Non-uniformly distributed CHF number table construction method and system, and medium

Abstract

The invention relates to the technical field of reactor thermal hydraulic power, in particular to a method and system for constructing a non-uniformly distributed CHF number table, and media and critical heat flux (CHF) are key input parameters of a reactor thermal design criterion and are also keys for characterizing the heat exchange limit of a reactor core. And the prediction precision of the CHF can be improved based on table interpolation calculation. The invention provides a nonlinear CHF number table construction method for high-precision interpolation calculation based on a number table from a nonlinear influence rule of main thermal parameters on CHF. The core content is a specific determination method of the connotation, the form and the non-uniform distribution of the number table. According to the method, the CHF high-precision calculation based on the data table can be supported, meanwhile, the total amount of data needed by the data table is reduced, the experiment cost is saved, and therefore the engineering purposes of assisting in improving the CHF calculation precision and releasing the reactor core design allowance are achieved.

Description

Technical Field

[0001] The invention relates to the field of reactor thermal hydraulic technology, and in particular to a method and system for constructing a non-uniformly distributed CHF table, and a medium. Background Art

[0002] Critical heat flux (CHF) is a key input parameter of reactor thermal design criteria and is also the key to characterizing the core heat transfer limit.

[0003] Improving the prediction accuracy of CHF can reduce the design penalty factor and release the design margin. At present, the engineering mainly uses the fitting relationship based on experiments to calculate CHF. The functional form of the relationship is artificially assumed, and due to the limited number of undetermined coefficients, there must be a significant deviation of about ±20% between the fitting relationship and the experimental data, which makes the design penalty factor larger. At the same time, when the experimental data is further expanded, the relationship is difficult to cover and must be refitted. Therefore, low calculation accuracy and difficulty in extrapolation are inherent defects of the fitting relationship.

[0004] When there are enough CHF experimental data points, CHF can be calculated directly by interpolation based on the table. In theory, the interpolation accuracy can continue to improve with data encryption; however, the total amount of data in the multidimensional table increases with the data encryption exponent. Summary of the invention

[0005] The purpose of the present invention is to provide a method and system for constructing a non-uniformly distributed CHF table, and a 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 method for constructing a non-uniformly distributed CHF number table, comprising:

[0008] Step 1: Obtain the midpoint of the table and determine the mass flow rate through the midpoint of the table;

[0009] Step 2: Step the mass flow rate, keep other parameters unchanged, and obtain mass flow rates of different sizes. For mass flow rates of different sizes, change the critical steam content value, and keep other parameters unchanged;

[0010] Step 3: Based on step 1 and step 2, increase or decrease the pressure value, and keep other parameters unchanged;

[0011] Step 4: Determine the new thermal diameter;

[0012] Step 5: Based on the determined mass flow rate, critical vapor fraction value, pressure value and thermodynamic diameter, the corresponding CHF is obtained through experiments to obtain a complete non-uniformly distributed CHF table.

[0013] Preferably, obtaining the midpoint of the table includes taking the rated design condition of the core as the center point of the table, and the thermal diameter is the value of a typical coolant sub-channel:

[0014] CHF0={p0,G0,xe0,Dh0}

[0015] Where CHF0 is the center point of the table, p0 represents the rated operating pressure of the core, G0 represents the average mass flow rate at the rated operating condition, xe0 represents the steam content at the hot channel outlet, and Dh0 represents the thermal diameter of the typical sub-channel.

[0016] Preferably, the other parameters remaining unchanged include:

[0017] A designated value is set so that when the critical vapor fraction value and the pressure value change, the difference in CHF values ​​between two adjacent points in the CHF table is not greater than the designated value, and the designated value is recorded as ΔCHF.

[0018] Preferably, determining the new thermal diameter comprises:

[0019]

[0020] Where Dh0 represents the typical sub-channel thermal diameter, Dh is the new sub-channel thermal diameter, CHF0 is the center point value of the table, and ΔCHF is the difference in CHF between two specified adjacent points.

