Rectangular fuel assembly coupling and heat transfer coupling method and system and medium

Abstract

The invention relates to the technical field of nuclear reactor thermal hydraulic power, in particular to a rectangular fuel assembly coupling and heat transfer coupling method and system and a medium. The method or the system provided by the invention mainly comprises the following steps: acquiring the surface heat flux density distribution of the fuel plate; carrying out iterative calculation on coolant flow distribution characteristics and fuel plate heat conduction characteristics; and judging whether iteration of the heat conduction characteristic iterative calculation of the fuel plate is completed. By means of the method, the detailed coupling heat transfer calculation method and process are provided according to the flow heat transfer fine analysis calculation requirement of the rectangular fuel assembly, and the method and process can be used for accurately solving the coupling heat transfer problem. The method provided by the invention can be used as an algorithm basis for advanced research of development of a reactor core thermal hydraulic program of a reactor (such as CARR). Computational accuracy of the fuel assembly may be provided, thereby releasing thermotechnical design margin. The method plays an important role in improving the overall performance of the research reactor.

Description

Technical Field

[0001] The invention relates to the field of nuclear reactor thermal hydraulic technology, and in particular to a rectangular fuel assembly coupling heat transfer coupling method and system, and a medium. Background Art

[0002] like Figure 2 As shown, rectangular fuel assemblies are used in some advanced research reactors at home and abroad due to their compact structure and high power density.

[0003] At present, subchannel programs are used in nuclear power design to calculate fuel assemblies. However, due to the significant difference in structure between flat fuel and nuclear power fuel assemblies, existing programs and methods cannot be used to calculate rectangular fuel assemblies.

[0004] Due to the structure of the fuel assembly, the coolant flow distribution and the heat transfer of the fuel element are coupled together: the uneven coolant flow distribution causes different heat transfer capabilities, which in turn leads to different coolant temperature rise and physical properties, resulting in different flow resistances, which further affects the flow distribution, resulting in a large margin in the existing design calculation, that is, assuming that the flow of each channel is equal to the flow under cold conditions (obtained through hydraulic experiments), and the power of the fuel plate is evenly distributed to both sides. This calculation is greatly simplified, so the calculation error is large. Summary of the invention

[0005] The purpose of the present invention is to provide a rectangular fuel assembly coupling heat transfer coupling method and system, and medium to solve the above-mentioned problems in the prior art.

[0006] The embodiments of the present invention are implemented by the following technical solutions:

[0007] In a first aspect, the present invention provides a rectangular fuel assembly coupling heat transfer coupling method, comprising:

[0008] Step 1: Set the initial surface heat flux density of the fuel plate;

[0009] Step 2: Perform iterative calculation of coolant flow distribution characteristics;

[0010] Step 3: Determine whether the iteration of the coolant flow distribution characteristic is completed. If not, re-calculate the coolant flow distribution characteristic. If completed, perform the iterative calculation of the fuel plate thermal conductivity characteristic.

[0011] Step 4: Set the end iteration threshold to determine whether the difference between the surface heat flux obtained by iterative calculation of the thermal conductivity of the fuel plate and the initial surface heat flux is within the end iteration threshold. If so, the coupling iteration is completed; if not, start again from step 2. If completed, output the balanced coupling calculation results.

[0012] Preferably, obtaining the surface heat flux density distribution of the fuel plate includes:

[0013]

[0014] In the formula, q W,L is the heat flux density distribution on the left side of the fuel plate, q W,R is the heat flux density distribution on the right side of the fuel plate, P e is the total power of the fuel plate, W is the flow channel width, and L is the height of the fuel active area.

[0015] Preferably, the iterative calculation of the coolant flow distribution characteristic includes:

[0016] Initialize the coolant flow rate, perform fluid iterative calculations on each channel, and obtain the pressure drop and average pressure drop of all channels;

[0017] Iteration constraints are set by pressure drop and average pressure drop. If the iteration constraints are met, the flow distribution iteration is accepted and the iteration is completed. If the iteration constraints are not met, the iteration is not completed.

[0018] Preferably, the initializing the coolant flow rate includes:

[0019]

[0020] Where W i is the coolant flow rate in channel i, W t is the total coolant flow rate of all channels, N is the number of channels, k A is the channel area ratio, k D is the hydraulic diameter ratio, i, k, n are natural numbers.

