Method and device for calculating nuclear power plant condensate holdup, storage medium and electronic equipment

Abstract

The present application relates to a kind of nuclear power plant condensate retention quantity calculation method, device, storage medium and electronic equipment, comprising: the establishment of the condensate retention quantity analysis geometric model of to-be-analyzed object, and the grid division of geometric model obtains three-dimensional grid model;Using single-phase multi-component model, three-dimensional grid model is calculated, obtains the flow field and component distribution of gas-liquid two-phase in phase change process;Based on the flow field and component distribution of gas-liquid two-phase in phase change process, combined with the control equation of to-be-analyzed object on condensing wall surface, the condensate production rate on condensing wall surface is obtained;Based on the distribution of condensate production rate calculation liquid film on condensing wall surface;According to the distribution of condensing wall surface, the wall surface condensation law under different steam conditions is analyzed by adjusting calculation condition, and the condensate retention quantity data of condensing wall surface is obtained.The present application can quantitatively predict and evaluate the condensate accumulation under different structures and working conditions, avoid the damage and accident risk to equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nuclear power plant condensation heat transfer simulation, and more particularly, to a nuclear power plant condensate retention amount calculation method and device, a storage medium and an electronic device. BACKGROUND

[0002] Containment spray system is an important guarantee system of nuclear power plant, which can spray cooling medium to the containment to evaporate and cool when the containment is in accident condition, so as to control the pressure and temperature inside the containment within the permissible range.

[0003] The spray system needs to suck water from the pit in the recirculation spray stage. In order to ensure the safe operation of the containment spray pump, it is necessary to ensure that there is enough effective net positive suction head at the inlet of the pump. Therefore, it is necessary to ensure that the liquid level after the containment spray pump takes water meets the requirement of the minimum water storage amount of the containment spray pump, and the quantitative analysis of the water loss amount of the containment spray pool under accident condition is the key. The water loss amount mainly includes containment leakage water amount, containment spray pump backflow tolerance loss, containment retention water amount, etc. Since the retention water amount is affected by many factors such as water film thickness and pressure, it is difficult to calculate the condensate water on the wall / floor. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a nuclear power plant condensate retention amount calculation method, device, storage medium and electronic device to solve the problems in the prior art.

[0005] The technical solution adopted by the present application to solve the technical problem is that a nuclear power plant condensate retention amount calculation method is constructed, comprising the following steps:

[0006] A condensate retention amount analysis geometric model of the object to be analyzed is established, and the geometric model is meshed to obtain a three-dimensional grid model;

[0007] 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 in the phase change process;

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

[0009] Based on the condensate production rate, the distribution of the liquid film on the condensation wall is calculated;

[0010] According to the distribution of the condensation wall, the calculation conditions are adjusted to analyze the wall condensation law under different steam conditions, and the condensate retention amount data of the condensation wall are obtained.

[0011] In the nuclear power plant condensate retention amount calculation method, the condensate retention amount analysis geometric model of the to-be-analyzed object is established, and the geometric model is meshed to obtain a three-dimensional grid model, which comprises:

[0012] According to the structure shape and size of the to-be-analyzed object, a three-dimensional geometric model of the to-be-analyzed object is established;

[0013] According to the structure function and working condition of the to-be-analyzed object, the three-dimensional geometric model is simplified to obtain a simplified three-dimensional model;

[0014] The simplified three-dimensional model is meshed to obtain an initial grid model;

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

[0016] In the nuclear power plant condensate retention amount calculation method, the initial grid model is processed to obtain the three-dimensional grid model, which comprises:

[0017] The fluid calculation domain required for calculation is extracted from the initial grid model;

[0018] The fluid calculation domain grid is smoothed and optimized;

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

[0020] In the nuclear power plant condensate retention amount calculation method, the three-dimensional grid model is calculated by 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, which comprises:

[0021] In the condensation process, a single-phase multi-component fluid is determined;

[0022] It is judged whether the fluid reaches an equilibrium state;

[0023] If yes, 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] The mixed gas parameters of the three-dimensional grid model are calculated 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 in the phase change process.

[0026] In the nuclear power plant condensate retention amount calculation method, the calculation based on the flow field and the component distribution of the gas-liquid two-phase in the phase change process, combined with the control equation of the to-be-analyzed object on the condensing wall surface, obtains the condensate generation rate on the condensing wall surface, including:

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

[0028] According to the control equation of the condensing wall surface, the mass source term, the energy source term and the momentum source term of the mixed gas in the phase change process are simulated.

[0029] The component loss of the mixed gas in the phase change process is calculated.

[0030] According to the mass source term, the energy source term, the momentum source term, and combined with the wall surface temperature, the updated phase change rate is calculated.

[0031] According to the updated phase change rate and the latent heat, the condensate generation rate on the wall surface unit at each time is obtained.

