A cryogenic liquid storage device

Abstract

This invention relates to the field of cryogenic engineering and cryogenic storage technology, and provides a cryogenic liquid storage device. The device includes an outer tank, a first insulation layer, a pump-assisted evaporation cooling screen, a second insulation layer, and an inner tank. An air extraction component and a liquid replenishment component are installed on the pump-assisted evaporation cooling screen. The pump-assisted evaporation cooling screen internally comprises a dispersed evaporation section and a porous liquid absorption core structure. The dispersed evaporation section consists of multi-stage liquid storage pools distributed along the height, dispersing the evaporation process into multiple evaporation surfaces along the height direction. The invention also includes a control module composed of a pressure sensor, a liquid level sensor, and a controller, which can automatically execute the air extraction and liquid replenishment processes. This invention, by introducing a pump-assisted evaporation cooling screen, suppresses the evaporation loss of the cryogenic liquid in the inner tank, and is suitable for long-term, high-reliability storage of cryogenic liquids such as liquid hydrogen and liquid helium.

Description

Technical Field

[0001] This invention relates to the field of cryogenic storage technology, and more particularly to a cryogenic liquid storage device. Background Technology

[0002] Cryogenic liquefied gases typically refer to substances with a critical temperature below -50°C. These working fluids are difficult to maintain stably in liquid form under normal temperature and pressure conditions and require a cryogenic environment to maintain their gas-liquid equilibrium. Currently, the cryogenic liquefied gases widely used in industrial applications mainly include liquid hydrogen, liquid helium, and liquid neon. Due to their extremely low critical temperatures, high purification and preparation costs, and significant application value, liquid helium, liquid hydrogen, and liquid neon are widely used in aerospace, quantum devices, hydrogen transportation, and energy storage. Therefore, the cryogenic storage and transportation of high-value liquefied gases such as liquid helium and liquid hydrogen are of great importance.

[0003] The main challenge in storing and transporting cryogenic liquefied gases lies in their high sensitivity to environmental heat load. Despite insulation measures, external heat inevitably transfers into the storage tank through conduction, radiation, and residual gas convection. Since cryogenic liquefied gases are typically near-saturation, the heat entering the system is difficult to buffer through sensible heat, often triggering liquid evaporation through latent heat of phase change. This leads to changes in the gas-liquid distribution and pressure state within the tank over time. Under long-term operating conditions, the continuous accumulation of environmental heat load further exacerbates these processes, making the maintenance of cryogenic conditions and the control of the evaporation process more complex, thus posing new technical challenges to the stable storage and transportation of cryogenic liquefied gases.

[0004] Existing cryogenic storage tank insulation measures mainly rely on passive cryogenic insulation technologies, including high-density insulation, high-vacuum insulation, and multi-layer insulation. These technologies reduce conductive, convective, and radiative heat transfer, and as much as possible, block the transfer of ambient heat to the inner tank, thereby slowing down the evaporation and pressure rise of the cryogenic liquid. However, once the system structure and material parameters are determined, the insulation performance of these passive thermal management schemes is difficult to actively adjust according to changes in external heat load. Under long-term operation or variable operating conditions, there is still room for improvement in their thermal management capabilities. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a cryogenic liquid storage device that reduces the heat load transferred to the inner tank and suppresses the evaporation process of cryogenic liquid, thereby improving the ability of the storage tank to maintain cryogenic conditions and enabling the device to adapt to the application requirements under long-cycle operation and variable operating conditions.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A cryogenic liquid storage device includes, from the outside to the inside, an outer tank, a first insulation layer, a cold shield, a second insulation layer, and an inner tank. The cold shield is a pump-assisted evaporation cold shield, comprising an outer cold shield plate, an inner cold shield plate, a dispersed evaporation section, and a liquid-absorbing core. The liquid-absorbing core is disposed on the inner surface of the outer cold shield plate. The dispersed evaporation section is disposed between the outer and inner cold shield plates and fixed to the outer cold shield plate. A gap exists between the dispersed evaporation section and the inner cold shield plate for vapor to rise. It includes multiple levels of liquid storage tanks distributed along the height, each tank being enclosed by a decentralized evaporation section and an external cooling screen. The upper and lower levels of liquid storage tanks are connected by overflow pipes, and the cryogenic liquid working fluid is sequentially distributed to each level of the liquid storage tanks along the height direction through these overflow pipes. An air extraction component and a liquid replenishment component are connected to the pump-evaporation cooling screen. The air extraction component is used to extract the working fluid vapor, which is vaporized by the endothermic reaction of the cryogenic liquid working fluid, from within the pump-evaporation cooling screen. The liquid replenishment component is used to replenish the cryogenic liquid working fluid to each level of the liquid storage tanks within the pump-evaporation cooling screen.

[0007] The liquid storage tank includes a bottom and a wall. The bottom extends circumferentially along the outer cooling screen. The outer edge of the bottom is connected to the inner wall of the outer cooling screen, and the inner edge is connected to the bottom of the wall. The bottom, wall, and inner wall of the outer cooling screen together form a liquid storage tank with an annular channel for containing a cryogenic liquid working fluid.

