Radiation-cooled thin-film power measurement device and method

Abstract

This invention relates to the field of radiation cooling technology and discloses a radiation cooling film power measurement device, including a testing cabinet. A limit frame is movably connected to the left side of the connecting seat, and a radiation film working box is provided on the top of the cold source tank. This radiation cooling film power measurement device and method transfers heat to liquid nitrogen in a Dewar flask through the heat of the radiation film layer itself and the heating effect of the heating disc. Liquid nitrogen simulates a low-temperature environment, creating a temperature difference that causes energy radiation. A black aluminum sheet simulates the radiation absorption effect in space. The radiation film layer and the heating disc are fixed on a fixture plate, and the chamber is evacuated to a vacuum. The radiation window is used to equivalently replace the atmosphere under clear conditions, facilitating rapid data processing and calculation of the cooling power of the radiation film. This method avoids the influence of outdoor weather, wind speed, and other factors in traditional measurement methods, thereby further improving the versatility of the experimental environment and the accuracy and reference value of the experimental data.

Description

Technical Field

[0001] This invention relates to the field of radiation cooling technology, specifically to a radiation cooling thin film power measuring device and method. Background Technology

[0002] With the rapid growth of the world economy and the rapid increase in the global population, the high energy consumption has led to a large amount of greenhouse gas emissions, resulting in rising global temperatures, abnormal climate, and serious threats to the survival of organisms. To address this, the country is vigorously developing new energy sources and promoting the consumption substitution and transformation and upgrading of traditional chemical materials such as coal. New pollution-free renewable energy sources have gradually become one of the important research directions. Compared with traditional cooling methods, sky radiation cooling is an energy-free, pollution-free, and autonomous cooling method. The principle of this technology is to reflect sunlight through the "atmospheric window" (8-13 micrometer wavelength band) and radiate heat directly to outer space, thereby achieving a passive and efficient cooling. Therefore, the research on the cooling power of cooling radiation films is gradually becoming one of the important directions.

[0003] Current research on the power of radiation cooling films is conducted under good lighting conditions, which is limited by outdoor weather and greatly affected by environmental factors, thus failing to improve the practicality of the device. At the same time, there are many cooling radiation film products on the market, and it is difficult to compare their advantages and disadvantages through experimental data. Therefore, in order to solve the problem that it is inconvenient to compare the selection of radiation films and the advantages and disadvantages of cooling power of different existing cooling radiation films through a more complete experimental system, a radiation cooling film power measurement device and measurement method are proposed. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] To address the shortcomings of existing technologies, this invention provides a radiation cooling film power measurement device and method. It has the advantages of being unrestricted by the environment and providing effective data support for evaluating radiation film selection and film cooling power through the establishment of a relatively complete evaluation and measurement experiment. This solves the problems in the prior art where the research and comparison of cooling power of some existing cooling radiation films is limited by environmental influences and it is difficult to form a relatively complete experimental evaluation system.

[0006] (II) Technical Solution

[0007] To achieve the above-mentioned goal of providing effective data support for the selection of radiation films and the evaluation of film cooling power by establishing a relatively complete evaluation and measurement experiment without being restricted by the environment, the present invention provides the following technical solution: a radiation cooling film power measurement device, including a detection cabinet, wherein the detection cabinet is equipped with measurement components;

[0008] The measuring assembly includes a lifting platform fixed to the right wall inside the testing cabinet. A threaded screw is rotatably connected to the inner side of the lifting platform, and a lifting seat is threaded to the outer side of the threaded screw. A connecting seat is fixedly connected to the left side of the lifting seat, and a limit frame is movably connected to the left side of the connecting seat. A cold source tank is placed inside the testing cabinet, and a radiation film working box is installed on the top of the cold source tank.

[0009] Preferably, a rotary disk is rotatably connected to the top of the lifting platform, and there are two threaded screws. The tops of the two threaded screws are coaxially fixed with sprockets, and the two sprockets are connected by a chain drive. The bottom of the rotary disk is coaxially fixed with one of the sprockets.

[0010] Preferably, the connecting seat has an internal angle adjustment structure, which includes a worm gear rotatably connected to the inside of the connecting seat. A turntable is rotatably connected to the inner left wall of the connecting seat. A worm gear shaft is coaxially fixed to the right side of the turntable, and the turntable extends through to the left side of the connecting seat. The worm gear meshes with the outer side of the worm gear shaft. The limiting frame includes a frame plate fixedly connected to the left side of the turntable, and two adjusting screws are rotatably connected inside the frame plate.

