An experimental device and method for evaluating the refrigeration performance of a radiative cooling material

Abstract

This invention discloses an experimental apparatus and method for evaluating the cooling performance of radiative cooling materials. The experimental apparatus includes a heat sink and a cover; the cover and the heat sink form a chamber; the cover is made of an atmospheric simulation material as described in this invention; the polymer film layer in the atmospheric simulation material is disposed along one side close to the heat sink. The apparatus for evaluating the performance of radiative cooling materials in this invention can simulate the radiative heat transfer behavior of the Earth's atmosphere and operate in the same wavelength-accurate radiative heat transfer mode as a 100 km thick atmosphere. This allows for experiments to be conducted in a laboratory environment under simulated atmospheric conditions, and the experimental conditions can be kept consistent across different batches to achieve experimental repeatability. This enables accurate evaluation of the performance of various radiative cooling materials, keeping the total testing error of radiative cooling materials within 10 W / m². 2 The following has high precision.

Description

Technical Field

[0001] This invention relates to the field of radiation cooling materials technology, and in particular to an experimental apparatus and method for evaluating the cooling performance of radiation cooling materials. Background Technology

[0002] Ground-based radiative cooling materials release heat energy into the frigid outer space through spectrally selective infrared emission. They can create cold surfaces below ambient temperature without consuming electricity or energy, promising a highly efficient, energy-saving, and zero-carbon cooling solution that complements traditional energy-intensive cooling technologies. This field has seen rapid development in recent years, with thousands of related publications annually. Current research focuses on developing new materials with high cooling performance, exploring cost-effective manufacturing methods, constructing cooling systems, and exploring their potential applications in construction, textiles, and water harvesting. Furthermore, the concept of ground-based radiative cooling has been extended to atmospheric and climate research.

[0003] The cooling performance of radiative cooling materials is influenced by atmospheric conditions and radiative heat transfer with the surrounding environment. Therefore, their performance is highly dependent on the geographical location and weather conditions of the outdoor experiment. On the other hand, inaccurate environmental temperature measurements and improper calculations of environmental heat transfer can lead to overestimation of radiative cooling power, a recurring problem in the literature. A standardized method is needed to evaluate the performance of radiative cooling materials. However, to date, there is no standardized method to accurately evaluate and compare the actual cooling performance of the rapidly emerging radiative cooling materials. This is because, firstly, the effectiveness of radiative cooling is extremely sensitive to geographical location, local climate, and real-time weather conditions. Except for experiments conducted simultaneously, no two outdoor experiments can be performed under identical conditions. These differences further complicate the accurate evaluation and comparison of the actual cooling performance of radiative cooling materials. Secondly, radiative cooling materials are diverse, and their spectral responses are closely related to their structure and composition, resulting in almost all reported materials having different spectral characteristics and significant cooling performance. Furthermore, accurately measuring radiative cooling capacity in outdoor experiments is very challenging in practice. Naturally occurring convection and heat conduction have a significant impact on the results, the specific degree of which varies depending on the specific experimental setup. In addition, inaccurate measurements of ambient temperature and heat transfer can also lead to serious deviations in the results.

[0004] A key challenge in accurately evaluating or testing the cooling performance of radiative cooling materials lies in simulating a standard atmospheric environment within an experimental setup to assess the material's cooling capacity. However, reproducing the radiative cooling process driven by the spectral characteristics of a 100-kilometer-thick atmosphere in a laboratory environment is extremely challenging because laboratory systems are typically closed and limited in size. Summary of the Invention

[0005] In order to overcome at least one of the technical problems existing in the prior art, one of the objectives of the present invention is to provide an atmospheric simulation material.

[0006] A second objective of this invention is to provide an experimental apparatus for evaluating the cooling performance of radiation-cooled materials.

[0007] The third objective of this invention is to provide a method for evaluating the cooling performance of radiation cooling materials.

[0008] The fourth objective of this invention is to provide the application of the above-mentioned atmospheric simulation material, the above-mentioned experimental apparatus for evaluating the cooling performance of radiation-cooled materials, or the above-mentioned method for evaluating the cooling performance of radiation-cooled materials in the field of performance testing of radiation-cooled materials.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides an atmospheric simulation material, comprising a stacked metal substrate layer and a polymer film layer; the polymer film layer contains a polymer and spectral resonance particles; the spectral resonance particles are distributed in the polymer film layer; The spectral resonance particles include ilmenite particles.

[0010] In this invention, ilmenite particles are used as the main component to achieve effective simulation of atmospheric spectrum.

[0011] In some embodiments of the present invention, the spectral resonance microparticles further include nitrate particles. Ilmenite particles are the primary material for effectively simulating the spectral characteristics of the atmosphere. Nitrate particles, such as potassium nitrate, sodium nitrate, and ammonium nitrate, are used as small additives to assist ilmenite particles in achieving more accurate atmospheric spectral characteristics simulation.

[0012] In some embodiments of the invention, the atmospheric simulation material has the same infrared emissivity as the atmosphere. This ensures consistent radiative heat exchange between the atmosphere and any radiatively cooled material. However, within the infrared spectral window where the atmosphere is transparent, the atmospheric simulation material exhibits high reflectivity, redirecting the heat flow that would otherwise be transferred to the cold universe, into a cryogenic cold source.

[0013] In some embodiments of the present invention, the atmospheric simulation material is black. When the atmospheric simulation material is black, it is possible to minimize the multiple reflections of solar radiation back onto the radiation-cooled material sample.

[0014] In some embodiments of the present invention, when only ilmenite particles are used as spectral resonance microparticles, with the total volume of the polymer film layer being 1, the volume fraction of the polymer is 0.9~0.93, and the volume fraction of the ilmenite particles is 0.07~0.1.

[0015] In some embodiments of the present invention, when ilmenite particles and nitrate particles are used as spectral resonance microparticles, with the total volume of the polymer film layer as 1, the volume fraction of the polymer is 0.85~0.885, the volume fraction of the ilmenite particles is 0.07~0.1, and the volume fraction of the nitrate particles is 0.045~0.05. In some embodiments of the present invention, with the total volume of the polymer film layer as 1, the volume fraction of the polymer is any value or a range formed by any two of 0.85, 0.855, 0.86, 0.865, 0.87, 0.875, 0.88, and 0.885. In some embodiments of the present invention, with the total volume of the polymer film layer as 1, the volume fraction of the ilmenite particles is any value or a range formed by any two of 0.07, 0.08, 0.09, and 0.1. In some embodiments of the present invention, with the total volume of the polymer film layer being 1, the volume fraction of the nitrate particles is any value of 0.045, 0.046, 0.047, 0.048, 0.049, 0.05 or a range formed by any two of these values.

[0016] This invention achieves the performance of simulating a 100-kilometer-thick atmosphere with different humidity levels by adjusting the ratio of polymer and spectral resonance particles in the polymer film layer.

[0017] In some embodiments of the present invention, the polymer is an infrared-transparent polymer. In some embodiments of the present invention, the polymer is a transparent polymer.

[0018] In some embodiments of the present invention, the average particle size of the ilmenite particles is 0.1~10 μm; in some embodiments of the present invention, the average particle size of the ilmenite particles is any value or a range formed by any two of the following: 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm; in some preferred embodiments of the present invention, the average particle size of the ilmenite particles is 2 μm.

[0019] In some embodiments of the present invention, the average particle size of the nitrate particles is 0.1~10 μm; in some embodiments of the present invention, the average particle size of the nitrate particles is any value or a range formed by any two of the following: 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm; in some preferred embodiments of the present invention, the average particle size of the nitrate particles is 2 μm.

[0020] In some embodiments of the present invention, the material of the ilmenite particles is FeTiO3.

