CN-118297001-B - Simulation method and device for phase-change water hammer in pipeline of nuclear power plant

CN118297001BCN 118297001 BCN118297001 BCN 118297001BCN-118297001-B

Abstract

The invention discloses a simulation method and a device of a phase-change water hammer in a pipeline of a nuclear power plant, wherein the method comprises the following steps of firstly, establishing a calculation domain model of a pipeline of the nuclear power plant; the method comprises the steps of carrying out grid division on a calculation domain model to generate grids, setting boundary conditions according to water hammer phenomena, wherein the boundary conditions comprise an inlet boundary condition, an outlet boundary condition and a wall boundary condition, establishing a Lee-HTC mixed model, and finally simulating the phase change water hammer phenomena by using an SST k-omega turbulence model, a VOF multiphase flow model and the established Lee-HTC mixed model based on the grids and the boundary conditions to obtain a simulation result. The invention combines the advantages of the Lee model and the HTC model, simultaneously considers the heat and mass transfer at the two-phase interface and the phase change in the liquid, can expand the application range of the traditional condensation model, and realizes the accurate simulation and analysis of the water hammer effect in the complex phase change process of flash evaporation and condensation.

Inventors

ZHAO JIAMING
WU YONGZHONG
XIONG FENG
ZHANG ZIHAO
CHEN ZHENGYU
GUO WENTAO
WANG SHENGFEI
Tu Ruiyang
ZHAO BIN
ZHANG ZEHAO
SHEN JIANNAN
YU PEI
LIN DAPING
CHEN XIAOXIA
LI JIE

Assignees

中国核电工程有限公司

Dates

Publication Date: 20260505
Application Date: 20240429

Claims (16)

