A heat transfer characteristics extraction method for heat exchanger performance modeling and simulation

Abstract

The present invention discloses a heat exchange characteristic extraction method for heat exchanger performance modeling and simulation, which relates to the technical field of heat exchanger performance modeling and simulation. The steps are as follows: S1, based on the similarity theory, the heat exchanger similarity criterion is obtained by analysis; S2, based on the heat exchanger similarity criterion, the heat transfer equation and the Fanning equation are combined to analyze the unit temperature difference heat transfer power P w and the heat exchanger corrected resistance coefficient F as characteristic parameters to characterize the performance of the heat exchanger; S3, given the combination of incoming flow parameters, extract the characteristics of the heat exchanger based on the traditional intercooling heat exchanger thermal simulation model and generate the heat exchanger heat transfer characteristic diagram; S4, calculate the heat exchanger performance based on the extracted heat exchanger heat transfer characteristic diagram. The heat transfer characteristic extraction method for heat exchanger performance modeling and simulation mentioned in this application has higher calculation efficiency while ensuring the calculation accuracy, and the general characteristic diagram obtained by extraction can be generalized and applied to the performance simulation of engine heat exchanger components.

Description

Technical Field

[0001] The invention relates to the field of heat exchanger performance modeling and simulation, and in particular to a heat exchange characteristic extraction method for heat exchanger performance modeling and simulation. Background Art

[0002] Precooling technology has opened up an effective way to solve the thrust gap problem of turbine-based combined cycle (TBCC) engines. Heat exchangers have been widely used in high-speed precooling / intercooling engines. However, as the core component for realizing energy exchange, its performance modeling and simulation is still a challenge. Precooling technology is inseparable from practical and reliable heat exchanger design methods, but the current heat exchanger design methods have defects: on the one hand, a large number of design method studies and experiments on heat exchanger components have been carried out, but these studies are limited to the component level and cannot effectively couple with other engine components for design and rapid performance evaluation. On the other hand, at the overall performance modeling level, in the overall performance modeling of engines involving heat exchange cooling, traditional heat exchanger simulation methods usually directly set the heat transfer degree and total pressure recovery coefficient of the heat exchanger, and then calculate the heat transfer of the hot and cold working fluids of the heat exchanger according to the definition of heat transfer degree and the principle of energy conservation. However, the premise of this simulation method is that the given heat exchanger performance meets the design feasibility by default, ignoring the constraints and influences of the intercooler installation space and the parameters of the hot and cold working fluids on the intercooler design. In addition, the fixed heat transfer degree and total pressure recovery coefficient cannot accurately simulate the actual heat transfer performance changes of the heat exchanger under different working conditions.

[0003] The most effective method to derive and establish a thermal simulation model of an indirect heat exchanger based on the heat transfer equation and the heat balance equation is currently the most effective method. It can comprehensively consider the design boundary conditions of the heat exchanger and better simulate the actual heat transfer performance of the heat exchanger under different working conditions. At the same time, compared with CFD simulation, the simulation model established by this method has a higher calculation speed.

[0004] However, its calculation still involves a large number of guessing iterations. Compared with other component-level performance modules of aircraft engines, the heat exchanger performance simulation model established by this method still has a relatively slow calculation speed, which is not conducive to the repeated iterative calculation of the overall engine performance or the large-scale calculation of the optimization algorithm.

[0005] Therefore, it is necessary to further study the simulation method with higher calculation efficiency and maintained calculation accuracy based on the thermal simulation calculation model. Summary of the invention

[0006] The purpose of the present invention is to provide a heat transfer characteristic extraction method for heat exchanger performance modeling and simulation, the steps are as follows:

[0007] S1. Analyze and obtain the similarity criterion of heat exchanger based on similarity theory;

[0008] S2. Based on the heat exchanger similarity criterion, combined with the heat transfer equation and Fanning equation analysis, the unit temperature difference heat transfer power P w and the heat exchanger corrected resistance coefficient F as characteristic parameters characterizing the performance of the heat exchanger;

[0009] S3, obtaining geometric information of the heat exchanger, given different cold and hot end airflow inlet parameters to form different incoming flow parameter combinations, extracting characteristics of the heat exchanger based on the traditional intercooling heat exchanger thermal simulation model and generating a heat exchange characteristic diagram of the heat exchanger;

[0010] S4. Calculate the heat exchanger performance based on the extracted heat exchanger heat transfer characteristic diagram, where the heat exchanger performance includes heat transfer performance and flow resistance loss performance.

