1.5-dimensional single-phase pipeline flow heat transfer simulation method considering gravity

Abstract

The invention relates to the technical field of pipeline simulation, and discloses a gravity-considered 1.5-dimensional single-phase pipeline flow heat transfer simulation method, which comprises the following steps of: acquiring pipeline data and fluid data of a target pipeline, establishing a three-dimensional calculation fluid dynamic model, simulating dimensionless data under multiple groups of working conditions, and calculating the flow heat transfer of the target pipeline according to the dimensionless data. A top nusselt number calculation formula and a bottom nusselt number calculation formula are fitted, a 1.5-dimensional single-phase pipeline flow heat transfer model considering gravity is established, a target pipeline is discretized, the time step length is determined, fluid data at all discrete nodes are solved, and the flow heat transfer efficiency is improved. And solving the temperature of the pipe wall at the bottom of the pipeline, the temperature of the pipe wall at the top of the pipeline and the temperature of the thermal insulation layer according to the fluid data at each discrete node until calculation within the simulation time is completed. By introducing the upper and lower wall surface differential heat exchange model, the upper and lower temperature difference of the pipeline caused by gas layering in the precooling process can be accurately simulated, and a reliable and practical calculation tool is provided for precooling process design and safety evaluation of the long-distance low-temperature liquid pipeline.

Description

Technical Field

[0001] This invention relates to the field of pipeline simulation technology, and in particular to a 1.5-dimensional single-phase pipeline flow heat transfer simulation method that takes gravity into account. Background Technology

[0002] Cryogenic liquid pipelines are typically at room temperature before commissioning. Directly introducing the cryogenic liquid into the pipeline causes rapid temperature changes, leading to a sudden increase in stress on pipes, flanges, and other equipment, uneven material shrinkage, and ultimately, leaks. Therefore, pre-cooling is essential before commissioning. To reduce the cost of pre-cooling long-distance pipelines, cryogenic nitrogen is generally chosen as the refrigerant. However, nitrogen density is highly sensitive to temperature, and during pre-cooling, gas stratification causes the lower part of the pipeline to cool faster than the upper part, resulting in a significant temperature difference across the same cross-section. Therefore, temperature changes at both the upper and lower sections of the pipeline must be monitored during pre-cooling simulation. One-dimensional models cannot simulate the temperature difference between the upper and lower sections of the pipeline, while two-dimensional and three-dimensional CFD (Computational Fluid Dynamics) models are computationally intensive and cannot simulate pipelines exceeding tens of kilometers in length. Summary of the Invention

[0003] This invention provides a 1.5-dimensional single-phase pipe flow heat transfer simulation method that takes gravity into account, in order to overcome the shortcomings of the prior art.

[0004] This invention provides a 1.5-dimensional single-phase pipe flow heat transfer simulation method considering gravity, comprising: Acquire pipeline and fluid data for the target pipeline; Based on pipeline and fluid data, a three-dimensional computational fluid dynamics model was established to simulate dimensionless number data under multiple working conditions, and the top and bottom Nusselt number calculation formulas were obtained by fitting. By combining the top and bottom Nusselt number calculation formulas, a 1.5-dimensional single-phase pipe flow heat transfer model considering gravity is established. Based on a 1.5-dimensional single-phase pipe flow heat transfer model, the target pipe is discretized and the time step is confirmed. The fluid data at each discrete node is solved, and the temperatures of the bottom wall, top wall, and insulation layer of the pipe are calculated based on the fluid data at each discrete node until the calculation within the simulation time is completed.

[0005] According to the present invention, a 1.5-dimensional single-phase pipe flow heat transfer simulation method considering gravity is provided. The pipe data includes any one or any combination of the following: length, inner diameter, wall thickness, roughness, insulation method, insulation layer material, insulation layer thickness, and ambient temperature; the fluid data includes fluid medium and physical property parameter data.

