Nuclear power station condensate retention volume calculation method and device, storage medium and electronic equipment

Abstract

The invention relates to a nuclear power station condensate retention volume calculation method and device, a storage medium and electronic equipment, and the method comprises the steps: building a condensate retention volume analysis geometric model of a to-be-analyzed object, and carrying out the mesh generation of the geometric model, and obtaining a three-dimensional mesh model; calculating the three-dimensional grid model by adopting a single-phase multi-component model to obtain a flow field and component distribution of gas and liquid phases in the phase change process; based on the flow field and component distribution of the gas phase and the liquid phase in the phase change process, calculation is carried out in combination with a control equation of the to-be-analyzed object on the condensation wall surface, and the condensate generation rate on the condensation wall surface is obtained; calculating the distribution condition of the liquid film on the condensation wall surface based on the condensate generation rate; according to the distribution condition of the condensation wall surface, the wall surface condensation rule under different steam conditions is analyzed by adjusting calculation conditions, and condensate retention volume data of the condensation wall surface is obtained. Condensate accumulation conditions under different structures and working conditions can be quantitatively predicted and evaluated, and damage to equipment and accident risks are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of condensation heat transfer simulation of nuclear power plants, and more specifically, to a method, device, storage medium and electronic equipment for calculating condensate retention in nuclear power plants. Background Art

[0002] The containment spray system is an important safeguard system of a nuclear power plant. When an accident occurs in the containment, the system can spray cooling medium into the containment for evaporative cooling, thereby controlling the internal pressure and temperature of the containment within the permitted range.

[0003] The spray system needs to draw water from the pit during the recirculation spraying stage. To ensure the safe operation of the containment spray pump, it is necessary to ensure that there is sufficient effective cavitation margin at the pump inlet. Therefore, it is necessary to ensure that the liquid level after the suppression tank is filled with water meets the minimum water storage requirement of the containment spray pump. The quantitative analysis of the water loss in the suppression tank under accident conditions is the key. The water loss mainly includes the leakage of the containment, the reflux tolerance loss of the suppression tank, and the retained water in the containment. Since the retained water is affected by many factors such as the thickness of the water film and pressure, it is difficult to calculate the condensation water on the wall / floor. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method, device, storage medium and electronic equipment for calculating the condensate retention amount of a nuclear power plant in view of the problems existing in the prior art.

[0005] The technical solution adopted by the present invention to solve the technical problem is: construct a method for calculating the condensate retention amount of a nuclear power plant, comprising the following steps:

[0006] Establishing a condensate retention analysis geometric model for the object to be analyzed, and meshing the geometric model to obtain a three-dimensional mesh model;

[0007] The three-dimensional grid model is calculated using a single-phase multi-component model to obtain the flow field and component distribution of the gas-liquid two-phase during the phase change process;

[0008] Based on the flow field and component distribution of the gas-liquid two-phase in the phase change process, combined with the control equation of the object to be analyzed on the condensation wall surface, calculation is performed to obtain the condensate generation rate on the condensation wall surface;

[0009] Calculating the distribution of the liquid film on the condensation wall surface based on the condensate generation rate;

[0010] According to the distribution of the condensation wall surface, by adjusting the calculation conditions and analyzing the wall condensation law under different steam conditions, the condensate retention data of the condensation wall surface is obtained.

[0011] In the method for calculating the condensate retention amount of a nuclear power plant according to the present invention, the step of establishing a condensate retention amount analysis geometric model of the object to be analyzed and meshing the geometric model to obtain a three-dimensional mesh model comprises:

[0012] Establishing a three-dimensional geometric model of the object to be analyzed according to the structural shape and size of the object to be analyzed;

[0013] Simplifying the three-dimensional geometric model according to the structural function and working conditions of the object to be analyzed to obtain a simplified three-dimensional model;

[0014] Meshing the simplified three-dimensional model to obtain an initial mesh model;

[0015] The initial mesh model is processed to obtain the three-dimensional mesh model.

[0016] In the method for calculating the condensate retention amount of a nuclear power plant according to the present invention, the processing of the initial grid model to obtain the three-dimensional grid model includes:

[0017] Extracting a fluid calculation domain required for calculation from the initial grid model;

[0018] Smoothing and optimizing the fluid computational domain grid;

[0019] The inlet condition, outlet condition and wall boundary condition of the fluid calculation domain grid are determined, the grid division is completed, and the three-dimensional grid model is obtained.

[0020] In the method for calculating the condensate retention of a nuclear power plant described in the present invention, the three-dimensional grid model is calculated using a single-phase multi-component model to obtain the flow field and component distribution of the gas-liquid two-phase in the phase change process, including:

[0021] During condensation, determine the single-phase multi-component fluid;

[0022] Determine whether the fluid has reached equilibrium;

[0023] If so, the condensation transition of the vapor component in the gas phase to the liquid phase is completed through the coupling of the wall source term;

[0024] Calculate the mixed gas parameters of the three-dimensional grid model based on the single-phase multi-component model;

[0025] Iterative calculation is performed to obtain the flow field and component distribution of the gas-liquid two-phase during the phase change process.

[0026] In the method for calculating the condensate retention amount of a nuclear power plant described in the present invention, the flow field and component distribution of the gas-liquid two-phase in the phase change process are calculated in combination with the control equation of the object to be analyzed on the condensate wall surface to obtain the condensate generation rate on the condensate wall surface, which includes:

[0027] Based on the flow field and component distribution of the gas-liquid two-phase during the phase change process, calculate the latent heat released by the steam at any time;

[0028] Simulating the mass source term, energy source term and momentum source term of the mixed gas in the phase change process according to the control equation of the condensation wall;

[0029] Calculate the component loss of mixed gas during phase change;

[0030] Calculating according to the mass source term, the energy source term, the momentum source term, and in combination with the wall temperature, to obtain an updated phase change rate;

[0031] Calculating according to the updated phase change rate and the latent heat to obtain the condensate generation rate on the wall unit at each moment;

[0032] Iterative calculation is performed to obtain the condensate generation rate on the condensation wall surface at different times.

