Experimental device for measuring convective heat transfer coefficient of surface of test piece and calculation method

Abstract

The invention provides an experimental device for measuring the convective heat transfer coefficient of the surface of a test piece and a calculation method, and relates to the technical field of convective heat transfer analysis of the surface of a structure. The experimental device comprises a box body and a measuring unit, the box body is further provided with a fluid inlet and a fluid outlet, and a flat plate test piece is vertically arranged in the box body; the surface extension direction is consistent with the fluid flowing direction, and the measuring units are installed on the two sides of the flat plate test piece and used for accurately measuring the space-time distribution of the environment temperature in the box body, the surface temperature distribution of the flat plate test piece, the incoming flow velocity distribution and the thermoelectric effect of the surface of the flat plate test piece. According to the experimental device and the calculation method, through the synergistic effect of the fluid inlet and the fluid outlet, the clamping block in the measuring unit exchanges different flat plate test pieces, and the surface convective heat transfer coefficients of various flat plate test pieces under different working conditions are measured. The device is simple in overall structure, and the independence and purity of the heat exchange process between the tested piece and the fluid and the authenticity of simulated fluid flow in a test system are fully ensured.

Description

Technical Field

[0001] The invention relates to the technical field of structural surface convection heat transfer analysis, and in particular to an experimental device and a calculation method for measuring a specimen surface convection heat transfer coefficient. Background Art

[0002] Convection is one of the three basic heat transfer modes. In engineering, it is common to see that a fluid flows through a solid and generates heat transfer between its surface. This process is called convection heat transfer, and the convection heat transfer coefficient is used to reflect the heat transfer capacity. As a cross product of fluid dynamics and thermodynamics, this technical indicator has a complex physical basis. Its optimization and control represent the exploration of energy utilization in modern engineering. Calculating and optimizing the convection heat transfer coefficient has important application value in improving energy efficiency, reducing energy consumption, promoting the development of materials science and manufacturing processes, and supporting high-precision simulation and digital twin technology.

[0003] In basic research on heat transfer, flat plate structures are highly regular and universal, and therefore are widely used as typical models for analyzing convective heat transfer. The calculation and optimization of the convective heat transfer coefficient of flat plates provide a theoretical basis for engineers and promote technological breakthroughs from nanoscale heat transfer materials to industrial-grade heat exchange equipment. For the convective heat transfer problem of swept flat plates, empirical formulas are usually relied on to estimate the heat transfer coefficient at this stage. These empirical formulas are usually based on fitting data under specific experimental conditions, and often make simplified assumptions about factors such as flow state, boundary layer characteristics, and changes in physical parameters. Due to the limitations of these formulas in breadth and applicability, when applied to flat plate specimens under different flow patterns, temperature gradients, or pressure environments, large uncertainties are easily generated, resulting in limited accuracy and robustness of the heat transfer coefficient calculation results.

[0004] Therefore, how to meet the requirements of solving the convective heat transfer coefficient with high precision under complex or changing working conditions has become a technical problem that needs to be solved urgently by technical personnel in this field. Summary of the invention

[0005] In view of this, one of the purposes of the present invention is to provide an experimental device for measuring the convective heat transfer coefficient of a specimen surface, so as to solve the technical problem in the prior art that the requirements for solving the convective heat transfer coefficient with high precision cannot be met under complex or changing working conditions.

[0006] A second object of the present invention is to provide a method for calculating the convective heat transfer coefficient of a test piece surface using an experimental device.

[0007] To achieve one of the above objects, the present invention provides an experimental device for measuring the convective heat transfer coefficient of a specimen surface. The specimen is set as a flat specimen, including a box body and a measuring unit disposed inside the box body. The box body is further provided with a fluid inlet and a fluid outlet. The flat specimen is vertically disposed inside the box body, and the extending direction of its surface is consistent with the fluid flow direction. The measuring unit is installed on both sides of the flat specimen and is used to accurately measure the spatio-temporal distribution of the environmental temperature inside the box body, the surface temperature distribution of the flat specimen, the oncoming flow velocity distribution, and the thermoelectric effect on the surface of the flat specimen.

[0008] Optionally, the measuring unit includes a temperature sensing element, an anemometer, and a thermopile patch. The temperature sensing element and the thermopile patch are simultaneously disposed on both sides of the flat specimen. The anemometer is located in the fluid flow direction and is close to the fluid inlet.