[0021] In some embodiments of the present invention, the material of the nitrate particles includes at least one of sodium nitrate, potassium nitrate, and ammonium nitrate.

[0022] In some embodiments of the present invention, the polymer includes at least one of polyethylene, polypropylene, polycarbonate, and polyurethane.

[0023] In some embodiments of the present invention, the thickness of the polymer film layer is 30~200μm; in some embodiments of the present invention, the thickness of the polymer film layer is any value or a range formed by any two of the following: 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, 130μm, 140μm, 150μm, 160μm, 170μm, 180μm, 190μm, 200μm.

[0024] In some embodiments of the present invention, the material of the metal substrate layer includes at least one of aluminum foil, copper foil, and tin foil.

[0025] In some embodiments of the present invention, the thickness of the metal substrate layer is 1~100μm; in some embodiments of the present invention, the thickness of the metal substrate layer is 20~40μm; in some embodiments of the present invention, the thickness of the metal substrate layer is 30μm.

[0026] A second aspect of the present invention provides an experimental apparatus for evaluating the cooling performance of a radiation-cooling material, comprising a heat sink and a cover; the cover and the heat sink are arranged to form a chamber; the material of the cover is the atmospheric simulation material described in the first aspect of the present invention; the polymer film layer in the atmospheric simulation material is disposed along one side close to the heat sink.

[0027] In some embodiments of the present invention, the shape of the cover may be hemispherical, cubic, or the like.

[0028] In some embodiments of the present invention, the experimental apparatus further includes a transparent window and a solar simulator; the transparent window is located on the cover; light emitted by the solar simulator enters the cavity through the transparent window.

[0029] In some embodiments of the present invention, the transparent window is made of at least one of quartz, glass, and sapphire. The transparent window is primarily for allowing sunlight to pass through and enter the cavity.

[0030] In some embodiments of the present invention, the experimental apparatus further includes a sample placement rack; the sample placement rack is disposed on the heat sink and located within the cavity; the sample placement rack is used to place radiation cooling material.

[0031] In some embodiments of the present invention, a reflective layer is provided on the surface of the sample holder; in some embodiments of the present invention, the reflective layer is aluminum foil, and using aluminum foil to cover the sample holder can reduce the error caused by thermal radiation heat transfer.

[0032] In some embodiments of the present invention, the experimental apparatus further includes a fluid channel disposed on the heat sink. In some embodiments of the present invention, the fluid channel is connected to a fluid source, and the temperature of the heat sink can be controlled by controlling the temperature of the fluid flowing in the fluid channel.

[0033] In some embodiments of the invention, the experimental apparatus further includes a heater for heating the cover. The heater is primarily used to control the temperature of the cover surface.

[0034] In some embodiments of the present invention, the experimental apparatus further includes a cooler; the cooler is used to control the temperature of the heat sink.

[0035] In some embodiments of the present invention, the experimental apparatus further includes a heating unit and a metal heat spreader; the heating unit is provided with a metal heat spreader, and the radiation cooling material is placed on the metal heat spreader. In some embodiments of the present invention, the heating unit is a heater. In some embodiments of the present invention, the metal heat spreader is a copper plate.

[0036] In some embodiments of the present invention, the heating unit and / or the surface of the metal heat exchange plate are covered with aluminum foil.

[0037] In a simulated atmospheric material environment, this invention allows for independent control of parameters such as the operating temperature of the cover, heat sink, and radiative cooling material sample, as well as the ambient temperature, when measuring the characteristic curves of radiatively cooled materials using heaters, coolers, and heating elements. These characteristic curves can be used to effectively evaluate non-radiative and convective heat transfer in specific applications.

[0038] In some embodiments of the present invention, the radiation cooling material includes at least one of window-type radiation cooling material and blackbody-type radiation cooling material.

[0039] In some embodiments of the present invention, the blackbody radiation cooling material includes a metal substrate and a polyethylene terephthalate (PET) film layer disposed on the metal substrate; in some embodiments of the present invention, the material of the metal substrate is aluminum.

[0040] In some embodiments of the present invention, the thickness of the metal substrate is 10-50 μm; in some embodiments of the present invention, the thickness of the metal substrate is 20-40 μm; in some embodiments of the present invention, the thickness of the metal substrate is 30 μm.

[0041] In some embodiments of the present invention, the thickness of the polyethylene terephthalate (PET) film layer is 0.1-0.3 mm; in some embodiments of the present invention, the thickness of the polyethylene terephthalate (PET) film layer is 0.2 mm.

[0042] In some embodiments of the present invention, the window-type radiative cooling material includes a stacked reflective substrate layer and a solution-derived SiO2 layer. x N y Thin film layer and SiO2 particle layer, the solution-derived SiO x N y The thin film layer is sandwiched between a reflective substrate and a layer of self-assembled SiO2 particles. (This spectrally selective / windowed cooling material is from C. Lin, Y. Li, Y. Kwon, J. Huang, Z. Wu, J. Zheng, G. Liu, C. Tso, C. Chao, B. Huang, Asolution-processed inorganic emitter with high spectral selectivity for efficient subambient radiative cooling in hot humid climate.) Advanced Materials34, 2109350 (2022). doi:10.1002 / adma.202109350).

[0043] In some embodiments of the present invention, the experimental apparatus further includes at least one temperature sensor for monitoring the temperature of at least one selected from a cover, a heat sink, and a radiative cooling material.

[0044] In some embodiments of the present invention, the at least one temperature sensor is in contact with the radiative cooling material; in some embodiments of the present invention, the at least one temperature sensor is disposed on the side of the radiative cooling material opposite to the cover.

[0045] In some embodiments of the present invention, the heat sink is made of black anodized aluminum.

[0046] In some embodiments of the present invention, the emissivity of the heat sink is 0.9 to 1.0; in some embodiments of the present invention, the emissivity of the heat sink is any value of 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1 or a range formed by any two of them.

[0047] In some embodiments of the present invention, the area of ​​the radiative cooling material is much smaller than the area of ​​the atmospheric simulation material. In some embodiments of the present invention, the ratio of the area of ​​the radiative cooling material to the area of ​​the atmospheric simulation material is 0.01-0.05; in some embodiments of the present invention, the ratio of the area of ​​the radiative cooling material to the area of ​​the atmospheric simulation material is 0.02-0.04; in some embodiments of the present invention, the ratio of the area of ​​the radiative cooling material to the area of ​​the atmospheric simulation material is 0.03.

[0048] In some embodiments of the present invention, the radiative cooling material is circular; the diameter of the radiative cooling material is ≤10cm.

[0049] In some embodiments of the present invention, the area of ​​the inner surface of the cover is 2000~3000 cm². 2 .

[0050] In some embodiments of the present invention, the area of ​​the atmospheric simulation material is the same as the area of ​​the heat sink.

[0051] A third aspect of the present invention provides a method for evaluating the performance of a radiation-cooling material, comprising the following steps: A temperature sensor is mounted on the radiative cooling material and then placed in the chamber of the experimental apparatus for evaluating the cooling performance of the radiative cooling material as described in the second aspect of the present invention. A vacuum is drawn, and then the temperature and cooling power of the radiation cooling material are measured. Based on the measured temperature and cooling power, a curve showing the relationship between cooling power and ambient temperature is plotted to obtain the cooling performance of the radiation cooling material.

[0052] The fourth aspect of the present invention provides the application of the atmospheric simulation material described in the first aspect of the present invention, or the experimental apparatus for evaluating the cooling performance of the radiative cooling material described in the second aspect of the present invention, or the method for evaluating the performance of the radiative cooling material described in the third aspect of the present invention, in the field of performance testing of radiative cooling materials.