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

[0033] In the nuclear power plant condensate retention amount calculation method, the calculation based on the flow field and the component distribution of the gas-liquid two-phase in the phase change process, combined with the control equation of the to-be-analyzed object on the condensing wall surface, obtains the condensate generation rate on the condensing wall surface, including:

[0034] Based on the control equation of the condensing wall surface, the following calculations are performed:

[0035] According to the initial phase change rate, the mass transfer of the gas phase steam component to the liquid phase water component is calculated to obtain the mass source term;

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

[0037] According to the wall surface viscous stress and pressure, the momentum loss between the gas and the liquid is calculated to obtain the momentum source term.

[0038] In the nuclear power plant condensate retention amount calculation method, the calculation of the component loss of the mixed gas in the phase change process includes:

[0039] In the phase change process, according to the proportional loss of the gas phase steam component, the change of the component fraction of the mixed gas is calculated; the change of the component fraction of the mixed gas is the combined loss of the mixed gas.

[0040] In the nuclear power plant condensate retention amount calculation method, the calculation according to the mass source term, the energy source term, the momentum source term and the wall temperature comprises:

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

[0042] The saturation vapor pressure at the gas-liquid interface is calculated according to the equilibrium pressure of steam during phase change and the wall temperature, and the updated phase change rate is obtained.

[0043] In the nuclear power plant condensate retention amount calculation method, the calculation of the distribution of the liquid film on the condensing wall based on the condensate generation rate comprises:

[0044] The distribution of the liquid film on the condensing wall is calculated based on the condensate generation rate and a liquid film model.

[0045] In the nuclear power plant condensate retention amount calculation method, the calculation of the distribution of the liquid film on the condensing wall based on the condensate generation rate and a liquid film model comprises:

[0046] A liquid film sub-grid is established in the first calculation unit of the wall;

[0047] The condensate generation rate is determined as the inlet velocity boundary condition of the liquid film sub-grid;

[0048] The flow and heat conduction of the liquid film are calculated in the liquid film sub-grid to obtain the velocity, thickness and temperature distribution of the liquid film;

[0049] The liquid-gas phase change rate is calculated according to the interfacial energy balance between the liquid film and the gas phase;

[0050] The average velocity of the liquid film is obtained, and the average velocity of the liquid film is determined as the outlet velocity boundary condition of the liquid film sub-grid;

[0051] The single-phase flow is calculated in the outer flow field;

[0052] The liquid film and gas phase flow coupling solution is obtained by iterative calculation of the inner and outer flow fields based on the velocity, thickness and temperature distribution of the liquid film and the single-phase flow; the liquid film and gas phase flow coupling solution is the distribution of the liquid film on the condensing wall.

[0053] In the nuclear power plant condensate retention amount calculation method, the calculation of the condensate retention amount data of the condensing wall according to the distribution of the condensing wall and by adjusting the calculation conditions to analyze the wall condensation law under different steam conditions comprises:

[0054] determining parameters affecting condensation;

[0055] different values of the parameters affecting condensation are set respectively, and a plurality of groups of calculation conditions are obtained;

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

[0057] The application further provides a nuclear power plant condensate retention amount calculation device, comprising:

[0058] a model construction unit, configured to establish a condensate retention amount analysis geometric model of an object to be analyzed, and perform grid division on the geometric model to obtain a three-dimensional grid model;

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

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

[0061] a liquid film distribution calculation unit, configured to calculate distribution of liquid film on the condensing wall surface based on the condensate generation rate;

[0062] a condensate retention amount calculation unit, configured to analyze wall condensation law under different steam conditions according to the distribution of the condensing wall surface by adjusting calculation conditions, and obtain condensate retention amount data of the condensing wall surface.

[0063] The application further provides a storage medium, which stores a computer program, and the computer program is suitable for being loaded by a processor to execute steps of the nuclear power plant condensate retention amount calculation method.

[0064] The application further provides an electronic device, which comprises a memory and a processor, and the memory stores a computer program, and the processor executes steps of the nuclear power plant condensate retention amount calculation method by calling the computer program stored in the memory.

[0065] The nuclear power plant condensate retention amount calculation method, device, storage medium and electronic equipment provided by the present application have the following beneficial effects: a condensate retention amount analysis geometric model of an object to be analyzed is established, and the geometric model is meshed to obtain a three-dimensional mesh model; a single-phase multi-component model is used 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, the control equation of the object to be analyzed on the condensing wall surface is combined to calculate the condensate generation rate on the condensing wall surface; the distribution of the liquid film on the condensing wall surface is calculated based on the condensate generation rate; according to the distribution of the condensing wall surface, the wall condensation law under different steam conditions is analyzed by adjusting the calculation conditions, and the condensate retention amount data of the condensing wall surface are obtained. The present application can quantitatively predict and evaluate the condensate accumulation under different structures and working conditions, and avoid damage to the equipment and accident risks. BRIEF DESCRIPTION OF DRAWINGS

[0066] The present application will be further described below in combination with the drawings and examples, and the drawings are as follows:

