A method and apparatus for visualizing critical heat flux experiments

Abstract

The application discloses a visual critical heat flux density test method and device, and belongs to the field of thermal hydraulic test.The visual critical heat flux density test method comprises the following steps: providing a CHF test device with a transparent heater; synchronously collecting infrared signal distribution data and bubble distribution image data of the transparent heater; establishing a heat conduction / radiation heat transfer coupling model of the transparent heater; calculating temperature distribution data of the transparent heating film according to the infrared signal distribution data; combining the temperature distribution data of the transparent heating film surface with the bubble distribution image data to determine the position of boiling phenomenon and the temperature of the transparent heating film at the corresponding moment during the test process.The method can effectively improve the accuracy of the CHF visual test.

Description

Technical Field

[0001] This invention belongs to the field of thermal hydraulic testing, specifically relating to a method and apparatus for visualizing critical heat flux density testing. Background Technology

[0002] In nuclear engineering, high heat flux density heat transfer structures, and related research fields, the critical heat flux (CHF) is one of the main parameters for evaluating the thermal safety margin of a system. Its magnitude is directly related to the fuel cladding temperature level, coolant heat transfer capacity, and safety margin under accident conditions. Therefore, accurately obtaining and predicting the critical heat flux is of great significance for the engineering design, safe operation analysis, and accident prevention of nuclear reactors.

[0003] In advanced nuclear energy systems such as high-flux research reactors and small modular reactors, as well as other heat exchange equipment that performs heat transfer and exchange functions, heat exchange structures with rectangular or annular narrow-gap flow channels are widely used. This type of flow channel exhibits significant advantages in engineering applications: firstly, it achieves equipment miniaturization and structural compactness through a high specific surface area, meeting the strict constraints of nuclear energy systems on volume and layout space; secondly, the manufacturing process for this type of structure is relatively mature and easy to process and shape. This type of structure has significant advantages such as high heat exchange efficiency, large effective heat exchange area, deep fuel burnup, and compact structure, and can meet the stringent requirements for cooling performance under high power density conditions.

[0004] Current research on critical heat flux density still heavily relies on simulation experiments. These experiments involve heating cooling water to the point of CHF (critical heat flux density) under simulated heating conditions, and then measuring the location of CHF occurrence and various physical parameters. Currently, CHF experiments generally rely on non-visual temperature measurements, and the results are highly dependent on the placement and density of temperature sensors (thermocouple spacing can typically be at the centimeter level). This makes it difficult to accurately obtain the wall temperature field during the experiment and to characterize the non-uniform spatial evolution of the heat load during CHF occurrence.

[0005] Some technical solutions attempt to introduce infrared thermal imaging and other techniques to visualize and measure the CHF process. However, during the experiment, the infrared measurement signal is simultaneously affected by changes in wall heat conduction, surface radiation characteristics, and the coupling effect of convection and phase change heat transfer on the coolant side. This leads to a significant deviation between the apparent temperature obtained by infrared measurement and the true wall temperature. Furthermore, in existing visualized boiling and CHF experiments, the wall heat flux density is usually calculated by averaging the input electrical power and the nominal heating area. This method essentially only obtains the overall average heat flux density and cannot reflect the non-uniform heating characteristics of the inner wall of the narrow rectangular channel in the flow direction and lateral direction. In particular, it cannot characterize the key features of the evolution of local heat load in time and space before the critical heat flux density occurs. Moreover, visualization measurement and heating electrical parameter acquisition methods usually operate independently, lacking a unified time synchronization and data correlation mechanism. This makes it difficult to accurately correlate and analyze different physical quantities at the same time scale and spatial location, thus making it difficult to establish a reliable quantitative correlation between wall thermal behavior and vapor-liquid two-phase flow behavior.

[0006] Therefore, providing an experimental method based on visualization experiments that can accurately calculate parameters related to critical heat flux density is of positive significance for improving the accuracy and reliability of visualization critical heat flux density experiments. Summary of the Invention

[0007] A method for visualizing critical heat flux density (CHF) testing is provided to improve the accuracy of CHF visualization tests. The invention also provides a device for calculating critical heat flux density based on visualization testing.

[0008] According to one embodiment of the present invention, a method for visualizing critical heat flux density is provided, the method comprising the following steps:

[0009] Step a): Provide a CHF testing apparatus, which includes a simulated flow channel and a transparent heater. The simulated flow channel contains flowing cooling water. The transparent heater is disposed on the wall of the simulated flow channel and includes a transparent substrate and a transparent heating film. The transparent heating film is disposed on the side of the transparent substrate facing the inside of the simulated flow channel. The cooling water is heated using the transparent heater.

