Method, terminal and medium for constructing discretization model of steam generator in nuclear power plant

Abstract

The present invention relates to the technical field of nuclear power plant simulation and operation optimization, and discloses a method, device, terminal, and medium for constructing a discrete model of a nuclear power plant steam generator. The method for constructing a discrete model of a nuclear power plant steam generator of the present invention comprises the following steps: obtaining operating data of the working fluid at the primary and secondary inlets of the steam generator at time j; establishing a descending channel model based on the operating data of the working fluid at the secondary inlet and the temperature, pressure, and flow rate of the primary and secondary circuit working fluids calculated by the model at time j-1, and obtaining the state variables of the working fluid at the bottom outlet of the descending channel at time j; the method for constructing a discrete model of a nuclear power steam generator provided by the present invention can obtain an accurate value of the vaporization starting height of the steam generator secondary side ascending channel, further reduce the cumulative error of the boiling section of the secondary side ascending channel, obtain a more accurate distribution of the working fluid temperature, pressure, flow rate, and gas holdup, and significantly improve the simulation speed of the model.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear power plant simulation and operation optimization, and in particular to a method, terminal and medium for constructing a discrete model of a nuclear power plant steam generator. Background Art

[0002] The vertical inverted U-shaped natural circulation steam generator is one of the key pieces of equipment widely used in nuclear power generation. The steam generator transfers heat from the primary coolant to the secondary working fluid, while simultaneously shielding the primary coolant from radiation. The secondary working fluid entering the steam generator is distributed to the hot and cold sections via a feedwater ring. The feedwater mixes with recirculating water from the steam-water separator outlet to form circulating water. The circulating water flows through descending and ascending channels, where it exchanges heat with the metal walls of the inverted U-shaped tubes and boils, forming a gas-liquid two-phase flow. This two-phase flow enters the steam-water separator, where the liquid phase becomes recirculating water and the gas phase flows into the steam main.

[0003] In computer simulation of steam generators, especially in the solution of distributed parameter models, the steam generator needs to be divided into several control volumes. In the solution of the secondary circuit rising channel, the control volume where the working fluid temperature first reaches the saturation temperature corresponding to the pressure is defined as the vaporization start control volume, and the height of the vaporization start control volume is defined as the vaporization start height. The vaporization start control volume is calculated as a liquid phase or a gas-liquid mixed phase. This will lead to truncation errors and cause jumps in the output variables when the height of the vaporization start control volume changes. To this end, we propose a discretization model construction method, terminal, and medium for nuclear power plant steam generators to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem in the prior art that in the computer simulation of the steam generator, especially in the solution of the distributed parameter model, the steam generator needs to be divided into several control bodies; wherein, in the solution of the secondary circuit rising channel, the control body where the working fluid temperature first reaches the saturation temperature corresponding to the pressure is defined as the vaporization start control body, the height of the vaporization start control body is defined as the vaporization start height, and the vaporization start control body is calculated as a liquid phase or a gas-liquid mixed phase; this will bring about truncation errors and cause the output variable to jump when the height of the vaporization start control body changes. A method, terminal and medium for constructing a discrete model of a nuclear power plant steam generator are proposed.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for constructing a discretized model of a steam generator in a nuclear power plant comprises the following steps:

[0007] Obtain the operating data of the working fluid at the primary and secondary sides of the steam generator at time j;

[0008] Based on the operating data of the working fluid at the secondary side inlet and the temperature, pressure and flow rate of the working fluid in the primary and secondary circuits calculated by the model at time j-1, a descending channel model is established to obtain the state variables of the working fluid at the bottom outlet of the descending channel at time j;

[0009] According to the state variables of the working fluid at the bottom outlet of the descending channel, the state variables of the calculated control body, and the temperature, pressure, and flow rate of the working fluid in the first and second circuits calculated by the model at time j-1, the relevant model of the control body i is established;

[0010] Determine whether the control body i at time j-1 has vaporized;

[0011] According to the temperature and pressure of the secondary side working medium of the control body i, determine whether the secondary side working medium here is saturated;

[0012] The data obtained in the previous step, the state variables of the control body that have been calculated, and the output value calculated by the model at time j-1 are used as the input value of the model corresponding to time i+1;

[0013] Determine whether the control body calculation is completed;

[0014] Based on the temperature, pressure and gas holdup at each position of the steam generator obtained in the above steps, the physical properties of the working fluid at each position of the steam generator at time j are calculated and used for calculation at time j+1.

[0015] According to one embodiment of the discretized model construction method for a nuclear power plant steam generator of the present invention, a relevant model of control body i is established based on the state variables of the working fluid at the outlet of the bottom of the downcomer, the calculated state variables of the control body, and the temperature, pressure, and flow rate of the working fluid in the primary and secondary circuits calculated by the model at time j-1. The calculation steps are as follows:

[0016] Establish a primary coolant model for control body i and calculate the temperature, pressure, and flow rate of the primary side working fluid;

[0017] An inverted U-shaped tube metal wall model of the control body i is established, and the metal wall temperature and the heat transfer coefficient between the metal wall and the primary and secondary working fluids are calculated.

[0018] Establish the secondary circuit working medium preheating section model of control body i and calculate the temperature, pressure and flow rate of the secondary side working medium;

[0019] The output values of the primary coolant model, inverted U-shaped tube metal wall model and secondary working fluid preheating section model of control body i are respectively used as the input values of the primary coolant model, inverted U-shaped tube metal wall model and secondary working fluid preheating section model of control body i+1.

