Method for determining thermal dynamic characteristics and calculating heat exchange capacity of air-air heat exchanger

Abstract

The application belongs to the technical field of performance evaluation of aero-engine thermal management system, and particularly relates to a method for determining thermal dynamic characteristics of an air-air heat exchanger and calculating heat exchange amount, wherein the method for determining thermal dynamic characteristics of the air-air heat exchanger comprises the following steps: step one, performing component-level heat exchange characteristic test on the air-air heat exchanger to obtain heat exchange amount of the air-air heat exchanger under different temperatures, pressures and flow rates of cold and hot sides; step two, calculating the hot side Reynolds number Re1, the cold side Reynolds number Re2 and the heat exchange amount QTA per unit temperature difference per unit area of the air-air heat exchanger under different temperatures, pressures and flow rates of cold and hot sides; and step three, taking logarithm of the hot side Reynolds number Re1, the cold side Reynolds number Re2 and the heat exchange amount QTA per unit temperature difference per unit area of the air-air heat exchanger under different temperatures, pressures and flow rates of cold and hot sides, and then performing polynomial fitting to obtain the thermal dynamic characteristics of the air-air heat exchanger.

Description

Technical Field

[0001] This application belongs to the technical field of performance evaluation of aero-engine thermal management systems, specifically relating to a method for determining the thermodynamic characteristics of an air-to-air heat exchanger and calculating its heat exchange capacity. Background Technology

[0002] With the continuous development of aero-engine technology, the heat dissipation requirements of aero-engine lubrication systems and high-power components are increasing, necessitating the use of air-to-air heat exchangers to cool high-temperature, high-pressure air from the aero-engine's low-temperature bypass air. To evaluate the performance of the aero-engine thermal management system, it is necessary to obtain the heat transfer characteristics of the air-to-air heat exchanger, and thus acquire the heat transfer capacity of the air-to-air heat exchanger under various conditions.

[0003] Currently, the heat transfer characteristics of fuel-oil heat exchangers are obtained by conducting a series of tests at different fuel flow rates and plotting the thermodynamic curves of the fuel-oil heat exchanger. The thermodynamic curves of the fuel-oil heat exchanger are shown below. Figure 1 As shown, the horizontal axis represents the fuel flow rate, and the vertical axis represents the heat exchanger's heat transfer per unit temperature difference. One-dimensional interpolation can be performed based on the fuel flow rate under different operating conditions to obtain the heat transfer of the fuel-oil heat exchanger. This method is feasible on the premise that the lubricating oil flow rate of the fuel-oil heat exchanger does not change with the operating conditions, and that changes in the temperature and pressure of fuel and lubricating oil have no effect on their physical properties and do not affect the heat transfer calculation. The main change in operating conditions is reflected in the change in fuel flow rate.

[0004] The method for determining the heat transfer characteristics and heat transfer capacity of a fuel-lubricating oil heat exchanger is a common approach used in aero-engines. The experimental design for its thermodynamic curves is relatively simple, considering only the influence of a single variable.

[0005] Compared to conventional heat exchangers such as fuel-oil heat exchangers in aero engines, air-to-air heat exchangers operate under more complex conditions, primarily because they utilize a gaseous medium, which differs significantly from the liquid medium used in conventional heat exchangers. The air pressure on the cold and hot sides of an air-to-air heat exchanger can vary from tens of kilopascals to thousands of kilopascals, the temperature from tens of degrees below zero to hundreds of degrees above zero, and the flow rate from tens of grams per second to several kilograms per second, resulting in drastic changes in physical properties. While the density of the liquid medium in a fuel-oil heat exchanger varies by less than 10% under different aero engine operating conditions, the density of air in an air-to-air heat exchanger can vary by tens of times.

[0006] Considering only the influence of a single variable on the heat exchange characteristics of a fuel-lubricating oil heat exchanger and the method for obtaining its heat exchange capacity is difficult to apply to air-to-air heat exchangers. The heat exchange characteristics of an air-to-air heat exchanger and the method for obtaining its heat exchange capacity need to consider the influence of six dimensions of parameter changes on the heat exchange capacity, namely temperature, pressure, and flow rate on both the cold and hot sides.

[0007] In view of the above, this application is hereby filed. Summary of the Invention

[0008] The purpose of this application is to provide a method for determining the thermodynamic characteristics and calculating the heat transfer of an air-to-air heat exchanger, so as to accurately determine the thermodynamic characteristics of the air-to-air heat exchanger and calculate the heat transfer of the air-to-air heat exchanger under a series of conditions, thus providing a reliable basis for the performance evaluation of the thermal management system of aero-engines.