[0010] Step b): Acquire infrared signal distribution data of the transparent heater and bubble distribution image data on the surface of the transparent heating film, and synchronize the infrared signal distribution data and the bubble distribution image data in time;

[0011] Step c): Establish a thermal conduction / radiative heat transfer coupling model for the transparent heater, and calculate the infrared radiation intensity distribution of the transparent heating film based on the thermal conduction / radiative heat transfer coupling model and the infrared signal distribution data, and further calculate the temperature distribution data of the transparent heating film; wherein,

[0012] ,

[0013] The infrared signal intensity, The infrared radiation signal intensity of the transparent heating film. Background infrared radiation intensity, The system equivalent apparent transmittance of the transparent heater is given. This is a monotonic mapping operator defined based on the thermal conductivity of solids. for inverse function, The temperature distribution of the transparent substrate, z c A is the thickness of the transparent substrate. h Let V(t) be the area of ​​the transparent substrate, V(t) be the voltage of the transparent heater, and l(t) be the current of the transparent heater. denoted as , where is the heat flux density between the transparent heating film and the transparent substrate; c is the speed of light in a vacuum; and c² is Planck's second radiation constant. Based on the heat conduction and radiation processes, and according to the boundary conditions of the transparent heater, the temperature distribution data of the transparent heating film is calculated through coupled solution.

[0014] Step d): Based on the temperature distribution data of the transparent heating film and the bubble distribution image data, determine the location of the cooling water boiling phenomenon during the experiment and the temperature of the transparent heating film at the corresponding time.

[0015] This method overcomes the systematic error caused by directly equating the infrared apparent temperature with the actual wall temperature in existing technologies by introducing a thermal conduction / radiation coupling model to invert infrared measurement data. It can invert the local heat flux density distribution based on the actual wall temperature gradient, thereby revealing the non-uniform evolution characteristics of the heat load in space before CHF occurs. It integrates infrared measurement, electrical parameter measurement and visualization imaging data for unified analysis, so as to quantitatively describe the relationship between wall thermal behavior and vapor-liquid two-phase behavior.

[0016] Furthermore, in some embodiments, a calibration step is included before the test. In the calibration step, the transparent heating film is heated in the simulated flow channel without the cooling water, and the infrared signal distribution data of the transparent heater is collected. In step c), the temperature distribution data of the transparent heating film is verified and calculated based on the results of the calibration step.

[0017] Further, in some embodiments, the verification calculation method is as follows: In the calibration step, the transparent heating film is brought to a given temperature, and the infrared photons emitted by the transparent heater are counted using an infrared camera to establish an infrared photon count-temperature steady-state curve; in step c), within a given time step, the local distribution of the infrared photon count emitted by the transparent heater is acquired using the infrared camera, and the local temperature of the transparent heating film is predicted and calculated based on the local distribution of the infrared photon count; the temperature distribution of the transparent substrate is calculated based on the boundary conditions and the thermal conductivity relationship; the total infrared radiation intensity of the transparent heater is converted into infrared photon counts, and compared with the infrared photon count results acquired by the infrared camera; when the error exceeds a given threshold, the parameters in the thermal conduction / radiation heat transfer coupling model are updated, and iterative calculations are performed until the error does not exceed the given threshold.

[0018] Furthermore, in some embodiments, in step a), the transparent heating film is opaque in the 3μm-5μm wavelength range.

[0019] Furthermore, in some embodiments, in step a), the transparent heating film is an indium tin oxide film, and the transparent substrate is sapphire, aluminum oxynitride, or quartz glass.

[0020] Furthermore, in some embodiments, in step a), the transparent heater is respectively provided on a pair of walls of the simulated flow channel.

[0021] According to another aspect of the present invention, a visual critical heat flux density testing device is provided for use with the visual critical heat flux density testing method provided in any of the foregoing embodiments. The device includes: a simulated flow channel, an infrared camera, a high-speed camera, and a data processing device; wherein at least a portion of the wall of the simulated flow channel is configured as a transparent heater, the transparent heater comprising a transparent substrate and a transparent heating film, the transparent heating film being disposed on the side of the transparent substrate facing the interior of the simulated flow channel, and cooling water flowing within the simulated flow channel; the infrared camera acquires infrared signal distribution data of the transparent heater; the high-speed camera acquires bubble distribution image data on the surface of the transparent heating film through the transparent heater; the data processing device is signal-connected to the simulated flow channel, the infrared camera, and the high-speed camera, and determines the location and corresponding temperature of the cooling water boiling phenomenon based on the infrared signal distribution data and the bubble distribution image data.

