final vent piping network.

[0023] To solve the aforementioned problem, the present invention is a method for evaluating a liquid hydrogen valve comprising a preparation step for vacuum formation and purging, a pre-cooling step using helium, a temperature synchronization step for controlling to an approach temperature, a test step for evaluating the valve by injecting liquid hydrogen, and a step for recovering BOG by re-liquefying it.

[0024] To solve the aforementioned problem, the present invention is configured to monitor the rate of temperature change of the valve test specimen surface in real time during the pre-cooling stage, and to feedback control the helium supply flow rate so that the cooling rate is maintained within the allowable thermal stress limit of the valve material based on data input through a database of thermal shrinkage rates and thermal stress characteristics for various valve materials embedded in the control unit or through a user interface (UI).

[0025] To solve the above-mentioned problem, the present invention is configured to perform a cross-contamination prevention sequence in which, immediately before the liquid hydrogen supply step, the bleed valve of the helium supply unit is opened to remove residual helium pressure and then closed, followed by the opening of the hydrogen supply valve.

[0026] To solve the aforementioned problem, the present invention is configured to control the flow path by branching it so that if the temperature of the discharged fluid in the recovery step is above the vaporization point, it is sent to a re-liquefaction unit, and if it is in a liquid state below the vaporization point, it is recovered by Dewar or sent to a separate recovery tank through a bypass line equipped with a recovery pump.

[0027] To solve the aforementioned problem, the present invention is configured to include an emergency stop step that cuts off the hydrogen supply upon detection of abnormal signs during testing, monitors whether the safety valve is operating, and injects an inert gas to eliminate the risk factor.

[0028] To solve the aforementioned problem, the present invention is configured to remove residual moisture and oxygen inside the system by performing cycle purging in the preparation stage, which alternately repeats a vacuum suction process and a helium pressurization washing process a set number of times. Effects of the invention

[0029] According to one embodiment of the present invention, by integrating a high-vacuum insulation chamber, a precision sensor, and a helium cooling and hydrogen re-liquefaction system, an environment of 20K, which is the actual liquid hydrogen temperature, is precisely realized, and by obtaining clear physical indicators of airtightness and operability through a flow meter, a helium leak detector, and a torque sensor, the reliability of valve performance evaluation is dramatically improved.

[0030] In addition, according to one embodiment of the present invention, by applying a double blocking and discharge (DBB) structure to perfectly isolate helium and hydrogen lines and discharge leaked fluid, there is an effect of preventing data errors or pipe blockage accidents caused by fluid mixing.

[0031] In addition, according to one embodiment of the present invention, there is an economic effect of preventing the waste of expensive hydrogen resources and reducing test operation costs through a high-efficiency re-liquefaction system that captures all of the vaporized hydrogen and returns it to a liquid state.

[0032] In addition, according to one embodiment of the present invention, through automated emergency operation logic based on vacuum sensor and hydrogen detection sensor data and a final vent piping network design that ensures safe combustion treatment (Flare stack) or discharge into a safe zone after inert gas dilution, there is an effect of fundamentally preventing large explosion accidents in the event of hydrogen leakage or overpressure situations.

[0033] In addition, according to one embodiment of the present invention, by providing a standardized test procedure from preparation to recovery, consistency of test results is ensured, and the same level of safety is guaranteed even in repeated tests.

[0034] In addition, according to one embodiment of the present invention, by utilizing a thermal shrinkage rate database by material and a user interface (UI) embedded in the control unit to perform optimal cooling rate control considering the thermal stress of the valve, damage to the test specimen caused by rapid temperature changes is prevented, and the lifespan of the valve, which is an expensive prototype, is extended.

[0035] In addition, according to one embodiment of the present invention, through a strict sequence for removing residual gas during oil type conversion, evaluation in a pure liquid hydrogen environment is ensured, and the effect of minimizing test errors caused by the incorporation of impurities is achieved.

[0036] In addition, according to one embodiment of the present invention, there is an effect of optimizing energy efficiency and ensuring physically stable recovery through intelligent control that selects re-liquefaction or bypass recovery using a pump depending on the state of the discharged fluid.

[0037] In addition, according to one embodiment of the present invention, a systematic emergency stop manual is logicized, so that in the event of an actual accident, the system automatically eliminates risk factors to protect the life of the worker.

