Container modeling method, system and equipment based on two fluids and six equations and medium

Abstract

The invention discloses a container modeling method, system and equipment based on two-fluid six equations and a medium, and the method comprises the steps: simplifying a container into a pipeline model with a hot component described by adopting the two-fluid six equations, and carrying out the modeling of a transverse connection pipe of the side wall of the container at the connection part of adjacent control bodies of the pipeline through a multi-pass principle; adding an internal heat source item in a vapor-liquid energy equation of the container control model to realize modeling of an electric heating element; extracting an electric heating element power control interface and fluid interfaces of a top connecting pipe, a bottom connecting pipe and a transverse side wall connecting pipe, and integrating the fluid area model, the thermal component model and the electric heating element model of the container to be packaged into a container assembly model with a plurality of fluid interfaces and control interfaces; and connecting the container model with other thermal hydraulic components and controller components to construct a simulation system. Under the framework of a two-fluid six-equation system, modularization, reusability and expandability of the container model are achieved.

Description

Technical Field

[0001] The present application relates to the technical field of container modeling and simulation, and in particular to a container modeling method, system, equipment and medium based on two-fluid six equations. Background Art

[0002] Steam-water two-phase thermal hydraulic systems are common process systems in pressurized water reactors (PWRs) and thermal power plants. These systems are generally mathematically modeled using a two-fluid six-equation system, which accurately simulates the mass and heat transfer behavior of the vapor-liquid two-phase system under both normal operating and emergency conditions. Vessels are common equipment in thermal hydraulic systems, such as safety injection tanks, emergency water tanks, deaerators, pressurizers, and accumulators. Their function is to store fluid at a certain pressure and temperature, providing a stable fluid source or pressure buffer for the thermal hydraulic system. Vessels are generally thermal hydraulic components with vapor-liquid stratification and several fluid inlet and outlet pipes. They share the same thermal hydraulic characteristics as steam-water two-phase pipelines, but also experience physical processes such as flash evaporation, condensation, and hot and cold mixing caused by liquid level changes or fluid ingress and egress. Furthermore, they must dissipate heat from the vessel walls and heat the fluid working medium by the vessel's electric heating elements.

[0003] Within the framework of a two-fluid six-equation system, the question is how to construct a modular, reusable, and scalable container model that can be applied to both cases where the vapor space is non-condensable gas and the liquid space is subcooled water, as well as cases where the vapor space is saturated steam and the liquid space is saturated water. Furthermore, the model can simulate the changes in the container's thermal-hydraulic parameters, such as pressure, temperature, and liquid level, as fluids enter and exit the container through pipes. Simultaneously, the model can simulate the heat dissipation from the container walls and the heating of the subcooled or saturated water in the liquid space by the container's electric heating elements. These are pressing issues that need to be addressed for high-precision simulation of the operational characteristics of steam-water two-phase thermal-hydraulic systems containing containers, and for demonstrating the influence of container structural parameters on key parameters of thermal-hydraulic systems. Summary of the Invention

[0004] In view of this, the present application provides a container modeling method, system, equipment and medium based on two-fluid six-equation system. Under the framework of the two-fluid six-equation system, the modularity, reusability and extensibility of the container model are realized. It is applicable to the situation where the steam space is non-condensable gas and the liquid space is supercooled water, and it is also applicable to the situation where the steam space is saturated steam and the liquid space is saturated water. It can also simulate the changes in the thermal-hydraulic parameters such as pressure, temperature, liquid level of the container after the fluid enters and exits the container through the pipe, providing reliable support for the modeling and simulation of the steam-water two-phase thermal-hydraulic system.

[0005] This application discloses a container modeling method based on two-fluid six equations, comprising the following steps:

[0006] Step 1: Simplify the container into a pipe model with a thermal component described by two fluids and six equations. The inlet fluid interface of the pipe model serves as the bottom pipe of the container, the outlet fluid interface of the pipe model serves as the top pipe of the container, and the thermal component serves as the solid wall of the container.

[0007] Step 2: Based on the axial distribution of the transverse nozzles on the side wall of the container, divide the container fluid area into nodes in the axial direction so that the transverse nozzles on the side wall of the container at different elevations correspond to different connections between two adjacent control bodies;

[0008] Step 3: Divide the container thermal component area into axial blocks and radial nodes, so that the thermal component axial blocks correspond to the control volume one by one, and the solid wall layer and insulation layer of the container thermal component area belong to different radial nodes;

[0009] Step 4: Model the container side wall transverse pipes at the connection points of adjacent control bodies corresponding to the transverse pipes using the multi-pass model principle. The container side wall transverse pipes are connected to the external thermal hydraulic system through fluid interfaces.

[0010] Step 5: Model the container heating element by adding a heat source term to the discretized vapor-liquid energy equation on the control volume. Determine the power of the newly added internal heat source term in the discretized vapor phase energy equation and liquid phase momentum equation for each control volume based on the height of the heating element from the bottom of the container and the cavitation fraction of the control volume.

[0011] Step 6: Use the third-class boundary to model the heat dissipation of the container's thermal components, set the ambient temperature of the container and the heat transfer coefficient between the container's outer wall and the environment;

[0012] Step 7: Extract the control interface for the power control of the container's electric heating element and the fluid interfaces of the bottom pipe, top pipe, and side wall transverse pipe of the container model, integrate and encapsulate the fluid area model, thermal component model, and electric heating element model of the container model, and encapsulate them into a container component model with several fluid interfaces and control interfaces.

[0013] Step 8: Connect the constructed container component model with other thermal-hydraulic component models such as pipeline models, valve models, pump models, and pipeline accessory models based on the two-fluid six-equation method to build a simulation system to simulate the changes in thermal-hydraulic parameters such as container pressure, temperature, and liquid level after the fluid enters and exits the container through the pipe under different initial conditions.

[0014] In a specific embodiment of the present application, the container is simplified into a pipeline model with a thermal component using Modelica as the modeling language, which includes a main equation model, a constitutive equation model and a physical property equation model of the fluid area and a heat conduction equation model and a thermal boundary model of the thermal component area.

[0015] In one embodiment of the present application, the main equation model includes mass equations, momentum equations, energy equations, and non-condensable gas equations for the vapor and liquid phases. The constitutive equation model includes wall friction equations, wall heat transfer equations, interface friction equations, interface heat transfer equations, and interface mass exchange equations. The physical property equation model utilizes the standard formulas for water and water vapor physical properties (IAPWS-97) to obtain physical property parameters such as density, thermal conductivity, viscosity, and specific heat at constant pressure, which are then used by the main equation model and the constitutive equation model.

[0016] In one specific embodiment of the present application, the fluid region is divided into nodes using a staggered grid, with control volume models and nozzle models appearing alternately. The control volume model is a primary control volume bounded by adjacent nodes, while the nozzle model is a secondary control volume bounded by the centers of adjacent primary control volumes. The control volume model models and calculates the mass and energy equations for the vapor and liquid phases, while the nozzle model models and calculates the momentum equations for the vapor and liquid phases. The control volume model and nozzle model perform coupled iterations to complete the six-equation calculations for the two fluids.

[0017] In a specific embodiment of the present application, for a vertical container, the bottom of the container is taken as the elevation zero point, and the elevation of the transverse pipe of the container side wall is the horizontal distance between the transverse pipe of the container side wall and the bottom of the container; for a horizontal container, the container inlet is taken as the bottom of the container and the elevation zero point, and the elevation of the transverse pipe of the container side wall is the horizontal distance between the transverse pipe of the container side wall and the bottom of the container.

[0018] In a specific embodiment of the present application, the implementation method 1 of the container fluid region node division method includes the following steps:

[0019] Step 1-1: Set the total number of nodes for the container node division based on modeling requirements. This total number of nodes must be greater than the number of transverse nozzles on the container sidewalls. If the container has no transverse nozzles, simply divide the container evenly according to the total number of nodes required.

[0020] Step 2-1: Create an elevation array that includes all container sidewall transverse nozzles. The array's cell data is arranged from smallest to largest. The cell data in the elevation array are all unique and duplicates should be removed. That is, if several container sidewall transverse nozzles have the same elevation, they will be mapped to only one corresponding cell data in the elevation array.