[0009] Optionally, the temperature sensing element includes a specimen temperature sensing element and an environmental temperature sensing element. The specimen temperature sensing element includes several, which are disposed on the surface of the flat specimen at a preset distance interval. The environmental temperature sensing element includes several, which are located on both sides of the flat specimen.

[0010] Optionally, the measuring unit further includes a clamping block and a backing plate. The backing plate is horizontally laid on the bottom surface of the box body. The flat specimen is disposed on the backing plate. The clamping block is disposed on both sides of the flat specimen along the fluid flow direction.

[0011] Optionally, an inlet fan and a heating element are provided at the fluid inlet of the box body, and an outlet fan is provided at the fluid outlet of the box body.

[0012] Optionally, there are two fluid inlets, which are located on the side wall of the box body and are arranged one above the other. There are two fluid outlets, which are located on the side wall of the box body opposite to the fluid inlet and are arranged one above the other, and are disposed opposite to the fluid inlet.

[0013] To achieve the second of the above objects, the present invention provides a calculation method for measuring the convective heat transfer coefficient of a specimen surface by using any one of the above experimental devices, including the following steps:

[0014] Step S1: Set the working conditions through the experimental device, and calculate the measured convective heat transfer coefficient, Nusselt number, Reynolds number, and Prandtl number based on the measured working condition data;

[0015] Step S2: Based on the power function form of the established criterion, perform regression analysis to calculate the working condition characteristic equation;

[0016] Step S3: Set a new working condition, and calculate the theoretical convective heat transfer coefficient based on the new measured working condition data and the working condition characteristic equation;

[0017] Step S4: Calculate the deviation between the theoretical convective heat transfer coefficient and the measured convective heat transfer coefficient. If it is within the interval, record the characteristic equation of the working condition as the correction formula for the convective heat transfer coefficient; otherwise, combine the previously set working condition parameters, expand the regression sample, and perform multi-condition regression analysis on the characteristic equation of the working condition until the convective heat transfer coefficient deviation calculated by the newly set working condition parameters is within the interval.

[0018] Optionally, the working condition is set in step S1 through the experimental device as follows:

[0019] Based on the experimental device, generate a fluid with a specific temperature and flow rate through the fluid inlet of the box and introduce it into the interior of the box. Denote each working condition as i = 1, 2, 3...;

[0020] Based on the discrete data measured under different working conditions by the measurement unit, respectively obtain the spatio-temporal distribution function t of the internal environment temperature of the box f 、the surface temperature distribution function t of the flat specimen w 、the incoming flow velocity distribution function u and the surface thermoelectric potential difference function V of the flat specimen;

[0021] According to the nominal sensitivity S of the thermopile patch and Newton's cooling formula, calculate the measured convective heat transfer coefficient α:

[0022]

[0023] In step S1, the measured convective heat transfer coefficient, Nusselt number, Reynolds number, and Prandtl number are calculated based on the measured working condition data as follows:

[0024] Through the relevant continuous functions under different working conditions, respectively calculate the Nusselt number Nu i 、the Reynolds number Re i and the Prandtl number Pr i :

[0025] and

[0026] where α i is the measured convective heat transfer coefficient under different working conditions, l is the Euclidean distance from the center position of the thermopile patch to the origin in the reference coordinate system of the flat specimen, u i is the incoming flow velocity under different working conditions, v i represents the kinematic viscosity under different working conditions, μ i is the dynamic viscosity under different working conditions, is the specific heat capacity at constant pressure under different working conditions, λ i is the thermal conductivity under different working conditions.

[0027] Optionally, based on the power function form of the established criterion in step S2, the gas flow state is discriminated by the Reynolds number using the working condition data measured and calculated in step S1, and the characteristic equation of the working condition is calculated by regression analysis:

[0028]

[0029] where Nu i , Re i , Pr i are the values calculated under different working conditions in step S1, and the six parameters C1, n1, m1, C2, n2, and m2 are the corresponding values calculated by regression analysis.

[0030] Optionally, in step S4, the deviation δ k ' between the calculated theoretical convective heat transfer coefficient α k and the measured convective heat transfer coefficient α k is calculated as follows:

[0031]

[0032] If δ k ≤ 15%, then the characteristic equation of the working condition obtained in step S3 is the correction formula for the convective heat transfer coefficient of the flat plate specimen; otherwise, the working conditions k = 1, 2, 3... are incorporated into the working conditions i = 1, 2, 3..., the regression sample set is expanded, and multi-working condition regression analysis is performed. Steps S1 - S4 are repeated until the deviation δ between the theoretical convective heat transfer coefficient and the measured convective heat transfer coefficient is ≤ 15%.