1. The simulation method of the phase-change water hammer in the pipeline of the nuclear power plant is characterized by comprising the following steps of: establishing a calculation domain model of a nuclear power plant pipeline; Performing grid division on the calculation domain model to generate grids; Setting boundary conditions according to the water hammer phenomenon, wherein the boundary conditions comprise an inlet boundary condition, an outlet boundary condition and a wall boundary condition; the method for building the Lee-HTC hybrid model comprises building the Lee-HTC hybrid model by utilizing a first integral equation, a mass conservation equation, a momentum conservation equation and an energy conservation equation, , Wherein, the As the volume fraction of the vapor, Is the liquid volume fraction, the mass conservation equation, , , Wherein, the In order to achieve a vapor density, As a velocity vector of the velocity vector, As a source item of quality, In order to achieve a liquid density, In order to be able to take time, Indicating the divergence of the mass flux of the steam, Representing the divergence of the liquid mass flux, the conservation of momentum equation, , Wherein, the For the density of the fluid at the grid, Is a negative gradient pressure, and the pressure is a negative gradient pressure, Is the dynamic viscosity of the fluid, and is defined as the dynamic viscosity of the fluid, Representing the transpose operator, The force of gravity is applied to the acceleration vector, For the force acting on the object per unit volume, the energy conservation equation, , Wherein, the In order to be able to determine the temperature, In order to provide a temperature gradient, Representation of Is used for the dispersion of (a), For the thermal conductivity of the material, Is the specific heat capacity of the material, Is an energy source item; Based on the grid and the boundary condition, simulating a phase change water hammer phenomenon by using an SST k-omega turbulence model, a VOF multiphase flow model and the established Lee-HTC mixed model to obtain a simulation result, wherein the simulation result comprises the steps of determining turbulence kinetic energy and specific dissipation rate according to the SST k-omega turbulence model, determining an energy source item of the Lee-HTC mixed model based on the turbulence kinetic energy and the specific dissipation rate, determining dissipation rate based on the turbulence kinetic energy and the specific dissipation rate by using a formula I, , wherein, In order for the dissipation ratio to be high, Is a constant coefficient of the number of the pieces of the material, As a kinetic energy of the turbulent flow, Determining a heat transfer coefficient HTC in the Lee-HTC hybrid model according to the turbulent kinetic energy and the dissipation ratio by a formula II, , Wherein, the In order to adjust the factor(s), Is the coefficient of thermal conductivity of the liquid, Is the specific heat capacity of the liquid, In order to achieve a liquid density, In order for the dissipation ratio to be high, Is the kinematic viscosity of the liquid and, Determining the energy source term of the Lee-HTC hybrid model according to the heat transfer coefficient HTC through a formula III, , Wherein, the As an energy source item, a device for generating energy, In order to achieve a relaxation time, the time of the relaxation, In order to achieve a liquid density, Is the temperature of the liquid, and is the temperature of the liquid, Is at the saturation temperature of the glass fiber, Is the latent heat of phase change, HTC is the heat transfer coefficient, Is the interface density.
2. The method of claim 1, further comprising evaluating the Lee-HTC hybrid model based on the simulation results.
3. The method of claim 1, wherein meshing the computational domain model to generate a mesh comprises: Simulating by adopting a plurality of groups of initial grids with different sizes, acquiring the temperature and the vapor-liquid mass transfer rate of a flow field corresponding to the initial grids with different sizes, and verifying the grid independence; And determining the size of the grid according to the grid independence verification result, and carrying out grid division on the calculation domain model by utilizing the size.
4. The method of claim 1, wherein simulating phase-change water hammer using SST k- ω turbulence model, VOF multiphase flow model and Lee-HTC hybrid model based on the grid, the boundary conditions, further comprises: Determining a quality source item of the Lee-HTC hybrid model according to the energy source item; Determining a liquid volume fraction using the VOF multiphase flow model; And solving according to the liquid volume fraction, the energy source term and the mass source term by combining the first integral equation, the mass conservation equation, the momentum conservation equation and the energy conservation equation to obtain a simulation result, wherein the simulation result comprises a steam volume fraction, a temperature, a pressure and a speed.
5. The method of claim 4, wherein determining turbulent kinetic energy and specific dissipation ratio from the SST k- ω turbulence model comprises: determining turbulent kinetic energy and specific dissipation ratio from a turbulent kinetic energy equation and specific dissipation ratio equation in the SST k- ω turbulent model, the turbulent kinetic energy equation, , Wherein, the As a kinetic energy of the turbulent flow, For the density of the fluid at the grid, Is the first of the velocity vectors The number of components of the composition, The orientation coordinates are represented as such, Representing the generation term of turbulent kinetic energy, As the coefficient of the light-emitting diode, In order to achieve the specific consumption rate of the powder, Is the dynamic viscosity of the fluid, and is defined as the dynamic viscosity of the fluid, Is turbulent dynamic viscosity; the specific dissipation ratio equation is described as, , Wherein, the In order to be able to compare the dissipation ratio, In order to achieve a turbulent kinematic viscosity, As a function of the mixing function, 、 As the coefficient of the light-emitting diode, Is the dynamic viscosity of the fluid, and is defined as the dynamic viscosity of the fluid, Is turbulent dynamic viscosity.
6. The method of claim 4, wherein determining a quality source term for the Lee-HTC hybrid model from the energy source term comprises: determining a quality source term of the Lee-HTC hybrid model according to the energy source term through a formula IV, , wherein, Is a quality source item.
7. The method of claim 4, wherein determining a liquid volume fraction using the VOF multiphase flow model comprises: determining a liquid volume fraction from a second volume fraction equation in the VOF multiphase flow model, the second volume fraction equation, , wherein, Representing the gradient of the liquid volume fraction.
8. The method of claim 2, wherein evaluating the Lee-HTC hybrid model based on the simulation results comprises: Generating a steam volume fraction cloud chart, a temperature cloud chart, a pressure change curve, a mass transfer rate curve and a vapor-liquid mass transfer rate curve according to the simulation result; and evaluating the Lee-HTC mixing model by combining the vapor volume fraction cloud chart, the temperature cloud chart, the pressure change curve, the mass transfer rate curve and the vapor-liquid mass transfer rate curve.
