CN112001068A - Arrangement method of electric heating elements of nuclear power station voltage stabilizer based on three-dimensional transient heat transfer mechanism - Google Patents

Arrangement method of electric heating elements of nuclear power station voltage stabilizer based on three-dimensional transient heat transfer mechanism Download PDF

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CN112001068A
CN112001068A CN202010793828.2A CN202010793828A CN112001068A CN 112001068 A CN112001068 A CN 112001068A CN 202010793828 A CN202010793828 A CN 202010793828A CN 112001068 A CN112001068 A CN 112001068A
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voltage stabilizer
temperature
speed
dimensionless
fluctuation
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张继国
陈勇
郝达荣
殷智峰
宋长远
陈大玮
唐旭
张煜坤
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Shanghai Jiaotong University
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Abstract

A method for arranging electric heating elements of a nuclear power station voltage stabilizer based on a three-dimensional transient heat transfer mechanism comprises the steps of firstly carrying out reasonable three-dimensional modeling and grid division on the voltage stabilizer, then based on a CFD method, an RKE model is combined with a VOF multiphase flow heat transfer model to carry out numerical simulation on the mixing phenomenon of cold and hot fluid in the voltage stabilizer during positive fluctuation, and finally, the time-mean dimensionless and root-mean-square dimensionless processing is carried out on the numerical simulation result to represent the average value and the fluctuation condition of the speed and the temperature during the mixing process, the invention analyzes the flow characteristic and the heat transfer characteristic of the coolant in the wave-in process of the voltage stabilizer from the angle of numerical simulation to obtain the accurate range of the reasonable arrangement of the electric heating elements in the lower end socket of the voltage stabilizer, thereby providing reference for the arrangement optimization of the electric heating elements in the actual engineering.

Description

Arrangement method of electric heating elements of nuclear power station voltage stabilizer based on three-dimensional transient heat transfer mechanism
Technical Field
The invention relates to a technology in the field of intelligent control of a nuclear power station, in particular to a method for arranging electric heating elements of a voltage stabilizer of the nuclear power station based on a three-dimensional transient heat transfer mechanism.
Background
The voltage stabilizer is a main device of a pressure safety system of a pressurized water reactor nuclear power station, the electric heater is a core element of the voltage stabilizer device, and in the operation process, because the electric heating element is directly soaked in water and heat is directly exchanged, the pressure stabilizer can bear the rigor tests of ultrahigh water pressure, instantaneous extreme temperature difference change, high radioactive dose, long-term stable operation and the like. Should an electric heater fail, it would affect the power plant's ability to maintain and control the operating pressure of the reactor coolant system, even leading to a primary overpressure shutdown. At present, the electric heating element of a pressurized water reactor voltage stabilizer of a third-generation nuclear power station has no mature operation performance, a typical third-generation nuclear power unit AP1000 is taken as an example, by comparing technical parameters of a second-generation heater, the power deviation of the AP1000 electric heater is about 5 times that of the second-generation heater, the actual power load is more difficult to control, the deviation can strengthen the cold and hot alternating stress of an electric heater cladding during operation, the electric heater cladding is easier to expand and break, so that a sleeve pipe is deformed mechanically, the probability of reactor coolant leakage caused by breakage of a lower end socket is increased, and in recent years, more and more students pay attention to failure cases of the electric heater which are continuously generated by domestic and foreign nuclear power stations. Therefore, on the basis of ensuring the quality of the electric heater element, direct impact of the incoming and outgoing cold and hot fluids on the electric heating rod is avoided as much as possible, the influence of speed and temperature oscillation generated in the mixing process of the cold and hot fluids on the electric heater is reduced, and repeated vibration, thermal fatigue failure and penetrating cracks generated on the surfaces of the electric heater cladding and the sleeve are prevented from damaging welding seams between the electric heater and the sleeve, and between the electric heater sleeve and the lower end socket of the voltage stabilizer.
