LNG film tank cold insulation calculation and daily evaporation rate prediction system

Abstract

The application discloses a LNG film tank cold insulation calculation and daily evaporation rate prediction system, which comprises a calculation platform input module, a calculation module and a data visualization module; wherein the calculation platform input module is responsible for receiving and arranging various input parameters and accurately transmitting the same to the calculation module; the calculation module performs operation processing based on the received input parameters, and outputs two core parameters of a total heat quantity of the LNG film tank and daily evaporation loss of the LNG film tank; meanwhile, other result parameters generated in the operation process are synchronously transmitted to the data visualization module in an intuitive presentation form, so that workers can quickly check, verify and analyze various result data. The application can comprehensively consider the cold insulation structure parameters of the film tank, environmental conditions and physical properties of liquid natural gas, accurately predict the daily evaporation rate of the tank body, ensure that the daily evaporation rate meets engineering requirements, and thus provide scientific guidance for structure design of the LNG film tank.

Description

Technical Field

[0001] This invention relates to the field of thermal insulation storage technology for liquefied natural gas membrane tanks, and particularly to a system for calculating the cold insulation of LNG membrane tanks and predicting the daily evaporation rate. Background Technology

[0002] In the storage and transportation of LNG, cold insulation technology is a key factor in ensuring the safe and efficient storage and transportation of liquefied natural gas. LNG membrane tanks, as an efficient storage method, are widely used in LNG storage and transportation due to their superior insulation performance and structural safety. Membrane tanks employ advanced membrane insulation material design, effectively reducing evaporation losses of liquefied natural gas and ensuring the stability of the storage process.

[0003] The temperature of liquefied natural gas stored in existing LNG membrane tanks is -162℃. The temperature difference between cryogenic LNG and the external environment is as high as nearly 190℃. The LNG storage liquid will transfer heat to the outside world through the tank, causing LNG to absorb heat and evaporate. On the one hand, the evaporation of LNG will lead to direct economic losses. On the other hand, a large amount of LNG evaporates into BOG (Boil-Off Gas), which will increase the pressure of the storage tank, increase the safety risks, and increase the handling cost of BOG.

[0004] Daily evaporation rate is an important indicator for evaluating the rationality of membrane tank structural design. In engineering, it is required that the daily evaporation loss of the storage tank is no more than 0.05%. The LNG membrane tank insulation structure is an important component to ensure that the daily evaporation loss of the storage tank is no more than 0.05%. However, in the current design of LNG membrane tank insulation structures, heat transfer calculation and insulation performance evaluation still face significant challenges.

[0005] A method for predicting LNG heat transfer phenomena and daily evaporation rate (BOR) in storage tanks, published in CN118313306A, neglects the contact thermal resistance between material interfaces to simplify the calculation process, leading to inaccurate prediction results. Contact thermal resistance refers to the additional resistance encountered by heat transfer at material interfaces due to factors such as surface unevenness, roughness, and microscopic gaps between materials. In the insulation structure of LNG membrane tanks, material interfaces exist between different insulation materials and between the insulation material and the tank structure. Contact thermal resistance has a significant impact on heat transfer at these interfaces. Because the contact thermal resistance is not considered, the existing method significantly overestimates the heat transferred from the environment to the LNG in the tank. This overestimation directly leads to a higher predicted BOR than the actual value. When designing based on a model that ignores contact thermal resistance, designers often choose excessively thick or high-performance insulation materials to achieve the target BOR, resulting in unnecessary increases in material costs.

[0006] Furthermore, existing design solutions often rely on experience. Designers primarily select insulation materials and determine cold-insulating structures based on their experience from similar past projects, lacking effective tools for comprehensive and accurate prediction and optimization of cold-insulating performance. This experience-based design approach struggles to handle LNG membrane tanks with varying operating conditions and structures, failing to fully consider the impact of complex factors on cold-insulating performance, potentially resulting in designs that do not achieve optimal performance.

[0007] Therefore, it is urgent to build an LNG membrane tank insulation calculation and daily evaporation rate prediction platform to reduce material and construction costs while ensuring that the project meets the insulation performance requirements, and to provide a theoretical basis for the design of LNG membrane tanks of different volumes in the future. Summary of the Invention

[0008] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide an LNG membrane tank insulation calculation and daily evaporation rate prediction system. This system can comprehensively consider the insulation structure parameters of the membrane tank, environmental conditions and physical properties of liquefied natural gas, accurately predict the daily evaporation rate of the tank, ensure that the daily evaporation rate meets the engineering requirements, and thus provide scientific guidance for the structural design of LNG membrane tanks.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A system for calculating the insulation of LNG membrane tanks and predicting the daily evaporation rate includes a calculation platform input module, a calculation module, and a data visualization module [111.1][author1.2]; The calculation platform input module is responsible for receiving and organizing various input parameters and accurately transmitting them to the calculation module. The calculation module performs calculations based on the received input parameters and outputs two core parameters: the total heat transferred into the LNG membrane tank and the daily evaporation loss of the LNG membrane tank. At the same time, it transmits other result parameters generated during the calculation process to the data visualization module in an intuitive form, making it convenient for staff to quickly view, verify and analyze various result data.

[0010] The computing platform input module includes: a basic environmental parameter module, a thin-film tank structure parameter configuration module, and a material thermal property configuration module, wherein... The basic environmental parameter module is used to input parameters such as ambient temperature setting, solar radiation intensity, and effective solar radiation time. The membrane tank structure parameter configuration module is used to input sidewall height parameters, sidewall inner diameter parameters, dome height parameters, tank bottom radius parameters, material layer quantity parameters, and material layer thickness parameters; The material thermal property configuration module is used to input the material's thermal conductivity, convective heat transfer coefficient, and interfacial contact thermal resistance.

[0011] The calculation module includes an initial parameter setting module, a dynamic parameter update module, a core heat transfer calculation module, a daily evaporation loss calculation module, and a calculation result management module; The initial parameter setting module provides all the basic parameters required for the core heat transfer calculation module to operate; the dynamic parameter update module corrects the basic parameters, and the corrected parameters are sent to the core heat transfer calculation module for accurate calculation of heat flow in various parts of the LNG membrane tank; the daily evaporation loss calculation module receives and integrates the output results of the core heat transfer calculation module, and based on these results, predicts the daily evaporation rate and outputs the predicted data; the calculation result management module judges the predicted data of the daily evaporation loss calculation module, and automatically triggers an early warning when the predicted result exceeds the preset standard. The initial parameter setting module is used to establish a three-dimensional structural feature database of the thin film tank and configure multi-level calculation boundary conditions such as ambient temperature range, material thermal conductivity, and contact thermal resistance, providing users with a standard for parameter input. The dynamic parameter update module is used to store the LNG film tank three-dimensional structural feature database, ambient temperature range, material thermal conductivity, contact thermal resistance and other multi-level calculation boundary conditions change parameters, to ensure real-time response to parameter modifications during the calculation process; The core heat transfer calculation module is based on the thermal resistance network diagram to analyze the heat transfer mode of the five major parts that make up the thin film tank, and constructs heat transfer models of the side wall, hot corner protection, tank bottom, tank top and solid components to accurately calculate the heat flow of each part. The daily evaporation loss calculation module is used to integrate heat flow transfer and solar radiation compensation in various parts, apply the LNG property conversion model, and combine parameters such as latent heat of vaporization and density volume to achieve accurate prediction of daily evaporation rate (BOG) and evaluation of cold preservation performance. The calculation result management module is used to judge the daily evaporation rate index and issue early warnings for exceeding the daily evaporation rate standard.