[0011] Preferably, each of the two adjusting screws has two symmetrically arranged threaded rings on its outer surface. Each of the two threaded rings is threadedly connected to a first clamping arm. A sponge pad is fixedly connected to the opposite side of each of the two first clamping arms. The outer side of each of the two sponge pads is covered with a threaded rubber layer. The outer surface of the other two threaded rings is threadedly connected to a second clamping arm. An arc-shaped clamping ring is fixedly connected to the opposite side of each of the two second clamping arms. A spring assembly is fixedly connected to the inner side of each of the two clamping rings.

[0012] Preferably, the cold source tank includes a vacuum tank body placed inside the two second clamping arms. A sealing cover plate is hinged to the top of the vacuum tank body. Anodized black aluminum sheets are fixedly connected to both the inner side of the sealing cover plate and the inner bottom wall of the vacuum tank body. A sealing ring is fixedly connected to the inner side of the sealing cover plate. A connecting pipe with a valve is fixedly connected to the left side of the vacuum tank body.

[0013] Preferably, a first vacuum tube is fixedly connected to both the right and back sides of the vacuum tank. A Dewar flask is placed on top of one of the black aluminum sheets. The Dewar flask is filled with liquid nitrogen. A vacuum pump is connected to the inside of the vacuum tank through the first vacuum tube to form a vacuum chamber structure. The radiation film working box includes a measuring box placed on top of a sealing cover plate. A boss is fixedly connected to the inner bottom wall of the measuring box. A clamping plate is fitted on the top of the boss.

[0014] Preferably, a hollow slot is provided at the center of the inner side of the clamp plate, and an alumina ceramic heating disc is fixedly engaged on the inner side of the hollow slot. A radiation thin film layer is attached to the top of the heating disc. A first mounting hole is provided on the inner left wall of the measuring box. A second vacuum tube is fixedly installed inside the first mounting hole, and a vacuum pressure gauge is fixedly installed outside the second vacuum tube. A second mounting hole is provided on the inner right wall of the measuring box.

[0015] Preferably, the inner top wall of the measuring box has a circular radiation window, which is a zinc selenide structure layer and is located directly above the heating disc. A first thermocouple is fixedly installed on the inner top wall of the measuring box on the side close to the radiation window, and a second thermocouple is fixedly installed on the side away from the radiation window. The heating disc, the first thermocouple, and the second thermocouple are all connected to external cables through the second mounting hole.

[0016] A method for measuring the power of a radiation-cooled thin film includes the following steps:

[0017] S1. Pre-preparation operation: Operate the PLC system, first pre-cool the Dewar bottle by introducing a small amount of liquid nitrogen, then continuously introduce sufficient liquid nitrogen and seal it, prepare a radiation thin film layer of appropriate size according to the size of the heating disc, and seal the radiation thin film layer on the top of the heating disc by uniformly applying thermal grease.

[0018] Next, place the temperature probe of the first thermocouple in the center of the radiation thin film layer, and place the temperature probe of the second thermocouple on the side away from the radiation thin film layer. Connect a vacuum pump to the second vacuum tube, and after the vacuum pump is stable, evacuate the second vacuum tube and the measuring box.

[0019] S2. Assembly Operation: Place the Dewar bottle steadily onto the black aluminum sheet on the bottom wall of the vacuum tank. After sealing with the sealing cover, use the external vacuum pump connected to the first vacuum tube to draw a vacuum. Then, fix the measuring box inside the transparent frame with the radiation window facing down. At this time, the radiation film layer is directly opposite the center of the sealing cover and the frame is placed on the top of the vacuum tank. Connect all the cables leading out of the second mounting hole to the PLC control system.

[0020] Then, rotate the two adjusting screws respectively to clamp and fix the measuring box body by the first clamping arm and the vacuum tank body by the second clamping arm. Adjust the measuring box body and the vacuum tank body to the appropriate height and angle by rotating the screw and worm.

[0021] S3. Experimental Operation: The test cabinet is equipped with a power module and a touch screen. First, turn on the power module and set the voltage and current values ​​to 1.0V and 0.5A respectively. Then, turn on the ambient switch on the touch screen and then turn on the main switch.

[0022] The heat from the radiant film layer is radiated into the liquid nitrogen in the Dewar flask through the radiant window and the black aluminum sheet. Data on the ambient temperature and the temperature of the radiant film are collected using a first and second thermocouple. At this point, the heating temperature is set, with a constant power of 100-200 W / m. 2 The heating disc within the range reheats the radiation thin film layer to the same temperature as the ambient temperature, and the heating time of the heating disc is recorded;

[0023] S4. Data processing: After one minute, read the voltage data V, current data A, high-level data t1, and total cycle data T during heating. Then calculate the value of (VAt1) / (radiation film area × T). If the value is around 110, continue the experiment. If the value is too large or too small, stop the experiment and check whether there are any irregularities in the previous steps.