[0009] The technical solution of this application is:

[0010] One aspect provides a method for determining the thermodynamic characteristics of an air-to-air heat exchanger, including:

[0011] Step 1: Conduct component-level heat transfer characteristic tests on the air-to-air heat exchanger to obtain the heat transfer capacity of the air-to-air heat exchanger under different temperatures, pressures, and flow rates on the cold and hot sides;

[0012] Step 2: Calculate the Reynolds number Re1 on the hot side, Re2 on the cold side, and the heat transfer per unit area per unit temperature difference for the air-to-air heat exchanger under different temperatures, pressures, and flow rates on the cold and hot sides.

[0013] Step 3: For the air-to-air heat exchanger at different temperatures, pressures, and flow rates on the hot and cold sides, take the logarithm of the hot-side Reynolds number Re1, the cold-side Reynolds number Re2, and the heat transfer per unit area per unit temperature difference QTA, and then perform polynomial fitting to obtain the thermodynamic characteristics of the air-to-air heat exchanger.

[0014] X = log(Re1);

[0015] Y = log(Re2);

[0016] Z = log(QTA);

[0017] in,

[0018] X, Y, and Z are the logarithms of the hot-side Reynolds number Re1, the cold-side Reynolds number Re2, and the heat transfer per unit area per unit temperature difference, QTA.

[0019] The fitted polynomial is in the form of:

[0020] ;

[0021] in,

[0022] p00, p10, p01, p20, p11, and p02 are the fitting coefficients that are yet to be determined.

[0023] According to at least one embodiment of this application, in the above-described method for determining the thermodynamic characteristics of an air-to-air heat exchanger, in step one, mass flow measurement points are arranged at the inlet of the cold and hot sides of the air-to-air heat exchanger, and temperature and pressure measurement points are arranged at the inlet and outlet.

[0024] Based on the six parameters of the air-to-air heat exchanger—hot side inlet temperature, hot side inlet pressure, hot side flow rate, cold side inlet temperature, cold side inlet pressure, and cold side flow rate—and their potential ranges in actual use, a six-factor DOE test scheme is designed.

[0025] The calculation of heat exchange capacity for air-to-air heat exchangers is as follows:

[0026] Q = qm1 × △T1;

[0027] in,

[0028] Q represents the heat exchange rate;

[0029] qm1 is the hot-side flow rate;

[0030] △T1 is the temperature difference between the inlet and outlet on the hot side.

[0031] According to at least one embodiment of this application, in the above-described method for determining the thermodynamic characteristics of an air-to-air heat exchanger, step two includes:

[0032] ;

[0033] ;

[0034] ;

[0035] in,

[0036] de1 is the equivalent diameter of the flow channel within the hot-side core;

[0037] Ac1 is the heat flow area on the hot side;

[0038] μ1 is the thermal dynamic viscosity;

[0039] qm2 is the cold side flow rate;

[0040] de2 is the equivalent diameter of the flow channel inside the cold-side core;

[0041] Ac2 is the cold-side flow area;

[0042] μ2 is the cold-side dynamic viscosity;

[0043] T1in is the inlet temperature on the hot side;

[0044] T2in is the cold-side inlet temperature;

[0045] A1 represents the heat exchange area on the hot side.

[0046] On the other hand, a method for calculating the heat exchange capacity of an air-to-air heat exchanger is provided, including:

[0047] The first step is to calculate the hot-side Reynolds number Re1 and the cold-side Reynolds number Re2 of the air-to-air heat exchanger. The calculation requires relevant parameters, which can be set or measured.

[0048] The second step is to calculate the logarithms X and Y of the hot-side Reynolds number Re1 and the cold-side Reynolds number Re2 of the air-to-air heat exchanger.

[0049] The three steps are as follows: Based on X and Y, the thermodynamic characteristics of the air-to-air heat exchanger are obtained by polynomial fitting using the method for determining the thermodynamic characteristics of the air-to-air heat exchanger described in claim 1, and the logarithm Z of the heat transfer per unit area per unit temperature difference of the air-to-air heat exchanger is calculated.

[0050] Four steps: Calculate the heat exchange capacity Q of the air-to-air heat exchanger based on Z.

[0051] According to at least one embodiment of this application, the four steps in the above-described method for calculating the heat exchange capacity of an air-to-air heat exchanger are as follows:

[0052] .

