A temperature-equalizing type cryogenic liquid fuel storage tank and a method for delaying discharge

Abstract

The present invention discloses an isothermal cryogenic liquid fuel storage tank and a method for delaying discharge, which relates to the field of cryogenic liquid fuel storage. The storage tank device is composed of a radiation cooling coating, an outer shell, a vacuum insulation layer, a reflective layer, a thermal insulation layer, an inner tank, an inner tank lining, an inner tank support, a wire mesh, a plurality of pipes and valves. The present invention utilizes the radiation cooling layer to reduce the net heat absorption of the system itself; uses the inserted wire mesh to improve the heat transfer in the tank, inhibits the slow heat transfer, and reduces the premature overpressure discharge caused by the rapid heat absorption and pressure increase in the gas phase region with low specific heat, reduces the emission loss, and achieves the purpose of long-term storage of liquid fuel. Compared with other technologies for extending the storage time, the present invention has the advantages of low energy consumption, simple structure, and low cost.

Description

Technical Field

[0001] The present invention relates to the field of cryogenic liquid fuel storage, and particularly to an isothermal cryogenic liquid fuel storage tank and a method for delaying discharge. Background Art

[0002] For higher volume density, hydrogen energy, natural gas, oxygen, etc. are usually stored for a long time or transported over long distances in the form of cryogenic liquids. Due to the large temperature difference between cryogenic liquids and the environment, heat leakage inevitably occurs during storage. Affected by natural convection, the heated high-temperature gas will gradually accumulate at the top of the tank. Since the heat transfer of the top gas is slow and the specific heat is small, it is easy to quickly increase the temperature and pressure under the condition of heat accumulation, resulting in the storage system reaching the discharge pressure in advance and discharging, causing loss of liquid fuel. Delaying overpressure discharge is of great significance to the long-term storage system of cryogenic liquid fuel. It can not only reduce the loss of cryogenic liquid fuel during storage and transportation, but also reduce the greenhouse effect and pollution caused by discharge, which is of great significance for promoting the realization of the "dual carbon goal".

[0003] At present, the methods for delaying overpressure discharge loss in the field of cryogenic liquid fuel storage are divided into active methods and passive methods. Active methods include cooling the target liquid fuel with other cryogenic liquids, such as using liquid nitrogen or liquid helium as coolants to extend the storage time of liquid fuels such as liquid hydrogen, or adding an additional cooling system, such as Chinese Patent 202222821009.1 using cryogenic helium gas to cool liquid hydrogen. However, such systems are complex in equipment, high in energy consumption, and high in cost. Chinese Patent 202210853783.2 prolongs the storage time of liquid hydrogen by a passive method of adding a catalyst in the liquid hydrogen storage tank to promote the endothermic conversion of ortho-hydrogen to para-hydrogen. However, the activity of the catalyst will gradually decline over time and eventually fail, and it is also difficult to replace after failure. Therefore, how to delay overpressure discharge with low energy consumption, low cost, and for a long time in the cryogenic liquid fuel storage system is one of the current key issues. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects in the prior art and provide a cryogenic liquid fuel storage tank device and method for delaying overpressure discharge. The present invention uses wire meshes to improve heat transfer in the tank, inhibit the phenomenon of thermal stratification, delay the premature overpressure discharge caused by the rapid increase in temperature and pressure of the top gas, reduce the loss of liquid fuel, and achieve the purpose of long-term storage.