The research on voltage regulators at home and abroad still stays in the dynamic characteristic research on the voltage regulators of the nuclear power station by establishing a mathematical model, and mainly comprises a two-phase equilibrium model, a two-phase non-equilibrium model, a three-zone non-equilibrium model and a multi-zone non-equilibrium model. However, the method of the mathematical model cannot embody the flow field distribution and the thermal hydraulic characteristics in the voltage stabilizer, and lacks guidance for the arrangement of the electric heating element in the voltage stabilizer. Considering that the third generation voltage stabilizer is greatly changed compared with the second generation voltage stabilizer, if the electric heating elements arranged in the voltage stabilizer are inevitably insufficient according to the past empirical value, the CFD simulation technology is introduced into the dynamic process analysis of the voltage stabilizer, and the optimal range suitable for the arrangement of the electric heating elements is searched from the fluctuation mechanism of the cold and hot fluid mixing process in the voltage stabilizer, so that the CFD simulation technology has important significance for understanding the flow heat transfer process in the voltage stabilizer, optimizing the design and safely operating the third generation nuclear power generating unit.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for arranging electric heating elements of a nuclear power station voltage stabilizer based on a three-dimensional transient heat transfer mechanism, which analyzes the flow characteristic and the heat transfer characteristic of a coolant in the wave-in process of the voltage stabilizer from the angle of numerical simulation to obtain the accurate range of reasonable arrangement of the electric heating elements in a lower end socket of the voltage stabilizer, and provides reference for the arrangement optimization of the electric heating elements in the actual engineering.
The invention is realized by the following technical scheme:
the invention relates to a nuclear power station voltage stabilizer electric heating element arrangement method based on a three-dimensional transient heat transfer mechanism, which comprises the steps of carrying out reasonable three-dimensional modeling on a voltage stabilizer and carrying out grid division, then carrying out numerical simulation on the mixing phenomenon of cold and hot fluid in the voltage stabilizer during positive fluctuation by using an RKE (k-turbulence) model and a VOF (fluid volume method) multiphase flow heat transfer model based on a CFD (computational fluid dynamics) method, finally carrying out time-mean dimensionless and root-mean-square dimensionless processing on the numerical simulation result to represent the average value and the fluctuation condition of speed and temperature in the mixing process, obtaining the accurate range of reasonable arrangement of electric heating elements in a lower end socket of the voltage stabilizer by analyzing the fluctuation intensity of the speed and the temperature, and providing reasonable and reliable theoretical guidance for engineering practice.
The three-dimensional modeling means that: a simplified three-dimensional full-size geometric model of a cavity of a voltage stabilizer of a nuclear power station is established, the condition of mixed fluctuation of cold and hot fluid in the voltage stabilizer is analyzed from a source, structures such as an electric heater rod, a supporting plate, a guide plate, a screen, a fluctuation pipe and a connecting pipe of the voltage stabilizer in the voltage stabilizer are ignored, a lower end socket of the voltage stabilizer is processed into the cavity, transient flow of a gas-liquid two-phase interface in the voltage stabilizer is described by an RANS equation based on a VOF multiphase flow model, the whole solving system is closed by a coupling RKE turbulence model, a coordinate system is established by the model by taking the circle center of the middle section of a cylinder of the.
Preferably, the three-dimensional modeling adopts a grid division mode of full hexahedron structuring and blocking.
In the mixing phenomenon of the cold and hot fluid in the voltage stabilizer, the density of the cold and hot fluid estimates the influence of a buoyancy term through a polynomial function of temperature, and the method specifically comprises the following steps: p 737.9063+1.81776T-0.00322T2Wherein: rho is the density of the water body, T is the temperature of the water body, and the compressibility of the water vapor is described by adopting an ideal gas law.