[0006] According to the present invention, a 1.5-dimensional single-phase pipe flow heat transfer simulation method considering gravity is provided, wherein the dimensionless number data includes any one or any combination of the following: Reynolds number. Re Prandtl numbers Pr Top Grashof number Gr top 、 Bottom Grashof number Gr down 、 Top Nusselt Nu top 、 Bottom Nusselt Nu down ;in, Reynolds number Re The expression is: , Prandtl number Pr The expression is: , Top Grashof number Gr top The expression is: , Bottom Grashof number Gr down The expression is: , Top Nusselt Nu top The expression is: , Bottom Nusselt Nu down The expression is: , In the formula, ρ Fluid density, kg / m³ 3 ; v The fluid velocity is expressed in m / s. d The inner diameter of the pipe is in meters (m). μ The viscosity is the fluid dynamic viscosity, Pa·s; c Specific heat capacity of the fluid, J / (kg·℃); λ ν is the thermal conductivity of the fluid, W / (m·K); β The coefficient of volumetric thermal expansion is given in °C. -1 ; g The acceleration due to gravity is m / s². 2 ; T w,top The temperature of the inner wall at the top of the pipe cross-section, in °C;T The fluid temperature is expressed in °C. T w,down The temperature of the inner wall at the bottom of the pipe cross-section, in °C; h top The heat transfer coefficient of the inner wall at the top of the pipe cross-section is given in W / (m²). 2 ·℃); h down The heat transfer coefficient of the inner wall at the bottom of the pipe cross-section is given in W / (m²). 2 ·℃); q top The heat flux density at the top of the inner wall of the pipe is W / m. 2 ; q down The heat flux density at the bottom of the inner wall of the pipe is W / m. 2 .

[0007] According to the 1.5D single-phase pipe flow heat transfer simulation method considering gravity provided by the present invention, the top Nusselt number is calculated as follows: , The formula for calculating the bottom Nusselt number is: , In the formula, Re The Reynolds number is... Pr For Prandtl numbers, Gr top Top Grashof number ，Gr down The base Grashof number, a 1. a 2. a 3. a 4. a 5 represents the fitting coefficient in the top Nusselt number calculation formula; b 1. b 2. b 3. b 4. b 5 represents the fitting coefficient in the calculation of the bottom Nusselt number.

[0008] According to the present invention, a 1.5-dimensional single-phase pipe flow heat transfer simulation method considering gravity is provided. The expression of the 1.5-dimensional single-phase pipe flow heat transfer model includes: , , , , , , , , In the formula, m The fluid mass flow rate is expressed in kg / s. A The cross-sectional area of ​​the pipe is in meters. 2 ; P The fluid pressure is expressed in Pa. h Enthalpy of the fluid, J / kg; f The coefficient of friction; ρ s The density of the pipe wall or insulation layer, kg / m³ 3 ; c s Specific heat capacity of the pipe wall or insulation layer, J / (kg·℃); λ s The value represents the thermal conductivity of the pipe wall or insulation layer, in W / (m·K); subscripts 1 and 2 represent the parameters of adjacent pipe walls or insulation layers, respectively. t For time, x Let be the distance from the discretized node of the pipeline to the starting point, in meters. G Let m be the height of the node after the pipeline is discretized; Nu top The top Nusselt number; Nu down The bottom Nusselt number; T W The pipe wall temperature is K; r Let be the distance from the radially discretized node to the axis, in meters (m). T f Let K be the fluid temperature.

[0009] According to the present invention, a 1.5D single-phase pipe flow heat transfer simulation method considering gravity is provided. The method involves discretizing the target pipe and determining the time step based on the 1.5D single-phase pipe flow heat transfer model, solving for the fluid data at each discrete node, and calculating the temperatures of the bottom wall, top wall, and insulation layer of the pipe based on the fluid data at each discrete node, until the calculation within the simulation time is completed. This includes: The fluid data at each discrete node is obtained using the method of characteristics. For intermediate discrete nodes, the fluid data at that node is obtained by combining Euler's prediction and the golden section method. For boundary discrete nodes, the fluid data at that node is obtained by combining the boundary conditions and Euler's prediction and the golden section method.