[0005] The specific technical solutions adopted by the present invention are as follows:

[0006] In the first aspect, the present invention provides an isothermal cryogenic liquid fuel storage tank, including an outer shell, an inner tank, a filling pipe, an exhaust pipe, and a liquid supply pipe;

[0007] The outer shell and the inner tank are coaxially sleeved and supported and connected by the inner tank, and a vacuum insulation layer is formed in the area between the outer shell and the inner tank; a heat insulation layer is laid on the outer wall of the inner tank, and a reflective layer is laid on the outside of the heat insulation layer; an inner lining of the inner tank is laid on the inner wall of the inner tank, and a wire mesh is filled inside the inner tank; a radiation cooling coating is applied on the outer wall of the outer shell;

[0008] One end of the filling pipe extends into the top inside the inner tank, and the other end is located outside the outer shell and is respectively connected to a filling pressure gauge and a filling valve; one end of the exhaust pipe extends into the top inside the inner tank, and the other end is located outside the outer shell and is respectively connected to a barometer and the first port of a three-way pipe; the second port of the three-way pipe is connected to a discharge pipe and a discharge valve, and the third port is connected to a gas supply pipe and a gas supply valve; one end of the liquid supply pipe extends into the bottom inside the inner tank, and the other end is located outside the outer shell and is connected to a liquid supply valve.

[0009] Preferably, part of the filling pipe is embedded in the inner tank support at the top for fixation, and the exhaust pipe and the liquid supply pipe are respectively partially embedded in the inner tank support on the side for fixation.

[0010] Preferably, the heat insulation layer is composed of multiple layers of heat insulation materials, and the heat insulation materials include one or a combination of more of fiberglass, aluminum silicate rock wool, glass wool and aerogel materials.

[0011] Preferably, the placement method of the isothermal cryogenic liquid fuel storage tank is vertical or horizontal, and the model is a C-type storage tank, a Dewar tank or a spherical tank.

[0012] Preferably, the shape of the wire mesh includes a herringbone mesh, a Z-shaped mesh, a diamond mesh, a horseshoe mesh, a chain mesh, an eyeglass mesh, a chain plate mesh or a spherical mesh.

[0013] Preferably, the material of the wire mesh is foam metal, carbon fiber, aluminum or steel.

[0014] Preferably, the end of the filling pipe extending into the inner tank protrudes from the inner lining of the inner tank, so that the liquid inside the inner tank cannot be completely filled.

[0015] In a second aspect, the present invention provides a method for delaying discharge using any of the isothermal cryogenic liquid fuel storage tanks in the first aspect, which is specifically as follows:

[0016] Open the filling valve, fill the cryogenic liquid fuel into the inner tank through the filling pipe until the liquid level is flush with the end of the filling pipe, and achieve liquid seal for the liquid fuel through the filling pipe;

[0017] During storage, due to the temperature difference between the cryogenic liquid fuel in the tank and the external environment, there is still a continuous heat absorption process under the action of the thermal insulation layer, resulting in the cryogenic liquid fuel in the tank absorbing heat and warming up to become gaseous fuel. At the same time, since the liquid filling rate of the liquid fuel filling is less than 1, there is a gas-liquid stratification phenomenon in the tank. During the heat absorption process between the cryogenic liquid fuel in the tank and the external environment, due to the lower thermal conductivity of the fuel in the upper gas phase region of the tank compared to the lower liquid phase side, the heat transfer thermal resistance between the gas and liquid phases is relatively large, and local overheating is likely to occur in the gas phase. By arranging a wire mesh with good thermal conductivity in the tank, the heat transfer thermal resistance in the gas phase region and at the gas-liquid interface is reduced, the temperature stratification phenomenon is inhibited, thereby avoiding the phenomenon of local rapid temperature rise and pressure increase in the gas phase due to large thermal resistance and small heat capacity, and avoiding the overpressure relief phenomenon of the isothermal cryogenic liquid fuel storage tank at a relatively low average temperature due to local pressure increase, thereby delaying the overpressure relief process, increasing the safe storage time of the cryogenic fuel storage tank, and achieving the purpose of long-term storage. By applying a radiation cooling coating on the outer wall of the outer shell, on the basis of the original heat balance, the external heat dissipation power of the outer shell surface is increased, thereby reducing the heat absorption power in the tank, so that under the condition of the same heat absorption amount, the heat absorption time is extended, thereby delaying the overpressure relief process of the isothermal cryogenic liquid fuel storage tank; since the radiation cooling power of the upper surface gas phase region is significantly greater than that of the lower surface, it further inhibits the phenomenon of local temperature rise and pressure increase in the gas phase on the upper surface, further reducing the gas-liquid temperature difference, improving the isothermal property, and thus extending the safe storage time; during the process of the cryogenic liquid fuel in the tank absorbing heat and warming up to become gaseous fuel, the pressure in the tank gradually increases. When the reading of the barometer exceeds the relief pressure, the relief valve is opened to allow some gas to be discharged to the outside through the relief pipe.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention uses an interpolated wire mesh to promote the diffusion of heat in the gas phase region of the cryogenic liquid storage tank to the liquid phase region, thereby inhibiting the premature overpressure relief of the system caused by the local rapid temperature rise and pressure increase in the gas phase region with slower heat transfer, and extending the storage time of the liquid fuel.

