Suction air cooling device for air conditioner outdoor units and method for cooling air conditioner outdoor units with suction air

Abstract

To provide a suction air cooling device for an air-conditioning outdoor unit that allows for an increased cooling capacity in periods of elevated temperatures like summer.SOLUTION: A suction air cooling device for air-conditioning outdoor units has a radiation cooling film W attached thereto in a cooling action state to cool the air sucked into an air-conditioning outdoor unit K.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an air intake cooling device for an air conditioning outdoor unit that cools the intake air drawn into the air conditioning outdoor unit, and to an air intake cooling method for an air conditioning outdoor unit that cools the intake air drawn into the air conditioning outdoor unit. [Background technology]

[0002] In an air conditioning system that uses a heat pump cycle to perform both cooling and heating operations, the outdoor unit is installed outside the building. During cooling operations, it releases heat into the outside air, and during heating operations, it absorbs heat from the outside air. Air conditioning outdoor units are sometimes installed in locations facing south on a building. When an air conditioning outdoor unit is installed in such a location facing south, the air in the space where the unit is installed tends to become hotter, even in winter, due to direct or indirect heating by sunlight. As a result, the air drawn into the air conditioning outdoor unit during cold winter months becomes as hot as possible, making it easier to improve heating capacity.

[0003] However, if an air conditioner's outdoor unit is installed facing south, during hot periods such as summer, the air in the space where the unit is installed will become hot due to direct or indirect heating by sunlight, leading to a decrease in cooling capacity.

[0004] For this reason, some air conditioner outdoor units are equipped with a sunshade member to cover the installation space (see, for example, Patent Document 1). Incidentally, Patent Document 1 describes providing a solar power generation unit on the upper part of the sunshade member. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2002-76407 [Overview of the project] [Problems that the invention aims to solve]

[0006] Conventionally, while sunshade components were installed to cover the space where the air conditioner's outdoor unit was installed, simply installing sunshade components was insufficient to adequately cool the air in the space where the air conditioner's outdoor unit was installed during high temperatures such as in summer. As a result, the air drawn into the air conditioner's outdoor unit became hot, making it difficult to improve the cooling capacity.

[0007] Incidentally, during cold periods such as winter, it is conceivable to remove the sunshade component to raise the temperature of the air in the space where the air conditioning outdoor unit is installed. However, if a solar power generation unit is installed on top of the sunshade component, the sunshade component will remain attached even during cold periods such as winter without being removed.

[0008] The present invention has been made in view of the above circumstances, and its purpose is to provide an air intake cooling device for an air conditioner outdoor unit and an air intake cooling method for an air conditioner outdoor unit that can improve cooling capacity during high temperatures such as in summer. [Means for solving the problem]

[0009] The characteristic configuration of the suction air cooling device for air conditioner outdoor units of the present invention is that a radiant cooling film is installed in a cooling state to cool the suction air drawn into the air conditioner outdoor unit. The radiative cooling film is mounted in a manner that allows switching between the cooling action state and the cooling stop state in which the intake air is not cooled. , A transparent heat-insulating sheet is provided to cover the upper part of the installation space for the outdoor unit of the air conditioner, and the radiative cooling film covers the upper part of the transparent heat-insulating sheet when the cooling is in operation, and opens the upper part of the transparent heat-insulating sheet when the cooling is stopped. It's at a single point.

[0010] In other words, A transparent heat-insulating sheet is provided to cover the upper part of the space where the air conditioner outdoor unit is installed. Radiative cooling film , covering the top of the transparent heat-insulating sheet in the cooling state Because it is attached to the condition, During high temperatures such as in summer, the radiative cooling film cools the transparent heat-insulating sheet, which in turn cools the outside air located below the sheet, thereby cooling the intake air drawn into the air conditioning outdoor unit. Even if the air conditioner's outdoor unit is installed facing south, the air drawn into the unit will be at a lower temperature, resulting in improved cooling capacity during hot periods such as summer. Furthermore, during low temperatures such as in winter, by stopping the cooling of the radiative cooling membrane so that it does not cool the intake air drawn into the outdoor unit of the air conditioner, it is possible to suppress the intake air being drawn into the outdoor unit of the air conditioner from becoming unnecessarily cold, thereby improving heating capacity. In particular, if the air conditioning outdoor unit is installed facing south on the building, the outside air in the space where the unit is installed tends to become hotter even in cold weather such as winter due to direct or indirect heating by sunlight, thus allowing for an appropriate improvement in heating capacity. Furthermore, when the cooling is stopped, the radiative cooling membrane opens up the top of the transparent heat-insulating sheet that covers the upper part of the installation space of the outdoor unit of the air conditioner. Therefore, if the outdoor unit of the air conditioner is installed in a location facing south on the building, sunlight will irradiate the transparent heat-insulating sheet, causing the outside air located below the sheet to reach an appropriate temperature. This will also raise the temperature of the intake air drawn into the outdoor unit of the air conditioner, thereby further improving the heating capacity.