[0010] According to the present invention, a 1.5-dimensional single-phase pipe flow heat transfer simulation method considering gravity is provided, and the expression of the method of characteristics includes: Left characteristic line equation (along) ): , The equation of the right characteristic line (along) ): , Material characteristic line equation (along) ): , By taking the difference along the characteristic line, we get: , , , in: , In the formula, subscript A represents the fluid data at point A; subscript G represents the fluid data at point G; subscript H represents the fluid data at point H; and subscript M represents the fluid data at point M. a s Let be the speed of sound in the fluid, in m / s; t Let be the time step, in seconds; x Let m be the spatial step size. θ The pipe inclination angle is expressed in degrees (°).

[0011] According to the present invention, a 1.5D single-phase pipe flow heat transfer simulation method considering gravity is provided. The method involves discretizing the target pipe and determining the time step based on the 1.5D single-phase pipe flow heat transfer model, solving for the fluid data at each discrete node, and calculating the temperatures of the bottom wall, top wall, and insulation layer of the pipe based on the fluid data at each discrete node, until the calculation within the simulation time is completed. This includes: Based on the fluid data at each discrete node, and using a 1.5-dimensional single-phase pipe flow heat transfer model, the implicit difference method is employed to discretize along the radial direction of the pipe, and the temperatures of the bottom wall, top wall, and insulation layer of the pipe are solved.

[0012] This invention also provides a 1.5-dimensional single-phase pipe flow heat transfer simulation system that considers gravity, comprising: The data acquisition module is used to acquire pipeline data and fluid data of the target pipeline. The 3D computational fluid dynamics model building module is used to: build a 3D computational fluid dynamics model based on pipeline data and fluid data, simulate dimensionless number data under multiple working conditions, and fit the top Nusselt number calculation formula and the bottom Nusselt number calculation formula. The 1.5D single-phase pipe flow heat transfer model establishment module is used to: combine the top Nusselt number calculation formula and the bottom Nusselt number calculation formula to establish a 1.5D single-phase pipe flow heat transfer model that takes gravity into account. The simulation module is used to: discretize the target pipe and confirm the time step based on a 1.5-dimensional single-phase pipe flow heat transfer model, solve for the fluid data at each discrete node, and solve for the temperature of the bottom wall, top wall and insulation layer of the pipe based on the fluid data at each discrete node, until the calculation within the simulation time is completed.

[0013] The present invention also provides an electronic device, including a processor and a memory storing a computer program, wherein the processor executes the computer program to implement any of the above-described 1.5-dimensional single-phase pipe flow heat transfer simulation methods considering gravity.

[0014] The present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the 1.5-dimensional single-phase pipe flow heat transfer simulation method considering gravity as described above.

[0015] The present invention also provides a computer program product, which includes a computer program that can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer is able to execute any of the above-described 1.5-dimensional single-phase pipe flow heat transfer simulation methods that consider gravity.

[0016] The present invention provides a 1.5-dimensional single-phase pipe flow heat transfer simulation method that considers gravity, which has at least the following beneficial effects: The method proposed in this invention features a clear calculation process, simplicity, and high computational speed. By establishing a "1.5D" model (i.e., introducing independent calculation dimensions for the top and bottom pipe wall temperatures radially in the pipe cross-section based on the axial one-dimensional flow model), this invention effectively overcomes the fundamental deficiency of existing one-dimensional models that cannot consider gravity factors, thus failing to simulate the temperature difference between the top and bottom of the pipe. Compared to computationally intensive two-dimensional or three-dimensional CFD models, this invention significantly reduces computational complexity while ensuring effective monitoring and prediction of the key parameter of the temperature difference between the top and bottom of the pipe. This makes efficient and feasible numerical simulation of the precooling process of pipelines tens of kilometers or even longer possible, providing an efficient and reliable calculation method for the process design and simulation of precooling processes in long-distance cryogenic liquid pipelines.

[0017] This invention uses a three-dimensional CFD model to simulate basic operating conditions and fits the results to obtain Nusselt number calculation formulas applicable to the top and bottom of the pipe cross-section. These two formulas, incorporating top and bottom Grashof numbers, accurately characterize the differentiated influence of gravity-induced natural convection on heat transfer intensity at different locations within the pipe. Embedding this differentiated heat transfer relationship into a 1.5-dimensional single-phase pipe flow heat transfer model allows the model to more realistically simulate the physical process of uneven cooling between the top and bottom of the pipe during cryogenic nitrogen precooling.

