Cross-dimensional coupling method for steam generator and passive residual heat removal system on secondary side

Abstract

The present invention discloses a cross-dimensional coupling method for a steam generator and a secondary-side passive residual heat removal system, and the steps are as follows: 1. Model the steam generator by using three-dimensional computational fluid dynamics software; 2. Initialize the secondary-side passive residual heat removal system by using one-dimensional dynamic simulation program; 3. Calculate the flow and heat transfer process in the steam generator by using three-dimensional computational fluid dynamics software; 4. Calculate the flow rate and heat transfer amount of the secondary-side passive residual heat removal system by using one-dimensional dynamic simulation program; 5. Update the mass and energy changes of the steam-water mixture in the steam generator; 6. Repeat steps (3) to (5) until the specified calculation time is reached. The method of the present invention can quickly and accurately calculate the natural circulation heat transfer process of the secondary-side passive residual heat removal system and its influence on the flow and heat transfer process in the steam generator, which is of great significance for the accident transient analysis of pressurized water reactors.

Description

Technical Field

[0001] The present invention belongs to the field of calculation of nuclear reactor accident processes, and particularly relates to a cross-dimensional coupling method for a steam generator and a passive residual heat removal system on the secondary side. Background Art

[0002] In advanced nuclear power plants such as "Hualong One" in China, a passive residual heat removal system is installed on the secondary side of the steam generator to remove the heat of the steam generator during an accident, thereby reducing the temperature of the coolant in the main system of the nuclear power plant and preventing the core from being exposed and melted. The passive residual heat removal system on the secondary side mainly includes a heat exchange water tank, a heat exchanger, and a flow pipeline connecting the steam generator.

[0003] The method of analyzing the steam generator using three-dimensional computational fluid dynamics software has been relatively mature. However, the geometry of the passive residual heat removal system on the secondary side is relatively complex and the pipes are relatively thin, making it difficult to use three-dimensional computational fluid dynamics software for modeling. Moreover, when the three-dimensional computational fluid dynamics software calculates the condensation process in the narrow pipes of the passive residual heat removal system on the secondary side, it is prone to divergence and it is difficult to calculate the accurate flow rate. Therefore, currently, a one-dimensional dynamic simulation program PRHRSDSC is generally used to analyze and calculate the passive residual heat removal system on the secondary side.

[0004] However, there is currently no good method to comprehensively calculate the thermal-hydraulic behavior of the steam generator and the natural circulation behavior of the passive residual heat removal system on the secondary side. Summary of the Invention

[0005] To fill the gaps in the above-mentioned existing technologies, the present invention provides a cross-dimensional coupling method for a steam generator and a passive residual heat removal system on the secondary side, which can quickly and accurately calculate the natural circulation heat transfer process of the passive residual heat removal system on the secondary side and its influence on the thermal-hydraulic characteristics of the steam generator, and is of great significance for the transient analysis of pressurized water reactor accidents.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A cross-dimensional coupling method for a steam generator and a passive residual heat removal system on the secondary side, comprising the following steps:

[0008] Step 1: Model the steam generator using three-dimensional computational fluid dynamics software, specifically including the following content:

[0009] 1) Establish the secondary side chamber of the steam generator and set the chamber liquid level, water temperature, gas temperature, and pressure;

[0010] 2) Establish the U-shaped heat exchanger area of the steam generator by the porous medium method and set the volume heat source;

[0011] 3) Establish two end faces at the inlet and outlet of the secondary-side passive residual heat removal system, and set them as the steam outflow boundary condition and the water inflow boundary condition respectively;

[0012] Step 2: Use the one-dimensional dynamic simulation program PRHRSDSC to model the secondary-side passive residual heat removal system, which specifically includes the following contents:

[0013] 1) Establish the inlet section and outlet section of the secondary-side passive residual heat removal system, and define the diameter, length, and pipe direction of each pipeline;

[0014] 2) Establish a heat exchange water pool and determine the water level and water temperature of the heat exchange water pool;

[0015] 3) Establish a heat exchanger and determine the heat transfer area, flow area, and length of the heat exchanger;