[0033] The experimental device and calculation method for measuring the convective heat transfer coefficient of the specimen surface provided by the present invention have the following technical effects:

[0034] The experimental device and method of the present invention have universality: through the coordinated action of the fluid inlet and the fluid outlet, different flat plate specimens are clamped and exchanged by the clamping blocks in the measuring unit, and the surface convective heat transfer coefficients of various flat plate specimens under different working conditions are measured. The overall structure of the device is simple, the box body has heat insulation properties, the fluid flow in the test system is uniform and continuous, which fully ensures the independence and purity of the heat transfer process between the tested specimen and the fluid, and the authenticity of the simulated fluid flow in the test system.

[0035] The experimental principle is simple and the operability is strong: the experimental device and method of the present invention calculate the convective heat transfer coefficient based on Newton's cooling law and the power function form of the established criterion, and the experimental principle is simple. This method only needs to measure four parameters, namely the internal environment temperature of the box body, the surface temperature of the flat plate specimen, the incoming flow velocity, and the surface thermoelectric potential difference of the flat plate specimen, and then the correction formula for the surface convective heat transfer coefficient of the flat plate specimen can be processed and calculated, which simplifies the experimental system and the data processing process and has strong operability.

[0036] Reduces the calculation uncertainty of the convective heat transfer coefficient: The experimental device and method of the present invention calculate the characteristic equations of the flat plate specimens under different working conditions for different flat plate specimens, obtain the correction formula for the convective heat transfer coefficient of the specific flat plate specimen, reduce the calculation uncertainty of the convective heat transfer coefficient of the flat plate specimen under different working conditions, effectively solve the problem that there will be a large iterative error when substituting its calculation result as the thermal boundary condition into the subsequent numerical analysis calculation, and improve the overall calculation accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0038] Figure 1 is a three-dimensional structural schematic diagram of a preferred embodiment of the experimental device of the present invention;

[0039] Figure 2 is Figure 1 the perspective structural schematic diagram of the experimental device in

[0040] Figure 3 is Figure 1 another three-dimensional structural schematic diagram of the experimental device in

[0041] Figure 4 is Figure 3 the perspective structural schematic diagram of the experimental device in

[0042] Figure 5 is the flow chart of the experimental and calculation method of the present invention.

[0043] Among them, Figures 1-5 :

[0044] 1. Box body; 11. Fluid inlet; 12. Fluid outlet;

[0045] 2. Flat plate specimen;

[0046] 3. Measuring unit; 31. Specimen temperature sensing element; 32. Ambient temperature sensing element; 33. Anemometer; 34. Thermopile patch; 35. Pad; 36. Clamping block;

[0047] 4. Heating element; 5. Inlet fan; 6. Outlet fan. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other implementation manners obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope protected by the present invention.

[0049] Based on the defects described in the background art, the following will specifically combine the attached Figures 1-5 Describe in detail the experimental device and calculation method for measuring the convective heat transfer coefficient of the surface of the test piece of the present invention.

[0050] As Figures 1-4 shown, it is a schematic structural diagram of a preferred embodiment of the experimental device for measuring the convective heat transfer coefficient of the surface of the test piece of the present invention. Among them, the test piece is preferably a flat test piece 2. The length of the flat test piece 2 is L, the width is d, and the height is h. Select the point O as shown in Figure 4 shown as the origin of the reference coordinate system, and record the coordinate positions of each temperature sensor, flow velocity measurement point, and the center of the thermopile patch 34 in this reference system.

[0051] The experimental device of a preferred embodiment of the present invention includes a box body 1 and a measurement unit 3. The measurement unit 3 is located inside the box body 1. The box body 1 is also provided with a fluid inlet 11 and a fluid outlet 12. The flat test piece 2 is vertically arranged inside the box body 1, and the extending direction of its surface is consistent with the fluid flow direction. The measurement unit 3 is installed on both sides of the flat test piece 2 for accurately measuring the spatio-temporal distribution of the environmental temperature inside the box body 1, the surface temperature distribution of the flat test piece 2, the oncoming flow velocity distribution, and the thermoelectric effect on the surface of the flat test piece 2.