[0033] In the method for calculating the condensate retention in a nuclear power plant of the present invention, the mass source term, energy source term and momentum source term of the mixed gas in the phase change process simulated according to the control equation of the condensation wall include:

[0034] The following calculations are performed based on the governing equations of the condensation wall:

[0035] Calculate the mass transfer of the gas phase steam component to the liquid phase water component according to the initial phase change rate to obtain the mass source term;

[0036] Calculate the heat transferred from the gas phase to the liquid phase according to the initial phase change rate and the latent heat of vaporization of the steam to obtain the energy source term;

[0037] The momentum source term is obtained by calculating the momentum loss between the gas and the liquid according to the wall viscous stress and the pressure.

[0038] In the method for calculating the condensate retention of a nuclear power plant described in the present invention, the calculation of the component loss of the mixed gas during the phase change process includes:

[0039] During the phase change process, the change in the component fraction of the mixed gas is calculated based on the proportional loss of the gas phase steam components; the change in the component fraction of the mixed gas is the combined loss of the mixed gas.

[0040] In the method for calculating the condensate retention amount in a nuclear power plant according to the present invention, the calculation based on the mass source term, the energy source term, the momentum source term, and in combination with the wall temperature to obtain the updated phase change rate includes:

[0041] Calculating the equilibrium pressure of the steam during phase change according to the mass source term, the energy source term, the momentum source term and the temperature of the mixed gas;

[0042] The saturated steam pressure at the gas-liquid interface is obtained by calculating the equilibrium pressure of the steam during the phase change in combination with the wall temperature, and the updated phase change rate is obtained.

[0043] In the method for calculating the condensate retention amount in a nuclear power plant according to the present invention, the calculation of the distribution of the liquid film on the condensate wall surface based on the condensate generation rate includes:

[0044] Based on the condensate generation rate, a liquid film model is used to calculate the distribution of the liquid film on the condensate wall surface.

[0045] In the method for calculating the condensate retention amount in a nuclear power plant of the present invention, the calculation of the distribution of the liquid film on the condensate wall surface using a liquid film model based on the condensate generation rate includes:

[0046] Create a liquid film subgrid in the first computational cell on the wall;

[0047] Determining the condensate generation rate as an inlet velocity boundary condition of the liquid film subgrid;

[0048] In the liquid film subgrid, the flow and heat conduction of the liquid film are calculated to obtain the liquid film velocity, thickness and temperature distribution;

[0049] The liquid-gas phase change rate is obtained by calculating the interfacial energy balance between the liquid film and the gas phase;

[0050] Obtaining an average velocity of the liquid film, and determining the average velocity of the liquid film as an outlet velocity boundary condition of the liquid film subgrid;

[0051] Calculate single-phase flow in the external flow field;

[0052] Based on the liquid film velocity, thickness and temperature distribution, the single-phase flow performs iterative calculation of internal and external flow fields to obtain a coupling solution of the liquid film and gas phase flow; the coupling solution of the liquid film and gas phase flow is the distribution of the liquid film on the condensation wall.

[0053] In the method for calculating the condensate retention amount of a nuclear power plant of the present invention, the condensate retention amount data of the condensate wall surface is obtained by adjusting the calculation conditions and analyzing the wall condensation law under different steam conditions according to the distribution of the condensate wall surface, including:

[0054] Determine the parameters that affect condensation;

[0055] Different values ​​of the parameters affecting condensation are set respectively to obtain multiple groups of calculation conditions;

[0056] According to the distribution of the condensation wall surface, numerical simulation of the condensate retention amount is performed for each group of calculation conditions, and the variation law of the wall condensation amount under different conditions is analyzed to obtain the condensate retention amount data of the condensation wall surface.

[0057] The present invention also provides a device for calculating the condensate retention amount of a nuclear power plant, comprising:

[0058] A model building unit, used to establish a condensate retention analysis geometric model for the object to be analyzed, and to mesh the geometric model to obtain a three-dimensional mesh model;

[0059] A phase change calculation unit, used to calculate the three-dimensional grid model using a single-phase multi-component model to obtain the flow field and component distribution of the gas-liquid two-phase during the phase change process;

[0060] A condensate generation rate calculation unit, used to calculate based on the flow field and component distribution of the gas-liquid two-phase in the phase change process, combined with the control equation of the object to be analyzed on the condensation wall surface, to obtain the condensate generation rate on the condensation wall surface;

[0061] A liquid film distribution calculation unit, used to calculate the distribution of the liquid film on the condensation wall surface based on the condensate generation rate;

[0062] The condensate retention calculation unit is used to obtain the condensate retention data of the condensate wall by adjusting the calculation conditions according to the distribution of the condensate wall surface and analyzing the wall condensation law under different steam conditions.

[0063] The present invention also provides a storage medium storing a computer program, wherein the computer program is suitable for being loaded by a processor to execute the steps of the method for calculating the condensate retention amount of a nuclear power plant as described above.

[0064] The present invention also provides an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor executes the steps of the method for calculating the condensate retention amount of a nuclear power plant as described above by calling the computer program stored in the memory.