Preferably, the three-dimensional modeling is to reduce the computation time and simplify the model, and consider the heat convection and the heat conduction while neglecting the heat conduction effect of the fluid and the pipe wall and the inner direction of the pipe wall, wherein: the energy equation for considering thermal convection and conduction is:
Figure BDA0002624781680000021
wherein: subscript k is a gas or liquid, subscript i is a non-k phase, αk，ρk，
Figure BDA0002624781680000022
HkVolume fraction, density, velocity, enthalpy of each phase,
Figure BDA0002624781680000023
for mass transfer from the k-phase to the i-phase, the first term on the right is the pressure induced enthalpy change, the second term is the combination of molecular and turbulent heat fluxes, and the third term is the change in enthalpy due to diffusion mass flux (evaporation and condensation).
The mesh division is preferably performed by using CFD preprocessing software, and in order to better simulate the area where the flow velocity gradient and the heat transfer temperature gradient are changed violently, the mesh at the joint of the lower end socket and the wave tube is subjected to secondary segmentation and topological operation, so that the mesh in the area is encrypted.
The numerical simulation is to establish a three-dimensional transient heat transfer mathematical model of mixed flow of cold and hot fluids in the cavity of the voltage stabilizer, determine an initial working condition and a boundary condition according to thermal state function test data of the nuclear power station, then solve a flow heat transfer control equation, and monitor the temperature and speed change of a monitoring point in the cold and hot fluid mixing process.
The initial working condition and the boundary condition comprise: setting a wall thermal boundary as a heat insulation boundary, and keeping the wall thermal boundary static, smooth and non-slip; setting the corresponding calculation domains of the water phase and the vapor phase and the initial pressure.
The change monitoring means that: the steam-water liquid level reconstruction adopts a Modified HRIC format, and adopts time-mean dimensionless values to describe the average value of the temperature in the mixing process, wherein the time-mean dimensionless temperature is as follows:
Figure BDA0002624781680000031
wherein:
Figure BDA0002624781680000032
is dimensionless temperature, ThotIs hot fluid, TcoldIs cold fluid, N is the total number collected in the calculation time, i is variable, Ti *Dimensionless temperature, T, for collection pointiThe temperature of the mixed water body at the collection point.
The average value and fluctuation condition of the speed and the temperature in the mixing process refer to that: the characterization method for determining the thermal fluctuation and the speed fluctuation intensity of the cold and hot fluid mixing dynamic process in the voltage stabilizer obtains the distribution and the change rule of an instantaneous speed field, a pressure field and temperature by using CFD post-processing software, and specifically comprises the following steps: describing the fluctuation intensity of the temperature in the mixing process by adopting a root-mean-square dimensionless value, wherein the root-mean-square dimensionless temperature is as follows:
Figure BDA0002624781680000033
wherein: n is the total number collected in the calculation time, i is variable, Ti *Is a non-dimensional temperature of the collection point,
Figure BDA0002624781680000034
the non-dimensional temperature is the acquisition point;
secondly, describing the average value of the speed in the mixing process by adopting the time-mean dimensionless value, wherein the time-mean dimensionless speed is as follows:
Figure BDA0002624781680000035
wherein: vmIndicating the speed of wave-in, ViFor the non-dimensional speed of the acquisition point,
Figure BDA0002624781680000036
the non-dimensional speed is obtained at the acquisition point; thirdly, the fluctuation intensity of the speed in the mixing process is described by adopting a root-mean-square dimensionless value, and the root-mean-square dimensionless speed is as follows:
Figure BDA0002624781680000037
technical effects
The invention integrally solves the technical problem of providing theoretical guidance for the arrangement range of the electric heating element in the voltage stabilizer of the pressurized water reactor nuclear power station so as to relieve the severe working environment of the electric heating element;
compared with the prior art, the method can effectively predict the development trend of the wave-in process of the voltage stabilizer, can capture the temperature and speed fluctuation intensity of cold and hot fluid mixing in the wave-in process, finds out the area with larger fluctuation intensity, and avoids the electric heating element from being arranged in the area as much as possible when the electric heating element is arranged, thereby improving the severe working environment of the electric heating element.