[0067] Figure 1 FIG. 1 is a flowchart of the nuclear power plant condensate retention amount calculation method provided by the present application;

[0068] Figure 2 FIG. 2 is a principle block diagram of the nuclear power plant condensate retention amount calculation device provided by the present application;

[0069] Figure 3 FIG. 3 is a geometric model of a containment in an embodiment of the present application;

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

[0071] Figure 5 FIG. 5 is a meshing diagram of the simplified model in an embodiment of the present application;

[0072] Figure 6 FIG. 6 is a wall condensation parameter diagram in an embodiment of the present application;

[0073] Figure 7 FIG. 7 is a two-dimensional calculation domain and mesh diagram in an embodiment of the present application;

[0074] Figure 8 FIG. 8 is a wall condensation flux verification result in an embodiment of the present application;

[0075] Figure 9 FIG. 9 is a temperature distribution nephogram in an embodiment of the present application;

[0076] Figure 10 FIG. 10 is a water vapor mass fraction nephogram in an embodiment of the present application;

[0077] Figure 11 is a dry air mass fraction cloud chart in an embodiment of the present application;

[0078] Figure 12 is a velocity distribution cloud chart in an embodiment of the present application;

[0079] Figures 13-16 is a liquid film calculation result in an embodiment of the present application. DETAILED DESCRIPTION

[0080] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0081] The present application can analyze the condensation law in detail by constructing a residence amount geometric model, reasonably simplifying the geometric model according to the structure function and working environment, and establishing a condensate residence amount numerical simulation model based on the geometric model, thereby providing guidance for condensate residence amount analysis of an object to be analyzed. The object to be analyzed can be a containment vessel or other geometric structure, for example, a nozzle, auxiliary equipment, nozzle mounting bracket, etc.

[0082] Specifically, as shown in Figure 1 In one preferred embodiment, the condensate residence amount calculation method of the nuclear power plant comprises the following steps:

[0083] Step S101: Establish a condensate residence amount analysis geometric model of the object to be analyzed, and divide the geometric model into grids to obtain a three-dimensional grid model.

[0084] Optionally, in some embodiments, establishing a condensate residence amount analysis geometric model of the object to be analyzed and dividing the geometric model into grids to obtain a three-dimensional grid model comprises: establishing a three-dimensional geometric model of the object to be analyzed according to the structure shape and size of the object to be analyzed; simplifying the three-dimensional geometric model according to the structure function and working condition of the object to be analyzed to obtain a simplified three-dimensional model; dividing the simplified three-dimensional model into grids to obtain an initial grid model; and processing the initial grid model to obtain a three-dimensional grid model. The three-dimensional geometric model can be established by a CAD software.

[0085] The processing of the initial grid model to obtain a three-dimensional grid model comprises: extracting a fluid calculation domain required for calculation from the initial grid model; smoothing and optimizing the fluid calculation domain grid; determining the inlet condition, outlet condition and wall boundary condition of the fluid calculation domain grid, completing the 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, to obtain the flow field and component distribution of the gas-liquid two-phase in the phase change process.

[0087] Optionally, in some embodiments, using a single-phase multi-component model to calculate the three-dimensional grid model, to obtain the flow field and component distribution of the gas-liquid two-phase in the phase change process includes: in the condensation process, determining a single-phase multi-component fluid; judging whether the fluid reaches an equilibrium state; if yes, completing the condensation transition of the vapor 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; performing iterative calculation to obtain the flow field and component distribution of the gas-liquid two-phase in the phase change process.

[0088] Specifically, in the condensation process, the vapor-air mixed gas is regarded as a single-phase multi-component fluid. When each component in the gas phase reaches complete mixing, the single-phase multi-component fluid is in an equilibrium state. When the single-phase multi-component fluid is in the equilibrium state, the condensation transition of the vapor 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, and thermal conductivity of the mixed gas) are calculated. Finally, through iterative calculation, the flow field and component distribution of the gas-liquid two-phase in the phase change process are obtained. The source term is a generalized quantity, which represents the sum of all other terms in the non-steady term, the convection term, and the diffusion term that cannot be included in the control equation. The addition of the source term is of great significance to the universality of the algorithm and the corresponding program discussed. If the source term is constant, it will not bring any difficulty in the establishment of the discrete equation. Generally, the source term is not constant, and is a function of the unknown quantity sought.

[0089] Step S103: based on the flow field and component distribution of the gas-liquid two-phase in the phase change process, combining the control equation of the object to be analyzed on the condensation wall surface, to calculate the condensate production 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 in the phase change process, combining the control equation of the object to be analyzed on the condensation wall surface, to calculate the condensate production rate on the condensation wall surface includes: based on the flow field and component distribution of the gas-liquid two-phase in the phase change process, calculating the latent heat released by the vapor 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 surface; calculating the component loss of the mixed gas in the phase change process; calculating the updated phase change rate according to the mass source term, energy source term, and momentum source term, and combining the wall surface temperature; calculating the condensate production rate on the wall surface unit at each time according to the updated phase change rate and the latent heat; performing iterative calculation to obtain the condensate production rate on the condensation wall surface at different times.

