Method for determining the mixing coefficient of fuel assemblies

Abstract

The embodiments of the present application relate to the field of thermal analysis or optimization technology, and specifically to a method for determining the mixing coefficient of a fuel assembly, comprising: classifying a plurality of channels of the fuel assembly according to the structure of the fuel assembly and the symmetry of the heating power distribution; determining the average outlet temperature value corresponding to each channel group according to the operating condition parameters corresponding to each channel group under each test condition; determining the temperature difference value corresponding to each channel group according to the inlet temperature value of the fuel assembly and the average outlet temperature value corresponding to each channel group under each test condition; determining the power flow ratio under each test condition; determining the relationship between the temperature difference value and the power flow ratio; determining the outlet temperature value of each channel under the converted condition according to the power flow ratio and the relationship under the converted condition; and determining the mixing coefficient according to the outlet temperature value. The method provided by the embodiments of the present application can reduce the amount of calculation, improve the calculation efficiency of the mixing coefficient, and ensure its calculation accuracy.

Description

Technical Field

[0001] The present application relates to the technical field of thermal analysis or optimization, and in particular to a method for determining the mixing coefficient of a fuel assembly. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] The mixing performance between the channels of the fuel assembly is an important research topic in the thermal-hydraulic performance of the core. Superior mixing performance can greatly improve the thermal-hydraulic performance of the core fuel assembly. The parameter used to characterize the mixing performance is the mixing coefficient, which is generally obtained through experimental measurements.

[0004] In the currently commonly used test measurement methods, measurement tests usually need to be carried out in dozens or even hundreds of groups to obtain a large amount of test data, but the current methods for processing these test data are not ideal. Summary of the Invention

[0005] A brief overview of the present application is provided below to provide a basic understanding of certain aspects of the present application. It should be understood that this overview is not an exhaustive overview of the present application. It is not intended to identify key or important portions of the present application, nor is it intended to limit the scope of the present application. Its purpose is simply to present certain concepts in a simplified form as a prelude to the more detailed description that will be discussed later.

[0006] An embodiment of the present application provides a method for determining the mixing coefficient of a fuel assembly, comprising the following steps: S1, obtaining the operating parameters of the fuel assembly under different test conditions, the operating parameters including at least heating power, mass flow value, outlet temperature value, and inlet temperature value of each channel; S2, classifying the multiple channels of the fuel assembly according to the structure of the fuel assembly and the symmetry of the heating power distribution to obtain at least one channel group; S3, determining the average outlet temperature value corresponding to each channel group according to the operating parameters corresponding to each channel group under each test condition; S4, determining the average outlet temperature value corresponding to each channel group according to the inlet temperature value of the fuel assembly under each test condition and the average outlet temperature value corresponding to each channel group. outlet temperature value, determine the temperature difference corresponding to each channel group; S5, determine the power flow ratio under each test condition according to the heating power and mass flow value of the fuel assembly under different test conditions; S6, determine the relationship between the temperature difference and the power flow ratio according to the temperature difference determined in step S4 and the power flow ratio determined in step S5; S7, determine the converted condition from the different test conditions of the fuel assembly, determine its power flow ratio according to the converted condition, and determine the outlet temperature value of each channel under the converted condition according to the power flow ratio and the relationship determined in step S6; S8, determine the mixing coefficient of the fuel assembly according to the outlet temperature value.

[0007] The method provided in the embodiments of the present application can determine the outlet temperature value of each channel under the converted operating condition by determining the relationship between the temperature difference corresponding to each channel group of the fuel assembly and the power flow ratio of the fuel assembly under each test operating condition. Furthermore, the mixing coefficient of the fuel assembly can be determined based on the outlet temperature value. This allows multiple sets of operating parameters of the fuel assembly under different test operating conditions to be converted into one set of converted operating parameters, thereby reducing the amount of calculation and improving the efficiency of the calculation of the mixing coefficient. At the same time, it helps to avoid the influence of relative measurement errors between multiple sets of operating parameters on the calculation results of the mixing coefficient, thereby ensuring the calculation accuracy of the mixing coefficient.

[0008] These and other advantages of the present application will become more apparent through the following detailed description of the preferred embodiments of the present application in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] To further illustrate the above and other advantages and features of the present application, the following detailed description of specific embodiments of the present application is provided in conjunction with the accompanying drawings. The accompanying drawings, together with the detailed description below, are incorporated into and form a part of this specification. Elements with the same function and structure are denoted by the same reference numerals. It should be understood that these drawings depict only typical examples of the present application and should not be construed as limiting the scope of the present application.