[0022] Furthermore, in some embodiments, the transparent heaters are respectively provided on a pair of walls of the simulated flow channel.

[0023] Furthermore, in some embodiments, the data processing device includes a synchronization trigger module, a memory, and a processor. The synchronization trigger module performs time synchronization between the infrared signal distribution data and the bubble distribution image data. The memory stores a calculation program, which, when executed by the processor, can perform the calculation processes in steps c) and d) of the visualization critical heat flux density test method provided in any of the foregoing embodiments and output the calculation results. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a visual critical heat flux density test device in one embodiment;

[0025] Figure 2 This is a schematic diagram of infrared radiation and heat conduction in one embodiment;

[0026] Figure 3 This is a temperature distribution data graph from one embodiment;

[0027] Figure 4 This is a graph showing the heat flux density distribution in one embodiment;

[0028] Figure 5 This is a steady-state calibration curve in one embodiment.

[0029] Meaning of the reference numerals in the attached figures:

[0030] 101-Power supply; 102-Infrared camera; 103-High-speed camera; 104-Synchronous trigger module; 105-Electrical parameter acquisition module; 106-Memory and processor; 200-CHF test device; 201-Cooling water; 202-Transparent heating film; 203-Transparent substrate; 204-Air layer.

[0031] The purpose of the above-described drawings is to provide a detailed description of the present invention so that those skilled in the art can understand the technical concept of the invention, and is not intended to limit the invention. For the sake of brevity, the above-described drawings only schematically depict the structures related to the technical features of the present invention, and do not depict the complete structure and all details strictly according to actual scale. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0033] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment herein. The phrase appearing in various places in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive, independent, or alternative embodiments. Those skilled in the art will understand that the embodiments herein can be combined with other embodiments without causing structural conflicts.

[0034] In this description, unless otherwise explicitly specified and limited, the technical terms "installation," "connection," "joining," etc., should be interpreted broadly, for example, referring to movable connections, fixed connections, or integration. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0035] In this description, terms such as "upper," "lower," "left," "right," "lateral," "longitudinal," "height," "length," and "width," which indicate orientation or positional relationships, are intended to accurately describe the embodiments and simplify the description, rather than limiting the parts or structures involved to have a specific orientation, or to be installed or operated in a specific orientation, and should not be construed as limiting the embodiments in this document.

[0036] In this description, terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating relative importance or limiting the number, specific order, or primary / secondary relationship of the described technical features. In this description, "multiple" means at least two.

[0037] In traditional CHF (Cold Fiber Fluidization) experiments, the experimental setup is heated under non-visual conditions, requiring direct temperature measurement of different heating zones using temperature sensors. Sudden changes in the heating rate are then used to determine if a change in the heat transfer mode has occurred. This method cannot achieve complete detection of the temperature field at the interface, and the experimental accuracy depends on the density of the temperature sensors and is subject to a degree of randomness; for example, it cannot determine the specific location of the measurement point within the film boiling region. Therefore, it is difficult to further improve the measurement accuracy of CHF experiments.

[0038] To overcome the aforementioned problems of the prior art, one embodiment of the present invention provides a method for visualizing critical heat flux density testing, the method comprising the following steps:

[0039] Step a): Build as follows Figure 1 The visualized critical heat flux density (CHF) test apparatus shown includes a CHF test device 200, a power supply 101, an infrared camera 102, a high-speed camera 103, and a data processing device. The data processing device further includes a synchronous triggering module 104, an electrical parameter acquisition module 105, and a memory and processor 106. Combined with... Figure 2 The CHF testing apparatus 200 includes a simulated flow channel and a transparent heater. The simulated flow channel contains flowing cooling water 201, and the transparent heater is disposed on the wall of the simulated flow channel, allowing external observation of the state inside the simulated flow channel through the transparent heater. The transparent heater includes a transparent substrate 203 and a transparent heating film 202 disposed on the side surface of the transparent substrate 203 facing the simulated flow channel. The transparent heating film 202 is used to heat the cooling water 201, causing it to boil on the surface of the transparent heating film 202 to trigger the CHF phenomenon.