[0012] The initial parameter module includes a basic environmental parameter submodule, a thin-film tank structural parameter submodule, and a material thermal property parameter submodule, wherein, The basic environmental parameters submodule is used to store data, including ambient temperature, solar radiation intensity, and effective solar radiation time. The membrane tank structure parameter submodule is used to store the LNG membrane tank three-dimensional storage tank geometric feature database, including data on the inner diameter of the membrane tank inscribed circle, the tank wall height, the outer diameter of the inner diameter of the membrane tank inscribed circle, the dome height, and the thickness of the layered insulation material, to construct a complete membrane tank spatial structure model; The material thermal characteristics submodule is used to store the thermophysical parameters of the layered insulation material, including the thermal conductivity of the material, the contact thermal resistance between two adjacent layers of material, and the convective heat transfer coefficient of the space.

[0013] The dynamic parameter update module includes: a basic environmental parameter submodule, a thin-film tank structure parameter submodule, and a material thermal property parameter submodule. Similar to the initial parameter module, the dynamic parameter update module achieves dynamic adjustment of parameters through real-time session state management technology.

[0014] The core heat transfer calculation module includes sub-modules for calculating sidewall heat flow, thermal corner protection system heat flow, bottom of the thin-film tank, dome of the thin-film tank, solid components of the thin-film tank, and solar radiation; among them; The sidewall heat flow calculation submodule is based on a multi-layer cylindrical wall heat transfer model. By analyzing a one-dimensional thermal resistance network diagram, it accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the inner wall of the membrane, as well as the natural convection heat flow between the external environment and the air outside the membrane tank. Finally, it outputs the total heat flow transferred through the sidewall region. The heat flow calculation submodule of the hot corner protection system, based on the multi-layer cylindrical wall heat transfer model, analyzes the 5m hot corner protection area at the bottom of the tank wall to establish a thermal resistance network diagram, accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the hot corner protection system, the natural convection heat flow between the external environment and the hot corner protection system, and finally outputs the total heat flow transferred through the hot corner protection system. The heat flow calculation submodule at the bottom of the membrane tank is based on a multi-layer planar wall heat transfer model. It analyzes the one-dimensional network heat map at the bottom of the tank, accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the inner wall of the membrane tank bottom, and finally outputs the total heat flow transferred through the bottom of the membrane tank. The membrane tank dome heat flow calculation submodule establishes an arched multi-layer heat transfer model to accurately calculate the heat flow caused by the temperature difference between the ambient temperature and the inner wall of the membrane dome, the heat flow caused by the natural convection heat transfer between the external environment and the outer wall of the membrane tank dome, and the heat flow caused by the natural convection heat transfer between the inner wall of the membrane tank dome and the gas phase space inside the tank. Finally, it outputs the total heat flow transferred through the dome region. The heat flow calculation submodule for solid components of the membrane tank accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the internal temperature of the membrane tank by analyzing the bottom one-dimensional network thermal diagram of the solid components, and finally outputs the total heat flow transferred through the solid components. The solar radiation calculation submodule is used to calculate the heat flow caused by solar radiation heat transfer to the outer wall of the thin film tank. Since the bottom of the thin film tank is not subject to solar radiation, the calculation area includes three parts: the side wall of the thin film tank, the thermal corner protection system, and the dome of the thin film tank. Finally, the total heat flow transferred by thermal radiation is output.

[0015] The daily evaporation loss calculation module includes: a total heat integration calculation submodule, an LNG volume and filling rate calculation submodule, and a daily evaporation rate calculation submodule, wherein... The total heat integration calculation submodule is used to integrate the heat flow data of the five submodules in the core heat transfer calculation module in real time; The LNG volume and filling rate calculation submodule is used to calculate the LNG volume and the LNG filling rate in the membrane tank by combining the membrane tank structure parameters in the dynamic parameter update module. The daily evaporation rate calculation submodule integrates parameters such as latent heat of vaporization and effective volume to convert total heat flow into daily evaporation loss, and finally outputs a BOG value accurate to 0.000001%, forming the core evaluation index of cold insulation performance.

[0016] The data visualization module includes: a real-time calculation result submodule, a thermodynamic distribution visualization submodule, a thin-film tank structure visualization module, and a technical description submodule, wherein... The real-time calculation results module is used to display the ambient temperature, total heat flow, and daily evaporation rate. The thermodynamic distribution visualization submodule displays the heat flow and percentage of each part in tabular form, with the percentage of heat flow clearly visualized using a pie chart. The membrane tank structure visualization module constructs a three-dimensional cross-sectional view of the membrane tank structure on the ground coordinate system, performs spatial mapping of heat flow distribution on the cross-sectional view, and labels the heat flow of each part; The technical description submodule is used to annotate the structure of the thin-film tank, and to explain the thermal corner protection system and the heat transfer characteristics of each part.

[0017] The beneficial effects of this invention are: The LNG membrane tank insulation calculation and daily evaporation rate prediction platform provided by this invention can accurately predict insulation performance. The comprehensive parameters included in the calculation platform's input module allow designers to dynamically simulate and evaluate the insulation performance of membrane tanks with different materials and structures under all-season (four seasons) and all-weather (24 hours) conditions, thereby effectively reducing the time cost required in actual testing. Secondly, the platform has a built-in dynamic parameter setting module that supports real-time optimization and adjustment of insulation structure parameters and provides rapid response, avoiding the waste of manpower and costs caused by hardware adjustments during the engineering implementation phase. Finally, the platform also provides technical developers with the ability to quickly iterate and test new volume and structure membrane tanks, greatly improving R&D efficiency and accelerating product optimization and innovation. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the design process of the LNG membrane tank cold insulation calculation and daily evaporation rate prediction platform of the present invention.

[0019] Figure 2 This is a schematic diagram showing the LNG thin-film tank structure and the corresponding calculation area division of the core heat transfer calculation module in the disclosed embodiment of the present invention.

[0020] Figure 3 This is a thermal resistance network diagram of convective heat transfer and thermal conduction during the heat transfer process of the LNG film tank sidewall, thermal corner protection system, bottom, dome, and solid components in the embodiments disclosed in this invention.

[0021] Figure 4 The input modules of the computing platform of this invention include the basic ambient temperature, thin-film tank structural parameters, and material thermal property parameters, as well as the parameters set in this embodiment.

[0022] Figure 5 This is a schematic diagram of the calculation results of each sub-module of the data visualization module in the embodiments disclosed in this invention.