[0021] Preferably, the interpolation of the non-uniformly distributed CHF table includes:

[0022] Based on the given input parameters, a table is used for interpolation calculation to obtain a CHF calculation value of the corresponding working condition. The calculation result of the interpolation function does not exceed the maximum value of the four corner points in the CHF table and is not lower than the minimum value.

[0023] Preferably, the interpolation function comprises:

[0024] Calculate the Euclidean distance between the point to be interpolated and its adjacent points, and obtain the CHF value of the point through interpolation.

[0025] In a second aspect, the present invention further provides a system for constructing a non-uniformly distributed CHF table, comprising:

[0026] The data determination module is configured to obtain the midpoint of the number table, determine the mass flow rate through the midpoint of the number table; step the mass flow rate, keep other parameters unchanged, obtain mass flow rates of different sizes, change the critical steam content value for the mass flow rates of different sizes, and keep other parameters unchanged; increase or decrease the pressure value based on step one and step two, and keep other parameters unchanged; determine a new thermal diameter;

[0027] The table building module is configured to conduct tests on these operating conditions to obtain CHF values ​​based on the determined mass flow rate, critical steam fraction value, pressure value and thermodynamic diameter, thereby obtaining a complete non-uniform distribution CHF table.

[0028] In a third aspect, the present invention further provides a computer-readable storage medium storing a computer program, wherein the computer program, when executed by a processor, implements the above-mentioned method for constructing a non-uniformly distributed CHF number table.

[0029] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0030] The method provided by the present invention mainly includes obtaining the midpoint of the table, determining the mass flow rate through the midpoint of the table; stepping the mass flow rate to obtain mass flow rates of different sizes, changing the critical steam content value for mass flow rates of different sizes, and increasing or decreasing the pressure value; determining a new thermal diameter, and based on the determined mass flow rate, critical steam content value, pressure value and thermal diameter, conducting experiments on these working conditions to obtain CHF values, and obtaining a complete non-uniformly distributed CHF table. The above method supports high-precision calculation of CHF based on the table, while reducing the total amount of data and saving experimental costs, thereby achieving the engineering purpose of helping to improve the calculation accuracy of CHF and releasing the core design margin. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] 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.

[0032] Figure 1 It is a schematic diagram of the nonlinear relationship between CHF-p of the present invention.

[0033] Figure 2 It is a schematic diagram of the process of constructing the non-uniform number table of the present invention. DETAILED DESCRIPTION

[0034] 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.

[0035] 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.

[0036] 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.

[0037] The existing CHF tables have evenly distributed parameters and small spacing between data points, and the data size is very large, mainly due to the large number of CHF experimental results for circular tubes in the public literature. The construction of such a large-scale table is unimaginable for some engineering projects with special channels, difficulty in obtaining public data, and strict experimental and funding constraints.

[0038] Figure 1 The nonlinear effect of pressure on CHF is shown. This inspires us to optimize the table based on the parameter variation law of CHF itself: that is, in the large slope area or near the inflection point, the experimental conditions can be increased; otherwise, the experimental conditions can be greatly reduced.

[0039] The present invention provides a method for constructing a non-uniformly distributed CHF number table, comprising:

[0040] Step 1: Obtain the midpoint of the table and determine the mass flow rate through the midpoint of the table;

[0041] Specifically, obtaining the midpoint of the table includes taking the rated design condition of the core as the center point of the table, and the thermal diameter is the value of a typical coolant subchannel:

[0042] CHF0={p0,G0,xe0,Dh0}

[0043] Where CHF0 is the center point of the table, p0 represents the rated operating pressure of the core, G0 represents the average mass flow rate at the rated operating condition, xe0 represents the steam content at the hot channel outlet, and Dh0 represents the thermal diameter of the typical sub-channel.