[0021] Preferably, the setting of the iteration constraint by the pressure drop and the average pressure drop comprises:

[0022] whether the difference between the pressure drop and the average pressure drop satisfies less than or equal to a first upper limit value;

[0023] |Δp i -Δp ave |≤ε p

[0024] In the formula, Δp i is the pressure drop in the channel, Δp ave is the average pressure drop in the channel, ε p is the first upper error limit.

[0025] Preferably, the iterative calculation of the thermal conductivity characteristics of the fuel plate includes:

[0026] The third type of heat transfer boundary condition is set according to the flow distribution calculation results, and the temperature distribution of the fuel plate is obtained by iterative solution of the heat conduction equation; then the surface heat flux density is obtained by the temperature of the fuel plate and the temperature of the fluid.

[0027] Preferably, obtaining the surface heat flux density by the temperature of the fuel plate and the temperature of the fluid comprises:

[0028] q W =h||T W -T f |

[0029] In the formula, q W is the surface heat flux density, T is the convective heat transfer coefficient, T W is the temperature of the fuel plate, T f is the temperature of the fluid.

[0030] Preferably, the setting of constraint conditions according to the surface heat flux density includes:

[0031] max(|q W -q W,0 |)≤ε q

[0032] In the formula, q W,0 is the initial heat flux value, ε q is the second upper error limit;

[0033] If the maximum deviation between the surface heat flux density and the initial heat flux density value is less than or equal to the second upper error limit, the iteration is completed; if the maximum deviation between the surface heat flux density and the initial heat flux density value is greater than the second upper error limit, the iteration is not completed.

[0034] In a second aspect, the present invention further provides a rectangular fuel assembly coupled heat transfer coupling system, comprising:

[0035] an acquisition module configured to acquire calculation input parameters such as the number of channels, channel structural parameters, the number and size of fuel plates, total power and power distribution ratio between each fuel plate, axial power distribution, coolant inlet temperature, total flow rate, reference pressure value, etc.;

[0036] The iteration module is configured to perform iterative calculation of the coolant flow distribution characteristic; determine whether the iteration of the coolant flow distribution characteristic is completed, if not, re-perform the iterative calculation of the coolant flow distribution characteristic, if completed, perform the iterative calculation of the fuel plate thermal conductivity characteristic; determine whether the coupled iterative calculation is completed, if not, re-perform the iterative calculation from the coolant flow distribution characteristic, if completed, output the coupled calculation result of the distribution reaching equilibrium;

[0037] The main control module is connected with the acquisition module and the iteration module, and is used to execute the above-mentioned rectangular fuel assembly coupled heat transfer coupling method.

[0038] In a third aspect, a computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the above-mentioned rectangular fuel assembly coupling heat transfer coupling method is implemented.

[0039] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0040] The method or system provided by the present invention mainly includes obtaining the surface heat flux density distribution of the fuel plate; performing iterative calculation of the coolant flow distribution characteristics; performing iterative calculation of the thermal conductivity characteristics of the fuel plate; judging whether the iterative calculation of the thermal conductivity characteristics of the fuel plate is iteratively completed, if not completed, restarting from the iterative calculation of the coolant flow distribution characteristics, if completed, outputting the coupled calculation result of the distribution reaching a balance. Through the above method, in view of the refined analysis and calculation requirements of the flow heat transfer of the rectangular fuel assembly, only focusing on the inherent characteristics of the flow distribution and the conjugate heat transfer process of the coolant-fuel plate, a detailed coupled heat transfer calculation method and process are proposed, which can be used for the accurate solution of the above coupled heat transfer problem. The present invention can be used as the algorithm basis for the development of the core thermal hydraulic program of advanced research reactors (such as CARR). It can provide the calculation accuracy of the fuel assembly, thereby releasing the thermal design margin. It plays an important role in improving the overall performance of the research reactor.

[0041] Secondly, the present invention embodies the coupling characteristics between the coolant and the fuel plate, and improves the calculation accuracy of the flow distribution and the heat conduction process of the components. The numerical calculation process provided by the present invention has a fast convergence speed, high calculation accuracy, and the program is easy to implement. The present invention proposes a detailed coupled heat transfer calculation method and process, which can be used to accurately solve the above-mentioned coupled heat transfer problems. The present invention can be used as an algorithm basis for the development of core thermal hydraulic programs. It can provide the calculation accuracy of the fuel assembly, thereby releasing the thermal design margin. It plays an important role in improving the overall performance of the reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 It is a schematic diagram of the process of the present invention;

[0044] Figure 2It is a schematic cross-sectional view of a flat-plate component of the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0046] The division of modules in this application is a logical division. There may be other division methods when implemented in actual applications. For example, multiple modules can be combined or integrated into another system, or some features can be ignored or not executed.