[0021] Step 3-1: Divide the container into nodes according to the elevation array obtained in step 2-1, and divide the container into several blocks, so that the elevation of the connection between two adjacent blocks from the bottom of the container corresponds one-to-one with the unit data of the elevation array.

[0022] Step 4-1: Further perform node division on the nodes divided in step 3-1, and divide each node into several control bodies. The lengths of the control bodies in the same node are equal, so that the total number of control bodies is equal to the total number of nodes required to divide the container, and the length of each control body is as close as possible to the ratio of the container height to the total number of nodes required to divide, that is, the average length of the control body.

[0023] Step 5-1: According to the correspondence between the transverse connecting pipe of the container side wall and the elevation array unit data, mark the correspondence between the transverse connecting pipe of the container side wall and the connection between two adjacent control bodies.

[0024] In a specific embodiment of the present application, the implementation method 2 of the container fluid region node division method includes the following steps:

[0025] Step 1-2: According to the modeling requirements, set the total number of nodes for the container node division. The total number of nodes must be greater than the number of lateral pipes on the container side wall.

[0026] Step 2-2: Divide the container evenly according to the total number of nodes, take the bottom of the container as the elevation zero point, and obtain an elevation array including the connection points of all two adjacent control bodies in the container, named array A;

[0027] Step 3-2: Create an array containing the elevations of all container sidewall transverse nozzles, named Array B. The cell data in Array B is arranged from smallest to largest. The cell data in Array B are all unique and duplicates should be removed. That is, if several container sidewall transverse nozzles have the same elevation, they will be mapped to only one corresponding cell in Array B.

[0028] Step 4-2: Using the first element B.1 in array B as a reference, locate element A.1 in array A where the absolute difference between A.1 and B.1 is the smallest among all elements in array A. Update array A, modify A.1 to equal B.1, and annotate element A.1 to correspond to element B.1 in array B.

[0029] Step 5-2: Using cell B.2 in array B as a reference, locate cell A.2 in array A. Among all the cells in array A, excluding the already labeled cells, the absolute difference between A.2 and B.2 is the smallest. Update array A, modify A.2 to equal B.2, and label cell A.2 to correspond to cell B.2 in array B.

[0030] Step 6-2: Repeat step 5-2 until all the cell data in array B are matched and labeled with the cell data in array A.

[0031] Step 7-2: Based on the array A obtained in step 6-2, re-divide the nodes of the container so that the elevation of the connection between two adjacent control bodies corresponds one-to-one with the unit data of array A. Based on the correspondence between the horizontal connecting pipes of the container side walls and array B, and the correspondence between array B and array A, mark the correspondence between the horizontal connecting pipes of the container side walls and the connection between two adjacent control bodies.

[0032] In a specific embodiment of the present application, the multi-pass model principle includes the following steps:

[0033] Steps 1-3: Model all vessel sidewall lateral nozzles using a control volume based on the two-fluid six-equation model. The flow area of the control volume model is equal to the flow area of the lateral nozzle, the hydraulic equivalent diameter of the control volume model is equal to the inner diameter of the lateral nozzle, and the length of the control volume model is equal to the length of the lateral nozzle. One end of the control volume model is connected to the external thermal-hydraulic system via a fluid interface, and the other end is connected to the vessel control volume.

[0034] Step 2-3: Based on the corresponding annotations between the vessel sidewall transverse nozzle and the connection points between two adjacent control bodies, identify the vessel control body connected to the vessel sidewall transverse nozzle. Connect the control body model of the vessel sidewall transverse nozzle to the vessel control body model using a nozzle model. Then, connect the inlet or outlet of the vessel control body model to several nozzle models.

[0035] Step 3-3: Establish constraints for the nozzle models connected to the same vessel control volume model. By summing the fluid mass and energy transport terms for each nozzle model, the total mass and energy of the control volume model can be maintained to meet conservation requirements. For the nozzle model, calculate the vapor-liquid flow rate and fluid momentum based on the upstream and downstream control volume pressure differentials and thermal-hydraulic state parameters.

[0036] In a specific embodiment of the present application, the container electric heating element is to add an internal heat source term Q to the vapor-liquid energy equation. g and Q f Modeling is carried out, and the internal heat source term Q is added to the discrete vapor-liquid energy equation g and Q f The calculation method is:

[0037] Step 1-4: Determine the power weight of the container control body model based on the length of the electric heating element. When the elevations of the upper and lower boundaries of the control body from the bottom of the container are both less than the length of the electric heating element, the control body power weight factor N is:

[0038]

[0039] Among them, H1 is the lower boundary elevation of the control body, H2 is the upper boundary elevation of the control body, and L cis the length of the control body, L t is the length of the heating element.

[0040] When the elevations of the upper and lower boundaries of the control body from the bottom of the container are both less than the length of the electric heating element, the power weight factor N of the control body is 0.

[0041] When the elevation of the upper boundary of the control body from the bottom of the container is greater than the length of the electric heating element, and the elevation of the lower boundary from the bottom of the container is less than the length of the electric heating element, the power weight factor N of the control body is:

[0042]

[0043] Step 2-4: For the vertical container, calculate the internal heat source term added to the vapor-liquid energy equation after the control volume is discretized:

[0044]

[0045]

[0046] Among them, Q g Add an internal heat source term to the vapor phase energy equation after the control volume is discretized, Q f The internal heat source term is added to the liquid phase energy equation after the control volume is discretized. Q is the power of the electric heating element, and Q max is the rated power of the heating element, is the power factor of the electric heating element, α g is the vapor phase cavitation fraction, α f is the liquid phase fraction.

[0047] For horizontal containers, the internal heat source term added to the vapor-liquid energy equation after the control volume is discretized is:

[0048] Q g =0 Formula 5

[0049]

[0050] In one specific embodiment of the present application, the axial segmentation of the container thermal component region is consistent with the control volume segmentation of the fluid region, including the number and length distribution of the thermal component axial segments, ensuring a one-to-one correspondence between the thermal component axial segments and the control volume. Simultaneously, the container thermal component region is radially segmented into nodes based on the radial dimensions of the solid wall layer and the insulation layer of the container thermal component region. This not only assigns the solid wall layer and the insulation layer of the container thermal component region to different radial nodes, but also sets the number of nodes and material properties of each layer, ensuring that both the solid wall layer and the insulation layer have multiple nodes for temperature distribution analysis.

[0051] In a specific embodiment of the present application, the outer wall of the insulation layer and the external environment adopt the third type of thermal boundary conditions, that is, the heat flux density q between the thermal component of the container and the external environment is out :

[0052]

[0053] Among them, r out is the diameter of the outer wall of the container insulation layer, λ is the thermal conductivity of the insulation layer, h out is the heat transfer coefficient between the outer wall of the insulation layer and the external environment, T wout is the outer wall temperature of the insulation layer, T env is the external ambient temperature.

[0054] In a specific embodiment of the present application, the method for initializing the thermal-hydraulic parameters of the container model includes the following steps:

[0055] Step 1-5: Define the initial pressure P0, initial temperature T0, initial liquid level H0 and initial non-condensable gas fraction X of the container model n0 ;

[0056] Step 2-5: According to the initial pressure P0 and initial liquid level H0 of the container, the initial temperature T0 and the initial fraction of non-condensable gas X defined in step 1-5 are calculated. n0 Automatic verification is performed, including the following situations:

[0057] Case A: When the initial liquid level H0 of the container is equal to the full liquid level of the container (that is, the initial liquid level is equal to the height inside the container), first check the initial temperature T0. If the defined initial temperature T0 is less than or equal to the saturation temperature T corresponding to the initial pressure P0 of the container, s0 , the initial temperature T0 is not adjusted; if the defined initial temperature T0 is greater than the saturation temperature T corresponding to the container pressure s0 , it will automatically adjust to the saturation temperature T s0 .

[0058] Then check the initial fraction of non-condensable gas X n0 for:

[0059]

[0060] Among them, P s (T0) is the saturation pressure corresponding to the initial temperature T0.

