Full-size shell-and-tube heat exchanger service performance analysis and calculation method based on sub-domain solution and cross-dimension coupling

Abstract

The invention discloses a full-size shell-and-tube heat exchanger service performance analysis and calculation method based on domain solving and cross-dimension coupling, and aims to solve the problem that the number of calculation resources needed by full-three-dimensional modeling numerical simulation of a shell-and-tube heat exchanger is large. Through key technologies of one-dimensional tube pass fluid calculation, full-size shell pass fluid porous medium fluid calculation, shell-and-tube heat exchanger thermodynamic calculation and data mapping, a multi-physics field cooperative calculation framework is constructed by applying domain solving and cross-dimension coupling, and the calculation complexity is remarkably reduced while the precision is guaranteed; flow heat transfer characteristics and mechanical characteristics of the shell-and-tube heat exchanger are analyzed. The method comprises the following steps: 1, setting shell-and-tube heat exchanger tube pass fluid; 2, setting shell pass fluid of the full-size shell-and-tube heat exchanger; 3, tube pass fluid and shell pass fluid are coupled; 4, bidirectional flow heat exchange coupling calculation; 5, bidirectional flow heat exchange coupling calculation; 6, thermal-mechanical coupling calculation of the heat transfer pipe; 7, quickly calculating and analyzing the service performance of the shell-and-tube heat exchanger; and 8, analyzing the mechanical properties of the shell-and-tube heat exchanger under the service condition.

Description

Technical Field

[0001] This invention belongs to the technical field of service performance analysis of shell-and-tube heat exchangers, specifically involving a calculation method for service performance analysis of full-size shell-and-tube heat exchangers based on domain-specific solution and cross-dimensional coupling. Background Technology

[0002] Heat exchangers are crucial heat exchange devices in nuclear power plants, but they are also the weakest link in the entire system. More than half of nuclear power plant shutdown accidents are caused by heat exchanger failure, severely impacting the safety and reliability of the entire plant. Therefore, there is an urgent need to establish a multiphysics coupled computational analysis technique for full-scale flow heat transfer and structural mechanics to achieve full-lifecycle performance evaluation of small heat exchangers under complex operating conditions.

[0003] In existing numerical simulations of shell-and-tube heat exchangers, common methods include the distributed parameter method and the three-dimensional numerical simulation method. The distributed parameter method divides the heat exchanger into multiple micro-element control volumes, calculates the temperature, pressure, and other parameter changes of the fluid in the shell and tube sides within each micro-element, and uses correlations derived from experiments, such as the Bell-Davis method or flow path analysis, to estimate the heat transfer and pressure drop characteristics of the shell side. Its accuracy heavily depends on the applicability of the selected correlations, most of which are derived from specific structures and operating conditions. When the heat exchanger structure is complex, or there are irregular baffles or multiple flows, the predictive accuracy of empirical correlations will decrease significantly. The three-dimensional numerical simulation method can reproduce the complex flow state of the shell-side fluid in detail by solving the governing equations of mass, momentum and energy conservation, and show the effects of vortices, bypass flow and leakage flow near the baffles, thereby more accurately predicting the local heat transfer coefficient and pressure drop distribution. Although this method can provide rich information on the local flow field and temperature field, and reveal flow dead zones or hot spots that are difficult to find by traditional methods, its computational cost is very high and it is extremely sensitive to the selection of mesh quality and turbulence model. In practical engineering applications, especially for large heat exchangers or when multi-condition optimization design is required, the huge demand for computing resources and the long calculation cycle are the main bottlenecks it faces.