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FIG. 1 is a schematic diagram of a test section of an experimental setup according to an embodiment of the present invention;
FIG. 2 is a flow chart of a method for arranging electric heating elements of a voltage stabilizer of a nuclear power plant based on a three-dimensional transient heat transfer mechanism;
FIG. 3 is a three-dimensional geometric model of an embodiment of the present invention;
in the figure: l is1＝12.63，L2＝0.8，DM＝2.54，DR＝0.366；
FIG. 4 is a diagram of a computational area grid division in accordance with an embodiment of the present invention;
FIG. 5 is a graph comparing experimental and simulated RMS dimensionless speed values in accordance with an embodiment of the invention;
FIG. 6 is a graph comparing experimental and simulated RMS dimensionless temperature values in accordance with an embodiment of the invention;
FIG. 7 is a flow field distribution diagram of the transient velocity at the central cross section of the lower head region of the voltage stabilizer according to the embodiment of the present invention;
in the figure: (a) t is 0.75s, (b) t is 1s, (c) t is 1.5s, (d) t is 2.5s, (e) t is 3.5s, (f) t is 4.5 s;
fig. 8 is a y-direction root mean square dimensionless speed distribution curve of different position points on the central cross section of the lower head region of the voltage stabilizer in the embodiment of the present invention;
fig. 9 is a y-direction root mean square dimensionless temperature distribution curve of different position points on the central cross section of the lower head region of the voltage stabilizer according to the embodiment of the present invention.
Detailed Description
In order to verify and analyze the simulation effect of the arrangement method of the electric heating elements of the nuclear power station voltage stabilizer based on the three-dimensional transient heat transfer mechanism, a built voltage stabilizer fluctuation research experiment device system is selected for verifying the effectiveness of the method, and a part of experiment devices are simply tested, as shown in fig. 1. The experimental condition comes from the nuclear power station thermal state function test data, namely when ripples, the vertical surge pipe and stabiliser barrel are being filled with hot-fluid in 50% space, and another 50% is the steam space, and liquid phase and vapour phase are in saturation equilibrium state, and the temperature of steam and coolant equals the saturation temperature of rated operating pressure (corresponding to 15.5Mpa for 617.95K), and in a certain moment suddenly, 595K low-temperature water from the surge pipe gushes into the stabiliser from the vertical straight tube section of surge pipe with 5.5 m/s's speed.
As shown in fig. 2, the method for arranging the electric heating elements of the nuclear power plant voltage stabilizer based on the three-dimensional transient heat transfer mechanism includes the following specific steps:
step 1, establishing a reasonably simplified three-dimensional full-size geometric model of a nuclear power station voltage stabilizer cavity according to engineering practice, and carrying out mesh division by using CFD pretreatment software: according to experimental working conditions, an ANSYS software SpaceClaim module creates a three-dimensional full-size geometric model of a cavity of the voltage stabilizer, the model establishes a coordinate system by taking the circle center of the section in the middle of the cylinder of the voltage stabilizer as an origin of coordinates, and the fluid direction of a fluctuation pipe is the positive y direction, as shown in FIG. 3; and importing the model into an ANSYS software ICEM module, defining each boundary surface, and performing secondary segmentation and topological operation on the grid at the joint of the lower end socket and the wave pipe by the model in a full hexahedron structured and blocked grid division mode so as to encrypt the grid in the region, as shown in FIG. 4.
Step 2, constructing a three-dimensional transient heat transfer mathematical model of mixed flow of cold and hot fluids in the cavity of the voltage stabilizer: the density of cold and hot fluid is processed into a polynomial function of temperature to estimate the influence of buoyancy term, and the density rho of the water body is 737.9063+1.81776T-0.00322T2And in the wave-in process, the density of the cold and hot fluid can be updated in real time according to the calculated temperature.
Step 3, determining an initial working condition and a boundary condition according to the thermal state function test data of the nuclear power station: the wall thermal boundary is set as an adiabatic boundary, and is static, smooth and free of slippage; the calculated domain and initial pressure (15.5Mpa) for the aqueous phase, vapor phase are set. The physical properties of the flowing medium are shown in table 1.
