A rectangular fuel assembly coupled heat transfer coupling method and system, medium

Abstract

The present application relates to the technical field of nuclear reactor thermal hydraulic, in particular, to a rectangular fuel assembly coupling heat transfer coupling method and system, medium. The method or system provided by the present application mainly includes obtaining the surface heat flux density distribution of the fuel plate; performing the iteration calculation of the coolant flow distribution characteristics and the fuel plate heat conduction characteristics; judging whether the iteration calculation of the fuel plate heat conduction characteristics is completed. Through the above method, for the refined analysis and calculation requirement of the rectangular fuel assembly flow heat transfer, a detailed coupling heat transfer calculation method and process are proposed, which can be used for accurate solution of the above coupling heat transfer problem. The present application can be used as the algorithm basis for the development of the core thermal hydraulic program of the advanced research reactor (such as CARR). The calculation accuracy of the fuel assembly can be provided, so as to release the thermal design margin. It plays an important role in improving the overall performance of the research reactor.

Description

Technical Field

[0001] This invention relates to the field of nuclear reactor thermal-hydraulic technology, and more specifically, to a method, system, and medium for coupling heat transfer of rectangular fuel assemblies. Background Technology

[0002] like Figure 2 As shown, rectangular fuel assemblies, due to their compact structure and high power density, have been used in some advanced research reactors both domestically and internationally.

[0003] Currently, subchannel programs are used for fuel assembly calculations in nuclear power plant design. However, due to the significant structural differences between flat-plate fuel and nuclear power fuel assemblies, existing programs and methods cannot be used for calculating rectangular fuel assemblies.

[0004] Due to the structure of the fuel assembly, the coolant flow distribution and heat transfer of the fuel elements are coupled: uneven coolant flow distribution leads to different heat transfer capabilities, resulting in different coolant temperature rises and physical properties, which in turn cause different flow resistances, further affecting the flow distribution. This results in a large margin in current design calculations, assuming that the flow rate of each channel is equal to the flow rate under cold conditions (obtained through hydraulic experiments), and that the power of the fuel plate is evenly distributed to both sides. This simplification leads to a large calculation error. Summary of the Invention

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

[0006] The embodiments of the present invention are achieved through the following technical solutions:

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

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

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

[0010] Step 3: Determine whether the coolant flow distribution characteristic iteration is complete. If not, recalculate the coolant flow distribution characteristic iteration. If complete, recalculate the fuel plate thermal conductivity characteristic iteration.

[0011] Step 4: Set an iteration termination threshold. Determine if the difference between the surface heat flux density obtained from the iterative calculation of the fuel plate's thermal conductivity and the initial surface heat flux density is within the termination threshold. If yes, the coupled iteration is complete; otherwise, restart from Step 2. If complete, output the coupled calculation result that has reached equilibrium.

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

[0013]

[0014] wherein q W,L is the left surface heat flux distribution of the fuel plate, q W,R is the right surface heat flux distribution of the fuel plate, P e is the total power of the fuel plate, W is the flow channel width, and L is the fuel active region height.

[0015] Preferably, the performing the coolant flow distribution characteristic iteration calculation comprises:

[0016] initializing the coolant flow, performing fluid iteration calculation for each channel, and obtaining the pressure drop and average pressure drop of all channels;

[0017] setting iteration constraints through the pressure drop and average pressure drop, if the iteration constraints are met, then accepting the flow distribution iteration, the iteration is completed, if the iteration constraints are not met, then the iteration is not completed.

[0018] Preferably, the initializing the coolant flow comprises:

[0019]

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

[0021] Preferably, the setting iteration constraints through the pressure drop and average pressure drop comprises:

[0022] whether the difference between the pressure drop and the average pressure drop meets a first upper limit value;

[0023] |Δp i -Δp ave |≤ε p

[0024] wherein Δp i is the pressure drop of the channel, Δp ave is the average pressure drop of the channel, ε p is the first error upper limit value.

[0025] Preferably, the performing the fuel plate heat conduction characteristic iteration calculation comprises:

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

[0027] Preferably, the surface heat flux density obtained 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, h is the convection heat transfer coefficient, T W is the temperature of the fuel plate, and T f is the temperature of the fluid.

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

[0031] max(|q W -q W,0 |)≤ε q

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

[0033] If the maximum deviation value of 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 iteration is completed, and if the maximum deviation value of 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.

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

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

[0036] An iteration module is configured to perform coolant flow distribution characteristic iteration calculation; judge whether the coolant flow distribution characteristic iteration is completed, if not, re-perform the coolant flow distribution characteristic iteration calculation, if yes, perform fuel plate heat conduction characteristic iteration calculation; judge whether the coupling iteration calculation is completed, if not, re-perform from the coolant flow distribution characteristic iteration calculation, if yes, output the coupling calculation result in which the distribution reaches equilibrium.

