One-dimensional heat flux density measuring device based on Fourier law

Abstract

The invention discloses a one-dimensional heat flux density measuring device based on the Fourier law, and relates to the technical field of object heat flux density measurement. Comprising a heating unit, a sealing heat insulation unit, a cooling unit, a temperature acquisition unit and a data processing unit. The sealing heat insulation unit comprises a heat insulation material, an aluminum oxide ceramic tube, a sealing air layer, an outer layer supporting plate and a rubber or silica gel sealing ring. The heating unit comprises a high-temperature copper plate heating platform; the cooling unit comprises a water cooling head, a cooling water jacket and a cooling water tank, and is nested at the top of the sealed heat insulation unit; according to the temperature acquisition unit, a thermocouple is attached to the surface of a measured object and is connected with an external thermodetector; the data processing unit comprises an acquisition terminal and a computer, the acquisition terminal is connected with a USB interface of the computer and a USB interface of the thermodetector, and data acquired by the thermodetector is transmitted to the computer. The invention provides the heat flux density measuring device which is simple and convenient to assemble, low in construction cost and simple and convenient to calculate, and the measuring efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of heat flux density measurement technology, and in particular to a one-dimensional heat flux density measurement device based on Fourier's law. Background Technology

[0002] Fourier's law states that in heat conduction, the amount of heat conducted through a given cross-section per unit time is proportional to the rate of temperature change perpendicular to that cross-section and the cross-sectional area, while the direction of heat transfer is opposite to the direction of temperature increase. As the core law of heat conduction, Fourier's law is widely used in many fields. In aerospace, new energy, and other fields, Fourier's law provides a basis for analyzing the heat flow path of heat-generating components such as power devices. In the field of metal heat treatment, Fourier's law can be used to predict transient temperature distributions during heating and cooling processes, optimizing process parameters to avoid material damage. In the field of new material development, Fourier's law can be used to measure temperature gradients and heat flux densities to determine the thermal conductivity of materials and evaluate their thermal conductivity performance under extreme temperatures or special environments.

[0003] Heat flux density is a physical quantity that characterizes the intensity of heat transfer per unit area of ​​an object. Heat transfer occurs wherever there is a temperature difference. Currently, the most commonly used instrument for measuring heat flux density is the heat flux meter, with the most widely used types being resistance heat flux meters, radiation heat flux meters, and convection heat flux meters. Traditional heat flux meters suffer from drawbacks such as long response time, low measurement accuracy, and high environmental sensitivity. With technological advancements, many new measurement methods are constantly being developed, such as novel thin-film heat flux meters, high-temperature heat flux meters, and double-sided heat flux meters.

[0004] Without considering radiative heat dissipation (significant only at temperatures above approximately 800℃, negligible around 100℃) and in a still air environment (no external fan considered, wind speed set to zero, convective heat transfer ignored), the heat dissipation capacity of the sample can be simplified to a single thermal conductivity model, satisfying Fourier's law of heat conduction. The one-dimensional heat transfer case is further simplified as follows, where k is the thermal conductivity of the material (W / m / K), and q is the heat flux density or heat transfer rate (W / m³). 2 ):

[0005]

[0006] This invention establishes a one-dimensional unidirectional heat conduction environment and provides a measurement device for evaluating radiator performance. Compared with traditional heat flow meters, this measurement device has advantages such as simple assembly, low construction cost, simple calculation, and easy installation and maintenance. Summary of the Invention

[0007] The purpose of this invention is to provide a one-dimensional heat flux density measuring device based on Fourier's law, so as to achieve simple and cost-effective measurement.

[0008] To achieve the above objectives, the present invention provides a one-dimensional heat flux density measuring device, characterized in that it includes a heating unit, a sealing and insulation unit, a cooling unit, a temperature acquisition unit, and a data processing unit.