[0016] Step 3: Use the three-dimensional computational fluid dynamics software to calculate the flow heat transfer and evaporation process in the steam generator, and specifically obtain the following parameters: the gas temperature distribution, gas velocity distribution, and water temperature distribution in the steam generator, and simultaneously obtain the pressure and gas temperature at the inlet of the secondary-side passive residual heat removal system;

[0017] Step 4: Use the one-dimensional dynamic simulation program PRHRSDSC to calculate the flow rate and heat transfer amount of the secondary-side passive residual heat removal system, which specifically includes the following contents:

[0018] 1) Calculate the specific heat capacity and viscosity of the fluid at the inlet of the secondary-side passive residual heat removal system based on the pressure and gas temperature at the inlet of the secondary-side passive residual heat removal system;

[0019] 2) Calculate the flow rate, heat transfer amount, and outlet temperature of the secondary-side passive residual heat removal system based on the specific heat capacity and viscosity of the fluid at the inlet of the secondary-side passive residual heat removal system, the gas temperature at the inlet of the secondary-side passive residual heat removal system, the water level and water temperature of the heat exchange water pool, the diameter, length, and pipe direction of the inlet section and outlet section, and the heat transfer area, flow area, and length of the heat exchanger;

[0020] 3) Update the water level and water temperature of the heat exchange water pool based on the heat transfer amount of the secondary-side passive residual heat removal system;

[0021] Step 5: Update the mass and temperature change of the steam-water mixture in the steam generator:

[0022] 1) Set the steam outflow boundary condition at the inlet of the secondary-side passive residual heat removal system in the steam generator, and the flow rate is the flow rate of the secondary-side passive residual heat removal system;

[0023] 2) Set the water inflow boundary condition at the outlet of the passive residual heat removal system on the secondary side in the steam generator. The flow rate is the flow rate of the passive residual heat removal system on the secondary side, and the temperature is the outlet temperature of the passive residual heat removal system on the secondary side;

[0024] 3) The three-dimensional computational fluid dynamics software updates the mass distribution, mass flow velocity distribution, and temperature distribution of the steam-water mixture in the steam generator according to the steam outflow boundary condition, water inflow boundary condition, and the volume heat source in the U-shaped heat exchanger area of the steam generator;

[0025] Step 6: Repeat Step 3 to Step 5 until the specified calculation time is reached.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. Use the coupled calculation of a one-dimensional dynamic simulation program and a three-dimensional computational fluid dynamics software. The one-dimensional dynamic simulation program is used to calculate the thermal-hydraulic behavior of the passive residual heat removal system on the secondary side with complex geometry and intense phase change, which has the advantages of fast calculation speed and low demand for calculation resources. For the thermal-hydraulic behavior in the steam generator, the three-dimensional computational fluid dynamics software is used for three-dimensional calculation, with high accuracy, and the mass, temperature, and velocity distributions of the steam-water mixture in a large space can be obtained, providing accurate inlet boundary conditions for the one-dimensional dynamic simulation program;

[0028] 2. It can simulate the operating state of the passive residual heat removal system on the secondary side, including the inflow of gas in the steam generator into the passive residual heat removal system on the secondary side, the flow and phase change of steam in the passive residual heat removal system on the secondary side, and the heating and evaporation of the heat exchange pool, etc.;

[0029] 3. It can calculate the cooling effect of the passive residual heat removal system on the secondary side on the coolant in the steam generator under accident conditions.

[0030] 4. The method of the present invention can perform coupled calculations on the thermal-hydraulic behavior in the steam generator during an accident, the operation process of the passive residual heat removal system on the secondary side, and the interaction process between the steam generator and the passive residual heat removal system on the secondary side;

[0031] 5. The three-dimensional computational fluid dynamics software and the one-dimensional dynamic simulation program are relatively independent and can be calculated separately, which is easy for the further development of the later coupling program. Brief Description of the Drawings

[0032] Figure 1 It is a schematic diagram for modeling the steam generator and the passive residual heat removal system on the secondary side.