[0004] Although numerical simulation of traditional shell-and-tube heat exchangers has become a typical method, existing distributed parameter methods struggle to characterize the effects of complex flow structures and baffles, and three-dimensional numerical simulations require significant computational resources. This limitation means that current simulation methods lack a balance between rapid computation and accuracy when dealing with irregularly shaped baffles, multi-flow systems, or novel support configurations, hindering the rapid design and evaluation of shell-and-tube heat exchangers. Therefore, there is an urgent need to develop an integrated analysis method encompassing geometric modeling, fluid simulation, data mapping, coupled solution, and performance analysis. 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 service performance of full-size shell-and-tube heat exchangers based on domain-based solution and cross-dimensional coupling, constructing a complete technical chain of "geometric modeling - fluid simulation - data mapping - coupled solution - performance analysis". By simplifying the fluid inside the three-dimensional heat transfer tube into a one-dimensional channel and using a porous medium model to characterize the external region, the computational scale is significantly reduced. Domain-based coupling and data mapping techniques are used to achieve bidirectional data exchange between the fluid inside and outside the tube at the flow and heat transfer levels. The temperature, pressure, and heat transfer coefficient obtained from fluid calculations are accurately mapped to the solid model of the heat transfer tube while maintaining its original design position. Structural static analysis is then performed to solve its stress-strain response under real constraints and heat flow loads, and the failure probability is assessed in real time.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for analyzing the service performance of a full-size shell-and-tube heat exchanger based on domain-specific solution and cross-dimensional coupling includes the following steps: Step 1: Setting up the fluid flow in the tubes of the shell-and-tube heat exchanger A tube-side fluid domain model of a shell-and-tube heat exchanger is established. By simplifying the fluid channels inside the three-dimensional heat transfer tubes into one-dimensional fluid node elements, the one-dimensional incompressible fluid equation and the two-dimensional solid thermal conductivity equation are applied. The fluid and solid adopt a convective heat transfer boundary, and the Dittus-Boelter equation is selected to calculate the corresponding convective heat transfer coefficient. The length, inner diameter, wall thickness, spatial position and arrangement of the heat transfer tubes are set, water is selected as the coolant, and the corresponding physical property parameters are used to complete the fluid settings of the heat transfer tubes in the shell-and-tube heat exchanger. Step 2: Shell-side fluid setup for full-size shell-and-tube heat exchanger Step 2-1: Establish a shell-side fluid domain model for the shell-and-tube heat exchanger. Using a porous medium fluid calculation method, simplify the model of the fluid outside the heat transfer tubes. Specifically, simplify the regularly arranged heat transfer tube region into a continuous and uniform medium. Except for the heat transfer tube region, the geometric model maintains the actual heat exchanger structure, completing the full-size model construction of the shell-and-tube heat exchanger's shell-side fluid. Divide boundary layer meshes on the fluid domain and heat exchanger wall, and adjust different boundary layer numbers and the thickness of the first boundary layer to divide several different boundary layer mesh generation strategies. Step 2-2: Divide the volume mesh into different sizes, adopt the boundary layer mesh generation strategy mentioned above, use the porous medium fluid region and the Reynolds-Averaged Navier-Stokes turbulence model to carry out steady-state calculations, perform mesh independence analysis, determine the minimum number of meshes that meet the calculation accuracy, and establish a shell-side fluid three-dimensional mesh element. Steps 2-3: Set the anisotropic drag coefficient and volume average energy source term to characterize the drag effect of the heat transfer tube structure on fluid flow and heat transfer characteristics. The coolant is water, and set the corresponding physical property parameters. Step 3: Setting up the coupling between tube-side and shell-side fluids The tube-side fluid and shell-side fluid of the shell-and-tube heat exchanger are coupled and set up. The one-dimensional fluid node elements established in step 1 and the three-dimensional mesh elements of the shell-side fluid established in step 2 are used to establish the coordinate correspondence based on the structural design of the shell-and-tube heat exchanger. The node variables of the one-dimensional fluid are mapped to the three-dimensional fluid mesh element variables through a linear interpolation mapping algorithm. The mesh element variables of the three-dimensional fluid are mapped to the node variables of the one-dimensional fluid through a nearest neighbor mapping algorithm. Step 4: Calculation of bidirectional flow heat transfer coupling Step 4-1: Set the inlet