[0010] Figure 1 is a flow chart of a method for determining a mixing coefficient of a fuel assembly according to one embodiment of the present application;

[0011] Figure 2 is a curve showing the variation of the error with the maximum temperature difference according to one embodiment of the present application;

[0012] Figure 3 is a curve showing a change in mixing coefficient with maximum temperature difference according to one embodiment of the present application;

[0013] Figure 4 is a schematic diagram of each channel of a fuel assembly according to one embodiment of the present application;

[0014] Figure 5 is a schematic diagram of a relationship between a temperature difference and a power flow ratio according to an embodiment of the present application;

[0015] Figure 6 3 is an error distribution diagram of the ratio of the measured value to the fitted value of the temperature difference under different power flow rates according to an embodiment of the present application.

[0016] It should be noted that the drawings are not necessarily drawn to scale, but are merely shown in a schematic manner that does not affect the reader's understanding. DETAILED DESCRIPTION

[0017] Exemplary embodiments of the present application will be described below with reference to the accompanying drawings. For the sake of clarity and conciseness, not all features of actual implementations are described in the specification. However, it should be understood that many implementation-specific decisions must be made in the process of developing any such actual implementation in order to achieve the developer's specific goals, such as meeting those constraints related to the system and business, and these constraints may vary depending on the implementation. In addition, it should be understood that although the development work may be very complex and time-consuming, it is a routine task for those skilled in the art who benefit from the content of this application.

[0018] It is also necessary to explain here that, in order to avoid obscuring the present application due to unnecessary details, the accompanying drawings only show the device structure and / or processing steps that are closely related to the solution according to the present application, while other details that are not closely related to the present application are omitted.

[0019] It should be noted that, unless otherwise defined, the technical or scientific terms used in this application should have the common meanings understood by persons having ordinary skills in the field to which this application belongs.

[0020] In the description of the embodiments of the present application, “multiple” means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0021] In the related art, in order to determine the mixing coefficient, it is usually necessary to carry out dozens or even hundreds of mixing coefficient measurement tests, and then process each set of test data to obtain the mixing coefficient corresponding to the group, and then calculate the average value of the mixing coefficient corresponding to each group as the final result. For each set of test data, the calculation process of the mixing coefficient is relatively complicated. The more groups of test data there are, the greater the total amount of calculation required for data processing, so the calculation efficiency is relatively low. In addition, there will always be a certain measurement error in the test data obtained in the measurement test. Since the mixing coefficient is calculated based on the test data, the size of the mixing coefficient is closely related to the test data. A small measurement error will result in a large difference between the calculated mixing coefficients. For this reason, the distribution of the mixing coefficients of each channel of the fuel assembly is often very scattered. For example, in the development of the FC2002r relationship, the experimentally measured mixing coefficient ranged from 0.027 to 0.056, with an average value of 0.04. Taking the average value as 1, the error range of the mixing coefficient was -32.5% to 40%, and the maximum value was more than twice the minimum value. It can be seen that the distribution of the mixing coefficient obtained in this way is very scattered and the error is large.

[0022] In order to solve the above technical problems, the present invention provides a method for determining the mixing coefficient of a fuel assembly. Figure 1As shown, the method may at least include the following steps S1 to S8.

[0023] S1. Obtain operating parameters of the fuel assembly under different test conditions. The operating parameters at least include heating power, mass flow rate, outlet temperature, and inlet temperature of each channel.

[0024] S2. Classify the multiple channels of the fuel assembly according to the structure of the fuel assembly and the symmetry of the heating power distribution to obtain at least one channel group.

[0025] S3. Determine the average outlet temperature value corresponding to each channel group according to the operating parameters corresponding to each channel group under each test operating condition.

[0026] S4. Determine the temperature difference corresponding to each channel group based on the fuel assembly inlet temperature value and the average outlet temperature value corresponding to each channel group under each test condition.

[0027] S5. Determine the power-to-flow ratio under each test condition based on the heating power and mass flow rate values ​​of the fuel assembly under different test conditions.

[0028] S6. Determine a relationship between the temperature difference and the power flow ratio based on the temperature difference determined in step S4 and the power flow ratio determined in step S5.