[0008] The pump-evaporation cooling screen also includes a support block, which is located at the bottom inside the cooling screen and between the outer cooling screen plate and the inner cooling screen plate. The porous liquid suction core is distributed alternately with each level of liquid storage tank along the inner surface of the outer cooling screen plate. That is, the liquid suction core is separated by the bottom of each level of liquid storage tank, and each level of liquid storage tank corresponds to one liquid suction core for pumping the low temperature liquid working fluid in the corresponding liquid storage tank.

[0009] It also includes a control module; the control module includes a pressure sensor, a liquid level sensor and a controller; the pressure sensor is located inside the pump-evaporation cooling screen; the liquid level sensor is located in the bottom liquid storage tank of the dispersed evaporation section; the controller is connected to the pressure sensor, the liquid level sensor, the vacuum pump and the replenishment valve, and the controller controls the start and stop of the vacuum pump according to the detection signal of the pressure sensor, and controls the opening and closing of the replenishment valve according to the detection signal of the liquid level sensor.

[0010] When the pressure sensor detects that the internal pressure of the pumped evaporator cooling screen has increased to a second set pressure value, the controller controls the vacuum pump to start pumping air; when the internal pressure of the pumped evaporator cooling screen has decreased to a first set pressure value, the controller controls the vacuum pump to shut down. When the liquid level sensor detects that the liquid level in each storage tank is lower than the first set liquid level, the controller controls the liquid replenishment valve to open for liquid replenishment; when the liquid level rises to a level higher than the second set liquid level, the controller controls the liquid replenishment valve to close.

[0011] The first set pressure value is greater than the saturation pressure of the freezing point of the cryogenic liquid working medium and less than the second set pressure value, and the second set pressure value is less than the atmospheric pressure outside the device; the first set liquid level is lower than the second set liquid level, and the second set liquid level is level with the overflow pipe.

[0012] The cryogenic liquid is a high-value liquefied gas, including but not limited to liquid hydrogen and liquid helium.

[0013] The cryogenic liquid storage device provided by this invention uses a pump-assisted evaporation cooling screen installed between the outer and inner tanks. This pump-assisted evaporation cooling screen is an active evaporation cooling screen that intercepts heat transferred from the external environment, thereby reducing the effective heat load transferred to the inner tank and suppressing the evaporation loss of the cryogenic liquid. The decentralized evaporation section includes multi-stage storage tanks and multiple overflow pipes. The multi-stage storage tanks are distributed along the height, forming a liquid containment structure distributed along the height direction inside the pump-assisted evaporation cooling screen. The cryogenic liquid working fluid in the decentralized evaporation section enters each stage of the storage tank sequentially under the guidance of the overflow pipes and is distributed step by step along the height direction under the action of gravity. When heat is transferred through the outer cooling screen, the cryogenic liquid working fluid undergoes evaporation and heat absorption in each stage of the storage tank, thereby forming a decentralized evaporation heat exchange interface in space. This avoids the evaporation process being concentrated on the surface of a single storage tank, increases the evaporation heat exchange area, and avoids the problem of evaporation only occurring on the surface due to depth. This achieves the interception and consumption of heat transferred from the first insulation layer, reduces the heat transferred to the inner tank, and suppresses the evaporation loss of the cryogenic liquid.

[0014] The working principle of the cryogenic liquid storage device provided by this invention is as follows: during the operation of the cryogenic liquid storage device, the heat from the external environment is first transferred to the first insulation layer through the outer tank. After being weakened by the first insulation layer, it enters the pump-evaporation cooling screen. The pump-evaporation cooling screen controls the internal temperature within a set range for a long time by combining two methods: pumping working fluid vapor and replenishing liquid working fluid. The heat transferred from the pump-evaporation cooling screen to the inner side is transferred to the inner tank through the second insulation layer, which significantly reduces the heat flux entering the inner tank, thereby effectively suppressing the evaporation rate of the cryogenic liquid in the inner tank.

[0015] The outer tank is a pressure-bearing structure between the external environment and the first insulation layer, used to physically isolate the cryogenic components inside the device from the ambient temperature environment. The outer tank has sufficient structural strength to withstand the loads of the external environment, enabling it to withstand external air pressure, its own weight, and additional loads during the operation, storage, and transportation of the device, providing reliable mechanical support for the internal structure of the cryogenic liquid storage device. At the same time, the outer tank provides external protection for the inner tank, the first insulation layer, the second insulation layer, and the pump evaporation cooling screen, ensuring the integrity and stability of the overall structure and providing a basic structural guarantee for the safe storage of cryogenic liquids.

[0016] Both the first and second insulation layers are vacuum insulation structures, with their internal space evacuated to a high vacuum state. This creates a low-molecular-density, high-vacuum insulation environment between the outer tank and the pump-evaporation cooling screen, and between the pump-evaporation cooling screen and the inner tank. Their surfaces are treated with liquid-based polishing, acid washing, or non-annealing to reduce their emissivity. These treatments effectively suppress conduction, convection, and radiation heat transfer processes that may occur during device operation, significantly increasing the overall thermal resistance between the outer and inner tanks. This reduces the heat transferred from the external environment to the inner tank, providing a reliable insulation foundation for the long-term, safe storage of cryogenic liquids.