[0023] Figure 6 This is a schematic diagram of the overall interface layout of the LNG film tank cold insulation calculation and daily evaporation rate prediction platform in an embodiment of the present invention. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings.

[0025] To facilitate understanding of the embodiments of the present invention, the following will be described in conjunction with the accompanying drawings. Figures 1 to 6 The following explanation is based on specific embodiments, and the accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0026] This example implementation provides a system for calculating the cold insulation of LNG membrane tanks and predicting the daily evaporation rate, such as... Figure 1 As shown, the system includes: a computing platform input module, a computing module, and a data visualization module.

[0027] The operation process of the LNG membrane tank insulation calculation and daily evaporation rate prediction platform includes the following steps: S1: Start the platform. The system will automatically enter the input module of the calculation platform. This module loads the initial settings by default. The initial settings include the basic ambient temperature, the configuration of the thin film tank structure parameters, and the configuration of the material thermal properties, which provide the basic conditions for subsequent calculations.

[0028] S2: Based on actual engineering design requirements, technicians can dynamically adjust the initial parameters loaded in S1 through the built-in dynamic parameter setting submodule in the calculation module, flexibly adapting to different working conditions and design standards, and ensuring the accuracy of the calculation parameters. S3: Within the calculation module, the core heat transfer calculation submodule completes the accurate calculation of heat flow in various parts of the LNG membrane tank based on the parameters adjusted by the dynamic parameter setting submodule; the daily evaporation loss calculation module receives and integrates the output results of the core heat transfer calculation module, completes the prediction of the daily evaporation rate based on the heat flow calculation results, and outputs the corresponding prediction data; at the same time, the calculation result management module judges the prediction data of the daily evaporation loss calculation module, and automatically triggers an early warning reminder when the prediction result exceeds the preset standard; S4: The data visualization module receives all the result data output by the calculation module, performs visualization processing on it, and provides data support to technical personnel in an intuitive and clear presentation form, which facilitates further analysis and design optimization.

[0029] The basic environmental parameters in S1 include: ambient temperature setting, solar radiation intensity setting, and effective solar radiation time; the membrane tank structural parameters include: sidewall height parameter, sidewall inner diameter parameter, dome height parameter, tank bottom radius parameter, material layer quantity parameter, and material layer thickness parameter; the material thermal property parameters include: material thermal conductivity parameter, convective heat transfer parameter, and layer interface contact parameter.

[0030] In S2, the platform allows technicians to dynamically modify various initial parameters according to specific engineering design requirements, flexibly adjust key parameters related to the heat transfer performance and cold insulation effect of the LNG membrane tank, and receive changes in input parameters in real time.

[0031] The calculations in S3 follow the following method: First, the heat transfer mechanism of the membrane tank is analyzed. In this embodiment, the average annual temperature of the region where the LNG membrane tank is located is 22.7℃, the extreme maximum temperature is 37.9℃, the extreme minimum temperature is 1.5℃, the annual average maximum temperature is 23.4℃, and the annual average minimum temperature is 22.0℃. The LNG storage temperature is -162℃, which is even much lower than the extreme minimum temperature. There is heat conduction caused by the temperature difference between the ambient temperature and the inner wall of the membrane tank. At the same time, the heat radiation received by the outer surface of the tank and the natural convection heat transfer of the ambient air need to be considered. The local solar radiation is 1120W / m². 2 .

[0032] This embodiment takes into account the actual engineering application situation, mainly because different materials have different surface roughness, and there are gaps between the contact parts. Heat conduction also needs to take into account the contact thermal resistance at the interface.

[0033] In this embodiment, the heat transfer methods of the LNG membrane tank include: heat conduction, heat convection, and heat radiation. It can be seen that the entire heat exchange process includes almost all heat transfer forms. This embodiment makes the following assumptions: First, under a specific working condition, the sun's radiation and the atmospheric temperature are constant and do not change with time and location. Secondly, for the tank body, the thickness of each part is uniform, and local thickness variations are ignored; The volume of the third tank does not change with temperature; that is, the volume is constant. The materials in each layer of the fourth tank are isotropic, meaning that the thermal conductivity of the materials does not change with temperature. The fifth heat transfer only follows a one-dimensional steady-state radial conduction, without considering the axial temperature gradient.

[0034] Based on the above assumptions, the heat transfer model of this embodiment is established as follows: For heat conduction: ; For convective heat transfer: ; In the formula The heat flux density for thermal conduction. The heat flux density for convective heat transfer is the heat flow rate per unit area. W / m 2 ; Temperature of the outer wall of the tank, in units K ; Temperature of the inner wall of the tank, same as LNG temperature, unit: K , Temperature of the hot air outside the tank (ambient temperature), unit K ; The convective heat transfer coefficient is expressed in units of... W / (m 2 ·K) , Heat flow is the amount of heat passing through a given area per unit time, which is the heat flux density multiplied by the given area, and its unit is W. From the heat flux density formula above, the expressions for the heat flow rate from the external environment to the tank under heat conduction and convection heat transfer can be derived as follows: For heat conduction: For convective heat transfer: In the formula, A is the heat transfer surface area, in meters. The heat flow expression can be rewritten in temperature and pressure form: For heat conduction: For convective heat transfer: Add the two equations together and eliminate the temperature. get: The common heat flow of both heat conduction and convection heat transfer: The heat flow expression can also be rewritten as: In the formula k The average heat transfer coefficient is expressed as: The form of the heat flow expression is similar to Ohm's law in electricity. In comparison, it is not difficult to see It has a similar function to a resistor, and... The thermal resistance per unit area in a heat transfer process is called the thermal resistance of the heat transfer process. What are the components of the thermal resistance in a heat transfer process? , These are the thermal resistances that constitute each component.