[0018] This invention employs the method of characteristics to solve the axial fluid dynamics equations of a pipe, offering high efficiency and numerical stability for single-phase transient flow calculations. For radial heat transfer through the pipe wall and insulation layer, an implicit finite difference method is used to ensure the stability of the temperature field calculation. This hybrid solution strategy of "axial method of characteristics + radial implicit finite difference" achieves coupled transient simulation of pipe fluid parameters and structural temperature field while maintaining low computational complexity.

[0019] This invention fully considers various influencing factors in actual engineering, and the required pipeline and fluid data are comprehensive and easily obtainable. The dimensionless correlation obtained through fitting allows the model to adapt to different pipeline specifications, operating conditions, and fluid media, exhibiting good versatility and scalability, and providing a powerful analytical tool for optimizing precooling schemes and assessing safety risks.

[0020] In summary, this invention effectively overcomes the technical contradictions mentioned in the background technology, namely, the insufficient accuracy of one-dimensional models and the excessive computational cost of two-dimensional / three-dimensional CFD models, which make them unsuitable for long-distance pipelines. It provides a solution that achieves an excellent balance between computational cost and simulation accuracy, and is particularly suitable for simulation analysis and safety assessment of the pre-cooling process before commissioning of long-distance cryogenic liquid pipelines. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic flowchart of a 1.5-dimensional single-phase pipe flow heat transfer simulation method that takes gravity into account, provided by the present invention.

[0023] Figure 2 This is a schematic flowchart of an embodiment of a 1.5-dimensional single-phase pipe flow heat transfer simulation method considering gravity provided by the present invention.

[0024] Figure 3Mesh diagram of a 3D pipeline created using ANSYS Fluent software.

[0025] Figure 4 This is a schematic diagram of the feature-based grid discretization method.

[0026] Figure 5 This is a schematic diagram comparing the simulation results from ANSYS Fluent software with the simulation results from this invention.

[0027] Figure 6 This invention provides a structural schematic diagram of a 1.5-dimensional single-phase pipe flow heat transfer simulation system that takes gravity into account.

[0028] Figure 7 This is a schematic diagram of the structure of the electronic device provided by the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, embodiments of this invention, and should not be construed as limiting the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. In the description of this invention, it should be understood that the terminology used is for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] Figure 1 This is a flowchart illustrating a 1.5D single-phase pipe flow heat transfer simulation method considering gravity provided by the present invention. The execution subject of this 1.5D single-phase pipe flow heat transfer simulation method considering gravity can be any applicable terminal-side device or network-side device, such as a 1.5D single-phase pipe flow heat transfer simulation device considering gravity.

[0031] See Figure 1 and 2 The present invention provides a 1.5-dimensional single-phase pipe flow heat transfer simulation method considering gravity, which may include: S110. Obtain the pipeline data and fluid data of the target pipeline.

[0032] In this embodiment, the fluid is nitrogen, the target pipeline is made of austenitic stainless steel, the pipeline is 20km long, has an inner diameter of 0.4m, a wall thickness of 10mm, a roughness of 1×10-5m, and adopts a stacked insulation method. The inner insulation layer material is polyisocyanate, the outer insulation material is foam glass, and the ambient temperature is 10℃. The specific properties of the pipeline and insulation layer materials are shown in Table 1.

[0033] Table 1 LNG Pipeline Dimensions and Material Properties

[0034] S120. Based on pipeline data and fluid data, a three-dimensional computational fluid dynamics model is established to simulate dimensionless number data under multiple working conditions, and the top Nusselt number calculation formula and the bottom Nusselt number calculation formula are obtained by fitting.