[0044] Step 2: Step the mass flow rate, keep other parameters unchanged, and obtain mass flow rates of different sizes. For mass flow rates of different sizes, change the critical steam content value, and keep other parameters unchanged;

[0045] The mass flow rate G is gradually increased or decreased, and other parameters remain unchanged, so that the CHF value between two adjacent points is not much different from the specified value, such as 15%. The difference ΔCHF can be approximately estimated using the existing relationship.

[0046] Similarly, by changing the critical vapor fraction value, other parameters remain unchanged so that the difference in CHF value between two adjacent points (the upper and lower points in the figure) is no greater than a specified value, such as 15%. Since the influence of the critical vapor fraction value is related to G, the resulting dot matrix is ​​non-uniformly distributed.

[0047] Step 3: Based on step 1 and step 2, increase or decrease the pressure value, and keep other parameters unchanged;

[0048] Increase or decrease the pressure p, and keep other parameters unchanged. Make the difference between the CHF values ​​of two adjacent layers not greater than a specified value, such as 15%. Since the influence of p is nonlinear, the lattice is non-uniformly distributed with respect to pressure.

[0049] There is an inflection point in the pressure effect, so the density near the inflection point can be appropriately increased.

[0050] Step 4: Determine the new thermal diameter;

[0051] Specifically, the design needs to examine the impact of flow channel deformation or flow channel size change on CHF. Usually, only three different thermal diameters need to be covered. The new thermal diameter can be determined using the following formula, which includes:

[0052]

[0053] Where Dh0 represents the typical sub-channel thermal diameter, Dh is the new sub-channel thermal diameter, CHF0 is the center point value of the table, and ΔCHF is the difference in CHF between two specified adjacent points.

[0054] If the CHF ratio is taken as 1.15, the enlarged thermal diameter can be obtained; if the ratio is taken as 0.85, the reduced thermal diameter can be obtained.

[0055] Step 5: Based on the determined mass flow rate, critical vapor fraction value, pressure value and thermodynamic diameter, conduct experiments to determine the CHF under the corresponding operating conditions to obtain a complete non-uniformly distributed CHF table.

[0056] In practical applications, a 10% to 20% difference in CHF between adjacent points is feasible, which mainly depends on the requirements for interpolation accuracy and the control of experimental costs.

[0057] The method provided by the present invention mainly includes obtaining the midpoint of the table, determining the mass flow rate through the midpoint of the table; stepping the mass flow rate to obtain mass flow rates of different sizes, changing the critical steam content value for mass flow rates of different sizes, and increasing or decreasing the pressure value; determining a new thermal diameter, and based on the determined mass flow rate, critical steam content value, pressure value and thermal diameter, conducting experiments to determine the CHF under the corresponding working conditions to obtain a complete non-uniformly distributed CHF table. Use the table to carry out interpolation calculations, etc. The above method realizes high-precision calculation of CHF based on the table, while reducing the total amount of data and saving experimental costs, thereby achieving the engineering purpose of helping to improve the calculation accuracy of CHF and releasing the core design margin.

[0058] Based on the above, it also includes:

[0059] Taking the rated operating condition as the origin and keeping other parameters unchanged, firstly, the mass flow rate G is stepped, and the advancing direction is shown in Figure 2 The horizontal red line in the figure is then changed for different G values, and the critical steam content value xe is changed to obtain two sets of points, and so on. Since the setting of the points is controlled by the change amplitude of CHF, the spacing between the points is different, and the distribution obtained is non-uniform, which greatly saves the number of experiments and costs.

[0060] Figure 2 The red quadrilateral and green diagonal pattern in the middle are used to illustrate the interpolation operation based on the table. Since the CHF variation between adjacent data points is very small (such as 15%), it can be considered that the CHF variation within this small quadrilateral area is monotonic; if a suitable interpolation function is selected and the result is required to be bounded (the interpolation calculation result does not exceed the maximum value of the four corner points and is not lower than the minimum value), it is easy to strictly prove that the interpolation error is far less than 15%.