[0091] In some embodiments, simulating the mass source term, the energy source term and the momentum source term of the mixed gas in the phase change process according to the control equation of the condensation wall surface comprises: performing the following calculation based on the control equation of the condensation wall surface: calculating the mass transfer of the vapor component in the gas phase to the water component in the liquid phase 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 vapor to obtain the energy source term; and calculating the momentum loss between the gas and the liquid according to the viscous stress and the pressure of the wall surface to obtain the momentum source term.

[0092] In some embodiments, calculating the component loss of the mixed gas in the phase change process comprises: calculating the change of the component fraction of the mixed gas according to the proportional loss of the vapor component in the gas phase during the phase change process. The change of the component fraction of the mixed gas is the combined loss of the mixed gas.

[0093] According to the mass source term, the energy source term and the momentum source term, and in combination with the wall surface temperature, calculating the updated phase change rate comprises: calculating the equilibrium pressure of the vapor during the phase change according to the mass source term, the energy source term and the momentum source term and the temperature of the mixed gas; and calculating the saturation vapor pressure at the gas-liquid interface according to the equilibrium pressure of the vapor during the phase change in combination with the wall surface temperature to obtain the updated phase change rate.

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

[0095] In the embodiments of the present application, the control equation is as follows:

[0096]

[0097] The mass source term calculation method of the condensate is as follows:

[0098]

[0099] The mass source term calculation method of the vapor gas phase is as follows:

[0100]

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

[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 viscous force, is the gravitational acceleration, 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 cellA is the volume of the grid cell face A is the wall area of the cell.

[0104] A is the momentum source term.

[0105] Step S104: Based on the condensate production rate, the distribution of the liquid film on the condensing wall is calculated.

[0106] In some embodiments, based on the condensate production rate, the distribution of the liquid film on the condensing wall is calculated by using a liquid film model based on the condensate production rate.

[0107] In some embodiments, based on the condensate production rate, the distribution of the liquid film on the condensing wall is calculated by using a liquid film model based on the condensate production rate.

[0108] Specifically, a liquid film sub-grid is established in the first calculation unit near the wall for calculating the heat transfer and flow of the liquid film; the condensate production rate obtained from the wall source term is used as the inlet velocity boundary condition of the liquid film sub-grid; in the liquid film sub-grid, 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 realize heat and mass exchange; then the average velocity of the liquid film is used as the outlet velocity boundary condition to realize coupling with the outer flow field, and in the outer flow field, the liquid film is treated as air to calculate the single-phase flow using Fluent software; finally, through the iterative calculation of the inner and outer flow fields, the coupling solution of the liquid film and the gas phase flow is obtained, i.e. the coupling solution of the liquid film and the gas phase flow is the distribution of the liquid film on the condensing wall.

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

[0110] In some embodiments, according to the distribution of the condensing wall surface, the wall surface condensation law under different steam conditions is analyzed by adjusting the calculation conditions, and the condensate retention amount data of the condensing wall surface is obtained, including: determining the parameters affecting condensation; setting different values of the parameters affecting condensation respectively, obtaining multiple sets of calculation conditions; according to the distribution of the condensing wall surface, numerical simulation of the condensate retention amount is performed on each set of calculation conditions, the change law of the wall surface condensation amount under different conditions is analyzed, and the condensate retention amount data of the condensing wall surface is obtained. The parameters affecting condensation include, but are not limited to, inlet steam temperature, pressure, velocity, humidity, etc.

[0111] Reference Figure 2 , Figure 2 A principle block diagram of a nuclear power plant condensate retention amount calculation device provided by the present application is shown.

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

[0113] A model construction unit 201 is configured to establish a condensate retention amount analysis geometric model of an object to be analyzed, and perform grid division on the geometric model to obtain a three-dimensional grid model.

[0114] A phase change calculation unit 202 is configured to calculate the three-dimensional grid model by 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.

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

[0116] A liquid film distribution calculation unit 204 is configured to calculate the distribution of the liquid film on the condensing wall surface based on the condensate generation rate.

[0117] A condensate retention amount calculation unit 205 is configured to analyze the wall surface condensation law under different steam conditions by adjusting the calculation conditions according to the distribution of the condensing wall surface, and obtain the condensate retention amount data of the condensing wall surface.

[0118] Specifically, the specific cooperation process between each unit in the nuclear power plant condensate retention amount calculation device can refer to the above-mentioned nuclear power plant condensate retention amount calculation method, which will not be described here.