[0038] Finally, according to one embodiment of the present invention, by removing even minute moisture invisible to the naked eye through powerful cycle purging using pressure fluctuations, there is an effect of preventing valve sticking or misdiagnosis of internal leakage in cryogenic environments. Brief explanation of the drawing

[0039] FIG. 1 is a schematic diagram showing the overall configuration of a liquid hydrogen valve evaluation device according to one embodiment of the present invention. FIG. 2 is a drawing showing a unit for preventing cross-contamination according to an embodiment of the present invention. FIG. 3 is a diagram showing a detailed configuration for recovering vaporized hydrogen according to one embodiment of the present invention. FIG. 4 is a diagram illustrating the emergency operation logic and final vent piping network of a valve evaluation device according to one embodiment of the present invention. FIG. 5 is a flowchart showing the overall flow of a liquid hydrogen valve evaluation method according to one embodiment of the present invention. FIG. 6 is a flowchart illustrating a database-based pre-cooling control process considering thermal stress of a valve test specimen according to one embodiment of the present invention. FIG. 7 is a diagram showing the valve opening and closing sequence when switching from helium cooling to hydrogen supply according to one embodiment of the present invention. Specific details for implementing the invention

[0040] The present invention relates to a system and method for evaluating the performance and safety of a liquefied hydrogen valve. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In assigning reference numerals to the components of each drawing, the same components are given the same reference numeral whenever possible, even if they are shown in different drawings. Furthermore, in describing the present invention, if it is determined that a detailed description of related known components or functions may obscure the essence of the present invention, such detailed description is omitted.

[0042] As illustrated in FIGS. 1 to 4, a liquid hydrogen valve evaluation device according to one embodiment of the present invention is composed of an integrated system for verifying the reliability of a valve in a cryogenic environment. The liquid hydrogen valve evaluation device is broadly composed of a chamber section for creating a test environment, a helium line for cooling, a hydrogen supply line as the actual fluid, and a system for controlling and recovering the same.

[0043] Specifically, the test chamber (100) provides a sealed containment space in which the valve test specimen (10) to be evaluated can be mounted. The test chamber (100) has a vacuum jacket form with a high-vacuum insulation structure, such as a multilayer insulation (MLI), to block heat intrusion from the outside during cryogenic testing. This insulation structure minimizes the vaporization of hydrogen due to heat transfer when the valve test specimen (10) is exposed to an environment of about 20 K, which is the temperature of liquid hydrogen, and enables accurate performance evaluation.

[0044] The vacuum port (110) is connected to the test chamber (100). The vacuum port (110) is connected to a vacuum pump that exhausts internal air to the outside to form a high vacuum state, and also includes a vacuum sensor (not shown) that measures the vacuum level inside the chamber in real time. Additionally, it includes a rupture disc or relief valve to discharge overpressure when the internal pressure exceeds a preset threshold in an emergency situation. At this time, since hydrogen has a low lower explosion limit and poses a high risk of leading to a major accident if leaked, a final vent piping network is applied to ensure that, in the event of overpressure, the hydrogen is discharged only to a safe zone after safe combustion treatment (flare stack) or inert gas dilution, rather than simply being discharged to the outside. This serves as a core safety device to completely eliminate the risk of explosion. Furthermore, a hydrogen detection sensor (not shown) is provided inside or adjacent to the test chamber (100) to detect whether there is a hydrogen leak. In addition, to obtain specific indicators for evaluating the airtightness and operability of the valve, a flow meter at the downstream end of the valve for measuring internal leakage and a helium leak detector for measuring external leakage are installed around the valve test specimen (10), and physical components such as a torque sensor for measuring the driving force and torque required when operating the valve are explicitly included.

[0046] A helium circulation loop is configured for pre-cooling the valve test specimen (10). The helium refrigerant compressor (200) compresses gaseous helium to a high pressure to form a flow, and the compressed helium passes through the helium refrigerant liquefier (210) and undergoes a phase change to a cryogenic state or is supercooled. The low-temperature helium thus generated is distributed to the system through the helium supply unit (220).