[0065] The method, device, storage medium and electronic device for calculating the condensate retention of a nuclear power plant according to the present invention have the following beneficial effects: including: establishing a geometric model for analyzing the condensate retention of the object to be analyzed, and meshing the geometric model to obtain a three-dimensional mesh model; using a single-phase multi-component model to calculate the three-dimensional mesh model to obtain the flow field and component distribution of the gas-liquid two-phase in the phase change process; based on the flow field and component distribution of the gas-liquid two-phase in the phase change process, combined with the control equation of the object to be analyzed on the condensation wall, calculate to obtain the condensate generation rate on the condensation wall; based on the condensate generation rate, calculate the distribution of the liquid film on the condensation wall; according to the distribution of the condensation wall, adjust the calculation conditions to analyze the wall condensation law under different steam conditions, and obtain the condensate retention data of the condensation wall. The present invention can quantitatively predict and evaluate the accumulation of condensate under different structures and working conditions, avoiding damage to equipment and accident risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0067] Figure 1 It is a schematic flow chart of a method for calculating the condensate retention amount of a nuclear power plant provided by the present invention;

[0068] Figure 2 It is a principle block diagram of the device for calculating the condensate retention amount of a nuclear power plant provided by the present invention;

[0069] Figure 3 is a geometric model of the containment vessel in an embodiment of the present invention;

[0070] Figure 4 is a simplified geometric model in an embodiment of the present invention;

[0071] Figure 5 is a simplified schematic diagram of the model mesh division in an embodiment of the present invention;

[0072] Figure 6 is a schematic diagram of wall condensation parameters in an embodiment of the present invention;

[0073] Figure 7 is a schematic diagram of a two-dimensional calculation domain and a grid in an embodiment of the present invention;

[0074] Figure 8 is the verification result of the wall condensation flux in the embodiment of the present invention;

[0075] Fig. 9 is a temperature distribution cloud diagram in an embodiment of the present invention;

[0076] Fig.10 is a water vapor mass fraction cloud diagram in an embodiment of the present invention;

[0077] Fig.11 is a dry air mass fraction cloud diagram in an embodiment of the present invention;

[0078] Fig.12 is a velocity distribution cloud diagram in an embodiment of the present invention;

[0079] Figure 13-Figure 16 It is the calculation result of the liquid film in the embodiment of the present invention. DETAILED DESCRIPTION

[0080] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0081] The present invention constructs a geometric model of retention and reasonably simplifies it according to the functions of each structure and the working environment, and at the same time establishes a numerical simulation model of condensate retention based on the geometric model. The method can analyze the wall condensation law in detail and provide guidance for the condensate retention analysis of the object to be analyzed. The object to be analyzed here can be a containment, or other geometric structures, for example, a nozzle, ancillary equipment, a nozzle mounting bracket, etc.

[0082] Specifically, Figure 1 As shown, in a preferred embodiment, the method for calculating the condensate retention amount of a nuclear power plant includes the following steps:

[0083] Step S101: establishing a condensate retention analysis geometric model for the object to be analyzed, and meshing the geometric model to obtain a three-dimensional mesh model.

[0084] Optionally, in some embodiments, establishing a condensate retention analysis geometric model for the object to be analyzed, and meshing the geometric model to obtain a three-dimensional mesh model includes: establishing a three-dimensional geometric model of the object to be analyzed according to the structural shape and size of the object to be analyzed; simplifying the three-dimensional geometric model according to the structural function and working conditions of the object to be analyzed to obtain a simplified three-dimensional model; meshing the simplified three-dimensional model to obtain an initial mesh model; processing the initial mesh model to obtain a three-dimensional mesh model. The construction of the three-dimensional geometric model can be established by CAD software.

[0085] Among them, processing the initial grid model to obtain a three-dimensional grid model includes: extracting the fluid calculation domain required for calculation from the initial grid model; smoothing and optimizing the fluid calculation domain grid; determining the inlet conditions, outlet conditions and wall boundary conditions of the fluid calculation domain grid, completing grid division, and obtaining a three-dimensional grid model.

[0086] Step S102: using a single-phase multi-component model to calculate the three-dimensional grid model, and obtaining the flow field and component distribution of the gas-liquid two-phase during the phase change process.

[0087] Optionally, in some embodiments, a single-phase multi-component model is used to calculate the three-dimensional grid model to obtain the flow field and component distribution of the gas-liquid two-phase during the phase change process, including: determining the single-phase multi-component fluid during the condensation process; judging whether the fluid has reached an equilibrium state; if so, completing the condensation transition of the steam component in the gas phase to the liquid phase through the coupling of the wall source term; calculating the mixed gas parameters of the three-dimensional grid model based on the single-phase multi-component model; and performing iterative calculations to obtain the flow field and component distribution of the gas-liquid two-phase during the phase change process.

[0088] Specifically, during the condensation process, the steam-air mixed gas is regarded as a single-phase multi-component fluid. Among them, when the components in the gas phase are completely mixed, the single-phase multi-component fluid is in equilibrium. When the single-phase multi-component fluid is in equilibrium, the condensation transition of the steam component in the gas phase to the liquid phase is realized through the coupling of the wall source term, and the mixed gas parameters (i.e., the density, specific heat capacity, viscosity, thermal conductivity, etc. of the mixed gas) are calculated. Finally, the flow field and component distribution of the gas-liquid two-phase in the phase change process are obtained through iterative calculation. Among them, the source term is a generalized quantity, which represents the sum of all other terms that cannot be included in the non-steady-state terms, convection terms and diffusion terms in the control equation. The addition of the source term is of great significance for expanding the generality of the algorithm discussed and the corresponding program. If the source term is a constant, it will not cause any difficulties in the process of establishing the discrete equation. In general, the source term is not a constant and is a function of the unknown quantity to be sought.

[0089] Step S103: Based on the flow field and component distribution of the gas-liquid two-phase in the phase change process, combined with the control equation of the object to be analyzed on the condensation wall surface, calculation is performed to obtain the condensate generation rate on the condensation wall surface.

[0090] Optionally, in some embodiments, based on the flow field and component distribution of the gas-liquid two-phase during the phase change process, combined with the control equation of the object to be analyzed on the condensation wall, calculation is performed to obtain the condensate generation rate on the condensation wall, including: calculating the latent heat released by steam at any time based on the flow field and component distribution of the gas-liquid two-phase during the phase change process; simulating the mass source term, energy source term and momentum source term of the mixed gas during the phase change process according to the control equation of the condensation wall; calculating the component loss of the mixed gas during the phase change process; calculating according to the mass source term, energy source term, momentum source term, and in combination with the wall temperature to obtain an updated phase change rate; calculating according to the updated phase change rate and latent heat to obtain the condensate generation rate on the wall unit at each time; performing iterative calculations to obtain the condensate generation rate on the condensation wall at different times.