[0052] The box body 1 of this embodiment can effectively isolate the thermal radiation interference from the external environment, ensuring the independence and purity of the heat transfer process between the flat test piece 2 to be measured and the fluid inside the box body 1.

[0053] Specifically, as Figure 2 and Figure 4 shown, the measurement unit 3 includes a temperature sensing element, an anemometer 33, a thermopile patch 34, a clamping block 36, and a backing plate 35. The temperature sensing element and the thermopile patch 34 are simultaneously arranged on both sides of the flat test piece 2. The anemometer 33 is located in the fluid flow direction and is close to the fluid inlet 11. The backing plate 35 is horizontally laid on the bottom surface of the box body 1. The flat test piece 2 is arranged on the backing plate 35. The clamping blocks 36 are arranged on both sides of the flat test piece 2 along the fluid flow direction.

[0054] The flat test piece 2 of this embodiment is fixed front and back by the clamping blocks 36 on both sides, so that the fluid forms an approximate flat plate flow state on both sides of the flat test piece 2.

[0055] Among them, the temperature sensing elements include the specimen temperature sensing element 31 and the ambient temperature sensing element 32. There are several specimen temperature sensing elements 31, which are arranged on the surface of the flat specimen 2 at a preset distance interval. There are several ambient temperature sensing elements 32, which are respectively located on both sides of the flat specimen 2.

[0056] Through the integrated specimen temperature sensing element 31, ambient temperature sensing element 32, anemometer 33 and thermopile patch 34, the spatio-temporal distribution of the ambient temperature in the box body 1, the surface temperature distribution of the specimen, the flow velocity distribution of the incoming flow and the thermoelectric effect on the surface of the specimen can be accurately measured respectively.

[0057] Continue to refer to Figure 2 and Figure 4 As shown, an inlet fan 5 and a heating element 4 are provided at the fluid inlet 11 of the box body 1, and an outlet fan 6 is provided at the fluid outlet 12 of the box body 1.

[0058] The inlet fan 5, outlet fan 6 and heating element 4 can cooperate to generate a fluid with a specific temperature and flow velocity. The fluid is introduced into the interior of the box body 1 and passes through the measurement unit 3 and the fluid outlet 12 in sequence. The outlet fan 6 arranged at the fluid outlet 12 is used to discharge the fluid inside the box body 1 to avoid the interference of fluid backflow on the experimental results.

[0059] The fluid inlet 11 of this embodiment includes two, which are located on the side wall of the box body 1 and are arranged one above the other. The fluid outlet 12 includes two, which are located on the side wall of the box body 1 opposite to the fluid inlet 11 and are arranged one above the other, facing the fluid inlet 11.

[0060] Since the fluid inlet 11 is divided into upper and lower parts, each part is equipped with an inlet fan 5 and a heating element 4 to cooperate in controlling the flow velocity and temperature of the blown-in fluid, so as to change the gradient distribution of the temperature and flow velocity inside the box body 1 in the vertical direction; the fluid outlet 12 is also divided into upper and lower parts, and each part is equipped with an outlet fan 6, and the arrangement of the outlet fan 6 is aligned with the position of the fluid inlet 11 to ensure the uniformity and continuity of the fluid flow inside the box body 1.

[0061] The calculation method for measuring the convective heat transfer coefficient on the surface of the specimen provided by the present invention, as Figure 5 shown, includes the following steps:

[0062] Step 1: Install the flat specimen 2. The measurement unit 3 is symmetrically installed on both sides of the flat specimen 2 and is fixed front and back by means of the clamping block 36 to make the fluid form an approximate flat plate flow state on both sides of the flat specimen 2.

[0063] Step 2: Adjust the positions of the temperature sensing element, ambient temperature sensing element 32, anemometer 33, and thermopile patch 34 of the flat specimen in the measurement unit 3, so that the integrated system can reflect the spatio-temporal fluctuations of the ambient temperature, the surface temperature distribution of the specimen, the oncoming flow velocity distribution, and the thermoelectric effect at a certain position on the specimen surface, and record the coordinate values of the corresponding positions through the reference coordinate system set in Step 1. In particular, record the coordinate (x, y, z) of the center position of the thermopile patch 34.