[0017] The inner tank is a storage tank structure used for the direct containment and long-term sealed storage of cryogenic liquids. The inner tank can adapt to pressure and stress changes caused by temperature variations during cryogenic liquid storage, and possesses the ability to maintain good mechanical properties and structural stability under long-term cryogenic conditions and repeated temperature fluctuations. This addresses the impact of cryogenic embrittlement, thermal stress concentration, or deformation on the tank's structural sealing performance that may occur during storage and transportation. By maintaining the integrity and sealing performance of the inner tank structure, the risk of cryogenic liquid leakage can be reduced, providing a sealing foundation for the safe and reliable operation of cryogenic liquid storage devices.

[0018] The external cooling plate is a separating component between the pump-evaporating cooling plate and the first insulation layer. It structurally separates the pump-evaporating cooling plate from the first insulation layer and serves as the main heat-receiving interface of the pump-evaporating cooling plate, receiving heat transferred from the first insulation layer. The external cooling plate transfers this heat along its inner surface to the connected dispersed evaporation section and porous wick, ensuring sufficient contact between the low-temperature liquid working fluid in the dispersed evaporation section and the external cooling plate, resulting in evaporation and heat absorption. This dissipates the heat transferred from the external environment as the latent heat of phase change of the working fluid, thus intercepting external heat.

[0019] The internal cooling plate is a partition between the pump-evaporator cooling plate and the second insulation layer, forming the inner wall structure of the pump-evaporator cooling plate facing the inner tank. As the heat transfer interface inside the pump-evaporator cooling plate, the internal cooling plate receives convective heat generated by the flow of working fluid vapor inside the pump-evaporator cooling plate, as well as heat radiated inwards from other structural components inside the pump-evaporator cooling plate, and transfers this heat to the second insulation layer. The internal cooling plate creates a clear heat transfer boundary inside the pump-evaporator cooling plate, reducing direct heat transfer towards the inner tank, which is beneficial for further reducing heat intrusion in conjunction with the second insulation layer.

[0020] The support block is a supporting component connecting the outer and inner cold shield plates. It has sufficient structural strength to withstand the loads of the inner cold shield plate, the second insulation layer, and the inner tank, maintaining the stability of the overall structure of the pump-driven evaporator cold shield during operation, storage, and transportation. Through the cooperation of the support block with the outer and inner cold shield plates, the three together form a stable spatial structure, ensuring that the geometry and spacing of the enclosed space inside the pump-driven evaporator cold shield remain unchanged, providing a structural foundation for the stable operation of the evaporation heat exchange process.

[0021] An overflow pipe is a connecting structure installed between adjacent storage tanks. It establishes a fluid communication channel for cryogenic liquids between multiple storage tanks, enabling the tiered overflow and distribution of cryogenic liquids among each tank level. The overflow pipe allows for the adjustment and stabilization of the liquid levels in each storage tank, ensuring a continuous and uniform supply of cryogenic liquid during evaporation. This increases the evaporation heat exchange area and avoids surface-level evaporation due to depth limitations. During operation, when the cryogenic liquid level in the next storage tank rises above the top of the overflow pipe, the liquid flows spontaneously into the next storage tank under gravity, distributing the cryogenic liquid along the height and forming a stable liquid transport path within each tank. This achieves stable delivery and tiered supply of the cryogenic working fluid.

[0022] The porous wick has a porous structure, and the capillary force between its pores draws the cryogenic working fluid to the inner wall of the outer cooling plate, thereby increasing the evaporation heat exchange area. When the cryogenic liquid working fluid in the storage tank comes into contact with the porous wick, the liquid surface between the pores of the porous material is depressed, generating capillary force that drives the cryogenic liquid working fluid to rise along the pores. This allows the cryogenic liquid working fluid to cover the inner surface of the outer cooling plate without external power, thus expanding the evaporation heat exchange interface.

[0023] The evacuation unit establishes and maintains a stable operating state within a set pressure range inside the pump-evaporator cooling screen, providing the necessary pressure conditions for the continuous evaporation and heat absorption of the cryogenic liquid working fluid. The evacuation pipe continuously extracts the working fluid vapor generated by the evaporation of the cryogenic liquid working fluid inside the pump-evaporator cooling screen during vacuum pump operation, thereby reducing the pressure in the gas space inside the pump-evaporator cooling screen. The evacuation pipe creates a stable low-pressure environment inside the pump-evaporator cooling screen, providing the necessary pressure conditions for the continuous evaporation of the cryogenic liquid working fluid and ensuring that the vaporous working fluid generated during evaporation is promptly discharged, preventing gas accumulation from adversely affecting the evaporation process.

[0024] The vacuum pump is the evacuation actuator used to actively evacuate the gas space inside the evaporator cooling screen, thereby reducing the working pressure inside the screen. When the vacuum pump is running, it continuously draws in the working fluid vapor, lowering the pressure within the gas space and thus reducing the saturation temperature of the cryogenic liquid working fluid in the storage tank, inducing evaporation. By adjusting the operating status of the vacuum pump, the evaporation temperature inside the evaporator cooling screen can be controlled, making the evaporation heat exchange process somewhat adjustable to adapt to changes in heat load under different operating conditions.

[0025] A check valve is used to prevent external air or gas from flowing back into the vacuum pump and the pump-evaporator cooling screen during the pumping process. The check valve is open when the vacuum pump is operating, allowing gas to flow out in one direction, and automatically closes when the vacuum pump stops or pumping is interrupted, thus preventing external ambient gas from flowing back into the pumping pipe and the pump-evaporator cooling screen. By using a check valve, the pressure inside the pump-evaporator cooling screen can be effectively maintained, preventing the pressure environment inside the pump-evaporator cooling screen from being disrupted by backflow of external gas, and improving the safety and stability of the pumping components.