[0053] This application has at least the following beneficial technical effects:

[0054] This paper provides a method for determining the thermodynamic characteristics and calculating the heat transfer of an air-to-air heat exchanger. It clarifies the test state points for heat transfer characteristic experiments, guides the conduct of heat exchanger characteristic tests, and obtains a series of test data. The paper then renders the cold and hot side performance data of the heat exchanger under different operating conditions dimensionless, performs two-dimensional surface fitting, and obtains the relationship between the heat transfer and the dimensionless flow rates of the cold and hot sides. This method accurately determines the thermodynamic characteristics of the air-to-air heat exchanger and, through the obtained relationship, accurately calculates the heat transfer of the air-to-air heat exchanger under new operating conditions, providing a reliable basis for the performance evaluation of aero-engine thermal management systems. Attached Figure Description

[0055] Figure 1 This is a thermodynamic curve of a current oil-fired heat exchanger;

[0056] Figure 2 - is a schematic diagram of an air-to-air heat exchanger for an aircraft engine provided in an embodiment of this application;

[0057] Figure 3 This is a schematic diagram of another air-to-air heat exchanger for an aero-engine provided in the embodiments of this application;

[0058] Figure 4This is a graph showing the correspondence between the resolution of the six-factor DOE experimental scheme and the experimental scheme provided in the embodiments of this application;

[0059] Figure 5 This is a diagram illustrating the creation of a six-factor DOE experimental design provided in the embodiments of this application;

[0060] Figure 6 This is a surface diagram of the thermodynamic characteristics of an air-to-air heat exchanger obtained by polynomial fitting according to an embodiment of this application.

[0061] Figure 7 This is a comparison chart of the test results of the air-to-air heat exchanger operating point and the heat exchange results calculated from the thermodynamic characteristics, provided in the embodiments of this application.

[0062] To better illustrate this embodiment, some content in the accompanying drawings may be omitted, enlarged, or reduced. They are for illustrative purposes only and should not be construed as limiting the scope of this application. Detailed Implementation

[0063] To make the technical solution and advantages of this application clearer, the technical solution of this application will be described in a clearer and more complete manner below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only some embodiments of this application, and are only used to explain this application, not to limit this application. It should be noted that, for ease of description, only the parts related to this application are shown in the accompanying drawings, and other related parts can be referred to the general design.

[0064] Furthermore, unless otherwise defined, the technical or scientific terms used in this application description shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The word "comprising" as used in this application description indicates that the concept preceding the word encompasses the concepts listed following the word and their equivalents, without excluding other related concepts.

[0065] Figure 2 , Figure 3 This is a schematic diagram of an air-to-air heat exchanger used in an aero-engine. The two media are high-temperature, high-pressure air and low-temperature bypass air, respectively. The two media exchange heat through the air-to-air heat exchanger. After the high-temperature air exchanges heat, its temperature decreases. The heat exchange capacity of the air-to-air heat exchanger can be calculated by monitoring the inlet and outlet temperatures, pressures, and flow rates of the medium on the hot side of the heat exchanger. Based on this, this application provides a method for determining the thermodynamic characteristics of an air-to-air heat exchanger.

[0066] Step 1: Conduct component-level heat transfer characteristic tests on the air-to-air heat exchanger to obtain the heat transfer capacity of the air-to-air heat exchanger under different temperatures, pressures, and flow rates on the cold and hot sides.

[0067] The air-to-air heat exchanger heat exchange characteristic test bench is required to provide air of different temperatures, pressures, and flow rates to the cold and hot sides of the air-to-air heat exchanger in order to simulate different operating conditions of the heat exchanger.

[0068] Mass flow measurement points are arranged at the inlet of the cold and hot sides of the air-to-air heat exchanger, and temperature and pressure measurement points are arranged at the inlet and outlet.

[0069] Determine the maximum and minimum values ​​of six parameters of the air-to-air heat exchanger: hot-side inlet temperature, hot-side inlet pressure, hot-side flow rate, cold-side inlet temperature, cold-side inlet pressure, and cold-side flow rate, and design typical test state points.

[0070] For example, an aero-engine has N typical states. Statistics on these N typical states of an aero-engine include:

[0071] The minimum and maximum values ​​of the hot-side inlet temperature of the air-to-air heat exchanger are T1min and T1max.

[0072] The minimum and maximum values ​​of the hot-side inlet pressure of the air-to-air heat exchanger are P1min and P1max, respectively.