[0035] This embodiment establishes a 100m 3D CFD pipeline model, and the mesh generation diagram is shown below. Figure 3 As shown, multiple operating conditions were simulated, including different inlet flow velocities (0.5 m / s, 1.0 m / s, 1.5 m / s) and different inlet nitrogen temperatures (-10℃, -50℃, -90℃, -130℃, -150℃). The Reynolds number was calculated using the pipe cross-sectional parameters, the average nitrogen parameters, the pipe top parameters, and the pipe bottom parameters. Re Prandtl numbers Pr Top Grashof number Gr top 、 Bottom Grashof number Gr down 、 Top Nusselt Nu top 、 Bottom Nusselt Nu down The expressions are shown in Equations (1) to (6) respectively. A total of 3200 sets of calculation results for each working condition and each pipe section along the line are shown in Table 2. Based on the data in Table 2, the calculation formulas for the top Nusselt number and the bottom Nusselt number are obtained by fitting using the least squares method, as shown in Equations (7) and (8). (1) (2) (3) (4) (5) (6) Table 2 Re , Pr , Gr top 、Gr down Nu top Nu down Calculation results

[0036] (7) (8) In the formula, ρ Fluid density, kg / m³ 3 ; v The fluid velocity is expressed in m / s. d The inner diameter of the pipe is in meters (m). μ The viscosity is the fluid dynamic viscosity, Pa·s; c Specific heat capacity of the fluid, J / (kg·℃); λ ν is the thermal conductivity of the fluid, W / (m·K); β The coefficient of volumetric thermal expansion is given in °C. -1 ; g The acceleration due to gravity is m / s². 2 ; T w,top The temperature of the inner wall at the top of the pipe cross-section, in °C; T The fluid temperature is expressed in °C. T w,down The temperature of the inner wall at the bottom of the pipe cross-section, in °C; h top The heat transfer coefficient of the inner wall at the top of the pipe cross-section is given in W / (m²). 2 ·℃); h down The heat transfer coefficient of the inner wall at the bottom of the pipe cross-section is given in W / (m²). 2 ·℃); q top The heat flux density at the top of the inner wall of the pipe is W / m. 2 ; q down The heat flux density at the bottom of the inner wall of the pipe is W / m. 2 .

[0037] S130. Combining the top and bottom Nusselt number calculation formulas, a 1.5-dimensional single-phase pipe flow heat transfer model considering gravity is established.

[0038] In this embodiment, equations (9) to (16) are combined to establish a 1.5-dimensional single-phase pipe flow heat transfer model that takes gravity into account.

[0039] (9) (10) (11) (12) (13) (14) (15) (16) In the formula, m The fluid mass flow rate is expressed in kg / s. A The cross-sectional area of ​​the pipe is in meters. 2 ; P The fluid pressure is expressed in Pa. h Enthalpy of the fluid, J / kg; f The coefficient of friction; ρ s The density of the pipe wall or insulation layer, kg / m³ 3 ; c s Specific heat capacity of the pipe wall or insulation layer, J / (kg·℃); λ s The value represents the thermal conductivity of the pipe wall or insulation layer, in W / (m·K); subscripts 1 and 2 represent the parameters of adjacent pipe walls or insulation layers, respectively. t For time, x Let be the distance from the discretized node of the pipeline to the starting point, in meters. G Let m be the height of the node after the pipeline is discretized; Nu top The top Nusselt number; Nu down The bottom Nusselt number; T W The pipe wall temperature is K; r Let be the distance from the radially discretized node to the axis, in meters (m). T f Let K be the fluid temperature.

[0040] S140. Based on a 1.5-dimensional single-phase pipe flow heat transfer model, the target pipe is discretized and the time step is confirmed. The fluid data at each discrete node is solved, and the temperature of the bottom wall, top wall and insulation layer of the pipe is solved based on the fluid data at each discrete node until the calculation within the simulation time is completed.

[0041] This embodiment first discretizes the target pipe, determines the time step according to the Courant criterion, and uses the method of characteristics to solve for the fluid parameters at each discrete node in the pipe based on equations (9), (10), (11), (13) and the initial state inside the pipe (the discrete grid of the method of characteristics is as follows). Figure 4 As shown), the simplified characteristic line equations include: Left characteristic line equation (along) ): , The equation of the right characteristic line (along) ): , Material characteristic line equation (along) ): , By taking the difference along the characteristic line, we get: , , , in: , In the formula, subscript A represents the fluid data at point A; subscript G represents the fluid data at point G; subscript H represents the fluid data at point H; and subscript M represents the fluid data at point M. a s Let be the speed of sound in the fluid, in m / s; t Let be the time step, in seconds; x Let m be the spatial step size. θ The pipe inclination angle is expressed in degrees (°).