[0119] The condensate accumulation under different structures and working conditions can be quantitatively predicted and evaluated through the application, reference for structure design and process optimization is provided, the mathematical model and calculation method can be popularized and applied to the analysis of other similar condensation processes, the physical mechanism of the condensation process, such as phase change dynamics and heat transfer law, can be revealed in depth, better understanding of the process can be obtained, part of experimental research can be replaced, development cost is reduced, product design cycle is shortened, the quantitative relationship of various parameters on the condensation amount can be provided, the condensation amount prediction model is established, engineering design and operation are guided, virtual simulation analysis can be used to replace field test, damage to equipment and accident risk are avoided, optimization of operation parameters is helpful, condensate accumulation is reduced, and the probability of equipment damage and accident occurrence is reduced, the liquid film distribution law can be calculated, the inner surface of the structure is optimized, and the liquid film blocking problem is reduced.

[0120] The following is described taking a containment vessel as an example.

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

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

[0123] The condensate in the containment vessel mainly stays on the wall surface in the form of a condensate film, and the amount of retention is directly related to the surface area exposed to the steam environment, the condensation calculation domain is extracted based on the geometric model of the containment vessel. The main condensation area in the containment vessel is the wall surface and the floor (the maintenance platform), the area below the grid platform in the containment vessel is not included in the research scope. The surface area of the spray pipeline is small, the condensate formed on the surface will drip into the pool, and the pipeline will cause rapid increase of the calculation grid, so the condensate on the surface of the pipeline is ignored in the calculation model. Since the size of the support is small and it is wrapped by high-temperature steam, the condensate on the surface is small, so these structures are also ignored in the calculation model. The remaining heating and ventilation equipment, the maintenance platform and the surface of the main equipment are retained. The final geometric model is as follows Figure 3The simplified geometric model of the containment is shown in Fig. 1, and the meshing of the simplified geometric model is shown in Fig. 2. Since condensation mainly occurs at the wall surface, the grids near the wall surface are encrypted, and the number of grids in each direction is 81x81x51, the height of the first layer of grids is 1mm, and the growth factor is 1.2. The simplified geometric model is shown in Fig. 1, and the meshing of the simplified geometric model is shown in Fig. 2. Figure 4 The simplified geometric model is shown in Fig. 1, and the meshing of the simplified geometric model is shown in Fig. 2. Figure 5 The simplified geometric model is shown in Fig. 1, and the meshing of the simplified geometric model is shown in Fig. 2.

[0124] After meshing, the present application uses 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 calculation, the following four points are set for the steam condensation process containing air:

[0125] (1) The influence of liquid film during condensation can be ignored, and the condensate is removed during condensation, and the accumulation of gas near the wall surface and the flow field distribution in the main flow area are mainly studied;

[0126] (2) The steam in the mixed gas is saturated steam under its partial pressure, and the relationship between the saturated steam pressure P s and the wall surface temperature Tw is as follows:

[0127]

[0128] (3) Condensation only occurs in the first layer of grids near the condensation wall, and after the saturated steam in the gas phase boundary layer is cooled, liquid droplets, i.e. fog, may also be formed. Compared with a large amount of wall condensation, the existence of liquid droplets in the gas phase boundary layer only has a very small influence on the mass diffusion of steam, and the liquid 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, and the two-component gas mixture composed of water vapor and air is assumed to be an ideal gas, and the density calculation formula is derived as follows:

[0130]

[0131] In the formula, p mix is the density of the mixed gas, kg / m 3 ; R is the molar gas constant; W v , W a are the mass fractions of water vapor and air; M v , M a are the molar masses of water vapor and air.

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

[0133]

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

[0135] Wherein, the mass diffusion coefficient is realized by using the DEFINE—IFFUSIVITY (vapor_diffusivity, c, t, i) macro compiled by UDF, and is loaded in the mixture setting of the material panel.

[0136] According to the above four assumptions, the air-containing steam condensation process can be simplified: in the first layer of grid in the condensing wall surface, the convective heat transfer between the mixed gas and the wall surface causes the fluid temperature T to decrease, and the local vapor partial pressure P v corresponding to the wall surface temperature is compared with the saturated pressure P s to determine whether condensation occurs, if P v >P s , condensation occurs, and condensate m0 is generated, and heat H0 is released, 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, and the phase change process of condensation causes the mass, energy, momentum and component loss of the mixed gas phase, and these losses can be simulated by adding source terms in the control equations of the condensing wall surface by compiling UDF, and the source term values in the cells near the wall surface are stored by UDM, which are used to calculate the latent heat released by the steam at a moment. Wherein, the wall condensation parameters are shown as shown in Figure 6 .

[0138] Control equation:

[0139]

[0140]

[0141] The mass source term calculation method of the condensate is:

[0142]

[0143] The mass source term calculation method of the steam gas phase is:

[0144]

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

[0146] S e = γS m

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

[0148] In the simulation of the test working condition, the embodiment of the present application adopts steady-state calculation, and the complete condensation process adopts a synchronous format. The physical quantities corresponding to the water vapor saturation pressure of the water vapor partial pressure and the wall surface temperature of the near-wall surface unit are all taken from the previous iteration calculation result. Whether condensation occurs is determined according to the iteration calculation result of the previous round. As long as the water vapor partial pressure of the near-wall surface unit is greater than the water vapor saturation pressure corresponding to the wall surface temperature, the iteration of the present round will occur condensation, and the mass of the condensation, that is, the condensation rate, is calculated by the wall surface temperature of the present round of iteration.