[0035] The heat conduction process considers contact thermal resistance, and the contact thermal resistance per unit area is denoted as... R The unit is The thermal resistance per unit area during the heat transfer process is determined by , and R The total heat flow from the two stages of convection and conduction is: When an LNG membrane tank is exposed to the Earth's surface, a portion of its area will inevitably be exposed to solar radiation. Some of the heat projected onto the outer surface of the membrane tank is reflected, while the remainder is absorbed by the outer wall surface of the membrane tank. This causes the temperature of the outer wall surface to be higher than when there is no solar radiation, i.e., higher than the temperature of the air. At the same time, some of the heat absorbed by the outer wall surface will also be dissipated into the air. Establish a heat balance equation on the outer wall of the thin-film tank: By simplifying the heat balance equation, we can obtain: In the formula The absorption coefficient of the outer wall surface material is given. The concrete reflectance coefficient is 0.95, which means the absorption coefficient is 0.05. The average heat transfer coefficient, The temperature rise on the outer surface of the thin-film tank is due to solar radiation. The convective heat transfer coefficient between the outer wall of the thin-film tank and the air; The solar radiative heat flux is obtained through the heat balance equation: The effective solar radiation duration during the day is approximately 6 to 12 hours, depending on the season and geographical location. For example, in summer or in areas near the equator, solar radiation may last for about 12 hours, while it may be shorter in winter or at higher latitudes. This example assumes that the effective solar radiation during the day accounts for a certain percentage of the 24-hour period. If the effective solar radiation time is 6 hours, That is, 0.25; Therefore, the heat flux of solar thermal radiation after considering the effective radiation time is: ; The core heat transfer calculation module in the calculation module includes: a submodule for calculating the heat flow of the thin-film tank sidewall, a submodule for calculating the heat flow of the thermal corner protection system, a submodule for calculating the heat flow of the thin-film tank bottom, a submodule for calculating the heat flow of the thin-film tank dome, a submodule for calculating the heat flow of the solid components of the thin-film tank, and a submodule for calculating solar radiation. These submodules work together to calculate the heat flow of each heat transfer channel, specifically five heat transfer channels, as shown in the attached diagram. Figure 2 The diagram shows five heat transfer channels. ① represents heat transfer through the sidewall, corresponding to the sidewall heat flow calculation submodule of the thin-film tank; ② represents heat transfer through the thermal corner protection system, corresponding to the thermal corner protection system heat flow calculation submodule; ③ represents heat transfer through the tank bottom, corresponding to the bottom heat flow calculation submodule of the thin-film tank; ④ represents heat transfer through the dome, corresponding to the dome heat flow calculation submodule of the thin-film tank; and ⑤ represents heat transfer through solid components, corresponding to the solid component heat flow calculation submodule of the thin-film tank. The membrane tank sidewall heat flow calculation submodule is based on a multi-layer cylindrical wall heat transfer model. It analyzes the thermal resistance network diagram of convective heat transfer and heat conduction, accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the inner wall of the membrane, as well as the natural convective heat flow between the external environment and the air outside the membrane tank, and finally outputs the total heat flow transferred through the sidewall region. The heat flow calculation submodule of the hot corner protection system, based on the multi-layer cylindrical wall heat transfer model, analyzes the thermal resistance network diagram of convective heat transfer and heat conduction in the critical protection area of ​​the bottom 5m of the tank wall, accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the hot corner protection system, as well as the natural convective heat flow between the external environment and the hot corner protection system, and finally outputs the total heat flow transferred through the hot corner protection system. The membrane tank bottom heat flow calculation submodule, based on a multi-layer planar wall heat transfer model, analyzes the one-dimensional network heat map of convective heat transfer and heat conduction at the bottom of the tank, accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the inner wall of the membrane tank bottom, and finally outputs the total heat flow transferred through the bottom of the membrane tank. The membrane tank dome heat flow calculation submodule establishes an arched multi-layer heat transfer model, analyzes the one-dimensional network heat map of convection heat transfer and heat conduction at the dome, and accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the inner wall of the membrane dome, the heat flow caused by the natural convection heat transfer between the external environment and the outer wall of the membrane tank dome, and the heat flow caused by the natural convection heat transfer between the inner wall of the membrane tank dome and the gas phase space inside the tank. Finally, it outputs the total heat flow transferred through the side wall region. The heat flow calculation submodule for solid components of the membrane tank accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the internal temperature of the membrane tank by analyzing the bottom one-dimensional network thermal diagram of the solid components, and finally outputs the total heat flow transferred through the solid components. The solar radiation calculation submodule is used to calculate the heat flow caused by solar radiation heat transfer to the outer wall of the thin film tank. Since the bottom of the thin film tank is not subject to solar radiation, the calculation area includes three parts: the side wall of the thin film tank, the thermal corner protection system, and the dome of the thin film tank. Finally, the total heat flow transferred by thermal radiation is output.

[0036] The core heat transfer calculation submodule in S3 includes: Based on the heat transfer model established above, the core heat transfer sub-computation module in the calculation module follows the following approach: S31: Submodule for calculating heat flow through the sidewall of the membrane tank. This module calculates the heat flow transferred through the sidewall of the membrane tank and analyzes the thermal resistance network diagram (see attached). Figure 3 The first part of the text includes heat transfer in three stages: convection heat transfer, heat conduction and heat radiation. The side wall of the thin film tank is a multi-layer cylindrical wall. In this embodiment, the side wall is composed of 7 layers of material. There is contact thermal resistance between adjacent layers of material, and there are a total of 6 contact thermal resistances in the 7 layers of material. The heat flow rates of the two processes—convective heat transfer and heat conduction—on the sidewall of the thin-film tank are: In the formula Let be the thermal conductivity of the i-th layer. ,unit ; The contact thermal resistance between layer j and layer j+1, ,unit ; The convective heat transfer coefficient is expressed in units of... ; Let be the inner diameter of the i-th layer of material, in meters (m). A The heat transfer surface area is expressed in meters (m²). 2 , The radius of the outer wall of the membrane tank is in meters. L The height of the membrane tank sidewall is in meters; the direction from the inner wall to the outer wall of the membrane tank sidewall is the positive direction in which i and j increase.

[0037] S32: Heat flow calculation submodule of hot corner protection system, calculates the heat flow transmitted through the hot corner protection system. The hot corner protection system is composed of aluminum plate and its related insulation structure. In this embodiment, it is a composite secondary shield. The composite secondary shield is embedded in polyurethane foam during the prefabrication stage and is set in the side wall area 5m close to the bottom of the tank. In the event of leakage in the inner tank of the membrane, the hot corner protection system can protect the concrete corner with a height of about 5m from the low temperature effect and ensure the sealing of the storage tank.

[0038] The thermal resistance network diagram of the hot corner protection system is attached. Figure 3Part ② of the document includes heat transfer through three stages: convection heat transfer, heat conduction, and heat radiation. The thermal corner protection system is a multi-layer cylindrical wall. In this embodiment, the sidewall is composed of 9 layers of material. There is contact thermal resistance between adjacent layers, and a total of 8 contact thermal resistances exist between the 9 layers. The heat flow rates of the two stages of heat transfer in the hot corner protection system are: In the formula For the first i The thermal conductivity of the layer, ,unit ; The contact thermal resistance between layer j and layer j+1, ,unit ; The convective heat transfer coefficient is expressed in units of... ; Let be the inner diameter of the i-th layer of material, in meters (m). A The heat transfer surface area is expressed in meters (m²). 2 ; The radius of the outer wall of the membrane tank is in meters. L The height of the membrane tank sidewall is in meters; the direction from the inner wall of the membrane tank's thermal protection towards the outer wall is the positive direction in which i and j increase.

[0039] S33: Submodule for calculating heat flow at the bottom of the membrane tank. Calculates the heat flow transferred through the bottom of the membrane tank and analyzes the thermal resistance network diagram (see attached). Figure 3 Part ③ of the text states that the bottom does not have convection heat transfer and is not exposed to sunlight. It only involves heat transfer through heat conduction. The bottom of the membrane tank is a multi-layered planar wall, which is a composite wall composed of several layers of different materials stacked together. In this embodiment, the bottom of the membrane tank is composed of 3 layers of materials. There is contact thermal resistance between adjacent layers, and the 3 layers of materials have a total of 2 contact thermal resistances. The heat flow rates at the bottom of the membrane tank, involving both convective heat transfer and heat conduction, are as follows: In the formula: For the first i The thermal conductivity of the layer, ,unit ; The contact thermal resistance between layer j and layer j+1, ,unit ; For the first i Inner diameter of the layer material, in meters; A The heat transfer surface area is expressed in meters (m²). 2 ; Let be the radius of the outer wall of the membrane tank, in meters; the direction from the inner wall of the bottom of the membrane tank to the outer wall is the positive direction in which i and j increase.