[0091] In some embodiments, simulating the mass source term, energy source term, and momentum source term of the mixed gas in the phase change process according to the control equation of the condensation wall includes: performing the following calculations based on the control equation of the condensation wall: calculating the mass transfer from the gas phase steam component to the liquid phase water component according to the initial phase change rate to obtain the mass source term; calculating the heat transferred from the gas phase to the liquid phase according to the initial phase change rate and the latent heat of vaporization of the steam to obtain the energy source term; calculating the momentum loss between the gas and the liquid according to the wall viscous stress and pressure to obtain the momentum source term.

[0092] Calculating the component loss of the mixed gas during the phase change process includes: calculating the change in the component fraction of the mixed gas according to the proportional loss of the gas phase steam component during the phase change process. The change in the component fraction of the mixed gas is the combined loss of the mixed gas.

[0093] The updated phase change rate is obtained by calculating according to the mass source term, the energy source term, the momentum source term and the wall temperature, including: calculating the equilibrium pressure of the steam during the phase change according to the mass source term, the energy source term, the momentum source term and the temperature of the mixed gas; and obtaining the saturated steam pressure at the gas-liquid interface by calculating according to the equilibrium pressure of the steam during the phase change and the wall temperature, thereby obtaining the updated phase change rate.

[0094] After obtaining the condensate generation rate on the wall unit at each moment, an iterative calculation is performed to obtain the accumulation and distribution of the wall condensate at different moments.

[0095] In the embodiment of the present invention, the control equation is as follows:

[0096]

[0097] The mass source term of the condensate is calculated as:

[0098]

[0099] The mass source term of the steam phase is calculated as:

[0100]

[0101] The source term of the energy equation is:

[0102] S e =γS m

[0103] ρ is the density, is the fluid velocity, e t is the specific heat capacity, τ eff is the fluid viscosity, is the acceleration due to gravity, λ eff is the thermal conductivity, p is the fluid pressure, D is the mass diffusion coefficient, ω is the component mass fraction, γ is the latent heat of vaporization, V cellis the grid unit volume, A face is the wall area of ​​the unit.

[0104] is the momentum source term.

[0105] Step S104: Calculate the distribution of the liquid film on the condensation wall surface based on the condensation liquid generation rate.

[0106] In some embodiments, calculating the distribution of the liquid film on the condensation wall surface based on the condensation liquid generation rate includes: calculating the distribution of the liquid film on the condensation wall surface using a liquid film model based on the condensation liquid generation rate.

[0107] In some embodiments, based on the condensate generation rate, the liquid film model is used to calculate the distribution of the liquid film on the condensation wall surface, including: establishing a liquid film subgrid in the first calculation unit of the wall surface; determining the condensate generation rate as the inlet velocity boundary condition of the liquid film subgrid; in the liquid film subgrid, calculating the flow and heat conduction of the liquid film, and obtaining the liquid film velocity, thickness and temperature distribution; calculating according to the interface energy balance between the liquid film and the gas phase, and obtaining the liquid-gas phase change rate; obtaining the average velocity of the liquid film, and determining the average velocity of the liquid film as the outlet velocity boundary condition of the liquid film subgrid; calculating the single-phase flow in the external flow field; iteratively calculating the internal and external flow fields based on the liquid film velocity, thickness and temperature distribution, and the single-phase flow, and obtaining the coupled solution of the liquid film and the gas phase flow; the coupled solution of the liquid film and the gas phase flow is the distribution of the liquid film on the condensation wall surface. Among them, the calculation unit here is a divided grid, which includes nodes and interfaces used for calculation.

[0108] Specifically, a liquid film subgrid is established in the first calculation unit near the wall to calculate the heat transfer and flow of the liquid film; the condensate generation rate obtained by the wall source term is used as the inlet velocity boundary condition of the liquid film subgrid; in the liquid film subgrid, the flow and heat conduction of the liquid film are calculated to obtain the liquid film velocity, thickness and temperature distribution; the liquid-gas phase change rate between the liquid film and the gas phase is calculated according to the interface energy balance to achieve heat and mass exchange; then the average velocity of the liquid film is used as the outlet velocity boundary condition to achieve coupling with the external flow field, and in the external flow field, the liquid film is treated as air, and single-phase flow calculations are performed using Fluent software; finally, through iterative calculations of internal and external flow fields, the coupled solution of the liquid film and gas phase flow is obtained, that is, the coupled solution of the liquid film and gas phase flow is the distribution of the liquid film on the condensation wall.

[0109] Step S105: According to the distribution of the condensation wall, by adjusting the calculation conditions and analyzing the wall condensation law under different steam conditions, the condensate retention data of the condensation wall is obtained.

[0110] In some embodiments, according to the distribution of the condensation wall, by adjusting the calculation conditions, analyzing the wall condensation law under different steam conditions, obtaining the condensate retention data of the condensation wall includes: determining the parameters affecting the condensation; respectively setting different values ​​of the parameters affecting the condensation to obtain multiple groups of calculation conditions; performing numerical simulation of the condensate retention for each group of calculation conditions according to the distribution of the condensation wall, analyzing the variation law of the wall condensation under different conditions, and obtaining the condensate retention data of the condensation wall. Among them, the parameters affecting the condensation include but are not limited to the inlet steam temperature, pressure, velocity and humidity.

[0111] refer to Figure 2 , Figure 2 This is a principle block diagram of the nuclear power plant condensate holdup calculation device provided by the present invention.