[0011] Preferably, the heat exchanger similarity criterion in S1 includes a first heat exchanger similarity criterion and a second heat exchanger similarity criterion;

[0012] The first heat exchanger similarity criterion is that when the Reynolds number of the hot and cold ends of two heat exchangers of the same size is c 、Re h When the corresponding values ​​are equal, the flow loss performance of the two heat exchangers is equal, and the Reynolds number Re is the similarity criterion number of the heat exchanger;

[0013] The second heat exchanger similarity criterion is that when the thermal derivatives E of the hot and cold ends of two heat exchangers of the same size are c 、E h When the corresponding values ​​are equal, the heat transfer performance of the two heat exchangers is equal, and the thermal derivative is the similarity criterion number of the heat exchanger.

[0014] Preferably, in S2, based on the heat exchanger similarity criterion, combined with the heat transfer formula and Fanning formula analysis, the unit temperature difference heat transfer power P w The specific process of using the heat exchanger corrected resistance coefficient F as a performance characteristic parameter to characterize the heat exchanger is:

[0015] For the heat transfer performance of the heat exchanger, the heat transfer equation (1) can be used to derive equation (2): K(E c ,E h )AΔT m =qc p |T2-T1|=Q (1);

[0016]

[0017] Among them, P w is the heat transfer power per unit temperature difference of the heat exchanger, K is the total heat transfer coefficient of the heat exchanger calculated using the thermal derivative as the independent variable, E c is the cold end thermal derivative, E h is the thermal derivative of the hot end, A is the heat exchange area, ΔTm is the logarithmic mean temperature difference, q is the fluid flow rate, c p is the specific heat capacity at constant pressure, T2 is the temperature after heat exchange, T1 is the temperature before heat exchange, and Q is the heat exchange amount.

[0018] For the flow resistance loss performance of the heat exchanger, equation (4) can be derived from Fanning equation (3):

[0019]

[0020]

[0021] Where Δp is the pressure loss, S is the length of the heat exchanger pipe, and d e is the diameter of the heat exchanger pipe, u is the fluid flow rate, A is the cross-sectional area of ​​the heat exchanger pipe, f is the heat exchanger resistance coefficient calculated by the single-valued function of the Reynolds number Re, q is the fluid flow rate, ρ is the fluid density, and F is the corrected resistance coefficient of the heat exchanger.

[0022] Preferably, in S3, the geometric information of the heat exchanger is obtained, different cold and hot end airflow inlet parameters are given to form different incoming flow parameter combinations, and the specific contents of extracting the characteristics of the heat exchanger and generating the heat exchange characteristic diagram of the heat exchanger based on the traditional intercooling heat exchanger thermal simulation model are as follows:

[0023] S301, obtaining geometric information of a heat exchanger, wherein the geometric information of the heat exchanger is the perimeter of a cross section of a cold and hot end flow channel;

[0024] S302: establishing a table for storing heat exchanger characteristics, and storing the geometric information of the heat exchanger in the table as the geometric information required for calculating the heat exchanger performance based on the heat exchanger characteristic diagram;

[0025] S303, randomly select different cold and hot end airflow inlet parameter combinations {(Tt h , Pt h ,q h ),(Tt c , Pt c ,q c )}, the different cold and hot end airflow inlet parameter combinations {(Tt h , Pt h ,q h ),(Tt c , Pt c ,q c )} corresponds to different (E h , E c ) combination, where Tt h is the total temperature at the hot end inlet, Pt h is the total pressure at the hot end inlet, q h is the hot end inlet flow rate, Tt cis the total temperature at the cold end inlet, Pt c is the total pressure at the cold end inlet, q c is the cold end inlet flow;

[0026] S304. For different cold and hot end inflow combinations, the unit heat transfer power P and the corrected resistance coefficient F of the heat exchanger under each working condition are calculated based on the traditional intercooling heat exchanger thermal simulation model. h and F c , and calculate the corresponding cold and hot end qualitative temperatures, that is, the average inlet and outlet temperatures;

[0027] S305, use the cold and hot end qualitative temperatures to recalculate the E corresponding to each operating point h and E c 、Re c and Re h , and E h 、E c , P, Re c 、Re h 、F h 、F c Record the data in a table storing the heat exchanger characteristics;

[0028] S306, according to each group of working condition data, a heat exchange characteristic diagram of the heat exchanger is obtained by a two-dimensional scattered point fitting method, wherein the heat exchange characteristic diagram of the heat exchanger is based on E h E c is the independent variable, P is the heat transfer power characteristic data grid with Re as the dependent variable c Re h is the independent variable, F h F c The resistance characteristic data grid is the dependent variable.