[0040] S34: Submodule for calculating heat flow through the dome of the membrane tank. This module calculates the heat flow transferred through the dome of the membrane tank and analyzes the thermal resistance network diagram (see attached). Figure 3 Part ④ is divided into four parts: natural convection between external air and the LNG outer tank dome, solar thermal radiation to the dome, heat entering the tank through the dome insulation material in the form of thermal conduction, and natural convection between the LNG inner tank and the gas phase space. In this embodiment, the membrane tank dome is composed of three layers of material. There is contact thermal resistance between two adjacent layers of material, and there are two contact thermal resistances in total for the three layers of material. For the dome of a thin-film tank, its surface area can be calculated using the spherical cap formula: In the formula: R The radius of the sphere containing the cap is in meters (m). h The arch height is expressed in meters (m). The radius of the sphere containing the crown R The calculation formula is: In the formula: r The radius of the bottom surface of the spherical cap is a fixed value here, the same as the bottom radius of the membrane tank and the same as the outer radius of the membrane tank, in meters; The heat flow rates of the two stages—convective heat transfer and heat conduction—at the dome of the thin-film tank are: In the formula: Let be the thermal conductivity of the i-th layer. ,unit ; The contact thermal resistance between layer j and layer j+1, ,unit ; This refers to the external convection heat transfer coefficient, also known as the natural air convection coefficient, in units of... ; The internal heat transfer coefficient is the natural convection coefficient between the inner wall of the thin film and the gas phase space, expressed in units of... ; Let be the inner diameter of the i-th layer of material, in meters (m). The radius of the outer wall of the membrane tank is in meters. The height of the i-th arch is in meters (m). The height of the outer wall of the vault is in meters (m). The height of the inner wall of the arch is denoted by ; the direction from the outer wall of the arch towards the inner wall of the arch is the positive direction in which i and j increase.

[0041] S35: Submodule for calculating heat flow of solid components in membrane tanks. This submodule calculates heat transfer caused by six types of ceiling hangers and ceiling openings, including: top inlet, bottom inlet, BOG outlet, low-pressure pump connection, ceiling equipment access hole, and ceiling manhole. One end of each opening is connected to the cryogenic liquid cargo, and the other end is connected to the high-temperature outer wall. The heat flow transferred is as follows: in: In the formula: —The thermal conductivity of each connector, i ≤9, unit ; —The thermal conductivity cross-sectional area of ​​each connector, i ≤9, unit m 2 ; —Effective thermal conductivity length of each connector, in meters; —The thermal conductivity temperature difference between each connector, in K; —Inner diameter of each connector, in meters; —Outer diameter of each connector, in meters; —Thickness of each connector, in meters (m) S36: Solar radiation calculation submodule, calculates heat transfer caused by solar radiation. The membrane tank has three parts that are subject to thermal radiation: the side wall of the membrane tank, the thermal corner protection system, and the bottom of the membrane tank. Heat flow from thermal radiation on the sidewall of the membrane tank: Heat flow from thermal radiation of the thermal angle protection system: Heat flow from thermal radiation at the dome of the membrane tank: In the formula: Effective radiation time during the day, in hours (h). The absorption coefficient of the outer wall surface material is given. The concrete reflectance coefficient is 0.95, which means the absorption coefficient is 0.05. The average heat transfer coefficient is expressed in units of... ; The temperature rise on the outer surface of the thin-film tank due to solar radiation is expressed in Kelvin. The convective heat transfer coefficient between the outer wall of the thin-film tank and the air is expressed in units of... ; The outer diameter of the membrane tank is in meters (m). The height of the outer wall of the vault is in meters (m).

[0042] Step 3, the daily evaporation loss calculation module, integrates heat flow transfer and solar radiation compensation from various parts of the core heat transfer calculation module. It applies the LNG property conversion model, combining parameters such as latent heat of vaporization, density, and volume to achieve accurate prediction of the daily evaporation rate (BOG) and evaluation of cold storage performance. This includes: a total heat integration calculation submodule, an LNG volume and filling rate calculation submodule, and a daily evaporation rate calculation submodule. The total heat integration calculation submodule is used to integrate the heat flow data of five submodules in the core heat transfer calculation module in real time, including: heat flow of the membrane tank sidewall, heat flow of the thermal corner protection system, heat flow of the membrane tank bottom, heat flow of the membrane tank dome, and solar radiation. The integrated LNG membrane tank transfers a total heat flow: The LNG volume and filling rate calculation submodule is used to calculate the LNG volume and the LNG filling rate in the membrane tank by combining the membrane tank structure parameters in the dynamic parameter update module. The volume of LNG includes the LNG storage section inside the membrane tank and the gas phase space above it; The filling rate is obtained by the ratio of the highest liquid level stored in the storage tank to the height of the outer tank wall. The daily evaporation rate calculation submodule integrates parameters such as latent heat of vaporization and effective volume to convert total heat flow into daily evaporation loss, and finally outputs a BOG value accurate to 0.000001%, forming the core evaluation index of cold insulation performance. LNG has a boiling point of -164℃, far below ambient temperature. When a steady state is reached inside the LNG membrane tank, if heat is transferred into the tank, a corresponding mass of LNG will vaporize into liquid natural gas. An LNG property conversion model is established as follows: Where: Q is the total heat flow of LNG; This represents the latent heat of vaporization of LNG at its boiling point under standard atmospheric pressure. The vaporization quality of LNG over 24 hours; The formula for calculating the daily evaporation rate of LNG is: In the formula: The density of LNG, in units ; —Latent heat of vaporization of liquefied natural gas, in units of ; —Volume of the membrane tank, in cubic meters (m³) 3 ; —LNG filling rate; All parameters required for the calculation process in S3 are attached. Figure 4 As shown.

[0043] S4: Visualize the results output by the calculation module to provide technicians with an intuitive data display, facilitating further analysis and design optimization.

[0044] Data visualization in S4 is achieved through the data visualization module, as shown in the attached image. Figure 5 As shown, this module includes: a real-time calculation results submodule, a thermodynamic distribution visualization submodule, a thin-film tank structure visualization submodule, and a technical description submodule; This platform adopts a scientific three-column layout design, as shown in the attached diagram. Figure 6 As shown, the left column contains the basic environmental parameters sub-module of the calculation platform input module, the real-time calculation results sub-module of the data visualization module, and the thermodynamic distribution visualization sub-module. Occupying 25% of the interface, it allows designers to set basic operating parameters and view the final calculation results. The middle column is the core parameter configuration area, containing the initial parameter setting sub-module and the dynamic parameter update module of the calculation module. Occupying 50% of the interface, it uses a tabbed design to organize hundreds of professional parameters for four key components: membrane tank sidewall, thermal corner protection system, membrane tank bottom, membrane tank dome, and membrane tank solid components. The right column is the visualization display area, containing the membrane tank structure visualization sub-module and the technical description module of the data visualization module. Occupying 25% of the interface, it displays the cross-sectional view of the tank structure and labels the heat flow values ​​for each part.