[0020] (2) The present invention adopts passive radiation cooling, thereby effectively reducing the net heat absorption of the tank body itself, and further delaying the overpressure relief caused by the heat absorption, temperature rise and pressure increase of the cryogenic liquid storage tank.

[0021] (3) The present invention adopts a passive method, with a simple structure, low energy consumption and low cost. At the same time, the wire mesh uses a material with a smaller density, which can reduce the system weight, facilitate the installation, maintenance and transportation of the storage system. Description of the Drawings

[0022] Figure 1 is a schematic structural diagram of a device of an isothermal cryogenic liquid fuel storage tank;

[0023] Figure 2 It is a graph showing the variation of the temperatures of the gas-liquid two-phase measuring points with or without wire mesh inside a spherical liquid hydrogen storage tank over time;

[0024] Figure 3 It is a graph showing the variation of the internal pressure inside a spherical liquid hydrogen storage tank with or without wire mesh over time;

[0025] In the figure: radiation cooling coating 1, outer shell 2, vacuum insulation layer 3, reflective layer 4, thermal insulation layer 5, inner tank 6, inner tank lining 7, inner tank support 8, wire mesh 9, filling pipe 10, filling pressure gauge 11, filling valve 12, exhaust pipe 13, barometer 14, relief pipe 15, relief valve 16, gas supply pipe 17, gas supply valve 18, liquid supply valve 19, liquid supply pipe 20. Specific embodiments

[0026] The present invention will be further described and explained below in conjunction with the accompanying drawings and specific embodiments. The technical features of each embodiment in the present invention can be combined correspondingly without conflict.

[0027] As Figure 1 shown, a temperature-equalizing type cryogenic liquid fuel storage tank provided by the present invention is shown. In actual use, the placement mode of the temperature-equalizing type cryogenic liquid fuel storage tank can be vertical or horizontal, and the model can be a C-type storage tank, a Dewar tank or a spherical tank. The device mainly includes an outer shell 2, an inner tank 6, a filling pipe 10, an exhaust pipe 13 and a liquid supply pipe 20. The structures and connection modes of each component will be specifically described below.

[0028] In the device of the present invention, an inner tank 6 is sleeved inside the outer shell 2, and the two are fixedly connected through a plurality of inner tank supports 8. The area between the outer shell 2 and the inner tank 6 forms a vacuum insulation layer 3. A thermal insulation layer 5 with a certain thickness is laid on the outer wall of the inner tank 6, and a reflective layer 4 is laid on the outside of the thermal insulation layer 5. An inner tank lining 7 is laid on the inner wall of the inner tank 6, and a wire mesh 9 is filled inside the inner tank 6. A radiation cooling coating 1 is applied to the outer wall of the outer shell 2.