[0029] Preferably, the specific content of calculating the heat exchanger performance based on the extracted heat exchange characteristic diagram of the heat exchanger is:

[0030] S401, calculating and obtaining the thermal derivative and Reynolds number of the heat exchanger based on the heat exchanger operating condition thermodynamic parameters and the geometric information in the heat exchanger characteristic number table;

[0031] S402, based on the calculated heat derivative and Reynolds number of the heat exchanger, two-dimensional interpolation is performed according to the heat exchange power characteristic data grid and the resistance characteristic data grid in the heat exchanger characteristic number table to obtain the unit heat exchange power P and the corrected resistance coefficient F of the heat exchanger;

[0032] S403. Substituting the unit heat transfer power P into formulas (1) and (2), the heat transfer performance of the heat exchanger can be calculated.

[0033] S404. Substituting the corrected resistance coefficient F into formulas (3) and (4), the flow loss performance of the heat exchanger can be calculated.

[0034] Preferably, in S302, E h The value changes from 1 to 11, E c The value varies from 1 to 3, and the number of combinations is no less than 200 points.

[0035] Therefore, the heat transfer characteristics extraction method for heat exchanger performance modeling simulation using the above steps of the present invention has the following four advantages compared with the traditional simulation design method:

[0036] 1. The method mentioned in the present invention can further simplify the calculation process of the heat exchanger, speed up the calculation speed, and is more conducive to the large-scale call calculation of the engine performance model;

[0037] 2. The characteristic diagram extracted based on the heat exchanger characteristics and the novel calculation method based on the characteristic diagram interpolation of the present invention have a low calculation error, which can achieve the same simulation accuracy as the heat exchanger thermal simulation model, and have the feasibility consideration of the heat exchanger design. The simulation results can also better simulate the actual heat exchange performance of the heat exchanger under different working conditions;

[0038] 3. The general characteristic diagram obtained by the method of the present invention can be further extended to be applicable to the performance simulation of engine heat exchanger components, without the need to derive and build a complex heat exchanger thermal simulation model;

[0039] 4. The heat exchanger characteristic diagram of the method of the present invention is helpful to guide the design of similar groups of real experiments / simulations, analyze the universal laws of heat exchanger performance, and better apply and design heat exchangers.

[0040] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a heat exchange power characteristic diagram of a heat exchanger component mentioned in a heat exchange characteristic extraction method for heat exchanger performance modeling and simulation of the present invention;

[0042] Figure 2 It is a cold end resistance characteristic diagram of a heat exchanger component mentioned in a heat exchange characteristic extraction method for heat exchanger performance modeling and simulation of the present invention;

[0043] Figure 3 It is a heat exchanger component hot end resistance characteristic diagram mentioned in a heat exchange characteristic extraction method for heat exchanger performance modeling and simulation of the present invention;

[0044] Figure 4 It is a heat transfer power error distribution diagram per unit temperature difference of a characteristic diagram interpolation method mentioned in a heat transfer characteristic extraction method for heat exchanger performance modeling and simulation of the present invention;

[0045] Figure 5 It is a hot end corrected resistance coefficient error distribution diagram of a characteristic diagram interpolation method mentioned in a heat transfer characteristic extraction method for heat exchanger performance modeling and simulation of the present invention;

[0046] Figure 6 It is a cold end corrected resistance coefficient error distribution diagram of a characteristic diagram interpolation method mentioned in a heat transfer characteristic extraction method for heat exchanger performance modeling and simulation of the present invention. DETAILED DESCRIPTION

[0047] The technical solution of the present invention is further described below by means of the accompanying drawings and embodiments. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​described in these embodiments do not limit the scope of the present application.

[0048] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present application, its application, or uses.

[0049] Technologies, systems, and devices known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, systems, and devices should be considered part of the specification.

[0050] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0051] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0052] The present invention provides a method for extracting dimensionless performance parameters that can express the performance of a heat exchanger, and on this basis, constructs a heat exchanger characteristic diagram, which ensures the simulation accuracy of the heat exchanger while accelerating the calculation speed and simplifying the coupling iterative process with the overall performance model of the engine. The focus of this method is: after deriving and establishing a thermal simulation model of an intercooler heat exchanger based on the heat transfer equation and the heat balance equation, the characteristics of the heat exchanger are extracted and applied based on the simulation model. Similar to the rotating parts of the engine, the compressor and turbine, by extracting the characteristics of the components, a large number of experiments / simulation times can be reduced in a similar group manner, and universal laws can be obtained, which can further guide the use and design of the heat exchanger. At the same time, the universal characteristic diagram extracted can be generalized and applied to the component-level performance simulation of the engine heat exchanger.