[0026] The liquid replenishment component includes a liquid replenishment pipe, a liquid replenishment valve, and a working fluid storage tank. One end of the liquid replenishment pipe is connected to the top-level storage tank of the decentralized evaporation section, and the other end is connected to the working fluid storage tank via the liquid replenishment valve. The liquid replenishment component establishes a fluid transport channel between the working fluid storage tank and the pump-driven evaporation cooling screen through the liquid replenishment pipe, and controls the start and stop of the liquid replenishment process from the working fluid storage tank to the pump-driven evaporation cooling screen by opening and closing the liquid replenishment valve. When a low-pressure environment is formed inside the pump-driven evaporation cooling screen under the action of air extraction, the cryogenic liquid working fluid in the working fluid storage tank spontaneously flows into the top-level storage tank through the liquid replenishment pipe under the action of pressure difference, thereby maintaining the stability of the liquid level in the liquid space and ensuring the continuity and stability of the evaporation heat exchange process.

[0027] The replenishment pipeline serves as a liquid transport channel, with one end connected to the top-level storage tank and the other end connected to the working fluid storage tank via a replenishment valve. During the replenishment process, the replenishment pipeline introduces the working fluid from the storage tank into the pump-evaporator cooling screen to replenish the low-temperature liquid working fluid consumed during evaporation. The replenishment pipeline ensures a clear transport path for the replenishment process, guaranteeing a stable flow of the working fluid into the pump-evaporator cooling screen, thereby maintaining the liquid level in the storage tank and ensuring the continuous occurrence of the evaporation heat exchange process.

[0028] The replenishment valve controls the transport of the cryogenic working fluid from the working fluid storage tank to the pump-evaporator cooling screen. When the replenishment valve is open, the vacuum pump continuously evacuates air from inside the pump-evaporator cooling screen, creating a low-pressure area. This generates a pressure difference between the working fluid storage tank and the pump-evaporator cooling screen, causing the cryogenic working fluid to be spontaneously transported along the replenishment pipeline to the top-level storage tank inside the pump-evaporator cooling screen under this pressure difference. By controlling the opening and closing of the replenishment valve, the start / stop and replenishment volume of the replenishment process can be adjusted to maintain the stability of the cryogenic working fluid quality within the pump-evaporator cooling screen and prevent a decrease in evaporative heat exchange capacity due to insufficient working fluid.

[0029] The working fluid storage tank is a storage container capable of holding cryogenic fluids and is used to store cryogenic working fluids. The working fluid storage tank is connected to the inside of the pump-evaporation cooling screen via a replenishment pipe, and when the replenishment valve is opened, it supplies the cryogenic liquid working fluid required for evaporation to the inside of the pump-evaporation cooling screen. The working fluid storage tank has a higher pressure than the pump-evaporation cooling screen; therefore, the cryogenic liquid working fluid in the working fluid storage tank will spontaneously flow towards the pump-evaporation cooling screen under the pressure difference between the working fluid storage tank and the pump-evaporation cooling screen, achieving a spontaneous replenishment process without external force.

[0030] Compared with existing passive cooling methods such as high vacuum insulation, multi-layer insulation materials, or fixed-temperature cold shields, the active evaporation cold shield structure introduced in this invention has at least the following beneficial effects: This invention achieves active regulation of the inner tank's heat load by introducing a pressure-adjustable pump-assisted evaporative cooling screen. Existing thermal management methods for cryogenic storage tanks primarily rely on vacuum insulation and low thermal conductivity materials. Their heat transfer capacity is essentially fixed once the structure and materials are determined, making dynamic adjustment difficult in response to changes in external heat load. However, the pump-assisted evaporative cooling screen can maintain its temperature at the cryogenic working fluid evaporation temperature. When the external heat load increases, the evaporation rate of the cryogenic working fluid inside the pump-assisted evaporative cooling screen increases accordingly, and the heat absorption capacity increases simultaneously. At this point, the temperature of the pump-assisted evaporative cooling screen is only related to the screen pressure. The vacuum pump actively draws vapor from the working fluid inside the cooling screen, changing the internal pressure and thus altering the cryogenic working fluid evaporation temperature, thereby achieving temperature regulation of the pump-assisted evaporative cooling screen. The inner tank's heat load originates from the heat transferred from the cooling screen plate through the second insulation layer; therefore, regulating the pump-assisted evaporative cooling screen temperature enables active regulation of the inner tank's heat load.

[0031] This invention combines the active control capability of a pump-driven evaporative cooling screen with the passive insulation capability of a double-layer vacuum insulation structure to construct a coupled active-passive low-temperature thermal management method. The first insulation layer weakens external ambient heat, the pump-driven evaporative cooling screen actively dissipates residual heat, and the second insulation layer further suppresses heat intrusion into the inner tank. These three layers are arranged sequentially along the heat flow path, resulting in a gradual attenuation of heat. This structural design enhances the system's adaptability to ambient temperature fluctuations and uncertainties in heat load, making it particularly suitable for long-haul transportation or applications with frequently changing operating conditions.