[0112] Specifically, Figure 2 As shown, the nuclear power plant condensate retention calculation device includes:

[0113] The model building unit 201 is used to establish a condensate retention analysis geometric model for the object to be analyzed, and to mesh the geometric model to obtain a three-dimensional mesh model.

[0114] The phase change calculation unit 202 is used to calculate the three-dimensional grid model using a single-phase multi-component model to obtain the flow field and component distribution of the gas-liquid two-phase during the phase change process.

[0115] The condensate generation rate calculation unit 203 is used to calculate the condensate generation rate on the condensate wall surface based on the flow field and component distribution of the gas-liquid two-phase in the phase change process and the control equation of the object to be analyzed on the condensate wall surface.

[0116] The liquid film distribution calculation unit 204 is used to calculate the distribution of the liquid film on the condensation wall surface based on the condensation liquid generation rate.

[0117] The condensate retention calculation unit 205 is used to obtain the condensate retention data of the condensate wall by adjusting the calculation conditions according to the distribution of the condensate wall surface and analyzing the wall condensation law under different steam conditions.

[0118] Specifically, the specific coordination operation process between the various units in the nuclear power plant condensate retention amount calculation device here can refer to the above-mentioned nuclear power plant condensate retention amount calculation method, which will not be repeated here.

[0119] The present invention can quantitatively predict and evaluate the accumulation of condensate under different structures and working conditions, and provide a reference for structural design and process optimization. The established mathematical model and calculation method can be extended and applied to the analysis of other similar condensation processes, and can deeply reveal the physical mechanism of the condensation process, such as phase change dynamics, heat transfer law, etc., to obtain a better understanding of the process. It can replace part of the experimental research, reduce the R&D cost, shorten the product design cycle, provide the quantitative relationship of the influence of various parameters on the condensation amount, establish the condensation amount prediction model, guide the engineering design and operation, and can replace the field test with virtual simulation analysis to avoid damage to the equipment and accident risks, which is helpful to optimize the operating parameters, reduce the accumulation of condensate, and reduce the probability of equipment damage and accidents. It can calculate the liquid film distribution law, optimize the inner surface of the structure, and reduce the problem of liquid film blockage.

[0120] The following is an explanation using the containment shell as an example.

[0121] Specifically, in the embodiment of the present invention, the condensation process in the containment is simulated by a single-phase multi-component model, that is, the single-phase multi-component model is used as the condensate calculation model, which can obtain the condensate generation rate on the wall (i.e., the condensate generation rate), and further adopt the Euler liquid film model with the condensate generation rate as the input condition to calculate the distribution of the liquid film on the condensation surface. The condensation law of the wall / floor under different steam conditions in the containment is analyzed to obtain the condensate retention data under different inclined catenary nets.

[0122] The total heat transfer from the gas phase to the tube wall is divided into two parts, one is the sensible heat transferred by natural convection, and the other is the latent heat transferred by the condensation of steam on the condensation wall. The moist heat and sensible heat are transferred to the cold fluid through the liquid film, tube wall, and dirt. The mass transfer power of steam diffusion to the heat transfer tube wall is the difference between the steam partial pressure of the gas mainstream and the saturated steam partial pressure corresponding to the liquid film temperature. When the steam diffuses to the heat transfer tube wall or the gas-liquid interface, if the temperature of the tube wall or the gas-liquid interface is lower than the steam dew point temperature, the steam condenses to form a liquid film.

[0123] The condensed water in the containment is mainly retained on each wall surface in the form of condensate film. The amount of retention is positively correlated with the surface area exposed to the steam environment. The condensation calculation domain is extracted based on the containment geometry model. The main areas where condensation occurs in the containment are the walls and floors (maintenance platform). The area below the grid platform in the containment is not included in the research scope. The surface area of ​​the spray pipe is small, and the condensate formed on its surface will drip into the pool. The existence of the pipe will cause a rapid increase in the calculation grid, so the condensate on the surface of the pipe is ignored in the calculation model. Since the bracket is small in size and is wrapped by high-temperature steam, there is less condensate on the surface, and these structures are also active in the calculation model. The remaining HVAC equipment, maintenance platform and main equipment surfaces are retained. The final geometric model is as follows Figure 3As shown. The geometric model of the containment is simplified, and the simplified geometric model is meshed. Since condensation mainly occurs at the wall, the mesh near the wall is encrypted, the number of meshes in each direction is 81×81×51, the first layer of mesh height is 1mm, and the growth factor is 1.2. Among them, the simplified geometric model is as follows Figure 4 As shown, the simplified geometric model mesh is divided as follows Figure 5 shown.

[0124] After completing the grid division, the present invention adopts a single-phase multi-component method to study the condensate retention in the containment, which can better consider the influence of non-condensable gas. In order to effectively perform the solution calculation, the following four settings are made for the air-containing steam condensation process:

[0125] (1) The influence of the liquid film during the condensation process can be ignored. The condensate is removed during the condensation process, and the focus is on the accumulation of gas near the wall and the flow field distribution in the mainstream area.

[0126] (2) The steam in the mixed gas is saturated steam at its partial pressure. The saturated steam pressure P s The relationship with the wall temperature Tw is:

[0127]

[0128] (3) Condensation only occurs in the first layer of grids near the condensation wall. After the saturated steam in the gas-phase boundary layer is cooled, droplets may appear, i.e., fog is formed. Compared with a large amount of wall condensation, the existence of droplets in the gas-phase boundary layer has only a very small effect on the mass diffusion of steam. The droplets formed in the gas-phase boundary layer can be ignored.

[0129] (4) The steam-air mixed fluid is treated as a single-phase two-component fluid. The two-component gas mixture composed of water vapor and air is assumed to be an ideal gas, and its density calculation formula is derived as follows:

[0130]

[0131] Where: mix —Mixed gas density, kg / m 3 ; R—molar gas constant; W v , W a —Water vapor, air mass fraction; M v 、M a —Molar mass of water vapor and air.