[0061] Case B: When the initial liquid level H0 of the container is equal to 0, first check the initial fraction of non-condensable gas X n0 , X n0 Should meet the following requirements:

[0062]

[0063] Among them, P s (T env ) is the ambient temperature T env (Generally, the value is 20℃) The corresponding saturation pressure. When the initial fraction of non-condensable gas defined is X n0 When formula 9 is satisfied, X n0 No adjustment is made; when X n0 When formula 9 is not satisfied, X n0 Automatically adjust to:

[0064]

[0065] Then check the defined initial temperature T0, which should satisfy:

[0066] T0≥T s (P gs0 )=T s (P0(1-X n0 )) Formula 11

[0067] Among them, P gs0 is the partial pressure of the container vapor, T s (P gs0 ) is the saturation temperature corresponding to the steam partial pressure. When the defined initial temperature T0 satisfies formula (11), that is, T0 is greater than or equal to the initial steam partial pressure P of the container g0 When the corresponding saturation temperature is reached, the defined initial temperature T0 is not adjusted. When the defined initial temperature T0 does not satisfy formula (11), T0 is automatically adjusted to:

[0068] T0=T s (P gs0 )=T s (P0(1-X n0 )) Formula 12

[0069] Case C: When the initial liquid level H0 of the container is between 0 and the full level, first check the defined initial temperature T0. If the defined initial temperature T0 is less than or equal to the saturation temperature T corresponding to the initial pressure P0 of the container, s0 , the initial temperature T0 will not be adjusted temporarily; if the defined initial temperature T0 is greater than the saturation temperature T corresponding to the container pressure s0 , it will automatically adjust to the saturation temperature T s0 .

[0070] Then check the initial fraction of non-condensable gas X n0 , X n0 Should meet the following requirements:

[0071]

[0072] Among them, P s(T0) is the saturation pressure corresponding to the initial temperature T0. When the initial fraction of non-condensable gas X n0 When formula (13) is satisfied, X n0 No adjustment is made; when X n0 When formula (13) is not satisfied, X n0 Automatically adjust to:

[0073]

[0074] Finally, the defined initial temperature T0 is checked and automatically adjusted to:

[0075] T0=T s (P gs0 )=T s (P0(1-X n0 Formula 15

[0076] Step 3-5: Based on the calibrated initial pressure P0, initial temperature T0, initial liquid level H0 and initial fraction of non-condensable gas X n0 Assign values to the initial parameters of the control body model and takeover model of the container. The assignment rules are as follows:

[0077] a. The initial values of the liquid and vapor flow rates of the container takeover model are both 0.

[0078] b. Initial pressure P of the control body model t0 are equal to the initial pressure P0 of the container.

[0079] c. Initial temperature of vapor phase of control body model T cg0 Both are:

[0080] T cg0 =max(T s (P0(1-X n0 )), T0) Formula 16

[0081] Among them, max() refers to the maximum value, T s (P0(1-X n0 )) is the saturation temperature corresponding to the steam partial pressure.

[0082] d. Initial temperature T of the liquid phase of the control body model cf0 Both are:

[0083] T cf0 =min(T s (P0(1-X n0 )), T0) Formula 17

[0084] Among them, min() refers to the minimum value.

[0085] e. When the container is a vertical container, the initial cavitation fraction α of the control body model cg0 for:

[0086]

[0087] Among them, H1 is the lower boundary elevation of the control body, and H2 is the upper boundary elevation of the control body.

[0088] When the container is a horizontal container, the initial cavitation fraction α of the control body model cg0 Both are:

[0089]

[0090] Where d is the inner diameter of the horizontal container.

[0091] In a specific embodiment of the present application, the container model electric heating element is connected to the external controller model through a control interface, the parameter transmitted is the electric heating element power factor, and the data transmitted is in the form of an analog value from 0 to 1. The electric heating element power factor transmitted through the control interface is then transmitted to the container thermal component area modeling module. The container thermal component area modeling module calculates the electric heating element power calculation result and transmits it to the newly added internal heat source term of the control body vapor-liquid energy equation for related energy equation calculation.

[0092] In a specific embodiment of the present application, the bottom pipe, top pipe and side wall transverse pipe of the container model are connected to other thermal-hydraulic component models based on two-fluid six equations through fluid interfaces. The transmitted parameters include pressure, cavitation fraction, vapor-liquid flow rate, vapor-liquid internal energy ratio, non-condensable gas fraction, etc., to realize the combination of the main equations of the container model and the main equations of other thermal-hydraulic component models.

[0093] The present application also discloses a container modeling system based on two-fluid six-equation method, comprising:

[0094] The container node division module is used to divide the container fluid area into several control bodies and connecting pipes in the form of a staggered grid, and the transverse connecting pipes of the container side walls at different elevations correspond to different adjacent control body connections; it is used to axially divide the container thermal component area into several blocks, and the division form is consistent with the control body division of the fluid area, so that each thermal component block corresponds to a control body; at the same time, the radial nodes of the container thermal component area are divided according to the container solid wall layer and the possible insulation layer, so that the container solid wall layer and the insulation layer belong to different radial nodes.

[0095] The container fluid region modeling and initialization module is used to construct the main fluid region equation model, constitutive closed-form equation model, and physical property equation model based on the two-fluid six equations. It is then discretized and solved according to the container's node partitioning. It also defines and verifies the initialization parameters of the container fluid region and initializes the variables of each control volume and nozzle based on these verified initialization parameters.

[0096] The container thermal component area modeling module is used to construct the heat conduction equation model and thermal boundary model of the container thermal component area.

[0097] The container electric heating element modeling module is used to add the electric heating element heat source term to the container control volume vapor-liquid energy equation, and accepts the parameters of the control interface as the electric heating element power factor to calculate the electric heating element power, which is applied to the newly added internal heat source term in the control volume vapor-liquid energy equation.

[0098] The container model encapsulation module is used to construct the fluid interfaces of the bottom pipe, top pipe and side wall lateral pipe of the container model and the control interface of the electric heating element. It integrates the fluid area model, thermal component model and electric heating element model of the encapsulated container model to form a container component model with several fluid interfaces and control interfaces.

[0099] The container model application module is used to connect the constructed container model with other thermal hydraulic component models such as pipeline models based on two fluids and six equations, valve models, pipeline accessory models, and hungry controller models for electric heating element power control, to build a simulation system, simulate the changes in the container's thermal hydraulic parameters such as pressure, temperature, and liquid level after the fluid enters and exits the container through the pipe, and simulate the heat dissipation process of the container side wall and the heating process of the container electric heating element on the supercooled water or saturated water in the liquid space.

[0100] The present application also discloses a computer device comprising at least a processor and a readable storage medium. The readable storage medium stores a computer program that, when executed by the processor, implements the above-mentioned container modeling method based on two fluids and six equations.

[0101] In a fourth aspect, the present application provides a computer-readable storage medium having computer executable instructions stored thereon. When the executable instructions are executed by a processor, the above-mentioned container modeling method based on two fluids and six equations is implemented.

[0102] In a fifth aspect, the present application provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the above-mentioned container modeling method based on two fluids and six equations.

[0103] Due to the adoption of the above-mentioned technical solution, the present application has the following advantages: within the framework of the two-fluid six-equation system, the modularity, reusability and extensibility of the container model are realized, which is applicable not only to the case where the steam space is non-condensable gas and the liquid space is supercooled water, but also to the case where the steam space is saturated steam and the liquid space is saturated water. It can also simulate the changes in the thermal-hydraulic parameters such as pressure, temperature, and liquid level of the container after the fluid enters and exits the container through the pipe, providing reliable support for the modeling and simulation of the steam-water two-phase thermal-hydraulic system. BRIEF DESCRIPTION OF THE DRAWINGS

[0104] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0105] Figure 1 A schematic diagram of a container modeling process based on two fluids and six equations according to an embodiment of the present application;

[0106] Figure 2 This is a schematic diagram of the topological structure of the container fluid area after node division in an embodiment of the present application;

[0107] Figure 3 This is a schematic diagram of the axial segment division and radial node division of the container thermal component area in an embodiment of the present application;

[0108] Figure 4 This is a schematic diagram of the principle of multiple transverse pipes on the side wall of a container according to an embodiment of the present application;

[0109] Figure 5 This is a logic diagram for defining and automatically checking the thermal hydraulic initialization parameters of a container according to an embodiment of the present application;

[0110] Figure 6 This is a schematic diagram of a vertical container model icon of an embodiment of the present application;

[0111] Figure 7 This is a schematic diagram of a horizontal container model icon according to an embodiment of the present application;

[0112] Figure 8 This is an architecture diagram of a container modeling system based on two fluids and six equations according to an embodiment of the present application. DETAILED DESCRIPTION

[0113] In order to provide a clearer understanding of the technical features, objectives, and effects of this application, the basic implementation principles of this application are now described. It should be understood that the specific implementation principles described herein are only used to explain this application and are not intended to limit this application. Based on the implementation principles of this application, all other implementation cases obtained by those skilled in the art without making any creative efforts are within the scope of protection of this application.