[0042] For intermediate discrete nodes, the temperature, pressure and mass flow rate at the node can be obtained by solving equations (20), (21) and (22) simultaneously using Euler's prediction and the golden section method; for boundary discrete points, the boundary conditions and corresponding characteristic equations can be solved by solving them simultaneously using Euler's prediction and the golden section method.

[0043] After obtaining the parameters of all nodes in the current time layer, the implicit difference method is used to discretize along the radial direction of the pipeline and solve equations (14), (15), and (16) to obtain the temperature of the pipe wall and insulation layer at the bottom of the pipeline. Then, based on equations (12), (14), (15), (16) and the parameters of the fluid inside the pipe, the implicit difference method is used to solve for the temperature of the pipe wall and insulation layer at the top of the pipe. This calculation is repeated until the calculation within the simulation time is completed.

[0044] Figure 5 This is a schematic diagram comparing the simulation results from ANSYS Fluent software with the simulation results from this embodiment. Figure 5 It can be seen that the 1.5D single-phase pipeline flow heat transfer simulation method considering gravity provided by this invention can simulate the temperature changes at the top and bottom of the pipeline well, and is basically consistent with the simulation results of ANSYS Fluent software. It has the characteristics of clear calculation process, simple method and fast calculation speed, which makes up for the deficiency of existing one-dimensional models that cannot consider gravity factors, and provides a calculation method for process design and simulation of precooling process of long-distance cryogenic liquid pipeline.

[0045] The following describes the 1.5-dimensional single-phase pipe flow heat transfer simulation system considering gravity provided by the present invention. The 1.5-dimensional single-phase pipe flow heat transfer simulation system considering gravity described below can be referred to in correspondence with the 1.5-dimensional single-phase pipe flow heat transfer simulation method considering gravity described above.

[0046] See Figure 6 The present invention provides a 1.5-dimensional single-phase pipe flow heat transfer simulation system that considers gravity, which may include: The data acquisition module is used to acquire pipeline data and fluid data of the target pipeline. The 3D computational fluid dynamics model building module is used to: build a 3D computational fluid dynamics model based on pipeline data and fluid data, simulate dimensionless number data under multiple working conditions, and fit the top Nusselt number calculation formula and the bottom Nusselt number calculation formula. The 1.5D single-phase pipe flow heat transfer model establishment module is used to: combine the top Nusselt number calculation formula and the bottom Nusselt number calculation formula to establish a 1.5D single-phase pipe flow heat transfer model that takes gravity into account. The simulation module is used to: discretize the target pipe and confirm the time step based on a 1.5-dimensional single-phase pipe flow heat transfer model, solve for the fluid data at each discrete node, and solve for the temperature of the bottom wall, top wall and insulation layer of the pipe based on the fluid data at each discrete node, until the calculation within the simulation time is completed.

[0047] Figure 7 An example is a schematic diagram of the physical structure of an electronic device, such as... Figure 7 As shown, the electronic device may include a processor 810, a communications interface 820, a memory 830, and a communication bus 840, wherein the processor 810, the communications interface 820, and the memory 830 communicate with each other via the communication bus 840. The processor 810 can call logical instructions in the memory 830 to execute the following steps: Acquire pipeline and fluid data for the target pipeline; Based on pipeline and fluid data, a three-dimensional computational fluid dynamics model was established to simulate dimensionless number data under multiple working conditions, and the top and bottom Nusselt number calculation formulas were obtained by fitting. By combining the top and bottom Nusselt number calculation formulas, a 1.5-dimensional single-phase pipe flow heat transfer model considering gravity is established. Based on a 1.5-dimensional single-phase pipe flow heat transfer model, the target pipe is discretized and the time step is confirmed. The fluid data at each discrete node is solved, and the temperatures of the bottom wall, top wall, and insulation layer of the pipe are calculated based on the fluid data at each discrete node until the calculation within the simulation time is completed.