[0132] The mass diffusion coefficient of a two-component mixture is calculated by the following formula:

[0133]

[0134] In the formula: T0, P0—temperature and pressure under standard conditions, 273.15K, 101325Pa; D0—mass diffusion coefficient under standard conditions; α—value range is 1.5~2.0.

[0135] Among them, the mass diffusion coefficient is implemented using the DEFINE—IFFUSIVITY(vapor_diffusivity,c,t,i) macro of the compiled UDF and loaded in the mixture settings of the material panel.

[0136] Based on the above four assumptions, the condensation process of air-containing steam can be simplified: in the first layer of grid on the condensation wall, the convection heat transfer between the mixed gas and the wall causes the fluid temperature T to decrease, and the local steam partial pressure P is compared in the condensation wall unit. v Saturation pressure P corresponding to the wall temperature s The size of P is used to determine whether condensation occurs. v >P s Then condensation occurs, producing condensate m0, while releasing heat H0, and the condensate and latent heat are removed; otherwise, the condensation amount is zero, and only convective heat transfer exists.

[0137] The convective heat transfer is calculated by FLUENT. The phase change process of condensation will cause the mass, energy, momentum and component loss of the mixed gas phase. These losses can be simulated by adding source terms to the control equation of the condensation wall by compiling UDF. The source term values ​​in each unit near the wall are stored using UDM to calculate the latent heat released by steam at a certain moment. Among them, the wall condensation parameters are as follows: Figure 6 shown.

[0138] Governing equations:

[0139]

[0140]

[0141] The mass source term of the condensate is calculated as:

[0142]

[0143] The mass source term of the steam phase is calculated as:

[0144]

[0145] The source term of the energy equation is:

[0146] S e =γS m

[0147] ρ is density, D is mass diffusion coefficient, ω is component mass fraction, γ is latent heat of vaporization, V cellis the grid unit volume, A face is the wall area of ​​the unit.

[0148] The embodiment of the present invention adopts steady-state calculation when simulating test conditions, and the complete condensation process adopts synchronous format. The physical quantities for calculating the water vapor partial pressure of the unit near the wall and the water vapor saturation pressure corresponding to the wall temperature are all taken from the previous iterative calculation results. Whether condensation can occur is determined based on the results of the previous iterative calculation. As long as the water vapor partial pressure of the unit near the wall is greater than the water vapor saturation pressure corresponding to the wall temperature, condensation will occur in this round of iteration, and the quality of condensation, that is, the condensation rate, is calculated by the wall temperature calculated in this round of iteration.

[0149] like Figure 7 As shown in the figure, a two-dimensional model is used to verify the UDF program. Among them, the inlet velocity is 0.1m / s, the inlet temperature is 359.31K, the inlet water vapor mass fraction is 0.479673, the cold wall temperature is 330K, and the upper wall is a symmetrical wall. Figure 8 To verify the results, it can be seen that the wall condensation flux calculated in this study is almost consistent with the analytical solution in the literature, with an error of less than 20%. Figures 9 to 12 The temperature distribution cloud map, water vapor and air mass fraction cloud map, and velocity distribution cloud map of the two-dimensional model are shown in Figure 1. It can be seen that as the condensation proceeds, the water vapor mass fraction in the channel gradually decreases, and the air mass fraction gradually increases.

[0150] The present invention is based on a single-phase multi-component condensation simulation method, opens the component transport equation, uses the user-developed platform UDF (User Defined Function) of FLUENT software to realize the numerical simulation of condensation, and uses UDM (User Defined Memory) to store latent heat exchange to obtain the condensate retention amount.

[0151] When calculating the model, the calculation accuracy is double precision, the numerical method selects the pressure-based solver (Pressure Based), and the velocity-pressure coupling method adopts the implicit coupling method (Coupled Solver). This method has great advantages when the density, energy, momentum and other parameters are interdependent. The density, momentum, energy and component terms are all discretized using the second-order upwind format; the variable gradient difference method selects the Green-Gauss Cell-Based method, which is suitable for quadrilateral and hexahedral grids; the second-order implicit relationship is selected to solve the mixing process of the two-component gas to obtain a more accurate solution. The condensation wall adopts the no-slip wall boundary condition and the wall temperature distribution is given. During the simulation, the wall temperature is set on the wall where condensation occurs, and the other walls are treated as adiabatic.

[0152] The flow of liquid film on the wall is calculated using the Euler liquid film model. In the model and material settings of the Euler wall film model, the option to solve the wall film momentum needs to be activated, and the gravity option and pressure gradient option are turned on in the momentum option. Only on this basis can the extension item and surface tension item be turned on; water is selected as the working fluid for the liquid film material, and its surface tension is set to 0.07194N / m. In the time discretization and space discretization options of the Euler wall film model, in order to improve the calculation accuracy, the time, continuity and momentum discretization of the wall film are all selected as second-order discretization. Turn on the coupled solution of mass and momentum equations and curved smoothing. By default, the mass equation of the wall film is calculated first, and then the momentum equation of the wall film is calculated. When the characteristic quantity of the wall film, the wall film height, is coupled with the velocity (such as the free-falling wall film on the wave surface), the coupled solution of the simultaneous calculation of the mass and momentum equations is required. The coupled solution is mainly used in the case of curved wall film and wall film surface tension calculation.

[0153] The amount of condensate generated is closely related to the internal parameters of the containment, such as the non-condensable gas content, steam pressure, wall pressure distribution, internal flow field, etc. For the study of condensate retention, it is necessary to distinguish between the condensate generation rate and the condensate retention. When the liquid film is in dynamic equilibrium, the condensed steam forms liquid and merges into the liquid film, and the liquid film flows downward under the action of gravity. Macroscopically, the mass of the condensate entering the liquid film area is the same as the mass of the condensate leaving the liquid film, and the liquid film is in a relatively stable state. This relatively stable liquid film mass is the cooling medium condensate retention.