[0029] In actual use, the thermal insulation layer 5 is composed of multiple layers of thermal insulation materials, and the thermal insulation materials include one or a combination of glass fiber, aluminum silicate rock wool, glass wool and aerogel materials. The material of the reflective layer 4 is aluminum foil or tin foil, and its main function is to reflect radiant heat dissipation. The material of the inner tank lining 7 is aluminum or the like, and its main function is to prevent cryogenic liquid fuel from leaking through the inner tank. The shape of the wire mesh 9 can be a herringbone mesh, a Z-shaped mesh, a diamond mesh, a horseshoe mesh, a chain mesh, an eyeglass mesh, a chain plate mesh or a spherical mesh, etc. The material of the wire mesh 9 can be foam metal, carbon fiber, aluminum or steel, etc.

[0030] In the device of the present invention, one end of the filling pipe 10 extends into the top inside the inner tank 6, and the other end is located outside the outer housing 2 and is respectively connected to the filling pressure gauge 11 and the filling valve 12. One end of the exhaust pipe 13 extends into the top inside the inner tank 6, and the other end is located outside the outer housing 2 and is respectively connected to the barometer 14 and the first port of the three-way pipe. The second port of the three-way pipe is connected to the discharge pipe 15 and the discharge valve 16, and the third port is connected to the gas supply pipe 17 and the gas supply valve 18. One end of the liquid supply pipe 20 extends into the bottom inside the inner tank 6, and the other end is located outside the outer housing 2 and is connected to the liquid supply valve 19.

[0031] During actual use, a part of the pipe body of the filling pipe 10 can be embedded in the inner tank support 8 at the top, so as to achieve fixation with the storage tank. The exhaust pipe 13 and the liquid supply pipe 20 can respectively embed a part of their pipe bodies in the inner tank support 8 on the side, so as to achieve fixation with the storage tank. Since a part of the gas phase area needs to be left inside the tank body of the present invention, the end of the filling pipe 10 extending into the inner tank 6 can protrude from the inner tank lining 7, so that the liquid inside the inner tank 6 cannot be completely filled.

[0032] The method for delaying the discharge of the above-mentioned isothermal low-temperature liquid fuel storage tank is as follows:

[0033] Open the filling valve 12, and fill the low-temperature liquid fuel into the inner tank 6 through the filling pipe 10 until the liquid level is flush with the end of the filling pipe 10, and achieve liquid sealing of the liquid fuel through the filling pipe 10. When it is necessary to transport the liquid-phase fuel outwards, open the liquid supply valve 19 to make the liquid-phase fuel flow out from the liquid supply pipe 20; when it is necessary to transport the gas-phase fuel outwards, open the gas supply valve 18 to make the gas-phase fuel flow out from the gas supply pipe 17.

[0034] During storage, due to the temperature difference between the cryogenic liquid fuel in the tank and the external environment, there is still a continuous heat absorption process under the action of the thermal insulation layer 5, resulting in the cryogenic liquid fuel in the tank absorbing heat and warming up to become gaseous fuel. At the same time, since the filling rate of the liquid fuel filling is less than 1, there is a gas-liquid stratification phenomenon in the tank. During the heat absorption process between the cryogenic liquid fuel in the tank and the external environment, due to the lower thermal conductivity of the fuel in the upper gas phase region of the tank compared to the lower liquid phase side, the heat transfer thermal resistance between the gas and liquid phases is relatively large, and local overheating is likely to occur in the gas phase. Through the wire mesh 9 with good thermal conductivity set in the tank, the heat transfer thermal resistance in the gas phase region and at the gas-liquid interface is reduced, and the temperature stratification phenomenon is inhibited, thereby avoiding the phenomenon of local rapid temperature rise and pressure increase in the gas phase due to the large thermal resistance and small heat capacity, and avoiding the overpressure relief phenomenon of the isothermal cryogenic liquid fuel storage tank at a lower average temperature due to the local pressure increase, thereby delaying the overpressure relief process, increasing the safe storage time of the cryogenic fuel storage tank, and achieving the purpose of long-term storage. By applying the radiative cooling coating 1 on the outer wall of the outer shell 2, on the basis of the original thermal balance, the external heat dissipation power of the surface of the outer shell 2 is increased, thereby reducing the heat absorption power in the tank, so that under the condition of the same heat absorption amount, the heat absorption time is extended, thereby delaying the overpressure relief process of the isothermal cryogenic liquid fuel storage tank. Since the radiative cooling power of the upper surface gas phase region is significantly greater than that of the lower surface, the phenomenon of local temperature rise and pressure increase of the gas phase on the upper surface is further inhibited, the gas-liquid temperature difference is further reduced, the isothermal property is improved, and the safe storage time is extended. During the process of the cryogenic liquid fuel in the tank absorbing heat and warming up to become gaseous fuel, the pressure in the tank gradually increases. When the reading of the barometer 14 exceeds the relief pressure, the relief valve 16 is opened to allow some gas to be discharged to the outside through the relief pipe 15.