[0024] The experiment takes about 30 minutes. After the experiment is completed, the experimental data displayed on the touch screen is extracted and plotted. Then, the cooling power of the tested radiation film is calculated by converting the heating efficiency of the heating disc.

[0025] (III) Beneficial Effects

[0026] Compared with the prior art, the present invention provides a radiation-cooled thin film power measurement device and measurement method, which has the following beneficial effects:

[0027] 1. The radiation cooling film power measurement device and method transfer heat to liquid nitrogen in a Dewar flask through the heat of the radiation film layer itself and the heating effect of the heating disc. The liquid nitrogen simulates a low-temperature environment to generate a temperature difference that causes energy radiation. A black aluminum sheet simulates the radiation absorption effect in space. The radiation film layer and the heating disc are fixed on a fixture plate. The chamber is evacuated to a vacuum. The radiation window is used to replace the atmosphere in a clear day. The heating disc is controlled by a PLC control system to control the heating and data acquisition. The data can be processed quickly and the cooling power of the radiation film can be calculated.

[0028] 2. The radiation cooling film power measurement device and method use liquid nitrogen to simulate heat conduction and generate radiation effect, and use black aluminum sheet to simulate the radiation absorption effect in space and the vacuum experimental environment. This can avoid the influence of outdoor weather, wind speed and other factors in traditional measurement methods, thereby further improving the versatility of the experimental environment and the accuracy and reference of the experimental data. Attached Figure Description

[0029] Figure 1 This is a left view of the structure of the testing cabinet of the present invention;

[0030] Figure 2 This is a right view of the structure of the testing cabinet of the present invention;

[0031] Figure 3 This is a cross-sectional view of the testing cabinet structure of the present invention;

[0032] Figure 4 This is a schematic diagram of the cold source tank structure of the present invention;

[0033] Figure 5 for Figure 4 Front view;

[0034] Figure 6 This is a schematic diagram of the connector structure of the present invention;

[0035] Figure 7 for Figure 6 A top-down view from a specific perspective;

[0036] Figure 8 This is a schematic diagram of the limiting frame structure of the present invention;

[0037] Figure 9 This is a schematic diagram of the measuring box structure of the present invention;

[0038] Figure 10 This is a schematic diagram of the radiation window structure of the present invention;

[0039] Figure 11 This is a theoretical design drawing of the vacuum tank of the present invention;

[0040] Figure 12 This is a flowchart of the temperature control logic of the present invention;

[0041] Figure 13 This is a graph showing experimental data for error verification of the device of the present invention;

[0042] Figure 14 This is a graph showing experimental data from the liquid nitrogen feasibility verification of the device of the present invention;

[0043] Figure 15 This is a graph showing the experimental data for the feasibility study of the device under liquid nitrogen conditions in this invention.

[0044] Figure 16 This is a graph showing the experimental data of the absorption rate of black aluminum anodized by the present invention after low-temperature treatment;

[0045] Figure 17 This is a graph showing experimental data for verifying the black aluminum radiation absorption performance of the device of the present invention.

[0046] Figure 18 This is a graph showing experimental data on the radiation transmittance of the ZnSe window of this invention.

[0047] Figure 19 This is a comparative experimental data graph showing the zinc selenide window sheet and acrylic sheet of the present invention;

[0048] Figure 20 The figure shows experimental data for verifying the method of reducing heat convection in this invention.

[0049] Figure 21 This is a diagram showing the experimental data of the radiation path simulation of the radiation film of the present invention;

[0050] Figure 22 This is a diagram showing the temperature distribution simulation experiment data of the radiation film working chamber of this invention;

[0051] Figure 23 This is a simulation experiment data diagram of the temperature distribution of the fixture of the present invention.

[0052] In the diagram: 1. Testing cabinet; 2. Measuring components; 201. Lifting platform; 202. Lead screw; 203. Lifting seat; 204. Connecting seat; 205. Limiting frame; 2051. Frame plate; 2052. Adjusting screw; 2053. First clamping arm; 2054. Second clamping arm; 2055. Clamping ring; 206. Cold source tank; 2061. Vacuum tank; 2062. Sealing cover; 2063. Connecting pipe; 2064. First vacuum tube; 2065. Dewar flask; 207. Radiation film working box; 2071. Measuring... 1. Measuring box; 2072. Fixture plate; 2073. Heating disc; 2074. Radiation film layer; 2075. Second vacuum tube; 2076. Radiation window; 2077. First thermocouple; 2078. Second thermocouple; 3. Rotating disc; 4. Chain gear; 5. Angle adjustment structure; 501. Worm gear; 502. Turntable base; 503. Worm gear shaft; 6. Threaded ring layer; 7. Sponge pad; 8. Spring assembly; 9. First mounting hole; 10. Vacuum pressure gauge; 11. Second mounting hole; 12. Power module; 13. Touch screen. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] Example 1:

[0055] For the height design of the vacuum tank 2061, assuming the highest indoor ambient temperature is 313K, the thermal conductivity K of liquid nitrogen at this temperature is 0.025W / Km. Furthermore, existing experiments show that at an operating temperature of 40℃, the heat flux density q from heat conduction and convection is approximately 50W / m². 2 The height of vacuum tank 2061 can be calculated using the following formula: d=kΔT / q, which shows that the height of vacuum tank 2061 should be at least 118mm.