[0114] 1. Vessel modeling method based on two-fluid six-equation

[0115] like Figure 1 As shown, at least one embodiment of the present application provides a container modeling method based on two fluids and six equations. The container modeling method can be applied to the Modelica language and includes the following steps:

[0116] Step 1: Simplify the container into a pipe model with a thermal component described by two fluids and six equations. The inlet fluid interface of the pipe model serves as the bottom pipe of the container, the outlet fluid interface of the pipe model serves as the top pipe of the container, and the thermal component serves as the solid wall of the container.

[0117] Step 2: According to the axial distribution of the transverse pipes on the side wall of the container, divide the axial node of the container fluid area so that the transverse pipes on the side wall of the container with different elevations correspond to different adjacent control body connections, such as Figure 2 As shown;

[0118] Step 3: Divide the container thermal component area into axial blocks and radial nodes, so that the thermal component axial blocks correspond to the control body one by one, and the solid wall layer and insulation layer of the container thermal component area belong to different radial nodes, such as Figure 3 As shown;

[0119] Step 4: Model the container side wall transverse pipe using the multi-pass model principle at the connection point of the adjacent control body corresponding to the transverse pipe. The container side wall transverse pipe is connected to the external thermal hydraulic system through a fluid interface, such as Figure 4 As shown;

[0120] Step 5: Model the container heating element by adding a heat source term to the discretized vapor-liquid energy equation on the control volume. Determine the power of the newly added internal heat source term in the discretized vapor phase energy equation and liquid phase momentum equation for each control volume based on the height of the heating element from the bottom of the container and the cavitation fraction of the control volume.

[0121] Step 6: Use the third-class boundary to model the heat dissipation of the container's thermal components, set the ambient temperature of the container and the heat transfer coefficient between the container's outer wall and the environment;

[0122] Step 7: Extract the control interface of the power control of the container electric heating element and the fluid interfaces of the bottom pipe, top pipe and side wall lateral pipe of the container model, integrate and encapsulate the fluid region model, thermal component model and electric heating element model of the container model, and encapsulate it into a container component model with several fluid interfaces and control interfaces, such as Figure 6 and Figure 7 As shown;

[0123] Step 8: Connect the constructed container component model with other thermal-hydraulic component models such as pipeline models, valve models, pump models, and pipeline accessory models based on the two-fluid six-equation method to build a simulation system to simulate the changes in thermal-hydraulic parameters such as container pressure, temperature, and liquid level after the fluid enters and exits the container through the pipe under different initial conditions.

[0124] 1. Container fluid area modeling

[0125] (1) Pipeline model based on two-fluid six-equation

[0126] This application is based on the Modelica language and models the container fluid area as a pipeline model based on the two-fluid six-equation model. The two-fluid six-equation model takes into account the different physical properties, flow rates, temperatures of the two-phase fluids in the actual two-phase fluid flow process, as well as the mass, energy and momentum exchange between the two phases, that is, the mass, momentum and energy conservation equations are established for the vapor phase and the liquid phase respectively. In order to make the control equation group closed, it is necessary to add closed constitutive equations such as phase interface friction, phase interface heat transfer, phase interface mass exchange, wall friction, and wall heat transfer. The basic form of the two-fluid six-equation is as follows:

[0127] The gas-liquid mass conservation equation is:

[0128]

[0129] The gas-liquid energy conservation equation is:

[0130]

[0131] The gas-liquid momentum conservation equation is:

[0132]

[0133] Non-condensable gas equation:

[0134]

[0135] Wherein, subscript k represents gas or liquid (subscript g for gas and f for liquid); i represents gas-liquid interface; w represents wall; α k is the volume percentage; ρ k is the density; V k is the flow rate, U kis the internal energy; A is the flow area; P is the pressure; Γ k is the amount of material exchange at the phase interface; Γ ik is the amount of material exchange at the interface in the mainstream region; Γ wk is the amount of material exchange at the interface of the wall thermal boundary layer; Q wk is the heat transfer from the wall; Q ik Q is the heat transfer at the phase interface; k A new internal heat source item corresponding to the container heating element; is the interface enthalpy in the mainstream area; h′ k is the enthalpy of the thermal boundary layer interface on the wall; DISS is the energy dissipation term; B x is the volume force; V ik is the interfacial flow velocity; F wk is the wall friction; F ik is the interfacial friction; F Lk is the local flow pressure loss; F Nk is the virtual mass force.

[0136] (2) Node division of container fluid area

[0137] The topological structure after the node division of the container fluid area is as follows Figure 2 As shown, a staggered grid is used, with control volumes and nozzles appearing alternately. The control volume model is a primary control volume bounded by adjacent nodes, while the nozzle model is a secondary control volume bounded by the center of the adjacent primary control volume. The control volume model models and calculates the mass and energy equations for the vapor and liquid phases, while the nozzle model models and calculates the momentum equations for the vapor and liquid phases. The control volume model and nozzle model perform coupled iterations to complete the six-equation calculation for the two fluids.

[0138] The container fluid area node division method includes the following two implementation methods:

[0139] Implementation method 1 includes the following steps:

[0140] Step 1-1: Set the total number of nodes for the container node division based on modeling requirements. This total number of nodes must be greater than the number of transverse nozzles on the container sidewalls. If the container has no transverse nozzles, simply divide the container evenly according to the total number of nodes required.

[0141] Step 2-1: Create an elevation array that includes all container sidewall transverse nozzles. The array's cell data is arranged from smallest to largest. The cell data in the elevation array are all unique and duplicates should be removed. That is, if several container sidewall transverse nozzles have the same elevation, they will be mapped to only one corresponding cell data in the elevation array.

[0142] Step 3-1: Divide the container into nodes according to the elevation array obtained in step 2-1, and divide the container into several blocks, so that the elevation of the connection between two adjacent blocks from the bottom of the container corresponds one-to-one with the unit data of the elevation array.

[0143] Step 4-1: Further perform node division on the nodes divided in step 3-1, and divide each node into several control bodies. The lengths of the control bodies in the same node are equal, so that the total number of control bodies is equal to the total number of nodes required to divide the container, and the length of each control body is as close as possible to the ratio of the container height to the total number of nodes required to divide, that is, the average length of the control body.

[0144] Step 5-1: According to the correspondence between the transverse connecting pipe of the container side wall and the elevation array unit data, mark the correspondence between the transverse connecting pipe of the container side wall and the connection between two adjacent control bodies.

[0145] Implementation method 2 includes the following steps:

[0146] Step 1-2: According to the modeling requirements, set the total number of nodes for the container node division. The total number of nodes must be greater than the number of lateral pipes on the container side wall.

[0147] Step 2-2: Divide the container evenly according to the total number of nodes, take the bottom of the container as the elevation zero point, and obtain an elevation array including the connection points of all two adjacent control bodies in the container, named array A;

[0148] Step 3-2: Create an array containing the elevations of all container sidewall transverse nozzles, named Array B. The cell data in Array B is arranged from smallest to largest. The cell data in Array B are all unique and duplicates should be removed. That is, if several container sidewall transverse nozzles have the same elevation, they will be mapped to only one corresponding cell in Array B.

[0149] Step 4-2: Using the first element B.1 in array B as a reference, locate element A.1 in array A where the absolute difference between A.1 and B.1 is the smallest among all elements in array A. Update array A, modify A.1 to equal B.1, and annotate element A.1 to correspond to element B.1 in array B.