[0032] This invention utilizes a decentralized evaporation section structure to construct a multi-interface evaporation heat exchange mode, avoiding evaporation concentration on the surface of a single storage tank and enabling more uniform evaporation heat exchange across the entire pump-driven evaporation cooling screen. The pump-driven evaporation cooling screen contains multiple levels of storage tanks distributed along its height, connected by overflow pipes. The internal pressure is lower than the pressure inside the working fluid storage tank, allowing the cryogenic liquid working fluid to spontaneously flow from the working fluid storage tank into the top-level storage tank inside the cooling screen without external power. When the cryogenic working fluid exceeds the overflow pipe of the top-level storage tank, it flows down the overflow pipe to the next level of storage tank under gravity, thus achieving a progressive distribution of the liquid working fluid and spatially dispersing the evaporation process. Compared to traditional cooling screen structures with a single storage tank or a concentrated evaporation interface, this decentralized evaporation section effectively avoids the problem of uneven heat exchange caused by evaporation concentration in a localized area.

[0033] This invention achieves complete coverage of the inner surface of the external cooling screen with a low-temperature working fluid through a capillary liquid absorption structure, improving the temperature uniformity of the external cooling screen. The porous liquid absorption core continuously spreads the liquid on the inner surface of the external cooling screen through capillary action, ensuring a stable and continuous evaporation process and making the heat capture by the cooling screen more uniform and reliable. After contacting the low-temperature liquid in the storage tank, the porous liquid absorption core generates capillary force, causing the liquid to rise along the pores and spread on the inner side of the external cooling screen without external power, forming a stable liquid film. This structure improves the effective evaporation heat exchange area and temperature uniformity of the external cooling screen, giving the pump-driven evaporation cooling screen a stronger cold retention capacity. Attached Figure Description

[0034] Figure 1 Overall schematic diagram of a cryogenic liquid storage device; Figure 2 Schematic diagram of a decentralized evaporation section; Figure 3 Schematic diagram of the pumping and transporting process of the working fluid from the evaporator cooling screen; Figure 4 Schematic diagram of porous liquid absorption core structure; Wherein: 101-Outer tank; 102-First insulation layer; 103-Pump evaporation cooling screen; 104-Second insulation layer; 105-Support block; 106-Inner tank; 107-Liquid replenishment pipe; 108-Replenishment valve; 109-Working fluid storage tank; 110-Gas extraction pipe; 111-Vacuum pump; 112-One-way valve; 113-Pressure sensor; 114-Level sensor; 115-Controller; LN2-Liquid nitrogen; N2-Nitrogen gas; 201-Dispersed evaporation section; 301-Overflow pipe; 302-Cryogenic liquid working fluid; 303-Storage tank; 304-Porous liquid suction core; 305-Working fluid vapor; 306-Inner cooling screen plate; 307-Outer cooling screen plate. Detailed Implementation

[0035] To enhance understanding of the present invention, specific embodiments will be further described below with reference to the accompanying drawings. These embodiments are used to explain the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0036] Figure 1 The overall structure of the cryogenic liquid storage device is shown, including an outer tank 101, a first insulation layer 102, a pump-evaporation cooling screen 103, a second insulation layer 104, and an inner tank 106. An air extraction component and a liquid replenishment component are installed on the pump-evaporation cooling screen 103. The outer tank 101 is located outside the first insulation layer, the first insulation layer 102 is located between the outer tank 101 and the pump-evaporation cooling screen 103, and the second insulation layer 104 is located between the pump-evaporation cooling screen 103 and the inner tank 106. The pump-evaporation cooling screen 103 is located between two insulation layers, and the inner tank 106 is located inside the second insulation layer 104. The outer tank 101 is cylindrical in the middle and has hemispherical end caps on both sides, which are used to withstand external environmental loads and provide overall mechanical protection for the internal structure. The inner tank 106 is similar in shape to the outer tank 101, and all points on it are equidistant from the outer tank 101, which is used to store cryogenic liquids. The first insulation layer 102 and the second insulation layer 104 are both in a high vacuum environment, and the heat transfer mode is mainly radiation heat transfer.

[0037] The air extraction component includes an air extraction pipe 110, a vacuum pump 111, and a one-way valve 112. One end of the air extraction pipe 110 is connected to the pump-evaporation cooling screen 103, and the other end is connected to the vacuum pump 111 and the one-way valve 112 in sequence and is open to the outside atmosphere. The vacuum pump 111 and the one-way valve 112 are both outside the outer tank 101. The vacuum pump 111 is used to actively extract air from the pump-evaporation cooling screen 103 to reduce the internal pressure. The one-way valve 112 is used to prevent external air from flowing back into the pump-evaporation cooling screen 103 when the air extraction is interrupted or the vacuum pump stops.

[0038] The liquid replenishment components include a liquid replenishment pipe 107, a liquid replenishment valve 108, and a working fluid storage tank 109. One end of the liquid replenishment pipe 107 is connected to the top-level liquid storage tank of the decentralized evaporation section 201, and the other end is connected to the working fluid storage tank 109 via the liquid replenishment valve 108. Both the liquid replenishment valve 108 and the working fluid storage tank 109 are located outside the outer tank 101. The working fluid storage tank 109 is used to store cryogenic liquid working fluid. Its internal pressure is higher than the working pressure inside the pump-assisted evaporation cooling screen 103. When the liquid replenishment valve 108 is opened, the cryogenic liquid working fluid flows spontaneously into the top-level liquid storage tank along the liquid replenishment pipe 107 under the action of the pressure difference, thereby replenishing the working fluid consumed during the evaporation process.