[0040] In a preferred embodiment, the transparent heating film 202 is opaque in the 3μm-5μm wavelength range to isolate the infrared radiation emitted by the cooling water 201 from interfering with the test. In a further preferred embodiment, the transparent heating film 202 is made of indium tin oxide film, which has a transmittance of over 90% in the 0.4μm-1.5μm wavelength range and is opaque in the 2.5μm-7μm wavelength range, effectively isolating the infrared radiation from the cooling water 201. The transparent substrate 203 is made of sapphire (88% transmittance in the 0.17μm-5.5μm wavelength range), aluminum oxynitride (85% transmittance in the 0.2μm-5.5μm wavelength range), or quartz glass (85% transmittance in the 0.22μm-2.5μm wavelength range). Sapphire also has excellent thermal conductivity, can withstand harsh environmental conditions, and is commonly used in infrared optical systems, operating in the near-infrared and milliwatt spectral bands; Quartz glass has good chemical stability and radiation resistance, low expansion coefficient, low fluorescence radiation, and scratch resistance.

[0041] Step b): Acquire infrared signal distribution data of the transparent heater and bubble distribution image data on the surface of the transparent heating film, and synchronize the infrared signal distribution data and bubble distribution image data in time. Specifically, use infrared camera 102 to capture infrared images of the transparent heater to acquire infrared signal distribution data, such as... Figure 3 and Figure 4 As shown, temperature distribution data and heat flux density distribution data within the plane of the transparent heater are acquired; bubble distribution image data is captured using a high-speed camera 103; further, a synchronization trigger module 104 is used to synchronize the infrared signal distribution data and bubble distribution image data in time, so that the heat transfer phenomenon can be correlated with the bubble distribution image in subsequent processing. The synchronization trigger module 104 specifically includes an NI DAQ data acquisition card, a junction box, and cables. The synchronization trigger module 104 serves as the master clock and is connected to the infrared camera 102 and the high-speed camera 103 via cables, with the infrared camera 102 and the high-speed camera 103 serving as slave devices to achieve data time synchronization.

[0042] Step c): Part of the heat generated by the transparent heater is as follows Figure 2 The black arrow indicates that the cooling water 201 is conducted inward to the simulated flow channel to produce a boiling phenomenon; another part is as follows: Figure 2 The red arrows indicate that heat is conducted outwards through conduction and radiation. Based on the self-heating of the transparent heating film 202 and its relationship with the transparent substrate 203 through conduction and radiation, a thermal conduction / radiation heat transfer coupling model for the transparent heater is established. The infrared radiation intensity distribution of the transparent heating film 202 is calculated based on this model and infrared signal distribution data. Furthermore, the temperature distribution data of the transparent heating film 202 is calculated. Specifically,

[0043] .

[0044] Where x, y, and z are spatial coordinates in a rectangular coordinate system, z is the thickness direction of the transparent heating film 202, the xy plane is the plane where the transparent heating film 202 is located, t is time, λ is wavelength, and λ2-λ1 is the measured infrared wavelength range. The total intensity of the infrared signal collected by infrared camera 102. The infrared radiation signal intensity of the transparent heating film 202. Background infrared radiation intensity, The system equivalent apparent transmittance for the transparent heater. This is a monotonic mapping operator defined based on the thermal conductivity of solids. for inverse function, The temperature distribution of the transparent substrate 203, z cA is a transparent substrate with a thickness of 203. h Let V(t) be the area of ​​the transparent substrate 203, V(t) be the voltage of the transparent heater, and l(t) be the current of the transparent heater. denoted as , where is the heat flux density between the transparent heating film 202 and the transparent substrate 203; c is the speed of light in a vacuum; and c2 is Planck's second radiation constant. Based on the heat conduction and radiation processes, and according to the boundary conditions of the transparent heater, the temperature distribution data of the transparent heating film is calculated through coupled solution.