[0009] The heating unit includes a high-temperature copper plate heating platform (2), the surface of which is coated with thermally conductive silicone grease, and the heating platform (2) is equipped with a heating temperature controller (1);

[0010] The sealed insulation unit is used to suppress heat exchange between the sample and the external environment. It includes a sealed air layer (13), a ceramic tube (4), insulation material (13), a sealing strip, and an external support shell (3). The hollow ceramic tube (4) is surrounded by insulation material (13), and the insulation material (13) is surrounded by an external support shell (3). The ceramic tube (4) is axially upright on a high-temperature copper plate heating platform (2). A water-cooling head (8) is provided at the upper end of the ceramic tube (4), and the water-cooling head (8) completely covers the ceramic tube (4). There is a gap between the upper end and the insulation material (13), the outer side of the water cooling head (8) and the upper inner side of the outer support shell (3), and the gap is sealed with a sealing strip; the test sample (5) is located inside the ceramic tube (4), the outer diameter of the test sample (5) is smaller than the inner diameter of the ceramic tube (4), and there is a gap between the two called the sealing air layer (13); thermocouples (14) are led out from two different heights on the outside of the test sample (5) to measure the temperature at different points; the lower end of the outer support shell (3) is fixed and sealed with the heating platform (2) by a fixing pad;

[0011] The water-cooling device includes a water-cooling head (8); the water-cooling head (8) is nested on the top of the sealed insulation unit, and the gap between it and the upper end of the outer supporting shell (3) is filled with a flexible sealing strip. The water-cooling head (8) is connected to the water tank (6) through the cooling water pipe (7) to form a cooling circulation structure. The water tank (6) has a built-in water pump, and the water pump outlet is connected to the cooling water pipe (7). The cooling water is circulated by pressurization. The temperature acquisition unit includes a thermocouple (14) and a thermometer. The thermocouple is attached to the surface of the test sample (5) and led out from the top of the device to connect to the thermometer. The thermometer has a USB interface, which can transmit data to a data processing unit with a USB interface. The data processing unit uses a computer, and then the heat flux density through the test sample under the condition can be calculated based on Fourier's law.

[0012] The heating unit is an adjustable constant temperature heater. To improve its surface thermal conductivity and uniformity, it is necessary to coat its surface with thermally conductive silicone grease, which then contacts a plane of the sample to be tested.

[0013] The cooling unit is a water-cooled radiator, including a cooling water tank, a cooling water jacket, and a cooling head, used to reduce the cold end temperature; and in order to improve its surface thermal conductivity and uniformity, thermally conductive silicone grease needs to be coated on the surface of the cooling head, and the thermally conductive silicone grease contacts the upper plane of the test sample (5); the cooling head has a cavity structure.

[0014] The temperature acquisition unit includes a thermometer and a thermocouple, and the thermocouple is made into close contact with both ends of the heat transfer path by thermal conductive adhesive.

[0015] The measured thermal conductivity direction is the length direction of the sample being tested (such as the axial direction of a bar or wire). Its material, cross-sectional shape (such as a circle), and length can be set according to measurement requirements to adjust the measurement sensitivity and range.

[0016] The sealed insulation unit is a detachable insulation cover, which facilitates the replacement of the test sample, the installation of thermocouples, and the cleaning of the internal structure.

[0017] The insulation material (13) is a flexible material such as multi-layered wound glass fiber or asbestos.

[0018] The heating platform is equipped with a temperature rise indicator light, a power indicator light, and a temperature rise switch.

[0019] According to the following formula (1), the heat flux density q is obtained by testing the temperature of the lower heating platform (2) and / or the water cooling effect of the upper water cooling device using the device of the present invention, dT / dx (the rate of temperature change between the two points to be measured); thereby obtaining the heat flux density q. x ;

[0020]

[0021] The one-dimensional heat flux density detection device provided by this invention can perform simple and effective heat flux density measurement by measuring the temperature difference on the surface of an object and utilizing Fourier's law of heat conduction.

[0022] The beneficial effects of this invention are at least as follows:

[0023] (1) This device adopts a multi-layer composite insulation structure. The ceramic tube forms a sealed air layer, which works in synergy with the insulation layer made of flexible materials such as asbestos or glass fiber. This can significantly suppress the radial diffusion of heat and increase the single conduction capability of heat flow along the axial direction. At the same time, the cooling unit reduces the temperature of the cold end of the sample, so that a stable temperature gradient is formed at both ends of the sample, thereby enhancing the thermodynamic driving force and constructing a one-dimensional unidirectional heat conduction environment.

[0024] (2) The experimental apparatus provided by the present invention simplifies the measurement model by constructing a one-dimensional unidirectional heat conduction environment, making it conform to the measurement environment required by Fourier's law, reducing the difficulty of error processing, and reducing the computational difficulty and data processing time.