[0053] The specific steps mentioned in this method are: S1, analyzing and obtaining the similarity criterion of the heat exchanger based on the similarity theory;

[0054] The theoretical basis of this method is the similarity theory, which is a set of theories that study the characteristics of similar physical phenomena and the conditions that ensure the similarity of physical phenomena. The "Three Similarity Theorems" stipulate the properties of similar physical phenomena and the conditions that ensure similarity:

[0055] 1. The first similarity theorem states that for similar phenomena, the similarity criterion number of the same word composition is a constant. According to this theorem, the dimensionless equations of motion of similar physical phenomena are the same, and the similarity criterion numbers in the main terms of these equations are equal.

[0056] 2. The second similarity theorem states that the solution of a differential equation describing a physical phenomenon can always be expressed in the form of a criterion equation, and if there are n physical parameters x1, x2, ..., x n and k basic dimensions, then (nk) independent dimensionless combinations can be formed.

[0057] 3. The third similarity theorem states that if the single-valued conditions of a phenomenon are similar and the values ​​of the similarity criteria derived from the single-valued conditions are equal, then the phenomenon is similar. Single-valued conditions refer to boundary conditions and initial conditions. Similar single-valued conditions mean similarity in geometry and physical properties, and the velocity, pressure and temperature fields in the incoming flow and the entire flow field at the initial moment are similar.

[0058] To summarize, the purpose of the first similarity theorem is to determine the similarity conditions, unify the equation analysis method and the dimensional analysis method to first solve the similarity criterion number and then find the similarity conditions; the second similarity theorem solves the method of solving the similarity criterion number of physical phenomena that have not been described by a definite physical equation; the third similarity theorem generalizes the similarity criterion equation obtained from the experiment to all phenomena similar to the model phenomenon.

[0059] From gas dynamics, we know that if geometrically similar objects are flowing around in an airflow, and the velocity ratio, pressure ratio, temperature ratio, etc. at any similar points on each object are the same at every moment, then this stable flow of gas is a similar flow.

[0060] In general, the criteria for ensuring flow similarity are very broad, and they are: the Mach number that represents the compressibility characteristics of the gas; the Reynolds number that represents the viscosity characteristics of the gas; the Becker number that represents the heat exchange; the Froude number that represents the effect of gravity on the gas; the Strouhal number that represents the unstable flow characteristics of the gas; the adiabatic index that characterizes the gas constant; and the Nusselt number that reflects the heat transfer characteristics. Obviously, it is not feasible and necessary to meet all these criteria at the same time. A more practical method is to select the most important factors based on the actual phenomenon being studied.

[0061] From gas dynamics, we know that for heat exchangers, the similarity conditions can be summarized into three: geometric similarity, flow field similarity and dynamic similarity. Geometric similarity requires that the geometric dimensions of the two heat exchangers must be proportional. Flow field similarity requires that the velocity directions of corresponding points in the heat exchanger are the same and proportional in size. The hot and cold end fluids in the heat exchanger are both axial flows. For heat exchangers of the same or equal proportions, the first two similarity conditions are easy to meet. Dynamic similarity requires that the directions of similar forces at corresponding points in the heat exchanger are the same and proportional in size. The similarity criteria include Euler number, Mach number, Reynolds number, Nusselt number, etc. All of the above similarity criteria are difficult to meet at the same time, and the most important similarity criteria need to be selected based on the flow problem being studied.

[0062] For example, the physical meaning of the Mach number is the ratio of inertial force to static pressure, which characterizes the influence of static pressure on the compressibility of the fluid. For the heat exchanger, this does not affect its key performance, so the Mach number is not selected as the similarity criterion; the physical meaning of the Reynolds number Re is the ratio of inertial force to viscous force, which characterizes the influence of viscous force on the flow resistance of the fluid, thereby affecting the flow loss of the heat exchanger, so it is selected as one of the similarity criteria; the Nusselt number Nu characterizes the physical properties of the fluid's convective heat transfer capacity and determines the heat transfer performance of the heat exchanger, so it is also selected as one of the similarity criteria.

[0063] According to the third similarity theorem, the similarity of phenomena requires similar single-valued conditions. For heat exchangers, what needs to be paid attention to is the similarity of the physical properties of the airflow. From the formula of the convective heat transfer coefficient, it can be seen that if the convective heat transfer coefficient is to be equal, in addition to ensuring that Nu is equal, it is also necessary to ensure that the thermal conductivity of the gas is equal. Therefore, the thermal derivative E=λ*Nu is defined as the similarity criterion. When the thermal derivatives of two heat exchangers are equal, the heat transfer performance of the heat exchanger is equal.