[0154] First, a constant condensate generation rate was used as the boundary condition to analyze the distribution of the liquid film and the retention on the wall. The calculation conditions for the condensate generation rate were: the pressure in the cavity was 0.3 MPa, the temperature difference was 50 °C, and according to the correlation formula, the average condensate generation rate on the vertical plane at a height of 6.5 m was about 0.1 kg / (m 2 s).

[0155] The calculation results of liquid film are as follows Figure 13 to Figure 16 As shown in the figure, the distribution of liquid film thickness on the wall, the distribution of liquid film flow rate, the distribution of liquid film mass and the distribution of liquid film thickness of the internal equipment are respectively shown. The liquid film is thicker at the top and near the bottom of the side wall. The condensate has a lower flow rate and a larger thickness at the top. The liquid film flows vertically downward along the side wall, and the flow rate is getting higher and higher. Due to the truncation of the maintenance platform, the liquid film is thicker above it and thinner below it.

[0156] High-temperature steam condenses when it contacts the lower-temperature shell wall, and the condensate flows down the wall to form a liquid film. From the perspective of reducing the temperature of the containment, the more condensed water produced per unit area, the more heat is lost through the containment, which helps to reduce the temperature and pressure inside the containment. However, the more condensed water produced per unit area, the thicker the water film, and the more cooling medium is retained in the containment, which reduces the water level of the circulating pump water intake pool and is not conducive to the stable operation of the system. The Euler liquid film model can be used to specify the area where the liquid film is generated. Since this model verification work only specifies the generation of liquid film on the outer surface, the thickness of the liquid film in the internal area is 0 mm. Under this condition, the liquid film retention is about 198.9 kg.

[0157] In addition, an electronic device of the present invention includes a memory and a processor; the memory is used to store a computer program; the processor is used to execute the computer program to implement a method for calculating the condensate retention of a nuclear power plant as described in any one of the above. Specifically, according to an embodiment of the present invention, the process described with reference to the flowchart above can be implemented as a computer software program. For example, an embodiment of the present invention includes a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program contains a program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed by an electronic device and when executed, it executes the above functions defined in the method of the embodiment of the present invention. The electronic device in the present invention can be a terminal such as a notebook, a desktop, a tablet computer, a smart phone, or a server.

[0158] In addition, a storage medium of the present invention stores a computer program thereon, and when the computer program is executed by a processor, any one of the above methods for calculating the condensate retention of a nuclear power plant is implemented. Specifically, it should be noted that the above storage medium of the present invention may be a computer-readable signal medium or a computer-readable storage medium or any combination of the above two. The computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any combination of the above. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present invention, a computer-readable storage medium may be any tangible medium containing or storing a program, which may be used by or in combination with an instruction execution system, device or device. In the present invention, a computer-readable signal medium may include a data signal propagated in a baseband or as part of a carrier wave, which carries a computer-readable program code. Such propagated data signals may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. Computer readable signal media may also be any computer readable medium other than computer readable storage media, which may send, propagate, or transmit programs for use by or in conjunction with an instruction execution system, apparatus, or device. The program code contained on the computer readable medium may be transmitted using any suitable medium, including but not limited to: wires, optical cables, RF (radio frequency), etc., or any suitable combination of the above.

[0159] The computer-readable medium may be included in the electronic device, or may exist independently without being incorporated into the electronic device.

[0160] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0161] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0162] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0163] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot limit the scope of protection of the present invention. All equivalent changes and modifications made to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for calculating the condensate holdup in a nuclear power plant, characterized in that: The following steps are involved: Establishing a condensate retention analysis geometric model for the object to be analyzed, and meshing the geometric model to obtain a three-dimensional mesh model; The three-dimensional grid model is calculated using a single-phase multi-component model to obtain the flow field and component distribution of the gas-liquid two-phase during the phase change process; Based on the flow field and component distribution of the gas-liquid two-phase in the phase change process, combined with the control equation of the object to be analyzed on the condensation wall surface, calculation is performed to obtain the condensate generation rate on the condensation wall surface; Calculating the distribution of the liquid film on the condensation wall surface based on the condensate generation rate; According to the distribution of the condensation wall surface, by adjusting the calculation conditions and analyzing the wall condensation law under different steam conditions, the condensate retention data of the condensation wall surface is obtained.

2. The method for calculating the condensate retention in a nuclear power plant according to claim 1, characterized in that: The step of establishing a condensate retention analysis geometric model for the object to be analyzed and meshing the geometric model to obtain a three-dimensional mesh model includes: Establishing a three-dimensional geometric model of the object to be analyzed according to the structural shape and size of the object to be analyzed; Simplifying the three-dimensional geometric model according to the structural function and working conditions of the object to be analyzed to obtain a simplified three-dimensional model; Meshing the simplified three-dimensional model to obtain an initial mesh model; The initial mesh model is processed to obtain the three-dimensional mesh model.

3. The method for calculating the condensate retention in a nuclear power plant according to claim 2, characterized in that: The processing of the initial mesh model to obtain the three-dimensional mesh model comprises: Extracting a fluid calculation domain required for calculation from the initial grid model; Smoothing and optimizing the fluid computational domain grid; The inlet condition, outlet condition and wall boundary condition of the fluid calculation domain grid are determined, the grid division is completed, and the three-dimensional grid model is obtained.

4. The method for calculating the condensate retention in a nuclear power plant according to claim 1, characterized in that: The method of calculating the three-dimensional grid model using a single-phase multi-component model to obtain the flow field and component distribution of the gas-liquid two-phase in the phase change process includes: During condensation, determine the single-phase multi-component fluid; Determine whether the fluid has reached equilibrium; If so, the condensation transition of the vapor component in the gas phase to the liquid phase is completed through the coupling of the wall source term; Calculate the mixed gas parameters of the three-dimensional grid model based on the single-phase multi-component model; Iterative calculation is performed to obtain the flow field and component distribution of the gas-liquid two-phase during the phase change process.