temperature, inlet velocity, and outlet pressure of the shell-side three-dimensional fluid in the shell-and-tube heat exchanger. After initialization, use the Reynolds-Averaged Navier-Stokes turbulence model to perform steady-state calculations until convergence. The shell-side fluid temperature, fluid pressure, and heat transfer coefficient are calculated to provide an initial flow field environment for the fluid inside the heat transfer tubes. Step 4-2: Set the inlet temperature, inlet velocity, and outlet pressure of the one-dimensional fluid inside the heat transfer tubes of the shell-and-tube heat exchanger as the initial values ​​for the one-dimensional fluid equation; read the fluid temperature and heat transfer coefficient calculated in the three-dimensional fluid equation as the boundary conditions for the one-dimensional fluid equation; perform iterative calculations on the one-dimensional fluid equation using the finite element numerical solution algorithm until convergence, and calculate the tube-side fluid temperature, fluid heat transfer coefficient, fluid pressure, and fluid energy loss to provide an energy source term for the fluid outside the heat transfer tubes; Step 4-3: The three-dimensional shell-side fluid reads the fluid energy loss calculated by the one-dimensional tube-side fluid. Through the volume averaging algorithm, the one-dimensional tube-side fluid energy loss is converted into a volume average energy source term, and the settings of the porous medium model are updated as the boundary conditions for the next iteration step, realizing the bidirectional flow heat transfer coupling calculation of the fluid inside and outside the heat transfer tube. Step 5: Modeling and Constraint Setting of Solid Domain for Shell-and-Tube Heat Exchanger Heat Transfer Tubes A solid-domain geometric model of the heat transfer tubes in a shell-and-tube heat exchanger is established, maintaining the actual structural position and full-size modeling. A swept structured mesh is generated for each heat transfer tube. Mesh independence analysis of the solid domain is performed to determine the appropriate mesh size. Fixed constraints are applied at both ends of the heat transfer tube along the axial direction to simulate the actual support boundary conditions in the shell-and-tube heat exchanger. A data mapping coupling surface is set on the inner surface of the heat transfer tube to receive the temperature and heat transfer coefficient values ​​calculated by the fluid inside the heat transfer tube, and a data mapping coupling surface is set on the outer surface of the heat transfer tube to receive the temperature and heat transfer coefficient values ​​calculated by the fluid outside the heat transfer tube, which are used as calculation boundary conditions. Step 6: Heat transfer tube thermodynamic coupling calculation Select the solid domain geometric model of the heat transfer tubes of the shell-and-tube heat exchanger, and accurately map the fluid temperature, heat transfer coefficient and fluid pressure obtained in steps 4-1 and 4-2 onto the inner and outer surfaces of each heat transfer tube in the selected solid domain geometric model of the shell-and-tube heat exchanger according to the corresponding time steps. Perform structural statics calculation. This calculation solves the stress-strain response of the heat transfer tubes under the operating conditions of the heat exchanger, and at the same time calculates and outputs the failure probability of the heat transfer tubes under stress in real time. Step 7: Rapid Calculation and Analysis of Shell-and-Tube Heat Exchanger Service Performance By analyzing fluid temperature and pressure, the heat exchange performance and energy efficiency of shell-and-tube heat exchangers are comprehensively evaluated. The inlet and outlet temperature differences of the tube-side fluid and shell-side fluid are calculated, which directly reflect the amount of heat exchange and measure the cooling capacity of the shell-and-tube heat exchanger. The pressure loss obtained from the tube-side and shell-side fluid pressures is related to the pumping power consumption and is used to analyze the resistance characteristics of the heat exchanger. By modifying the inner and outer diameters and the spacing of the heat transfer tube bundles, the overall performance of the heat exchanger is optimized. Under the premise of achieving the target heat exchange capacity, a low operating pressure drop is maintained, thereby achieving the optimal balance between heat exchange efficiency and operating cost. Step 8: Mechanical property analysis of shell-and-tube heat exchangers under service conditions A coupled calculation of heat transfer in the tube-side and shell-side fluids and the solid domain of a shell-and-tube heat exchanger was constructed. Mechanical property analysis of the heat exchanger under service conditions was carried out, and the maximum principal stress, Mises stress, and maximum principal strain of the heat transfer tubes and heat exchanger structure were obtained. The maximum principal stress was compared with the material tensile strength and the Mises stress was compared with the material yield strength. The maximum principal strain was used to determine whether fatigue failure had occurred, and the reliability of the shell-and-tube heat exchanger under operating conditions was determined.