[0064]

[0065] After the above analysis of the similarity criteria of the heat exchanger, the similarity criteria of the two heat exchangers were finally determined. Considering that the heat exchanger has hot and cold end fluids participating in the heat exchange, the similarity criteria can be expressed as follows:

[0066] 1. When the Reynolds numbers Re of the airflow at the cold and hot ends of the heat exchanger are equal, the flow loss performance of the heat exchanger is equal

[0067] 2. When the thermal derivative E of the cold and hot ends of the heat exchanger is equal, the heat transfer performance of the heat exchanger is equal

[0068] S2. Based on the heat exchanger similarity criterion, combined with the heat transfer equation and Fanning equation, the unit temperature difference heat transfer power P w and the heat exchanger corrected resistance coefficient F as characteristic parameters characterizing the performance of the heat exchanger;

[0069] After determining the similarity criterion of the heat exchanger, it is also necessary to determine the heat exchanger characteristic form that can meet the calculation requirements of the overall engine performance model. Taking the similarity criterion number as the independent variable, it is necessary to determine the characteristic parameters that characterize the performance of the heat exchanger as the dependent variable.

[0070] In S2, based on the heat exchanger similarity criterion, the heat transfer formula and Fanning formula are combined to analyze the unit temperature difference heat transfer power P w The specific process of using the heat exchanger corrected resistance coefficient F as a characteristic parameter to characterize the performance of the heat exchanger is:

[0071] For the heat transfer performance of the heat exchanger, the heat transfer equation (1) can be used to derive equation (2): K(E c ,E h )AΔT m =qc p |T2-T1|=Q (1);

[0072]

[0073] Among them, P w is the heat transfer power per unit temperature difference of the heat exchanger, K is the total heat transfer coefficient of the heat exchanger calculated using the thermal derivative as the independent variable, E c is the cold end thermal derivative, E h is the thermal derivative of the hot end, A is the heat exchange area, ΔT m is the logarithmic mean temperature difference, q is the fluid flow rate, c p is the specific heat capacity at constant pressure, T2 is the temperature after heat exchange, T1 is the temperature before heat exchange, and Q is the heat exchange amount.

[0074] For two heat exchangers with the same geometric dimensions, their heat transfer areas A are equal. According to the first heat exchanger similarity criterion, when the thermal derivatives E of the cold and hot ends of the two heat exchangers are equal, c , E h When the corresponding values ​​are equal, the total heat transfer coefficients K of the two heat exchangers are equal. At this time, it can be seen from formula (2) that the unit temperature difference heat transfer power P of the two heat exchangers is w That is, when the thermal derivatives of two heat exchangers of the same size are equal, the heat transfer power per unit temperature difference P w are equal, so P w As a characteristic parameter to characterize the heat transfer performance of the heat exchanger.

[0075]

[0076] For the flow resistance loss performance of the heat exchanger, equation (4) can be derived from Fanning equation (3):

[0077]

[0078] Where Δp is the pressure loss, S is the length of the heat exchanger pipe, and de is the diameter of the heat exchanger pipe, u is the fluid flow rate, A is the cross-sectional area of ​​the heat exchanger pipe, f is the heat exchanger resistance coefficient calculated by the single-valued function of the Reynolds number Re, q is the fluid flow rate, ρ is the fluid density, and F is the corrected resistance coefficient of the heat exchanger.

[0079] For two heat exchangers with the same geometric dimensions, the heat exchanger pipe length S, cross-sectional area A, and diameter d e Equal. According to the second heat exchanger similarity criterion, when the Reynolds numbers Re c 、Re h When the corresponding values ​​are equal, the heat exchanger resistance coefficients f of the two heat exchangers are equal. At this time, it can be seen from formula (4) that the heat exchanger corrected resistance coefficients F of the two heat exchangers are equal. That is, when the Reynolds numbers of two heat exchangers of the same size are equal, the heat exchanger corrected resistance coefficients F are equal, so F can be used as a characteristic parameter to characterize the flow loss performance of the heat exchanger.

[0080] like Figure 1-Figure 3 As shown, Figure 1-Figure 3 The heat exchanger characteristic diagram is generated based on the heat exchanger performance simulation model, with the above selected similarity criteria as the independent variable and the heat exchanger performance characteristic parameters as the dependent variable. Figure 1 It is the heat transfer power characteristic diagram of the heat exchanger components. Figure 2 is the cold end resistance characteristic diagram of the heat exchanger component, Figure 3 This is the hot end resistance characteristic diagram of the heat exchanger components.

[0081] Next, the steps for generating the heat exchanger characteristics and the calculation logic of the heat exchanger module after adopting the heat exchanger characteristic diagram are introduced.