[0020] According to one embodiment of the method for constructing a discretized model of a steam generator in a nuclear power plant of the present invention, whether the secondary-side working medium is saturated is determined based on the temperature and pressure of the secondary-side working medium of control volume i. If not, the method returns to step 3 to calculate the primary coolant model, the inverted U-shaped tube metal wall model, and the secondary-circuit working medium preheating section model of control volume i+1.

[0021] If control volume i is saturated, then control volume i is defined as the vaporization start control volume, and a secondary circuit working medium vaporization start control volume model is established to obtain the state variables of the liquid phase and the gas-liquid mixed phase of the vaporization start control volume. The state variables include: the temperature, pressure, flow rate, and gas holdup of the liquid phase and the gas-liquid mixed phase of the vaporization start control volume.

[0022] According to one embodiment of the method for constructing a discretized model of a nuclear power plant steam generator of the present invention, the data obtained in the previous step, the state variables of the calculated control body, and the output value calculated by the model at time j-1 are used as the input value of the model corresponding to time i+1. The calculation steps are as follows:

[0023] Establish a primary coolant model for control body i and calculate the temperature, pressure and flow rate of the primary side working fluid;

[0024] An inverted U-shaped tube metal wall model of the control body i is established, and the metal wall temperature and the heat transfer coefficient between the metal wall and the primary and secondary working fluids are calculated.

[0025] Establish a boiling section model of the secondary circuit working fluid of control body i and calculate the temperature, pressure, flow rate and gas holdup of the secondary side working fluid;

[0026] The output values of the primary coolant model, inverted U-tube metal wall model and secondary working medium boiling section model of control body i are respectively used as the input values of the primary coolant model, inverted U-tube metal wall model and secondary working medium preheating section model of control body i+1.

[0027] According to one embodiment of the method for constructing a discretized model of a steam generator in a nuclear power plant of the present invention, it is determined whether the calculation of the control body is completed. If the calculation of any control body is not completed, the process returns to step 6 to calculate the primary circuit coolant model, the inverted U-shaped tube metal wall model, and the secondary circuit working medium boiling section model of the control body i+1;

[0028] If all control bodies have been calculated, the temperature, pressure, flow rate, and gas holdup of the outlet working fluid of the last control body obtained in S6 are used to establish a steam-water separator model to obtain the temperature, pressure, flow rate, and mass flow of the gas phase working fluid at the steam-water separator outlet.

[0029] In order to achieve the above-mentioned object of the invention, the present invention provides a device for constructing a discretized model of a steam generator in a nuclear power plant, which comprises:

[0030] An operation data acquisition module is used to obtain the operation data of the working fluid at the primary and secondary sides of the steam generator at time j;

[0031] The descending channel model establishment module is used to establish the descending channel model based on the operating data of the secondary side inlet working fluid and the temperature, pressure, and flow rate of the primary and secondary circuit working fluids calculated by the model at time j-1, and obtain the state variables of the working fluid at the bottom outlet of the descending channel at time j;

[0032] The relevant model building module of the control body i is used to build the relevant model of the control body i according to the state variables of the working fluid at the bottom outlet of the descending channel, the calculated state variables of the control body, and the temperature, pressure, and flow rate of the primary and secondary circuit working fluids calculated by the model at time j-1;

[0033] A vaporization judgment module is used to judge whether the control body i at time j-1 has vaporized;

[0034] A saturation judgment module is used to judge whether the secondary side working medium of the control body i is saturated according to the temperature and pressure of the secondary side working medium;

[0035] A model calculation and transmission module is used to use the data obtained by the saturation judgment module, the state variables of the control body that have completed the calculation, and the output value calculated by the model at time j-1 as the input value of the model corresponding to time i+1;

[0036] Calculation judgment module, used to judge whether the control body calculation is completed;

[0037] The physical property parameter calculation module is used to calculate the physical property parameters of the working fluid at each position of the steam generator at time j based on the temperature, pressure and gas holdup at each position of the steam generator obtained by all the above modules, and use them for calculation at time j+1.

[0038] According to one embodiment of the discretization model building device for a steam generator in a nuclear power plant of the present invention, the relevant model building module of the control body i includes:

[0039] The first coolant model establishment unit is used to establish a primary-circuit coolant model of the control body i and calculate the temperature, pressure and flow rate of the primary-side working fluid;

[0040] The first metal wall model establishment unit is used to establish an inverted U-shaped tube metal wall model of the control body i, and calculate the metal wall temperature and the heat transfer coefficient between the metal wall and the primary and secondary side working media;

[0041] The preheating section model building unit is used to build the preheating section model of the secondary circuit working medium of the control body i and calculate the temperature, pressure and flow rate of the secondary side working medium;

[0042] The data transmission unit is used to use the output values of the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working fluid preheating section model of the control body i as the input values of the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working fluid preheating section model of the control body i+1 respectively.

[0043] According to one embodiment of the apparatus for constructing a discretized model of a steam generator in a nuclear power plant according to the present invention, the model calculation and transmission module includes:

[0044] The second coolant model establishment unit is used to establish a primary-circuit coolant model of the control body i and calculate the temperature, pressure and flow rate of the primary-side working fluid;

[0045] The second metal wall model establishment unit is used to establish an inverted U-shaped tube metal wall model of the control body i, and calculate the metal wall temperature and the heat transfer coefficient between the metal wall and the primary and secondary side working media;

[0046] The boiling section model establishment unit is used to establish the boiling section model of the secondary circuit working medium of the control body i and calculate the temperature, pressure, flow rate and gas holdup of the secondary side working medium;

[0047] The data transmission unit uses the output values of the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working medium boiling section model of the control body i as the input values of the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working medium preheating section model of the control body i+1 respectively.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] 1. The method for constructing a discretized model of a nuclear power steam generator provided by the present invention can obtain the precise value of the vaporization starting height of the secondary side rising channel of the steam generator, further reduce the cumulative error of the boiling section of the secondary side rising channel, and obtain a more accurate distribution of the working fluid temperature, pressure, flow rate, and gas holdup.