[0056] With the thickness of the radiation window 2076 set to 12 mm, the effective radiation angle of the radiation film layer 2074 is concentrated in the range of 0-30°. Therefore, the minimum width of the liquid nitrogen storage device is 190 mm. Based on the possible errors in the above calculations, the opening width of the liquid nitrogen container is finally set to 250 mm and the depth to 300 mm, as shown in the attached figure.

[0057] Example 2: Feasibility Verification

[0058] (I) Verification of Device Errors

[0059] To verify the effectiveness of this device in measuring the cooling power of the radiative film, the team compared the device's measurements with MATLAB simulations and calculated the errors between the two methods. In the attached figure, the radiative cooling power is set at an ambient temperature of 27°C using standard indoor measuring equipment. Due to data accumulation lag on the Weintek touchscreen, after exporting the data, MATLAB was used to compare the ambient temperature and the film temperature, and cooling power compensation was applied. The compensated power is approximately 128 W / m. 2 Furthermore, the power difference before and after the experimental compensation was 20W / m. 2 The left and right figures prove the rationality of the experiment.

[0060] The attached figure shows the results of a MATLAB simulation, with a calculated value of 140 W / m. 2 Then, the relative error is calculated as (140-128) / 140*100%≈8.5%.

[0061] Comparison of actual experimental data revealed that the actual measurement results were not significantly different from the MATLAB simulation results. Therefore, this measuring device can accurately measure the cooling power of the radiation film.

[0062] (II) Feasibility verification of using liquid nitrogen

[0063] When the radiative thin film layer 2074 operates outdoors, since the cold source is space (3K), liquid nitrogen is used to create the low-temperature environment, while a Dewar flask is used as the cold source (77K). Calculations show that the radiative power of the cold source at 77K is only 0.0303W / m². 2 With 100W / m 2 The net power is negligible compared to the cold source, so using a liquid nitrogen container as a cold source to verify the radiation cooling performance in the laboratory can be considered an ideal solution. Then, a preliminary control experiment was conducted. One control group had liquid nitrogen added to the liquid nitrogen container to provide a low temperature environment, while the other experimental group was in a room temperature environment without liquid nitrogen.

[0064] Since the power difference before and after the experiment was 20W / m 2The results, as shown in the attached figures, demonstrate that both control experiments are reasonable. Compared to the control group with added liquid nitrogen, the experimental group without liquid nitrogen lacks a significant temperature difference. Consequently, heat cannot radiate away due to the temperature difference, resulting in heat remaining primarily inside the measuring chamber 2071 and on the surface of the radiation film layer 2074. This causes the temperature of the measuring chamber 2071 and the radiation film layer 2074 in the experimental group without liquid nitrogen to continuously rise, with the measured cooling power only reaching 25 W / m. 2 Around, with the actual power of the membrane at 110W / m 2 The difference is huge, making the experimental data unreasonable;

[0065] Therefore, to further verify its feasibility, the cooling power of the same cooling radiation membrane was tested using both outer space as the cold source and a liquid nitrogen container as the cold source. According to the experimental results in the attached figure, the cooling power measured using a liquid nitrogen container as the cold source and outer space as the cold source is approximately equal, thus further confirming the rationality of using a liquid nitrogen container as the cold source.

[0066] (III) Verification of radiation absorption performance of black aluminum

[0067] Black aluminum sheets were installed inside the vacuum tank 2061 to absorb the thermal radiation generated by the radiative cooling film. To verify its absorption characteristics, the absorption rate of black aluminum sheets with different processing methods was tested. According to the experimental results in the attached figure, the absorption rate of black aluminum sheets processed by anodizing is over 95%. To verify that black aluminum still has a suitable absorption rate in extremely low temperature environments, the absorption rate of black aluminum after low temperature treatment was also measured. After 12 hours, the infrared absorption rate of black aluminum was still over 80%.