[0149] As shown in Figure 7 A two-dimensional model is used to verify the UDF program. The inlet velocity is 0.1 m / s, the inlet temperature is 359.31 K, the inlet water vapor mass fraction is 0.479673, and the cold wall surface temperature is 330 K. The upper wall surface is a symmetrical wall surface. Figure 8 To verify the results, it can be seen that the wall condensation flux calculated by the present research almost coincides with the analytical solution in the literature, and the error is less than 20%. Figures 9-12 The temperature distribution cloud map of the two-dimensional model, the water vapor and air mass fraction cloud map, and the velocity distribution cloud map can be seen. 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 application is based on the single-phase multi-component condensation simulation method, opens the component transport equation, uses the user self-development platform UDF (User Defined Function) of the FLUENT software to realize the numerical simulation of condensation, and uses UDM (User Defined Memory) to store the latent heat exchange amount to obtain the condensate retention amount.

[0151] When the model is calculated, the calculation precision 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 there is a mutual dependence relationship among density, energy, momentum and other parameters. The density, momentum, energy term and component term are all discretized by a second-order upwind scheme; the variable gradient difference method selects the Green-Gauss Cell-Based method, which is suitable for quadrilateral and hexahedral grids; selecting a second-order implicit relationship to solve the mixing process of two-component gas can obtain more accurate solutions. The condensation wall surface adopts a no-slip wall boundary condition, and the wall surface temperature distribution is given. During simulation, the wall surface where condensation occurs is set to the wall surface temperature, and the remaining wall surfaces are treated as adiabatic.

[0152] The flow of liquid film on the wall surface is calculated by using the Euler liquid film model. In the model and material settings of the Euler wall film model, the wall film momentum option needs to be activated, and the gravity option and the pressure gradient option in the momentum option need to be opened. On this basis, the extension term and the surface tension term can be opened. The liquid film material selects water as the working medium, and sets its surface tension to 0.07194 N / m. In the time discretization and spatial 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 the second order discretization. The coupled solution of mass and momentum equations is opened, and the bending smoothing is defaulted. Under the default condition, the mass equation of the wall film is calculated first, and then the momentum equation of the wall film is calculated. When the wall film characteristic quantity, i.e. the wall film height and the speed are coupled (such as the free falling wall film of the wave surface), the coupled solution of simultaneously calculating the mass and momentum equations needs to be used. The coupled solution is mainly applied to the occasions of bending wall film and wall film surface tension calculation.

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

[0154] Firstly, a constant condensate generation rate is used as a boundary condition to analyze the liquid film distribution on the wall surface and the retention amount. The calculation conditions of the condensate generation rate are as follows: the pressure in the cavity is 0.3 MPa, the temperature difference is 50℃, and the average condensate generation rate on the 6.5m high vertical plane is about 0.1 kg / (m 2 s) according to the correlation formula.

[0155] The liquid film calculation results are shown in Figures 13-16 , which respectively show the liquid film thickness distribution, the liquid film flow rate distribution, the liquid film mass distribution on the wall surface, and the liquid film thickness distribution of the internal equipment. The liquid film is thicker at the top and the side wall surface near the lower part. The condensate has a low flow rate and a large thickness at the top. The liquid film flows vertically downward along the side wall surface, and the flow rate becomes higher and higher. Due to the truncation of the maintenance platform, the liquid film is thicker above the platform and thinner below the platform.

[0156] The shell wall surface with low steam contact temperature condenses, and the condensate flows down along the wall surface to form a liquid film. From the perspective of reducing the temperature of the containment, the more condensate produced per unit area, the more heat dissipated through the containment, which helps to reduce the temperature and pressure inside the containment. However, the more condensate produced per unit area, the thicker the water film, and the more cooling medium retained in the containment, which reduces the water level of the circulating pump water pool, which 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 peripheral surface, the liquid film thickness 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 application 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 realize the nuclear power plant condensate retention calculation method of any one of the above. Specifically, according to the embodiments of the present application, the processes described above with reference to the flowchart can be implemented as a computer software program. For example, the embodiments of the present application include a computer program product including a computer program carried on a computer readable medium, the computer program including program code for executing the method shown in the flowchart. In such embodiments, the computer program can be downloaded and installed by the electronic device and executed to perform the above-mentioned functions defined in the method of the embodiments of the present application. The electronic device in the present application can be a notebook, desktop, tablet computer, smart phone and other terminals, and can also be a server.