[0025] (3) The experimental apparatus provided by this invention is relatively simple in assembly and testing procedures while ensuring the reliability of measurement data, which effectively reduces the workload of experiments and lowers the difficulty of operation. At the same time, the construction cost of the apparatus is low. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the testing device in Embodiment 1 of the present invention.

[0027] Figure 2 This is a cross-sectional view of the test sample fixing module (the structure inside the supporting shell and the water cooling head) in Embodiment 1 of the present invention.

[0028] Figure 3 Photograph of the testing device in Embodiment 1 of the present invention.

[0029] Figure 4 The temperature-time change result curve of Example 1 of the present invention.

[0030] Figure 5 The temperature-time change result curve of Example 2 of the present invention.

[0031] Figure 6 The temperature-time change result curve of Comparative Example 1 of this invention.

[0032] Figure 7 The temperature-time change result curve of Comparative Example 2 of this invention.

[0033] Appendix Figure 1 and Figure 2 Numerical markers:

[0034] 1- Heating temperature controller; 2- Heating platform; 3- Support shell (containing the test sample, see cross-section) Figure 2 4-Insulated ceramic tube; 5-Rock sample to be tested; 6-Water cooling device (including a water tank and a circulating water pump); 7-Water pipe (including one inlet pipe and one return pipe); 8-Metal water cooling head; 9-Heating indicator light; 10-Power indicator light; 11-Heating switch; 12-Power switch; 13-Insulation material (asbestos, glass fiber, or aerosol, etc.); 14-Thermocouple (two sets, including two temperature measuring points). Detailed Implementation

[0035] Combined with appendix Figure 1 Appendix Figure 2 Appendix Figure 3 Appendix Figure 4 Appendix Figure 5 Appendix Figure 6 Appendix Figure 7 The present invention will be described in detail with specific embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0036] Example 1

[0037] This embodiment provides a specific structural design for an improved one-dimensional heat flux density measurement platform device, such as... Figure 1 As shown, the heating platform 2 is the heat source of the device, which can accurately control and display the temperature and heat the rod-shaped material 5. The rod-shaped material 5 is a copper rod with a diameter of 20 mm and a length of 100 mm, with a thermal conductivity of k = 389 W / (m·K), which can be substituted into formula (1) for heat flux density calculation. The heating platform temperature controller 1 can display the temperature in real time and adjust it accurately, providing stable heat source conditions for the experiment. The alumina ceramic tube 4 is used as the sample support structure, which has excellent high temperature resistance and low thermal expansion coefficient, ensuring that the sample remains stable at high temperatures. The support shell 3 provides structural support to ensure that the sample is in the correct position. The gap between the alumina ceramic tube 4 and the support shell 3 is filled with asbestos sheets. The asbestos sheets have excellent heat insulation performance and compressibility, and can tightly fit samples of different diameters, reducing the non-uniformity of the heat conduction path. The metal plate water-cooled head 8 is the cold end part of the device, which is tightly fitted with the support shell 3 and the rod-shaped material 5. To ensure a good sealing effect, sealing strips are used around the perimeter to isolate air convection heat transfer. The water-cooling device 6 cools the other end of the rod-shaped material 5 through the water-cooling head 8, ensuring a stable temperature difference between the two ends of the sample, thereby achieving accurate measurement of one-dimensional heat flux density. The alumina ceramic tube 4 has 2mm wide grooves machined on both sides to facilitate the lead-out of the thermocouple wires without affecting the one-dimensional heat conduction path. A cross-sectional view of the interior of the supporting shell is shown below. Figure 2 As shown; actual photos of the device are as follows. Figure 3 As shown.

[0038] The preparation method provided in this embodiment includes the following steps:

[0039] First, turn on the power switch and the heating switch. Once the power indicator and heating indicator lights up, use the heating stage temperature display to precisely control the temperature and raise the heating stage to a fixed, known temperature (e.g., 100℃). After heating to the target temperature, maintain the temperature for 30 minutes until the temperature fluctuation stabilizes within ±0.5℃ / min.