[0073] The minimum and maximum flow rates on the hot side of the air-to-air heat exchanger are qm1min and qm1max, respectively.

[0074] The minimum and maximum values ​​of the cold side inlet temperature of the air-to-air heat exchanger are T2min and T2max;

[0075] The minimum and maximum values ​​of the cold-side inlet pressure of the air-to-air heat exchanger are P2min and P2max, respectively.

[0076] The minimum and maximum flow rates of the cold side of the air-to-air heat exchanger are qm2min and qm2max, respectively.

[0077] Based on the six parameters of the air-to-air heat exchanger—hot side inlet temperature, hot side inlet pressure, hot side flow rate, cold side inlet temperature, cold side inlet pressure, and cold side flow rate—and their potential ranges in actual use, a six-factor DOE test scheme is designed. Depending on the resolution of the factor design, a 1 / 8, 1 / 4, 1 / 2, or full factorial design scheme can be selected.

[0078] The correspondence between the resolution and the experimental sub-schemes of a six-factor DOE experimental design is shown in [reference needed]. Figure 4 Select the experimental design based on the experimental budget. If the budget is sufficient, a full factorial design with the most experimental state points can be selected. The resolution of the experiment should not be lower than level III, and the number of center points in each region should not be less than 1.

[0079] Based on the minimum and maximum values ​​of six parameters of the air-to-air heat exchanger—hot-side inlet temperature, hot-side inlet pressure, hot-side flow rate, cold-side inlet temperature, cold-side inlet pressure, and cold-side flow rate—a six-factor design of experiment (DOE) is created. (See [reference]). Figure 5 Based on the minimum and maximum values ​​of the six parameters of the air-to-air heat exchanger—hot side inlet temperature, hot side inlet pressure, hot side flow rate, cold side inlet temperature, cold side inlet pressure, and cold side flow rate—a test sequence table is generated, as shown in the table below.

[0080] Test record sheet for heat transfer characteristics of air-to-air heat exchangers with resolution level IV:

[0081] 1 800 2000 0.02 300 50 0.2 Record the test results 2 800 200 0.2 200 50 1 … 3 400 200 0.2 200 200 1 … 4 800 200 0.02 200 200 0.2 … 5 800 2000 0.2 300 200 1 … 6 800 200 0.2 300 50 0.2 … 7 400 2000 0.2 200 50 0.2 … 8 400 2000 0.02 300 200 0.2 … 9 800 200 0.02 300 200 1 … 10 400 200 0.02 200 50 0.2 … 11 800 2000 0.2 200 200 0.2 … 12 400 2000 0.2 300 50 1 … 13 400 200 0.02 300 50 1 … 14 400 200 0.2 300 200 0.2 … 15 600 1100 0.11 250 125 0.6 … 16 800 2000 0.02 200 50 1 … 17 400 2000 0.02 200 200 1 …

[0082] According to the test record sheet for the heat transfer characteristics of the air-to-air heat exchanger, the test was carried out, and the heat transfer at each test state point was recorded. The calculation of the heat transfer of the air-to-air heat exchanger is as follows:

[0083] Q = qm1 × △T1;

[0084] in,

[0085] Q represents the heat exchange capacity, measured in kW.

[0086] qm1 is the heat-side flow rate, in kg / s;

[0087] △T1 is the temperature difference between the inlet and outlet of the hot side, in K.

[0088] Step 2: Calculate the Reynolds number Re1 on the hot side, Re2 on the cold side, and the heat transfer per unit area per unit temperature difference for the air-to-air heat exchanger under different temperatures, pressures, and flow rates on the cold and hot sides. Perform dimensionless processing on the experimental data.

[0089] ;

[0090] ;

[0091] ;

[0092] in,

[0093] de1 is the equivalent diameter of the flow channel in the hot-side core, in meters.

[0094] Ac1 is the heat flow area, in m2;

[0095] μ1 is the dynamic viscosity on the thermal side, in Pa·s;

[0096] qm2 is the cold side flow rate, in kg / s;

[0097] de2 is the equivalent diameter of the flow channel in the cold side core, in meters.

[0098] Ac2 is the cold-side flow area, in m2;

[0099] μ2 is the cold-side dynamic viscosity, in Pa·s;

[0100] T1in is the inlet temperature on the hot side, in K.

[0101] T2in is the cold-side inlet temperature, in Kelvin (K).

[0102] A1 represents the heat exchange area on the hot side, in m2.