[0033] Figure 2 It is a flow chart for the cross-dimensional coupled calculation of the steam generator and the passive residual heat removal system on the secondary side. Detailed implementation manners

[0034] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0035] Figure 1 It is a schematic diagram for modeling a steam generator and a passive residual heat removal system on the secondary side. A one-dimensional dynamic simulation program PRHRSDSC is used to simulate the passive residual heat removal system on the secondary side, and a three-dimensional computational fluid dynamics software CFX is used to simulate the thermal-hydraulic behavior in the steam generator. The thermal-hydraulic parameters of the steam generator obtained by the three-dimensional computational fluid dynamics software CFX provide boundary conditions for the one-dimensional dynamic simulation program PRHRSDSC, and the thermal-hydraulic parameters of the passive residual heat removal system on the secondary side obtained by the one-dimensional dynamic simulation program PRHRSDSC are also fed back to the three-dimensional computational fluid dynamics software CFX as computational boundary conditions.

[0036] As Figure 2 shown, the cross-dimensional coupling method for the steam generator and the passive residual heat removal system on the secondary side of the present invention includes the following steps:

[0037] Step 1: Use the three-dimensional computational fluid dynamics software to model the steam generator in Figure 1 , specifically including the following contents:

[0038] 1) Establish the secondary side chamber of the steam generator, and set the initial liquid level, water temperature, gas temperature and pressure of the chamber;

[0039] 2) Establish the U-shaped heat exchanger area of the steam generator by the porous medium method, and set the volume heat source of the U-shaped heat exchanger area;

[0040] 3) Establish the inlet end face and outlet end face of the passive residual heat removal system on the secondary side in the steam generator, set the inlet end face as the steam outflow boundary condition, and set the outlet end face as the water inflow boundary condition;

[0041] Step 2: Use the one-dimensional dynamic simulation program PRHRSDSC to model the passive residual heat removal system on the secondary side in Figure 1 , specifically including the following contents:

[0042] 1) Establish the inlet section and outlet section of the passive residual heat removal system on the secondary side, and define the diameter, length and pipe direction of each pipeline;

[0043] 2) Establish a heat exchange water pool, and determine the water level and water temperature of the heat exchange water pool;

[0044] 3) Establish a heat exchanger, and determine the heat exchange area, flow area and length of the heat exchanger;

[0045] Step 3: Use the three-dimensional computational fluid dynamics software to calculate Figure 1The flow heat transfer and evaporation process in the intermediate steam generator, and specifically obtain the following parameters: the gas temperature distribution, gas velocity distribution, and water temperature distribution in the steam generator. At the same time, the pressure and gas temperature at the inlet end face of the passive residual heat removal system on the secondary side can be obtained;

[0046] Step 4: Use the one-dimensional dynamic simulation program PRHRSDSC to calculate Figure 1 the flow rate and heat transfer amount of the passive residual heat removal system on the secondary side, specifically including the following content:

[0047] 1) Calculate the specific heat capacity and viscosity of the fluid at the inlet of the passive residual heat removal system on the secondary side based on the steam pressure and steam temperature at the inlet of the passive residual heat removal system on the secondary side;

[0048] 2) Calculate the flow rate, heat transfer amount and outlet temperature of the passive residual heat removal system on the secondary side based on the specific heat capacity and viscosity of the fluid at the inlet of the passive residual heat removal system on the secondary side, the steam temperature at the inlet of the passive residual heat removal system on the secondary side, the water level and water temperature of the heat exchange pool, the diameters, lengths, pipe directions of the inlet and outlet sections, the heat transfer area, flow area and length of the heat exchanger;

[0049] 3) Update the water level and water temperature of the heat exchange pool based on the heat transfer amount from the heat exchanger of the passive residual heat removal system on the secondary side to the pool;

[0050] Step 5: Update Figure 1 the mass and temperature changes of the steam-water mixture in the intermediate steam generator:

[0051] 1) Set a steam outflow boundary condition at the inlet of the passive residual heat removal system on the secondary side in the steam generator, and the flow rate is the flow rate of the passive residual heat removal system on the secondary side;