[0007] This invention reduces computational load by simplifying modeling and employing cross-dimensional coupling methods, achieving efficient fluid heat transfer simulation for shell-and-tube heat exchangers. Addressing the problem of coupled solution between one-dimensional tube-side and three-dimensional shell-side fluid programs, it applies domain coupling and data mapping methods to exchange data between programs based on spatial geometric positions. While ensuring the computational efficiency of each program, it ensures that the computational domain modeling conforms to the overall structure of the actual shell-and-tube heat exchanger, achieving coupled calculation of flow heat transfer and structural mechanics for full-size shell-and-tube heat exchangers. Compared with existing technologies, this invention has the following advantages: 1. The method of the present invention provides a simplified structure for a shell-and-tube heat exchanger, which can significantly improve the efficiency of heat exchanger performance analysis while ensuring calculation accuracy; 2. The method of this invention provides a two-way coupling scheme, which enables the mutual transfer of variables such as temperature, convective heat transfer coefficient, and pressure between the tube-side fluid, shell-side fluid, and solid domain, thereby improving the accuracy of inter-program coupling calculations. 3. The method of the present invention provides a cross-dimensional coupling scheme, which realizes the mapping between three-dimensional elements and nodes through interpolation mapping algorithm and nearest neighbor mapping algorithm for the three-dimensional porous medium fluid domain in the shell side and the one-dimensional fluid domain in the tube side; 4. The method of the present invention does not change the internal model of the analysis program for the fluid and solid domains of the heat exchanger, and can flexibly set the solution parameters. Attached Figure Description