9. The utility model provides a nuclear power plant in-line phase transition water hammer's analogue means which characterized in that includes: The first building module is used for building a calculation domain model of the nuclear power plant pipeline; the dividing module is used for dividing grids of the calculation domain model to generate grids; the setting module is used for setting boundary conditions according to the water hammer phenomenon, wherein the boundary conditions comprise an inlet boundary condition, an outlet boundary condition and a wall boundary condition; A second building module for building a Lee-HTC hybrid model, comprising building the Lee-HTC hybrid model using a first integral equation, a conservation of mass equation, a conservation of momentum equation, and a conservation of energy equation, , Wherein, the As the volume fraction of the vapor, Is the liquid volume fraction, the mass conservation equation, , , Wherein, the In order to achieve a vapor density, As a velocity vector of the velocity vector, As a source item of quality, In order to achieve a liquid density, In order to be able to take time, Indicating the divergence of the mass flux of the steam, Representing the divergence of the liquid mass flux, the conservation of momentum equation, , Wherein, the For the density of the fluid at the grid, Is a negative gradient pressure, and the pressure is a negative gradient pressure, Is the dynamic viscosity of the fluid, and is defined as the dynamic viscosity of the fluid, Representing the transpose operator, The force of gravity is applied to the acceleration vector, For the force acting on the object per unit volume, the energy conservation equation, , Wherein, the In order to be able to determine the temperature, In order to provide a temperature gradient, Representation of Is used for the dispersion of (a), For the thermal conductivity of the material, Is the specific heat capacity of the material, Is an energy source item; the simulation module is used for simulating a phase change water hammer phenomenon by using an SST k-omega turbulence model, a VOF multiphase flow model and the established Lee-HTC mixed model based on the grid and the boundary condition to obtain a simulation result, and comprises the steps of determining turbulence kinetic energy and specific dissipation rate according to the SST k-omega turbulence model, determining an energy source item of the Lee-HTC mixed model based on the turbulence kinetic energy and the specific dissipation rate, determining dissipation rate according to a formula I based on the turbulence kinetic energy and the specific dissipation rate, , wherein, In order for the dissipation ratio to be high, Is a constant coefficient of the number of the pieces of the material, As a kinetic energy of the turbulent flow, Determining a heat transfer coefficient HTC in the Lee-HTC hybrid model according to the turbulent kinetic energy and the dissipation ratio by a formula II, , Wherein, the In order to adjust the factor(s), Is the coefficient of thermal conductivity of the liquid, Is the specific heat capacity of the liquid, In order to achieve a liquid density, In order for the dissipation ratio to be high, Is the kinematic viscosity of the liquid and, Determining the energy source term of the Lee-HTC hybrid model according to the heat transfer coefficient HTC through a formula III, , Wherein, the As an energy source item, a device for generating energy, In order to achieve a relaxation time, the time of the relaxation, In order to achieve a liquid density, Is the temperature of the liquid, and is the temperature of the liquid, Is at the saturation temperature of the glass fiber, Is the latent heat of phase change, HTC is the heat transfer coefficient, Is the interface density.
10. The apparatus of claim 9, further comprising an evaluation module configured to evaluate the Lee-HTC hybrid model based on the simulation results.
11. The apparatus of claim 10, wherein the partitioning module is configured to: Simulating by adopting a plurality of groups of initial grids with different sizes, acquiring the temperature and the vapor-liquid mass transfer rate of a flow field corresponding to the initial grids with different sizes, and verifying the grid independence; And determining the size of the grid according to the grid independence verification result, and carrying out grid division on the calculation domain model by utilizing the size.
12. The apparatus of claim 11, wherein the simulation module is further configured to: Determining a quality source item of the Lee-HTC hybrid model according to the energy source item; Determining a liquid volume fraction using the VOF multiphase flow model; And solving according to the liquid volume fraction, the energy source term and the mass source term by combining the first integral equation, the mass conservation equation, the momentum conservation equation and the energy conservation equation to obtain a simulation result, wherein the simulation result comprises a steam volume fraction, a temperature, a pressure and a speed.
13. The apparatus of claim 12, wherein determining turbulent kinetic energy and specific dissipation ratio from the SST k- ω turbulence model comprises: determining turbulent kinetic energy and specific dissipation ratio from a turbulent kinetic energy equation and specific dissipation ratio equation in the SST k- ω turbulent model, the turbulent kinetic energy equation, , Wherein, the As a kinetic energy of the turbulent flow, For the density of the fluid at the grid, Is the first of the velocity vectors The number of components of the composition, The orientation coordinates are represented as such, Representing the generation term of turbulent kinetic energy, As the coefficient of the light-emitting diode, In order to achieve the specific consumption rate of the powder, Is the dynamic viscosity of the fluid, and is defined as the dynamic viscosity of the fluid, Is turbulent dynamic viscosity; the specific dissipation ratio equation is described as, , Wherein, the In order to be able to compare the dissipation ratio, In order to achieve a turbulent kinematic viscosity, As a function of the mixing function, 、 As the coefficient of the light-emitting diode, Is the dynamic viscosity of the fluid, and is defined as the dynamic viscosity of the fluid, Is turbulent dynamic viscosity.
14. The apparatus of claim 13, wherein determining a quality source term for the Lee-HTC hybrid model from the energy source term comprises: determining a quality source term of the Lee-HTC hybrid model according to the energy source term through a formula IV, , wherein, Is a quality source item.
15. The apparatus of claim 13, wherein determining a liquid volume fraction using the VOF multiphase flow model comprises: determining a liquid volume fraction from a second volume fraction equation in the VOF multiphase flow model, the second volume fraction equation, , wherein, Indicating the dispersion of the liquid volume fraction.
16. The apparatus of claim 10, wherein the evaluation module is configured to: Generating a steam volume fraction cloud chart, a temperature cloud chart, a pressure change curve, a mass transfer rate curve and a vapor-liquid mass transfer rate curve according to the simulation result; and evaluating the Lee-HTC mixing model by combining the vapor volume fraction cloud chart, the temperature cloud chart, the pressure change curve, the mass transfer rate curve and the vapor-liquid mass transfer rate curve.