[0052] 2) Set a water inflow boundary condition at the outlet of the passive residual heat removal system on the secondary side in the steam generator, the flow rate is the flow rate of the passive residual heat removal system on the secondary side, and the temperature is the outlet temperature of the passive residual heat removal system on the secondary side;

[0053] 3) The three-dimensional computational fluid dynamics software updates the mass distribution, mass flow velocity distribution and temperature distribution of the steam-water mixture in the steam generator according to the steam outflow boundary condition at the inlet of the passive residual heat removal system on the secondary side at the top of the steam generator, the water inflow boundary condition at the outlet of the passive residual heat removal system on the secondary side at the upper part of the steam generator, and the volume heat source in the U-shaped heat exchanger area of the steam generator;

[0054] Step 6: Repeat steps 3 to 5 until the specified calculation time is reached.

[0055] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited thereto. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as falling within the scope of patent protection determined by the claims submitted for the present invention.

Claims

1. A cross - dimensional coupling method for a steam generator and a passive residual heat removal system on the secondary side, Characterized in that: It includes the following steps: Step 1: Model the steam generator using three - dimensional computational fluid dynamics software, specifically including the following: 1) Establish the secondary side chamber of the steam generator and set the chamber liquid level, water temperature, gas temperature and pressure; 2) Establish the U - type heat exchanger area of the steam generator using the porous medium method and set the volume heat source; 3) Establish two end faces at the inlet and outlet of the passive residual heat removal system on the secondary side, and set them as the steam outflow boundary condition and the water inflow boundary condition respectively; Step 2: Model the passive residual heat removal system on the secondary side using a one - dimensional dynamic simulation program, specifically including the following: 1) Establish the inlet section and outlet section of the passive residual heat removal system on the secondary side, and define the diameter, length and pipe direction of each pipeline; 2) Establish the heat exchange water pool and determine the water level and water temperature of the heat exchange water pool; 3) Establish the heat exchanger and determine the heat transfer area, flow area and length of the heat exchanger; Step 3: Use the three - dimensional computational fluid dynamics software to calculate the flow, heat transfer and evaporation process in the steam generator, and specifically obtain the following parameters: the gas temperature distribution, gas velocity distribution, water temperature distribution in the steam generator, and at the same time obtain the pressure and gas temperature at the inlet of the passive residual heat removal system on the secondary side; Step 4: Use the one - dimensional dynamic simulation program to calculate the flow rate and heat transfer amount of the passive residual heat removal system on the secondary side, specifically including the following: 1) Calculate the specific heat capacity and viscosity of the fluid at the inlet of the passive residual heat removal system on the secondary side based on the pressure and gas temperature at the inlet of the passive residual heat removal system on the secondary side; 2) Calculate the flow rate, heat transfer amount and outlet temperature of the passive residual heat removal system on the secondary side based on the specific heat capacity and viscosity of the fluid at the inlet of the passive residual heat removal system on the secondary side, the gas temperature at the inlet of the passive residual heat removal system on the secondary side, the water level and water temperature of the heat exchange water pool, the diameter, length and pipe direction of the inlet section and outlet section, and the heat transfer area, flow area and length of the heat exchanger; 3) Update the water level and water temperature of the heat exchange water pool based on the heat transfer amount of the passive residual heat removal system on the secondary side; Step 5: Update the mass and temperature change of the steam - water mixture in the steam generator: 1) Set the steam outflow boundary condition at the inlet of the passive residual heat removal system on the secondary side in the steam generator, and the flow rate is the flow rate of the passive residual heat removal system on the secondary side; 2) Set the water inflow boundary condition at the outlet of the passive residual heat removal system on the secondary side in the steam generator, the flow rate is the flow rate of the passive residual heat removal system on the secondary side, and the temperature is the outlet temperature of the passive residual heat removal system on the secondary side; 3) The three - dimensional computational fluid dynamics software updates the mass distribution of the steam - water mixture, the mass flow velocity distribution of the steam - water mixture and the temperature distribution of the steam - water mixture in the steam generator according to the steam outflow boundary condition, the water inflow boundary condition and the volume heat source of the U - type heat exchanger area of the steam generator; Step 6: Repeat Step 3 to Step 5 until the specified calculation time is reached.

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