[0045] Based on the temperature of the transparent heating film 202 and the physical parameters of the transparent substrate 203, such as heat capacity and thermal conductivity, a heat transfer model of the transparent substrate 203 can be established, and the temperature field in the transparent substrate 203 can be calculated. According to basic thermophysics, the thermal radiation intensity of the transparent substrate 203 at different temperatures can be determined. Considering transmittance, integrating the thermal radiation of the transparent substrate 203 along the thickness direction allows for the calculation of the direct radiation intensity of the transparent substrate 203. The reflected radiation intensity exhibits a convergent series and can also be obtained through basic thermophysics and mathematical calculations. The background infrared radiation intensity can be obtained through experimental measurement. Based on this, the infrared radiation intensity of the transparent heating film 202 can be calculated, and its corresponding temperature can be obtained according to the basic principles of infrared thermometry. Since the thickness of the transparent heating film 202 is very small, its temperature is considered to be uniform along the thickness direction.

[0046] Step d): Based on the bubble distribution image data captured by the high-speed camera 103 and the temperature distribution data of the transparent heating film 202 calculated in step c), determine the location where the cooling water 201 boils on the surface of the transparent heating film 202 during the experiment and the temperature state of the transparent heating film 202 in that area at the corresponding time. Further determine the location and corresponding temperature of bubble merging, deviating from the bubble nucleus boiling, and film boiling, thereby accurately determining the heat transfer conditions when the CHF phenomenon occurs.

[0047] In some embodiments, transparent heaters are respectively installed on both sides of the CHF test device 200, enabling simultaneous double-sided heating tests. For the double-sided heating test, different observation methods can be used in different embodiments. In some embodiments, high-speed cameras 103 can be installed on both sides, while an infrared camera 102 is only installed on one side. The high-speed camera 103 installed on the opposite side of the infrared camera 102 is used for auxiliary observation to better align wall temperature, heat flux density information, and bubble dynamics information. In other embodiments, both infrared cameras 102 and high-speed cameras 103 can be arranged on both sides to conduct a more comprehensive observation of the CHF phenomenon in the narrow flow channel under double-sided heating conditions.

[0048] In a preferred embodiment, a calibration step is included before conducting the formal CHF test. In the calibration step, the transparent heating film 202 is heated without cooling water in the simulated flow channel, and infrared signal distribution data of the transparent heater is collected using an infrared camera 102. Based on this data, the temperature distribution data of the transparent heating film 202 calculated in step c) is verified. Specifically, in a further preferred embodiment, the verification calculation method is as follows: First, in the calibration step, since no cooling water is filled in the simulated flow channel, the heat loss of the transparent heating film 202 only includes radiative heat transfer and conductive heat dissipation to the transparent substrate 203. Therefore, the temperature of the transparent substrate 203 can be calculated and determined relatively accurately based on the thermal conductivity / radiative heat transfer coupling model.

[0049] The infrared camera 102 counts the infrared photons emitted by the transparent heater, establishing a system as follows: Figure 5 The infrared photon counting-temperature steady-state curve shown can be obtained specifically through polynomial fitting.

[0050] Subsequently, in step c), within a given time step, the local distribution of infrared photon counts emitted by the transparent heater is acquired using the infrared camera 102. Based on the thermal conduction / radiation heat transfer coupling model, the local temperature of the transparent heating film 202 is predicted and calculated according to the local distribution of infrared photon counts under experimental conditions. The temperature distribution of the transparent substrate 203 is calculated based on the boundary conditions and the relationship of heat conduction. The calculated temperature distribution data is converted into infrared photon counts to obtain the calculated value of the infrared photon count. This calculated value is compared with the actual infrared photon counts obtained by the infrared camera 102 during the experiment. If the error exceeds a given threshold (e.g., the hardware accuracy range of the infrared camera), the parameters of the thermal conduction / radiation heat transfer coupling model are adjusted, for example, by using the conjugate gradient method for parameter optimization, and iterative calculation is performed again until the difference between the calculated value and the measured value of the infrared photon count does not exceed the given error threshold.

[0051] The methods provided in the above embodiments enable accurate measurement of the location of CHF phenomena and the changes in temperature and heat flux density during CHF occurrence. By comparing the results with those obtained by deploying thermocouples, the data error calculated by the methods provided in the above embodiments can be reduced by 10%-20% compared to methods that directly calculate temperature based on infrared images without data processing.