[0047] The helium supply unit (220) is connected to the helium refrigerant liquefier (210) and includes a gas supply line for purging the inside of the valve test body (10) and a flow path switching valve assembly for selectively opening and closing a flow path for cooling. This serves to switch the use of the helium for cleaning or cooling depending on the test stage. Additionally, an inert gas supply line (not shown) is connected to the test chamber (100) and related piping to supply inert gas in case of emergency or during purging.

[0048] The helium cooling system (230) is provided inside the test chamber (100). The helium cooling system (230) has a cooling jacket or cooling coil structure positioned to be in close contact with the outer surface of the valve test body (10). As cryogenic helium supplied from the helium supply unit (220) passes through the helium cooling system (230), it indirectly cools the valve test body (10) through conduction or convection heat transfer. This serves to prevent thermal shock by cooling the valve to near the target temperature before directly injecting liquid hydrogen. The helium, after cooling, is recovered through the cryogenic helium recirculation unit (240) and recirculated back to the helium refrigerant compressor (200), thereby maximizing energy efficiency.

[0049] Meanwhile, the liquid hydrogen deurer (300) is provided to supply hydrogen, which is the actual test fluid. The liquid hydrogen deurer (300) is a vacuum-insulated container that stores a large volume of liquid hydrogen. The PBC (310) is installed to control the internal pressure of the liquid hydrogen deurer (300). The PBC (Pressure Building Circuit) (310) uses a method of drawing out a portion of the liquid hydrogen from the bottom of the deurer, converting it into gas through a vaporizer, and then reinjecting it into the gas layer (Ullage space) at the top of the deurer. Specifically, the PBC (310) opens a pressure control valve when the pressure data inside the deurer collected by the control unit (500) is less than a set value, and forcibly vaporizes the liquid hydrogen drawn out from the bottom through heat exchange with the atmosphere or a separate heat source, utilizing the rapid volume expansion of the hydrogen that occurs during this process. When vaporized high-pressure hydrogen gas is reinjected into the gas layer at the top of the Dewar, the mass of the gas layer increases and molecular motion becomes more active, causing the saturated vapor pressure inside the Dewar to rise. During this pressure increase process, the pressure regulating valve operates to actively raise the internal pressure of the Dewar to the target pressure set by the user, and the resulting differential pressure serves as the driving force for transporting liquid hydrogen.

[0050] Using the pressure formed by the above PBC (310), the liquid hydrogen supply unit (320) precisely supplies liquid hydrogen within the liquid hydrogen deurer (300) to the valve test body (10). At this time, the control unit (500) manages the entire system. The control unit (500) collects data received from the vacuum sensor and hydrogen detection sensor, as well as temperature and pressure data for each line, and based on this, controls the opening and closing of the helium supply unit (220) and the liquid hydrogen supply unit (320), and the operation of the inert gas supply line to ensure that a safe and efficient test is performed.

[0051] Finally, the hydrogen discharged during the test process is transferred to the re-liquefaction unit (400). The re-liquefaction unit (400) collects the vaporized hydrogen (BOG) discharged from the downstream end of the valve test body (10) and re-liquefies it back into a liquid state through a condenser containing a built-in cryogenic refrigerator or heat exchanger. The re-liquefied hydrogen is recovered to the liquid hydrogen deurer (300) to conserve resources and ensure economic efficiency.

[0052] Through such a configuration, the present invention has the effect of precisely evaluating the airtightness, operability, and durability of the valve under cryogenic conditions similar to actual operating environments, while minimizing the consumption of expensive liquid hydrogen.

[0054] In the present invention, the piping configuration for preventing fluid mixing accidents and ensuring safety adopts a Double Block and Bleed (DBB) method. The helium supply unit (220) and the liquid hydrogen supply unit (320) each have a first shut-off valve and a second shut-off valve arranged in series on the main supply path leading to the valve test specimen (10). A bleed valve connected to an external vent line is branched and connected in the path section between these two shut-off valves.

[0056] This DBB unit configuration is designed to physically and completely block cross-contamination caused by the mixing of helium and hydrogen, which have different physical properties. This is because mixing of helium and hydrogen can reduce the re-liquefaction efficiency of hydrogen or lead to the formation of hydrogen ice in the helium refrigeration cycle, causing blockages.