[0035] The following combines specific embodiments to further clarify the specific applications and technical effects of the above-mentioned isothermal cryogenic liquid fuel storage tank device and the method for delaying relief. It should be noted that the following embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0036] Embodiment

[0037] This embodiment takes a spherical liquid hydrogen storage tank with a diameter of 4.89 m 3 as an example. The filling rate of this liquid hydrogen storage tank is 83%, and the boundary heat leakage heat flux density is 3.5 W / m 2 , which is evenly distributed on the outer wall of the storage tank. When no wire mesh is arranged in the storage tank, the temperature of the hydrogen at the internal gas-liquid two-phase measurement points is measured by using a resistive temperature sensor, and the pressure in the tank is measured by using a pressure sensor. The results can be obtained as shown in Figure 2 and Figure 3Curves of the temperature of the gas-liquid two-phase and the pressure inside the tank changing with time as shown by the solid line. When the stainless steel human-shaped wire mesh is fully arranged inside the storage tank, assuming that the heat flux density between the two measurement points of the gas-liquid two-phase remains unchanged, the temperature difference between the gas-liquid two-phase after arranging the wire mesh can be calculated. Then, based on the energy conservation between the two phases, the temperatures of the gas-liquid two-phase measurement points can be calculated. The obtained gas-liquid two-phase temperatures are as shown by Figure 2 the dashed line. The calculation formula is as follows:

[0038]

[0039] m l Cp l (T l,a )T l,a +m v Cp v (T v,a )T v,a =m l Cp l (T l,b )T l,b +m v Cp v (T v,b )T v,b (2)

[0040] Among them, q vl represents the heat flux density between the two measurement points of the gas-liquid two-phase, λ a represents the thermal conductivity between the two measurement points without the wire mesh, T v,a represents the temperature of the gas-phase measurement point without the wire mesh, T l,a represents the temperature of the liquid-phase measurement point without the wire mesh, L represents the distance between the gas-liquid two-phase measurement points, λ b represents the thermal conductivity between the two measurement points after adding the wire mesh, which can be obtained by the area weighting method, T v,b represents the temperature of the gas-phase measurement point after adding the wire mesh, T l,b represents the temperature of the liquid-phase measurement point after adding the wire mesh, m l represents the mass of liquid hydrogen in the storage tank, m v represents the mass of hydrogen in the storage tank, Cp l (T l,a ) represents the specific heat of liquid hydrogen at the temperature of T l,a , Cp v (T v,a ) represents the specific heat of hydrogen at the temperature of T v,a .