[0037] A master module is connected with the acquisition module and the iteration module, and is used for executing the rectangular fuel assembly coupled heat transfer coupling method.

[0038] In a third aspect, a computer readable storage medium is provided, and a computer program is stored on the computer readable storage medium, and the computer program is executed by a processor to implement the rectangular fuel assembly coupled heat transfer coupling method.

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

[0040] The method or system provided by the present application mainly comprises the following steps: acquiring the surface heat flux density distribution of a fuel plate; performing coolant flow distribution characteristic iteration calculation; performing fuel plate heat conduction characteristic iteration calculation; judging whether the fuel plate heat conduction characteristic iteration calculation is completed, if not, re-performing the coolant flow distribution characteristic iteration calculation, and if yes, outputting the coupled calculation result of the distribution reaching balance. Through the above method, for the refined analysis and calculation requirement of the rectangular fuel assembly flow heat transfer, only the internal characteristics of the flow distribution and the coolant-fuel plate conjugate heat transfer process are considered, a detailed coupled heat transfer calculation method and process are proposed, which can be used for accurate solution of the above coupled heat transfer problem. The present application can be used as the algorithm basis for the development of the core thermal hydraulic program of an advanced research reactor (such as CARR). The calculation accuracy of the fuel assembly can be provided, so as to release the thermal design margin. The present application plays an important role in improving the overall performance of the reactor.

[0041] Secondly, the present application embodies the coupling characteristics between the coolant and the fuel plate, improves the calculation accuracy of the flow distribution and the element heat conduction process. The numerical calculation process given by the present application has fast convergence speed and high calculation accuracy, and the program is easy to implement. The present application proposes a detailed coupled heat transfer calculation method and process, which can be used for accurate solution of the above coupled heat transfer problem. The present application can be used as the algorithm basis for the development of the core thermal hydraulic program. The calculation accuracy of the fuel assembly can be provided, so as to release the thermal design margin. The present application plays an important role in improving the overall performance of the reactor. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical scheme of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and should not be regarded as a limitation to the scope. Other related drawings can also be obtained by those skilled in the art without creative labor.

[0043] Figure 1 The flowchart of the present application;

[0044] Figure 2A schematic view of a cross section of a flat plate type assembly according to the present application. DETAILED DESCRIPTION

[0045] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0046] The division of the modules appearing in the present application is a logical division, and in actual application, another division mode can be used, for example, a plurality of modules can be combined or integrated in another system, or some features can be ignored or not executed.

[0047] The independently described modules or sub-modules can be physically separated or not physically separated, can be software implemented or hardware implemented, and part of the modules or sub-modules can be software implemented, the function of the part of the modules or sub-modules is called by a processor, and the other part of the modules or sub-modules is hardware implemented, for example, is implemented by a hardware circuit. In addition, part or all of the modules can be selected to achieve the purpose of the present application according to actual needs.

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

[0049] Step one: setting the initial surface heat flux density of the fuel plate;

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

[0051]

[0052] In the formula, q W,L q W,R q e is the total power of a single fuel plate, W is the width of the flow channel, and L is the height of the fuel active region.

[0053] Step two: performing an iterative calculation of the coolant flow distribution characteristics;

[0054] Step three: judging whether the coolant flow distribution characteristic iteration is completed, if not, re-performing the coolant flow distribution characteristic iteration calculation, if yes, performing the fuel plate heat conduction characteristic iteration calculation, the heat conduction calculation iteration itself is simple, and thus is not described herein;

[0055] Step four: judging whether the coupling iteration calculation is completed, if not, re-performing from step two, if yes, outputting the coupling calculation result of the distribution reaching balance.

[0056] Through the above method, the coupling characteristics between the coolant and the fuel plate are embodied, and the calculation precision of the flow distribution and the element heat conduction process is improved. The numerical calculation flow provided by the present application has fast convergence speed, high calculation precision, and is easy to realize. The present application provides a detailed coupling heat transfer calculation method and flow, and can be used for accurate solution of the coupling heat transfer problem. The present application can be used as an algorithm basis for development of a reactor core thermal hydraulic program, and can provide calculation accuracy of the fuel assembly, thereby releasing a thermal design margin. The present application plays an important role in improvement of the overall performance of the reactor

[0057] In an example embodiment of the present application, the coolant flow distribution characteristic iteration calculation comprises:

[0058] The coolant flow is initialized, and fluid calculation is performed on each channel to obtain the pressure drop and average pressure drop of all channels;

[0059] The iteration constraint is set through the pressure drop and the average pressure drop, if the iteration constraint is met, the flow distribution iteration is accepted, and the iteration is completed, if the iteration constraint is not met, the iteration is not completed.