[0150] Step 5-2: Using cell B.2 in array B as a reference, locate cell A.2 in array A. Among all the cells in array A, excluding the already labeled cells, the absolute difference between A.2 and B.2 is the smallest. Update array A, modify A.2 to equal B.2, and label cell A.2 to correspond to cell B.2 in array B.

[0151] Step 6-2: Repeat step 5-2 until all the cell data in array B are matched and labeled with the cell data in array A.

[0152] Step 7-2: Based on the array A obtained in step 6-2, re-divide the nodes of the container so that the elevation of the connection between two adjacent control bodies corresponds one-to-one with the unit data of array A. Based on the correspondence between the horizontal connecting pipes of the container side walls and array B, and the correspondence between array B and array A, mark the correspondence between the horizontal connecting pipes of the container side walls and the connection between two adjacent control bodies.

[0153] (3) Modeling of the transverse nozzle on the side wall of the container

[0154] Based on Figure 2 In the topological structure of the fluid region of the container shown, each transverse pipe on the side wall of the container corresponds to the connection between two adjacent control bodies, and the transverse pipe on the side wall of the container forms a multi-pass with the container cylinder. The multi-pass principle can be used to model the transverse pipe on the side wall of the container, such as Figure 4 As shown, the following steps are included:

[0155] Steps 1-3: Model all vessel sidewall lateral nozzles using a control volume based on the two-fluid six-equation model. The flow area of the control volume model is equal to the flow area of the lateral nozzle, the hydraulic equivalent diameter of the control volume model is equal to the inner diameter of the lateral nozzle, and the length of the control volume model is equal to the length of the lateral nozzle. One end of the control volume model is connected to the external thermal-hydraulic system via a fluid interface, and the other end is connected to the vessel control volume.

[0156] Step 2-3: Based on the corresponding annotations between the vessel sidewall transverse nozzle and the connection points between two adjacent control bodies, identify the vessel control body connected to the vessel sidewall transverse nozzle. Connect the control body model of the vessel sidewall transverse nozzle to the vessel control body model using a nozzle model. Then, connect the inlet or outlet of the vessel control body model to several nozzle models.

[0157] Step 3-3: Establish constraints for the nozzle models connected to the same vessel control volume model. By summing the fluid mass and energy transport terms for each nozzle model, the total mass and energy of the control volume model can be maintained to meet conservation requirements. For the nozzle model, calculate the vapor-liquid flow rate and fluid momentum based on the upstream and downstream control volume pressure differentials and thermal-hydraulic state parameters.

[0158] (4) Modeling of electric heating elements

[0159] The electric heating element is to add an internal heat source term Q to the vapor-liquid energy equation k Modeling is performed, see formula (2), to simulate the heating process of the container fluid by the electric heating element. Figure 2The discrete topological structure of the control volume is calculated by the following method:

[0160] Step 1-4: Determine the power weight of the container control body model based on the length of the electric heating element. When the elevations of the upper and lower boundaries of the control body from the bottom of the container are both less than the length of the electric heating element, the control body power weight factor N is:

[0161]

[0162] In formula (5) (corresponding to formula 1), H1 is the lower boundary elevation of the control volume, H2 is the upper boundary elevation of the control volume, and L c is the length of the control body, L t is the length of the heating element.

[0163] When the elevations of the upper and lower boundaries of the control body from the bottom of the container are both less than the length of the electric heating element, the power weight factor N of the control body is 0.

[0164] When the elevation of the upper boundary of the control body from the bottom of the container is greater than the length of the electric heating element, and the elevation of the lower boundary from the bottom of the container is less than the length of the electric heating element, the power weight factor N of the control body is:

[0165]

[0166] Step 2-4: For the vertical container, calculate the internal heat source term added to the vapor-liquid energy equation after the control volume is discretized:

[0167]

[0168]

[0169] Among them, Q g Add an internal heat source term to the vapor phase energy equation after the control volume is discretized, Q f The internal heat source term is added to the liquid phase energy equation after the control volume is discretized. Q is the power of the electric heating element, and Q max is the rated power of the heating element, is the power factor of the electric heating element, α g is the vapor phase cavitation fraction, ɑ f is the liquid phase fraction.

[0170] For horizontal containers, the internal heat source term added to the vapor-liquid energy equation after the control volume is discretized is:

[0171] Q g =0 (9)

[0172]

[0173] Among them, the power factor of the electric heating element It can be configured by the user or input from an external controller through the control interface.

[0174] It should be noted that formula (6) corresponds to formula 2, formula (7) corresponds to formula 3, formula (8) corresponds to formula 4, formula (9) corresponds to formula 5, and formula (10) corresponds to formula 6.

[0175] 2. Container thermal component area modeling

[0176] First, the container's thermal component region is divided into axial segments and radial nodes. The axial node division is consistent with the control volume division of the fluid region, including the number and length distribution of the thermal component's axial segments, ensuring a one-to-one correspondence between the thermal component's axial segments and the control volume. Simultaneously, the container's thermal component region is divided into radial nodes based on the radial dimensions of the solid wall and insulation layer. This ensures that the solid wall and insulation layer belong to different radial nodes, while also ensuring that each layer has several nodes for temperature analysis.

[0177] Assuming that the axial temperature gradient of the thermal component is much smaller than the radial temperature gradient, the heat transfer of the thermal component can only be along the radial direction. For the same axial segment of the thermal component, the following equation is satisfied:

[0178]

[0179] Where ρ is the solid density, C is the solid specific heat capacity, T is the thermal component temperature, λ is the thermal conductivity, and r is the radius of the cylindrical thermal component. Physical properties such as density, solid specific heat capacity, and thermal conductivity can be set separately for the solid wall layer and the insulation layer.

[0180] The outer wall of the insulation layer and the external environment adopt the third type of thermal boundary conditions, that is, the heat flux density q between the thermal component of the container and the external environment is out :

[0181]

[0182] In formula (12) (corresponding to formula 7), r out is the diameter of the outer wall of the container insulation layer, λ is the thermal conductivity of the insulation layer, h out is the heat transfer coefficient between the outer wall of the insulation layer and the external environment, T wout is the outer wall temperature of the insulation layer, T env is the external ambient temperature.

[0183] 3. Initialization method of thermal hydraulic parameters of container model

[0184] Step 1-5: Define the initial pressure P0, initial temperature T0, initial liquid level H0 and initial non-condensable gas fraction X of the container modeln0 ;

[0185] Specifically, the initialization state of the thermal hydraulic parameters of the container model consists of the initial pressure P0, initial temperature T0, initial liquid level H0 and initial fraction of non-condensable gas X n0 Define and determine the initial values of variables such as pressure of the container control body and the connecting pipe, vapor-liquid flow rate, vapor-liquid temperature, and cavitation fraction based on these four initial parameters.

[0186] Step 2-5: According to the initial pressure P0 and initial liquid level H0 of the container, the initial temperature T0 and the initial fraction of non-condensable gas X defined in step 1-5 are calculated. n0 Perform automatic calibration, such as Figure 5 Specifically, the following situations are included:

[0187] Case A: When the initial liquid level H0 of the container is equal to the full liquid level of the container (that is, the initial liquid level is equal to the height inside the container), first check the initial temperature T0. If the defined initial temperature T0 is less than or equal to the saturation temperature T corresponding to the initial pressure P0 of the container, s0 , the initial temperature T0 is not adjusted; if the defined initial temperature T0 is greater than the saturation temperature T corresponding to the container pressure s0 , it will automatically adjust to the saturation temperature T s0 .

[0188] Then check the initial fraction of non-condensable gas X n0 for:

[0189]

[0190] In formula (13) (corresponding to formula 8), P s (T0) is the saturation pressure corresponding to the initial temperature T0.