[0048] Furthermore, the logical instructions in the aforementioned memory 830 can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0049] On the other hand, the present invention also provides a computer program product, the computer program product comprising a computer program, the computer program being able to be stored on a non-transitory computer-readable storage medium, and the computer program being executed by a processor, enabling the computer to perform the following steps: Acquire pipeline and fluid data for the target pipeline; Based on pipeline and fluid data, a three-dimensional computational fluid dynamics model was established to simulate dimensionless number data under multiple working conditions, and the top and bottom Nusselt number calculation formulas were obtained by fitting. By combining the top and bottom Nusselt number calculation formulas, a 1.5-dimensional single-phase pipe flow heat transfer model considering gravity is established. Based on a 1.5-dimensional single-phase pipe flow heat transfer model, the target pipe is discretized and the time step is confirmed. The fluid data at each discrete node is solved, and the temperatures of the bottom wall, top wall, and insulation layer of the pipe are calculated based on the fluid data at each discrete node until the calculation within the simulation time is completed.

[0050] In another aspect, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the following steps: Acquire pipeline and fluid data for the target pipeline; Based on pipeline and fluid data, a three-dimensional computational fluid dynamics model was established to simulate dimensionless number data under multiple working conditions, and the top and bottom Nusselt number calculation formulas were obtained by fitting. By combining the top and bottom Nusselt number calculation formulas, a 1.5-dimensional single-phase pipe flow heat transfer model considering gravity is established. Based on a 1.5-dimensional single-phase pipe flow heat transfer model, the target pipe is discretized and the time step is confirmed. The fluid data at each discrete node is solved, and the temperatures of the bottom wall, top wall, and insulation layer of the pipe are calculated based on the fluid data at each discrete node until the calculation within the simulation time is completed.

[0051] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0052] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A 1.5D single-phase pipe flow heat transfer simulation method considering gravity, characterized in that, include: Acquire pipeline and fluid data for the target pipeline; Based on pipeline and fluid data, a three-dimensional computational fluid dynamics model was established to simulate dimensionless number data under multiple working conditions, and the top and bottom Nusselt number calculation formulas were obtained by fitting. By combining the top and bottom Nusselt number calculation formulas, a 1.5-dimensional single-phase pipe flow heat transfer model considering gravity is established. Based on a 1.5-dimensional single-phase pipe flow heat transfer model, the target pipe is discretized and the time step is confirmed. The fluid data at each discrete node is solved, and the temperatures of the bottom wall, top wall, and insulation layer of the pipe are calculated based on the fluid data at each discrete node until the calculation within the simulation time is completed.

2. The 1.5D single-phase pipe flow heat transfer simulation method considering gravity according to claim 1, characterized in that, Pipeline data includes any one or any combination of the following: length, inner diameter, wall thickness, roughness, insulation method, insulation material, insulation thickness, and ambient temperature; fluid data includes fluid medium and physical property parameters.

3. The 1.5D single-phase pipe flow heat transfer simulation method considering gravity according to claim 2, characterized in that, Dimensionless numbers include any one of the following or any combination thereof: Reynolds number Re Prandtl numbers Pr Top Grashof number Gr top 、 Bottom Grashof number Gr down 、 Top Nusselt Nu top 、 Bottom Nusselt Nu down ;in, Reynolds number Re The expression is: ， Prandtl number Pr The expression is: ， Top Grashof number Gr top The expression is: ， Bottom Grashof number Gr down The expression is: ， Top Nusselt Nu top The expression is: ， Bottom Nusselt Nu down The expression is: ， In the formula, ρ For fluid density; v The fluid velocity; d This refers to the inner diameter of the pipe. μ For fluid dynamic viscosity; c Specific heat capacity of the fluid; λ The thermal conductivity of the fluid; β It is the coefficient of volumetric thermal expansion; g It is the acceleration due to gravity; T w,top The temperature of the inner wall at the top of the pipe cross-section; T For fluid temperature; T w,down The temperature of the inner wall at the bottom of the pipe cross-section; h top The heat transfer coefficient is the inner wall of the top section of the pipe. h down The heat transfer coefficient is the inner wall temperature at the bottom of the pipe cross-section. q top The heat flux density is the top of the inner wall of the pipe. q down The heat flux density is at the bottom of the inner wall of the pipe.