[0058] The control unit (500) precisely controls this DBB unit according to the test mode. Specifically, when a pre-cooling mode using helium is performed, the control unit (500) opens the shut-off valves of the helium supply unit (220) to supply helium. At the same time, the first and second shut-off valves on the side of the liquid hydrogen supply unit (320) both remain closed. However, since the possibility of minute internal leakage of the valve cannot be ruled out, the control unit (500) forcibly opens the bleed valve of the liquid hydrogen supply unit (320). Accordingly, any liquid hydrogen or gaseous hydrogen that leaks through the first shut-off valve cannot flow toward the valve test body and is discharged to an external safety zone through the bleed valve. In other words, the inflow of hydrogen into the helium line is completely blocked.

[0059] Conversely, in the liquid hydrogen supply mode, the control unit (500) opens the shut-off valves of the liquid hydrogen supply unit (320) and closes the bleed valve to supply hydrogen. At the same time, the first and second shut-off valves on the helium supply unit (220) side are closed, and the bleed valve located between them is opened. This prevents high-pressure helium from flowing back into the hydrogen line, thereby preventing a decrease in the purity of the hydrogen or causing pressure disturbances.

[0061] The above re-liquefaction unit (400) is a system that efficiently recovers the boiler-off gas (BOG) that inevitably occurs during the testing process and converts it back into a liquid state. At the forefront of the above re-liquefaction unit (400), a gas-liquid separator (410) installed in the discharge line at the rear end of the valve test body (10) is located. The fluid discharged from the test body may be in a two-phase flow state in which liquid and gas are mixed. The gas-liquid separator (410) physically separates the high-density liquid component and the low-density gas component using gravity or centrifugal force.

[0063] The gaseous hydrogen separated in the above-mentioned gas-liquid separator (410) flows into a plate heat exchanger (420). This plate heat exchanger (420) is a device that maximizes heat transfer efficiency by providing a large heat transfer surface area. Here, the gaseous hydrogen performs heat exchange with cryogenic helium refrigerant supplied from a separate refrigeration cycle. The helium refrigerant, having a temperature of 20 K or less, absorbs heat from the gaseous hydrogen, and the hydrogen, having lost heat, undergoes a phase change (condensation) from a gaseous state to a liquid state. Furthermore, the above-mentioned plate heat exchanger (420) goes beyond simple liquefaction to make the generated liquid hydrogen into a sub-cooling state, thereby suppressing re-gasification during transport.

[0065] The hydrogen thus re-liquefied must be sent back into the liquid hydrogen deurer (300). However, since a constant pressure is maintained inside the deurer, recovery may be difficult through natural flow alone. To this end, the re-liquefaction unit (400) includes a cryogenic liquid pump. The cryogenic liquid pump pressurizes the re-liquefied hydrogen and forcibly pumps it into the liquid hydrogen deurer (300).

[0067] The safety management system of the present invention is implemented with multi-detection and emergency response logic centered on the control unit (500). The control unit (500) receives vacuum level data inside the test chamber (100) in real time from a vacuum sensor equipped in the vacuum port (110). A high vacuum state is not only an essential condition for maintaining thermal insulation performance, but also serves as an indirect indicator for determining whether hydrogen has leaked from a valve or piping.

[0068] Additionally, the control unit (500) is also linked to a hydrogen detection sensor installed in the test chamber (100). When a leak signal is received from the hydrogen detection sensor, this is considered an immediate danger situation. If either a decrease in vacuum level or a hydrogen leak signal is detected, the control unit (500) immediately activates an Emergency Shutdown Sequence. As a first measure, the control unit (500) immediately closes the Emergency Shut-Down Valve (ESD Valve) of the liquid hydrogen supply unit (320).

[0069] Simultaneously with the source blockage, the control unit (500) opens an inert gas supply line to remove residual hydrogen inside the test chamber (100) and in the associated piping. This allows high-pressure inert gas (nitrogen or helium) to be blown into the system to rapidly dilute the combustible hydrogen and push it out through an external vent line.

[0071] As illustrated in FIG. 5, the liquid hydrogen valve evaluation method according to the present invention is divided into five stages: preparation, pre-cooling, temperature synchronization, main test, and recovery, and each stage is organically controlled by the control unit (500).