[0082] S3, obtaining the geometric information of the heat exchanger and the airflow inlet parameters of different cold and hot ends, given the different airflow inlet parameters of the cold and hot ends to form different incoming flow parameter combinations, extracting the characteristics of the heat exchanger based on the traditional intercooling heat exchanger thermal simulation model and generating a heat transfer characteristic diagram of the heat exchanger;

[0083] For the geometric information of the heat exchanger, it is necessary to record and store the total circulation area of ​​the hot and cold ends, the characteristic length and aspect ratio of a single circulation channel. To obtain the geometric information of the heat exchanger and the different cold and hot end airflow inlet parameters, different cold and hot end airflow inlet parameters are given to form different incoming flow parameter combinations. Based on the traditional intercooling heat exchanger thermal simulation model, the heat exchanger characteristics are extracted and the heat exchange characteristic diagram of the heat exchanger is generated. The steps are as follows:

[0084] SS301, obtaining geometric information of the heat exchanger and airflow inlet parameters of different cold and hot ends, wherein the geometric information of the heat exchanger is the perimeter of the cross section of the cold and hot end flow channel;

[0085] S302: establishing a table for storing heat exchanger characteristics, and storing the geometric information of the heat exchanger in the table as the geometric information required for calculating the heat exchanger performance based on the heat exchanger characteristic diagram;

[0086] S303, randomly select different cold and hot end airflow inlet parameter combinations {(Tt h , Pt h ,q h ),(Tt c , Pt c ,q c )}, the different cold and hot end airflow inlet parameter combinations {(Tt h , Pt h ,q h ),(Tt c , Pt c ,q c )} corresponds to different (E h , E c ) combination, where Tt h is the total temperature at the hot end inlet, Pt h is the total pressure at the hot end inlet, q h is the hot end inlet flow rate, Tt c is the total temperature at the cold end inlet, Pt c is the total pressure at the cold end inlet, q c is the cold end inlet flow;

[0087] S304. For different cold and hot end inflow combinations, the unit heat transfer power P and the corrected resistance coefficient F of the heat exchanger under each working condition are calculated based on the traditional intercooling heat exchanger thermal simulation model. h and F c , and calculate the corresponding cold and hot end qualitative temperatures, that is, the average inlet and outlet temperatures;

[0088] S305, use the cold and hot end qualitative temperatures to recalculate the E corresponding to each operating point h and E c 、Re c and Re h , and E h 、E c , P, Re c 、Re h 、F h 、F c Record the data in a table storing the heat exchanger characteristics;

[0089] S306, according to each group of working condition data, a heat exchange characteristic diagram of the heat exchanger is obtained by a two-dimensional scattered point fitting method, wherein the heat exchange characteristic diagram of the heat exchanger is based on E h E c is the independent variable, P is the heat transfer power characteristic data grid with Re as the dependent variable cRe h is the independent variable, F h F c The resistance characteristic data grid is the dependent variable.

[0090] The table storing the heat exchanger geometric information, the heat transfer power characteristic data grid and the resistance characteristic data grid is the heat exchanger characteristic table.

[0091] S4. Calculate the heat exchanger performance based on the extracted heat exchanger heat transfer characteristic diagram, where the heat exchanger performance includes heat transfer performance and flow resistance loss performance.

[0092] The specific contents of calculating the heat exchanger performance based on the extracted heat exchange characteristic diagram of the heat exchanger are as follows;

[0093] S401, calculating and obtaining the thermal derivative and Reynolds number of the heat exchanger based on the heat exchanger operating condition thermodynamic parameters and the geometric information in the heat exchanger characteristic number table;

[0094] S402, based on the calculated heat derivative and Reynolds number of the heat exchanger, two-dimensional interpolation is performed according to the heat exchange power characteristic data grid and the resistance characteristic data grid in the heat exchanger characteristic number table to obtain the unit heat exchange power P and the corrected resistance coefficient F of the heat exchanger;

[0095] S403. Substituting the unit heat transfer power P into formulas (1) and (2), the heat transfer performance of the heat exchanger can be calculated.

[0096] S404. Substituting the corrected resistance coefficient F into formulas (3) and (4), the flow loss performance of the heat exchanger can be calculated.

[0097] For the unit heat transfer power P obtained by interpolation, according to the following formula,

[0098] Q1=qc p,h (T h,in -T h,out );

[0099] Q2=P w ΔT m ;

[0100] When the unit heat transfer power is known, only the hot end outlet temperature needs to be guessed, and the actual cold and hot end outlet temperatures can be quickly iterated based on the Q residuals calculated separately. For the corrected resistance coefficient F obtained by interpolation, the flow resistance loss of the heat exchanger can be calculated according to the following formula, which greatly simplifies the complicated calculation steps in the previous heat exchanger thermal simulation model.