[0068] To verify the role of black aluminum in this verification experiment, an experimental group without black aluminum was set up. According to the experimental results in the attached figure, the measured cooling power without black aluminum is not stable, and its curve is a monotonically increasing arc. In contrast, the control group with black aluminum is a straight line parallel to the time axis and fluctuates slightly at a certain specific value. This is because without the absorption of radiation by black aluminum, the heat emitted by the radiation film layer 2074 cannot be fully absorbed, which reduces the temperature difference. As a result, some heat cannot be radiated out within the specified time and remains on the surface of the radiation film, thus making it impossible to obtain accurate measurement results.

[0069] (iv) Verification of the radiation transmittance of ZnSe window

[0070] To simulate the atmospheric environment under clear weather conditions, ZnSe material was used for the radiation window 2076 and radiation transmittance experiments were conducted. The experimental results of the infrared transmission spectrum are shown in the attached figure. It can be seen that the transmittance is good in the 8-13μm band, reaching more than 95%, which can achieve the effect of simulating the atmospheric environment under clear weather conditions. This can effectively transmit the heat radiated by the cooling film through the window into the Dewar flask 2065, preventing the problem of the film temperature rising due to the inability to pass through the window and affecting the experimental results.

[0071] To further verify the influence of the material selection for the 2076 radiation window on the experimental results, ZnSe and ordinary acrylic sheets were used as the control and experimental groups, respectively. According to the experimental results shown in the attached figure, due to sensitivity issues causing high-level loss, compensation was required. The power difference before and after compensation in both control and experimental groups was 20 W / m². 2 The results, approximately 50W / m², demonstrate the validity of both sets of experiments. A comparison with the control group shows that the power output using acrylic sheets is less than 50W / m². 2 The power output using ZnSe reached 120W / m. 2 ;

[0072] The cooling power obtained by this experimental group differed greatly from the actual power. This is because the transmittance of ordinary acrylic sheets is much lower than that of ZnSe material windows. As a result, only a portion of the heat dissipated by the cooling film can pass through the window, while the heat that does not pass through the window is reflected back onto the cooling film, causing an unnecessary increase in the film's temperature. Since the cooling power is reflected by the rate at which the film's temperature decreases over a certain period of time, the final measured temperature of the film becomes higher, resulting in a very small measured power. This demonstrates that the high transmittance window of ZnSe material can ensure the accuracy of the experimental measurement results.

[0073] (V) Verification of methods to reduce heat convection

[0074] Thermal convection is the main cause of inaccurate indoor cooling film power measurements. To verify the impact of thermal convection on experimental data, a control group under vacuum conditions and an experimental group under non-vacuum conditions were set up. According to the experimental results in the attached figure, the power difference before and after compensation in both groups was 20 W / m. 2 The left and right figures demonstrate the rationality of the two control experiments.

[0075] By comparing the data obtained from the experimental group and the control group, it can be seen that the measured power continued to decrease after the start of the experiment, and gradually stabilized after about 1.5 hours. This is because the movement of thermal convection interfered with the normal radiation of the radiant film to the cold source. Due to the chaotic flow of thermal convection in the air, some heat was blocked on the radiant film for a long time by the relative movement of thermal convection and could not be dissipated, which slowed down the temperature drop of the radiant film and thus affected the accuracy of the cooling power measurement data.

[0076] Example 3: Device Simulation Verification

[0077] (I) Simulation of Radiation Path of Radiation Film

[0078] The radiation path and return rate of the radiation film were simulated using the software TracePro. The ambient temperature was set to 298K, and the temperature of the black aluminum sheet was set to 77K. At this temperature, the absorption rate in the 8-13μm wavelength band was 90%. Then, a Lambertian emission field model was selected, and a surface light source with a wavelength of 8-13μm and a wavenumber of 5000 was added. The illuminance of the light source was set to 298W / m². 2 As shown in the attached figure, the heat radiated by the radiative thin film layer 2074 is almost completely absorbed, and only 0.003% of the heat is reflected back, which further proves the feasibility of simulating the radiation path of the radiative film.

[0079] (II) Simulation of Temperature Distribution in Radiation Film Working Chamber

[0080] To verify the heat insulation effect of the vacuum environment and the fixture plate 2072, the heat transfer in the vacuum environment and the specific heat conduction of the fixture plate 2072 were analyzed and verified using ANSYS simulation software. In addition, a control experiment was set up with and without vacuum to further verify the influence of the vacuum environment on the power measurement of the cooling film.

[0081] Assuming the radiative cooling power of the radiative cooling film is 80 W / m 2 The ambient temperature was 30℃. The heat transfer results under vacuum and non-vacuum conditions inside the tank were compared as shown in the figure. Under non-vacuum conditions, the temperature of the radiative cooling film decreased by 5℃, while under vacuum conditions, the temperature of the radiative cooling film decreased by 9℃. This reflects the importance of creating a vacuum environment and the feasibility of vacuuming the measurement chamber 2071.