[0072] First, a preparation step (S100) is performed. In this step, the control unit (500) operates a vacuum pump connected to the vacuum port (110) to exhaust the air inside the test chamber (100), thereby forming a high vacuum insulation state. At the same time, the helium supply unit (220) is controlled to perform a purging operation in which room temperature helium gas is injected into and discharged into the internal flow path of the valve test body (10).

[0073] Next, a pre-cooling step (S200) of the valve test specimen (10) follows. The control unit (500) switches the flow path switching valve assembly of the helium supply unit (220) to a cooling mode and circulates cryogenic helium to the jacket or coil of the helium cooling system (230). Afterward, a temperature synchronization step (S250) is performed. The control unit (500) precisely controls the helium flow rate so that the temperature of the valve test specimen (10) reaches an approach temperature set to a range of about 1 K to 10 K higher than the saturation temperature of liquid hydrogen.

[0074] Once the temperature stabilizes, the actual test phase (S300) proceeds. The control unit (500) blocks the helium supply unit (220) and increases the pressure inside the dewar using the PBC (310). Liquid hydrogen is supplied into the valve test body (10) through the liquid hydrogen supply unit (320) by the formed differential pressure.

[0075] Finally, a recovery step (S400) for processing the gas generated during the test is performed. During the test step (S300), the gaseous hydrogen (BOG) that naturally vaporizes or is generated during the valve cooling process is converted into a liquid state through the condenser of the re-liquefaction unit (400) and recovered to the liquid hydrogen dewar (300).

[0077] As illustrated in FIG. 6, the pre-cooling step (b) (S200) follows a sophisticated temperature control profile to prevent thermal damage to the valve test specimen (10). The control unit (500) lowers the temperature of the helium supplied to the helium cooling system (230) according to a preset temperature profile. At this time, the rate of change of the surface temperature (delta T / dt) of the valve test specimen (10) is monitored in real time, and the helium flow rate is feedback-controlled so that the cooling rate does not exceed the allowable thermal stress limit of the valve material. To implement this in an actual device, the control unit (500) has a built-in database of thermal shrinkage rates and thermal stress characteristics for various valve materials (e.g., SUS 316L, etc.), and a user interface (UI) is provided so that the user can easily select or input this.

[0079] As illustrated in FIG. 7, the present invention performs a cross-contamination blocking sequence at the transition point from a pre-cooling step (S200) using helium to a test step (S300) using hydrogen. The control unit (500) first stops the helium supply by closing the main shut-off valve on the helium supply unit (220) side. Then, the bleed valve provided on the helium supply unit (220) side is opened to discharge residual helium in the piping. When the pressure drops to the level of atmospheric pressure, the bleed valve is closed, and only then is the shut-off valve of the liquid hydrogen supply unit (320) opened to introduce pure liquid hydrogen.

[0081] The recovery step (e) (S400) above actively determines the recovery path according to the phase state of the discharged fluid. The control unit (500) operates the flow path control valve to guide the discharged fluid to the re-liquefaction unit (400) when the temperature of the discharged fluid is above the vaporization point of hydrogen. On the other hand, when the temperature of the discharged fluid is below the vaporization point and it is in a liquid state, it controls the opening of a bypass line equipped with a separate recovery pump to forcibly recover the fluid to the liquid hydrogen dewar (300) or to send it to a separate liquid hydrogen recovery tank. This is intended to overcome the physical limitations that make natural backflow to the pressurized dewar impossible and to reduce the re-liquefaction load.

[0082] If a danger signal is detected during the test, the control unit (500) performs an emergency stop step. When the vacuum sensor or hydrogen detection sensor reacts, the emergency shut-off valve (ESD) of the liquid hydrogen supply unit (320) is immediately closed, and the inert gas supply line is opened to purge the inside of the system with nitrogen or helium.