[0158] In addition, the present application also provides a storage medium storing a computer program, which is executed by a processor to implement the nuclear power plant condensate holdup calculation method according to any one of the above. Specifically, it should be noted that the storage medium of the present application can 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, for example, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or apparatus, or any combination of the above. More specific examples of the computer readable storage medium can include, but are not limited to, an electrical connection having one or more wires, a portable computer diskette, 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 application, the computer readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, device or apparatus. In the present application, the computer readable signal medium can include a data signal carried in a baseband or as a part of a carrier wave, which carries computer readable program code. Such a propagated data signal can take various forms, including but not limited to an electromagnetic signal, an optical signal or any suitable combination of the above. The computer readable signal medium can also be any computer readable medium other than the computer readable storage medium, which can send, propagate or transmit a program for use by or in conjunction with an instruction execution system, device or apparatus. The program code contained in the computer readable medium can be transmitted by any suitable medium, including but not limited to a wire, a cable, an RF (radio frequency) or the like, or any suitable combination of the above.

[0159] The above computer readable medium can be contained in the above electronic device; or can exist separately and not be assembled into the electronic device.

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

[0161] Those skilled in the art will further realize that the mere conception of the examples described herein is not inducing any patentable instrument, and that each example presents only one illustrative aspect of the present application. The present application is thus deemed to cover any and all adaptations or variations of preferred examples. It is intended to embrace each and every novel feature and combination of features disclosed herein, singly or in any combination. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

[0162] The steps of a method or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in random access memory (RAM), flash memory, read-only memory (ROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0163] The above examples are merely illustrative of the present application. It is contemplated that other variations of the application will occur to those skilled in the art. Therefore, the present application is not limited to the specific examples described herein, but only by the scope of the appended claims.

Claims

1. A method of calculating a condensate holdup amount in a nuclear power plant, characterized by, The method comprises the following steps: establishing a condensate retention amount analysis geometric model of an object to be analyzed, and performing mesh division on the geometric model to obtain a three-dimensional mesh model; calculating the three-dimensional mesh model by using a single-phase multi-component model to obtain flow field and component distribution of gas-liquid two phases in a phase change process; based on the flow field and component distribution of the gas-liquid two phases in the phase change process, and in combination with a control equation of the object to be analyzed on a condensing wall surface, calculating a condensate generation rate on the condensing wall surface; the calculation based on the flow field and component distribution of the gas-liquid two phases in the phase change process, and in combination with the control equation of the object to be analyzed on the condensing wall surface to obtain the condensate generation rate on the condensing wall surface comprises: based on the flow field and component distribution of the gas-liquid two phases in the phase change process, calculating latent heat released by steam at any time; simulating a mass source term, an energy source term and a momentum source term of mixed gas in the phase change process according to the control equation of the condensing wall surface; calculating component loss of the mixed gas in the phase change process; calculating an updated phase change rate according to the mass source term, the energy source term, the momentum source term and in combination with a wall surface temperature; calculating the condensate generation rate on the wall surface unit at each time according to the updated phase change rate and the latent heat; performing iterative calculation to obtain the condensate generation rate on the condensing wall surface at different times; calculating distribution of the liquid film on the condensing wall surface based on the condensate generation rate; according to the distribution of the condensing wall surface, adjusting calculation conditions to analyze wall surface condensation rules under different steam conditions, and obtaining condensate retention amount data of the condensing wall surface.

2. The nuclear power plant condensate holdup calculation method according to claim 1, characterized by, The establishment of the condensate retention amount analysis geometric model of the object to be analyzed, and the mesh division on the geometric model to obtain the three-dimensional mesh model comprises: establishing a three-dimensional geometric model of the object to be analyzed according to a structure shape and size of the object to be analyzed; simplifying the three-dimensional geometric model according to structure function and working conditions of the object to be analyzed to obtain a simplified three-dimensional model; performing mesh division on the simplified three-dimensional model to obtain an initial mesh model; processing the initial mesh model to obtain the three-dimensional mesh model.

3. The nuclear power plant condensate holdup calculation method according to claim 2, characterized by, 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 mesh model; performing smoothing and optimization processing on the fluid calculation domain mesh; determining an inlet condition, an outlet condition and a wall surface boundary condition of the fluid calculation domain mesh, completing mesh division, and obtaining the three-dimensional mesh model.

4. The nuclear power plant condensate holdup calculation method according to claim 1, characterized by, The calculation of the three-dimensional mesh model by using the single-phase multi-component model to obtain the flow field and component distribution of the gas-liquid two phases in the phase change process comprises: determining a single-phase multi-component fluid in a condensation process; judging whether the fluid reaches an equilibrium state; if yes, completing condensation transition of steam components in the gas phase to the liquid phase through coupling of wall surface source terms; calculating mixed gas parameters of the three-dimensional mesh model based on the single-phase multi-component model; performing iterative calculation to obtain the flow field and component distribution of the gas-liquid two phases in the phase change process.