[0064] Step 3: Generate a fluid with a specific temperature and flow rate through the fluid inlet 11 and introduce it into the interior of the box 1. Denote each working condition as i = 1, 2, 3,.... Based on the discrete data measured under different working conditions by the measurement unit 3, respectively obtain the spatio-temporal distribution function t of the ambient temperature inside the box 1 through regression analysis f 、the surface temperature distribution function t of the specimen w 、the oncoming flow velocity distribution function u, and the thermoelectric potential difference function V on the specimen surface. According to the nominal sensitivity S of the thermopile patch 34 and Newton's cooling formula, calculate the measured convective heat transfer coefficient α:

[0065]

[0066] Step 4: Based on the continuous functions under different working conditions described in Step 3 and the Euclidean distance from the center position of the thermopile patch 34 to the origin in the reference coordinate system Calculate the Nusselt number Nu under different working conditions respectively based on heat transfer i 、the Reynolds number Re i and the Prandtl number Pr i .

[0067] Step 5: Based on the power function form of the established criterion, use the working condition data measured and calculated in Steps 3 and 4 to determine the gas flow state through Reynolds number discrimination, and perform regression analysis to calculate the working condition characteristic equation:

[0068]

[0069] In the formula, the six parameters C1, n1, m1, C2, n2, and m2 are the corresponding values calculated through regression analysis.

[0070] Step 6: Set a fluid with a temperature and flow rate different from that of working condition i through the fluid inlet 11 and introduce it into the interior of the box 1, and denote each working condition as k = 1, 2, 3,.... Correspondingly, the measured convective heat transfer coefficient that can be calculated under each working condition is denoted as α k , the Reynolds number is denoted as Re k 、the Prandtl number is denoted as Pr k . According to the working condition characteristic equation calculated in Step 5, take the Nusselt number Nu k as the parameter to be solved:

[0071]

[0072] Step 7: According to the obtained Nusselt numbers Nu under different working conditions k calculate the theoretical convective heat transfer

[0073]

[0074] Step 8: Calculate the theoretical convective heat transfer coefficient α k ' and the deviation δ from the measured convective heat transfer coefficient α k k :

[0075]

[0076] Step 9: If δ k ≤15%, record the characteristic equation of the working condition obtained in Step 5 as the correction formula for the convective heat transfer coefficient of this flat plate specimen 2; otherwise, incorporate the working conditions k = 1, 2, 3... into the working conditions i = 1, 2, 3..., expand the regression sample set, perform multi - working - condition regression analysis, and repeat Steps 3, 4, 5, 6, 7, 8, 9 until the deviation δ between the theoretical convective heat transfer coefficient and the measured convective heat transfer coefficient is ≤15%.

[0077] In the description of the present invention, it should be noted that unless otherwise specified, the meaning of "a plurality of" is two or more; the orientation or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0078] In the description of the present invention, it should also be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected to" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0079] ​The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims described above.

Claims

1. An experimental device for measuring the convective heat transfer coefficient of a specimen surface, characterized in that: The specimen is set as a flat specimen, including a box body and a measuring unit arranged in the box body. The box body is also provided with a fluid inlet and a fluid outlet. The flat specimen is vertically arranged in the box body, and its surface extension direction is consistent with the fluid flow direction. The measuring unit is installed on both sides of the flat specimen, and is used to accurately measure the temporal and spatial distribution of the ambient temperature in the box body, the surface temperature distribution of the flat specimen, the incoming flow velocity distribution and the thermoelectric effect of the surface of the flat specimen.

2. The experimental device for measuring the convective heat transfer coefficient of the specimen surface according to claim 1, characterized in that: The measuring unit comprises a temperature sensing element, an anemometer and a thermopile patch. The temperature sensing element and the thermopile patch are arranged on both sides of the flat specimen. The anemometer is located in the fluid flow direction and close to the fluid inlet.

3. The experimental device for measuring the convective heat transfer coefficient of the specimen surface according to claim 2, characterized in that: The temperature sensing elements include a specimen temperature sensing element and an environment temperature sensing element. The specimen temperature sensing elements include a plurality of elements which are arranged on the surface of the flat specimen at a preset distance. The environment temperature sensing elements include a plurality of elements which are located on both sides of the flat specimen.