[0053] The beneficial effects of this invention are: the atmospheric simulation material of this invention can effectively simulate the spectral and radiative thermal response of a 100-kilometer-thick atmosphere by embedding spectral resonance microparticles in a polymer thin film layer. It can be used in a laboratory environment to simulate the behavior and characteristics of a 100-kilometer-thick atmosphere and replicate the radiative heat transfer between the radiative cooling material and the atmosphere, which has great advantages in evaluating the performance of radiative cooling materials.

[0054] The experimental apparatus for evaluating the cooling performance of radiation-cooled materials in this invention can simulate the radiative heat transfer behavior of the Earth's atmosphere and operate in a radiative heat transfer mode with the same wavelength accuracy as a 100-kilometer-thick atmosphere. This allows for experiments to be conducted in a laboratory environment under simulated atmospheric conditions, and ensures that experimental conditions are consistent across different batches of experiments. This allows for the accurate evaluation of the performance of various radiation-cooled materials under identical conditions, maintaining the total testing error of radiation-cooled materials within 10 W / m². 2 The following parameters demonstrate high precision. Furthermore, this experimental setup can simulate various day / night conditions or atmospheric conditions by changing various parameters.

[0055] The method for evaluating the performance of radiation cooling materials in this invention is simple to operate, requires little skill from operators, and can be widely applied. Attached Figure Description

[0056] Figure 1 This is a schematic diagram illustrating the mechanism of radiation cooling of surface material samples in the external environment according to the present invention.

[0057] Figure 2 This is a diagram showing the emission spectrum and transmittance of dry air.

[0058] Figure 3 This is a schematic diagram of the experimental apparatus for evaluating the performance of radiation cooling materials in an embodiment of the present invention.

[0059] Figure 4This is a diagram showing the required spectral emissivity and transmittance of the atmospheric simulation material in the atmosphere according to an embodiment of the present invention.

[0060] Figure 5 This is a schematic diagram of the structure of the atmospheric simulation material in an embodiment of the present invention.

[0061] Figure 6 This is a diagram showing the absorption efficiency coefficients of ilmenite particles and nitrate particles in an embodiment of the present invention.

[0062] Figure 7 The image shows the spectral radiative power of atmospheric simulation materials under three different atmospheric conditions (low humidity, medium humidity, and high humidity) according to an embodiment of the present invention.

[0063] Figure 8 This is a comparison chart of the spectral radiative power of the atmospheric simulation material in this embodiment of the invention under moderate humidity and the spectral radiative power of the actual moderate humidity atmosphere.

[0064] Figure 9 The graph shows the relationship between the radiative cooling power of two typical radiative cooling materials in the broadband transmitter (or blackbody type) and wavelength-selective transmitter (or window type) embodiments of the present invention and the temperature difference between the sample and the air. The smaller graph shows the spectral emissivity of these two typical radiative cooling materials.

[0065] Figure 10 This is a physical diagram of the experimental apparatus used to evaluate the performance of radiation-cooled materials in an embodiment of the present invention.

[0066] Figure 11 This is a spectral emissivity diagram of a wideband transmitter and a wavelength-selective transmitter in an embodiment of the present invention.

[0067] Figure 12 The graph shows the cooling power characteristics of a wideband transmitter and a wavelength-selective transmitter measured in an embodiment of the present invention during simulated nighttime and daytime conditions.

[0068] Figure 13 The diagram shows the net cooling power of the wavelength-selective sample under different non-radiative heat transfer coefficients according to an embodiment of the present invention.

[0069] Figure label: Cooling surface 102, atmosphere 104, universe 106, experimental device 200, radiation cooling material 202, cover 204, heat sink 206, chamber 208, transparent window 210, sunlight simulator 212, heating element 220, first thermocouple 232, second thermocouple 234, third thermocouple 236, atmosphere simulation material 300, polyethylene film layer 302, nitrate particles 304, ilmenite particles 306. Detailed Implementation

[0070] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0071] like Figure 1 As shown, surface radiative cooling achieves net heat loss to the cold outer space through infrared radiation via atmospheric windows. For surface radiative cooling, the cooling surface 102 of the radiative cooling material... s (λ), T s Infrared radiation allows heat to pass through the infrared atmospheric window and be emitted into the cold outer space. Earth's atmosphere has a depth of 10⁴ ( ). atm (λ), T atm It exhibits high transmittance within the atmospheric window spectral range of 8-13 μm, such as Figure 2 As shown, the emission spectrum and transmittance (emissivity and transmittance are taken from the MODTRAN database) of a dry atmosphere are well-matched, while Universe 106 is cold and capable of absorbing heat emitted by radiatively cooling materials. The spectral characteristics required to simulate the atmosphere are as follows: Figure 2 As shown. Currently, no single material fully meets these specific requirements. However, the process of combining stochastic resonant optical scatterers with polymer photonics is scalable and has been successfully used to fabricate passive radiative cooling materials for large-scale applications. Atmospheric simulation material 300 can be prepared using the same strategy.

[0072] Example 1 This example provides an atmospheric simulation material, which consists of an aluminum foil and a polyethylene film layer disposed on the aluminum foil. The polyethylene film layer contains uniformly dispersed iron ilmenite particles and sodium nitrate particles (which can also be replaced by potassium nitrate or ammonium nitrate particles). The material of the ilmenite particles is FeTiO3; the average particle size of both the ilmenite particles and the nitrate particles is 2 μm (this particle size value is better than other particle size values). Taking the total volume of the polyethylene film layer as 1, the volume fraction of ilmenite v,钛铁矿 The volume fraction of nitrate is 0.07. v,硝酸盐 The volume fraction of polyethylene is 0.045. v,聚乙烯 It is 0.885; The thickness of the polyethylene film layer is 62 μm; The atmospheric simulation material used in this example is used to simulate an atmosphere with low humidity (its total water vapor capacity is 1.5 cm).

[0073] Example 2 This example provides an atmospheric simulation material, which consists of an aluminum foil and a polyethylene film layer disposed on the aluminum foil. The polyethylene film layer contains uniformly dispersed iron ilmenite particles and sodium nitrate particles (which can also be replaced by potassium nitrate or ammonium nitrate particles). The material of the ferroilite particles is FeTiO3; The average particle size of both the ilmenite and nitrate particles is 2 μm. Taking the total volume of the polyethylene film layer as 1, the volume fraction of ilmenite v,钛铁矿 The volume fraction of nitrate is 0.1. v,硝酸盐 The volume fraction of polyethylene is 0.05. v,聚乙烯 It is 0.85; The thickness of the polyethylene film layer is 69 μm; The atmospheric simulation material used in this example is an atmosphere with moderate humidity (its total water vapor capacity is 3 cm).

[0074] Example 3 This example provides an atmospheric simulation material, which consists of an aluminum foil and a polyethylene film layer disposed on the aluminum foil. The polyethylene film layer contains uniformly dispersed iron ilmenite particles and sodium nitrate particles (which can also be replaced by potassium nitrate or ammonium nitrate particles). The material of the ilmenite particles is FeTiO3; the average particle size of both the ilmenite particles and the nitrate particles is 2 μm. Taking the total volume of the polyethylene film layer as 1, the volume fraction of ilmenite v,钛铁矿 The volume fraction of nitrate is 0.1. v,硝酸盐 The volume fraction of polyethylene is 0.05. v,聚乙烯 It is 0.85; The thickness of the polyethylene film layer is 155 μm; The atmospheric simulation material used in this example is used to simulate an atmosphere with high humidity (its total water vapor capacity is 6 cm).

[0075] Example 4 Reference Figure 3 The present invention provides an experimental apparatus 200 for evaluating the performance of radiation-cooled materials, as shown in the structural diagram. This experimental apparatus 200 is capable of simulating the thermal properties of the atmosphere. The experimental apparatus 200 includes: Heat sink 206, which has a blackbody surface, is used to absorb radiative heat on radiative cooling material 202. The low reflectivity and temperature of heat sink 206 are designed to simulate the thermal effects of the universe in radiative cooling.