TABLE 1 physical Properties of Coolant, saturated steam
Parameter(s) Value of
Initial water temperature of the pressure stabilizer, K 617.95
Water temperature, K 595
Wave entry velocity, m/s 5.5
Density of coolant, kg/m3 737.9063+1.81776T-0.00322T2
Constant pressure specific heat capacity of coolant, J/kg.K 5458.3
Dynamic viscosity of coolant, kg/m.s 5.122×10-5
Saturated steam density, kg/m3 100.86
Saturated steam constant pressure specific heat capacity, J/kg.K 13803.5
Saturated steam dynamic viscosity, kg/m.s 2.55×10-5
Latent heat of saturated steam, J/kg 973.31×103
Richardson number Ri 0.022
Reynolds number Re 26997662
Step 4, solving a flow heat transfer control equation, and monitoring the temperature and speed change of the cold and hot fluid mixing process at the monitoring point, wherein the method specifically comprises the following steps:
4.1) selecting a transient solver on the basis of the step 3;
4.2) selecting a VOF two-phase flow model and selecting a readable k-turbulence model;
4.3) setting the variation trend of the cold and hot fluid density along with the temperature according to a polynomial function, and setting the vapor phase density to change according to an ideal gas law;
4.4) processing The Pressure-speed coupling relation of The continuous equation and The momentum equation by adopting a PISO (The Pressure-Implicit with Splitting of Operators) algorithm, wherein The discrete format of each control equation is in a QUICK format, The iterative solution is carried out by setting The time step, and The specific process is as follows: and setting a proper time step length, and sequentially solving a momentum equation, an energy equation, a component equation and a turbulence equation by using a conventional CFD pressure-based solver in sequence.
Step 5, analysis of calculation results
5.1) after the calculation is finished, compiling a macro file by using a VBA function to extract and integrate the temperature and the speed on a typical section line, wherein the sampling time interval is 0.001s, the total sampling time is from 0.6s to 5s, and the total number of the acquisition points is 4400. From the collected data, the time-mean dimensionless value and the root-mean-square dimensionless value of the velocity and the temperature were calculated, respectively, and the calculation results were compared with the experimental results, as shown in fig. 5 and 6. It can be seen that the simulated values fit the experimental values more closely, despite some differences between the two. The comparison result shows that the readable k-turbulence model and the VOF multi-phase flow thermal model can effectively and economically predict the complex mixing process of the cold and hot fluid in the voltage stabilizer when positive fluctuation occurs.
5.2) observing and analyzing the internal flow field of the cold and hot fluid mixture at different moments in the wave-in process by using CFD post-processing software, and analyzing the corresponding speed, temperature change and evolution process of mixing, as shown in FIG. 7.
5.3) in order to qualitatively explain the fluctuation intensity of the speed and the temperature in a period of time, the y-direction root-mean-square dimensionless speed and temperature distribution diagram of different positions on the central section of the lower end socket of the voltage stabilizer is analyzed, as shown in figures 8 and 9. It can be seen that when the transient wave occurs, the mixing of cold and hot fluids mainly occurs in the region of-0.5 m < z <0.5 m; the most severe temperature and speed fluctuation places are concentrated on-0.2 m < z <0.2m, and the fluctuation peak value of the fluctuation gradually becomes larger along with the advancing of the wave-in process. In order to ensure the reliability of the stable operation of the electric heating element and reduce the influence of the speed and the thermal oscillation generated in the mixing process of the cold fluid and the hot fluid on the electric heating element, the electric heater in the voltage stabilizer should be prevented from being arranged in a region of-0.5 m < z <0.5m as much as possible.