[0050] 2. The method for constructing a discretized model of a nuclear power steam generator provided by the present invention uses the working fluid physical parameters of the previous moment to replace the physical parameters of the current moment, which can significantly improve the simulation speed of the model. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 This is a flow chart of a method for constructing a discretized model of a nuclear power plant steam generator proposed in the present invention;

[0052] Figure 2 This is a graph showing changes in output power of a nuclear power unit according to an embodiment of the present invention;

[0053] Figure 3 This is a simulation result diagram of the gas holdup of the working medium in the hot section secondary circuit in an embodiment of the present invention;

[0054] Figure 4 This is a diagram showing the simulation results of the working medium temperature in the hot section secondary circuit in an embodiment of the present invention;

[0055] Figure 5 Schematic diagram of the calculation steps for establishing the relevant models of the control body i in the method for constructing a discretized model of a nuclear power plant steam generator proposed by the present invention;

[0056] Figure 6 This is a schematic diagram of the calculation flow of step 4 of the method for constructing a discretized model of a nuclear power plant steam generator proposed by the present invention. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0058] Reference Figure 1-6 A method for constructing a discretized model of a steam generator in a nuclear power plant comprises the following steps:

[0059] S1: Obtain the operating data of the working fluid at the primary and secondary inlets of the steam generator at time j, including the temperature, pressure, and mass flow rate of the working fluid at the primary and secondary inlets;

[0060] S2: According to the operating data of the secondary side inlet working fluid and the temperature, pressure and flow rate of the primary and secondary circuit working fluids calculated by the model at time j-1, a descending channel model is established to obtain the state variables of the working fluid at the bottom outlet of the descending channel at time j. The state variables include: the temperature, pressure and mass flow rate of the working fluid at the bottom outlet of the descending channel. The descending channel model is divided into a hot section model and a cold section model, accounting for of feed water flows into the hot section, accounting for of feed water flows into the cold section, accounting for of recycled water flows into the hot section, accounting for The recirculating water flows into the cold section, and the hot section model of the descending channel model is constructed by the following formula:

[0061]

[0062]

[0063]

[0064]

[0065] In the formula, superscript j is the current moment, j-1 is the previous moment, and dt is the discrete calculation time interval; G HL,DCis the working fluid mass flow rate at the outlet of the hot section descending channel; G fw is the total mass flow of water at the inlet of the hot and cold section descending channels; G rw is the mass flow rate of recirculating water at the inlet of the hot and cold section descending channels; ρ HL,DC is the working fluid density in the hot section descending channel; A DC is the flow area of the descending channel; H DC is the height of the descending channel; T HL,DC is the working fluid temperature at the outlet of the hot section descending channel; Cp fw is the constant pressure specific heat of the feed water at the downcomer inlet; Cp rw is the constant pressure specific heat of the recirculating water at the inlet of the downcomer; T fw is the temperature of the feed water at the inlet of the downcomer; T rw is the temperature of the recirculating water at the inlet of the downcomer; p HL,DC is the outlet pressure of the working fluid in the hot section descending channel; p HL,DC,in is the working fluid pressure at the inlet of the hot section descending channel; f HL,DC is the friction factor of the hot section descending channel; D DC is the hydraulic diameter of the descending channel; g is the acceleration due to gravity; μ HL,DC is the viscosity of the working fluid in the descending channel of the hot section;

[0066] The cold segment model of the descending channel model is constructed using the following formula:

[0067]

[0068]

[0069]

[0070]

[0071] Where G CL,DC is the mass flow rate of the working fluid at the outlet of the cold section descending channel; ρ CL,DC is the working fluid density in the cold section descending channel; A CL,DC is the flow area of the cold section descending channel; T CL,DC is the working fluid temperature at the outlet of the cold section descending channel; Cp CL,fw Cp is the constant pressure specific heat of the feed water at the inlet of the cold section downpipe; CL,rw is the constant pressure specific heat of the recirculating water at the inlet of the cold section downflow channel; p CL,DC is the outlet pressure of the working fluid in the cold section descending channel; p CL,DC,in is the working fluid pressure at the inlet of the cold section descending channel; f CL,DC is the friction factor of the cold section descending channel; μ CL,DC is the viscosity of the working fluid in the cold section descending channel;

[0072] S3: Based on the state variables of the working fluid at the bottom outlet of the descending channel, the calculated state variables of the control body, and the temperature, pressure, and flow rate of the working fluid in the first and second circuits calculated by the model at time j-1, the relevant model of the control body i is established. The calculation steps are as follows:

[0073] S301: Establish a primary coolant model for control body i and calculate the temperature, pressure, and flow rate of the primary side working fluid. The primary coolant model is divided into a hot section model and a cold section model. The hot and cold section models differ only in the inlet variables, and their models and calculation methods are consistent. The hot and cold section models of the primary coolant model are constructed using the following formulas:

[0074]

[0075]

[0076]

[0077]

[0078] in:

[0079]

[0080]