[0047] The modules or submodules described independently may be physically separated or not: they may be implemented by software or hardware, and some modules or submodules may be implemented by software, and the processor may call the software to implement the functions of these modules or submodules, and other modules or submodules may be implemented by hardware, such as by hardware circuits. In addition, some or all of the modules may be selected according to actual needs to achieve the purpose of the present application.

[0048] Please refer to Figure 1 The present invention provides a rectangular fuel assembly coupling heat transfer coupling method, comprising:

[0049] Step 1: Set the initial surface heat flux density of the fuel plate;

[0050] In the coupled calculation, the number, size, and power distribution of the fuel plates are all given. Therefore, it can be directly assumed that the upper and lower ends of the fuel plate are insulated, and the heat flux density on the left and right sides is equal, which is equal to the total power of the single plate divided by the area on the left and right sides that is in contact with the coolant.

[0051]

[0052] In the formula, q W,L is the heat flux density distribution on the left side of the fuel plate, q W,R is the heat flux density distribution on the right side of the fuel plate, P e is the total power of a single fuel plate, W is the channel width, and L is the height of the fuel active area.

[0053] Step 2: Perform iterative calculation of coolant flow distribution characteristics;

[0054] Step 3: Determine whether the iteration of the coolant flow distribution characteristic is completed. If not, re-calculate the coolant flow distribution characteristic. If completed, perform the iterative calculation of the fuel plate thermal conductivity characteristic. The thermal conductivity calculation iteration itself is relatively simple and will not be described in detail.

[0055] Step 4: Determine whether the coupling iterative calculation is completed. If not, start again from step 2. If completed, output the coupling calculation result that achieves equilibrium distribution.

[0056] Through the above method, the invention embodies the coupling characteristics between the coolant and the fuel plate, and improves the calculation accuracy of the flow distribution and the heat conduction process of the components. The numerical calculation process provided by the present invention has a fast convergence speed, high calculation accuracy, and easy program implementation. The present invention proposes a detailed coupled heat transfer calculation method and process, which can be used to accurately solve the above-mentioned coupled heat transfer problems. The present invention can serve as an algorithmic basis for the development of core thermal hydraulic programs. It can provide the calculation accuracy of the fuel assembly, thereby releasing the thermal design margin. It plays an important role in improving the overall performance of the reactor.

[0057] In an exemplary embodiment of the present invention, performing iterative calculation of coolant flow distribution characteristics includes:

[0058] Initialize the coolant flow rate, perform fluid calculations on each channel, and obtain the pressure drop and average pressure drop of all channels;

[0059] Iteration constraints are set by pressure drop and average pressure drop. If the iteration constraints are met, the flow distribution iteration is accepted and the iteration is completed. If the iteration constraints are not met, the iteration is not completed.

[0060] Specifically, the following formula is used to initialize the flow of each channel. This is a theoretical solution for flow distribution that ignores the influence of shape resistance and power. It can better reflect the influence of channel size on flow distribution. Initializing the coolant flow includes:

[0061]

[0062] Where W i is the coolant flow rate of channel i, W t is the total flow rate of channel coolant, N is the number of channels, k A is the channel area ratio, k D is the hydraulic diameter ratio, which is obtained by selecting the first channel as the reference value and dividing it. i, k, and n are natural numbers.

[0063] The key to fluid-solid coupling is still the distribution of flow. This formula reflects the influence of channel geometry differences and can effectively reduce the number of iterations.

[0064] The iterative calculation of fluid flow for each channel includes:

[0065] Each channel is closed, so it is a typical convection process, which requires iterative solution of the fluid mass, momentum and energy conservation equations. The relevant algorithms are relatively mature, such as the SIMPLER algorithm based on staggered grids; or the differential equations based on the same grid, and then simple iterations between the fluid mass, momentum and energy conservation equations until convergence, which completes the calculation of one channel. If each channel is calculated once, the pressure drop of all channels can be obtained.

[0066] Δp i =p i,in -p i,out

[0067]

[0068] In the formula, Δp i is the pressure drop in the channel, p i,in is the inlet pressure of the channel, p i,out is the outlet pressure of the channel.

[0069] Specifically, the iteration constraints set by pressure drop and average pressure drop include:

[0070] whether the difference between the pressure drop and the average pressure drop satisfies less than or equal to a first upper limit value;

[0071] |Δp i -Δp ave |≤ε p

[0072] In the formula, Δp i is the pressure drop in the channel, Δp ave is the average pressure drop in the channel, ε p is the first upper error limit.