[0039] The cryogenic liquid storage device also includes a control module. The control module includes a pressure sensor 113, a liquid level sensor 114, and a controller 115. The pressure sensor 113 is installed in the gas space inside the pump-evaporation cooling screen 103 to detect the internal pressure in real time. The liquid level sensor 114 is installed in each layer of the liquid storage tank 303 in the decentralized evaporation section 201 to detect the liquid level. The controller 115 is installed outside the outer tank and is electrically connected to the pressure sensor 113, the liquid level sensor 114, the vacuum pump 111, and the replenishment valve 108.

[0040] During device operation, when pressure sensor 113 detects that the internal pressure of the pump-evaporation cooling screen 103 has risen to the second set pressure value, controller 115 controls vacuum pump 111 to start pumping air; when the pressure drops to the first set pressure value, controller 115 controls vacuum pump 111 to stop running, thereby stabilizing the internal pressure of the pump-evaporation cooling screen 103 within the set range. When liquid level sensor 114 detects that the liquid level in the bottom storage tank is lower than the first set liquid level, controller 115 controls replenishment valve 108 to open for replenishment; when the liquid level rises back to above the second set liquid level, controller 115 controls replenishment valve 108 to close, thereby maintaining the stability of the liquid working fluid content inside the pump-evaporation cooling screen 103.

[0041] like Figure 3 As shown, the pump-evaporation cooling screen 103 includes an outer cooling screen plate 307, an inner cooling screen plate 306, a support block 105, a dispersed evaporation section 201, and a porous liquid suction core 304. The outer cooling screen plate 307 is located on the outer side of the pump-evaporation cooling screen 103, facing the first insulation layer 102; the inner cooling screen plate 306 is located on the inner side of the pump-evaporation cooling screen 103, facing the second insulation layer 104; the support block 105 is located at the bottom inside the pump-evaporation cooling screen 103, with its upper end connected to the inner cooling screen plate 306 and its lower end connected to the outer cooling screen plate 307. After the outer cooling screen plate 307, the inner cooling screen plate 306, and the support block 105 are interconnected, they together enclose a closed space for containing the low-temperature working fluid.

[0042] The overall structure of the decentralized evaporation section is as follows: Figure 2As shown, the decentralized evaporation section 201 includes multi-stage liquid storage tanks 303 and multiple overflow pipes 301. The multi-stage liquid storage tanks 303 are distributed along the height, and the liquid storage tanks at each stage are connected by overflow pipes 301, forming liquid storage tanks 303 distributed along the height direction inside the pump-assisted evaporation cooling screen 103. The liquid storage tank 303 includes a liquid storage tank bottom 401 and a liquid storage tank wall 402. The liquid storage tank bottom 401 extends circumferentially along the outer cooling screen plate, and the outer edge of the liquid storage tank bottom 401 is connected to the inner wall surface of the outer cooling screen plate 307. The inner edge of the liquid storage tank bottom 401 is connected to the bottom end of the liquid storage tank wall 402. The liquid storage tank bottom 401, the liquid storage tank wall 402, and the inner wall surface of the outer cooling screen plate 307 together form a liquid storage tank 303 with annular channels for containing low-temperature liquid working fluid.

[0043] Figure 3 The process of transporting the liquid working medium in the pump-evaporation cooling screen is also demonstrated. The cryogenic liquid working medium 302 in the decentralized evaporation section 201 enters the storage tanks 303 in stages under the guidance of the overflow pipe 301: when the liquid level of the cryogenic liquid working medium 302 in the upper storage tank rises and exceeds the height of the top of the overflow pipe between the two storage tanks, the cryogenic liquid working medium 302 flows spontaneously into the lower storage tank under the action of gravity through the overflow pipe between the two storage tanks, so that the cryogenic liquid working medium 302 is distributed in stages along the height direction and forms a stable liquid transport path in each storage tank; the cryogenic liquid working medium 302 evaporates and absorbs heat on the surface of each storage tank 303, and the generated working medium vapor rises from the gap between the inner cooling plate and the storage tank 303, and leaves the pump-evaporation cooling screen 103 through the exhaust pipe 110.

[0044] Figure 4 A schematic diagram of the porous wick structure is shown. The porous wick 304 is disposed on the inner surface of the outer cooling plate 307 and is staggered with the various levels of liquid storage tanks 303. When the porous wick 304 comes into contact with the cryogenic liquid working medium 302 in the liquid storage tank 303, it can transport the cryogenic liquid working medium upward along the inner wall of the outer cooling plate 307 under the action of capillary force, so that a continuous and stable liquid film is formed on the inner surface of the outer cooling plate 307, thereby increasing the evaporation heat exchange area.

[0045] The external and internal cooling panels should be made of metal materials with good low-temperature toughness, relatively low thermal conductivity, low vacuum outgassing rate and sufficient structural strength, including but not limited to austenitic stainless steel or aluminum alloy.

[0046] The support block should be made of a material with high specific strength, low thermal conductivity and a coefficient of thermal expansion that matches that of the cold shield material, in order to bear the mechanical load and reduce heat leakage, including but not limited to glass fiber reinforced epoxy resin composite material or polyimide composite material.

