A method for analyzing the operation characteristics of a nuclear power system steam generator full-flow field

Abstract

This invention discloses a method for analyzing the full-flow-domain operation characteristics of a steam generator in a nuclear power system. The method includes: 1. Simplifying the main heat exchange flow structure of the selected steam generator based on the calculation objectives and establishing a geometric model of the main flow domain; 2. Analyzing and simplifying the structure of the selected two-stage steam-water separator, establishing its geometric model, and combining it with the main flow domain geometric model to form a full-flow-domain geometric model of the steam generator; 3. Meshing the above-mentioned full-fluid geometric model of the steam generator; 4. Establishing a gas-liquid separation model and a resistance model for the two-stage steam-water separator; 5. Conducting full-flow-domain thermal-hydraulic calculations of the steam generator based on the established model. The accuracy of the calculation results is used to determine whether the mesh in step 3 needs to be refined until the model meets the calculation requirements. This invention provides a reference for the overall operation and maintenance of existing steam generators and the design optimization of two-stage steam-water separators.

Description

Technical Field

[0001] This invention relates to the field of three-dimensional thermal-hydraulic analysis technology for steam generators in nuclear power systems, and specifically to a method for analyzing the operational characteristics of a nuclear power steam generator covering the entire flow domain. Background Technology

[0002] The steam generator connects the primary and secondary loops of the nuclear power system. The fluid within its primary-side U-tube bundle is primary loop cooling water, responsible for safely removing fission energy from the reactor core. Feedwater on the secondary side of the steam generator is heated by the primary-side tube bundle to produce wet saturated steam. This steam is then dried by a two-stage steam-water separation unit (a rotary vane separator and a corrugated plate dryer) located at the top before being supplied to the turbine. If the steam humidity is too high, entrained droplets can cause cavitation on the turbine blades, jeopardizing turbine safety. Therefore, it is necessary to conduct operational characteristic studies using a full-range steam generator model with a two-stage steam-water separation unit.

[0003] Current research on the thermal-hydraulic numerical methods for steam generators, both domestically and internationally, primarily employs porous media methods. Typical programs include FIT-III, GENEPI, ATHOS, CUPID-SG, and STAF. These programs typically only include the flow domain primarily encompassing the secondary tube bundle region of the steam generator. The simplification of the primary flow often utilizes a one-dimensional heat source and fails to consider the subsequent drying process of the wet steam, i.e., the flow domain of the two-stage steam-water separation device. Numerical studies of two-stage steam-water separation devices mainly employ Eulerian-Lagrange and Eulerian-Eulerian methods, focusing on a single flow channel within a single rotary vane steam-water separator or a corrugated plate dryer. They investigate separation efficiency and pressure drop under different operating conditions. Fang Di et al. from Xi'an Jiaotong University established a full-scale three-dimensional numerical model of a steam-water separation device; however, its mesh size is extremely large, reaching 90 million. Furthermore, its flow domain only includes the two-stage steam-water separation device of the steam generator, leading to inaccurate inlet parameters.

[0004] In summary, there is currently no comprehensive thermal-hydraulic numerical simulation study covering the entire flow domain of a steam generator. Existing methods are insufficient to accurately simulate the distribution characteristics of thermal-hydraulic parameters covering the entire flow domain of a steam generator, as well as the steam-water separation characteristics accurate down to a single rotary vane separator or corrugated plate dryer. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a method for analyzing the full-domain operation characteristics of a steam generator in a nuclear power system. This method can perform thermal-hydraulic calculations on the entire domain of the steam generator. The present invention can provide a method for thermal-hydraulic safety analysis of existing steam generators and provide a reference for the internal optimization design of a new generation of high-efficiency steam generators.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for analyzing the full-range operational characteristics of a steam generator in a nuclear power system, comprising the following steps:

[0008] Step 1: Select the target steam generator, simplify its main flow area, and establish the corresponding geometric model;

[0009] Step 2: The top of the steam generator has a two-stage steam-water separation device, which consists of multiple vortex steam-water separators and multiple corrugated plate dryers. The flow domain of the steam-water separation device includes the vortex steam-water separator flow domain, the gravity separation section flow domain, the corrugated plate dryer flow domain, and the top cover flow domain. During the geometry establishment process, the vortex structure in the vortex steam-water separator flow domain is ignored, and a single vortex steam-water separator is directly simplified to a circular tube without vortexes. The drainage pipe structure that has no effect on the flow is ignored in the gravity separation section flow domain. The corrugated plate dryer flow domain is simplified using a porous media method. The corresponding geometry of the top cover flow domain is directly established. The geometry model established in Step 1 is spliced ​​with the vortex steam-water separator at the position to form the full flow domain geometry model of the steam generator.