[0073] If it is satisfied, the iteration is completed and the next step is carried out. If it is not satisfied, the channel inlet flow value is changed again and the process returns to step 2.

[0074] In an exemplary embodiment of the present invention, the iterative calculation of the thermal conductivity of the fuel plate includes:

[0075] Boundary conditions are set, and the temperature of the fuel plate is obtained by iterative solution of the heat conduction equation; the surface heat flux density is obtained by the temperature of the fuel plate and the temperature of the fluid, and constraint conditions are set according to the surface heat flux density. The constraint conditions are used to determine whether the coupled iteration (external iteration) calculation is completed.

[0076] Among them, regarding setting boundary conditions, the surface in contact between the fuel plate and the fluid meets the third type of boundary conditions, namely, the convection heat transfer boundary, and the remaining surfaces are set as adiabatic boundaries.

[0077] The heat conduction equation is discretized to obtain a set of coupled discrete equations; if the change of fuel properties with temperature is considered, the set of equations is still nonlinear. For this reason, the iterative method can be used to solve the heat conduction equation to obtain the temperature distribution inside the fuel plate. The relevant iterative method is relatively mature.

[0078] For example,

[0079] Where u is the temperature at position x and time t, α is the diffusion rate, is the Laps operator.

[0080] Time discretization: Divide the time domain into several small time steps Δt.

[0081] Spatial discretization: Divide the spatial domain into a grid of points (e.g. using the central difference method).

[0082] The iterative process includes: selecting initial conditions (for example, setting initial temperature distribution); setting boundary values ​​according to boundary conditions (such as fixed temperature or adiabatic conditions); and calculating the temperature distribution at time n+1 using an iterative formula until convergence.

[0083] Convergence and stability: When choosing the time step Δt and the space step Δx, attention should be paid to the stability conditions (such as the CFL condition) to ensure the convergence of the numerical solution.

[0084] In an exemplary embodiment of the present invention, obtaining the surface heat flux density by the temperature of the fuel plate and the temperature of the fluid comprises:

[0085] q W =h||T W -T f |

[0086] In the formula, q W is the surface heat flux density, T is the convective heat transfer coefficient, T W is the temperature of the fuel plate, T f is the temperature of the fluid.

[0087] In an exemplary embodiment of the present invention, setting constraints according to surface heat flux density includes:

[0088] max(|q W -q W,0 |)≤ε q

[0089] In the formula, q W,0 is the assumed initial heat flux value, ε q is the second upper error limit;

[0090] If the maximum deviation between the surface heat flux density and the initial heat flux density value is less than or equal to the second error upper limit value, the coupled iteration (external iteration) is completed; if the maximum deviation between the surface heat flux density and the initial heat flux density value is greater than the second error upper limit value, the iteration is not completed.

[0091] This process is convenient for organizing the program structure, and it is relatively simple to judge the iterative convergence. Each link is relatively independent, which is convenient for acceleration.

[0092] The present invention also provides a rectangular fuel assembly coupled heat transfer coupling system, comprising:

[0093] The acquisition module is configured to obtain calculation input parameters such as the number of channels, channel structure parameters, the number and size of fuel plates, total power and the power distribution ratio between each fuel plate, axial power distribution, coolant inlet temperature, total flow, reference pressure value, etc.

[0094] The iteration module is configured to perform iterative calculation of the coolant flow distribution characteristic; determine whether the iteration of the coolant flow distribution characteristic is completed, if not, re-perform the iterative calculation of the coolant flow distribution characteristic, if completed, perform the iterative calculation of the thermal conductivity characteristic of the fuel plate; determine whether the iterative calculation of the thermal conductivity characteristic of the fuel plate is completed, if not, re-perform the iterative calculation from the coolant flow distribution characteristic, if completed, output the coupling calculation result of the distribution reaching equilibrium;

[0095] The main control module is connected with the acquisition module and the iteration module, and is used to execute the above-mentioned rectangular fuel assembly coupled heat transfer coupling method.