[0029] S7. Determine a converted operating condition from different test operating conditions of the fuel assembly, determine its power flow ratio based on the converted operating condition, and determine the outlet temperature value of each channel under the converted operating condition based on the power flow ratio and the relationship determined in step S6.

[0030] S8. Determine the mixing coefficient of the fuel assembly based on the outlet temperature value.

[0031] The method provided in the embodiments of the present application can determine the outlet temperature value of each channel under the converted operating condition by determining the relationship between the temperature difference corresponding to each channel group of the fuel assembly and the power flow ratio of the fuel assembly under each test operating condition. Furthermore, the mixing coefficient of the fuel assembly can be determined based on the outlet temperature value. This allows multiple sets of operating parameters of the fuel assembly under different test operating conditions to be converted into one set of converted operating parameters, thereby reducing the amount of calculation and improving the efficiency of the calculation of the mixing coefficient. At the same time, it helps to avoid the influence of relative measurement errors between multiple sets of operating parameters on the calculation results of the mixing coefficient, thereby ensuring the calculation accuracy of the mixing coefficient.

[0032] In some embodiments, in step S3, after determining the average outlet temperature value corresponding to each channel group based on the operating parameters corresponding to each channel group under each test condition, the average outlet temperature value corresponding to each channel group can be used to replace the original outlet temperature value of each channel in the channel group, thereby reducing the measurement error; and when the outlet temperature value of any one or more channels obtained by measurement is abnormal, the abnormal situation can be discovered in time and the abnormal outlet temperature value can be discarded.

[0033] In some embodiments, in step S4, the inlet temperature value of the fuel assembly under each test condition can be subtracted from the average outlet temperature value corresponding to each channel group to obtain the difference between each channel group, and the difference is determined as the temperature difference corresponding to each channel group.

[0034] In some embodiments, the inventors of the present application have discovered that when the mixing coefficient is constant, the temperature difference and the power flow ratio have a positive proportional relationship. Therefore, based on the temperature difference determined in step S4 and the power flow ratio determined in step S5, a relationship between the temperature difference and the power flow ratio can be determined. For example, the relationship between the temperature difference and the power flow ratio can be a positive proportional function.

[0035] In some embodiments, in step S7, one test condition may be selected from different test conditions of the fuel assembly and determined as the converted condition.

[0036] In some embodiments, in step S8, the exchange coefficient determined based on the outlet temperature values ​​of each channel under the converted working condition can be used as the average value of the exchange coefficients under different test working conditions, that is, the average mixing coefficient.

[0037] In some embodiments, after step S8, the method may further include determining the error of the obtained mixing coefficient using the temperature difference. The ratio of the measured value to the fitted value of each temperature difference, as well as the average and standard deviation of the ratio of each temperature difference to the fitted temperature value, may be calculated. A closer average value to 1 and a smaller standard deviation indicate a smaller error and higher calculation accuracy. The fitted value of the temperature difference is the difference calculated according to the relationship determined in step S6.

[0038] In some embodiments, step S1 may include the following steps S11 to S13. S11: Testing the fuel assembly under different test conditions; S12: Under each test condition, measuring multiple outlet test points of each channel of the fuel assembly to obtain outlet temperature values ​​of the multiple outlet test points; S13: Under each test condition, measuring the inlet test point of the fuel assembly to obtain the inlet temperature value.

[0039] The embodiment of the present application measures the set inlet test point and multiple outlet test points respectively, so as to obtain the inlet temperature value of the fuel assembly and the outlet temperature value of each channel, and the measurement results are relatively reliable.

[0040] In some embodiments, in step S12, an outlet test point may be set in each channel of the fuel assembly under test to obtain multiple outlet test points for each channel, and then the outlet temperatures of the multiple outlet test points may be measured to obtain the outlet temperature values ​​of the multiple outlet test points.

[0041] Similar to the method of obtaining the outlet temperature value, in step S13, an inlet test point can be set at the inlet of the tested fuel assembly, and the inlet temperature of the inlet test point is measured to obtain the inlet temperature value of the inlet test point.

[0042] In some embodiments, step S8 may include the following steps S81 to S87.

[0043] S81: Determine multiple estimated values ​​of the mixing coefficient based on the converted operating condition parameters.

[0044] S82: Based on each estimated value, determine temperature calculation values ​​of multiple outlet test points.