[0010] Step 3: Mesh the full-flow-domain geometric model of the steam generator established in Step 2 to create a full-flow-domain mesh model of the steam generator;

[0011] Step 4: Establish gas-liquid separation model and resistance model for the two-stage steam-water separation device, and complete the simulation of the operating characteristics of the steam generator steam-water separation device;

[0012] Step 5: Perform full-basin thermal-hydraulic calculations of the steam generator based on the established full-basin grid model of the steam generator.

[0013] Preferably, step 1 specifically involves: selecting and determining a pressurized water reactor natural circulation steam generator, wherein the steam generator contains a primary side flow domain and a secondary side flow domain with independent flow; the primary side flow domain includes an inlet lower chamber flow domain, a flow domain within the U-shaped tube bundle region, and an outlet lower chamber flow domain; the secondary side flow domain includes a descending section flow domain, a flow domain outside the U-shaped tube bundle region, and a steam rising chamber flow domain; the primary side flow domain and the secondary side flow domain constitute the main flow domain of the steam generator, and a corresponding geometric model is established for the main flow domain. The flow domain within the U-shaped tube bundle region and the flow domain outside the U-shaped tube bundle region are simplified using a porous media method, requiring only the establishment of an inverted U-shaped geometry that encloses the tube bundle region. The remaining main flow domains do not require simplification using a porous media method, and a flow domain geometric model is directly established. It should be noted that the height of the descending section flow domain is based on the feedwater level of the steam generator.

[0014] Preferably, the overall mesh of the steam generator full-basin mesh model established in step 3 is mainly hexahedral mesh, with polyhedral mesh used as a transition in complex areas, to improve mesh quality and computational efficiency.

[0015] Preferably, the specific process of step 4 is as follows:

[0016] The gas-liquid separation model in the rotary vane gas-liquid separator is calculated using the empirical relationship derived by Liu et al.:

[0017]

[0018] In the formula, η swirl ρ is the separation efficiency of the rotary vane steam-water separator; μ is the fluid dynamic viscosity (Pa·s); ρ is the fluid density (kg·m³). -3 j represents the apparent velocity in m·s. -1 The subscripts l and g represent the liquid phase and gas phase, respectively.

[0019] The above fluid parameters are obtained by traversing the average fluid parameters at the inlet face of each rotary steam-water separator. After the calculation is completed, the inlet face flow rate is extracted and combined with the separation efficiency to calculate the liquid phase separation amount per unit time. This separation amount is then loaded into the grid flow domain of the rotary steam-water separator by setting a negative mass source term to achieve the separation of the liquid phase in the wet steam.

[0020] The gas-liquid separation model in the corrugated plate dryer was calculated using a computational formula developed by Wang et al.

[0021]

[0022]

[0023] In the formula, η dryer denoted as , where is the separation efficiency of the corrugated plate dryer; Stk is a dimensionless parameter characterizing the ratio of droplet inertial effect to diffusion effect; β and γ are geometric coefficients of different corrugated plates; d is the droplet diameter / m; μ is the hydrodynamic viscosity / Pa·s; and s is the characteristic dimension of the corrugated plate, i.e., the corrugated plate spacing / m.

[0024] The above fluid parameters are obtained by traversing the average fluid parameters at the inlet face of each corrugated plate dryer. After the calculation is completed, the inlet face flow rate is extracted and combined with the separation efficiency to calculate the liquid phase separation amount per unit time. This separation amount is then loaded into the grid flow domain of the corrugated plate dryer by setting a negative mass source term to achieve the separation of the liquid phase in the wet steam.