[0008] Figure 1 This is a flowchart of the method of the present invention.

[0009] Figure 2 This is a schematic diagram of fluid flow in the tube.

[0010] Figure 3 This is a schematic diagram showing the coordinate correspondence between the shell-side fluid and the tube-side fluid.

[0011] Figure 4 This is a schematic diagram of the heat transfer tubes in a shell-and-tube heat exchanger. Detailed Implementation

[0012] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0013] like Figure 1 As shown, the present invention provides a method for analyzing and calculating the service performance of a full-size shell-and-tube heat exchanger based on domain-specific solution and cross-dimensional coupling. The steps are as follows: Step 1: A one-dimensional simplification method is used to establish the tube-side fluid domain model of the shell-and-tube heat exchanger. The three-dimensional fluid channel is simplified into one-dimensional fluid node elements along the axial direction. The model is described based on the one-dimensional incompressible flow equation and the two-dimensional solid heat conduction equation. The fluid-solid interface between the fluid and the inner surface of the heat transfer tube adopts convective heat transfer boundary conditions. The Dittus-Boelter equation is applied to calculate the convective heat transfer coefficient using fluid velocity, properties, tube diameter, and temperature parameters for fluid-solid coupling calculations. In the numerical model, the triangular arrangement and spatial layout of the heat transfer tubes are set, water is selected as the cooling medium, and corresponding property parameters are configured to complete the numerical modeling of tube-side flow and heat transfer. Figure 2 The figure shown is a schematic diagram of the established tube-side fluid domain model of a shell-and-tube heat exchanger. Step 2: Shell-side fluid setup for full-size shell-and-tube heat exchanger Step 2-1: Establish a shell-side fluid domain model for the shell-and-tube heat exchanger, such as... Figure 3 As shown in the three-dimensional fluid domain, except for the heat transfer tube region, the geometric modeling maintains the real heat exchanger structure. A complete fluid domain geometric model including the wall, inlet and outlet and baffles is established, and the regularly arranged heat transfer tube bundle region is equivalent to a continuous and uniform porous medium region. Fluid domain meshing is carried out, and an adjustable boundary layer mesh is set at the wall boundary. Multiple mesh refinement schemes are formed by adjusting the number of boundary layers and the thickness of the first boundary layer through the system.