[0081]

[0082] In the formula, superscript i is the control body number, j is the current time; K PS is the heat transfer coefficient between the primary side working medium and the metal wall; Re PS is the Reynolds number of the working fluid in a circuit; Pr PS is the Prandtl number of the primary circuit working medium; λ PS is the thermal conductivity of the working fluid in a circuit; D PS is the inner diameter of the inverted U-shaped tube; W PS is the primary side working fluid flow rate; G PS is the mass flow rate of the working fluid on the primary side; ρ PS is the density of the working fluid in a circuit; A PS is the primary circuit flow area; p PS is the working fluid pressure of a circuit; f PS is the friction factor of the working medium on the primary side; dz is the height of the control body; g is the acceleration of gravity; T PS is the working medium temperature of a circuit; Cp PS is the constant pressure specific heat of the primary side working fluid; V PS is the volume of the control volume of a loop; S MT is the heat transfer area of the metal wall; T MT is the metal wall temperature; dt is the discrete calculation step size; μ PSis the primary side working fluid viscosity; λ PR is the thermal conductivity of the working fluid on the primary side;

[0083] S302: Establish an inverted U-shaped tube metal wall model for control body i, calculate the metal wall temperature and the heat transfer coefficient between the metal wall and the primary and secondary working media. The inverted U-shaped tube metal wall model is divided into a hot section model and a cold section model. The hot and cold section models differ only in the inlet variables, and their models and calculation methods are the same. The hot and cold section models of the inverted U-shaped tube metal wall model are constructed using the following formulas:

[0084]

[0085] Where, T RC is the working medium temperature in the secondary circuit rising channel; K RC is the heat transfer coefficient between the working fluid and the metal wall in the secondary circuit rising channel; ρ MT is the metal wall density; Cp MT is the specific heat of the metal wall at constant pressure, V MT is the volume of the metal wall;

[0086] S303: Establish a secondary circuit working medium preheating section model for control body i, and calculate the temperature, pressure, and flow rate of the secondary side working medium. The secondary circuit working medium preheating section model is divided into a hot section model and a cold section model. The hot and cold section models differ only in the inlet variables, and their models and calculation methods are consistent. The hot and cold section models of the circuit working medium preheating section model are constructed using the following formulas:

[0087]

[0088]

[0089]

[0090]

[0091] in:

[0092]

[0093]

[0094]

[0095] In the formula, superscript i is the control body number, j is the current time; K PR is the heat transfer coefficient between the working medium and the metal wall in the secondary preheating section; Re PR is the Reynolds number of the working medium in the secondary preheating section; Pr PR is the Prandtl number of the working medium in the secondary preheating section; PR is the thermal conductivity of the working medium in the secondary side preheating section; DRC is the hydraulic diameter of the secondary side rising channel; W PR is the working medium flow rate in the secondary side preheating section; G PR is the mass flow rate of the working medium in the preheating section of the secondary circuit; ρ PR is the working fluid density in the preheating section of the secondary circuit; A RC is the flow area of the secondary side rising channel; p PR is the working medium pressure in the secondary side preheating section; f PR is the friction factor of the working medium in the secondary circuit preheating section; dz is the height of the control body; g is the acceleration of gravity; T PR is the working medium temperature in the secondary side preheating section; Cp PR V is the constant pressure specific heat of the working medium in the preheating section of the secondary circuit; PR is the volume of the control volume of the secondary side preheating section; S MT is the heat transfer area of the metal wall; T MT is the metal wall temperature; dt is the discrete calculation step size; μ PS is the viscosity of the working fluid in the secondary side preheating section; PR is the thermal conductivity of the working medium in the secondary side preheating section;

[0096] S304: Using the output values of the primary circuit coolant model, the inverted U-shaped tube metal wall model, and the secondary circuit working medium preheating section model of control body i as the input values of the primary circuit coolant model, the inverted U-shaped tube metal wall model, and the secondary circuit working medium preheating section model of control body i+1, respectively;

[0097] S4: Determine whether the control body i at time j-1 has vaporized. If the control body i at time j-1 has vaporized, extrapolate the physical parameters of the secondary side rising channel working fluid and calculate them using the following formula:

[0098]

[0099]

[0100]

[0101]

[0102]

[0103] In the formula, the superscript i is the serial number of the control body to be determined, i S is the current control body number; ρ PR is the working medium density in the secondary side preheating section; h PR is the specific enthalpy of the working medium in the secondary side preheating section; PR is the thermal conductivity of the working medium in the secondary side preheating section; μ PR is the viscosity of the working fluid in the secondary side preheating section; Cp PRis the constant pressure specific heat of the working fluid in the secondary side preheating section;

[0104] S5: Based on the temperature and pressure of the secondary-side working medium of control volume i, determine whether the secondary-side working medium here is saturated. If not, return to step 3 to calculate the primary circuit coolant model, inverted U-shaped tube metal wall model, and secondary circuit working medium preheating section model of control volume i+1;

[0105] If the control body i is saturated, then the control body i is defined as the vaporization start control body, and the secondary circuit working medium vaporization start control body model is established to obtain the state variables of the liquid phase and the gas-liquid mixed phase of the vaporization start control body. The state variables include: the temperature, pressure, flow rate and gas holdup of the liquid phase and the gas-liquid mixed phase of the vaporization start control body. The vaporization start control body refers to the first control body whose secondary circuit working medium temperature is higher than the saturation temperature corresponding to its pressure. The control body number is defined as i. s .