Description

Simulation method and device for phase-change water hammer in pipeline of nuclear power plant Technical Field The invention relates to the technical field of multiphase flow simulation, in particular to a simulation method and device of a phase change water hammer in a pipeline of a nuclear power plant. Background The water hammer phenomenon is an unsteady flow phenomenon occurring in the flow of liquid. When the liquid suddenly stops or changes speed in the pipe, the pressure in the pipe changes drastically, which results in a shock wave, the effect of which is the so-called water hammer effect. The water hammer effect may occur in many facilities in daily life, such as a home water supply system, a steam pipe of a thermal power plant, and the like. Particularly in large industrial pipeline systems, the more damaging the effects of water hammer effects may be due to the high fluid flow rates and large flows. According to different water hammer initiation mechanisms, the water hammer caused by sudden stop of single-phase flowing fluid and the water hammer caused by condensation phase change can be divided into two types. The single-phase water hammer mostly occurs in a pipeline system of a water supply plant, and the condensed water hammer refers to the phenomenon of instant pressure pulsation and impact force generated by interaction of steam and condensed water in the pipeline system, and is commonly found in a hot gas defrosting process in the refrigeration industry and a pressurized water reactor water supply pipe and an evaporator of a nuclear power station. Condensation water hammer is a common and dangerous form of water hammer, which not only causes damage to pipes and equipment, but also threatens personnel safety. The occurrence mechanism of the condensation water hammer is complex, and a plurality of physical processes such as multiphase flow, phase change, heat transfer, mass transfer and the like are involved, so that modeling and solving are not easy, and accurate prediction and control of the condensation water hammer are challenging. At present, computational Fluid Dynamics (CFD) technology has become one of effective methods for analyzing and predicting a condensation water hammer, but a traditional condensation model such as a Lee model has an unsatisfactory simulation effect on a condensation phenomenon, and an HTC model based on a surface update theory only considers a heat and mass transfer process at a phase change interface, so that a flash evaporation process inside liquid is difficult to describe, and a water hammer effect when an air pocket collapses is difficult to simulate. The prior patent CN111695242A discloses a numerical simulation method for condensing wet saturated flue gas steam, which simplifies the condensing process of the wet saturated flue gas into a steam condensing process containing a large amount of non-condensable gas, carries out geometric modeling and grid division on a heat exchange flow field, carries out numerical calculation by adopting a phase change coefficient model and a multiphase flow model, sets the non-condensable flue gas as a main phase, adds mass and energy source items to a control equation by introducing a self-organized UDF program, realizes mass and energy transfer generated by phase change between phases, simulates the condensing process of the steam in the wet saturated flue gas, and analyzes the distribution condition of flue gas speed and mass fraction under the condition of turbulence. The method is used for realizing faster and effective numerical prediction of the steam condensation heat exchange process in the wet saturated flue gas, and is not suitable for solving the problem of water hammer effect in the complex phase change process including flash evaporation and cavitation collapse. The prior document 2 discloses numerical simulation of steam condensation and flow in a horizontal tube, which is performed on the steam condensation and flow process in 100mm of the inlet section of a heat exchange tube of a horizontal tube falling film evaporator in a seawater desalination device. The method comprises the steps of tracking a phase interface by adopting a VOF method, respectively processing a condensation source item and surface tension by using a Lee model and a CSF model, analyzing the influence rules of heat transfer temperature difference of pipe wall and steam and inlet steam mass flow rate on heat flow density and average heat exchange coefficient of the pipe, observing two-phase distribution in the pipe, observing that no complete liquid film is formed around the pipe wall, enabling the steam to directly contact with the wall surface for condensation and heat release, enabling the thickness of a temperature boundary layer at the pipe wall to be 20-30 mu m, and analyzing the axial speed and radial speed distribution rules of the steam under different heat transfer temperature differences. In summary, the above-mentioned prior ar