[0052] According to another aspect of the present invention, a visual critical heat flux density testing apparatus is provided, which is used in any of the foregoing embodiments for the visual critical heat flux density testing method. Figure 1The device includes a CHF testing apparatus 200, a power supply 101, an infrared camera 102, a high-speed camera 103, and a data processing device. The data processing device further includes a synchronous triggering module 104, an electrical parameter acquisition module 105, and a memory and processor 106. The CHF testing apparatus 200 contains a simulated flow channel, the main body of which is made of stainless steel, with at least a portion of the walls configured as transparent heaters. In a preferred embodiment, the simulated flow channel is a narrow rectangular channel, with transparent heaters installed on the walls on both horizontal sides. Flowing cooling water is provided within the simulated flow channel, and the transparent heaters heat the cooling water to trigger the CHF phenomenon. Specifically, in conjunction with... Figure 2 The transparent heater includes a transparent substrate 203, the surface of which facing the simulated flow channel is coated with a transparent heating film 202. In a preferred embodiment, the transparent substrate 203 is made of indium tin oxide film, sapphire, aluminum oxynitride, or quartz glass. A power supply 101 supplies power to the transparent heater, causing the transparent heating film 202 to heat up to the required experimental conditions. The power supply 101 is connected to an electrical parameter acquisition module 105, which acquires voltage, current, and other parameter information in real time during the experiment. An infrared camera 102 and a high-speed camera 103 are respectively positioned facing the transparent heater to acquire infrared signal data from the transparent heater and bubble distribution image data on the surface of the transparent heating film 202 in real time during the experiment. A synchronization trigger module 104 is connected to the infrared camera 102 and the high-speed camera 103 to synchronize the acquired data in time. A memory and processor 106 calculates the data acquired during the experiment and outputs the calculation results.

[0053] In one specific embodiment, the memory stores a calculation program, which specifically includes a temperature calculation module, a three-dimensional thermal conductivity solution module, a thermal conductivity / radiation coupling calculation module, and a convergence judgment module. The calculation program can be executed by a processor. When the processor executes the calculation program, the temperature calculation module calculates the apparent temperature information based on the physical model describing the CHF experimental device established by the experimenters, and uses the apparent temperature information as the initial input condition for subsequent inversion calculations. Next, the apparent temperature information is input to the thermal conductivity / radiation coupling calculation module, which performs coupled calculations on the thermal conductivity process and the surface radiation process based on the material parameters and geometric parameters of the simulated flow channel wall and the heating boundary conditions provided by the transparent heating film 202. After completing the coupled calculations, the calculation results are output to the three-dimensional thermal conductivity solution module, which solves for the temperature field and obtains the corresponding temperature distribution results. Next, the results from the 3D heat conduction solution module are output to the convergence judgment module. Based on the data obtained during the calibration steps, the initial judgment module performs verification calculations. When the error exceeds a given threshold, the calculation results are returned to the temperature calculation module or the heat conduction / radiation coupling calculation module to update the model parameters and recalculate iteratively until the error does not exceed the given threshold, thus obtaining the temperature distribution and local heat flux density distribution data of the transparent heating film 202. Furthermore, the temperature distribution and local heat flux density distribution data of the transparent heating film 202 are combined with the bubble distribution image data acquired by the high-speed camera 103 to obtain the time and location of the CHF phenomenon, as well as the temperature and heat flux density distribution data obtained when the CHF phenomenon occurs.

[0054] The purpose of the above embodiments is to provide a further detailed description of the present invention in conjunction with the accompanying drawings, so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, optimization or equivalent substitution of the technical features involved, as well as combination of implementation methods in different embodiments without causing structural and principle conflicts, all fall within the protection scope of the present invention.

Claims

1. A method for visualizing critical heat flux density experiments, characterized in that, Includes the following steps: Step a): Provide a CHF testing apparatus, which includes a simulated flow channel and a transparent heater. The simulated flow channel contains flowing cooling water. The transparent heater is disposed on the wall of the simulated flow channel and includes a transparent substrate and a transparent heating film. The transparent heating film is disposed on the side of the transparent substrate facing the inside of the simulated flow channel. The cooling water is heated using the transparent heater. Step b): Acquire infrared signal distribution data of the transparent heater and bubble distribution image data on the surface of the transparent heating film, and synchronize the infrared signal distribution data and the bubble distribution image data in time; Step c): Establish a thermal conduction / radiative heat transfer coupling model for the transparent heater, and calculate the infrared radiation intensity distribution of the transparent heating film based on the thermal conduction / radiative heat transfer coupling model and the infrared signal distribution data, and further calculate the temperature distribution data of the transparent heating film; wherein, ， x, y, and z are spatial coordinates in a rectangular coordinate system, z represents the thickness direction of the transparent heating film, the xy plane is the plane where the transparent heating film is located, t is time, λ is wavelength, and λ2-λ1 is the measured infrared wavelength range. The infrared signal distribution, The infrared radiation signal intensity of the transparent heating film. Background infrared radiation intensity, The system equivalent apparent transmittance of the transparent heater is given. This is a monotonic mapping operator defined based on the thermal conductivity of solids. for inverse function, The temperature distribution of the transparent substrate, z c A is the thickness of the transparent substrate. h Let V(t) be the area of ​​the transparent substrate, V(t) be the voltage of the transparent heater, and l(t) be the current of the transparent heater. denoted as , where is the heat flux density between the transparent heating film and the transparent substrate; c is the speed of light in a vacuum; and c² is Planck's second radiation constant. Based on the heat conduction and radiation processes, and according to the boundary conditions of the transparent heater, the temperature distribution data of the transparent heating film is calculated through coupled solution. Step d): Based on the temperature distribution data of the transparent heating film and the bubble distribution image data, determine the location of the cooling water boiling phenomenon during the experiment and the temperature of the transparent heating film at the corresponding time.