[0011] Radiative cooling refers to the phenomenon in which a substance emits electromagnetic waves such as infrared rays to the surroundings and its temperature decreases. By utilizing this phenomenon, for example, it is possible to cool a cooling target without consuming energy such as electricity. That is, the radiative cooling film emits electromagnetic waves such as infrared rays to the outside (for example, the sky), and as a result, its temperature decreases. Consequently, during high-temperature periods such as summer, the suction air drawn into the outdoor unit of the air conditioner is cooled, improving the cooling capacity.

[0012] In short, according to the suction air cooling device for an outdoor unit of an air conditioner of the present invention, the cooling capacity is improved during high-temperature periods such as summer. This allows for improved heating capacity during low-temperature periods such as winter. .

[0017] A further characteristic configuration of the suction air cooling device for an outdoor unit of an air conditioner of the present invention is that the radiative cooling film is mounted in a state of covering the upper part of the installation space of the outdoor unit of the air conditioner.

[0018] That is, since the radiative cooling film is mounted in a state of covering the upper part of the installation space of the outdoor unit of the air conditioner, by cooling the outside air in the installation space of the outdoor unit of the air conditioner, the suction air drawn into the outdoor unit of the air conditioner can be cooled, improving the cooling capacity.

[0019] That is, with a simple configuration of mounting the radiative cooling film in a state of covering the upper part of the installation space of the outdoor unit of the air conditioner, the suction air drawn into the outdoor unit of the air conditioner can be cooled, improving the cooling capacity.

[0020] In short, according to a further characteristic configuration of the suction air cooling device for an outdoor unit of an air conditioner of the present invention, the cooling capacity can be improved with a simple configuration.

[0033] A further characteristic configuration of the suction air cooling device for an outdoor unit of an air conditioner of the present invention is that the radiative cooling film includes a radiative cooling layer. The radiative cooling layer is configured in a form that includes an infrared radiation layer that emits infrared light from a radiation surface, and a light reflection layer that is positioned on the side opposite to the side where the radiation surface exists in the infrared radiation layer. The infrared radiation layer is a resin material layer made of a polyvinyl chloride resin whose thickness is adjusted to emit thermal radiation energy greater than the absorbed solar energy in the wavelength band from 8 μm to 14 μm. The key feature is that the aforementioned light-reflecting layer comprises silver or a silver alloy. The vinyl chloride resin used in the present invention is a homopolymer of vinyl chloride or vinylidene chloride, and a copolymer of vinyl chloride or vinylidene chloride, and is manufactured by conventionally known polymerization methods.

[0034] In other words, sunlight incident from the radiating surface of the infrared radiating layer in the radiative cooling layer passes through the resin material layer, is reflected by the light-reflecting layer on the opposite side of the resin material layer from the radiating surface, and escapes from the radiating surface to the outside of the system. In this specification, when the term "light" is used, the concept of light includes ultraviolet light, visible light, and infrared light. When these are described in terms of wavelengths of light as electromagnetic waves, they include electromagnetic waves with wavelengths ranging from 10 nm to 20,000 nm (electromagnetic waves from 0.01 μm to 20 μm).

[0035] Furthermore, heat transfer (heat input) to the radiative cooling layer is converted into infrared radiation by the resin material layer acting as an infrared radiation layer, and then released from the radiating surface to the outside of the system. In this way, the radiative cooling layer can reflect sunlight that irradiates it, and can also radiate heat transferred to the radiative cooling layer (for example, heat transferred from the atmosphere or heat transferred from the film material that the radiative cooling layer cools) out of the system as infrared light.

[0036] Furthermore, the resin material layer made of polyvinyl chloride resin is adjusted to a thickness that emits greater thermal radiation energy than the absorbed solar energy in the wavelength band of 8 μm to 14 μm (the atmospheric window region). Therefore, by appropriately reflecting sunlight with a light-reflecting layer containing silver or a silver alloy, the cooling function can be exerted even in daytime solar radiation conditions.

[0037] Therefore, even under daytime sunlight conditions, the radiative cooling effect of the radiative cooling layer can cool the intake air drawn into the outdoor unit of the air conditioner.

[0038] Incidentally, as mentioned above, polyvinyl chloride resin provides sufficient thermal radiation in the window region of the atmosphere, and is considerably cheaper than fluororesin or silicone rubber, which provide similar thermal radiation. Therefore, it is advantageous for inexpensively constructing radiative cooling films that cool below ambient temperature under direct sunlight.

[0039] Furthermore, thin-film polyvinyl chloride resins become flexible when plasticizers are added, allowing them to change shape flexibly to conform to other objects that come into contact with them, thus avoiding damage and maintaining their beautiful appearance for a long period of time. In contrast, thin-film fluororesins are rigid, so they cannot change shape flexibly when in contact with other objects, making them easily scratched and difficult to maintain in a beautiful condition.

[0040] Furthermore, by adding plasticizers, polyvinyl chloride resins can deform and smooth out surface scratches when heated to over 80°C, effectively self-repairing damage. Fluoropolymers and silicone rubber do not possess this property. This characteristic of flexible polyvinyl chloride resins allows them to maintain a clean appearance for extended periods, which in turn contributes to the long-term maintenance of radiative cooling performance.