[0103] Step 3: For the air-to-air heat exchanger at different temperatures, pressures, and flow rates on the hot and cold sides, take the logarithm of the hot-side Reynolds number Re1, cold-side Reynolds number Re2, and heat transfer per unit area per unit temperature difference, in order to reduce the nonlinearity between the heat transfer and the cold and hot-side Reynolds numbers. Then, perform polynomial fitting to obtain the thermodynamic characteristics of the air-to-air heat exchanger.

[0104] For air-to-air heat exchangers, under different temperatures, pressures, and flow rates on the hot and cold sides, calculate the hot-side Reynolds number Re1, cold-side Reynolds number Re2, and heat transfer per unit area per unit temperature difference, using a logarithmic method with base 10:

[0105] X = log(Re1);

[0106] Y = log(Re2);

[0107] Z = log(QTA);

[0108] in,

[0109] X, Y, and Z are the logarithms of the hot-side Reynolds number Re1, the cold-side Reynolds number Re2, and the heat transfer per unit area per unit temperature difference, QTA.

[0110] The recommended form of the fitting polynomial is:

[0111] ;

[0112] in,

[0113] p00, p10, p01, p20, p11, and p02 are the fitting coefficients that are yet to be determined.

[0114] Two-dimensional interpolation can be used to calculate. The values ​​are obtained by taking the X, Y, and Z values ​​of the air-to-air heat exchanger at different temperatures, pressures, and flow rates on the cold and hot sides as known conditions. The values ​​are obtained by using a column vector form and two-dimensional linear interpolation for the new X0 and Y0. For example, using the griddata function in MATLAB, Z0 = griddata(X,Y,Z, X0,Y0,'linear').

[0115] In a specific example, the surface form of the thermodynamic characteristics of an air-to-air heat exchanger obtained by polynomial fitting is as follows: Figure 6 As shown.

[0116] Based on the above-described method for determining the thermodynamic characteristics of an air-to-air heat exchanger, this application provides a method for calculating the heat transfer capacity of an air-to-air heat exchanger.

[0117] The first step is to calculate the hot-side Reynolds number Re1 and the cold-side Reynolds number Re2 of the air-to-air heat exchanger. The calculation requires relevant parameters, which can be set or measured.

[0118] The second step is to calculate the logarithms X and Y of the hot-side Reynolds number Re1 and the cold-side Reynolds number Re2 of the air-to-air heat exchanger.

[0119] In three steps, based on X and Y, the logarithm Z of the heat transfer per unit area per unit temperature difference of the air-to-air heat exchanger is calculated using the thermodynamic characteristics of the air-to-air heat exchanger obtained by polynomial fitting.

[0120] Four steps: Calculate the heat exchange capacity Q of the air-to-air heat exchanger based on Z.

[0121] .

[0122] In practical applications, Z can be log(QTA), or other indicators representing heat exchange capacity can be selected, such as heat exchange per unit inlet temperature difference per unit heat exchange area (QTA), heat exchange Q, heat exchanger efficiency, heat exchange per unit temperature difference, etc.

[0123] In a specific example, the test results of 47 operating points of the air-to-air heat exchanger are compared with the heat transfer results calculated from the thermodynamic characteristics. Figure 7 As shown, the average deviation is 7% and the maximum deviation is 15%, which meets the needs of engineering calculations and evaluations. This indicates that the above calculation method for the heat exchange of air-to-air heat exchangers is effective and can obtain relatively accurate heat exchange data.

[0124] The above-described method for determining the thermodynamic characteristics of air-to-air heat exchangers is as follows:

[0125] The design of the air-to-air heat exchanger heat exchange characteristic test considers the minimum and maximum values ​​of six dimensions of parameters under full operating conditions. The test state points of each variable are randomly generated within the range of minimum and maximum values, which effectively ensures the validity of the six-dimensional test state parameters and can cover the operating conditions of the heat exchanger under full operating conditions.

[0126] The flow rates on the hot and cold sides of the air-to-air heat exchanger are dimensionless, and QTA is defined as the heat transfer per unit inlet temperature difference per unit heat exchange area. A dimensionless correspondence between the heat transfer and the flow rates on the hot and cold sides is established. The nonlinearity of the correspondence is reduced by logarithmic operations, and a fitting correlation with six undetermined coefficients is designed. This effectively corresponds to the six dimensions of the heat exchanger (hot side inlet temperature, hot side inlet pressure, hot side flow rate, cold side inlet temperature, cold side inlet pressure, and cold side flow rate), enabling high-precision fitting of the heat transfer characteristics of the air-to-air heat exchanger.