[0083] In addition, the purging performed in the preparation step (S100) of the present invention applies a cycle purging method that repeats vacuum suction and pressurized helium washing. The control unit (500) completely removes residual moisture and oxygen by alternately performing the process of desorbing impurities through suction via a vacuum pump and diluting them through helium pressurization. Explanation of the symbols

[0084] 10: Valve test specimen 100: Test chamber 110: Vacuum pot 200: Helium refrigerant compressor 210: Helium refrigerant liquefier 220: Helium supply unit 230: Helium cooling system 240: Cryogenic Helium Recirculation Unit 300: Liquid Hydrogen Dewar 310: PBC (Pressure Building Circuit) 320: Liquid hydrogen supply unit 400: Re-liquefaction unit 410: Gas-liquid separator 420: Plate heat exchanger 500: Control unit

Claims

Claim 1 A test chamber (100) having a sealed receiving space in which a valve test specimen (10) to be evaluated can be mounted, and having a high-vacuum insulation structure that blocks external heat intrusion; a vacuum port (110) connected to the test chamber (100) to form a vacuum by exhausting internal air, and including a vacuum sensor that measures internal pressure and a rupture disc or relief valve that discharges overpressure when the internal pressure exceeds a preset threshold; a hydrogen detection sensor installed inside or adjacent to the test chamber (100) to detect hydrogen leakage; a physical measurement means provided for evaluating airtightness and operability indicators, including a flow meter at the downstream end of the valve to measure internal leakage of the valve, a helium leak detector to measure external leakage, and a torque sensor to measure the driving force required when operating the valve; an inert gas supply line connected to supply inert gas into the test chamber (100) and the piping; and a structure designed to discharge hydrogen discharged through the rupture disc or relief valve into a safe zone after safe combustion treatment (flare stack) or inert gas dilution. Final vent piping network; a helium refrigerant compressor (200) that compresses gaseous helium to form a high-pressure flow; a helium refrigerant liquefier (210) that changes the phase of helium supplied from the helium refrigerant compressor (200) into a cryogenic fluid; a helium supply unit (220) connected to the helium refrigerant liquefier (210) and including a line that supplies purging gas into the valve test body (10) and a flow path switching valve assembly that selectively opens and closes a cooling flow path; a helium cooling system (230) having a cooling jacket or cooling coil structure that is positioned to be in close contact with the outer surface of the valve test body (10) inside the test chamber (100) and performs conduction or convection heat transfer, and cools the valve test body (10) by passing cryogenic helium supplied from the helium supply unit (220) through it.A cryogenic helium recirculation unit (240) that recovers helium that has passed through the helium cooling system (230) and recirculates it to the helium refrigerant compressor (200); a liquid hydrogen deurer (300) that stores liquid hydrogen; a pressure regulating valve that opens and closes according to feedback control based on internal pressure data of the liquid hydrogen deurer collected by a control unit (500), and when the pressure regulating valve is opened, liquid hydrogen at the bottom of the liquid hydrogen deurer (300) is drawn out and forcibly vaporized in a vaporizer, and the vaporized high-pressure hydrogen gas is re-injected into the upper gas layer using the volume expansion of the hydrogen generated, thereby increasing the saturated vapor pressure according to the increase in the amount of substance, thereby actively increasing the internal pressure of the liquid hydrogen deurer (300); and a liquid hydrogen that supplies liquid hydrogen within the liquid hydrogen deurer (300) to the valve test body (10) using the pressure difference formed by the PBC (310). A liquid hydrogen valve evaluation device comprising: a supply unit (320); a re-liquefaction unit (400) that collects the gaseous hydrogen (BOG) discharged from the downstream end of the valve test body (10) and re-liquefies the gaseous hydrogen through a condenser including a cryogenic refrigerator or a heat exchanger to recover it to the liquid hydrogen deurer (300); and a control unit (500) that controls the opening and closing of the flow path switching valve assembly of the helium supply unit (220), the liquid hydrogen supply unit (320), and the inert gas supply line based on data received from the vacuum sensor and the hydrogen detection sensor. Claim 2 A liquid hydrogen valve evaluation device according to claim 1, wherein the helium supply unit (220) and the liquid hydrogen supply unit (320) each comprise a Double Block and Bleed (DBB) unit consisting of a first and second shut-off valve arranged in series on a supply path leading to the valve test body (10), and a bleed valve connecting the path between the first and second shut-off valves to an external vent line, and wherein