The invention adopts a three-dimensional transient multi-phase flow heat transfer model to accurately predict the mixing fluctuation process of the cold and hot fluid in the voltage stabilizer, finds the range with the most severe speed and temperature fluctuation in the voltage stabilizer, proposes the idea of determining the arrangement range of the electric heating element according to the speed and temperature fluctuation degree, proposes that the electric heating element should be prevented from being arranged in the place with severe fluctuation degree, and guides the practical engineering from the perspective of a flow heat transfer mechanism.
The idea of establishing a three-dimensional full-size geometric model of the nuclear power station voltage stabilizer cavity is provided, and a foundation is laid for the prediction of the subsequent cold and hot fluid mixing fluctuation process and the further development of the subsequent work.
Through specific practical experiments, the experimental conditions are as shown above, the root mean square dimensionless speed and the temperature distribution of the lower end socket obtained through the experiments are shown in fig. 5 and 6, and it can be seen that the average error of the speed fluctuation intensity between the three simulation curves and the measured value is 4.6%, and the maximum error is 14.8%. The average error of the temperature fluctuation intensity is 2.3 percent, and the maximum error is 6 percent. The error is mainly concentrated in the geometric center of the voltage stabilizer. Compared with experimental data, the numerical result has acceptable error of 15%, and the effectiveness of the simulation calculation method is proved.
Compared with the prior art, the method adopts the three-dimensional transient multi-phase flow heat transfer model to accurately predict the mixing fluctuation process of the cold and hot fluid in the voltage stabilizer, proposes the idea of determining the arrangement range of the electric heating element by using the speed and the temperature fluctuation degree, can be used for specific arrangement of the conductive heating element, and fills the theoretical blank of the engineering practice.
The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (8)

1. A nuclear power station voltage stabilizer electric heating element arrangement method based on a three-dimensional transient heat transfer mechanism is characterized in that firstly, reasonable three-dimensional modeling is carried out on a voltage stabilizer, grid division is carried out, then, based on a CFD method, an RKE model is used for carrying out numerical simulation on the mixing phenomenon of cold and hot fluid in the voltage stabilizer during positive fluctuation by combining a VOF multiphase flow heat transfer model, finally, the time-mean dimensionless and root-mean-square dimensionless processing is carried out on the numerical simulation result to represent the average value and the fluctuation condition of speed and temperature in the mixing process, and the accurate range of reasonable arrangement of electric heating elements in a lower end socket of the voltage stabilizer is obtained by analyzing the fluctuation intensity of the speed and the;
the three-dimensional modeling means that: a simplified three-dimensional full-size geometric model of a cavity of a voltage stabilizer of a nuclear power station is established, the condition of mixed fluctuation of cold and hot fluid in the voltage stabilizer is analyzed from a source, structures such as an electric heater rod, a supporting plate, a guide plate, a screen, a fluctuation pipe and a connecting pipe of the voltage stabilizer in the voltage stabilizer are ignored, a lower end socket of the voltage stabilizer is processed into the cavity, transient flow of a gas-liquid two-phase interface in the voltage stabilizer is described by an RANS equation based on a VOF multiphase flow model, the whole solving system is closed by a coupling RKE turbulence model, a coordinate system is established by the model by taking the circle center of the middle section of a cylinder of the.
2. The method as recited in claim 1, wherein the three-dimensional modeling is a grid division of a full hexahedron structure and blocks.
3. The method as claimed in claim 1, wherein the density of the cold and hot fluid in the mixing phenomenon of the cold and hot fluid in the pressurizer is a polynomial function of temperature to estimate the influence of the buoyancy term, and the method comprises: p 737.9063+1.81776T-0.00322T2Wherein: rho is the density of the water body, T is the temperature of the water body, and the compressibility of the water vapor is described by adopting an ideal gas law.