[0045] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A system for calculating the cold insulation of LNG membrane tanks and predicting daily evaporation rate, characterized in that, It includes a computing platform input module, a computing module, and a data visualization module; The computing platform input module is responsible for receiving and organizing various input parameters and accurately transmitting them to the computing module. The computing module performs calculations based on the received input parameters and outputs parameters such as the total heat input from the LNG membrane tank and the daily evaporation loss of the LNG membrane tank. At the same time, it transmits other result parameters generated during the calculation process to the data visualization module in an intuitive form, making it convenient for staff to quickly view, verify and analyze various result data.

2. The LNG membrane tank insulation calculation and daily evaporation rate prediction system according to claim 1, characterized in that, The computing platform input module includes: a basic environmental parameter module, a thin-film tank structure parameter configuration module, and a material thermal property configuration module, wherein... The basic environmental parameter module is used to input parameters such as ambient temperature setting, solar radiation intensity, and effective solar radiation time. The membrane tank structure parameter configuration module is used to input sidewall height parameters, sidewall inner diameter parameters, dome height parameters, tank bottom radius parameters, material layer quantity parameters, and material layer thickness parameters; The material thermal property configuration module is used to input the material's thermal conductivity, convective heat transfer coefficient, and interfacial contact thermal resistance.

3. The LNG membrane tank insulation calculation and daily evaporation rate prediction system according to claim 2, characterized in that, The calculation module includes an initial parameter setting module, a dynamic parameter update module, a core heat transfer calculation module, a daily evaporation loss calculation module, and a calculation result management module; The initial parameter setting module provides all the basic parameters required for the core heat transfer calculation module to operate; the dynamic parameter update module corrects the basic parameters, and the corrected parameters are sent to the core heat transfer calculation module to complete the accurate calculation of the heat flow of each part of the LNG membrane tank. The daily evaporation loss calculation module receives and integrates the output results of the core heat transfer calculation module, and based on these results, completes the prediction of the daily evaporation rate and outputs the prediction data. The calculation result management module judges the predicted data of the daily evaporation loss calculation module, and automatically triggers an early warning when the prediction result exceeds the preset standard; The initial parameter setting module is used to establish a three-dimensional structural feature database of the thin film tank and configure multi-level calculation boundary conditions such as ambient temperature range, material thermal conductivity, and contact thermal resistance, providing users with a standard for parameter input. The dynamic parameter update module is used to store the LNG film tank three-dimensional structural feature database, ambient temperature range, material thermal conductivity, contact thermal resistance and other multi-level calculation boundary conditions change parameters to ensure real-time response to parameter modifications during the calculation process. The core heat transfer calculation module is based on the thermal resistance network diagram to analyze the heat transfer mode of the five major parts that make up the thin film tank, and constructs heat transfer models of the side wall, thermal corner protection, tank bottom, tank top and solid components to accurately calculate the heat flow of each part. The daily evaporation loss calculation module is used to integrate heat flow transfer and solar radiation compensation in various parts, apply the LNG property conversion model, and combine parameters such as latent heat of vaporization and density volume to achieve accurate prediction of daily evaporation rate (BOG) and evaluation of cold preservation performance. The calculation result management module is used to judge the daily evaporation rate index and issue early warnings for exceeding the daily evaporation rate standard.

4. The LNG membrane tank insulation calculation and daily evaporation rate prediction system according to claim 3, characterized in that, The initial parameter setting module includes a basic environmental parameter submodule, a thin-film tank structure parameter submodule, and a material thermal property parameter submodule, wherein... The basic environmental parameters submodule is used to store data, including ambient temperature, solar radiation intensity, and effective solar radiation time. The membrane tank structure parameter submodule is used to store the LNG membrane tank three-dimensional storage tank geometric feature database, including data on the inner tangent circle diameter of the membrane tank, the tank wall height, the outer tangent circle diameter, the dome height, and the thickness of the layered insulation material, to construct a complete membrane tank spatial structure model; The material thermal characteristics submodule is used to store the thermophysical parameters of the layered insulation material, including the thermal conductivity of the material, the contact thermal resistance between two adjacent layers of material, and the convective heat transfer coefficient of the space.

5. The LNG membrane tank insulation calculation and daily evaporation rate prediction system according to claim 4, characterized in that, The dynamic parameter update module includes: a basic environmental parameter submodule, a thin-film tank structure parameter submodule, and a material thermal property parameter submodule. Similar to the initial parameter module, the dynamic parameter update module achieves dynamic adjustment of parameters through real-time session state management technology. The core heat transfer calculation module includes sub-modules for calculating heat flow to the side walls, heat flow to the thermal corner protection system, heat flow to the bottom of the thin-film tank, heat flow to the dome of the thin-film tank, heat flow to the solid components of the thin-film tank, and solar radiation calculation. The sidewall heat flow calculation submodule is based on a multi-layer cylindrical wall heat transfer model. By analyzing a one-dimensional thermal resistance network diagram, it accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the inner wall of the membrane, as well as the natural convection heat flow between the external environment and the air outside the membrane tank. Finally, it outputs the total heat flow transferred through the sidewall region. The heat flow calculation submodule of the hot corner protection system, based on the multi-layer cylindrical wall heat transfer model, analyzes the 5m hot corner protection area at the bottom of the tank wall to establish a thermal resistance network diagram, accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the hot corner protection system, the natural convection heat flow between the external environment and the hot corner protection system, and finally outputs the total heat flow transferred through the hot corner protection system. The heat flow calculation submodule at the bottom of the membrane tank is based on a multi-layer planar wall heat transfer model. It analyzes the one-dimensional network heat map at the bottom of the tank, accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the inner wall of the membrane tank bottom, and finally outputs the total heat flow transferred through the bottom of the membrane tank. The membrane tank dome heat flow calculation submodule establishes an arched multi-layer heat transfer model to accurately calculate the heat flow caused by the temperature difference between the ambient temperature and the inner wall of the membrane dome, the heat flow caused by the natural convection heat transfer between the external environment and the outer wall of the membrane tank dome, and the heat flow caused by the natural convection heat transfer between the inner wall of the membrane tank dome and the gas phase space inside the tank. Finally, it outputs the total heat flow transferred through the dome region. The heat flow calculation submodule for solid components of the membrane tank accurately calculates the heat flow caused by the temperature difference between the ambient temperature and the internal temperature of the membrane tank by analyzing the bottom one-dimensional network thermal diagram of the solid components, and finally outputs the total heat flow transferred through the solid components. The solar radiation calculation submodule is used to calculate the heat flow caused by solar radiation heat transfer to the outer wall of the thin film tank. Since the bottom of the thin film tank is not subject to solar radiation, the calculation area includes three parts: the side wall of the thin film tank, the thermal corner protection system, and the dome of the thin film tank. Finally, the total heat flow transferred by thermal radiation is output.