[0076] And a cover 204 for covering the heat sink 206, the cover 204 being made of an atmosphere simulation material 300 (for example, any of the atmosphere simulation materials in Examples 1 to 3 may be used); The chamber 208 is formed by assembling a heat sink 206 and a cover 204 together, and the chamber 208 contains a radiation cooling material 202; The cover 204 covers the heat sink 206 and the radiative cooling material 202, and there is a certain distance between the cover 204 and the radiative cooling material 202; The heat sink 206 has a base surface, the radiative cooling material 202 has a cooling surface, and the cover 204 has a simulated atmospheric surface. Figure 3 It can be seen that the heat sink 206, the radiative cooling material 202, and the cover 204 define three surfaces with different thermal properties, which are the cooling surfaces of the radiative cooling material 202. 1(λ), T 1) The atmospheric simulation surface of the cover 204 ( 2(λ), T 2) and the surface of the cold source simulated by heat sink 206 ( 3(λ), T 3) These surfaces constitute the structure of the actual surface-atmosphere-universe device. The cold source surface absorbs radiant heat from the cooling surface, and theoretically it can be located below the atmospheric simulation material 300. However, in order to maintain a constant temperature, the atmospheric simulation material 300 must maintain good thermal contact with the temperature control device. Therefore, the atmospheric simulation material 300 is preferably opaque and has spectral reflectivity.

[0077] In some embodiments of the invention, the cold source surface may be located below or near the cooling surface. The radiative heat transfer connecting the cooling surface to the cold universe (which would normally occur through the atmosphere) is now redirected and directed to the cold source surface via the spectral selective reflection of the atmospheric simulation material 300.

[0078] This experimental setup 200 can simulate the outdoor natural environment on a small scale in a laboratory setting, enabling performance evaluation or testing of radiative cooling materials in a laboratory environment. The setup 200 can reproduce the radiative cooling process by simulating the spectral characteristics of a 100-kilometer-thick atmosphere. In this example, the setup 200 can be used to evaluate the cooling performance of radiative cooling materials under conditions without sunlight. The setup 200 can perform comparative tests on different radiative cooling materials under standardized atmospheric conditions, with a measurement accuracy error of less than 10 W / m. 2 .

[0079] In some embodiments of the invention, the cover 204 includes a window 210. In some embodiments of the invention, the window 210 may be a transparent window to allow sunlight to enter the cavity 208. In some embodiments of the invention, such as Figure 3 As shown, the transparent window 210 is located on the cover 204 near the highest point of the cover 204. In some embodiments of the present invention, the window 210 may be formed at the highest point of the cover 204, for example, the window 210 may be formed at the apex of the cover 204.

[0080] In some embodiments of the present invention, window 210 may be made of quartz. In some embodiments of the present invention, window 210 may be made of sapphire. In some embodiments of the present invention, window 210 may be made of glass.

[0081] In some embodiments of the present invention, the cover 204 may be curved or arc-shaped. In some embodiments of the present invention, such as... Figure 3 As shown, the cover 204 is hemispherical.

[0082] In some embodiments of the present invention, such as Figure 3 As shown, the radiative cooling material 202 is disposed on one side of the heat sink 206 along the direction close to the cover 204, such that the radiative cooling material 202 faces the hemispherical cover 204. In some embodiments of the present invention, during use, the radiative cooling material 202 is placed on top of the heat sink 206, such that the radiative cooling material 202 faces the cover 204.

[0083] In some embodiments of the present invention, the heat sink 206 is made of black anodized aluminum foil. The emissivity of the black anodized aluminum foil is close to 1. The heat sink 206 may be a blackbody surface.

[0084] In some embodiments of the invention, the radiative cooling material 202 and the heat sink 206 are located inside a chamber 208 formed by a cover 204. During device assembly, the cover 204 includes or surrounds the radiative cooling material 202 and the heat sink 206. In some embodiments of the invention, a sealed chamber 208 may be formed between the cover 204 and the heat sink 206. In some embodiments of the invention, the vacuum pressure inside the chamber is <1 psi during use. The chamber 208 may be under vacuum during use. The chamber 208 may be maintained at a vacuum pressure below 1 psi to reduce conduction and convection losses. In some embodiments of the invention, the vacuum pressure level in the chamber 208 may be adjusted. The vacuum state within the chamber 208 reduces heat loss within the chamber 208 and ensures improved thermal bonding between the atmospheric simulation material 300 on the cover 204 and the radiative cooling material 202. The vacuum state reduces any errors caused by unintentional heat loss or heat transfer between the radiative cooling material 202 and the air in the chamber 208. Therefore, removing air through a vacuum can reduce errors when evaluating the performance of radiation-cooled materials.

[0085] In some embodiments of the invention, the experimental apparatus 200 further includes a solar simulator 212. The solar simulator 212 is disposed on the side of the window 210 away from the radiation-cooling material 202. The solar simulator 212 is capable of generating light and / or electromagnetic radiation to simulate solar radiation intensity. In use, the light and / or electromagnetic radiation generated by the solar simulator 212 is transmitted into the chamber 208 through the window 210.

[0086] In some embodiments of the present invention, the heat sink 206 further includes a fluid channel formed therein. Figure 3 (not shown in the image) to enable its temperature control. This fluid channel can be connected to a fluid source.

[0087] In some embodiments of the present invention, the cover 204 employs an atmospheric simulation material 300, which is typically opaque and has spectral reflectivity within the atmospheric window spectral range, used to simulate the spectral and thermal response (spectral emissivity) of a 100 km thick atmosphere. This atmospheric simulation material comprises an aluminum foil layer and a 50 μm thick optical film disposed on the surface of the aluminum foil layer; this atmospheric simulation material can effectively simulate the spectral and radiative thermal response of a 100 km thick atmosphere. The optical film is made of infrared-transparent low-density polyethylene (density 0.91 g / cm³). 3 It is made by embedding particles with spectral resonance characteristics (such as ilmenite particles and / or nitrate particles) into the material, enabling the reproduction of radiative heat transfer between a cooled surface and an atmospheric surface in a laboratory setting. Infrared transparency refers to the property of allowing infrared radiation to pass through.

[0088] Figure 4 The required spectral emissivity and transmittance for the atmospheric simulation material were demonstrated through theoretical calculations. For reference, Figure 2 and Figure 4 The medium gray and yellow shaded backgrounds represent the solar spectrum at AM1.5 (labeled as region X, gray area) and the blackbody emission spectrum at 300K (labeled as region Y, yellow area), respectively. The radiative heat transfer of the radiative cooling material 202 is redirected and directed to the heat sink 206 through the atmospheric simulation of the spectral selective reflection of material 300 by the covering 204. (As shown...) Figure 4 As shown, the atmospheric simulation material 300 has a spectral emissivity in the infrared region that is basically the same as that of the atmosphere, but it needs to be reflective in the spectral range where the actual atmosphere is transparent. This allows the atmospheric simulation material 300 to reject the thermal radiation of the radiatively cooled material sample in the atmospheric window and redirect it to the heat sink 206 (simulating a cold blackbody) when the viewing angle ratio between the atmosphere and the radiatively cooled material sample is small enough.