[0041] For a closed storage tank, in the unsteady state stage where the temperature difference between the gas and liquid phases gradually increases, it can be assumed that the evaporation rate of liquid hydrogen is zero. In this case, the gas phase density should remain constant. During the temperature rise, the pressure should increase accordingly. By referring to the physical property table of hydrogen, the corresponding storage tank pressure can be obtained. In the steady state stage where the temperature difference between the gas and liquid phases remains almost constant, it can be assumed that all the boundary heat flux is used for evaporating liquid hydrogen. The density increment of gaseous hydrogen completely depends on the evaporation rate, and the temperature remains constant. By referring to the physical property table of hydrogen, the corresponding storage tank pressure can be obtained. The calculated tank pressure is as shown by Figure 3 the dashed line, and the calculation formula is as follows:

[0042] q b A = Δm × ΔH vap (3)

[0043]

[0044] Among them, q b represents the boundary heat flux density, A represents the surface area of the storage tank, Δm represents the evaporation rate in the steady state stage, and ΔH vap represents the latent heat of vaporization of liquid hydrogen, and Δρ v represents the density increment of the gas phase in the steady state stage, and V v represents the gas phase volume.

[0045] From Figure 2 the results, it can be found that without adding wire mesh, the temperature difference between the gas and liquid phase measurement points in the steady state stage can reach up to \alphaK. After adding wire mesh, the temperature difference significantly decreases, only about 3K. This shows that the arrangement of wire mesh can effectively inhibit the temperature stratification phenomenon of cryogenic liquid storage tanks and increase the temperature uniformity of the storage tank. From Figure 3 the results, it can be found that without arranging wire mesh, the pressure in the tank increased by about 150 kPa within 12 hours. After arranging wire mesh, the pressure in the tank only increased by about 90 kPa in the same time. This shows that the arrangement of wire mesh can inhibit and delay the occurrence of overpressure relief, reduce the loss of liquid fuel, and achieve the purpose of long-term storage.

[0046] The present invention utilizes a radiation cooling layer to reduce the net heat absorption of the system itself; uses an interpolated wire mesh to improve heat transfer in the tank and inhibit the premature overpressure relief caused by the rapid temperature rise and pressure increase of the gas phase region with slow heat transfer and low specific heat, reducing the emission loss and achieving the purpose of long-term storage of liquid fuel. Compared with other technologies for extending the storage time, the present invention has the advantages of low energy consumption, simple structure, and low cost.

[0047] The above-described embodiments are only a preferred solution of the present invention, but they are not intended to limit the present invention. Those of ordinary skill in the relevant technical fields can still make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by adopting equivalent replacement or equivalent transformation methods fall within the protection scope of the present invention.

Claims

1. A temperature-equalizing type cryogenic liquid fuel storage tank, characterized in that, It includes an outer shell (2), an inner tank (6), a filling pipe (10), an exhaust pipe (13) and a liquid supply pipe (20); The outer shell (2) is coaxially sleeved with the inner tank (6) and connected by an inner tank support (8). The area between the outer shell (2) and the inner tank (6) forms a vacuum insulation layer (3); A thermal insulation layer (5) is laid on the outer wall of the inner tank (6), and a reflective layer (4) is laid on the outside of the thermal insulation layer (5); An inner tank lining (7) is laid on the inner wall of the inner tank (6), and a wire mesh (9) is filled inside the inner tank (6); A radiation cooling coating (1) is applied on the outer wall of the outer shell (2); One end of the filling pipe (10) extends into the top inside the inner tank (6), and the other end is located outside the outer shell (2) and is respectively connected to a filling pressure gauge (11) and a filling valve (12); One end of the exhaust pipe (13) extends into the top inside the inner tank (6), and the other end is located outside the outer shell (2) and is respectively connected to a barometer (14) and the first port of a three-way pipe; The second port of the three-way pipe is connected to a discharge pipe (15) and a discharge valve (16), and the third port is connected to a gas supply pipe (17) and a gas supply valve (18); One end of the liquid supply pipe (20) extends into the bottom inside the inner tank (6), and the other end is located outside the outer shell (2) and is connected to a liquid supply valve (19).

2. The isothermal low-temperature liquid fuel storage tank according to claim 1, wherein A part of the filling pipe (10) is embedded in the top inner tank support (8) for fixation, and the exhaust pipe (13) and the liquid supply pipe (20) are respectively partially embedded in the side inner tank supports (8) for fixation.