6. The LNG membrane tank insulation calculation and daily evaporation rate prediction system according to claim 5, characterized in that, The daily evaporation loss calculation module includes: a total heat integration calculation submodule, an LNG volume and filling rate calculation submodule, and a daily evaporation rate calculation submodule, wherein... The total heat integration calculation submodule is used to integrate the heat flow data of the five submodules in the core heat transfer calculation module in real time; The LNG volume and filling rate calculation submodule is used to calculate the LNG volume and the LNG filling rate in the membrane tank by combining the membrane tank structure parameters in the dynamic parameter update module. The daily evaporation rate calculation submodule integrates parameters such as latent heat of vaporization and effective volume to convert total heat flow into daily evaporation loss, and finally outputs a BOG value accurate to 0.000001%, forming the core evaluation index of cold insulation performance.

7. The LNG membrane tank insulation calculation and daily evaporation rate prediction system according to claim 6, characterized in that, The data visualization module includes: a real-time calculation result submodule, a thermodynamic distribution visualization submodule, a thin-film tank structure visualization module, and a technical description submodule, wherein... The real-time calculation results module is used to display the ambient temperature, total heat flow, and daily evaporation rate. The thermodynamic distribution visualization submodule displays the heat flow and percentage of each part in tabular form, with the percentage of heat flow clearly visualized using a pie chart. The membrane tank structure visualization module constructs a three-dimensional sectional view of the membrane tank structure on the ground coordinate system, performs spatial mapping of heat flow distribution on the sectional view, and labels the heat flow of each part; The technical description submodule is used to annotate the structure of the thin-film tank, and to explain the thermal corner protection system and the heat transfer characteristics of each part.

8. A method for calculating the insulation of an LNG membrane tank and predicting its daily evaporation rate according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Start the platform. The system will automatically enter the computing platform input module. The computing platform input module will load the initial settings, which include the basic ambient temperature, thin film tank structural parameter configuration, and material thermal property configuration. S2: Based on actual engineering design requirements, technicians can dynamically adjust the initial parameters loaded in S1 through the dynamic parameter setting submodule built into the calculation module, flexibly adapting to different working conditions and design standards, and ensuring the accuracy of the calculation parameters. S3: Inside the calculation module, the core heat transfer calculation submodule completes the accurate calculation of heat flow in various parts of the LNG membrane tank based on the parameters adjusted by the dynamic parameter setting submodule. The daily evaporation loss calculation module receives and integrates the output results of the core heat transfer calculation module, completes the prediction of the daily evaporation rate based on the heat flow calculation results, and outputs the corresponding prediction data. At the same time, the calculation result management module judges the prediction data of the daily evaporation loss calculation module, and automatically triggers an early warning reminder when the prediction result exceeds the preset standard. S4: The data visualization module receives all the result data output by the calculation module, performs visualization processing on it, and provides data support to technical personnel in an intuitive and clear presentation format.

9. The method for calculating the cold insulation of an LNG membrane tank and predicting its daily evaporation rate according to claim 8, characterized in that, The basic environmental parameters in S1 include: ambient temperature setting, solar radiation intensity setting, and effective solar radiation time; the membrane tank structural parameters include: sidewall height parameter, sidewall inner diameter parameter, dome height parameter, tank bottom radius parameter, material layer quantity parameter, and material layer thickness parameter; the material thermal property parameters include: material thermal conductivity parameter, convective heat transfer parameter, and layer interface contact parameter. The calculations in S3 follow the following method: Make the following assumptions: First, under a specific working condition, the sun's radiation and the atmospheric temperature are constant and do not change with time and location. Secondly, for the tank body, the thickness of each part is uniform, and local thickness variations are ignored; The volume of the third tank does not change with temperature; that is, the volume is constant. The materials in each layer of the fourth tank are isotropic, meaning that the thermal conductivity of the materials does not change with temperature. The fifth heat transfer only follows one-dimensional steady-state radial conduction, without considering the axial temperature gradient; Based on the above assumptions, a heat transfer model is established: For heat conduction: ; For convective heat transfer: ; In the formula The heat flux density for thermal conduction. The heat flux density for convective heat transfer is the heat flow rate per unit area. W / m 2 ; Temperature of the outer wall of the tank, in units K ; Temperature of the inner wall of the tank, same as LNG temperature, unit: K , Temperature of the hot air outside the tank (ambient temperature), unit K ; The convective heat transfer coefficient is expressed in units of... W / (m 2 ·K) , Heat flow is the amount of heat passing through a given area per unit time, i.e., the heat flux density multiplied by the given area, with units of W. From the heat flux density formula above, the expressions for the heat flow rate from the external environment to the tank under heat conduction and convection heat transfer can be derived as follows: For heat conduction: For convective heat transfer: In the formula, A is the heat transfer surface area, in m². The heat flow expression can be rewritten in temperature and pressure form: For heat conduction: For convective heat transfer: Add the two equations together and eliminate the temperature. get: The common heat flow of both heat conduction and convection heat transfer: The heat flow expression can also be rewritten as: In the formula k The average heat transfer coefficient is expressed as: The heat conduction process considers contact thermal resistance, and the contact thermal resistance per unit area is denoted as... R The unit is The thermal resistance per unit area during the heat transfer process is determined by , and R The total heat flow from the two stages of convection and conduction is: Establish a heat balance equation on the outer wall of the thin-film tank: By simplifying the heat balance equation, we obtain: In the formula The absorption coefficient of the outer wall surface material. The average heat transfer coefficient, The temperature rise on the outer surface of the thin-film tank is due to solar radiation. The convective heat transfer coefficient between the outer wall of the thin-film tank and the air; The solar radiative heat flux is obtained through the heat balance equation: The heat flow of solar thermal radiation is: .