[0082] Control experiments were conducted with vacuum conditions as the control variable, while keeping all other conditions the same. According to the experimental results in the attached figure, data were obtained for both the non-vacuum and vacuum experiments. In the non-vacuum environment, the temperature of the radiative cooling film decreased by 0.5℃, while in the vacuum environment, the temperature decreased by 1℃. Furthermore, the net cooling power was better under vacuum conditions than under non-vacuum conditions, thus demonstrating the influence of creating a vacuum environment on the measurement of cooling film power.

[0083] (III) Simulation of Fixture Temperature Distribution

[0084] The thermal conductivity of the fixture plate 2072 was simulated and verified. The fixture plate 2072 and the heating disc 2073 were assembled and fixed. The initial temperature was set to 20℃, and the temperature on the six faces of the heating disc 2073 was linearly increased from 20℃ to 30℃. The thermal conductivity of the fixture plate 2072 and the heating disc 2073 were 29.3 W / Km and 0.022 W / Km, respectively. According to the heat flux vector data obtained from the heat conduction shown in the attached figure, the average heat flux density of the heating disc 2073 is approximately 1×10⁻⁶. -13 W / Km, the highest heat flux density of clamp plate 2072 is 1.32×10 -14 W / Km, therefore the proportion of heat lost through heat conduction is extremely small and can be ignored.

[0085] Based on the analysis of the simulation model and the data from the comparative experimental results, it can be seen that the combined use of vacuuming and thermal insulation clamps can greatly reduce the impact of heat convection on the measurement of the cooling power of the radiation film, thereby ensuring the reliability of the experimental data.

[0086] Example 4:

[0087] (a) Using liquid nitrogen and black aluminum as cold sources to create a large temperature difference indoors.

[0088] Because the temperature in outer space is 3K, there is a significant temperature difference compared to the Earth's surface, allowing surface radiation to be emitted into space. Liquid nitrogen at 77K was chosen to create this large temperature difference indoors, and a Dewar flask with very low thermal conductivity (2065) was used to hold the liquid nitrogen. Calculations show that the radiative power of 77K liquid nitrogen is 8.7183 * 10⁻⁶. -4 W / m 2 The difference is negligible, and the effect of outer space and liquid nitrogen absorbing radiation was verified by measuring the cooling power under the two conditions. The results showed that the difference was not significant, thus proving the feasibility of using liquid nitrogen and black aluminum as cold sources to create a large temperature difference indoors.

[0089] Meanwhile, because the temperature in outer space is low, less heat is radiated to the Earth's surface through the atmosphere. This device uses anodized black aluminum to cover the bottom and mouth of the Dewar flask. The black aluminum sheet at the bottom of the flask serves as part of the cold source, while the black aluminum disc at the mouth of the flask is used to minimize the radiation reflected back to the window. Simulation calculations show that black aluminum can almost completely absorb radiation.

[0090] Simulation calculations showed that a container with an inner diameter of 250mm and a height of 300mm was required to allow all the radiation from the membrane to enter the cold source. Therefore, a Dewar 2065 flask with an inner diameter of 143mm and an inner height of 300mm was selected. A black aluminum sheet with an outer diameter of 265mm, an inner diameter of 143mm, and a thickness of 20mm was placed on the container. Simulations verified the feasibility of the Dewar 2065 flask and the black aluminum sheet dimensions. Measurements showed that the radiation power of the same membrane measured under conditions where liquid nitrogen and black aluminum were used as the cold source was almost the same as that measured under conditions where space was used as the cold source, which can effectively simulate the space environment.

[0091] (ii) Using ZnSe windows to replace PE films with high transmittance in the 8-13μm wavelength band.

[0092] Because the radiation in the 8-13 micrometer band has high and stable transmittance in the atmosphere, but outdoor measurements are easily affected by the weather, and because the radiation film working chamber 207 needs to be evacuated to a vacuum, the chamber cover structure needs to be strong enough to withstand one atmosphere of pressure. Therefore, instead of the PE film which cannot withstand pressure, a ZnSe window with a transmittance of over 90% in the 8-13 micrometer band was selected. After simulation, the window showed extremely high radiation transmittance and achieved excellent results in the experiment.

[0093] In summary, the working principle of the radiation cooling film power measurement device and measurement method is as follows: the device is designed based on the "temperature feedback principle". The radiation film layer 2074 continuously transfers its own heat to the bottom cold source tank 206 through mid-infrared radiation, causing its own temperature to drop. The heating disc 2073 heats the film by heat conduction, continuously maintaining the film temperature at the same level as the ambient temperature.