[0101]

[0102] However, it should be noted that, compared with the use of the heat exchanger thermal simulation model, there is a certain error in the heat exchanger performance calculated directly using the generated heat exchanger characteristic diagram. The reason is that in the calculation of the heat exchanger simulation model, due to the large temperature variation between the cold and hot ends, the average inlet and outlet temperature (qualitative temperature) is used for calculation. In the interpolation calculation of the characteristic diagram, since only the inlet temperature is known, the thermal derivative E and Reynolds number Re used in the interpolation calculation are calculated by the inlet temperature. This problem can be solved by the method of prediction and correction, that is, based on the inlet and outlet temperatures obtained by the initial calculation, the qualitative temperature is calculated, and then the new unit heat transfer power and corrected resistance coefficient are obtained by interpolation based on the thermal derivative and Reynolds number calculated and divided by the qualitative temperature. At this time, the calculated heat exchanger performance has a higher accuracy.

[0103] Advantages and beneficial effects of this patent solution:

[0104] To illustrate the advantages of the method proposed in this patent, the accuracy of the above technical solution of the present invention is verified through specific examples. By giving 100 sets of airflow parameter combinations at the cold and hot ends of the heat exchanger, and comparing the errors between the calculation results based on the heat exchanger characteristic diagram interpolation method and the calculation results compared with the heat exchanger thermal simulation model, the accuracy of the technical solution of the present invention can be verified. Table 1 shows the error comparison between the characteristic diagram interpolation method and the heat exchanger thermal simulation model. Figure 4-Figure 6 As shown, Figure 4-Figure 6 The error distribution of 100 sets of calculation results of the characteristic diagram interpolation method is given, where Figure 4 is the unit temperature difference heat transfer power error distribution of the characteristic diagram interpolation method, Figure 5 is the error distribution of the hot end corrected drag coefficient using the characteristic map interpolation method, Figure 6 The error distribution of cold end corrected drag coefficient using the characteristic diagram interpolation method.

[0105] Table 1

[0106] Heat exchange power Pw Hot end resistance correction factor Cold end resistance correction factor Average Error 0.0096％ 0.046％ 0.051％ Maximum error 0.13％ 0.43％ 0.36％