[0045] S83: Determine an error between the calculated temperature value and the outlet temperature value according to the calculated temperature value and the outlet temperature value in the converted operating condition parameter.

[0046] S84: Calculate the difference between the temperature calculation values ​​of the outlet test points of each channel corresponding to multiple estimated values ​​of different mixing coefficients to determine the maximum temperature difference.

[0047] S85: Fit the error and the maximum temperature difference into a first predetermined function.

[0048] S86: Fitting the mixing coefficient and the maximum temperature difference into a second predetermined function.

[0049] S87: Determine the mixing coefficient of the fuel assembly based on the maximum temperature difference.

[0050] The embodiments of the present application determine the errors between the calculated temperature values ​​of multiple outlet test points of each channel and the outlet temperature values, as well as the maximum value of the differences between the calculated temperature values ​​of the outlet test points of each channel corresponding to multiple estimated values ​​of different mixing coefficients, that is, the maximum temperature difference, and fit the errors and the maximum temperature difference, as well as the mixing coefficient and the maximum temperature difference, respectively. The fitting accuracy is high, and the variation pattern of the error with the maximum temperature difference and the variation pattern of the maximum temperature difference with the mixing coefficient can be accurately obtained, thereby improving the accuracy of the finally determined mixing coefficient. At the same time, it can simplify the determination process of the mixing coefficient, further reduce the amount of calculation, and improve efficiency.

[0051] In some embodiments, in step S81, for each test operating condition, when determining multiple estimated values ​​of the mixing coefficient, multiple different values ​​of the mixing coefficient can be selected within the range that the mixing coefficient may fall into based on the structure and operating parameters of the tested fuel assembly and experience, as multiple estimated values ​​of the mixing coefficient.

[0052] In some embodiments, at least five estimated values ​​of the mixing coefficient may be determined based on the structure and operating parameters of the tested fuel assembly to ensure fitting accuracy, thereby ensuring the accuracy of the ultimately determined mixing coefficient.

[0053] In some embodiments, step S82 may further include: S821, determining the temperature distribution of each channel corresponding to each estimated value of the mixing coefficient based on each estimated value of the mixing coefficient; S822, determining the temperature calculation values ​​of multiple outlet test points of each channel based on the temperature distribution of each channel.

[0054] Specifically, in step S821, each channel of the fuel assembly under test may be modeled one by one, and the temperature distribution of each channel may be obtained through numerical solution.

[0055] In some embodiments, in step S83, the error between the calculated temperature value and the outlet temperature value satisfies the following relationship:

[0056]

[0057] Where s represents the error, and the outlet temperature value of the i-th channel is T ai , the calculated temperature is T pi , the outlet temperature of the jth channel is T aj , the calculated temperature is T pj In this way, the error between the calculated temperature value and the outlet temperature value of multiple outlet test points of the tested fuel assembly is obtained.

[0058] In some embodiments, in step S84, the differences between the calculated temperature values ​​of the outlet test points of each channel corresponding to multiple estimated values ​​of different mixing coefficients may be calculated respectively, and the maximum value of the differences between the calculated temperature values ​​may be determined as the maximum temperature difference.

[0059] In some embodiments, in step S85, the first predetermined function is the following relationship:

[0060]

[0061] Where s represents the error, T β represents the maximum temperature difference, and A1, B1, and C1 are constants. The relationship between the error and the maximum temperature difference can be accurately fitted using this equation to obtain the changing relationship between the error and the maximum temperature difference.

[0062] In some embodiments, the relationship of the first predetermined function is determined as follows: Since the outlet temperature of the i-th channel of the tested fuel assembly is T ai , and the outlet temperature of the jth channel is T aj is a fixed constant, and the error s is a function of the outlet temperature values ​​at multiple outlet test points of the tested fuel assembly. Furthermore, for the same tested fuel assembly, the ratio of the differences between the outlet temperature values ​​at the outlet test points of each channel corresponding to multiple estimated values ​​of the mixing coefficient is a constant value that varies very little with the mixing coefficient. Therefore, the ratio of the differences between the calculated temperature values ​​can be approximated as a constant.

[0063] Therefore, the difference T between the calculated temperature values ​​in formula (1) is pi -T pj You can use k ij T β Substituting into formula (1) we get:

[0064]

[0065] Among them, k ij is the difference between the outlet temperature of the i-th channel and the j-th channel and the maximum temperature difference T β The ratio of is a constant. Therefore, the error s is the maximum temperature difference T β Therefore, the error and the maximum temperature difference are fitted into a quadratic function according to formula (2).