[0014] Step 2-2: Conduct mesh independence verification. Use multiple sets of volume meshes of different sizes in conjunction with boundary layer strategies. Combine the Reynolds-Averaged Navier-Stokes turbulence model to perform steady-state calculations. By comparing the numerical deviations of fluid inlet and outlet pressure drop and fluid temperature changes, determine the optimal mesh configuration to ensure calculation accuracy and establish a three-dimensional mesh element for the shell-side fluid.

[0015] Steps 2-3: Complete the quantitative setting of porous medium parameters, calculate the anisotropic resistance coefficient based on the heat transfer tube arrangement structure, define the volume average energy source term to accurately characterize the flow resistance and heat transfer characteristics of the tube bundle region, and set the physical property parameters of the water coolant. Finally, establish a complete shell-side fluid calculation model.

[0016] Step 3: Setting up coupling between the tube-side and shell-side fluid domains: Establishing a cross-dimensional data exchange mechanism. For example... Figure 3 As shown, based on the actual geometric layout of the heat exchanger, a spatial coordinate mapping relationship is established between the one-dimensional fluid node elements constructed in step 1 and the three-dimensional shell-side fluid mesh elements constructed in step 2. A two-way variable transfer strategy is adopted: through a linear interpolation algorithm, the temperature, velocity, and other parameters of the one-dimensional tube-side fluid nodes are continuously mapped to the three-dimensional shell-side mesh elements, ensuring the smoothness of field variable transfer; with the help of the nearest neighbor mapping algorithm, the physical quantities such as the temperature field and pressure field of the three-dimensional shell-side mesh elements are mapped to the one-dimensional tube-side nodes, forming a closed solution loop. This coupling setting maintains the computational efficiency of the one-dimensional tube side while fully considering the complex flow characteristics of the three-dimensional shell side, laying the foundation for subsequent two-way iterative calculations.

[0017] Step 4: Calculation of bidirectional flow heat transfer coupling. Figure 1 The flowchart for the coupled calculation is given, and the specific calculation is as follows: Step 4-1: Initialization and Solution of the Three-Dimensional Flow Field in the Shell Side: The boundary conditions of the three-dimensional fluid domain in the shell side are set, including the inlet velocity, inlet temperature distribution, and static pressure outlet conditions. After initialization, the Reynolds-Averaged Navier-Stokes turbulence model and the SIMPLE algorithm are used for steady-state solution. By solving the three-dimensional mass, momentum, and energy conservation equations, the convergent shell-side fluid velocity field, temperature field, pressure field, and wall heat transfer coefficient distribution are obtained. This provides the initial flow field environment and boundary conditions for the one-dimensional flow simulation in the tube side.

[0018] Step 4-2: Iterative Calculation of One-Dimensional Flow in the Tube Pass: Set the inlet temperature, inlet velocity, and outlet pressure boundary conditions for the one-dimensional fluid in the tube pass; read the fluid temperature and heat transfer coefficient from the three-dimensional fluid calculation as boundary conditions for the one-dimensional fluid equation; iteratively solve the one-dimensional incompressible flow equation and energy equation using the finite element numerical discretization method until the convergence criterion is reached. The output includes the temperature distribution, pressure distribution, heat transfer coefficient, and fluid energy loss along the tube pass.