[0089] To evaluate the daytime performance of the cooling surface of the radiative cooling material 202, this invention introduces a solar simulator 212 to simulate normal solar radiation intensity at noon. Part of the solar radiation is directly absorbed by the radiative cooling material 202 sample, while the remainder is reflected to the upper hemispherical atmospheric simulation (i.e., the upper part of the cover 204), undergoing multiple reflections and absorption by both the radiative cooling material 202 sample and the atmospheric simulation material 300. To eliminate the reabsorption caused by multiple reflections in the radiative cooling material sample, the atmospheric simulation material 300 has a high emissivity (approximately 1) across the solar spectral band. Figure 4 As shown, this allows for the complete capture of this portion of solar radiation reflection; therefore, the spectral emissivity of atmospheric simulation material 300 is defined as:

[0090] in, irr ( )and E b ( , T amb ) represent the temperature at room temperature ( T amb , that is T ambientThe solar spectral irradiance and emission power of a blackbody are considered. Adjusting the short-wavelength (visible-near-infrared) emissivity of the atmospheric simulation material 300 to near 1 results in a negligible change in the overall radiative cooling power. This is because the surface of a blackbody (with an emissivity of 1) at room temperature radiates very little energy within a specific wavelength range, accounting for less than 1% of the total radiative energy. This atmospheric simulation material 300 has a high emissivity within the solar spectrum, which not only reduces reabsorption in the presence of solar radiation but also lowers the stringent conditions required for implementing atmospheric simulation materials in experiments. Therefore, the significant power density difference between solar irradiance and the infrared radiation flux emitted by the surface of the radiative cooling material necessitates that the radiative cooling material effectively releases heat energy while absorbing as little sunlight as possible.

[0091] To ensure that the experimental apparatus 200 of this invention can accurately reproduce the Earth's radiative cooling process, the heat sink 206 must be at a sufficiently low temperature, that is, the temperature of the heat sink 206 must be much lower than room temperature (i.e., 3 amb (The temperature difference used in this experiment was 20℃), and the area of ​​the radiation cooling material 202 sample was much smaller than the area of ​​the atmospheric simulation material 300, i.e. 1 2 (This experiment) 1 and (The ratio is 0.03). The symbol "" indicates much smaller. Under specific geometric conditions, quantitative analysis of radiative heat transfer in a closed experimental setup 200 is possible. By equating the radiative heat flux of a radiatively cooled material sample in a laboratory system with the radiative heat flux in an actual surface-atmosphere-space system, this invention proposes the following requirements:

[0092] A 2 and A 3 represents the area of ​​the atmospheric simulation material 300 and the area of ​​the heat sink 206, respectively. T 1. T s , T 2 represents the surface temperature of radiation cooling material 102, radiation cooling material 202 (102 and 202 are the same material, and were placed in the external environment and experimental device respectively for comparison in the analysis), and the surface temperature of atmospheric simulation material 300. 1( ) represents the irradiation dose of the radiation-cooled material sample (i.e., surface 1); irr ( ) is at room temperature ( T amb The solar spectral irradiance of a blackbody.

[0093] In some embodiments of the present invention, the atmospheric simulation material 300 comprises several components that have extremely low infrared absorption rates in the atmospheric window, or may be transparent. The atmospheric simulation material 300 can be a 50 μm thick optical film. The atmospheric simulation material 300 includes a transparent polyethylene film layer and ilmenite particles and nitrate particles distributed within the transparent polyethylene film layer. In some embodiments of the present invention, the atmospheric simulation material 300 includes a polyethylene film layer 302, at least one nitrate particle 304, and at least one ilmenite particle 306. The nitrate particles 304 and ilmenite particles 306 are distributed within the polyethylene film layer 302. The ilmenite particles 306 are composed of FeTiO3, and the nitrate particles 304 are composed of KNO3 and / or NaNO3. This atmospheric simulation material 300 can simulate the radiative heat transfer characteristics of the atmosphere in a laboratory environment, thereby enabling the evaluation of radiative cooling materials in laboratory systems. This atmospheric simulation material 300 can simulate the spectrum of the actual atmosphere, thereby enabling the replication of the spectral radiative heat transfer of radiative cooling materials. The experimental apparatus 200 of this invention uses this atmospheric simulation material 300, which can be used to simulate the radiation properties of the Earth's atmosphere, such as a 100-kilometer-thick atmosphere. This allows the experimental apparatus 200 to be small and compact, enabling its use in a laboratory environment.

[0094] To achieve high emissivity outside the atmospheric window, researchers identified materials within its infrared fingerprint region and utilized these materials to construct resonant optical scatterers. Below the atmospheric window wavelengths, nitrates (such as KNO3 and NaNO3) exhibit extremely strong absorption between 7-8 μm due to the stretching motion between nitrogen-oxygen (NO) bonds. Above the atmospheric window wavelengths, nitrates do not exhibit this absorption property. However, within the atmospheric window range, most long-wavelength emissive materials exhibit strong parasitic absorption. Notably, compounds such as ferric oxide (Fe2O3) have relatively low absorption in this region, but from 16 μm, their absorption increases significantly due to the presence of ferro-oxygen (Fe–O) bonds. To further reduce absorption within this window, this invention selected ilmenite (FeTiO3), the primary ore of titanium. The asymmetric vibration of Fe–Ti–O occurs at 681 cm⁻¹. -1 Its absorption is enhanced at (14.7 μm) while suppressing absorption across the entire atmospheric window. It also exhibits a absorption at 1370 cm⁻¹. -1 A weak absorption band at (7.3 μm) enhances the absorption rate in the wavelength range below the atmospheric window.

[0095] Figure 5 A schematic diagram of an atmospheric simulation material 300 is shown. This atmospheric simulation material 300 comprises a polyethylene film layer, which can be formed by mixing appropriate amounts of the inorganic compounds ilmenite, nitrates, and polyethylene resin. The atmospheric simulation material 300 may comprise a base layer or substrate. The base layer or substrate may be made of a highly reflective metallic material. In some embodiments of the invention, such as Figure 5 As shown, the polyethylene film layer is supported by a reflective aluminum substrate 310. Nitrate particles 304 and ilmenite particles 306 are encapsulated within the polyethylene film layer 302.

[0096] In some embodiments of the present invention, the optimal average particle size of nitrate particles 304 is 2 μm.

[0097] In some embodiments of the present invention, the optimal average particle size of ilmenite particles 306 is 2 μm.

[0098] To develop high-performance atmospheric respiration simulation material 300, the composition and structure of the polyethylene film layer are also important. The absorption efficiency factors of ilmenite and nitrate particles were calculated and plotted. Figure 6 (Calculated by Mie scattering theory). Figure 6 In the diagram, curves 600, 602, and 604 all display the absorption efficiency factor of nitrate particles. Curve 600 (solid line) shows the absorption efficiency factor for nitrate particles with an average particle size of 2 μm; curve 602 (dashed line) shows the absorption efficiency factor for nitrate particles with an average particle size of 5 μm; and curve 604 shows the absorption efficiency factor for nitrate particles with an average particle size of 0.5 μm. Curve 606 (solid line) shows the absorption efficiency factor for ilmenite particles with an average particle size of 2 μm; and curve 608 (dashed line) shows the absorption efficiency factor for ilmenite particles with an average particle size of 5 μm. Curve 610 shows the absorption efficiency factor for ilmenite particles with an average particle size of 0.5 μm.

[0099] Depend on Figure 6It is known that nitrate particles significantly enhance absorption in the 7-8 μm wavelength range. The enhanced wavelength range expands accordingly with increasing nitrate particle size. Furthermore, as nitrate particle size increases, the absorption effect gradually extends beyond 8 μm to the atmospheric window region, particularly noticeable for nitrate particles with an average particle size of 5 μm. Therefore, nitrate particles with an average particle size of 2 μm were chosen to maximize absorptivity / reflectivity in the 7-8 μm wavelength range. On the other hand, ilmenite particles exhibit relatively weak absorption within the atmospheric window but strong intrinsic absorption outside the window. Absorption within the atmospheric window begins to increase when the size of ilmenite particles exceeds 2 μm. Therefore, 2 μm ilmenite particles were used in the development of the atmospheric simulation material 300 in this invention. The emissivity of various standard atmospheric simulation materials 300 at different humidity levels was calculated in this invention.