[0094] Then, the air inside the vacuum chamber is extracted by a vacuum pump to ensure that the internal pressure is less than 0.1 Pa. The radiation film layer 2074 and the radiation window 2076 are then facing the cold source. The radiation window 2076, which has high transmittance in the mid-infrared band and is made of zinc selenide, reaches the bottom cold source tank 206. Then, the film temperature and ambient temperature inside the vacuum chamber are measured in real time by the first thermocouple 2077 and the second thermocouple 2078 of type K. The "temperature feedback" principle is adopted. The opening / closing of the solid-state relay is controlled by the PLC, which indirectly controls the opening / closing of the main power supply, thereby achieving the working / non-working state of the heating disc 2073. This ensures that the entire heat exchange process inside the measuring chamber 2071 remains balanced throughout the entire experiment.

[0095] By extracting data from the touchscreen 13, the programmable logic controller (PLC) is used as a logic operation and control system. The PLC controls intermediate components (such as DC voltage relay switches) to control the start and stop of the heating disc 2073. After starting work, the PLC compares the ambient temperature (Ta) measured by two thermocouples with the film temperature (Tf). If Ta > Tf, the PLC controls the heating disc 2073 to heat the film at a constant power until Tf = Ta. The PLC automatically collects the ratio of the start / stop time of the heating disc 2073 to the heating power of the heating disc 2073, and calculates the actual heating power of the heating disc 2073 during the heating period, i.e., the cooling power of the radiative cooling film, according to the formula P(cooling) = P(heating disc) * high level / (total cycle * film area).

[0096] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0097] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A power measurement device for a radiative cooling thin film, comprising a detection cabinet (1), characterized in that: The testing cabinet (1) is equipped with a measuring component (2); The measuring component (2) includes a lifting platform (201) fixed to the right wall inside the testing cabinet (1). A threaded screw (202) is rotatably connected to the inner side of the lifting platform (201). A lifting seat (203) is threaded to the outer side of the threaded screw (202). A connecting seat (204) is fixedly connected to the left side of the lifting seat (203). A limit frame (205) is movably connected to the left side of the connecting seat (204). A cold source tank (206) is placed inside the testing cabinet (1). A radiation film working box (207) is set on the top of the cold source tank (206).

2. The radiation-cooled thin film power measuring device according to claim 1, characterized in that: The top of the lifting platform (201) is rotatably connected to a rotary disk (3). There are two threaded screws (202). The tops of the two threaded screws (202) are coaxially fixed with sprockets (4). The two sprockets (4) are connected by a chain drive. The bottom of the rotary disk (3) is coaxially fixed with one of the sprockets (4).

3. The radiation-cooled thin film power measuring device according to claim 1, characterized in that: The connecting seat (204) is provided with an angle adjustment structure (5). The angle adjustment structure (5) includes a worm gear (501) rotatably connected to the inside of the connecting seat (204). A turntable seat (502) is rotatably connected to the inner left wall of the connecting seat (204). A worm gear shaft (503) is coaxially fixed to the right side of the turntable seat (502), and the turntable seat (502) extends through to the left side of the connecting seat (204). The worm gear (501) meshes with the outer side of the worm gear shaft (503). The limiting frame (205) includes a frame plate (2051) fixedly connected to the left side of the turntable seat (502). Two adjusting screws (2052) are rotatably connected inside the frame plate (2051).

4. The radiation-cooled thin film power measuring device according to claim 3, characterized in that: The two adjusting screws (2052) are provided with two symmetrical threaded rings (6) on their outer sides. The outer sides of the two threaded rings (6) are threaded with first clamping arms (2053). Sponge pads (7) are fixedly connected to the opposite side of the two first clamping arms (2053). The outer sides of the two sponge pads (7) are covered with threaded rubber layers. The outer sides of the other two threaded rings (6) are threaded with second clamping arms (2054). The opposite side of the two second clamping arms (2054) is fixedly connected with arc-shaped clamping rings (2055). The inner sides of the two clamping rings (2055) are fixedly connected with spring groups (8).

5. The radiation-cooled thin film power measuring device according to claim 1, characterized in that: The cold source tank (206) includes a vacuum tank body (2061) placed inside the two second clamping arms (2054). A sealing cover plate (2062) is hinged to the top of the vacuum tank body (2061). Anodized black aluminum sheets are fixedly connected to both the inner side of the sealing cover plate (2062) and the inner bottom wall of the vacuum tank body (2061). A sealing ring is fixedly connected to the inner side of the sealing cover plate (2062). A connecting pipe (2063) with a valve is fixedly connected to the left side of the vacuum tank body (2061).