[0047] The storage tank and overflow pipe should be made of metal materials that are compatible with the working fluid in the storage tank, resistant to low-temperature impact, and easy to form or weld, including but not limited to aluminum alloy or stainless steel.

[0048] The porous liquid wick should be made of porous materials with excellent capillary properties, good wettability with the working fluid in the storage tank, and the ability to work at low temperatures for a long time, including but not limited to metal wire mesh or sintered porous materials.

[0049] In this embodiment, heat from the external environment first enters the first insulation layer 102 through the outer tank 101. After being weakened by the first insulation layer 102, the heat enters the pump-evaporation cooling screen 103. The heat is transferred to its inner side through the outer cooling screen plate 307, where it exchanges heat with the liquid film formed by the porous liquid wick 304 and the cryogenic liquid working fluid 302 in each level of the liquid storage tank 303. The cryogenic liquid working fluid 302 evaporates and absorbs heat under the low-pressure environment created by the pumping. The working fluid vapor 305 generated by evaporation is continuously drawn out by the vacuum pump 111 through the pumping pipe 110, thereby maintaining the continuity of the evaporation process. The remaining heat weakened by the pump-evaporation cooling screen 103 is then transferred to the inner tank 106 through the second insulation layer 104, significantly reducing the effective heat flux entering the inner tank 106, thereby effectively suppressing the evaporation loss of the cryogenic liquid in the inner tank 106.

[0050] Example This embodiment provides a calculation case for the cold insulation effect of pump-assisted evaporation and cold shield. This case ignores the thermal resistance of the tank, the equivalent thermal conductivity of the insulation layer, and only considers the gray body radiation, which is an idealized lower limit estimate.

[0051] Assuming ambient temperature T =300 K. The inner tank stores liquid hydrogen as the working fluid, with a latent heat of vaporization of... h H ≈ 446 kJ / kg, the temperature of liquid hydrogen inside the inner tank is T i = 20K. The working fluid pumped into the evaporator cooling screen is liquid nitrogen. The inner surface of the outer tank, the outer surface of the outer cooling screen plate, the outer surface of the inner cooling screen plate, and the outer surface of the inner tank are all subjected to liquid-filled polishing treatment, and their surface emissivity is taken. ε = 0.15. The outer tank, cold shield, and inner tank are all cylindrical with two semi-circular heads. The inner surface area of ​​the outer tank is... A o =75 m 2 External cold shield surface area A s,o 67m 2 Inner surface area of ​​the internal cooling screen A s,i 66 m 2 The inner tank has a surface area of ​​58 m². 2 The equivalent volume of the cold screen gas space is V = 0.78 m³. 3 It remains approximately constant within one period.

[0052] For the radiation of two gray bodies in a coaxial closed cavity, the area of ​​the enclosed inner surface is... A 1. Emission rate ε 1. The area of ​​its surrounding outer surface is A 2. Emission rate ε 2. Radiative heat transfer for:

[0053] In the formula, The Stefan-Boltzmann constant; The temperature of the heat source; The temperature of the cold source; The heat flow from the outer tank to the outer cooling screen plate Q 1. Heat flow from the internal cooling screen to the inner tank Q 2 can be calculated using the above formula.

[0054] To lower the temperature of the cooling screen and reduce the amount of liquid hydrogen evaporating from the inner tank, this embodiment controls the liquid nitrogen saturation temperature to the lowest possible level by evacuating the tank. T 1 = 66 K, corresponding to the first saturation pressure P l The pressure is 20 kPa; then it slowly rises back to the highest temperature. T 2 = 77 K, corresponding to the second saturation pressure P h Approximately 101 kPa. Vacuum pump outlet pressure. P out At atmospheric pressure of 101.3 kPa, pump efficiency η 50%, pumping speed Constantly 0.5 m 3 / s.

[0055] The pump work for one pumping cycle is calculated below. One pumping cycle can be divided into two stages: the pumping stage starts the vacuum pump, and the pressure rises from the second saturation pressure... P h Reduced to the first saturation pressure P l During the natural recovery phase, pumping stops, and the pressure drops from the first saturation pressure. P l Rise to the second saturation pressure P h .

[0056] The average temperature of nitrogen during the extraction phase T a Mean pressure P a Average latent heat of vaporization h a It is approximately the average of the two states before and after evacuation. The mass flow rate of nitrogen evaporation. The net heat flux into the cold screen can be divided by the average latent heat of vaporization during the pumping process.

[0057] Assume the vacuum pump's pumping speed is The required evacuation time is t p According to the principle of conservation of energy, the following equation can be derived:

[0058] In the formula, It is the ideal gas constant; For vacuum pump pumping speed; Assuming the pressure rise after pumping stops is entirely due to continuous evaporation, the time required for natural recovery... The mass difference before and after evacuation can be calculated as the ratio of the mass flow rate of nitrogen evaporation.

[0059] Assuming the vacuum pump performs isothermal compression, the average power of the actual vacuum pump during its duty cycle is... for:

[0060] Let the average heat flow entering the inner tank during the period be... It is approximately the average value of the heat flow transferred from the cold screen to the inner tank at the beginning and end of each pumping operation. Assume the inner tank has an exhaust valve to control the pressure. Daily evaporation of liquid hydrogen for:

[0061] Daily evaporation rate The ratio of the daily evaporated mass of liquid hydrogen to the mass of liquid hydrogen in the inner tank is given, assuming the volume of liquid hydrogen in the inner tank is 90% of the total volume of the inner tank.