[0107] From Table 1 and Figure 4-Figure 6It can be seen that the characteristic diagram extracted based on the heat exchanger characteristics and the new calculation method based on characteristic diagram interpolation have low calculation errors, which can achieve the same simulation accuracy as the heat exchanger thermal simulation model, and have the feasibility considerations of heat exchanger design. The simulation results can also better simulate the actual heat transfer performance of the heat exchanger under different working conditions. At the same time, the use of this method can further simplify the calculation process of the heat exchanger, speed up the calculation speed, and be more conducive to the large-scale call calculation of the engine performance model. In addition, similar to the characteristic diagram of the rotating parts of the engine, the extracted heat exchanger characteristic diagram is more conducive to guiding the design of similar groups of real experiments / simulations, analyzing the universal laws of heat exchanger performance, and better applying and designing heat exchangers. At the same time, the universal characteristic diagram extracted can also be further promoted to be applicable to the performance simulation of engine heat exchanger components, without the need to derive and build a complex heat exchanger thermal simulation model.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A heat transfer characteristic extraction method for heat exchanger performance modeling and simulation, characterized in that: Here are the steps: S1. Analyze and obtain the similarity criterion of heat exchanger based on similarity theory; S2. Based on the heat exchanger similarity criterion, combined with the heat transfer equation and Fanning equation analysis, the unit temperature difference heat transfer power and the corrected resistance coefficient of the heat exchanger As a characteristic parameter to characterize the performance of the heat exchanger; S3, obtaining geometric information of the heat exchanger, given different cold and hot end airflow inlet parameters to form different incoming flow parameter combinations, extracting characteristics of the heat exchanger based on the traditional intercooling heat exchanger thermal simulation model and generating a heat exchange characteristic diagram of the heat exchanger; S4. Calculating the heat exchanger performance based on the extracted heat exchange characteristic diagram of the heat exchanger, where the heat exchanger performance includes heat exchange performance and flow resistance loss performance; The heat exchanger similarity criterion in S1 includes a first heat exchanger similarity criterion and a second heat exchanger similarity criterion; The first heat exchanger similarity criterion is that when the Reynolds number of the hot and cold ends of two heat exchangers of the same size is When the corresponding values ​​are equal, the flow loss performance of the two heat exchangers is equal, and the Reynolds number Re is the similarity criterion number of the heat exchanger; The second heat exchanger similarity criterion is that when the thermal derivatives of the hot and cold ends of two heat exchangers of the same size are , When the corresponding values ​​are equal, the heat transfer performance of the two heat exchangers is equal, and the thermal derivative is the similarity criterion number of the heat exchanger; In S2, based on the heat exchanger similarity criterion, the heat transfer formula and Fanning formula are combined to analyze the unit temperature difference heat transfer power. and the corrected resistance coefficient of the heat exchanger The specific process of characterizing the performance characteristic parameters of the heat exchanger is: For the heat transfer performance of the heat exchanger, equation (2) is derived from the heat transfer equation (1): （1）； （2）； in, is the heat transfer power per unit temperature difference of the heat exchanger, K is the total heat transfer coefficient of the heat exchanger calculated using the thermal derivative as the independent variable, is the cold end thermal derivative, is the hot end thermal derivative, A is the heat exchange area, is the logarithmic mean temperature difference, q is the fluid flow rate, is the specific heat capacity at constant pressure, is the temperature after heat exchange, is the temperature before heat exchange, Q is the heat exchange amount; For the flow resistance loss performance of the heat exchanger, equation (4) is derived from Fanning equation (3): （3）； （4）； in, is the pressure loss, S is the length of the heat exchanger pipe, is the diameter of the heat exchanger pipe, u is the fluid flow rate, A is the cross-sectional area of ​​the heat exchanger pipe, f is the heat exchanger resistance coefficient calculated by the single-valued function of the Reynolds number Re, q is the fluid flow rate, is the fluid density, F is the corrected resistance coefficient of the heat exchanger; In S3, the geometric information of the heat exchanger is obtained. Given different cold and hot end airflow inlet parameters to form different incoming flow parameter combinations, the heat exchanger characteristics are extracted based on the traditional intercooling heat exchanger thermal simulation model and the specific contents of the heat exchanger heat transfer characteristic diagram are generated as follows: S301, obtaining geometric information of a heat exchanger, wherein the geometric information of the heat exchanger is the perimeter of a cross section of a cold and hot end flow channel; S302: establishing a table for storing heat exchanger characteristics, and storing the geometric information of the heat exchanger in the table as the geometric information required for calculating the heat exchanger performance based on the heat exchanger characteristic diagram; S303, randomly select different cold and hot end airflow inlet parameter combinations , the different cold and hot end air flow inlet parameter combinations Corresponding to different Combination, where is the total temperature at the hot end inlet, is the total pressure at the hot end inlet, is the hot end inlet flow rate, is the total temperature at the cold end inlet, is the total pressure at the cold end inlet, is the cold end inlet flow; S304. For different cold and hot end inflow combinations, the unit heat transfer power P and the corrected resistance coefficient of the heat exchanger under various working conditions are calculated based on the traditional intercooling heat exchanger thermal simulation model. and , and calculate the corresponding cold and hot end qualitative temperatures, that is, the average inlet and outlet temperatures; S305, use the cold and hot end qualitative temperature to recalculate the corresponding temperature of each working point and and , and Record the data in a table storing the heat exchanger characteristics; S306, according to each group of working condition data, a heat exchange characteristic diagram of the heat exchanger is obtained by a two-dimensional scattered point fitting method, wherein the heat exchange characteristic diagram of the heat exchanger is is the independent variable, The heat transfer power characteristic data grid with the dependent variable is the independent variable, The resistance characteristic data grid for the dependent variable.

2. A heat transfer characteristic extraction method for heat exchanger performance modeling and simulation according to claim 1, characterized in that: The specific contents of calculating the heat exchanger performance based on the extracted heat exchange characteristic diagram of the heat exchanger are as follows; S401, calculating and obtaining the thermal derivative and Reynolds number of the heat exchanger based on the heat exchanger operating condition thermodynamic parameters and the geometric information in the heat exchanger characteristic number table; S402, based on the calculated heat derivative and Reynolds number of the heat exchanger, perform two-dimensional interpolation according to the heat exchange power characteristic data grid and the resistance characteristic data grid in the heat exchanger characteristic number table to obtain the unit heat exchange power P and the corrected resistance coefficient F of the heat exchanger; S403, substituting the unit heat exchange power P into formulas (1) and (2) to calculate the heat exchange performance of the heat exchanger; S404, substituting the corrected resistance coefficient F into formulas (3) and (4) to calculate the flow loss performance of the heat exchanger.

3. The heat transfer characteristics extraction method for heat exchanger performance modeling and simulation according to claim 1 is characterized in that: S303 The value varies from 1 to 11. The value varies from 1 to 3, and the number of combinations is no less than 200 points.

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