[0100] Figure 7 The spectral radiant power of atmospheric simulation material 300 (i.e., the atmospheric simulation materials of Examples 1-3) was calculated and presented under three different atmospheric conditions (low humidity, medium humidity, and high humidity). Figure 7 As shown, by changing the volume fractions of ilmenite and nitrate particles and the thickness of the generated atmospheric simulation film, this invention can generate gaseous spectra with different humidity levels. The humidity level is measured by the total precipitable water vapor (TPW, which refers to the total amount of water vapor in the atmosphere perpendicular to the air column under clear sky conditions). Figure 7 The three subplots a, b, and c show the spectral radiative power of the atmospheric simulation material 300 under low, medium, and high humidity conditions, respectively.

[0101] like Figure 7 As shown in Figure a, curve 710 illustrates the spectral radiant power of a low-humidity atmosphere (with a total water vapor capacity of 1.5 cm³), which can be approximated using a thin sheet of atmospheric simulation material containing ilmenite and nitrates, where the volume fraction of ilmenite is... v,钛铁矿 The volume fraction of nitrate is 0.07. v,硝酸盐 The value is 0.045, and the thickness of the polyethylene film layer is h=62μm; Curve 712 shows the spectral radiant power of the atmospheric simulation material 300, which is similar to the spectral radiant power of a low-humidity atmosphere.

[0102] like Figure 7 As shown in Figure b, curve 710 displays the spectral radiant power of a moderately humid atmosphere (with a total water vapor capacity of 3 cm), represented by atmospheric simulation materials, with the following parameters: v,钛铁矿=0.1, v,硝酸盐 =0.05, and the thickness of the polyethylene film layer h=69μm. Curve 712 shows the spectral radiant power of atmospheric simulation material 300, which is approximately the same as that of a moderately humid atmosphere.

[0103] Increasing the film thickness in this simulated humidity environment to h = 155 μm resulted in a film like... Figure 7 The high humidity environment shown in Figure c (with a total water vapor capacity of 6 cm) can be approximated by using the following parameters to simulate the properties of atmospheric materials, similar to those of a high humidity environment: v,钛铁矿 =0.1, v,硝酸盐 =0.05, the thickness of the polyethylene film layer h=155μm. Curve 710 shows the spectral radiant power in a high humidity environment. Curve 712 shows the spectral radiant power of the optimized atmospheric simulation material that can simulate a high humidity environment. Figure 7 In the image, the emission spectrum of a blackbody at room temperature of 300K is used as the gray background region A for comparison.

[0104] Compared with the spectral radiant power under typical atmospheric conditions, the three atmospheric simulation materials in Examples 1-3 showed good consistency with the atmosphere, with a difference of 14 W / m in total heat dissipation. 2 8W / m 2 and 3W / m 2 .like Figure 7 As shown, the improved atmospheric simulation material performs very similarly to its performance under typical atmospheric conditions.

[0105] In some embodiments of the invention, the polyethylene film layer contains only ilmenite particles. Given that most nitrates are strong oxidizing agents, and considering that at room temperature, the spectral energy density at wavelengths outside the atmospheric window (>13 μm) is significantly higher than that below the window (<8 μm), the present invention uses only ilmenite-doped polyethylene films to capture the key spectral features required to simulate atmospheric radiative heat transfer.

[0106] Figure 8 The illustration (i.e., the right-hand image) shows a physical image of one of the atmospheric simulation material samples, with the volume fraction of ilmenite. v,钛铁矿 The volume fraction of nitrate is 0.1. v,硝酸盐 The volume fraction of polyethylene is 0.05. v,聚乙烯The value is 0.85; the thickness of the polyethylene film layer is 50 μm. This ilmenite-doped film is made by thoroughly mixing ilmenite particles and polyethylene powder, and then pressing them onto a highly reflective aluminum foil using a hot-pressing process. This aluminum foil is capable of reflecting infrared light. The spectral response of the atmospheric simulation material doped only with ilmenite was measured using a Fourier transform infrared spectrometer (Nikolaite IS50, Thermo Fisher Scientific) equipped with a gold-plated integrating sphere (Parker Technology). The measured spectral response is in excellent agreement with the theoretical predictions, indicating that it represents the characteristics of a moderately humid atmosphere with a total precipitable water content of 3 cm. Specifically, as shown in the figure... Figure 8 As shown. Using this atmospheric simulation material as a standard atmosphere, the present invention can construct a cooling power characteristic curve that depicts the radiative cooling flux of any radiative cooling material under different operating temperatures and heat loads. Figure 8 (Left image) shows a comparison between the spectral emissivity (theoretical prediction, experimental measurement) of a simulated material of a moderately humid atmosphere and the spectral emissivity of a moderately humid atmosphere. For example... Figure 8 As shown, curve 802 represents the spectral radiance of a moderately humid atmosphere, curve 804 represents the theoretical spectral radiance of the atmospheric simulation material, and curve 806 represents the experimentally measured spectral emissivity of the atmospheric simulation material. The experimentally measured atmospheric simulation material is the material used in experimental setup 200.

[0107] Through calculation, Figure 9 In this study, two ideal radiation-cooling materials were considered (broadband / blackbody emitters and wavelength-selective / window emitters). Figure 9 The cooling power characteristic curves (showing the emissivity characteristics in the smaller figures) were evaluated. Figure 9 Curve 902 represents the cooling power characteristic curve of an ideal broadband transmitter, and curve 904 represents the cooling power characteristic curve of a wavelength-selective transmitter. The test environments included a moderate humidity atmosphere (total water vapor capacity = 3 cm³) and a simulated atmosphere. Using existing atmospheric simulation material films, the relatively low emissivity at shorter wavelengths introduced a systematic error. This is beneficial for broadband transmitters, with the total error remaining at 10 W / m² across all operating temperatures close to room temperature. 2 the following. Figure 9 This illustrates the calculation of radiative cooling power and the temperature difference between the sample and the air when assuming the use of a moderate humidity atmosphere to simulate the material (solid line) and a moderate humidity atmosphere (total water vapor capacity = 3 cm) (dashed line), using an ideal broadband emitter and a wavelength-selective emitter. T 试样 - T amb The relationship between ) Figure 9 The x-coordinate in the middle is Tsample - T amb It is the temperature difference between the radiative cooling material and the air. T sample for T 试样 , Figure 9 The small figure in the diagram shows the relationship between the emissivity and wavelength of broadband transmitters and wavelength-selective transmitters.

[0108] Figure 10 A physical diagram of the experimental apparatus for evaluating the performance of irradiated cooling materials according to the present invention is shown, wherein... Figure 10 The location of the radiation-cooling material in the experimental apparatus 200 of this invention is shown, with the sample of the radiation-cooling material facing the atmospheric simulation material 300. Below the radiation-cooling material sample is a heat sink 206. The entire experimental apparatus 200 is externally covered with an insulating layer for thermal insulation. A quartz window is installed at the top of the cover to allow normal solar radiation from a solar simulator (e.g., the Newport 94083A solar simulator) to enter. The entire inner top surface of the chamber is covered with a material with an area of ​​approximately A²≈2500 cm². 2 A thin film of atmospheric simulation material was constructed to simulate a moderate humidity environment. The temperature of the atmospheric simulation material, T2, was controlled by a heater. A black anodized aluminum foil (RoscoMatte) with an emissivity close to 1 was used as the inner bottom surface, acting as a heat sink 206, whose temperature T3 was regulated by a cryogenic circulating cooler. This experimental setup allows for the testing of the cooling characteristics of any radiatively cooled material under a standard simulated atmospheric environment. The current experimental setup limits the surface area of ​​the radiatively cooled material sample to a diameter of 10 cm, thus limiting the area of ​​the radiatively cooled material... 1 is much smaller than the area of ​​the simulated atmospheric material. 2 (i.e.) 1 2) Orient the radiation-cooled material sample toward the atmospheric simulation material. Use a sample holder to separate the radiation-cooled material sample from the experimental apparatus of this invention. For example... Figure 10 As shown, a Capton heating element 220 is located below the radiatively cooled material sample, enabling precise and independent control of the sample's temperature. A thin copper plate (i.e., a metal vapor chamber) is placed between the radiatively cooled material sample and the heater to ensure good thermal contact and improve the temperature uniformity of the sample's surface.