[0191] Case B: When the initial liquid level H0 of the container is equal to 0, first check the initial fraction of non-condensable gas X n0 , X n0 Should meet the following requirements:

[0192]

[0193] In formula (14) (corresponding to formula 9), P s (T env ) is the ambient temperature T env (Generally, the value is 20℃) The corresponding saturation pressure. When the initial fraction of non-condensable gas defined is X n0 When formula (14) is satisfied, X n0 No adjustment is made; when X n0 When formula (14) is not satisfied, X n0 Automatically adjust to:

[0194]

[0195] Then check the defined initial temperature T0, which should satisfy:

[0196] T0≥T s (P gs0 )=T s (P0(1-X n0 )) (16)

[0197] In formulas (15) and (16) (corresponding to formulas 10 and 11, respectively), P gs0 is the partial pressure of the container vapor, T s (P gs0 ) is the saturation temperature corresponding to the steam partial pressure. When the defined initial temperature T0 satisfies formula (16), that is, T0 is greater than or equal to the initial steam partial pressure P of the container g0 When the corresponding saturation temperature is reached, the defined initial temperature T0 is not adjusted. When the defined initial temperature T0 does not satisfy formula (16), T0 is automatically adjusted to:

[0198] T0=T s (P gs0 )=T s (P0(1-X n0 )) (17).

[0199] It should be noted that formula (17) corresponds to formula twelve.

[0200] Case C: When the initial liquid level H0 of the container is between 0 and the full level, first check the defined initial temperature T0. If the defined initial temperature T0 is less than or equal to the saturation temperature T corresponding to the initial pressure P0 of the container, s0 , the initial temperature T0 will not be adjusted temporarily; if the defined initial temperature T0 is greater than the saturation temperature T corresponding to the container pressure s0 , it will automatically adjust to the saturation temperature T s0 .

[0201] Then check the initial fraction of non-condensable gas X n0 , X n0 Should meet the following requirements:

[0202]

[0203] In formula (18) (corresponding to formula 13), P s (T0) is the saturation pressure corresponding to the initial temperature T0. When the initial fraction of non-condensable gas X n0 When formula (18) is satisfied, X n0 No adjustment is made; when X n0 When formula (18) is not satisfied, X n0Automatically adjust to:

[0204]

[0205] Finally, the defined initial temperature T0 is checked and automatically adjusted to:

[0206] T0=T s (P gs0 )=T s (P0(1-X n0 )) (20)

[0207] Then, according to the calibrated initial pressure P0, initial temperature T0, initial liquid level H0 and initial fraction of non-condensable gas X n0 Assign values to the initial parameters of the control body model and takeover model of the container. The assignment rules are as follows:

[0208] a. The initial values of the liquid and vapor flow rates of the container takeover model are both 0.

[0209] b. Initial pressure P of the control body model t0 are equal to the initial pressure P0 of the container.

[0210] c. Initial temperature of vapor phase of control body model T cg0 Both are:

[0211] T cg0 =max(T s (P0(1-X n0 )), T0) (21)

[0212] Among them, max() refers to the maximum value, T s (P0(1-X n0 )) is the saturation temperature corresponding to the steam partial pressure.

[0213] d. Initial temperature T of the liquid phase of the control body model cf0 Both are:

[0214] T cf0 =min(T s (P0(1-X n0 )), T0) (22)

[0215] Among them, min() refers to the minimum value.

[0216] e. When the container is a vertical container, the initial cavitation fraction α of the control body model cg0 for:

[0217]

[0218] Among them, H1 is the lower boundary elevation of the control body, and H2 is the upper boundary elevation of the control body.

[0219] When the container is a horizontal container, the initial cavitation fraction α of the control body model cg0 Both are:

[0220]

[0221] Where d is the inner diameter of the horizontal container.

[0222] It should be noted that formula (19) corresponds to formula 14, formula (20) corresponds to formula 15, formula (21) corresponds to formula 16, formula (22) corresponds to formula 17, formula (23) corresponds to formula 18, and formula (24) corresponds to formula 19.

[0223] The container model electric heating element is connected to the external controller model through a control interface. The parameter transmitted is the electric heating element power factor, and the data transmitted is in the form of an analog value from 0 to 1. The electric heating element power factor transmitted through the control interface is then transmitted to the container thermal component area modeling module. The container thermal component area modeling module calculates the electric heating element power calculation result and transmits it to the newly added internal heat source term of the control body vapor-liquid energy equation for related energy equation calculation.

[0224] The bottom pipe, top pipe and side wall transverse pipe of the container model are connected to other thermal-hydraulic component models based on two-fluid six equations through fluid interfaces. The transmitted parameters include pressure, cavitation fraction, vapor-liquid flow rate, vapor-liquid internal energy ratio, non-condensable gas fraction, etc., to realize the combination of the main equations of the container model and the main equations of other thermal-hydraulic component models.

[0225] The above content is the details of the container modeling process and method based on the two-fluid six-equation system. Within the framework of the two-fluid six-equation system, this application realizes the modularization, reusability, and scalability of the container model through the above-mentioned container modeling process and method. It is applicable to the case where the vapor space is non-condensable gas and the liquid space is supercooled water, and it is also applicable to the case where the vapor space is saturated steam and the liquid space is saturated water. It can also simulate the changes in the container's thermal-hydraulic parameters such as pressure, temperature, and liquid level after the fluid enters and exits the container through the pipe, providing reliable support for the modeling and simulation of the steam-water two-phase thermal-hydraulic system.

[0226] 2. Container Modeling System Based on Two-Fluid Six-Equation

[0227] like Figure 8 As shown, the present application provides a container modeling system based on two fluids and six equations. The container modeling system can be applied to the Modelica language. The container modeling system includes:

[0228] The container node division module is used to divide the container fluid area into several control bodies and connecting pipes in the form of a staggered grid, and the transverse connecting pipes of the container side walls at different elevations correspond to different adjacent control body connections; it is used to axially divide the container thermal component area into several blocks, and the division form is consistent with the control body division of the fluid area, so that each thermal component block corresponds to a control body; at the same time, the radial nodes of the container thermal component area are divided according to the container solid wall layer and the possible insulation layer, so that the container solid wall layer and the insulation layer belong to different radial nodes.

[0229] The container fluid region modeling and initialization module is used to construct the main fluid region equation model, constitutive closed-form equation model, and physical property equation model based on the two-fluid six equations. It is then discretized and solved according to the container's node partitioning. It also defines and verifies the initialization parameters of the container fluid region and initializes the variables of each control volume and nozzle based on these verified initialization parameters.

[0230] The container thermal component area modeling module is used to construct the heat conduction equation model and thermal boundary model of the container thermal component area.

[0231] The container electric heating element modeling module is used to add the electric heating element heat source term to the container control volume vapor-liquid energy equation, and accepts the parameters of the control interface as the electric heating element power factor to calculate the electric heating element power, which is applied to the newly added internal heat source term in the control volume vapor-liquid energy equation.

[0232] The container model encapsulation module is used to construct the fluid interfaces of the bottom pipe, top pipe and side wall lateral pipe of the container model and the control interface of the electric heating element. It integrates the fluid area model, thermal component model and electric heating element model of the encapsulated container model to form a container component model with several fluid interfaces and control interfaces.

[0233] The container model application module is used to connect the constructed container model with other thermal hydraulic component models such as pipeline models based on two fluids and six equations, valve models, pipeline accessory models, and hungry controller models for electric heating element power control, to build a simulation system, simulate the changes in the container's thermal hydraulic parameters such as pressure, temperature, and liquid level after the fluid enters and exits the container through the pipe, and simulate the heat dissipation process of the container side wall and the heating process of the container electric heating element on the supercooled water or saturated water in the liquid space.

[0234] At least one embodiment of the present application further provides a computer device comprising at least a processor and a readable storage medium. The readable storage medium stores a computer program that, when executed by the processor, implements the aforementioned control valve modeling method based on two fluids and six equations.

[0235] It should be noted that the processor is, for example, a CPU. The computer device may also include a display screen.

[0236] At least one embodiment of the present application provides a computer-readable storage medium having computer executable instructions stored thereon. When the executable instructions are executed by a processor, the above-mentioned container modeling method based on two fluids and six equations is implemented.

[0237] At least one embodiment of the present application provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the above-mentioned container modeling method based on two fluids and six equations.

[0238] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and not to limit them. Although the present application has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present application can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present application should be included in the scope of protection of the claims of the present application.