10. The method for calculating the cold insulation of an LNG membrane tank and predicting its daily evaporation rate according to claim 9, characterized in that, The core heat transfer calculation submodule in S3 includes: Based on the heat transfer model established above, the heat transfer sub-calculation module in the calculation module follows the following approach: S31: Membrane tank sidewall heat flow calculation submodule, calculates the heat flow transferred through the membrane tank sidewall, including heat transfer through three stages: convection heat transfer, heat conduction and heat radiation. The membrane tank sidewall is a multi-layer cylindrical wall. The heat flow rates of the two processes—convective heat transfer and heat conduction—on the sidewall of the thin-film tank are: In the formula Let be the thermal conductivity of the i-th layer. ,unit ; The contact thermal resistance between layer j and layer j+1, ,unit ; The convective heat transfer coefficient is expressed in units of... ; Let be the inner diameter of the i-th layer of material, in meters (m). A The heat transfer surface area is expressed in meters (m²). 2 , The radius of the outer wall of the membrane tank is in meters. L The height of the membrane tank sidewall is in meters; the direction from the inner wall to the outer wall of the membrane tank sidewall is the positive direction of the increase of i and j. S32: Heat flow calculation submodule for hot corner protection system, which calculates the heat flow transmitted through the hot corner protection system, which consists of an aluminum plate and its related insulation structure; The thermal resistance network diagram of the hot corner protection system includes heat transfer through three stages: convection heat transfer, heat conduction and heat radiation. The hot corner protection system belongs to a multi-layer cylindrical wall. The heat flow rates of the two stages of heat transfer in the hot corner protection system are: In the formula For the first i The thermal conductivity of the layer, ,unit ; The contact thermal resistance between layer j and layer j+1, ,unit ; The convective heat transfer coefficient is expressed in units of... ; Let be the inner diameter of the i-th layer of material, in meters (m). A The heat transfer surface area is expressed in meters (m²). 2 ; The radius of the outer wall of the membrane tank is in meters. L The height of the membrane tank sidewall is in meters; the direction from the inner wall of the membrane tank's thermal protection to the outer wall is the positive direction of the increase of i and j. S33: The heat flow calculation submodule at the bottom of the membrane tank calculates the heat flow transferred through the bottom of the membrane tank. It analyzes the heat resistance network diagram and finds that the bottom of the membrane tank has no convective heat transfer and is not exposed to sunlight. It only includes heat transfer through one link: heat conduction. The heat flow rates at the bottom of the membrane tank, involving both convective heat transfer and heat conduction, are as follows: In the formula: For the first i The thermal conductivity of the layer, ,unit ; The contact thermal resistance between layer j and layer j+1, ,unit ; For the first i Inner diameter of the layer material, in meters; A The heat transfer surface area is expressed in meters (m²). 2 ; Let be the radius of the outer wall of the membrane tank, in meters; the direction from the inner wall of the bottom of the membrane tank to the outer wall is the positive direction in which i and j increase. S34: The membrane tank dome heat flow calculation submodule calculates the heat flow transferred through the membrane tank dome and analyzes the thermal resistance network diagram, which is divided into four parts: natural convection between the external air and the LNG outer tank dome, solar thermal radiation to the dome, heat entering the tank through the dome insulation material in the form of thermal conduction, and natural convection between the LNG inner tank and the gas phase space. For the dome of a thin-film tank, its surface area can be calculated using the spherical cap formula: In the formula: R The radius of the sphere containing the cap is in meters (m). h The arch height is expressed in meters (m). The radius of the sphere containing the crown R The calculation formula is: In the formula: r The radius of the bottom surface of the spherical cap is a fixed value here, the same as the bottom radius of the membrane tank and the same as the outer radius of the membrane tank, in meters; The heat flow rates of the two stages—convective heat transfer and heat conduction—at the dome of the thin-film tank are: In the formula: Let be the thermal conductivity of the i-th layer. ,unit ; The contact thermal resistance between layer j and layer j+1, ,unit ; This refers to the external convection heat transfer coefficient, also known as the natural air convection coefficient, in units of... ; The internal heat transfer coefficient is the natural convection coefficient between the inner wall of the thin film and the gas phase space, expressed in units of... ; Let be the inner diameter of the i-th layer of material, in meters (m). The radius of the outer wall of the membrane tank is in meters. The height of the i-th arch is in meters (m). The height of the outer wall of the vault is in meters (m). The height of the inner wall of the vault is denoted by ; the direction from the outer wall of the vault to the inner wall of the vault is the positive direction in which i and j increase. S35: Submodule for calculating heat flow of solid components in membrane tanks. This module calculates heat transfer caused by six types of ceiling hangers and ceiling openings, including: top inlet, bottom inlet, BOG outlet, low-pressure pump connection, ceiling equipment access hole, and ceiling manhole. One end of each opening is connected to the cryogenic liquid cargo, and the other end is connected to the high-temperature outer wall. The heat flow transferred is as follows: in: In the formula: —The thermal conductivity of each connector, i ≤9, unit ; —The thermal conductivity cross-sectional area of ​​each connector, i ≤ 9, unit m 2 ; —Effective thermal conductivity length of each connector, in meters; —The thermal conductivity temperature difference between each connector, in K; —Inner diameter of each connector, in meters; —Outer diameter of each connector, in meters; —Thickness of each connector, in meters (m) S36: Solar radiation calculation submodule, calculates heat transfer caused by solar radiation. The membrane tank has three parts that are subject to thermal radiation: the side wall of the membrane tank, the thermal corner protection system, and the bottom of the membrane tank. Heat flow from thermal radiation on the sidewall of the membrane tank: Heat flow from thermal radiation of the thermal angle protection system: Heat flow from thermal radiation at the dome of the membrane tank: In the formula: Effective radiation time during the day, in hours (h). The absorption coefficient of the outer wall surface material is 0.95, meaning the absorption coefficient of concrete is 0.

05. The average heat transfer coefficient is expressed in units of... ; The temperature rise on the outer surface of the thin-film tank due to solar radiation is expressed in Kelvin. The convective heat transfer coefficient between the outer wall of the thin-film tank and the air is expressed in units of... ; The outer diameter of the membrane tank is in meters (m). The height of the outer wall of the vault is in meters (m). The daily evaporation loss calculation module integrates heat flow transfer and solar radiation compensation from various parts of the core heat transfer calculation module. It applies an LNG property conversion model, combining parameters such as latent heat of vaporization, density, and volume to accurately predict the daily evaporation rate and assess its cold-keeping performance. This module includes: a total heat integration calculation submodule, an LNG volume and filling rate calculation submodule, and a daily evaporation rate calculation submodule. The total heat integration calculation submodule is used to integrate the heat flow data of five submodules in the core heat transfer calculation module in real time, including: heat flow of the membrane tank sidewall, heat flow of the thermal corner protection system, heat flow of the membrane tank bottom, heat flow of the membrane tank dome, and solar radiation. The integrated LNG membrane tank transfers a total heat flow: The LNG volume and filling rate calculation submodule is used to calculate the LNG volume and the LNG filling rate in the membrane tank by combining the membrane tank structure parameters in the dynamic parameter update module. The volume of LNG includes the LNG storage section inside the membrane tank and the gas phase space above it; The filling rate is obtained by the ratio of the highest liquid level stored in the storage tank to the height of the outer tank wall. The daily evaporation rate calculation submodule integrates parameters such as latent heat of vaporization and effective volume to convert total heat flow into daily evaporation loss, and finally outputs a BOG value accurate to 0.000001%, forming the core evaluation index of cold insulation performance. Establish an LNG property conversion model: In the formula: Q is the total heat flow of LNG; This represents the latent heat of vaporization of LNG at its boiling point under standard atmospheric pressure. The vaporization quality of LNG over 24 hours; The formula for calculating the daily evaporation rate of LNG is: In the formula: The density of LNG, in units ; —Latent heat of vaporization of liquefied natural gas, in units of ; —Volume of the membrane tank, in cubic meters (m³) 3 ; —LNG filling rate.

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