[0025] The resistance model in the rotary vane steam-water separator is calculated using the empirical relationship derived by Liu et al.:

[0026]

[0027]

[0028]

[0029] In the formula, Δp swirl The pressure drop of the rotary vane steam-water separator is given in Pa; K is the loss coefficient due to the influence of reaction pressure; and G is the wet steam mass flow density in kg·m³. -2 ;

[0030] The above fluid parameters are obtained by traversing the average fluid parameters at the inlet face of each rotary vapor separator. The calculated pressure drop is then applied to the grid domain of the rotary vapor separator by setting a momentum source term, thereby simulating the resistance of the rotary vapor separator.

[0031] The resistance model in the corrugated plate dryer is calculated using the distributed resistance method in the porous media model, based on the relationship between flow velocity and pressure drop.

[0032] Δp dryer =av+bv 2

[0033] In the formula, Δp swirl V is the pressure drop of the corrugated plate dryer (Pa); v is the inlet velocity of the corrugated plate dryer (m·s). -1 a is the coefficient of the viscous resistance term; b is the coefficient of the inertial resistance term; the above coefficients are obtained by establishing a refined local CFD model of the corrugated plate dryer and carrying out multi-condition simulation and fitting calculation results; the distributed resistance is directional, so the above resistance term coefficients need to be set along the flow direction, and the other directional coefficients are set to 1000 times the flow direction to avoid unreasonable lateral flow.

[0034] Preferably, step 5 specifically involves: performing thermal-hydraulic numerical calculations on the established full-basin grid model of the steam generator based on the computational fluid dynamics model; conducting error analysis between the obtained calculation results and the actual operating parameters of the steam generator; and successfully establishing the full-basin grid model of the steam generator when the accuracy meets the requirements. If the accuracy does not meet the requirements, return to step 2, adjust the grid, perform grid refinement operations, and then continue subsequent operations, iterating multiple times until the calculation accuracy requirements are met.

[0035] Compared with existing technologies, the present invention provides a numerical simulation method for analyzing the full-range operational characteristics of steam generators in nuclear power systems. Its overall beneficial effects are as follows:

[0036] 1) This invention can introduce the mesh of a two-stage steam-water separation device into the existing steam generator main flow domain mesh by mesh splicing method, and combine them to form a full flow domain mesh model of the steam generator, which greatly reduces the modeling workload;

[0037] 2) In establishing the geometric model of the two-stage steam-water separation device of the steam generator, the present invention simplifies the structure of the vortex blades and corrugated plates, greatly simplifies the mesh generation, reduces the number of local structures and meshes, improves the mesh quality, and is beneficial to computational stability and efficiency.

[0038] 3) The gas-liquid separation part of this invention is solved based on existing verified empirical relationships, which greatly improves the computational efficiency and makes the analysis of the full-domain operation characteristics of steam generators a reality;

[0039] 4) This invention establishes a full-scale, full-flow-domain thermal-hydraulic model of a steam generator. Compared with previous studies that were limited to the main flow domain (tube bundle) of the steam generator, this invention is the first to achieve full-flow-domain thermal-hydraulic characteristic research coverage of the steam generator.

[0040] 5) Compared with previous studies that focused on the flow domain of a single steam-water separator, the whole flow domain method of this invention can provide a high-fidelity inlet parameter distribution for each rotary steam-water separator / corrugated plate dryer. It can be used to study the steam-water separation characteristics of separators at different locations and the non-uniformity of droplet load, and guide the optimization design of steam-water separator layout.

[0041] 6) The implementation method of this invention is highly versatile and can be applied to the full-range operation characteristic analysis of existing natural circulation steam generators of various models; Attached Figure Description

[0042] Figure 1 A flowchart illustrating the technical route for establishing the full-domain analysis model of the steam generator in the nuclear power system of this invention.

[0043] Figure 2 This is a schematic diagram of the entire flow domain of the steam generator involved in the model of this invention.

[0044] The flow areas and structures marked in the attached diagram are as follows: 1-Primary side inlet lower chamber flow area, 2-Gravity separation section flow area, 3-Wave plate dryer flow area, 4-Top cover outlet structure, 5-Top cover flow area, 6-Sealing inclined plate structure, 7-Rotary vane steam-water separator flow area, 8-Steam rising chamber flow area, 9-Descending section flow area, 10-U-shaped tube bundle area flow area, 11-Primary side outlet lower chamber flow area.