6. The radiation-cooled thin film power measuring device according to claim 5, characterized in that: The right side and back of the vacuum tank (2061) are fixedly connected to a first vacuum tube (2064). A Dewar flask (2065) is placed on top of one of the black aluminum sheets. The Dewar flask (2065) is filled with liquid nitrogen. The vacuum tank (2061) is connected to an external vacuum pump through the first vacuum tube (2064) to form a vacuum chamber structure. The radiation film working box (207) includes a measuring box (2071) placed on top of a sealing cover plate (2062). A boss is fixedly connected to the inner bottom wall of the measuring box (2071). A clamping plate (2072) is assembled on the top of the boss.

7. The radiation-cooled thin film power measuring device according to claim 5, characterized in that: The clamp plate (2072) has a hollow slot at its inner center. An alumina ceramic heating disc (2073) is fixedly attached to the inner side of the hollow slot. A radiation thin film layer (2074) is attached to the top of the heating disc (2073). A first mounting hole (9) is provided on the inner left wall of the measuring box (2071). A second vacuum tube (2075) is fixedly installed inside the first mounting hole (9). A vacuum pressure gauge (10) is fixedly installed outside the second vacuum tube (2075). A second mounting hole (11) is provided on the inner right wall of the measuring box (2071).

8. The radiation-cooled thin film power measuring device according to claim 7, characterized in that: The inner top wall of the measuring box (2071) has a circular radiation window (2076). The radiation window (2076) is a zinc selenide structure layer and is located directly above the heating disc (2073). A first thermocouple (2077) is fixedly installed on the inner top wall of the measuring box (2071) on the side close to the radiation window (2076), and a second thermocouple (2078) is fixedly installed on the side away from the radiation window (2076). The heating disc (2073), the first thermocouple (2077), and the second thermocouple (2078) are all connected to external cables through the second mounting hole (11).

9. A method for measuring the power of a radiation-cooled thin film, characterized in that: The radiation-cooled thin film power measuring device according to claims 1-8 further includes the following operating steps: S1. Preparatory operation: Operate the PLC system, first pre-cool the Dewar bottle (2065) by introducing a small amount of liquid nitrogen, and then continuously introduce sufficient liquid nitrogen and seal it. Prepare a radiation thin film layer (2074) of appropriate size according to the size of the heating disc (2073). Apply thermal grease evenly to seal the radiation thin film layer (2074) to the top of the heating disc (2073). Then, place the temperature probe of the first thermocouple (2077) in the center of the radiation thin film layer (2074), and place the temperature probe of the second thermocouple (2078) on the side away from the radiation thin film layer (2074). Connect a vacuum pump to the second vacuum tube (2075), and after the vacuum pump is stable, evacuate the second vacuum tube (2075) and the measuring box (2071) for vacuum treatment. S2. Assembly Operation: Place the Dewar flask (2065) steadily onto the black aluminum sheet on the bottom wall of the vacuum tank (2061). After sealing with the sealing cover (2062), vacuum is drawn through the external vacuum pump connected to the first vacuum tube (2064). Then, fix the measuring box (2071) with the radiation window (2076) facing down inside the transparent frame. At this time, the radiation film layer (2074) is directly opposite the center of the sealing cover (2062) and the frame is placed on the top of the vacuum tank (2061). Connect all the cables leading out from the second mounting hole (11) to the PLC control system. Then, rotate the two adjusting screws (2052) respectively to clamp and fix the measuring box (2071) by the first clamping arm (2053) and the vacuum tank (2061) by the second clamping arm (2054). By rotating the threaded screw (202) and the worm (501), adjust the measuring box (2071) and the vacuum tank (2061) to a suitable height and angle. S3. Experimental operation: A power module (12) and a touch screen (13) are set on the test cabinet (1). First, turn on the power module (12), set the voltage and current values ​​of 1.0V and 0.5A respectively on the power module (12), then turn on the environmental switch on the touch screen (13), and then turn on the main switch. The heat of the radiation film layer (2074) is radiated to the liquid nitrogen in the Dewar flask (2065) through the radiation window (2076) and the black aluminum sheet, and the data of the ambient temperature and the radiation film temperature are collected by using the first thermocouple (2077) and the second thermocouple (2078). At this time, the heating temperature is set to be the same as the ambient temperature by using the constant power of 100-200 W / m 2 The heating wafer (2073) in the range of 100-200 W / m is used to reheat the radiation film layer (2074) to the same temperature as the ambient temperature, and the heating time of the heating wafer (2073) is recorded. S4. Data processing: After one minute, read the voltage data V, current data A, high-level data t1, and total cycle data T during heating. Then calculate the value of (VAt1) / (radiation film area × T). If the value is around 110, continue the experiment. If the value is too large or too small, stop the experiment and check whether there are any irregularities in the previous steps. The experiment takes about 30 minutes. After the experiment is completed, the experimental data displayed on the touch screen (13) is extracted and the data is plotted. Then, the cooling power of the tested radiation film is calculated by converting the heating efficiency of the heating disc (2073).

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