[0106] The secondary circuit working medium vaporization initial control body model is constructed using the following formula:

[0107]

[0108]

[0109]

[0110]

[0111]

[0112] In the formula, superscript i is the control body number; T BR is the working medium temperature in the preheating section of the secondary circuit; p BR is the working medium pressure in the preheating section of the secondary circuit; p BR is the working medium pressure in the preheating section of the secondary circuit; T S,p i It is p BR i The corresponding saturation temperature; H BR is the vaporization starting height; dz is the control body height; φ BR k is the proportion of the gas-liquid mixed phase working medium in the vaporization starting control body; p and k T is an intermediate variable, including T BR and T S The rate of change information, k p (1) represents k p The first element, the rest are similar; T S is the temperature at which the secondary circuit working medium starts to boil; p S It's T S The corresponding saturation pressure;

[0113]

[0114]

[0115]

[0116]

[0117]

[0118]

[0119]

[0120]

[0121]

[0122]

[0123]

[0124] In the formula, superscript i is the control body number, j is the current time; K BR is the heat transfer coefficient between the working fluid and the metal wall in the boiling section of the secondary circuit; Kfc BR is the forced convection heat transfer coefficient between the working fluid and the metal wall in the boiling section of the secondary circuit; Knb BR is the nucleate boiling heat transfer coefficient between the working medium and the metal wall in the secondary circuit boiling section; S BR is the two-phase flow suppression factor; Re BR is the Reynolds number of the working medium in the boiling section of the secondary circuit; Pr BR is the Prandtl number of the working medium in the boiling section of the secondary circuit; T MT is the metal wall temperature; T BR is the working medium temperature in the boiling section of the secondary circuit; p BR is the working medium pressure in the boiling section of the secondary circuit; p S is the saturated static pressure of the working medium in the boiling section of the secondary circuit; σ BR is the surface tension coefficient of the liquid phase working medium in the boiling section of the secondary circuit; μ S,L is the viscosity of the saturated liquid phase in the boiling section of the secondary circuit; h S,V is the specific enthalpy of the saturated gas phase working medium in the boiling section of the secondary circuit; h S,L is the specific enthalpy of the saturated liquid phase working medium in the boiling section of the secondary circuit; h BR is the specific enthalpy of the working medium in the boiling section of the secondary circuit; Cp BR is the constant pressure specific heat of the working medium in the boiling section of the secondary circuit; μ PS is the viscosity of the working fluid in the secondary boiling section; PR is the thermal conductivity of the working fluid in the secondary boiling section; ρS,V is the density of saturated gas phase working medium in the boiling section of the secondary circuit; ρ S,L is the density of saturated liquid phase working medium in the boiling section of the secondary circuit; μ S,V is the viscosity of the saturated gas phase working medium in the boiling section of the secondary circuit; μ S,L is the viscosity of the saturated liquid phase in the boiling section of the secondary circuit; Φ BR is the full liquid phase conversion coefficient of the secondary side working fluid;

[0125] S6: Based on the data obtained in the previous step, the state variables of the control body that have been calculated, and the output value calculated by the model at time j-1, the input value of the model corresponding to time i+1 is used. The calculation steps are as follows:

[0126] S601: Establish a primary-circuit coolant model for control body i and calculate the temperature, pressure, and flow rate of the primary-side working fluid;

[0127] S602: Establish an inverted U-shaped tube metal wall model of the control body i, and calculate the metal wall temperature and the heat transfer coefficient between the metal wall and the primary and secondary working media;

[0128] S603: Establish a secondary circuit working fluid boiling section model for control body i, and calculate the temperature, pressure, flow rate, and gas holdup of the secondary side working fluid. The secondary circuit working fluid boiling section model is divided into a hot section model and a cold section model. The hot and cold section models only differ in inlet variables, and their models and calculation methods are consistent.

[0129] The hot and cold section models of the secondary circuit working medium boiling section model are constructed using the following formulas:

[0130]

[0131]

[0132]

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139]

[0140]

[0141]

[0142]

[0143]

[0144] in:

[0145]

[0146]

[0147] In the formula, superscript i is the control body number, j is the current time; K BR is the heat transfer coefficient between the working medium and the metal wall in the boiling section of the secondary circuit; F BR is the two-phase flow enhancement factor; S BR is the two-phase flow suppression factor; Xtt BR is the Martinelli parameter of the two-phase flow of the working medium in the boiling section of the secondary circuit; Re BR is the Reynolds number of the working medium in the boiling section of the secondary circuit; Pr BR is the Prandtl number of the working medium in the boiling section of the secondary circuit; BR is the thermal conductivity of the working fluid in the boiling section of the secondary circuit; Cp BR is the constant pressure specific heat of the working medium in the boiling section of the secondary circuit; T MT is the metal wall temperature; T BR is the working medium temperature in the boiling section of the secondary circuit; p BR is the working medium pressure in the boiling section of the secondary circuit; p S is the saturated static pressure of the working medium in the boiling section of the secondary circuit; σ BR is the surface tension coefficient of the liquid phase working medium in the boiling section of the secondary circuit; h S,V is the specific enthalpy of the saturated gas phase working medium in the boiling section of the secondary circuit; h S,L is the specific enthalpy of the saturated liquid phase working medium in the boiling section of the secondary circuit; h BR is the specific enthalpy of the working medium in the boiling section of the secondary circuit; ρ S,V is the density of saturated gas phase working medium in the boiling section of the secondary circuit; ρ S,L is the density of the saturated liquid phase working medium in the boiling section of the secondary circuit; ρ BR is the working medium density in the boiling section of the secondary circuit; μ S,V is the viscosity of the saturated gas phase working medium in the boiling section of the secondary circuit; μ S,L is the density of the saturated liquid phase working medium in the boiling section of the secondary circuit; W BR is the working medium flow rate in the boiling section of the secondary circuit; A RC is the flow area of the secondary circuit rising channel; V RC It controls the volume of the secondary circuit rising channel in the body; S MT It controls the heat transfer area of the metal wall inside the body; T S is the saturation temperature of the working medium in the boiling section of the secondary circuit; x BRis the gas holdup of the working medium in the boiling section of the secondary circuit; β BR is the volumetric gas holdup of the working medium in the boiling section of the secondary circuit; Φ BR is the full liquid phase conversion coefficient of the secondary side working fluid;