[0045] Figure 3 This is a schematic diagram of the mesh generation for the full-domain model of the steam generator of the present invention.

[0046] Figure 4 In the middle (a) and (b), respectively, the trace diagrams of the primary and secondary side flow fields obtained from the calculation of the full flow domain model of the steam generator of the present invention are shown. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are only for explaining the invention and are not intended to limit the invention. Figure 1 The flowchart shown illustrates the technical route of this invention, using a typical steam generator structure as an example for further detailed description.

[0048] Step 1: Select the target steam generator (taking AP1000 as an example), simplify its main flow area, and establish the corresponding geometric model:

[0049] A pressurized water reactor natural circulation steam generator is selected and defined, which includes a primary side flow domain and a secondary side flow domain with independent flow. The primary side flow domain includes the inlet lower chamber flow domain, the flow domain inside the U-shaped tube bundle region, and the outlet lower chamber flow domain. The secondary side flow domain includes the descending section flow domain, the flow domain outside the U-shaped tube bundle region, and the steam rising chamber flow domain. The above flow domains are the main flow domains of the steam generator. A corresponding geometric model is established for the main flow domains. The flow domain inside and outside the U-shaped tube bundle region is simplified using the porous media method. Only an inverted U-shaped geometry enclosing the tube bundle region needs to be established. The other main flow domains do not need to be simplified using the porous media method. The flow domain geometric model is directly established. It should be noted that the height of the descending section flow domain is the height of the steam generator feedwater level.

[0050] Step 2: The steam generator has a two-stage steam-water separation device at the top, consisting of 33 rotary vane steam-water separators and 8 corrugated plate dryers. The flow domain of the steam-water separation device includes the rotary vane steam-water separator flow domain, the gravity separation section flow domain, the corrugated plate dryer flow domain, and the top cover flow domain. During the geometry establishment process, the vane structure in the rotary vane steam-water separator flow domain is ignored; a single rotary vane steam-water separator is directly simplified to a vaneless circular tube (the vane structure has little impact on the subsequent corrugated plate dryer inlet flow distribution and can be ignored). The drainage pipe structure, which has no impact on the flow, is ignored in the gravity separation section flow domain. The corrugated plate dryer flow domain is simplified using a porous media method. The corresponding geometry for the top cover flow domain is directly established. The geometry model established in Step 1 is spliced ​​with the one established in Step 1 at the rotary vane steam-water separator location to form the overall flow domain geometry model of the steam generator. The overall flow domain is as follows: Figure 2As shown, the secondary side fluid enters from the descending section 9, flows downward and enters the U-shaped tube bundle region 10 (outside the tube). The fluid is then heated, boiled, and vaporized as it flows upward along the tube bundle region. It then flows from the steam rising chamber into the vortex steam-water separator region 7, where primary gas-liquid separation is completed. It then flows into the gravity separation section 2, and is guided by the sealing inclined plate structure 6 into the corrugated plate dryer region 3, where further gas-liquid separation is completed. Finally, it flows out from the top cover region 5 through the top cover outlet structure 4. The primary side fluid enters from the primary side inlet lower chamber 1, flows upward into the U-shaped tube bundle region 10 (inside the tube), where heat exchange with the external region is completed. Finally, it flows out through the primary side outlet lower chamber 11.

[0051] Step 3: Mesh the geometric model established in Step 2 to create a mesh model of the entire steam generator flow domain. The overall mesh is mainly hexahedral, with polyhedral meshes used as a transition in complex areas to improve mesh quality and computational efficiency. Figure 3 The grid model is shown, which covers the entire flow domain of the primary and secondary sides of the steam generator. The tube bundle region grid is an overlapping grid, which includes both the primary and secondary tube bundle regions. In the steam-water separation device, the vortex steam-water separator ignores the vortex structure and is directly simplified to a vortex-free circular tube grid. The gravity separation section does not establish a drainage pipe structure. The corrugated plate dryer region is established as a porous media method grid.