[0127] The obtained thermodynamic characteristics of the air-to-air heat exchanger can be easily embedded into the calculation program of the aero-engine thermal management system. It can accurately iteratively calculate the heat transfer of the air-to-air heat exchanger according to the state of the aero-engine, and realize the coupled calculation of the air-to-air heat exchanger component and the aero-engine thermal management system.

[0128] Furthermore, the method for determining the thermodynamic characteristics of air-to-air heat exchangers disclosed above is also applicable to heat exchangers such as fuel-to-air heat exchangers and air-to-oil radiators, where the medium on one side is air.

[0129] The technical solution of this application has been described in conjunction with the preferred embodiments shown in the accompanying drawings. Those skilled in the art should understand that the scope of protection of this application is obviously not limited to these specific embodiments. Without departing from the principles of this application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of this application.

Claims

1. A method for determining the thermodynamic characteristics of an air-to-air heat exchanger, characterized in that, include: Step 1: Conduct component-level heat transfer characteristic tests on the air-to-air heat exchanger to obtain the heat transfer capacity of the air-to-air heat exchanger under different temperatures, pressures, and flow rates on the cold and hot sides; Step 2: Calculate the Reynolds number Re1 on the hot side, Re2 on the cold side, and the heat transfer per unit area per unit temperature difference for the air-to-air heat exchanger under different temperatures, pressures, and flow rates on the cold and hot sides. Step 3: For the air-to-air heat exchanger at different temperatures, pressures, and flow rates on the hot and cold sides, take the logarithm of the hot-side Reynolds number Re1, the cold-side Reynolds number Re2, and the heat transfer per unit area per unit temperature difference QTA, and then perform polynomial fitting to obtain the thermodynamic characteristics of the air-to-air heat exchanger. X = log(Re1); Y = log(Re2); Z = log(QTA); in, X, Y, and Z are the logarithms of the hot-side Reynolds number Re1, the cold-side Reynolds number Re2, and the heat transfer per unit area per unit temperature difference, QTA. The fitted polynomial is in the form of: ； in, p00, p10, p01, p20, p11, and p02 are the fitting coefficients that are yet to be determined. In step one, mass flow measurement points are arranged at the inlet of the air-to-air heat exchanger on both the cold and hot sides, and temperature and pressure measurement points are arranged at the inlet and outlet. Based on the six parameters of the air-to-air heat exchanger—hot side inlet temperature, hot side inlet pressure, hot side flow rate, cold side inlet temperature, cold side inlet pressure, and cold side flow rate—and their potential ranges in actual use, a six-factor DOE test scheme is designed. The calculation of heat exchange capacity for air-to-air heat exchangers is as follows: Q = qm1 × △T1; in, Q represents the heat exchange rate; qm1 is the hot-side flow rate; △T1 is the temperature difference between the inlet and outlet on the hot side; Step two includes: ； ； ； in, de1 is the equivalent diameter of the flow channel within the hot-side core; Ac1 is the heat flow area on the hot side; μ1 is the thermal dynamic viscosity; qm2 is the cold side flow rate; de2 is the equivalent diameter of the flow channel inside the cold-side core; Ac2 is the cold-side flow area; μ2 is the cold-side dynamic viscosity; T1in is the inlet temperature on the hot side; T2in is the cold-side inlet temperature; A1 represents the heat exchange area on the hot side.

2. A method for calculating the heat transfer capacity of an air-to-air heat exchanger, characterized in that, include: The first step is to calculate the hot-side Reynolds number Re1 and the cold-side Reynolds number Re2 of the air-to-air heat exchanger. The calculation requires relevant parameters, which can be set or measured. The second step is to calculate the logarithms X and Y of the hot-side Reynolds number Re1 and the cold-side Reynolds number Re2 of the air-to-air heat exchanger. The three steps are as follows: Based on X and Y, the thermodynamic characteristics of the air-to-air heat exchanger are obtained by polynomial fitting using the method for determining the thermodynamic characteristics of the air-to-air heat exchanger as described in claim 1, and the logarithm Z of the heat transfer per unit area per unit temperature difference of the air-to-air heat exchanger is calculated. Four steps: Calculate the heat exchange capacity Q of the air-to-air heat exchanger based on Z.

3. The method for calculating the heat transfer capacity of an air-to-air heat exchanger according to claim 2, characterized in that, The four steps are as follows: 。

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