[0019] Step 4-3: Two-way Coupled Data Exchange and Update: Establish a data feedback mechanism between the tube side and the shell side. The calculated tube-side fluid energy loss is converted into an equivalent volumetric heat source term using a volume averaging algorithm. This term is then embedded into the energy equation of the shell-side porous medium model, updating its source term settings. The updated shell-side model serves as the input condition for the next iteration, re-executing the solution process of Step 4-1 to form a complete two-way coupled calculation loop. Through multiple iterations, the dynamic equilibrium of flow and heat transfer between the tube and shell sides is finally achieved, completing the steady-state solution of the coupled system.

[0020] Step 5: Solid Domain Modeling and Constraint Setting for Shell-and-Tube Heat Exchanger: Establish a geometric model of the solid domain of the shell-and-tube heat exchanger's heat transfer tubes, generate a structured mesh using sweep technology, and verify mesh independence; for example... Figure 4 The schematic diagram of the heat transfer tube structure of the shell-and-tube heat exchanger is shown. Fixed constraints are applied to both ends of the heat transfer tube along the axial direction to simulate the actual support of the tube sheet. At the same time, data mapping coupling interfaces are created on the inner and outer surfaces of the tube wall to receive the temperature and heat transfer coefficient field distribution provided by the fluid calculations in the tube side and shell side, respectively, as boundary conditions for the thermo-mechanical coupling calculation.

[0021] Step 6: Thermo-mechanical coupling calculation of heat transfer tubes: Based on the established geometric model of the solid domain of the heat transfer tubes in the shell-and-tube heat exchanger, the fluid temperature field, heat transfer coefficient distribution, and fluid pressure field data obtained by the tube-side and shell-side coupling calculations in Steps 4-1 and 4-2 are dynamically mapped to the corresponding mesh elements on the inner and outer walls of each heat transfer tube according to the corresponding time step using an interpolation algorithm; considering the thermo-mechanical coupling effect, the structural statics calculation is performed to solve the constitutive equation considering the combined effects of temperature load and pressure load, characterizing the multiaxial stress-strain distribution characteristics of the heat transfer tubes under actual operating conditions.

[0022] Step 7: Rapid Calculation and Analysis of Shell-and-Tube Heat Exchanger Service Performance: Based on the fluid temperature and pressure in the tube and shell sides, a systematic evaluation of the heat exchanger performance is conducted. The heat transfer capacity is quantitatively analyzed by calculating the inlet and outlet temperature differences between the tube and shell sides, directly reflecting its heat transfer capability. Simultaneously, pressure loss is calculated using the fluid pressures on both sides to assess flow resistance characteristics and correlate with system power consumption. Based on this, by adjusting the structural parameters and arrangement of the heat transfer tubes, the pressure drop level is effectively controlled while ensuring the required heat transfer capacity, ultimately achieving synergistic optimization of the heat exchanger's heat transfer efficiency and operational economy.

[0023] Step 8: Mechanical Characteristic Analysis of Shell-and-Tube Heat Exchanger under Service Conditions: Conduct a mechanical characteristic analysis of the heat exchanger under actual service conditions. Solve for the stress-strain field of the heat transfer tubes and key pressure-bearing components, extracting key mechanical parameters such as maximum principal stress, Mises equivalent stress, and maximum principal strain. Compare the maximum principal stress with the material's tensile strength to assess fracture risk. Compare the Mises stress with the material's yield strength to determine if the structure has entered a plastic state. Based on the maximum principal strain analysis results, predict fatigue life. Based on the comprehensive evaluation of the above multi-dimensional strength criteria, finally quantify and determine the structural reliability and safety margin of the heat exchanger under specific operating conditions.