[0052] Step 4: Establish the gas-liquid separation model and resistance model for the two-stage gas-liquid separator:

[0053] The gas-liquid separation model in the rotary vane gas-liquid separator is calculated using the empirical relationship derived by Liu et al.:

[0054]

[0055] In the formula, η swirl ρ is the separation efficiency of the rotary vane steam-water separator; μ is the fluid dynamic viscosity (Pa·s); ρ is the fluid density (kg·m³). -3 j represents the apparent velocity in m·s. -1 The subscripts l and g represent the liquid phase and gas phase, respectively.

[0056] The above fluid parameters are obtained by traversing the average fluid parameters at the inlet face of each rotary steam-water separator. After the calculation is completed, the inlet face flow rate is extracted and combined with the separation efficiency to calculate the liquid phase separation amount per unit time. This separation amount is then loaded into the grid flow domain of the rotary steam-water separator by setting a negative mass source term to achieve the separation of the liquid phase in the wet steam.

[0057] The gas-liquid separation model in the corrugated plate dryer was calculated using a computational formula developed by Wang et al.

[0058]

[0059]

[0060] In the formula, η dryer denoted as , where is the separation efficiency of the corrugated plate dryer; Stk is a dimensionless parameter characterizing the ratio of droplet inertial action to diffusion effect; β and γ are geometric structure coefficients for different corrugated plates, selected with reference to the fitting results of Wang et al. (the AP1000 evaporator uses STPV type corrugated plates, β = -33.582, γ = 0.986); d is the droplet diameter / m; μ is the hydrodynamic viscosity / Pa·s; s is the characteristic dimension of the corrugated plate, i.e., the corrugated plate spacing / m.

[0061] The above fluid parameters are obtained by traversing the average fluid parameters at the inlet face of each corrugated plate dryer. After the calculation is completed, the inlet face flow rate is extracted and combined with the separation efficiency to calculate the liquid phase separation amount per unit time. This separation amount is then loaded into the grid flow domain of the corrugated plate dryer by setting a negative mass source term to achieve the separation of the liquid phase in the wet steam.

[0062] The resistance model in the rotary vane steam-water separator is calculated using the empirical relationship derived by Liu et al.:

[0063]

[0064]

[0065]

[0066] In the formula, Δp swirl The pressure drop of the rotary vane steam-water separator is given in Pa; K is the loss coefficient due to the influence of reaction pressure; and G is the wet steam mass flow density in kg·m³. -2 ;

[0067] The above fluid parameters are obtained by traversing the average fluid parameters at the inlet face of each rotary vapor separator. The calculated pressure drop is then applied to the grid domain of the rotary vapor separator by setting a momentum source term, thereby simulating the resistance of the rotary vapor separator.

[0068] The resistance model in the rotary vane steam-water separator is calculated using the empirical relationship derived by Liu et al.:

[0069]

[0070]

[0071]

[0072] In the formula, Δp swirlThe pressure drop of the rotary vane steam-water separator is given in Pa; K is the loss coefficient due to the influence of reaction pressure; and G is the wet steam mass flow density in kg·m³. -2 ;

[0073] The above fluid parameters are obtained by traversing the average fluid parameters at the inlet face of each rotary vapor separator. The calculated pressure drop is then applied to the grid domain of the rotary vapor separator by setting a momentum source term, thereby simulating the resistance of the rotary vapor separator.

[0074] The resistance model in the corrugated plate dryer is calculated using the distributed resistance method in the porous media model, based on the relationship between flow velocity and pressure drop.

[0075] Δp dryer =av+bv 2

[0076] In the formula, Δp swirl V is the pressure drop of the corrugated plate dryer (Pa); v is the inlet velocity of the corrugated plate dryer (m·s). -1 ; a is the coefficient of the viscous drag term; b is the coefficient of the inertial drag term; the above coefficients were obtained by establishing a refined local CFD model of the corrugated plate dryer and conducting multi-condition simulations, and the fitting calculation results were (a = 3.88 × 10). 3 (b = 100.47); The above distributed resistance is directional, so the resistance coefficients should be set along the flow direction, and the other directional coefficients should be set to 1000 times the flow direction to avoid unreasonable lateral flow.