[0109] In some embodiments of the present invention, the experimental apparatus 200 includes at least one temperature sensor for measuring the temperature change of a radiation-cooled material sample. In some embodiments of the present invention, the temperature sensor is a thermocouple; in some embodiments of the present invention, at least one thermocouple is mounted on the back side of the radiation-cooled material sample for temperature measurement. In some embodiments of the present invention, the number of thermocouples is three. Figure 10 As shown, three thermocouples 232, 234, and 236 are mounted on the radiatively cooled material sample 202. Other types of temperature sensors can also be used in this experimental setup 200. The bottom of the heating element 220 and the sample tray are wrapped with highly reflective (low emissivity) aluminum foil to reduce radiative heat exchange. The pressure in chamber 208 is maintained at a vacuum below 1 psi to minimize conduction and convection losses. Therefore, the net radiative cooling power of the radiatively cooled material sample is equal to the resistance heating power generated by the Capton heating element 220.

[0110] It should be noted that the convection within the chamber is not completely eliminated; however, it is primarily affected by the temperature difference (pressure below 1 psi) between the radiatively cooled material sample and the surrounding air. This convection is mainly driven by the relatively low temperature of the surface of the cold source fins on the heat sink. To mitigate its effect, one approach is to increase the vacuum level of the chamber or to maintain a constant temperature difference. In some embodiments of the invention, the constant temperature difference between the radiatively cooled material sample and the surface of the cold source fins on the heat sink is approximately 20°C, remaining constant throughout the measurement process. This method further reduces and normalizes the effect of convection. Even if the operating temperature of the cold source fin surface varies, convection still exists between different measurements.

[0111] To conduct experiments on radiation-cooled materials within a closed experimental setup 200, two typical radiation-cooled materials were selected, and their characteristics were analyzed based on their different cooling capabilities: one is blackbody-type 502 (denoted as a broadband emitter, known for its high emissivity across the entire infrared band); the other is window-type 502 (denoted as a wavelength-selective emitter, renowned for its high emissivity within an atmospheric window). Samples of these two radiation-cooled materials are shown below. Figure 11 As shown in the illustrations, the blackbody-type 502 radiative cooling material sample consists of an aluminum substrate and a polyethylene terephthalate (PET, 0.2 mm thick) film disposed on a 30 μm thick aluminum substrate. The window-type 500 radiative cooling material sample includes a stacked reflective substrate layer and solution-derived SiO2. x N y Thin film layer and SiO2 particle layer, the solution-derived SiO x N yThe thin film layer is sandwiched between a reflective substrate and a layer of self-assembled SiO2 particles. (This spectrally selective / windowed cooling material is from C. Lin, Y. Li, Y. Kwon, J. Huang, Z. Wu, J. Zheng, G. Liu, C. Tso, C. Chao, B. Huang, A solution-processed inorganic emitter with high spectral selectivity for efficient subambient radiative cooling in hot humid climate.) Advanced Materials 34, 2109350 (2022). doi:10.1002 / adma.202109350). The full-band emissivity from ultraviolet to mid-infrared wavelengths of blackbody-type 502 radiative cooling material samples and window-type 500 radiative cooling material samples is shown in the figure. Figure 11 As shown in the left-hand image, Figure 11 The right side of the image shows physical images of a blackbody-type 502 radiation cooling material sample and a window-type 500 radiation cooling material sample. Figure 11 Curve 510 in the figure represents the full-band emissivity of the blackbody-type 502 radiation-cooling material sample, and curve 512 represents the full-band emissivity of the window-type 500 radiation-cooling material sample.

[0112] Example 5 This example provides a method for evaluating the performance of radiation-cooled materials (e.g., window-type or blackbody-type radiation-cooled materials), which can be performed using the experimental setup 200 of any of the above embodiments; the method includes the following steps: At least one temperature sensor is attached to the radiation-cooled material and then placed in the experimental apparatus for evaluating the performance of the radiation-cooled material as described in the above embodiment. The vacuum pressure inside the chamber of experimental apparatus 200 was reduced to less than 1 psi. The temperature of the radiative cooling material is measured, and then the cooling power is measured based on the temperature change. The performance of the radiative cooling material is determined based on the measured temperature and cooling power.

[0113] The performance of radiation-cooled materials can be determined by plotting a cooling power characteristic curve, which is the relationship between cooling power and ambient temperature, i.e., the curve showing how cooling power changes with ambient temperature. This cooling power characteristic curve indicates the cooling characteristics of the radiation-cooled material. Further details on using experimental setup 200 to evaluate the performance of radiation-cooled materials will be described below.

[0114] Without considering solar radiation, the overall radiative cooling power of broadband and wavelength-selective transmitters was first measured at night. This was achieved by keeping the temperature of the atmospheric simulated material film constant while varying the operating temperature of the radiatively cooled material samples (e.g., ...). Figure 12 As shown in the figure, the functional relationship between temperature difference and radiative cooling power was obtained. Figure 12 Curve 800 in the figure shows the cooling power characteristics of the broadband transmitter at night (without sunlight). Figure 12 The x-coordinate in the middle is T s -T ambient This refers to the temperature difference between the surface of the broadband transmitter and the ambient temperature; curve 802 shows the cooling power characteristics of the wavelength-selective transmitter at night (no sun); curve 804 shows the cooling power characteristics of the broadband transmitter during the day (e.g., when the solar simulator is on); curve 806 shows the cooling power characteristics of the wavelength-selective transmitter during the day (e.g., when the solar simulator is on). Figure 12 It can be seen that, under nighttime conditions, both broadband and wavelength-selective transmitters have a cooling effect across the entire operating temperature range. This is true when the surface temperature of the radiative cooling material is equal to or higher than the atmospheric temperature. T 1≥ T 2 ( T amb At this point, the net radiative cooling power of a broadband transmitter is higher than that of a wavelength-selective transmitter. However, the slope of this cooling power characteristic curve is flatter for window-type transmitters, making them better suited for achieving lower surface temperatures below ambient temperature. For both types of transmitters, according to Figure 12 The results showed that the measured cooling power differed from the actual value by approximately 10 W / m under all conditions. 2 Although the absolute error is low, the atmospheric simulation film used here exhibits systematic errors, which benefit broadband transmitters due to its reduced emissivity in the 6–8 μm range. Theoretical predictions based on radiative heat transfer between a moderately humid atmosphere, radiatively cooled material samples, and the cold universe have also been calculated and plotted (solid line) for comparison, showing a high degree of agreement between theoretical predictions and measured values. The atmospheric simulation material film used in this independent, thermally isolated experimental setup 200 captures all the key elements of the radiative cooling process, phenomena previously only observable in open, sky-accessible outdoor environments.