[0066] In some embodiments, A1, B1, and C1 are determined by fitting to improve the fitting accuracy of the error and the maximum temperature difference and accurately reflect the variation of the error with the maximum temperature difference.

[0067] In some embodiments, in step S86, the second predetermined function satisfies the following expression:

[0068]

[0069] Where β represents the mixing coefficient, and A2, B2, and C2 are constants. This relationship can be used to accurately fit the maximum temperature difference to the mixing coefficient, yielding the relationship between the maximum temperature difference and the mixing coefficient.

[0070] In some embodiments, the expression of the second predetermined function is determined based on the following: since the difference in outlet temperature values ​​of multiple outlet test points of each channel decreases as the mixing coefficient increases, but when the mixing coefficient is 0, the difference in outlet temperature values ​​is a certain value rather than tending to positive infinity, the maximum temperature difference is not inversely proportional to the mixing coefficient, and therefore an exponential decay law is assumed; however, when the mixing coefficient tends to positive infinity, the difference in outlet temperature values ​​of multiple outlet test points of each channel tends to a certain value rather than being completely equal, and therefore a constant term is assumed. Therefore, the maximum temperature difference and the mixing coefficient are fitted to the sum of an exponential function and a constant term according to formula (3).

[0071] Specifically, in step S86, when the mixing coefficient and the maximum temperature difference are fitted into the second predetermined function, the equation (3) can be transformed into the following expression by shifting the terms and taking the logarithm:

[0072] ln(T β -C2)=lnA2-B2β (4)

[0073] According to formula (4), first assume a value of C2, and then set ln(T β -C2) is linearly fitted with β and the fitting error R is calculated. 2 , and then adjust the value of C2 according to the fitting error, so that the fitting error R 2 Reaching the minimum, even if R 2 Close to 1, the value of C2 at this time is the fitting of C2. The slope of the straight line obtained by linear fitting is -B2, and the intercept is lnA2.

[0074] In some embodiments, A2, B2, and C2 are determined by fitting to improve the fitting accuracy of the maximum temperature difference and the mixing coefficient, and accurately reflect the variation of the maximum temperature difference with the mixing coefficient.

[0075] In some embodiments, step S87 may include: when s takes a minimum value, determining the maximum temperature difference using a first predetermined function; and determining the mixing coefficient of the fuel assembly based on the maximum temperature difference and a second predetermined function.

[0076] In an embodiment of the present application, when s takes a minimum value, a first predetermined function is used to determine the maximum temperature difference, and the mixing coefficient of the fuel assembly is determined based on the maximum temperature difference and the second predetermined function. The mixing coefficient of the fuel assembly is determined by utilizing the variation pattern of the error obtained by fitting with the maximum temperature difference and the variation pattern of the maximum temperature difference with the mixing coefficient, thereby avoiding multiple trial calculations and iterations and reducing tedious and complicated workload.

[0077] In some embodiments, when the maximum temperature difference is determined by using the first predetermined function, the maximum temperature difference T when s takes the minimum value can be obtained based on the properties of the quadratic function and the fitting coefficients A1, B1, and C1.β The value of is as follows:

[0078]

[0079] In some embodiments, when determining the mixing coefficient of the fuel assembly based on the maximum temperature difference and the second predetermined function, the expression for the mixing coefficient β can be obtained by first inversely solving equation (3), as shown below:

[0080]

[0081] Then, the maximum temperature difference T when s takes the minimum value determined by the first predetermined function is used. β Substituting into formula (6), the mixing coefficient β is calculated.

[0082] The following is a specific example to further illustrate the process of determining the mixing coefficient of a fuel assembly using the method of the present application.

[0083] Example 1

[0084] First, under different test conditions, the fuel assembly was tested in a 5×5 square arrangement of rods, and then the operating parameters of the fuel assembly under different test conditions were obtained. In this embodiment, a total of 136 sets of tests were conducted.

[0085] Second, based on the structure of the fuel assembly and the symmetry of the heating power distribution, the 16 channels of the fuel assembly can be divided into three channel groups. Figure 4 As shown, for the convenience of description and understanding, the 16 channels are marked as M 1,1 To M 4,4 The first channel group includes 4 channels, namely M 2,2 、M 2,3 、M 3,2 and M 3,3 ; The second channel group includes 4 channels, namely M 1,1 、M 1,4 、M 4,1 and M 4,4 ; The third channel group includes 8 channels, which are the remaining channels except the channels included in the first channel group and the second channel group.