4. The experimental device for measuring the convective heat transfer coefficient of the specimen surface according to claim 2, characterized in that: The measuring unit further comprises a clamping block and a pad, wherein the pad is horizontally laid on the bottom surface of the box, the flat plate specimen is arranged on the pad, and the clamping block is arranged on both sides of the flat plate specimen along the flow direction of the fluid.

5. The experimental device for measuring the convective heat transfer coefficient of a specimen surface according to claim 1, characterized in that: The fluid inlet of the box is equipped with an inlet fan and a heating element, and the fluid outlet of the box is equipped with an outlet fan.

6. The experimental device for measuring the convective heat transfer coefficient of the specimen surface according to claim 5, characterized in that: The fluid inlets include two, which are located on the side wall of the box body and are arranged one above and one below. The fluid outlets include two, which are located on the side wall of the box body opposite to the fluid inlets and are arranged one above and one below, and are arranged directly opposite to the fluid inlets.

7. A method for calculating the convective heat transfer coefficient of a test piece surface by using the experimental device according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step S1: setting the working conditions through the experimental device, and calculating the measured convective heat transfer coefficient, Nusselt number, Reynolds number and Prandtl number based on the measured working condition data; Step S2: Based on the power function form of the predetermined criterion, regression analysis is performed to calculate the operating condition characteristic equation; Step S3: setting a new working condition, and calculating the theoretical convection heat transfer coefficient based on the working condition characteristic equation through the newly measured working condition data; Step S4: Calculate the deviation between the theoretical convective heat transfer coefficient and the measured convective heat transfer coefficient. If the deviation is within the interval, record the operating condition characteristic equation as the convective heat transfer coefficient correction formula; Otherwise, the previously set operating parameters are merged, the regression sample is expanded, and the operating characteristic equation is analyzed by multi-operating condition regression until the deviation of the convective heat transfer coefficient calculated by the newly set operating parameters is within the interval.

8. The calculation method according to claim 7, characterized in that: In step S1, the operating conditions are set by the experimental device as follows: Based on the experimental device, a fluid with a specific temperature and flow rate is generated through the fluid inlet of the box and introduced into the box, and each working condition is recorded as i=1,2,3...; Based on the discrete data under different working conditions measured by the measuring unit, the temporal and spatial distribution function t of the ambient temperature inside the box is obtained based on regression analysis. f , surface temperature distribution function of the flat specimen t w , the incoming flow velocity distribution function u and the surface thermoelectric potential difference function V of the flat specimen; According to the nominal sensitivity S of the thermopile patch and the Newton cooling formula, the measured convective heat transfer coefficient α is calculated: In step S1, the measured convective heat transfer coefficient, Nusselt number, Reynolds number and Prandtl number are calculated based on the measured operating data as follows: Through the relevant continuous functions under different working conditions, the Nusselt number Nu under different working conditions is calculated based on heat transfer. i , Reynolds number Re i and the Prandtl number Pr i : as well as Where α i is the measured convective heat transfer coefficient under different working conditions, l is the Euclidean distance from the center of the thermopile patch to the origin in the reference coordinate system of the flat specimen, u i is the incoming flow velocity under different working conditions, v i Indicates the kinematic viscosity under different working conditions, μ i is the dynamic viscosity under different working conditions, is the constant pressure specific heat capacity under different working conditions, λ i is the thermal conductivity under different working conditions.

9. The calculation method according to claim 8, characterized in that: In step S2, based on the power function form of the predetermined criterion, the operating condition data measured and calculated in step S1 are used to calculate the gas flow state determined by the Reynolds number, and the operating condition characteristic equation is calculated by regression analysis: Where Nu i 、Re i , Pr i are the values ​​calculated under different working conditions in step S1, and the six parameters C1, n1, m1, C2, n2 and m2 are the corresponding values ​​calculated using regression analysis.

10. The calculation method according to claim 9, characterized in that: The step S4 calculates the theoretical convection heat transfer coefficient α k ' and the measured convective heat transfer coefficient α k Deviation δ k : If δ k ≤15%, then the operating condition characteristic equation obtained in step S3 is the correction formula for the convective heat transfer coefficient of the flat plate specimen; On the contrary, the working condition k=1,2,3... is incorporated into the working condition i=1,2,3..., the regression sample set is expanded, and multi-working condition regression analysis is performed, and steps S1-S4 are repeated until the deviation δ between the theoretical convective heat transfer coefficient and the measured convective heat transfer coefficient is ≤15%.

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