4. The method of claim 1, wherein the three-dimensional modeling is to reduce computation time and simplify modeling, and the effects of heat conduction between the fluid and the pipe wall and the direction inside the pipe wall are ignored while taking into account thermal convection and conduction, and wherein: the energy equation for considering thermal convection and conduction is:
Figure FDA0002624781670000011
Figure FDA0002624781670000012
wherein: subscript k is a gas or liquid, subscript i is a non-k phase, αk，ρk，
Figure FDA0002624781670000013
HkVolume fraction, density, velocity, enthalpy of each phase,
Figure FDA0002624781670000014
for mass transfer from the k-phase to the i-phase, the first term on the right is the pressure induced enthalpy change, the second term is the combination of molecular and turbulent heat fluxes, and the third term is the change in enthalpy due to diffusion mass flux.
5. The method as claimed in claim 1, wherein the grid division is performed by using CFD preprocessing software, and in order to better simulate the region where the flow velocity gradient and the heat transfer temperature gradient are drastically changed, the grid at the joint of the lower head and the surge pipe is subjected to secondary segmentation and topology operation, so as to encrypt the grid in the region.
6. The method for arranging the electrical heating elements of the nuclear power plant voltage stabilizer according to claim 1, wherein the numerical simulation is carried out by constructing a three-dimensional transient heat transfer mathematical model of mixed flow of cold and hot fluid in a cavity of the voltage stabilizer, determining an initial working condition and a boundary condition according to thermal functional test data of the nuclear power plant, then solving a flow heat transfer control equation, and monitoring the temperature and speed change of a cold and hot fluid mixing process at a monitoring point;
the change monitoring means that: the steam-water liquid level reconstruction adopts a Modified HRIC format, and adopts time-mean dimensionless values to describe the average value of the temperature in the mixing process, wherein the time-mean dimensionless temperature is as follows:
Figure FDA0002624781670000021
wherein:
Figure FDA0002624781670000022
is dimensionless temperature, ThotIs hot fluid, TcoldIs cold fluid, N is the total number collected in the calculation time, i is variable, Ti *Dimensionless temperature, T, for collection pointiThe temperature of the mixed water body at the collection point.
7. The method of claim 1, wherein the initial operating conditions and the boundary conditions comprise: setting a wall thermal boundary as a heat insulation boundary, and keeping the wall thermal boundary static, smooth and non-slip; setting the corresponding calculation domains of the water phase and the vapor phase and the initial pressure.
8. The method as claimed in claim 6, wherein the average and fluctuation of the speed and temperature during the mixing process is: the characterization method for determining the thermal fluctuation and the speed fluctuation intensity of the cold and hot fluid mixing dynamic process in the voltage stabilizer obtains the distribution and the change rule of an instantaneous speed field, a pressure field and temperature by using CFD post-processing software, and specifically comprises the following steps:
describing the fluctuation intensity of the temperature in the mixing process by adopting a root-mean-square dimensionless value, wherein the root-mean-square dimensionless temperature is as follows:
Figure FDA0002624781670000023
wherein: n is the total number collected in the calculation time, i is variable, Ti *Is a non-dimensional temperature of the collection point,
Figure FDA0002624781670000024
the non-dimensional temperature is the acquisition point;
secondly, describing the average value of the speed in the mixing process by adopting the time-mean dimensionless value, wherein the time-mean dimensionless speed is as follows:
Figure FDA0002624781670000025
wherein: vmIndicating the speed of wave-in, ViFor the non-dimensional speed of the acquisition point,
Figure FDA0002624781670000026
the non-dimensional speed is obtained at the acquisition point;
thirdly, the fluctuation intensity of the speed in the mixing process is described by adopting a root-mean-square dimensionless value, and the root-mean-square dimensionless speed is as follows:
Figure FDA0002624781670000031
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CN112989727A (en) * 2021-05-10 2021-06-18 中国空气动力研究与发展中心低速空气动力研究所 Wall surface temperature simulation method of anti-icing system
CN114004173A (en) * 2021-10-29 2022-02-01 上海交通大学 Optimized arrangement method for electric heating elements of voltage stabilizer of nuclear power station
CN116882314A (en) * 2023-07-06 2023-10-13 昆明理工大学 Method for carrying out heat optimization design on steel piston head of high-strength diesel engine

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