5. The nuclear power plant condensate holdup calculation method according to Claim 1, characterized by, The mass source term, energy source term, and momentum source term of the mixed gas during the phase change process, simulated according to the governing equation of the condensation wall, include: Based on the governing equations of the condensation wall, the following calculations are performed: The mass source term is obtained by calculating the mass transfer from the gas phase vapor component to the liquid phase water component based on the initial phase change rate. The heat transferred from the gas phase to the liquid phase is calculated based on 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 gas and liquid based on the viscous stress and pressure on the wall.

6. The nuclear power plant condensate holdup calculation method according to Claim 1, characterized by, The calculation of component losses in the mixed gas during the phase transition 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 vapor components; the change in the component fraction of the mixed gas is the combined loss of the mixed gas.

7. The nuclear power plant condensate holdup calculation method according to Claim 1, characterized by, The step of calculating the updated phase transition rate based on the mass source term, the energy source term, the momentum source term, and in conjunction with the wall temperature includes: The equilibrium pressure of the vapor during phase change is calculated based on the mass source term, the energy source term, the momentum source term, and the temperature of the mixed gas. The saturated vapor pressure at the gas-liquid interface is calculated based on the equilibrium pressure of the vapor during the phase change and the wall temperature, and the updated phase change rate is obtained.

8. The nuclear power plant condensate holdup calculation method according to Claim 1, characterized by, The calculation of the liquid film distribution on the condenser wall based on the condensate generation rate includes: Based on the condensate generation rate, the distribution of the liquid film on the condensation wall is calculated using a liquid film model.

9. The nuclear power plant condensate holdup calculation method according to claim 8, characterized by, The calculation of the distribution of the liquid film on the condenser wall surface using a liquid film model based on the condensate generation rate includes: Create a liquid film subgrid in the first computational cell of the wall; The condensate generation rate is determined as the inlet velocity boundary condition of the liquid film subgrid; Within 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 transition rate is calculated based on the interfacial energy balance between the liquid film and the gas phase. The average velocity of the liquid film is obtained and the average velocity of the liquid film is determined as the exit velocity boundary condition of the liquid film subgrid; Calculate single-phase flow in an external flow field; Based on the liquid film velocity, thickness, and temperature distribution, iterative calculations of the internal and external flow fields of the single-phase flow are performed to obtain the coupled solution of the liquid film and gas phase flow; the coupled solution of the liquid film and gas phase flow is the distribution of the liquid film on the condensation wall.

10. The nuclear power plant condensate holdup calculation method according to Claim 1, characterized by, The step of analyzing the wall condensation patterns under different steam conditions based on the distribution of the condensation wall surface, by adjusting the calculation conditions, and obtaining the condensate retention data of the condensation wall surface includes: Determine the parameters that affect condensation; By setting different values ​​for the parameters that affect condensation, multiple sets of calculation conditions are obtained; Numerical simulations of condensate retention were performed for each set of calculation conditions based on the distribution of the condensation wall surface. The variation law of condensation on the wall surface under different conditions was analyzed to obtain the condensate retention data of the condensation wall surface.

11. A nuclear power plant condensate holdup amount calculation device characterized by comprising: include: The model building unit is used to establish a geometric model for analyzing the condensate retention of the object to be analyzed, and to mesh the geometric model to obtain a three-dimensional mesh model. A phase change computing unit is configured to calculate the three-dimensional grid model by using a single-phase multi-component model to obtain a flow field and a component distribution of gas-liquid two-phase in a phase change process; A condensate production rate calculating unit is configured to calculate the condensate production rate on the condensing wall surface based on the flow field and the component distribution of the gas-liquid two-phase in the phase change process and a control equation of the object to be analyzed on the condensing wall surface. The calculation based on the flow field and the 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 condensing wall surface to obtain the condensate production rate on the condensing wall surface includes: calculating the latent heat released by steam at any time based on the flow field and the component distribution of the gas-liquid two-phase in the phase change process; simulating a mass source term, an energy source term and a momentum source term of mixed gas in the phase change process according to the control equation of the condensing wall surface; calculating the component loss of the mixed gas in the phase change process; calculating an updated phase change rate according to the mass source term, the energy source term, the momentum source term and the wall surface temperature; calculating the condensate production rate on the wall surface unit at each time according to the updated phase change rate and the latent heat; and performing iterative calculation to obtain the condensate production rate on the condensing wall surface at different times. A liquid film distribution calculating unit is configured to calculate the distribution of the liquid film on the condensing wall surface based on the condensate production rate. A condensate holdup calculating unit is configured to analyze the wall surface condensation law under different steam conditions by adjusting the calculation conditions according to the distribution of the condensing wall surface to obtain the condensate holdup data of the condensing wall surface.

12. A storage medium, characterized by The storage medium stores a computer program, and the computer program is suitable for being loaded by the processor to execute the steps of the nuclear power plant condensate holdup calculation method according to any one of claims 1 to 10.

13. An electronic device, comprising: The memory stores a computer program, and the processor executes the steps of the nuclear power plant condensate holdup calculation method according to any one of claims 1 to 10 by calling the computer program stored in the memory.

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