[0148] S604: Using the output values of the primary coolant model, the inverted U-tube metal wall model, and the secondary working medium boiling section model of control volume i as the input values of the primary coolant model, the inverted U-tube metal wall model, and the secondary working medium preheating section model of control volume i+1, respectively;

[0149] S7: Determine whether the control body calculation is completed. If the control body calculation is not completed, return to step 6 to calculate the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working medium boiling section model of the control body i+1;

[0150] If all control bodies have been calculated, the temperature, pressure, flow rate, and gas holdup of the outlet working fluid of the last control body obtained in S6 are used to establish a steam-water separator model, and the temperature, pressure, flow rate, and mass flow rate of the gas phase working fluid at the steam-water separator outlet are obtained. The steam-water separator model is a hot and cold section two-phase flow mixing model.

[0151] The water separator model is constructed using the following formula:

[0152]

[0153]

[0154]

[0155] in:

[0156]

[0157] Where, the superscript I is the number of the control body at the top of the inverted U-shaped tube, that is, the total number of control bodies; G SP is the mass flow rate of saturated dry steam at the outlet of the steam-water separator; G rw is the mass flow rate of recirculating water at the outlet of the steam-water separator; is the working fluid gas holdup at the outlet of the rising channel of the hot section secondary circuit; is the working fluid gas holdup at the outlet of the rising channel of the secondary circuit of the cold section; is the working fluid mass flow rate at the outlet of the rising channel of the hot section secondary circuit; is the mass flow rate of the working medium at the outlet of the rising channel of the secondary circuit of the cold section; η is the separation efficiency of the steam-water separator; p SP is the pressure of saturated dry steam at the outlet of the steam-water separator; is the working fluid pressure at the outlet of the rising channel of the hot section secondary circuit; is the outlet pressure of the rising channel of the secondary circuit of the cold section; fSP is the friction coefficient of the working medium in the steam-water separator; Φ BR is the full liquid phase conversion coefficient of the working fluid in the steam-water separator; ρ SP is the density of the working fluid in the steam-water separator; G SP is the flow rate of the working fluid in the steam-water separator; D SP is the hydraulic diameter of the steam-water separator; H SP is the height of the steam-water separator; ρ S,V is the density of saturated gas phase working medium in the boiling section of the secondary circuit; ρ S,L is the density of saturated liquid phase working medium in the boiling section of the secondary circuit; μ S,V is the viscosity of the saturated gas phase working medium in the boiling section of the secondary circuit; μ S,L is the density of the saturated liquid phase working medium in the boiling section of the secondary circuit;

[0158] S8: Based on the temperature, pressure and gas holdup at each position of the steam generator obtained in the above steps, the physical properties of the working fluid at each position of the steam generator at time j are calculated for use in calculations at time j+1.

[0159] In addition, the present invention also provides a device for constructing a discretized model of a nuclear power plant steam generator, which includes:

[0160] An operation data acquisition module is used to obtain the operation data of the working fluid at the primary and secondary sides of the steam generator at time j;

[0161] The descending channel model establishment module is used to establish the descending channel model based on the operating data of the secondary side inlet working fluid and the temperature, pressure, and flow rate of the primary and secondary circuit working fluids calculated by the model at time j-1, and obtain the state variables of the working fluid at the bottom outlet of the descending channel at time j;

[0162] The relevant model building module of the control body i is used to build the relevant model of the control body i according to the state variables of the working fluid at the bottom outlet of the descending channel, the calculated state variables of the control body, and the temperature, pressure, and flow rate of the primary and secondary circuit working fluids calculated by the model at time j-1;

[0163] A vaporization judgment module is used to judge whether the control body i at time j-1 has vaporized;

[0164] A saturation judgment module is used to judge whether the secondary side working medium of the control body i is saturated according to the temperature and pressure of the secondary side working medium;

[0165] A model calculation and transmission module is used to use the data obtained by the saturation judgment module, the state variables of the control body that have completed the calculation, and the output value calculated by the model at time j-1 as the input value of the model corresponding to time i+1;

[0166] Calculation judgment module, used to judge whether the control body calculation is completed;

[0167] The physical property parameter calculation module is used to calculate the physical property parameters of the working fluid at each position of the steam generator at time j based on the temperature, pressure and gas holdup at each position of the steam generator obtained by all the above modules, and use them for calculation at time j+1.