[0061] In an exemplary embodiment of the present invention, interpolating a non-uniformly distributed CHF table includes:

[0062] Based on the given input parameters, a table is used for interpolation calculation to obtain the CHF calculation value of the corresponding working condition. The table is constructed. The table represents the mapping relationship between the independent variable and the function value CHF. The key point of the present invention is to achieve the non-uniform distribution of the dot matrix by controlling the CHF difference of adjacent points. The non-uniform means that the step length between each independent variable, that is, the interval, is not equal. Figure 2 and attached Figure 1 . This is the core principle of the invention;

[0063] Application of number tables. At this time, given the independent variables, {p, G, xe, Dh}, based on the number table, the interpolation algorithm is used to obtain the CHF calculation value (interpolation result) under the corresponding working condition. The calculation result of the interpolation function does not exceed the maximum value of the four corner points in the CHF number table, and is not lower than the minimum value.

[0064] Specifically, the interpolation function includes.

[0065] The interpolation calculation algorithm adopted by the present invention is the "Euclidean distance inverse interpolation method". First, the Euclidean distance between the point to be interpolated and the adjacent point is calculated:

[0066] s i =[(pp i ) 2 +(GG i ) 2 +(xe-xe i ) 2 +(Dh-Dh i ) 2 ] 0.5

[0067] Where the subscript i represents the i-th adjacent point near the interpolation point, and is the Euclidean distance between the interpolation point and the i-th adjacent point.

[0068] In the formula, s i is the Euclidean distance, p is the core pressure interpolation point, p i is the ith adjacent point near the core pressure interpolation point, G is the average mass flow rate interpolation point, G i is the ith adjacent point near the average mass flow rate interpolation point, xe is the steam content interpolation point at the hot channel outlet, and xe i is the i-th adjacent point near the interpolation point of the steam content at the hot channel outlet, Dh is the interpolation point of the thermal diameter of the typical subchannel, and Dh i is the i-th adjacent point near the interpolation point of the thermal diameter of a typical sub-channel.

[0069] The total distance is defined as:

[0070]

[0071] Where n represents the number of adjacent points and s is the total Euclidean distance.

[0072] Weighting coefficient λ i Defined as:

[0073]

[0074] The interpolation calculation shows that the CHF value at this point is:

[0075]

[0076] In the formula, CHF i is the adjacent CHF value to be interpolated.

[0077] In a second aspect, the present invention further provides a system for constructing a non-uniformly distributed CHF table, comprising:

[0078] The data determination module is configured to obtain the midpoint of the number table, determine the mass flow rate through the midpoint of the number table; step the mass flow rate, keep other parameters unchanged, obtain mass flow rates of different sizes, change the critical steam content value for the mass flow rates of different sizes, and keep other parameters unchanged; increase or decrease the pressure value based on step one and step two, and keep other parameters unchanged; determine a new thermal diameter;

[0079] The table construction module is configured to conduct experiments to determine the CHF under the corresponding working conditions based on the determined mass flow rate, critical steam content value, pressure value and thermal diameter, so as to obtain a complete non-uniform distribution CHF table. The table interpolation calculation module. According to the constructed non-uniform table and the specified input, multi-dimensional interpolation calculation is carried out to obtain the CHF calculation value of the corresponding input.

[0080] 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.

[0081] 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.

[0082] 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 method for constructing a non-uniformly distributed CHF table, characterized in that: include: Step 1: Obtain the midpoint of the table and determine the mass flow rate through the midpoint of the table; Step 2: Step the mass flow rate, keep other parameters unchanged, and obtain mass flow rates of different sizes; for each mass flow rate of different sizes, change the critical steam content value, and keep other parameters unchanged; Step 3: Based on step 1 and step 2, increase or decrease the pressure value, and keep other parameters unchanged; Step 4: Determine the new thermal diameter; Step 5: Based on the determined mass flow rate, critical vapor fraction value, pressure value and thermodynamic diameter, the CHF value is obtained through experiments, thereby obtaining a complete non-uniformly distributed CHF table.