[0086] Third, according to the operating parameters corresponding to each channel group under each test condition, the average outlet temperature value corresponding to each channel group can be determined.

[0087] Fourth, based on the fuel assembly inlet temperature value and the average outlet temperature value corresponding to each channel group under each test condition, the temperature difference corresponding to each channel group can be determined.

[0088] Fifth, based on the heating power and mass flow rate values ​​of the fuel assembly under different test conditions, the power-flow ratio under each test condition can be determined.

[0089] Sixth, as Figure 5 As shown, according to the determined temperature difference and power flow ratio, the temperature difference and power flow ratio can be fitted. Fitting equations a, b, and c are the fitting results corresponding to the three channel groups. Among them, the fitting equation a is: y = 1.3125x, and the fitting error R 2 =0.9929; the fitting relationship b is: y = 0.9731x, the fitting error R 2 =0.9943; the fitting relationship c is: y = 0.7672x, the fitting error R 2 =0.9921. Where x represents the mass flow rate and y represents the temperature difference. Figure 5 As shown in the figure, the fitting accuracy of each channel group is relatively high.

[0090] Seventh, select pressure 15MPa, inlet temperature 100℃, mass flow density 2800kg / m 2 s, heat flux density of hot rod 0.65MW / m 2 For the converted working conditions, it can be determined that the outlet temperature values ​​of each channel group under the converted working conditions are 153.73℃, 168.16℃, and 191.93℃ respectively.

[0091] Eighth, based on the outlet temperature values ​​of each channel under the converted working conditions, the mixing coefficient can be determined to be 0.01683.

[0092] In some embodiments, according to the calculation method in the prior art, it is necessary to calculate the mixing coefficients corresponding to 136 groups of data respectively, and the range of the mixing coefficients is 0.007 to 0.022, and then the average value of the mixing coefficients is calculated to be 0.01655. The error between the calculation result of the mixing coefficient in the embodiment of the present application and the calculation result obtained by the calculation method in the prior art is only 1.7%, which shows the correctness of the method provided in the embodiment of the present application. Furthermore, the method provided in the embodiment of the present application only calculates the mixing coefficient once, which can reduce the amount of calculation to less than 1% of the calculation method in the prior art, greatly reducing the amount of calculation.

[0093] In some embodiments, regarding the error analysis of the final blending coefficient, the blending coefficient calculated according to the relevant technology ranges from 0.007 to 0.022, with an average value of 0.01655 and a relative error range of -57.7% to 32.9%, which is very dispersed. Figure 6As shown, according to the method provided in the embodiment of the present application, the measured and fitted values ​​of the temperature differences calculated range from 0.92 to 1.08, with an average value of 0.995, very close to 1, a relative error range of only -8% to 8%, and a standard deviation of only 2.9%. This shows that the method provided in the embodiment of the present application has a small error and high accuracy.

[0094] The following is a specific example to further illustrate the process of determining the mixing coefficient of a fuel assembly based on the outlet temperature value using the method in this application.

[0095] Example 2

[0096] (1) Based on the structure and operating parameters of the tested fuel assembly, the possible range of the mixing coefficient was determined empirically, and six values ​​of 0.006, 0.01, 0.014, 0.018, 0.022, and 0.026 were selected as multiple estimated values ​​of the mixing coefficient.

[0097] (2) Based on each estimated value of the mixing coefficient, determine the temperature distribution of each channel corresponding to each estimated value of the mixing coefficient; and determine the temperature calculation values ​​of multiple outlet test points of each channel according to the temperature distribution.

[0098] (3) According to the temperature calculation value and the outlet temperature value, use formula (1) to determine the error between the temperature calculation value and the outlet temperature value.

[0099] (4) Calculating the difference between the temperature calculation values ​​of the outlet test points of each channel corresponding to multiple estimated values ​​of different mixing coefficients, and determining the maximum value of the difference between the temperature calculation values ​​as the maximum temperature difference.

[0100] (5) Compare the error s with the maximum temperature difference T β Specifically, according to formula (2), the error s and the maximum temperature difference T are obtained. β The changing relationship is as follows:

[0101]

[0102] Among them, the fitting error R 2 =0.9997. According to the change relationship, the error s is obtained as the maximum temperature difference T β The change curve of Figure 2 shown.