Claims

1. A container modeling method based on two-fluid six-equation method, characterized in that: The following steps are involved: Step 1: Simplify the container into a pipe model with a thermal component described by two fluids and six equations. The inlet fluid interface of the pipe model serves as the bottom pipe of the container, the outlet fluid interface of the pipe model serves as the top pipe of the container, and the thermal component serves as the solid wall of the container. Step 2: Based on the axial distribution of the transverse nozzles on the side wall of the container, divide the container fluid area into nodes in the axial direction so that the transverse nozzles on the side wall of the container at different elevations correspond to different connections between two adjacent control bodies; Step 3: Divide the container thermal component area into axial blocks and radial nodes, so that the thermal component axial blocks correspond to the control volume one by one, and the solid wall layer and insulation layer of the container thermal component area belong to different radial nodes; Step 4: Model the container side wall transverse pipes at the connection points of adjacent control bodies corresponding to the transverse pipes using the multi-pass model principle. The container side wall transverse pipes are connected to the external thermal hydraulic system through fluid interfaces. Step 5: Model the container heating element by adding a heat source term to the discretized vapor-liquid energy equation on the control volume. Determine the power of the newly added internal heat source term in the discretized vapor phase energy equation and liquid phase momentum equation for each control volume based on the height of the heating element from the bottom of the container and the cavitation fraction of the control volume. Step 6: Use the third-class boundary to model the heat dissipation of the container's thermal components, set the ambient temperature of the container and the heat transfer coefficient between the container's outer wall and the environment; Step 7: Extract the control interface for the power control of the container's electric heating element and the fluid interfaces of the bottom, top, and sidewall pipes of the container model. Integrate and encapsulate the fluid region model, thermal component model, and electric heating element model of the container model into a container component model with several fluid interfaces and control interfaces. Step 8: Connect the constructed container component model with other thermal-hydraulic component models based on two-fluid six-equation to build a simulation system to simulate the changes in the thermal-hydraulic parameters of the container after the fluid enters and exits the container through the pipe under different initial conditions.

2. The container modeling method according to claim 1, characterized in that: The simplified pipeline model uses Modelica as the modeling language, and includes a main equation model, a constitutive equation model and a physical property equation model; the main equation model includes the mass equation, momentum equation, energy equation and non-condensable gas equation of the vapor phase and liquid phase; the constitutive equation model includes the wall friction equation, wall heat transfer equation, phase interface friction equation, phase interface heat transfer equation and phase interface mass exchange equation; the physical property equation model uses the standard formula IAPWS-97 for physical property parameters of water and water vapor to obtain physical property parameters for calling by the main equation model and the constitutive equation model.

3. The container modeling method according to claim 1, characterized in that: The implementation of the container fluid region node division method includes the following steps: Step 1-1: Set the total number of nodes for container node division according to modeling requirements. The total number of nodes must be greater than the number of transverse pipes on the container side walls. If the container has no transverse pipes, directly divide the container evenly according to the total number of nodes required. Step 2-1: Create an elevation array that includes all the container sidewall transverse nozzles. The cell data of the array is arranged from small to large. The cell data of the elevation array are not equal to each other and duplicates should be removed. That is, if there are several container sidewall transverse nozzles with the same elevation, then these container sidewall transverse nozzles are mapped to only one cell data in the elevation array. Step 3-1: Divide the container into nodes according to the elevation array obtained in step 2-1, and divide the container into a number of blocks, so that the elevation of the connection between two adjacent blocks from the bottom of the container corresponds one-to-one with the unit data of the elevation array; Step 4-1: Further perform node division on the nodes divided in step 3-1, dividing each node into several control bodies. The lengths of the control bodies in the same node are equal, so that the total number of control bodies is equal to the total number of nodes required to divide the container, and the length of each control body is as close as possible to the ratio of the container height to the total number of nodes required to divide, that is, the average length of the control body; Step 5-1: According to the correspondence between the transverse connecting pipe of the container side wall and the elevation array unit data, mark the correspondence between the transverse connecting pipe of the container side wall and the connection between two adjacent control bodies.

4. The container modeling method according to claim 1, characterized in that: The implementation of the container fluid region node division method includes the following steps: Step 1-2: Set the total number of nodes for container node division according to modeling requirements. The total number of nodes must be greater than the number of lateral pipes on the container side wall. Step 2-2: Divide the container evenly according to the total number of nodes, take the bottom of the container as the elevation zero point, and obtain an elevation array including the connection points of all two adjacent control bodies in the container, named array A; Step 3-2: Create an array of the elevations of all the container sidewall transverse nozzles, named array B. The cell data of array B are arranged from small to large. The cell data of array B are not equal to each other and duplicates should be removed. That is, if there are several container sidewall transverse nozzles with the same elevation, then these container sidewall transverse nozzles are mapped to only one cell data in array B. Step 4-2: Using the first cell data B.1 of array B as a reference, locate cell data A.1 in array A. Among all the cell data in array A, the absolute value of the difference between A.1 and B.1 is the smallest. Update array A, modify A.1 to make it equal to B.1, and mark cell data A.1 so that it corresponds to cell data B.1 in array B. Step 5-2: Using cell data B.2 in array B as a reference, locate cell data A.2 in array A. Among all the cell data in array A, excluding the marked cell data, the absolute value of the difference between A.2 and B.2 is the smallest. Update array A, modify A.2 to make it equal to B.2, and mark cell data A.2 to correspond to cell data B.2 in array B. Step 6-2: Repeat step 5-2 until all the cell data in array B are matched and labeled with the cell data in array A; Step 7-2: Based on the array A obtained in step 6-2, re-divide the nodes of the container so that the elevation of the connection between two adjacent control bodies corresponds one-to-one with the unit data of array A. Based on the correspondence between the horizontal connecting pipes of the container side walls and array B, and the correspondence between array B and array A, mark the correspondence between the horizontal connecting pipes of the container side walls and the connection between two adjacent control bodies.

5. The container modeling method according to claim 1, characterized in that: The multi-pass model principle includes the following steps: Step 1-3: Model all the transverse nozzles on the side walls of the container using a control volume based on the two-fluid six-equation model. The flow area of the control volume model is equal to the flow area of the transverse nozzle, the hydraulic equivalent diameter of the control volume model is equal to the inner diameter of the transverse nozzle, and the length of the control volume model is equal to the length of the transverse nozzle. One end of the control volume model is connected to the external thermal-hydraulic system through a fluid interface, and the other end is connected to the container control volume. Step 2-3: Based on the corresponding annotation relationship between the connection points of the container side wall transverse nozzle and the two adjacent control bodies, identify the container control body connected to the container side wall transverse nozzle, and connect the control body model of the container side wall transverse nozzle with the container control body model in the form of a nozzle model. Then, the inlet or outlet of the container control body model is connected to several nozzle models; Step 3-3: Establish a constraint relationship for the take-over model connected to the same container control body model. By summing the fluid mass transport term and energy transport term of each take-over model, the total mass and total energy of the control body model can meet the conservation requirements. For the take-over model, the flow rate and fluid momentum of the vapor-liquid two-phase of the take-over model are calculated based on the control body pressure difference and thermal-hydraulic state parameters upstream and downstream of the take-over.

6. The container modeling method according to claim 1, characterized in that: The container electric heating element is to add the internal heat source term Q to the vapor-liquid energy equation. g and Q f Modeling is carried out, and the internal heat source term Q is added to the discrete vapor-liquid energy equation g and Q f The calculation method is: Step 1-4: Determine the power weight of the container control body model based on the length of the electric heating element. When the elevations of the upper and lower boundaries of the control body from the bottom of the container are both less than the length of the electric heating element, the control body power weight factor N is: In formula 1, H1 is the lower boundary elevation of the control volume, H2 is the upper boundary elevation of the control volume, and L c is the length of the control body, L t is the length of the heating element; When the elevations of the upper and lower boundaries of the control body from the bottom of the container are both less than the length of the electric heating element, the power weight factor N of the control body is 0; When the elevation of the upper boundary of the control body from the bottom of the container is greater than the length of the electric heating element, and the elevation of the lower boundary from the bottom of the container is less than the length of the electric heating element, the power weight factor N of the control body is: Step 2-4: For the vertical container, calculate the internal heat source term added to the vapor-liquid energy equation after the control volume is discretized: Among them, Q g Add an internal heat source term to the vapor phase energy equation after the control volume is discretized, Q f The internal heat source term is added to the liquid phase energy equation after the control volume is discretized. Q is the power of the electric heating element, and Q max is the rated power of the heating element, is the power factor of the electric heating element, α g is the vapor phase cavitation fraction, α f is the liquid phase fraction; For horizontal containers, the internal heat source term added to the vapor-liquid energy equation after the control volume is discretized is: Q g =0 Formula 5 7. The container modeling method according to claim 1, characterized in that: The container model electric heating element is connected to the external controller model through a control interface. The parameter transmitted is the electric heating element power factor, and the data transmitted is in the form of an analog value from 0 to 1. The electric heating element power factor transmitted through the control interface is then transmitted to the container thermal component area modeling module. The container thermal component area modeling module calculates the electric heating element power calculation result and transmits it to the newly added internal heat source term of the control body vapor-liquid energy equation for related energy equation calculation.