[0040] Next, place the supporting shell and the alumina ceramic tube on the heating stage. The inner diameter of the alumina ceramic tube should be 0.5 mm larger than that of the rod-shaped material. Apply thermal grease to both ends of the copper rod to reduce contact thermal resistance. The thermal conductivity of the thermal grease is 2-3 W / (m·K), which is much higher than that of air (0.024 W / (m·K)), and can significantly improve the heat transfer efficiency between the heating stage and the sample.

[0041] At a fixed distance along the axial length of the copper rod, attach two thermocouples using high-temperature adhesive (such as KAPTON high-temperature tape, temperature resistance ≤400℃). The thermocouple spacing should be 70% of the rod length (70mm for a 100mm rod), and at least 5mm from both ends of the rod to avoid end effects interfering with temperature measurements. The thermocouples must be attached parallel to the rod's axis to ensure that the measured temperature gradient accurately reflects the axial thermal conductivity characteristics.

[0042] Place the copper rod in the middle of the alumina ceramic tube, and then completely attach the metal water-cooling head to the other end of the rod. Seal the area around the rod with a sealing strip to prevent air convection heat transfer. Apply thermal grease to the contact surface between the water-cooling head and the rod to minimize contact thermal resistance. The water-cooling system should maintain a constant flow rate (1-5 L / min) of cooling medium, keeping the cold end temperature within the range of 20-25°C. After turning on the water-cooling system, record experimental data until the system reaches thermal equilibrium.

[0043] The measured temperature change curve over time is as follows: Figure 4 As shown, after substituting the data into Fourier's law, the heat flux density of the sample is obtained as 64418 W / m³. 2 .

[0044] Example 2

[0045] This embodiment provides a specific structural design for an improved one-dimensional heat flux density measurement platform device, such as... Figure 1 As shown, the heating platform 2 is the heat source of the device, which can accurately control and display the temperature and heat the rod-shaped material 5. The rod-shaped material 5 is a 304 stainless steel rod with a diameter of 20 mm and a length of 100 mm, and a thermal conductivity of k = 15 W / (m·K), which can be directly substituted into formula (1) for heat flux density calculation. The heating platform temperature controller 1 can display the temperature in real time and adjust it accurately, providing stable heat source conditions for the experiment. The alumina ceramic tube 4 serves as the sample support structure, which has excellent high temperature resistance and a low coefficient of thermal expansion, ensuring that the sample remains stable at high temperatures. The support shell 3 provides structural support to ensure that the sample is in the correct position. The gap between the alumina ceramic tube 4 and the support shell 3 is filled with asbestos sheets. The asbestos sheets have excellent thermal insulation performance and compressibility, and can tightly fit samples of different diameters, reducing the non-uniformity of the heat conduction path. The metal plate water-cooled head 8 is the cold end part of the device, which is tightly fitted with the support shell 3 and the rod-shaped material 5. To ensure a good sealing effect, sealing strips are used around the perimeter to isolate air convection heat transfer. The water-cooling device 6 cools the other end of the rod-shaped material 5 through the water-cooling head 8, ensuring a stable temperature difference between the two ends of the sample, thereby achieving accurate measurement of one-dimensional heat flux density. The alumina ceramic tube 4 has 2mm wide grooves machined on both sides to facilitate the lead-out of the thermocouple wires without affecting the one-dimensional heat conduction path. A cross-sectional view of the interior of the supporting shell is shown below. Figure 2 As shown.

[0046] The preparation method provided in this embodiment includes the following steps:

[0047] First, turn on the power switch and the heating switch. After the power indicator and heating indicator lights up, use the heating stage temperature display to precisely control the temperature and raise the heating stage to a fixed, known temperature (100℃). After heating to the target temperature, maintain the temperature for 30 minutes until the temperature fluctuation stabilizes within ±0.5℃ / min.

[0048] Next, place the supporting shell and alumina ceramic tube on the heating stage. The inner diameter of the alumina ceramic tube should be 0.5 mm larger than that of the rod-shaped material. Apply thermal grease to both ends of the 304 stainless steel rod to reduce contact thermal resistance. The thermal conductivity of the thermal grease is 2 W / (m·K), which is much higher than that of air (0.024 W / (m·K)), and can significantly improve the heat transfer efficiency between the heating stage and the sample.