[0103] (6) The mixing coefficient β and the maximum temperature difference T β According to formula (3), the second predetermined function is fitted to obtain the mixing coefficient β and the maximum temperature difference T β The relationship between the mixing coefficient β and the maximum temperature difference T is obtained based on the relationship between the mixing coefficient β and the maximum temperature difference T. β The change curve of Figure 3 shown.

[0104] (VII) According to the fitting coefficients 35.118 and -377.32, according to formula (5), when s takes the minimum value, the maximum temperature difference T β is 5.372℃; and then substituting it into formula (6), the mixing coefficient β of the fuel assembly is calculated to be 0.01694.

[0105] Regarding the embodiments of the present application, it should also be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other to obtain new embodiments.

[0106] The above description is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. The protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A method for determining the mixing coefficient of a fuel assembly, characterized in that: The following steps are involved: S1. Obtaining operating parameters of the fuel assembly under different test conditions, wherein the operating parameters include at least heating power, mass flow rate, outlet temperature, and inlet temperature of each channel; S2. Classifying the plurality of channels of the fuel assembly according to the structure of the fuel assembly and the symmetry of the heating power distribution to obtain at least one channel group; S3. Determine the average outlet temperature value corresponding to each channel group according to the operating condition parameters corresponding to each channel group under each test condition; S4. Determine the temperature difference corresponding to each channel group according to the inlet temperature value of the fuel assembly and the average outlet temperature value corresponding to each channel group under each test condition; S5. determining a power-flow ratio under each test condition based on the heating power and mass flow values ​​of the fuel assembly under different test conditions; S6. Determine a relationship between the temperature difference and the power flow ratio based on the temperature difference determined in step S4 and the power flow ratio determined in step S5; S7. Determine a converted operating condition from the different test operating conditions of the fuel assembly, determine a power flow ratio based on the converted operating condition, and determine an outlet temperature value of each channel under the converted operating condition based on the power flow ratio and the relationship determined in step S6; S8. Determine the mixing coefficient of the fuel assembly according to the outlet temperature value; The S8 step includes: S81: Determine multiple estimated values ​​of the mixing coefficient according to the converted operating condition parameters; S82: Determine calculated temperature values ​​of a plurality of outlet test points based on each estimated value; S83: determining an error between the temperature calculation value and the outlet temperature value according to the temperature calculation value and the outlet temperature value in the converted operating condition parameter; S84: Calculating the difference between the temperature calculation values ​​of the outlet test points of each channel corresponding to multiple estimated values ​​of different mixing coefficients to determine the maximum temperature difference; S85: Fitting the error and the maximum temperature difference into a first predetermined function; S86: Fitting the mixing coefficient and the maximum temperature difference into a second predetermined function; S87: Determine a mixing coefficient of the fuel assembly according to the maximum temperature difference; In step S85, the first predetermined function is the following relational expression: ， Where s represents the error, T β Indicates the maximum temperature difference, A1, B1, C1 are constants; In step S86, the second predetermined function satisfies the following expression: ， Wherein, β represents the mixing coefficient, and A2, B2, and C2 are constants.

2. The method according to claim 1, characterized in that The S1 step includes: S11. Testing the fuel assembly under different test conditions; S12. Under each of the test conditions, measuring multiple outlet test points of each channel of the fuel assembly to obtain outlet temperature values ​​of the multiple outlet test points; S13. Under each of the test conditions, measure the inlet test point of the fuel assembly to obtain the inlet temperature value.

3. The method according to claim 1, characterized in that In step S83, the error satisfies the following relationship: ， Where s represents the error, and the outlet temperature value of the i-th channel is T ai , the calculated temperature is T pi , the outlet temperature of the jth channel is T aj , the calculated temperature is T pj .

4. The method according to claim 1, wherein The A1, B1, and C1 are determined by fitting.

5. The method according to claim 1, wherein The A2, B2, and C2 are determined by fitting.

6. The method according to claim 1, characterized in that The S87 step includes: When s takes a minimum value, determining the maximum temperature difference using the first predetermined function; A mixing coefficient of the fuel assembly is determined according to the maximum temperature difference and the second predetermined function.

7. The method according to claim 1, characterized in that In step S6, the relationship between the temperature difference and the power flow ratio is a directly proportional function.

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