3. A temperature-equalizing type cryogenic liquid fuel storage tank according to claim 1, characterized in that, The thermal insulation layer (5) is composed of multiple layers of thermal insulation materials, and the thermal insulation materials include one or a combination of glass fiber, aluminum silicate rock wool, glass wool and aerogel materials.

4. A temperature-equalizing type cryogenic liquid fuel storage tank according to claim 1, characterized in that, The placement method of the isothermal low-temperature liquid fuel storage tank is vertical or horizontal, and the model is a C-type storage tank, a Dewar tank or a spherical tank.

5. A temperature-equalizing type cryogenic liquid fuel storage tank according to claim 1, characterized in that, The shape of the wire mesh (9) includes a herringbone mesh, a Z-shaped mesh, a diamond mesh, a horseshoe mesh, a chain mesh, an eyeglass mesh, a chain plate mesh or a spherical mesh.

6. The isothermal low-temperature liquid fuel storage tank according to claim 1, characterized in that, The material of the wire mesh (9) is foam metal, carbon fiber, aluminum or steel.

7. A temperature-equalizing type cryogenic liquid fuel storage tank according to claim 1, characterized in that, The end of the filling pipe (10) extending into the inner tank (6) protrudes from the inner tank lining (7), so that the liquid inside the inner tank (6) cannot be completely filled.

8. A method for delaying the discharge of a temperature-equalizing type cryogenic liquid fuel storage tank according to any one of claims 1 to 7, characterized in that, Specifically as follows: During storage, due to the temperature difference between the cryogenic liquid fuel in the tank and the external environment, there is still a continuous heat absorption process under the action of the thermal insulation layer (5), resulting in the cryogenic liquid fuel in the tank absorbing heat and warming up to become gaseous fuel. At the same time, since the liquid filling rate of the liquid fuel filling is less than 1, there is a gas-liquid stratification phenomenon in the tank. During the heat absorption process between the cryogenic liquid fuel in the tank and the external environment, due to the lower thermal conductivity of the fuel in the upper gas phase region of the tank compared to the lower liquid phase side, the heat transfer resistance between the gas and liquid phases is relatively large, and local overheating is likely to occur in the gas phase. By means of the wire mesh (9) with good thermal conductivity arranged in the tank, the heat transfer resistance in the gas phase region and at the gas-liquid interface is reduced, and the temperature stratification phenomenon is inhibited, thereby avoiding the phenomenon of local rapid temperature rise and pressure increase in the gas phase due to the large heat transfer resistance and small heat capacity in the gas phase region, and avoiding the overpressure relief phenomenon of the isothermal cryogenic liquid fuel storage tank at a relatively low average temperature due to local pressure increase, thus delaying the overpressure relief process, increasing the safe storage time of the cryogenic fuel storage tank, and achieving the purpose of long-term storage. By means of the radiation cooling coating (1) coated on the outer wall of the outer shell (2), on the basis of the original thermal balance, the external heat dissipation power of the surface of the outer shell (2) is increased, thereby reducing the heat absorption power in the tank, so that under the condition of the same heat absorption amount, the heat absorption time is extended, thus delaying the overpressure relief process of the isothermal cryogenic liquid fuel storage tank. Since the radiation cooling power of the upper surface gas phase region is significantly greater than that of the lower surface, the phenomenon of local temperature rise and pressure increase in the gas phase of the upper surface is further inhibited, the gas-liquid temperature difference is further reduced, the isothermal property is improved, and thus the safe storage time is extended. During the process of the cryogenic liquid fuel in the tank absorbing heat and warming up to become gaseous fuel, the pressure in the tank gradually increases. When the reading of the barometer (14) exceeds the relief pressure, the relief valve (16) is opened to allow some gas to be discharged to the outside through the relief pipe (15).

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