[0049] At a fixed distance on a 304 stainless steel rod, attach two thermocouples using high-temperature adhesive (such as KAPTON high-temperature tape, temperature resistance ≤400℃). The thermocouple spacing should be 70% of the rod length (for a 100mm long rod, the thermocouple spacing dx is 70mm), and at least 5mm from both ends of the rod to avoid end effects interfering with temperature measurement. The thermocouples must be attached parallel to the rod's axis to ensure that the measured temperature gradient accurately reflects the axial thermal conductivity characteristics.

[0050] Place a 304 stainless steel rod in the middle of the alumina ceramic tube, and then completely attach the metal water-cooling head to the other end of the rod. Seal the area around the rod with a sealing strip to prevent air convection heat transfer. Apply thermal grease to the contact surface between the water-cooling head and the rod to minimize contact thermal resistance. The water-cooling system should maintain a constant flow rate (1-5 L / min) of cooling medium, keeping the cold end temperature within the range of 20-25°C. After turning on the water-cooling system, record experimental data until the system reaches thermal equilibrium.

[0051] The measured temperature change curve over time is as follows: Figure 5 As shown, after processing the data using Fourier's law, the heat flux density of the sample is obtained as 10170 W / m³. 2 .

[0052] Comparative Example 1

[0053] Without applying thermal grease to the contact surfaces of the 20mm diameter, 100mm length copper rod with the heating platform and the water-cooling head, the sample temperature rose slowly during the experiment and never reached a steady state. The final steady-state temperature was 12-15℃ lower than that of Example 1. Analysis revealed that this phenomenon stemmed from the presence of a tiny gap between the heating platform and the sample. The thermal conductivity of air (0.024 W / (m·K)) is much lower than that of metals or ceramics, resulting in low heat transfer efficiency. When thermal grease (thermal conductivity 2-3 W / (m·K)) was applied to the contact surfaces, the temperature of the rod material increased significantly and reached a steady state within the same timeframe. This indicates that the thermal grease reduces contact thermal resistance by filling the microscopic gaps, thereby accelerating heat transfer and improving measurement accuracy.

[0054] The measured temperature change curve over time is as follows: Figure 6 As shown, the thermocouple spacing dx is 70mm. The curve indicates that this condition presents problems such as slow heating rate and excessive temperature difference between the hot end and the heating platform. After processing the data using Fourier's law, the heat flux density measured in this study is 13885W / m³. 2 .

[0055] Comparative Example 2

[0056] A copper rod sample with a diameter of 20 mm and a length of 100 mm was directly wrapped with asbestos. Figure 5 As shown in the figure. The results show that although there is direct heat conduction between the rod and the asbestos, the softness of the asbestos prevents the water-cooled head from fitting tightly against the sample, resulting in airflow in the contact gap. The convective heat transfer caused by the airflow violates the theoretical assumption of one-dimensional unidirectional heat transfer, and the cooling efficiency at the cold end is insufficient, so the cooling effect of the water-cooling device is not fully realized. Further observation revealed that although the compressibility of asbestos can adapt to changes in the sample diameter, it was not used in conjunction with a sealing strip when used as insulation material, causing the system boundary condition control to fail. In contrast, this embodiment fills the gap between the alumina ceramic tube and the supporting shell with asbestos sheets, and combines this with a sealing strip to seal the contact surface between the water-cooled head and the sample, effectively isolating air convection and ensuring the uniqueness of the heat conduction path and the cooling efficiency at the cold end. Experimental data show that this design stabilizes the temperature difference between the two ends of the sample within the set range, and the repeatability error of the heat flux density measurement results is less than ±2%, verifying the reliability of the device in constructing a one-dimensional steady-state heat transfer environment.

[0057] The measured temperature change curve over time is as follows: Figure 7 As shown, the thermocouple spacing dx is 70mm. The curve indicates that the water-cooling head is not effectively cooling the system in this case. After processing the data using Fourier's law, the measured heat flux density is 299544 W / m³. 2 .