[0096] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0097] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. The computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods of various embodiments of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0098] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A rectangular fuel assembly coupling heat transfer coupling method, characterized in that: include: Step 1: Set the initial surface heat flux density of the fuel plate; Step 2: Perform iterative calculation of coolant flow distribution characteristics; Step 3: Determine whether the iteration of the coolant flow distribution characteristic is completed. If not, re-calculate the coolant flow distribution characteristic. If completed, perform the iterative calculation of the fuel plate thermal conductivity characteristic. Step 4: Set the end iteration threshold to determine whether the difference between the surface heat flux obtained by iterative calculation of the thermal conductivity of the fuel plate and the initial surface heat flux is within the end iteration threshold. If so, the coupling iteration is completed and the coupled calculation result that reaches equilibrium is output; if not, start again from step 2.

2. A rectangular fuel assembly coupling heat transfer coupling method according to claim 1, characterized in that: The setting of the initial surface heat flux density of the fuel plate comprises: In the formula, q W,L is the heat flux density distribution on the left side of the fuel plate, q W,R is the heat flux density distribution on the right side of the fuel plate, P e is the total power of the fuel plate, W is the flow channel width, and L is the height of the fuel active area.

3. A rectangular fuel assembly coupling heat transfer coupling method according to claim 1, characterized in that: The iterative calculation of the coolant flow distribution characteristic comprises: Initialize the coolant flow rate, perform fluid iterative calculations on each channel, and obtain the pressure drop and average pressure drop of all channels; Iteration constraints are set by pressure drop and average pressure drop. If the iteration constraints are met, the flow distribution iteration is ended and the iteration is completed. If the iteration constraints are not met, the iteration is not completed.

4. A rectangular fuel assembly coupling heat transfer coupling method according to claim 3, characterized in that: Initializing the coolant flow rate includes: Where W i is the coolant flow rate in channel i, W t is the total coolant flow rate of all channels, N is the number of channels, k A is the channel area ratio, k D is the hydraulic diameter ratio, i, k, n are natural numbers.

5. A rectangular fuel assembly coupling heat transfer coupling method according to claim 3, characterized in that: The iterative constraints set by pressure drop and average pressure drop include: whether the difference between the pressure drop and the average pressure drop satisfies less than or equal to a first upper limit value; |Δp i -·△p ave |≤ε p In the formula, Δp i is the pressure drop in the channel, Δp ave is the average pressure drop in the channel, ε p is the first upper error limit.

6. A rectangular fuel assembly coupling heat transfer coupling method according to claim 1, characterized in that: The iterative calculation of the thermal conductivity characteristics of the fuel plate includes: The third type of heat transfer boundary condition is set according to the flow distribution calculation results, and the temperature distribution of the fuel plate is obtained by iterative solution of the heat conduction equation; then the surface heat flux density is obtained by the temperature of the fuel plate and the temperature of the fluid.

7. A rectangular fuel assembly coupling heat transfer coupling method according to claim 6, characterized in that: The obtaining of the surface heat flux density by the temperature of the fuel plate and the temperature of the fluid comprises: q w =h|T w -T f | In the formula, q W is the surface heat flux density, h is the convective heat transfer coefficient, T W is the temperature of the fuel plate, T f is the temperature of the fluid.

8. A rectangular fuel assembly coupling heat transfer coupling method according to claim 7, characterized in that: The constraint conditions set according to the surface heat flux density include: max(|q w -q w，0 |)≤ε q In the formula, q W,0 is the initial assumed heat flux value, ε q is the second upper error limit; If the maximum deviation between the surface heat flux and the initial heat flux is less than or equal to the second upper error limit, the coupled iteration is completed; if the maximum deviation between the surface heat flux and the initial heat flux is greater than the second upper error limit, the iteration is not completed.

9. A rectangular fuel assembly coupled heat transfer coupling system, characterized in that: include: an acquisition module configured to acquire calculation input parameters such as the number of channels, channel structural parameters, the number and size of fuel plates, total power and power distribution ratio between each fuel plate, axial power distribution, coolant inlet temperature, total flow rate, reference pressure value, etc.; The iteration module is configured to perform iterative calculation of the coolant flow distribution characteristic; determine whether the iteration of the coolant flow distribution characteristic is completed, if not, re-perform the iterative calculation of the coolant flow distribution characteristic, if completed, perform the iterative calculation of the fuel plate thermal conductivity characteristic; determine whether the coupled iterative calculation is completed, if not, re-perform the iterative calculation from the coolant flow distribution characteristic, if completed, output the coupled calculation result of the distribution reaching equilibrium; A main control module is connected to the acquisition module and the iteration module, and is used to execute a rectangular fuel assembly coupled heat transfer coupling method as described in any one of claims 1 to 8.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, a rectangular fuel assembly coupling heat transfer coupling method as described in any one of claims 1 to 8 is implemented.

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