[0077] The above introduces a two-stage steam-water separation device gas-liquid separation model and a resistance model into the full-domain model of the steam generator, which can simulate the operating characteristics of the steam-water separation device of the steam generator;

[0078] Step 5: Based on the model established above, perform full-range thermal-hydraulic calculations for the steam generator:

[0079] For the established full-basin grid model of the steam generator, thermal-hydraulic numerical calculations are performed based on the computational fluid dynamics model. Error analysis is conducted between the calculated results and the operating parameters of the AP1000 steam generator. If the accuracy meets the requirements, the full-basin grid model of the steam generator is successfully established. If the accuracy does not meet the requirements, return to step 2 to adjust the grid and perform grid refinement. Then continue with subsequent operations, iterating multiple times until the required computational accuracy is met. Figure 4Figures (a) and (b) show the flow field traces of the primary and secondary flow domains of the steam generator calculated by the present invention. As can be seen from the figures, the flow field calculated by the method of the present invention achieves full coverage of the secondary flow domain (main flow domain of the tube bundle area and flow domain of the steam-water separator) and the primary flow domain (flow domain of the tube bundle area and inlet and outlet chambers) of the steam generator. The flow domain of the steam-water separator can be post-processed to obtain parameters such as the gas-liquid separation efficiency and load non-uniformity of the single-blade steam-water separator and the corrugated plate dryer for evaluating the performance of the separator.

[0080] This invention enables thermal-hydraulic calculations across the entire flow domain of a steam generator, covering the primary side inlet and outlet chambers, tube sheet and U-tube bundle (inside the tubes), secondary side descending section, U-tube bundle (outside the tubes), steam rising section, vortex steam-water separator, gravity separation section, corrugated plate dryer, and top cover. It can be used to study key performance characteristics of nuclear power system steam generators under different operating conditions, such as flow heat transfer, two-phase boiling, flow resistance, steam-water separation, load unevenness, and steam dryness. The introduction of a two-stage steam-water separation device allows for comparative studies, examining the effects of different arrangements of the vortex steam-water separator and the corrugated plate dryer (two-stage steam-water separation device) on improving steam-water separation efficiency and smoothing out dryer load unevenness, thereby improving steam quality, increasing turbine efficiency, and ultimately enhancing the economic benefits of nuclear power. In summary, this invention can provide a reference for the internal optimization design of next-generation high-efficiency steam generators.

[0081] The above description is only one specific embodiment of the present invention and does not limit the scope of protection of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of protection of the present invention.

Claims

1. A method for analyzing the full-domain operation characteristics of a steam generator in a nuclear power system, characterized in that: The steps are as follows: Step 1: Select the target steam generator, simplify its main flow area, and establish the corresponding geometric model; Step 2: The top of the steam generator has a two-stage steam-water separation device, which consists of multiple vortex steam-water separators and multiple corrugated plate dryers. The flow domain of the steam-water separation device includes the vortex steam-water separator flow domain, the gravity separation section flow domain, the corrugated plate dryer flow domain, and the top cover flow domain. During the geometry establishment process, the vortex structure in the vortex steam-water separator flow domain is ignored, and a single vortex steam-water separator is directly simplified to a circular tube without vortexes. The drainage pipe structure that has no effect on the flow is ignored in the gravity separation section flow domain. The corrugated plate dryer flow domain is simplified using a porous media method. The corresponding geometry of the top cover flow domain is directly established. The geometry model established in Step 1 is spliced ​​with the vortex steam-water separator at the position to form the full flow domain geometry model of the steam generator. Step 3: Mesh the full-flow-domain geometric model of the steam generator established in Step 2 to create a full-flow-domain mesh model of the steam generator; Step 4: Establish gas-liquid separation model and resistance model for the two-stage steam-water separation device, and complete the simulation of the operating characteristics of the steam generator steam-water separation device; Step 5: Perform full-basin thermal-hydraulic calculations of the steam generator based on the established full-basin grid model of the steam generator; Step 1 specifically involves selecting and defining a pressurized water reactor natural circulation steam generator. The steam generator contains a primary side flow domain and a secondary side flow domain with independent flow. The primary side flow domain includes the inlet lower chamber flow domain, the flow domain inside the U-shaped tube bundle region, and the outlet lower chamber flow domain. The secondary side flow domain includes the descending section flow domain, the flow domain outside the U-shaped tube bundle region, and the steam rising chamber flow domain. The primary side flow domain and the secondary side flow domain constitute the main flow domain of the steam generator. A corresponding geometric model is established for the main flow domain. The flow domain inside and outside the U-shaped tube bundle region is simplified using a porous media method, requiring only the establishment of an inverted U-shaped geometry that encloses the tube bundle region. The remaining main flow domains do not require simplification using the porous media method; a flow domain geometric model is directly established. Note that the height of the descending section flow domain should be based on the steam generator feedwater level.