[0058] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A one-dimensional heat flux density measuring device based on Fourier's law, characterized in that, It includes a heating unit, a sealing and insulation unit, a cooling unit, a temperature acquisition unit, and a data processing unit; The heating unit includes a high-temperature copper plate heating platform (2), the surface of which is coated with thermally conductive silicone grease, and the heating platform (2) is equipped with a heating temperature controller (1); The sealed insulation unit is used to suppress heat exchange between the sample and the external environment. It includes a sealed air layer (13), a ceramic tube (4), insulation material (13), a sealing strip, and an external support shell (3). The hollow ceramic tube (4) is surrounded by insulation material (13), and the insulation material (13) is surrounded by an external support shell (3). The ceramic tube (4) is axially upright on a high-temperature copper plate heating platform (2). A water-cooling head (8) is provided at the upper end of the ceramic tube (4), and the water-cooling head (8) completely covers the ceramic tube (4). There is a gap between the upper end and the insulation material (13), the outer side of the water cooling head (8) and the upper inner side of the outer support shell (3), and the gap is sealed with a sealing strip; the test sample (5) is located inside the ceramic tube (4), the outer diameter of the test sample (5) is smaller than the inner diameter of the ceramic tube (4), and there is a gap between the two called the sealing air layer (13); thermocouples (14) are led out from two different heights on the outside of the test sample (5) to measure the temperature at different points; the lower end of the outer support shell (3) is fixed and sealed with the heating platform (2) by a fixing pad; The water-cooling device includes a water-cooling head (8); the water-cooling head (8) is nested on the top of the sealed insulation unit, and the gap between it and the upper end of the outer supporting shell (3) is filled with a flexible sealing strip. The water-cooling head (8) is connected to the water tank (6) through the cooling water pipe (7) to form a cooling circulation structure. The water tank (6) has a built-in water pump, and the water pump outlet is connected to the cooling water pipe (7). The cooling water is circulated by pressurization. The temperature acquisition unit includes a thermocouple (14) and a thermometer. The thermocouple is attached to the surface of the test sample (5) and led out from the top of the device to connect to the thermometer. The thermometer has a USB interface, which can transmit data to a data processing unit with a USB interface. The data processing unit uses a computer, and then the heat flux density through the test sample under the condition can be calculated based on Fourier's law.

2. The one-dimensional heat flux density measuring device based on Fourier's law according to claim 1, characterized in that, The heating unit is an adjustable constant temperature heater. To improve its surface thermal conductivity and uniformity, it is necessary to coat its surface with thermally conductive silicone grease, which then contacts a plane of the sample to be tested.

3. A one-dimensional heat flux density measuring device based on Fourier's law according to claim 1, characterized in that, The cooling unit is a water-cooled radiator, including a cooling water tank, a cooling water jacket, and a cooling head, used to reduce the cold end temperature; and in order to improve its surface thermal conductivity and uniformity, thermally conductive silicone grease needs to be coated on the surface of the cooling head, and the thermally conductive silicone grease contacts the upper plane of the test sample (5); the cooling head has a cavity structure.

4. A one-dimensional heat flux density measuring device based on Fourier's law according to claim 1, characterized in that, The temperature acquisition unit includes a thermometer and a thermocouple, and the thermocouple is made into close contact with both ends of the heat transfer path by thermal conductive adhesive.

5. A one-dimensional heat flux density measuring device based on Fourier's law according to claim 1, characterized in that, The measured thermal conductivity direction is the length direction of the sample being tested (such as the axial direction of a bar or wire). Its material, cross-sectional shape (such as a circle), and length can be set according to measurement requirements to adjust the measurement sensitivity and range.

6. A one-dimensional heat flux density measuring device based on Fourier's law according to claim 1, characterized in that, The sealed insulation unit is a detachable insulation cover, which facilitates the replacement of the test sample, the installation of thermocouples, and the cleaning of the internal structure.

7. A one-dimensional heat flux density measuring device based on Fourier's law according to claim 1, characterized in that, The heating platform is equipped with a temperature rise indicator light, a power indicator light, and a temperature rise switch.

8. A one-dimensional heat flux density measuring device based on Fourier's law according to claim 1, characterized in that, The insulation material (13) is a flexible material such as multi-layered wound glass fiber or asbestos.

9. A one-dimensional heat flux density measuring device based on Fourier's law according to claim 1, characterized in that, According to the following formula (1), the heat flux density q is obtained by testing the temperature of the lower heating platform (2) and / or the water cooling effect of the upper water cooling device using the device of the present invention, dT / dx (the rate of temperature change between the two points to be measured); thereby obtaining the heat flux density q. x ;

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