4. The 1.5D single-phase pipe flow heat transfer simulation method considering gravity according to claim 3, characterized in that, The formula for calculating the top Nusselt number is: ， The formula for calculating the bottom Nusselt number is: ， In the formula, Re The Reynolds number is... Pr For Prandtl numbers, Gr top Top Grashof number ，Gr down The base Grashof number, a 1. a 2. a 3. a 4. a 5 represents the fitting coefficient in the top Nusselt number calculation formula; b 1. b 2. b 3. b 4. b 5 represents the fitting coefficient in the calculation of the bottom Nusselt number.

5. The 1.5D single-phase pipe flow heat transfer simulation method considering gravity according to claim 4, characterized in that, The expressions for the 1.5D single-phase pipe flow heat transfer model include: ， ， ， ， ， ， ， ， In the formula, m This refers to the fluid mass flow rate. A This refers to the cross-sectional area of ​​the pipe. P For fluid pressure; h Enthalpy of the fluid; f The coefficient of friction; ρ s The density of the pipe wall or insulation layer; c s Specific heat capacity of the pipe wall or insulation layer; λ s This represents the thermal conductivity of the pipe wall or insulation layer; subscripts 1 and 2 represent the parameters of adjacent pipe walls or insulation layers, respectively. t For time, x This represents the distance from the discretized node of the pipeline to the starting point. G The height of the node after the pipeline is discretized; Nu top The top Nusselt number; Nu down The bottom Nusselt number; T W The pipe wall temperature is K; r This represents the distance from the radially discretized node to the axis. T f The fluid temperature.

6. The 1.5D single-phase pipe flow heat transfer simulation method considering gravity according to claim 5, characterized in that, The 1.5D single-phase pipe flow and heat transfer model discretizes the target pipe and confirms the time step, solves for the fluid data at each discrete node, and calculates the temperatures of the bottom and top pipe walls and the insulation layer based on the fluid data at each discrete node until the calculation within the simulation time is completed, including: The fluid data at each discrete node is obtained by using the method of characteristics. For intermediate discrete nodes, the fluid data at the node is obtained by combining Euler's prediction and the golden section method. For boundary discrete nodes, the fluid data at the node is obtained by combining the boundary conditions and Euler's prediction and the golden section method. Based on the fluid data at each discrete node, and using a 1.5-dimensional single-phase pipe flow heat transfer model, the implicit difference method is employed to discretize along the radial direction of the pipe, and the temperatures of the bottom wall, top wall, and insulation layer of the pipe are solved.

7. The 1.5D single-phase pipe flow heat transfer simulation method considering gravity according to claim 6, characterized in that, The expressions for the method of characteristics include: Equation of the left characteristic line: ， Equation of the right characteristic line: ， Material characteristic line equations: ， By taking the difference along the characteristic line, we get: ， ， ， in: ， In the formula, subscript A represents the fluid data at point A; subscript G represents the fluid data at point G; subscript H represents the fluid data at point H; and subscript M represents the fluid data at point M. a s The speed of sound in the fluid; t For time step; x For spatial step size, θ This refers to the pipe inclination angle.

8. A 1.5-dimensional single-phase pipe flow heat transfer simulation system considering gravity, characterized in that, include: The data acquisition module is used to acquire pipeline data and fluid data of the target pipeline. The 3D computational fluid dynamics model building module is used to: build a 3D computational fluid dynamics model based on pipeline data and fluid data, simulate dimensionless number data under multiple working conditions, and fit the top Nusselt number calculation formula and the bottom Nusselt number calculation formula. The 1.5D single-phase pipe flow heat transfer model establishment module is used to: combine the top Nusselt number calculation formula and the bottom Nusselt number calculation formula to establish a 1.5D single-phase pipe flow heat transfer model that takes gravity into account. The simulation module is used to: discretize the target pipe and confirm the time step based on a 1.5-dimensional single-phase pipe flow heat transfer model, solve for the fluid data at each discrete node, and solve for the temperature of the bottom wall, top wall and insulation layer of the pipe based on the fluid data at each discrete node, until the calculation within the simulation time is completed.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the 1.5-dimensional single-phase pipe flow heat transfer simulation method considering gravity as described in any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the 1.5-dimensional single-phase pipe flow heat transfer simulation method considering gravity as described in any one of claims 1 to 7.

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