2. The method for analyzing the full-domain operation characteristics of a steam generator in a nuclear power system according to claim 1, characterized in that: The overall mesh of the steam generator full-basin mesh model established in step 3 is mainly hexahedral mesh, with polyhedral mesh used as a transition in complex areas to improve mesh quality and computational efficiency.

3. The method for analyzing the full-domain operation characteristics of a steam generator in a nuclear power system according to claim 1, characterized in that: The specific process of step 4 is as follows: The gas-liquid separation model in a rotary vane gas-liquid separator is calculated using the following formula: In the formula, The separation efficiency of the rotary vane steam-water separator; For fluid dynamic viscosity / ; fluid density / ; Apparent flow rate / subscript and These represent the liquid phase and the gas phase, respectively. The above fluid parameters are obtained by traversing the average fluid parameters at the inlet face of each rotary steam-water separator. After the calculation is completed, the inlet face flow rate is extracted and combined with the separation efficiency to calculate the liquid phase separation amount per unit time. This separation amount is then loaded into the grid flow domain of the rotary steam-water separator by setting a negative mass source term to achieve the separation of the liquid phase in the wet steam. The gas-liquid separation model in the corrugated plate dryer is calculated using the following formula: In the formula, For the separation efficiency of the corrugated plate dryer; A dimensionless parameter characterizing the ratio of droplet inertial action to diffusion action; and These are the geometric coefficients for different waveform boards; droplet diameter / ; For fluid dynamic viscosity / ; The characteristic dimension of the corrugated board, i.e., the spacing between the corrugated boards / ; The above fluid parameters are obtained by traversing the average fluid parameters at the inlet face of each corrugated plate dryer. After the calculation is completed, the inlet face flow rate is extracted and combined with the separation efficiency to calculate the liquid phase separation amount per unit time. This separation amount is then loaded into the grid flow domain of the corrugated plate dryer by setting a negative mass source term to achieve the separation of the liquid phase in the wet steam. The resistance model in a rotary vane steam-water separator is calculated using the following formula: In the formula, Pressure drop of the rotary vane steam-water separator / ; This represents the loss coefficient due to the influence of reaction pressure. wet steam mass flow rate / ; The above fluid parameters are obtained by traversing the average fluid parameters at the inlet face of each rotary vapor separator. The calculated pressure drop is then applied to the grid domain of the rotary vapor separator by setting a momentum source term, thereby simulating the resistance of the rotary vapor separator. The resistance model in the corrugated plate dryer is calculated using the distributed resistance method in the porous media model, based on the relationship between flow velocity and pressure drop. In the formula, Pressure drop of the corrugated plate dryer / ; The inlet flow rate of the corrugated plate dryer / ; This is the coefficient for the viscous resistance term; For the coefficient of the inertial drag term; The above coefficients were obtained by establishing a refined local CFD model of the corrugated plate dryer and conducting multi-condition simulations, and fitting the calculation results. The distributed resistance is directional, so the above resistance coefficients need to be set along the flow direction, and the coefficients of other directions are set to 1000 times the flow direction to avoid unreasonable lateral flow.

4. The method for analyzing the full-domain operation characteristics of a steam generator in a nuclear power system according to claim 1, characterized in that: Step 5 specifically involves: performing thermal-hydraulic numerical calculations on the established full-basin grid model of the steam generator based on the computational fluid dynamics model, and conducting error analysis between the obtained calculation results and the actual operating parameters of the steam generator. If the accuracy meets the requirements, the full-basin grid model of the steam generator is successfully established. If the accuracy does not meet the requirements, return to step 2, adjust the grid, perform grid refinement, and then continue the subsequent operations, iterating multiple times until the calculation accuracy requirements are met.

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