[0115] The daytime radiative cooling characteristics under different solar radiation intensities can be evaluated using solar simulator 212. Figure 12The effects of radiative cooling are illustrated. Characteristic curves for blackbody and window-type radiatively cooled materials are presented under a simulated solar irradiance of 0.8 solar masses. Vertical incidence of solar radiation corresponds to a solar elevation angle of 90°. Under such solar irradiance, the corresponding error is significantly reduced, accounting for less than 5% of the total solar absorption of the radiatively cooled material sample. This error primarily stems from measurement instabilities related to the solar simulator. The wavelength-selective emitter used here exhibits good radiative cooling performance even at high temperatures, with an average emissivity (7.3%) across the solar spectrum lower than that of the broadband emitter used here (22.6%). This phenomenon is particularly pronounced under high solar irradiance. Figure 12 As shown, wavelength-selective transmitters maintain cooling performance even at temperatures above ambient, while broadband transmitters lack cooling performance across the entire temperature range studied due to their high solar absorptivity.

[0116] Another important factor affecting radiative cooling performance in practical applications is non-radiative heat transfer, including conduction and convection. By... '' 传导+对流 The h(Ts-Tamb) factor calculation was incorporated into the radiative cooling power obtained from the above experimental measurements, and the influence of these factors was studied. Figure 13 This demonstrates wavelength-selective samples with a nonradiative heat transfer coefficient h = 0 W / (m²) K), 6W / (m²) K), 12W / (m²) K), 20W / (m²) Net cooling power at K), Figure 13 The x-coordinate in the middle is T s -T ambient This refers to the temperature difference between the surface of the wavelength-selective sample and the ambient temperature. As predicted by the second law of thermodynamics, cooling performance improves when operating at temperatures above ambient, and decreases when the sample's operating temperature is below ambient. Therefore, as the heat transfer coefficient increases, the sub-ambient equilibrium temperature of the sample at zero cooling power gradually approaches the ambient temperature.

[0117] Experimental data shows that a 50 μm thick polymer photonics film can effectively simulate the spectral and radiative thermal responses of a 100 km thick atmosphere. This atmospheric simulation material can be used in laboratory environments to simulate the behavior and properties of a 100 km thick atmosphere. This atmospheric simulation material 300 can replicate the radiative heat transfer between radiatively cooled materials and the atmosphere. It provides a standard procedure and apparatus for comparing various radiatively cooled materials under controlled atmospheric conditions. This development not only accelerates the development process and widely adopts passive cooling technology, but also opens new avenues for studying the optical and thermal properties of the entire atmosphere in laboratory environments.

[0118] This experimental setup offers numerous advantages because it employs atmospheric simulation materials. These materials can simulate atmospheric conditions in a laboratory environment, enabling the evaluation of radiative cooling materials. By mimicking the spectrum of the actual atmosphere, they can replicate spectral radiative heat transfer, providing a significant advantage in evaluating the performance of radiative cooling materials because it can be operated under controlled conditions in a laboratory setting. This approach allows for iterative comparisons of various types of radiative cooling materials to determine their performance.

[0119] The experimental setup 200 described above offers numerous advantages because it employs atmospheric simulation materials capable of mimicking atmospheric behavior in a laboratory environment. The setup also allows for the adjustment of one or more parameters, such as solar radiation intensity. These parameters can be easily varied to simulate multiple day / night conditions or different atmospheric conditions. Furthermore, the setup can reproduce the same conditions to evaluate the performance of various radiation-cooling materials, providing a controlled environment for repeatable experiments, unlike experiments conducted in external environments where precise control is impossible. This setup 200 offers a compact laboratory layout, enabling users to precisely control parameters within a laboratory environment, thus improving ease of use and allowing users to test multiple radiation-cooling materials in a simple, easy-to-use, and controlled environment. The experimental setup and methods described above offer numerous advantages because they enable a standardized approach to evaluating the performance of radiation-cooling materials, providing an easy-to-use tool for calibrating radiation-cooling performance.

[0120] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An atmospheric simulation material, characterized by: It includes a stacked metal substrate layer and a polymer thin film layer; the polymer thin film layer contains a polymer and spectral resonant microparticles; the spectral resonant microparticles are distributed in the polymer thin film layer; The spectral resonance particles include ilmenite particles.

2. The atmospheric layer simulation material of claim 1, wherein: The spectral resonance microparticles also include nitrate particles; preferably, with the total volume of the polymer film layer as 1, the volume fraction of the polymer is 0.85~0.885, the volume fraction of the ilmenite particles is 0.07~0.1, and the volume fraction of the nitrate particles is 0.045~0.

05.

3. The atmospheric layer simulation material of claim 1, wherein: With the total volume of the polymer film layer as 1, the volume fraction of the polymer is 0.9~0.93, and the volume fraction of the ilmenite particles is 0.07~0.

1.

4. The atmospheric layer simulation material according to claim 1 or 2, characterized by: The average particle size of the ilmenite particles is 0.1~10μm; And / or, the average particle size of the nitrate particles is 0.1~10 μm; And / or, the material of the ilmenite particles is FeTiO3; And / or, the material of the nitrate particles includes at least one of sodium nitrate, potassium nitrate, and ammonium nitrate; And / or, the polymer includes at least one of polyethylene, polypropylene, polycarbonate, and polyurethane; And / or, the thickness of the polymer film layer is 30~200μm; And / or, the material of the metal substrate layer includes at least one of aluminum foil, copper foil, and tin foil.

5. An experimental apparatus for evaluating the cooling performance of a radiative cooling material, characterized by: It includes a heat sink and a cover; the cover and the heat sink are arranged to form a cavity; the material of the cover is the atmospheric simulation material according to any one of claims 1 to 4; the polymer film layer in the atmospheric simulation material is disposed along the side close to the heat sink.

6. The experimental setup for evaluating the cooling performance of a radiative cooling material according to claim 5, wherein: The experimental apparatus further includes a transparent window and a solar simulator; the transparent window is disposed on the cover; the solar simulator is used to allow the light emitted by it to enter the cavity through the transparent window; And / or, the experimental apparatus further includes a sample rack; the sample rack is disposed on the heat sink and located within the chamber; the sample rack is used to hold radiation-cooling material; And / or, the experimental apparatus further includes a fluid channel; the fluid channel is disposed on the heat sink; And / or, the experimental apparatus further includes a heater for heating the cover; And / or, the experimental apparatus further includes a cooler; the cooler is used to control the temperature of the heat sink; And / or, the experimental apparatus further includes a heating unit and a metal heat exchanger; the heating unit is provided with a metal heat exchanger, and the radiation cooling material is placed on the metal heat exchanger; And / or, the experimental apparatus further includes at least one temperature sensor for monitoring the temperature of at least one selected from the cover, heat sink, and radiative cooling material.

7. The experimental setup for evaluating the cooling performance of a radiative cooling material according to claim 5, wherein: The heat sink is made of black anodized aluminum. And / or, the emissivity of the heat sink is 0.9~1.

0.

8. The experimental setup for evaluating the cooling performance of a radiative cooling material according to claim 6, wherein: The area of ​​the atmospheric simulation material is the same as the area of ​​the heat sink; And / or, the ratio of the area of ​​the radiation cooling material to the area of ​​the atmospheric simulation material is 0.01-0.

05.

9. A method for evaluating the cooling performance of a radiative cooling material, characterized by: Includes the following steps: A temperature sensor is mounted on the radiative cooling material and then placed in the chamber of the experimental apparatus for evaluating the cooling performance of the radiative cooling material as described in any one of claims 5 to 8; A vacuum is drawn, and then the temperature and cooling power of the radiation cooling material are measured. Based on the measured temperature and cooling power, a curve showing the relationship between cooling power and ambient temperature is plotted to obtain the cooling performance of the radiation cooling material.

10. The application of the atmospheric simulation material according to any one of claims 1 to 4, the experimental apparatus for evaluating the cooling performance of radiative cooling materials according to any one of claims 5 to 8, or the method for evaluating the cooling performance of radiative cooling materials according to claim 9, in the field of performance testing of radiative cooling materials.

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