[0168] Among them, the relevant model building modules of control body i include:

[0169] The first coolant model establishment unit is used to establish a primary-circuit coolant model of the control body i and calculate the temperature, pressure and flow rate of the primary-side working fluid;

[0170] The first metal wall model establishment unit is used to establish an inverted U-shaped tube metal wall model of the control body i, and calculate the metal wall temperature and the heat transfer coefficient between the metal wall and the primary and secondary side working media;

[0171] The preheating section model building unit is used to build the preheating section model of the secondary circuit working medium of the control body i and calculate the temperature, pressure and flow rate of the secondary side working medium;

[0172] The data transmission unit is used to use the output values of the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working fluid preheating section model of the control body i as the input values of the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working fluid preheating section model of the control body i+1 respectively.

[0173] Among them, the model calculation and transmission module includes:

[0174] The second coolant model establishment unit is used to establish a primary-circuit coolant model of the control body i and calculate the temperature, pressure and flow rate of the primary-side working fluid;

[0175] The second metal wall model establishment unit is used to establish an inverted U-shaped tube metal wall model of the control body i, and calculate the metal wall temperature and the heat transfer coefficient between the metal wall and the primary and secondary side working media;

[0176] The boiling section model establishment unit is used to establish the boiling section model of the secondary circuit working medium of the control body i and calculate the temperature, pressure, flow rate and gas holdup of the secondary side working medium;

[0177] The data transmission unit uses the output values of the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working medium boiling section model of the control body i as the input values of the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working medium preheating section model of the control body i+1 respectively.

[0178] The present invention also discloses an intelligent terminal and a computer-readable storage medium. The intelligent terminal includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it is configured to execute the steps of the method for constructing a discretized model of a nuclear power plant steam generator according to the present invention. The computer-readable storage medium stores a computer program. When the processor executes the program, it is configured to execute the steps of the method for constructing a discretized model of a nuclear power plant steam generator according to the present invention.

[0179] Combined with the above detailed description of the embodiments of the present invention, it can be seen that compared with the prior art, the present invention has the following technical effects:

[0180] 1. The method for constructing a discretized model of a nuclear power steam generator provided by the present invention can obtain the precise value of the vaporization starting height of the secondary side rising channel of the steam generator, further reduce the cumulative error of the boiling section of the secondary side rising channel, and obtain a more accurate distribution of the working fluid temperature, pressure, flow rate, and gas holdup.

[0181] 2. The method for constructing a discretized model of a nuclear power steam generator provided by the present invention uses the working fluid physical parameters of the previous moment to replace the physical parameters of the current moment, which can significantly improve the simulation speed of the model.

[0182] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for constructing a discretized model of a steam generator in a nuclear power plant, characterized in that: The following steps are involved: S1. Obtain the operating data of the working fluid at the primary and secondary inlets of the steam generator at time j; S2. Based on the operating data of the working fluid at the secondary side inlet and the temperature, pressure and flow rate of the working fluid in the primary and secondary circuits calculated by the model at time j-1, a descending channel model is established to obtain the state variables of the working fluid at the bottom outlet of the descending channel at time j; S3. Establish a relevant model for control body i based on the state variables of the working fluid at the bottom outlet of the descending channel, the state variables of the control body, and the temperature, pressure, and flow rate of the working fluid in the primary and secondary circuits calculated by the model at time j-1; S4, determining whether the control body i at time j-1 has vaporized; S5. Determine whether the secondary-side working fluid is saturated based on the temperature and pressure of the secondary-side working fluid of control body i. If the control body i is saturated, define the control body i as the vaporization start control body, establish a secondary-circuit working fluid vaporization start control body model, and obtain state variables of the liquid phase and the gas-liquid mixed phase of the vaporization start control body. The state variables include the temperature, pressure, flow rate, and gas holdup of the liquid phase and the gas-liquid mixed phase of the vaporization start control body. S6. Use the data obtained in the previous step, the state variables of the control body that have been calculated, and the output value calculated by the model at time j-1 as the input value of the model corresponding to the control body i+1; S7, judging whether the control body calculation is completed; S8. Based on the temperature, pressure and gas holdup at each position of the steam generator obtained in the above steps, calculate the physical properties of the working fluid at each position of the steam generator at time j, which are used for calculation at time j+1.

2. The method for constructing a discretized model of a nuclear power plant steam generator according to claim 1, wherein: Based on the state variables of the working fluid at the bottom outlet of the descending channel, the state variables of the control body, and the temperature, pressure, and flow rate of the working fluid in the primary and secondary circuits calculated by the model at time j-1, the relevant model of the control body i is established. The calculation steps are as follows: Establish a primary coolant model for control body i and calculate the temperature, pressure and flow rate of the primary side working fluid; An inverted U-shaped tube metal wall model of the control body i is established, and the metal wall temperature and the heat transfer coefficient between the metal wall and the primary and secondary working fluids are calculated. Establish the secondary circuit working medium preheating section model of control body i and calculate the temperature, pressure and flow rate of the secondary side working medium; The output values of the primary coolant model, inverted U-shaped tube metal wall model and secondary working fluid preheating section model of control body i are respectively used as the input values of the primary coolant model, inverted U-shaped tube metal wall model and secondary working fluid preheating section model of control body i+1.

3. The method for constructing a discretized model of a steam generator in a nuclear power plant according to claim 1, wherein: Based on the temperature and pressure of the secondary working medium of control volume i, determine whether the secondary working medium here is saturated. If not, return to step 3 to calculate the primary circuit coolant model, inverted U-shaped tube metal wall model, and secondary circuit working medium preheating section model of control volume i+1. If control volume i is saturated, then control volume i is defined as the vaporization start control volume, and a secondary circuit working medium vaporization start control volume model is established to obtain the state variables of the liquid phase and the gas-liquid mixed phase of the vaporization start control volume. The state variables include: the temperature, pressure, flow rate, and gas holdup of the liquid phase and the gas-liquid mixed phase of the vaporization start control volume.