2. The method for visualizing critical heat flux density testing according to claim 1, characterized in that, Before conducting the test, a calibration step is also included. In the calibration step, the transparent heating film is heated in the simulated flow channel without the cooling water, and the infrared signal distribution data of the transparent heater is collected. In step c), the temperature distribution data of the transparent heating film is verified and calculated based on the results of the calibration step.

3. The method for visualizing critical heat flux density testing according to claim 2, characterized in that, The verification calculation method is as follows: In the calibration step, the transparent heating film is brought to a given temperature, and the infrared photons emitted by the transparent heater are counted using an infrared camera to establish an infrared photon count-temperature steady-state curve; in step c), within a given time step, the local distribution of the infrared photon count emitted by the transparent heater is acquired using the infrared camera, and the local temperature of the transparent heating film is predicted and calculated based on the local distribution of the infrared photon count; the temperature distribution of the transparent substrate is calculated based on the boundary conditions and the thermal conductivity relationship; the total infrared radiation intensity of the transparent heater is converted into infrared photon counts, and compared with the infrared photon count results acquired by the infrared camera; when the error exceeds a given threshold, the parameters in the thermal conduction / radiation heat transfer coupling model are updated, and iterative calculations are performed until the error does not exceed the given threshold.

4. The method for visualizing critical heat flux density testing according to claim 1 or 2, characterized in that, In step a), the transparent heating film is opaque in the 3μm-5μm wavelength range.

5. The method for visualizing critical heat flux density testing according to claim 4, characterized in that, In step a), the transparent heating film is made of indium tin oxide film, and the transparent substrate is made of sapphire, aluminum oxynitride, or quartz glass.

6. The method for visualizing critical heat flux density testing according to claim 1 or 2, characterized in that, In step a), the transparent heaters are respectively provided on a pair of walls of the simulated flow channel.

7. A visual critical heat flux density test apparatus, characterized in that, A method for visualizing critical heat flux density testing as described in any one of claims 1 to 6, comprising: a simulated flow channel, an infrared camera, a high-speed camera, and a data processing device; in, At least a portion of the wall of the simulated flow channel is configured as a transparent heater, the transparent heater comprising a transparent substrate and a transparent heating film, the transparent heating film being disposed on the side of the transparent substrate facing the interior of the simulated flow channel, and the simulated flow channel being provided with flowing cooling water; The infrared camera collects infrared signal distribution data of the transparent heater; The high-speed camera captures image data of the bubble distribution on the surface of the transparent heating film through the transparent heater; The data processing device is connected to the simulated flow channel, the infrared camera, and the high-speed camera signal, and determines the location and corresponding temperature of the cooling water boiling phenomenon based on the infrared signal distribution data and the bubble distribution image data.

8. The visual critical heat flux density test apparatus according to claim 7, characterized in that, The transparent heaters are respectively installed on a pair of walls of the simulated flow channel.

9. The visual critical heat flux density test apparatus according to claim 7 or 8, characterized in that, The data processing device includes a synchronization trigger module, a memory, and a processor. The synchronization trigger module performs time synchronization between the infrared signal distribution data and the bubble distribution image data. The memory stores a calculation program. When the calculation program is executed by the processor, it can perform the calculation process in steps c) and d) of the visualization critical heat flux density test method as described in any one of claims 1 to 6 and output the calculation results.

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