8. The container modeling method according to any one of claims 1 to 7, characterized in that: The outer wall of the insulation layer and the external environment adopt the third type of thermal boundary conditions, that is, the heat flux density q between the thermal component of the container and the external environment is out : Among them, r out is the diameter of the outer wall of the container insulation layer, λ is the thermal conductivity of the insulation layer, h out is the heat transfer coefficient between the outer wall of the insulation layer and the external environment, T wout is the outer wall temperature of the insulation layer, T env is the external ambient temperature.

9. A method for initializing thermal hydraulic parameters of a container model based on two-fluid six-equation method, characterized in that: The steps include: Step 1-5: Define the initial pressure P0, initial temperature T0, initial liquid level H0 and initial non-condensable gas fraction X of the container model n0 ; Step 2-5: According to the initial pressure P0 and initial liquid level H0 of the container, the initial temperature T0 and the initial fraction of non-condensable gas X defined in step 1 are calculated. n0 Automatic verification is performed, including the following situations: Case A: When the initial liquid level H0 of the container is equal to the full liquid level of the container (that is, the initial liquid level is equal to the height inside the container), first check the initial temperature T0. If the defined initial temperature T0 is less than or equal to the saturation temperature T corresponding to the initial pressure P0 of the container, s0 , the initial temperature T0 is not adjusted; if the defined initial temperature T0 is greater than the saturation temperature T corresponding to the container pressure s0 , it will automatically adjust to the saturation temperature T s0 ; Then check the initial fraction of non-condensable gas X n0 for: Among them, P s (T0) is the saturation pressure corresponding to the initial temperature T0; Case B: When the initial liquid level H0 of the container is equal to 0, first check the initial fraction of non-condensable gas X n0 , X n0 Should meet the following requirements: Among them, P s (T env ) is the ambient temperature T env (generally taken as 20℃) corresponding to the saturation pressure, when the initial fraction of non-condensable gas defined is X n0 When formula 9 is satisfied, X n0 No adjustment is made; when X n0 When formula 9 is not satisfied, X n0 Automatically adjust to: Then check the defined initial temperature T0, which should satisfy: T0≥T s (P gs0 )=T s (P0(1-X n0 )) Formula 11 Among them, P gs0 is the partial pressure of the container vapor, T s (P gs0 ) is the saturation temperature corresponding to the steam partial pressure. When the defined initial temperature T0 satisfies formula (11), that is, T0 is greater than or equal to the initial steam partial pressure P of the container, g0 When the corresponding saturation temperature is reached, the defined initial temperature T0 is not adjusted. When the defined initial temperature T0 does not satisfy formula (11), T0 is automatically adjusted to: T0=T s (P gs0 )=T s (P0(1-X n0 )) Formula 12 Case C: When the initial liquid level H0 of the container is between 0 and the full level, first check the defined initial temperature T0. If the defined initial temperature T0 is less than or equal to the saturation temperature T corresponding to the initial pressure P0 of the container, s0 , the initial temperature T0 will not be adjusted temporarily; if the defined initial temperature T0 is greater than the saturation temperature T corresponding to the container pressure s0 , it will automatically adjust to the saturation temperature T s0 ; Then check the initial fraction of non-condensable gas X n0 , X n0 Should meet the following requirements: Among them, P s (T0) is the saturation pressure corresponding to the initial temperature T0. When the initial fraction of non-condensable gas X is defined n0 When formula (13) is satisfied, X n0 No adjustment is made; when X n0 When formula (13) is not satisfied, X n0 Automatically adjust to: Finally, the defined initial temperature T0 is checked and automatically adjusted to: T0=T s (P gs0 )=T s (P0(1-X n0 )) Formula 15 Step 3-5: Based on the calibrated initial pressure P0, initial temperature T0, initial liquid level H0 and initial fraction of non-condensable gas X n0 Assign values to the initial parameters of the control body model and takeover model of the container. The assignment rules are as follows: a. The initial values of the liquid and vapor flow rates of the container nozzle model are both 0; b. Initial pressure P of the control body model t0 are equal to the initial pressure P0 of the container; c. Initial temperature of vapor phase of control body model T cg0 Both are: T cg0 =max(T s (P0(1-X n0 )), T0) Formula 16 Among them, max() refers to the maximum value, T s (P0(1-X n0 )) is the saturation temperature corresponding to the steam partial pressure; d. Initial temperature T of the liquid phase of the control body model cf0 Both are: T cf0 =min(T s (P0(1-X n0 )), T0) Formula 17 Among them, min() refers to the minimum value; e. When the container is a vertical container, the initial cavitation fraction α of the control body model cg0 for: Among them, H1 is the lower boundary elevation of the control body, and H2 is the upper boundary elevation of the control body; When the container is a horizontal container, the initial cavitation fraction α of the control body model cg0 Both are: Where d is the inner diameter of the horizontal container.

10. A container modeling system based on two fluids and six equations, characterized in that: include: The container node division module is used to divide the container fluid area into several control bodies and nozzles in a staggered grid format, and to make the transverse nozzles of the container side wall at different elevations correspond to different adjacent control body connections. It is used to axially divide the container thermal component area into several blocks. The division format is consistent with the control body division of the fluid area, so that each thermal component block corresponds to a control body. At the same time, the radial nodes of the container thermal component area are divided according to the container solid wall layer and any existing insulation layer, so that the container solid wall layer and the insulation layer belong to different radial nodes. The container fluid region modeling and initialization module is used to construct the main equation model of the fluid region, the constitutive closed equation model, and the physical property equation model based on the two-fluid six equations in the container fluid region, and discretize and solve them according to the node division form of the container. It is also used to define and verify the initialization parameters of the container fluid region, and initialize and assign values to the variables of each control body and nozzle according to the verified initialization parameters; The container thermal component area modeling module is used to construct the heat conduction equation model and thermal boundary model of the container thermal component area; The container electric heating element modeling module is used to add the electric heating element heat source term to the container control volume vapor-liquid energy equation. It accepts the parameters of the control interface as the electric heating element power factor to calculate the electric heating element power and applies it to the newly added internal heat source term in the control volume vapor-liquid energy equation. The container model packaging module is used to construct the fluid interfaces of the bottom nozzle, top nozzle, and side wall lateral nozzle of the container model, as well as the control interface of the electric heating element. It integrates the fluid region model, thermal component model, and electric heating element model of the packaged container model to form a container component model with multiple fluid interfaces and control interfaces. The container model application module is used to connect the constructed container model with other thermal-hydraulic component models based on two-fluid six-equation and the hungry controller model for electric heating element power control, to build a simulation system, simulate the changes in the thermal-hydraulic parameters of the container after the fluid enters and exits the container through the pipe, and simulate the heat dissipation process of the container side wall and the heating process of the container electric heating element on the supercooled water or saturated water in the liquid space.

11. A computer device, characterized in that: The computer device includes at least a processor and a readable storage medium, wherein the readable storage medium stores a computer program, and when the computer program is executed by the processor, the container modeling method based on two fluids and six equations as described in any one of claims 1 to 9 is implemented.

12. A computer-readable storage medium having computer-executable instructions stored thereon, characterized in that: When the executable instructions are executed by the processor, the container modeling method based on two fluids and six equations as described in any one of claims 1 to 9 is implemented.

13. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the container modeling method based on two fluids and six equations as described in any one of claims 1 to 9 is implemented.

Images