[0024] In summary, steps 1 and 2 complete the relevant settings for the tube-side and shell-side fluid calculations of the heat exchanger; steps 3 and 4 complete the coupled flow and heat transfer calculations of the tube-side and shell-side of the shell-and-tube heat exchanger; steps 5 and 6 complete the data transfer and coupled calculations of the solid mechanics program for the heat transfer tubes of the shell-and-tube heat exchanger; steps 7 and 8 comprehensively evaluate the heat transfer performance and structural reliability of the heat exchanger. Through the above steps, the computational load is reduced by simplifying modeling and using cross-dimensional coupling methods. Domain coupling and data mapping methods are applied to achieve coupled solution of the one-dimensional tube-side fluid program and the three-dimensional shell-side fluid program. Under the premise of ensuring the computational efficiency of each, the coupled calculations of flow, heat transfer, and deformation of the shell-and-tube heat exchanger are realized.

Claims

1. A full-size shell-and-tube heat exchanger service performance analysis and calculation method based on sub-domain solving and cross-dimension coupling, characterized in that: Comprising the following steps: Step 1: Tube side fluid setting of the shell-and-tube heat exchanger A tube side fluid domain model of the shell-and-tube heat exchanger is established, the three-dimensional fluid channel in the heat transfer tube is simplified as a one-dimensional fluid node unit, a one-dimensional incompressible fluid equation and a two-dimensional solid thermal conductivity equation are applied, the fluid and the solid adopt a convective heat transfer boundary, and a Dittus-Boelter equation is selected to calculate the corresponding convective heat transfer coefficient; the length, inner diameter, wall thickness, spatial position and arrangement mode of the heat transfer tube are set, water is selected as the coolant, the corresponding physical property parameters are used, and the fluid setting of the heat transfer tube in the shell-and-tube heat exchanger is completed; Step 2: Full-size shell side fluid setting of the shell-and-tube heat exchanger Step 2-1: A shell side fluid domain model of the shell-and-tube heat exchanger is established, a porous medium fluid calculation method is used to simplify the modeling of the fluid outside the heat transfer tube, and specifically the regularly arranged heat transfer tube region is simplified as a continuous and uniform medium; except for the heat transfer tube region, the geometric modeling maintains the true heat exchanger structure, the full-size model of the shell side fluid of the shell-and-tube heat exchanger is completed; the fluid domain and the boundary layer grid on the heat exchanger wall are divided, different boundary layer layer numbers and first layer boundary layer thicknesses are adjusted, and several different boundary layer grid generation strategies are divided to generate; Step 2-2: Different size body grids are divided, the above boundary layer grid generation strategy is used, the porous medium fluid region and the Reynolds-Averaged Navier-Stokes turbulent flow model are used to carry out steady-state calculation, grid independence analysis is carried out, the minimum grid number meeting the calculation precision is determined, and a three-dimensional grid unit of the shell side fluid is established; Step 2-3: Anisotropic resistance coefficient and volume average energy source term are set to represent the resistance influence of the heat transfer tube structure on the fluid flow and the heat transfer characteristics, the coolant is water, and the corresponding physical property parameters are set; Step 3: Coupling setting of the tube side fluid and the shell side fluid The tube side fluid and the shell side fluid of the shell-and-tube heat exchanger are coupled and set, the one-dimensional fluid node unit established in step 1 and the three-dimensional grid unit of the shell side fluid established in step 2 are used to establish a coordinate correspondence based on the structure design of the shell-and-tube heat exchanger; the node variables of the one-dimensional fluid are mapped to the grid unit variables of the three-dimensional fluid through a linear interpolation mapping algorithm; the grid unit variables of the three-dimensional fluid are mapped to the node variables of the one-dimensional fluid through a nearest neighbor mapping algorithm; Step 4: Two-way flow heat exchange coupling calculation Step 4-1: The inlet temperature, inlet velocity and outlet pressure of the three-dimensional fluid of the shell side of the shell-and-tube heat exchanger are set, after initialization, the Reynolds-Averaged Navier-Stokes turbulent flow model is used for steady-state calculation until convergence, and the shell side fluid temperature, fluid pressure and heat transfer coefficient are calculated to provide an initialization flow field environment for the fluid in the heat transfer tube; Step 4-2: The inlet temperature, inlet velocity and outlet pressure of the one-dimensional fluid in the heat transfer tube of the shell-and-tube heat exchanger are set as the initial values of the one-dimensional fluid equation; The fluid temperature and heat transfer coefficient calculated by the three-dimensional fluid are read as the boundary conditions of the one-dimensional fluid equation; The one-dimensional fluid equation is calculated by the finite element numerical solution algorithm until convergence, and the fluid temperature, fluid heat transfer coefficient, fluid pressure and fluid energy loss of the tube are calculated, which provides the energy source term for the fluid outside the heat transfer tube; Step 4-3: The three-dimensional shell fluid reads the fluid energy loss calculated by the one-dimensional tube fluid, converts the one-dimensional tube fluid energy loss into a volume average energy source term through a volume average algorithm, and updates the settings of the porous medium model as the boundary conditions for the next iteration step, realizing the two-way flow and heat exchange coupling calculation of the fluid inside and outside the heat transfer tube; Step 5: Modeling and constraint setting of the solid domain of the heat transfer tube of the shell-and-tube heat exchanger A geometric model of the solid domain of the heat transfer tube of the shell-and-tube heat exchanger is established, and the geometric model is modeled in the true structure position and full size. Sweep structured grid division is performed on each heat transfer tube. Grid independence analysis is performed on the solid domain to determine the appropriate grid size. Fixed constraints are applied at both ends of the heat transfer tube in the axial direction to simulate the actual support boundary conditions of the heat exchanger. Data mapping coupling surfaces are set on the inner and outer surfaces of the heat transfer tube to receive the temperature and heat transfer coefficient values calculated by the fluid inside and outside the heat transfer tube, respectively, as the calculation boundary condition settings. Step 6: Thermal coupling calculation of the heat transfer tube Select the solid domain geometric model of the heat transfer tube of the shell-and-tube heat exchanger, and accurately map the fluid temperature, heat transfer coefficient and fluid pressure obtained in steps 4-1 and 4-2 to the inner and outer surfaces of each heat transfer tube of the selected solid domain geometric model of the heat transfer tube of the shell-and-tube heat exchanger according to the corresponding time step. Perform structural statics calculation to solve the stress and strain response of the heat transfer tube under the operating conditions of the heat exchanger, while calculating and outputting the failure probability of the heat transfer tube under stress in real time. Step 7: Quick calculation and analysis of the service performance of the shell-and-tube heat exchanger By analyzing the fluid temperature and fluid pressure, the heat exchange performance and energy efficiency level of the shell-and-tube heat exchanger are comprehensively evaluated. The temperature difference between the inlet and outlet of the tube and shell is calculated, which directly reflects the size of the heat exchange capacity and measures the cooling capacity of the shell-and-tube heat exchanger. The pressure loss obtained by the tube and shell fluid pressure is related to the pumping power, which is used to analyze the resistance characteristics of the heat exchanger. By modifying the inner and outer diameters and arrangement spacing of the heat transfer tube bundle, the comprehensive performance of the heat exchanger is optimized. Under the premise of achieving the target heat exchange capacity, the operating pressure drop is maintained at a low level, thereby achieving the optimal balance between heat exchange efficiency and operating cost. Step 8: Analysis of the mechanical properties of the shell-and-tube heat exchanger under service conditions The heat transfer and solid domain coupling calculation of the tube and shell fluid of the shell-and-tube heat exchanger is constructed, and the mechanical property analysis under the service conditions of the heat exchanger is carried out to obtain the maximum principal stress, Mises stress and maximum principal strain of the heat transfer tube and the heat exchanger structure. By comparing whether the maximum principal stress exceeds the tensile strength of the material and whether the Mises stress exceeds the yield strength of the material, and by judging whether fatigue failure occurs through the maximum principal strain, the reliability of the operating conditions of the shell-and-tube heat exchanger is determined.

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