5. The method for calculating the condensate retention in a nuclear power plant according to claim 1, characterized in that: The calculation based on the flow field and component distribution of the gas-liquid two-phase in the phase change process and the control equation of the object to be analyzed on the condensation wall surface to obtain the condensate generation rate on the condensation wall surface includes: Based on the flow field and component distribution of the gas-liquid two-phase during the phase change process, calculate the latent heat released by the steam at any time; Simulating the mass source term, energy source term and momentum source term of the mixed gas in the phase change process according to the control equation of the condensation wall; Calculate the component loss of mixed gas during phase change; Calculating according to the mass source term, the energy source term, the momentum source term, and in combination with the wall temperature, to obtain an updated phase change rate; Calculating according to the updated phase change rate and the latent heat to obtain the condensate generation rate on the wall unit at each moment; Iterative calculation is performed to obtain the condensate generation rate on the condensation wall surface at different times.

6. The method for calculating the condensate retention in a nuclear power plant according to claim 5, characterized in that: The mass source term, energy source term and momentum source term of the mixed gas in the phase change process simulated according to the control equation of the condensation wall include: The following calculations are performed based on the governing equations of the condensation wall: Calculate the mass transfer of the gas phase steam component to the liquid phase water component according to the initial phase change rate to obtain the mass source term; Calculate the heat transferred from the gas phase to the liquid phase according to the initial phase change rate and the latent heat of vaporization of the steam to obtain the energy source term; The momentum source term is obtained by calculating the momentum loss between the gas and the liquid according to the wall viscous stress and the pressure.

7. The method for calculating the condensate retention of a nuclear power plant according to claim 5, characterized in that: The calculation of the component loss of the mixed gas during the phase change process includes: During the phase change process, the change in the component fraction of the mixed gas is calculated based on the proportional loss of the gas phase steam components; the change in the component fraction of the mixed gas is the combined loss of the mixed gas.

8. The method for calculating the condensate retention in a nuclear power plant according to claim 5, characterized in that: The step of calculating according to the mass source term, the energy source term, the momentum source term and in combination with the wall temperature to obtain an updated phase change rate includes: Calculating the equilibrium pressure of the steam during phase change according to the mass source term, the energy source term, the momentum source term and the temperature of the mixed gas; The saturated steam pressure at the gas-liquid interface is obtained by calculating the equilibrium pressure of the steam during the phase change in combination with the wall temperature, and the updated phase change rate is obtained.

9. The method for calculating the condensate retention of a nuclear power plant according to claim 1, characterized in that: The calculating the distribution of the liquid film on the condensation wall surface based on the condensation liquid generation rate includes: Based on the condensate generation rate, a liquid film model is used to calculate the distribution of the liquid film on the condensate wall surface.

10. The method for calculating the condensate retention in a nuclear power plant according to claim 9, characterized in that: The method of calculating the distribution of the liquid film on the condensation wall surface using a liquid film model based on the condensation liquid generation rate includes: Create a liquid film subgrid in the first computational cell on the wall; Determining the condensate generation rate as an inlet velocity boundary condition of the liquid film subgrid; In the liquid film subgrid, the flow and heat conduction of the liquid film are calculated to obtain the liquid film velocity, thickness and temperature distribution; The liquid-gas phase change rate is obtained by calculating the interfacial energy balance between the liquid film and the gas phase; Obtaining an average velocity of the liquid film, and determining the average velocity of the liquid film as an outlet velocity boundary condition of the liquid film subgrid; Calculate single-phase flow in the external flow field; Based on the liquid film velocity, thickness and temperature distribution, the single-phase flow performs iterative calculation of internal and external flow fields to obtain a coupling solution of the liquid film and gas phase flow; the coupling solution of the liquid film and gas phase flow is the distribution of the liquid film on the condensation wall.

11. The method for calculating the condensate retention of a nuclear power plant according to claim 1, characterized in that: According to the distribution of the condensation wall surface, by adjusting the calculation conditions and analyzing the wall condensation law under different steam conditions, the condensate retention data of the condensation wall surface is obtained, which includes: Determine the parameters that affect condensation; Different values ​​of the parameters affecting condensation are set respectively to obtain multiple groups of calculation conditions; According to the distribution of the condensation wall surface, numerical simulation of the condensate retention amount is performed for each group of calculation conditions, and the variation law of the wall condensation amount under different conditions is analyzed to obtain the condensate retention amount data of the condensation wall surface.

12. A device for calculating the condensate retention in a nuclear power plant, characterized in that: include: A model building unit, used to establish a condensate retention analysis geometric model for the object to be analyzed, and to mesh the geometric model to obtain a three-dimensional mesh model; A phase change calculation unit, used to calculate the three-dimensional grid model using a single-phase multi-component model to obtain the flow field and component distribution of the gas-liquid two-phase during the phase change process; A condensate generation rate calculation unit, used to calculate based on the flow field and component distribution of the gas-liquid two-phase in the phase change process, combined with the control equation of the object to be analyzed on the condensation wall surface, to obtain the condensate generation rate on the condensation wall surface; A liquid film distribution calculation unit, used to calculate the distribution of the liquid film on the condensation wall surface based on the condensate generation rate; The condensate retention calculation unit is used to obtain the condensate retention data of the condensate wall by adjusting the calculation conditions according to the distribution of the condensate wall surface and analyzing the wall condensation law under different steam conditions.

13. A storage medium, characterized in that: The storage medium stores a computer program, and the computer program is suitable for being loaded by a processor to execute the steps of the method for calculating the condensate retention amount of a nuclear power plant as described in any one of claims 1 to 11.

14. An electronic device, characterized in that: It comprises a memory and a processor, wherein the memory stores a computer program, and the processor executes the steps of the method for calculating the condensate retention amount of a nuclear power plant as claimed in any one of claims 1 to 11 by calling the computer program stored in the memory.

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