the control unit (500) controls the opening of the bleed valve of the liquid hydrogen supply unit (320) in helium cooling mode to discharge leaked hydrogen, thereby preventing hydrogen from flowing into the helium line, and opening the bleed valve of the helium supply unit (220) in liquid hydrogen supply mode to prevent backflow of hydrogen into the helium line. Claim 3 A liquid hydrogen valve evaluation device according to claim 1, wherein the re-liquefaction unit (400) comprises: a gas-liquid separator (410) installed in the discharge line at the rear end of the valve test body (10); the condenser including a plate heat exchanger (420) that converts gaseous hydrogen separated from the gas-liquid separator (410) into a supercooled liquid through heat exchange with a helium refrigerant; and a cryogenic liquid pump that pumps the re-liquefied hydrogen into the liquid hydrogen dewar (300). Claim 4 A liquid hydrogen valve evaluation device according to claim 1, wherein the control unit (500) performs an emergency operation logic in which, when the vacuum level measured by the vacuum sensor drops below a preset safety threshold or a leakage signal is received from the hydrogen detection sensor, the control unit (500) immediately closes the emergency shut-off valve (ESD Valve) of the liquid hydrogen supply unit (320) and opens the inert gas supply line to forcibly purge residual hydrogen inside the test chamber (100) and piping, while controlling the discharged gas to undergo safe combustion treatment (Flare stack) or inert gas dilution treatment through the final vent piping network. Claim 5 A valve evaluation method using the liquid hydrogen valve evaluation device of claim 1, comprising: (a) a preparation step (S100) in which a control unit (500) operates a vacuum pump connected to a vacuum port (110) to form a vacuum insulation state inside a test chamber (100) and controls a helium supply unit (220) to purge the inside of a valve test body (10); (b) a step (S200) of pre-cooling the valve test body (10) by switching the flow path switching valve assembly of the helium supply unit (220) to a cooling mode and driving a helium refrigerant compressor (200) and a helium refrigerant liquefier (210) to circulate cryogenic helium to a jacket or coil of a helium cooling system (230); (c) controlling the helium flow rate so that the temperature of the valve test body (10) reaches an approach temperature set in a range of 1 K to 10 K higher than the saturation temperature of liquid hydrogen, thereby performing a subsequent A method for evaluating a liquid hydrogen valve comprising: a temperature synchronization step (S250) to prevent rapid phase change and thermal shock when liquid hydrogen is injected; (d) a test step (S300) to evaluate the performance of the valve by supplying liquid hydrogen into the valve test specimen (10) through the liquid hydrogen supply unit (320) by blocking the helium supply unit (220) and pressurizing the inside of the deurer using the PBC (310); and (e) a step (S400) to convert the gaseous hydrogen (BOG) generated during the test step (S300) into a liquid state through the condenser of the re-liquefaction unit (400) and recover it to the liquid hydrogen deurer (300). Claim 6 A method for evaluating a liquid hydrogen valve according to claim 5, wherein step (b) (S200) lowers the temperature of the helium supplied to the helium cooling system (230) according to a preset temperature profile, while monitoring the rate of change (delta T / dt) of the temperature sensor attached to the surface of the valve test specimen (10) in real time to feedback control the flow rate of the helium supply unit (220) so that the cooling rate is maintained within the allowable thermal stress limit of the valve material, and sets the allowable thermal stress limit based on input values ​​through a database of thermal shrinkage rates and thermal stress characteristics for various valve materials embedded in the control unit (500) or a user interface (UI). Claim 7 A method for evaluating a liquid hydrogen valve according to claim 5, wherein, prior to performing step (d) (S300), the helium supply unit (220) includes a bleed valve, and the bleed valve on the side of the helium supply unit (220) is opened to remove residual helium pressure in the piping to an atmospheric pressure level and then closed again, and subsequently, the shut-off valve of the liquid hydrogen supply unit (320) is opened to perform a cross-contamination blocking sequence to prevent mixing of helium and hydrogen. Claim 8 A method for evaluating a liquid hydrogen valve according to claim 5, wherein step (e) (S400) is characterized by controlling the flow path to guide the fluid to a re-liquefaction section (400) when the temperature of the fluid discharged from the downstream end of the valve test body (10) is above a preset vaporization point, and to recover the fluid to the liquid hydrogen dewar (300) or to a separate liquid hydrogen recovery tank through a bypass line equipped with a recovery pump when the fluid is in a liquid state below the vaporization point.

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