[0060] Specifically, the flow of each channel is initialized by using the following formula, which is a flow distribution theoretical solution ignoring the shape resistance and power influence, and can better reflect the influence of channel size on flow distribution.

[0061]

[0062] In the formula, W i is the coolant flow of the channel i, W t is the total coolant flow of the channel, N is the number of channels, k A is the channel area ratio, k D is the hydraulic diameter ratio, the first channel is selected as a reference value to obtain, i, k, and n are natural numbers.

[0063] The key of the fluid-structure coupling is the flow distribution, and the formula reflects the influence of the channel geometric difference, and can effectively reduce the iteration times.

[0064] In the formula, the fluid iteration calculation on each channel comprises:

[0065] Each channel is closed, so it is a typical convection process, and the fluid mass, momentum and energy conservation equations need to be solved iteratively. The relevant algorithm is relatively mature, such as the SIMPLER algorithm based on staggered grid; or based on the difference equation of the same grid, then a simple iteration is performed between the fluid mass, momentum and energy conservation equations until convergence, that is, the calculation of one channel is completed. After each channel is calculated, 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 of the channel, p i,in is the inlet pressure of the channel, and p i,out is the outlet pressure of the channel.

[0069] Specifically, the iteration constraint is set by the pressure drop and the average pressure drop, including:

[0070] Whether the difference between the pressure drop and the average pressure drop satisfies the first upper limit value or not;

[0071] |Δp i -Δp ave |≤ε p

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

[0073] If it is satisfied, the iteration is completed, and the next step is performed, and if it is not satisfied, the channel inlet flow value is changed back to step two.

[0074] In an example embodiment of the present application, the fuel plate heat conduction characteristic iterative calculation includes:

[0075] Setting boundary conditions, obtaining the temperature of the fuel plate according to the iterative solution of the heat conduction equation; obtaining the surface heat flux density according to the temperature of the fuel plate and the temperature of the fluid, setting a constraint condition according to the surface heat flux density, and judging whether the coupling iteration (outer iteration) calculation is completed according to the constraint condition.

[0076] Among them, regarding the setting of boundary conditions, the surface of the fuel plate and the fluid meets the third type of boundary condition, that is, the convection heat transfer boundary, and the rest of the surface is set as an adiabatic boundary.

[0077] where u is the temperature at position x and time t, and a is the thermal diffusivity.

[0078] For example,

[0079] where u is the temperature at position x and time t, and a is the thermal diffusivity. is the Laplacian operator.

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

[0081] Space discretization: divide the spatial domain into grid points (e.g., using central difference method).

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

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

[0084] In an example embodiment of the present application, the surface heat flux density is obtained by the temperature of the fuel plate and the temperature of the fluid, including:

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

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

[0087] In an example embodiment of the present application, the constraint condition is set according to the surface heat flux density, including:

[0088] max(|q W -q W,0 |)≤ε q

[0089] where q is the assumed initial heat flux density value, and ε is the second error upper limit value. W,0 q

[0090] ​​​​​If the maximum deviation value of the surface heat flow density from the initial heat flow density value is less than or equal to the second error upper limit value, the coupling iteration (outer iteration) is completed, and if the maximum deviation value of the surface heat flow density from the initial heat flow density value is greater than the second error upper limit value, the iteration is not completed.

[0091] The flow is convenient for organizing program structure, and iteration convergence judgment is simple.

[0092] The application further provides a rectangular fuel assembly coupling heat coupling system, comprising:

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

[0094] The iteration module is configured to perform coolant flow distribution characteristic iteration calculation, judge whether the coolant flow distribution characteristic iteration is completed, if not, re-perform the coolant flow distribution characteristic iteration calculation, if yes, perform fuel plate heat conduction characteristic iteration calculation, judge whether the fuel plate heat conduction characteristic iteration is completed, if not, re-perform from the coolant flow distribution characteristic iteration calculation, if yes, output the coupling calculation result of distribution reaching balance.

[0095] The main control module is connected with the obtaining module and the iteration module, and is used for executing the rectangular fuel assembly coupling heat coupling method.

[0096] In addition, each functional unit in each embodiment of the application can be integrated in one processing unit, or each unit can be physically present independently, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0097] If the integrated unit is realized 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 stored in a storage medium includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method of each embodiment of the application. The foregoing storage medium includes a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various program code storage media.