2. The method for constructing a non-uniformly distributed CHF table according to claim 1, characterized in that: The method of obtaining the midpoint of the table includes taking the rated design condition of the core as the center point of the table, and the thermal diameter is the value of a typical coolant sub-channel: CHF0={p0,G0,xe0,Dh0} Where CHF0 is the center point of the table, p0 represents the rated operating pressure of the core, G0 represents the average mass flow rate at the rated operating condition, xe0 represents the steam content at the hot channel outlet, and Dh0 represents the thermal diameter of the typical sub-channel.

3. The method for constructing a non-uniformly distributed CHF table according to claim 2, characterized in that: Also includes step lengths for individual parameters: Set the specified value so that when the mass flow rate, critical vapor fraction value or pressure value changes, the difference in CHF values ​​between two adjacent points in the CHF table is not greater than the specified value.

4. The method for constructing a non-uniformly distributed CHF table according to claim 3, characterized in that: Determining the new thermal diameter includes: Where Dh0 represents the typical sub-channel thermal diameter, Dh is the new sub-channel thermal diameter, CHF0 is the center point value of the table, and ΔCHF is the difference in CHF between two specified adjacent points.

5. The method for constructing a non-uniformly distributed CHF table according to claim 3, characterized in that: The interpolation of the non-uniformly distributed CHF table includes: According to the input parameters and the constructed table, the corresponding CHF calculation results are obtained through the interpolation function; The calculation result of the interpolation function does not exceed the maximum value of the four corner points in the CHF table and is not lower than the minimum value.

6. The method for constructing a non-uniformly distributed CHF table according to claim 3, characterized in that: The interpolation function includes: Calculate the Euclidean distance between the point to be interpolated and its adjacent points, and obtain the CHF value of the point through interpolation.

7. The method for constructing a non-uniformly distributed CHF table according to claim 6, characterized in that: The calculating of the Euclidean distance between the point to be interpolated and the adjacent point comprises: s i =[(pp i ) 2 +(GG i ) 2 +(is-is i ) 2 +(D-D i ) 2 ] 0.5 In the formula, s i is the Euclidean distance, p is the core pressure interpolation point, p i is the ith adjacent point near the core pressure interpolation point, G is the average mass flow rate interpolation point, G i is the ith adjacent point near the average mass flow rate interpolation point, xe is the steam content interpolation point at the hot channel outlet, and xe i is the i-th adjacent point near the interpolation point of the steam content at the hot channel outlet, Dh is the interpolation point of the thermal diameter of the typical subchannel, and Dh i is the i-th adjacent point near the interpolation point of the thermal diameter of a typical sub-channel.

8. The method for constructing a non-uniformly distributed CHF table according to claim 7, characterized in that: The total distance is also: Where n represents the number of adjacent points and s is the total Euclidean distance.

9. A system for constructing a non-uniformly distributed CHF table, characterized in that: include: The data determination module is configured to obtain the midpoint of the number table, determine the mass flow rate through the midpoint of the number table; step the mass flow rate, keep other parameters unchanged, obtain mass flow rates of different sizes, change the critical steam content value for the mass flow rates of different sizes, and keep other parameters unchanged; increase or decrease the pressure value based on step one and step two, and keep other parameters unchanged; determine a new thermal diameter; A table building module is configured to obtain a complete non-uniformly distributed CHF table by experimentally obtaining a corresponding CHF based on the determined mass flow rate, critical vapor fraction value, pressure value and thermodynamic diameter; The table interpolation calculation module performs multi-dimensional interpolation calculation based on the constructed non-uniform table and the given input to obtain the CHF calculation value corresponding to the input; A main control module is connected to the data determination module and the number table construction module, and is used to execute a non-uniformly distributed CHF number table construction 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, the method for constructing a non-uniformly distributed CHF number table according to any one of claims 1 to 8 is implemented.

Images