[0062] Simulation results show that a cycle duration is approximately 4.5 minutes, with pumping time of approximately 2 seconds, an average pump power of 220 W, and a daily liquid hydrogen evaporation rate of approximately 0.1% / day. This power level and daily evaporation rate demonstrate good economic viability and feasibility for long-term cold-keeping operation of liquid hydrogen storage tanks.

Claims

1. A cryogenic liquid storage device, comprising, from the outside to the inside, an outer tank, a first insulation layer, a cold shield, a second insulation layer, and an inner tank, characterized in that, The cold screen is a pump-assisted evaporation cold screen, which includes an outer cold screen plate, an inner cold screen plate, a dispersed evaporation section, and a liquid suction core. The liquid suction core is disposed on the inner surface of the outer cold screen plate. The dispersed evaporation section is disposed between the outer and inner cold screen plates and fixed to the outer cold screen plate. There is a gap between the dispersed evaporation section and the inner cold screen plate for steam to rise. The dispersed evaporation section includes multiple levels of liquid storage tanks distributed along the height. The liquid storage tanks are enclosed by the dispersed evaporation section and the outer cold screen plate. The upper and lower level liquid storage tanks are connected by an overflow pipe. The cryogenic liquid working fluid is distributed sequentially to each level of the liquid storage tank along the height direction through the overflow pipe. An air extraction component and a liquid replenishment component are connected to the pump-assisted evaporation cold screen. The air extraction component is used to extract the working fluid vapor, which is vaporized by the endothermic reaction of the cryogenic liquid working fluid, from inside the pump-assisted evaporation cold screen. The liquid replenishment component is used to replenish the cryogenic liquid working fluid to each level of the liquid storage tank inside the pump-assisted evaporation cold screen.

2. The cryogenic liquid storage device according to claim 1, characterized in that, The liquid storage tank includes a bottom and a wall. The bottom extends circumferentially along the outer cooling screen. The outer edge of the bottom is connected to the inner wall of the outer cooling screen, and the inner edge is connected to the bottom of the wall. The bottom, wall, and inner wall of the outer cooling screen together form a liquid storage tank with an annular channel for containing a cryogenic liquid working fluid.

3. The cryogenic liquid storage device according to claim 1, characterized in that, The pump-evaporation cold screen also includes a support block, which is located at the bottom inside the cold screen and between the outer cold screen plate and the inner cold screen plate.

4. The cryogenic liquid storage device according to claim 2, characterized in that, The inner surface of the outer cooling screen is covered by the liquid-absorbing core, and the liquid-absorbing core is embedded in the bottom of each level of liquid storage tank.

5. The cryogenic liquid storage device according to claim 1, characterized in that, The extraction component includes an extraction pipe, a vacuum pump, and a one-way valve; the vacuum pump is connected to the internal space of the pump evaporation cooling screen through the extraction pipe, and the one-way valve is installed on the extraction pipe.

6. The cryogenic liquid storage device according to claim 1, characterized in that, The replenishment component includes a replenishment pipe, a replenishment valve, and a working fluid storage tank; one end of the replenishment pipe is connected to the top-level liquid storage pool inside the cold shield, and the other end of the replenishment pipe is connected to the working fluid storage tank via the replenishment valve.

7. The cryogenic liquid storage device according to claim 1, characterized in that, Both the first and second insulation layers are vacuum insulation structures. The internal space of the vacuum insulation structure is evacuated to a high vacuum state, so that a low molecular density high vacuum insulation environment is formed between the outer tank and the pump-evaporation cold screen, and between the pump-evaporation cold screen and the inner tank.

8. The cryogenic liquid storage device according to any one of claims 1-7, characterized in that, It also includes a control module; the control module includes a pressure sensor, a liquid level sensor and a controller; the pressure sensor is installed in the internal space of the pump-evaporation cooling screen; the liquid level sensor is installed in each layer of the liquid storage tank of the dispersed evaporation section; the controller is connected to the pressure sensor, the liquid level sensor, the vacuum pump and the replenishment valve, and the controller controls the start and stop of the vacuum pump according to the detection signal of the pressure sensor, and controls the opening and closing of the replenishment valve according to the detection signal of the liquid level sensor.

9. The cryogenic liquid storage device according to claim 8, characterized in that, When the pressure sensor detects that the internal pressure of the pumped evaporator cooling screen has increased to a second set pressure value, the controller controls the vacuum pump to start pumping air; when the internal pressure of the pumped evaporator cooling screen has decreased to a first set pressure value, the controller controls the vacuum pump to shut down. When the liquid level sensor detects that the liquid level of a certain storage tank is lower than the first set liquid level, the controller controls the liquid replenishment valve to open for liquid replenishment; when the liquid level rises back to above the second set liquid level, the controller controls the liquid replenishment valve to close.

10. The cryogenic liquid storage device according to claim 9, characterized in that, The first set pressure value is greater than the saturation pressure of the freezing point of the cryogenic liquid working medium and less than the second set pressure value, and the second set pressure value is less than the atmospheric pressure outside the device; the first set liquid level is lower than the second set liquid level, and the second set liquid level is level with the overflow pipe.

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