4. The method for constructing a discretized model of a steam generator in a nuclear power plant according to claim 1, wherein: Based on the data obtained in the previous step, the state variables of the control body that have been calculated, and the output value calculated by the model at time j-1, the input value of the corresponding model of the control body i+1 is calculated as follows: Establish a primary coolant model for control body i and calculate the temperature, pressure and flow rate of the primary side working fluid; An inverted U-shaped tube metal wall model of the control body i is established, and the metal wall temperature and the heat transfer coefficient between the metal wall and the primary and secondary working fluids are calculated. Establish a boiling section model of the secondary circuit working fluid of control body i and calculate the temperature, pressure, flow rate and gas holdup of the secondary side working fluid; The output values of the primary coolant model, inverted U-tube metal wall model and secondary working medium boiling section model of control body i are respectively used as the input values of the primary coolant model, inverted U-tube metal wall model and secondary working medium boiling section model of control body i+1.

5. The method for constructing a discretized model of a steam generator in a nuclear power plant according to claim 1, wherein: Determine whether the control volume calculation is completed. If the control volume calculation is not completed, return to step 6 to calculate the primary circuit coolant model, inverted U-shaped tube metal wall model, and secondary circuit working medium boiling section model of control volume i+1; If all control bodies have been calculated, the temperature, pressure, flow rate and gas holdup of the outlet working fluid of the last control body obtained in S6 are used to establish a steam-water separator model to obtain the temperature, pressure, flow rate and mass flow of the gas phase working fluid at the steam-water separator outlet.

6. A device for constructing a discretized model of a steam generator in a nuclear power plant, characterized in that: include: An operation data acquisition module is used to obtain the operation data of the working fluid at the primary and secondary sides of the steam generator at time j; The descending channel model establishment module is used to establish the descending channel model based on the operating data of the secondary side inlet working fluid and the temperature, pressure and flow rate of the primary and secondary circuit working fluids calculated by the model at time j-1, and obtain the state variables of the working fluid at the bottom outlet of the descending channel at time j; The relevant model building module of the control body i is used to build the relevant model of the control body i according to the state variables of the working fluid at the bottom outlet of the descending channel, the state variables of the control body, and the temperature, pressure and flow rate of the working fluid in the primary and secondary circuits calculated by the model at time j-1; A vaporization judgment module is used to judge whether the control body i at time j-1 has vaporized; A saturation judgment module is used to determine whether the secondary-side working medium of control body i is saturated based on the temperature and pressure of the secondary-side working medium. If control body i is saturated, control body i is defined as the vaporization start control body, a secondary circuit working medium vaporization start control body model is established, and state variables of the liquid phase and gas-liquid mixed phase of the vaporization start control body are obtained. The state variables include the temperature, pressure, flow rate, and gas holdup of the liquid phase and gas-liquid mixed phase of the vaporization start control body; A model calculation and transmission module is used to use the data obtained by the saturation judgment module, the state variables of the control body that have completed the calculation, and the output value calculated by the model at time j-1 as the input value of the model corresponding to the control body i+1; Calculation judgment module, used to judge whether the control body calculation is completed; The physical property parameter calculation module is used to calculate the physical property parameters of the working fluid at each position of the steam generator at time j based on the temperature, pressure and gas holdup at each position of the steam generator obtained by all the above modules, and use them for calculation at time j+1.

7. The apparatus for constructing a discretized model of a steam generator in a nuclear power plant according to claim 6, wherein: The relevant model building module of the control body i includes: The first coolant model establishment unit is used to establish a primary-circuit coolant model of the control body i and calculate the temperature, pressure and flow rate of the primary-side working fluid; The first metal wall model establishment unit is used to establish an inverted U-shaped tube metal wall model of the control body i, and calculate the metal wall temperature and the heat transfer coefficient between the metal wall and the primary and secondary side working media; The preheating section model building unit is used to build the preheating section model of the secondary circuit working medium of the control body i and calculate the temperature, pressure and flow rate of the secondary side working medium; The data transmission unit is used to use the output values of the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working fluid preheating section model of the control body i as the input values of the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working fluid preheating section model of the control body i+1 respectively.

8. The apparatus for constructing a discretized model of a steam generator in a nuclear power plant according to claim 6, wherein: The model calculation and transmission module includes: The second coolant model establishment unit is used to establish a primary-circuit coolant model of the control body i and calculate the temperature, pressure and flow rate of the primary-side working fluid; The second metal wall model establishment unit is used to establish an inverted U-shaped tube metal wall model of the control body i, and calculate the metal wall temperature and the heat transfer coefficient between the metal wall and the primary and secondary side working media; The boiling section model establishment unit is used to establish the boiling section model of the secondary circuit working medium of the control body i and calculate the temperature, pressure, flow rate and gas holdup of the secondary side working medium; The data transmission unit uses the output values of the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working medium boiling section model of the control body i as the input values of the primary circuit coolant model, the inverted U-shaped tube metal wall model and the secondary circuit working medium boiling section model of the control body i+1 respectively.

9. An intelligent terminal, characterized in that: The invention comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method for constructing a discretized model of a nuclear power plant steam generator is used to execute the steps of the method according to any one of claims 1 to 5.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium stores a computer program, which, when executed by a processor, is used to perform the steps of the method for constructing a discretized model of a nuclear power plant steam generator according to any one of claims 1 to 5.

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