[0098] The above merely describes the preferred embodiments of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method of coupling heat transfer in a rectangular fuel assembly, the method comprising: The method comprises the following steps: Step 1: setting an initial surface heat flux of the fuel plate; Step 2: performing an iteration calculation of coolant flow distribution characteristics; Step 3: judging whether the iteration of the coolant flow distribution characteristics is completed, if not, re-performing the iteration calculation of the coolant flow distribution characteristics, if yes, performing an iteration calculation of the heat conduction characteristics of the fuel plate; Step 4: setting an end iteration threshold, judging whether the difference between the surface heat flux obtained by the iteration calculation of the heat conduction characteristics of the fuel plate and the initial surface heat flux is within the end iteration threshold, if yes, the coupling iteration is completed, and the coupling calculation result reaching equilibrium is output, if not, re-performing from Step 2; The iteration calculation of the coolant flow distribution characteristics comprises the following steps: initializing the coolant flow, performing a fluid iteration calculation for each channel to obtain the pressure drop and average pressure drop of all channels; setting an iteration constraint through the pressure drop and average pressure drop, if the iteration constraint is met, ending the flow distribution iteration, if not, the iteration is not completed; The iteration calculation of the heat conduction characteristics of the fuel plate comprises the following steps: setting a third type of heat transfer boundary condition from the flow distribution calculation result, obtaining the temperature distribution of the fuel plate according to the iteration solution of the heat conduction equation, and then obtaining the surface heat flux through the temperature of the fuel plate and the temperature of the fluid.

2. The method of claim 1, wherein the coupling method is a rectangular fuel assembly coupling heat coupling method. The setting of the initial surface heat flux of the fuel plate comprises the following steps: wherein is the fuel plate left side surface heat flux distribution, is the fuel plate right side surface heat flux distribution, is the fuel plate total power, is the flow channel width, is the fuel active zone height.

3. The method of claim 2, wherein the coupling method is a rectangular fuel assembly coupling heat coupling method. The initialization of the coolant flow comprises the following steps: wherein Qc is the coolant flow rate for channel i, Qc is the total coolant flow rate for all channels, N is the number of channels, A is the area ratio of channels, D is the hydraulic diameter ratio, , , is a natural number.

4. The method of claim 2, wherein the coupling method is a rectangular fuel assembly coupling heat coupling method. The setting of the iteration constraint through the pressure drop and average pressure drop comprises the following steps: whether the difference between the pressure drop and the average pressure drop is less than or equal to a first upper limit value; wherein is the pressure drop of the channel, is the average pressure drop of the channel, is the first error upper limit value.

5. The method of claim 4, wherein the coupling method is a rectangular fuel assembly coupling heat coupling method, characterized by, The obtaining of the surface heat flux through the temperature of the fuel plate and the temperature of the fluid comprises the following steps: wherein is the surface heat flux density, is the convective heat transfer coefficient, is the temperature of the fuel plate, is the temperature of the fluid.

6. The method of claim 5, wherein the coupling method is a rectangular fuel assembly coupling heat coupling method. The method further comprises setting a constraint condition according to the surface heat flux, which comprises the following steps: wherein is an initial assumed heat flux density value, is a second error upper limit value; if the maximum deviation value of the surface heat flux from the initial heat flux value is less than or equal to a second error upper limit value, the coupling iteration is completed, if the maximum deviation value of the surface heat flux from the initial heat flux value is greater than the second error upper limit value, the iteration is not completed.

7. A rectangular fuel assembly coupling heat transfer coupling system, characterized by, The method comprises the following steps: an acquisition module configured to acquire channel number, channel structure parameters, fuel plate number, size, total power, power distribution ratio among the fuel plates, axial power distribution, coolant inlet temperature, total flow, and reference pressure value calculation input parameters; an iteration module configured to perform an iteration calculation of coolant flow distribution characteristics, judge whether the iteration of the coolant flow distribution characteristics is completed, if not, re-perform the iteration calculation of the coolant flow distribution characteristics, if yes, perform an iteration calculation of the heat conduction characteristics of the fuel plate, and judge whether the coupling iteration calculation is completed, if not, re-perform from the iteration calculation of the coolant flow distribution characteristics, if yes, output the coupling calculation result reaching equilibrium of distribution; a main control module connected with the acquisition module and the iteration module, and configured to execute the coupling method for the coupling heat transfer of the rectangular fuel assembly according to any one of claims 1 to 6.

8. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program, and the computer program is executed by the processor to implement the coupling method for the coupling heat transfer of the rectangular fuel assembly according to any one of claims 1 to 6.

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