[0041] Furthermore, since polyvinyl chloride resins are flame-retardant and resistant to biodegradation, they are suitable as resin materials for forming the infrared radiation layer of radiative cooling films used outdoors. Furthermore, in addition to the flexibility of the thin film-like polyvinyl chloride resin, the polyvinyl chloride resin is softened by the addition of plasticizers, which further enhances the flexibility of the resin material layer, resulting in a flexible radiative cooling film.

[0042] In short, according to the further characteristic configuration of the suction air cooling device for air conditioning outdoor units of the present invention, the air drawn into the air conditioning outdoor unit can be cooled by radiative cooling in daytime solar radiation conditions.

[0043] A further characteristic configuration of the suction air cooling device for an air conditioning outdoor unit of the present invention is that the thickness of the resin material layer is The material is designed to have a thickness that provides optical absorption characteristics such as a wavelength-average light absorption rate of 13% or less from 0.4 μm to 0.5 μm, a wavelength-average light absorption rate of 4% or less from 0.5 μm to 0.8 μm, a wavelength-average light absorption rate of 1% or less from 0.8 μm to 1.5 μm, and a wavelength-average light absorption rate of 40% or less from 1.5 μm to 2.5 μm, while also providing thermal radiation characteristics with a wavelength-average emissivity of 40% or more from 8 μm to 14 μm.

[0044] Furthermore, the wavelength-averaged light absorptivity from 0.4 μm to 0.5 μm refers to the average value of the light absorptivity for each wavelength in the range of 0.4 μm to 0.5 μm, and the same applies to the wavelength-averaged light absorptivity from 0.5 μm to 0.8 μm, from 0.8 μm to 1.5 μm, and from 1.5 μm to 2.5 μm. Other similar descriptions, including emissivity, also refer to similar average values, and the same applies hereafter in this specification.

[0045] In other words, the light absorption rate and emissivity (photoluminescence) of the resin material layer change depending on its thickness. Therefore, it is necessary to adjust the thickness of the resin material layer so that it absorbs as little sunlight as possible and emits a large amount of thermal radiation in the wavelength range of the so-called atmospheric window (the region of light wavelengths from 8 μm to 14 μm).

[0046] Specifically, in terms of the light absorption rate (light absorption characteristics) of sunlight in the resin material layer, the wavelength average of the light absorption rate from 0.4 μm to 0.5 μm must be 13% or less, the wavelength average of the light absorption rate from 0.5 μm to 0.8 μm must be 4% or less, the wavelength average of the light absorption rate from 0.8 μm to 1.5 μm must be 1% or less, and the wavelength average of the light absorption rate from 1.5 μm to 2.5 μm must be 40% or less. For light absorption from 2.5 μm to 4 μm, the wavelength average only needs to be 100% or less. When light absorption rates are distributed in this manner, the light absorption rate of sunlight becomes 10% or less, which translates to an energy of 100W or less.

[0047] In other words, the light absorption rate of sunlight increases as the thickness of the resin material layer increases. When the resin material layer is made thick, the emissivity of the atmospheric window becomes almost 1, and the thermal radiation emitted into space at that time is 125 W / m 2 From 160W / m 2 This is the result. The light-reflecting layer absorbs sunlight at 50 W / m². 2 The following is preferable: Therefore, the sum of the solar absorption in the resin material layer and the light-reflecting layer is 150 W / m². 2 The following conditions apply, and cooling will proceed if atmospheric conditions are favorable. For the resin material layer, it is best to use one with low absorption near the peak values ​​of the solar spectrum, as described above.

[0048] Furthermore, from the perspective of the emissivity (thermal radiation characteristics) of the resin material layer emitting infrared light, the wavelength average of the emissivity from 8 μm to 14 μm must be 40% or higher. In other words, 50 W / m² is absorbed by the light-reflecting layer. 2 In order for a certain amount of solar thermal radiation to be emitted from the resin material layer into space, the resin material layer needs to emit even more thermal radiation than that. For example, when the ambient temperature is 30°C, the maximum thermal radiation through an atmospheric window with wavelengths from 8 μm to 14 μm is 200 W / m². 2 This value is obtained (calculated assuming an emissivity of 1). This value is obtained in clear skies in dry environments with thin air, such as high mountains. In lowlands, the thickness of the atmosphere is greater than in high mountains, so the wavelength range of the atmospheric window narrows, and the transmittance decreases. Incidentally, this is called "the atmospheric window narrowing."

[0049] Furthermore, the environment in which air conditioning outdoor units are actually used, that is, the environment in which radiative cooling membranes are used, is often humid, and in that case the atmospheric window also narrows. When used in low-lying areas, the thermal radiation generated in the atmospheric window area is 160 W / m² at 30°C under ideal conditions. 2 This is the estimated value (calculated assuming an emissivity of 1). Also, although it is common in Japan, when there is haze in the sky or when smog exists, the atmospheric window becomes even narrower, and the radiation to space is on the order of 125 W / m 2 or less.

[0050] In view of such circumstances, the wavelength average of the emissivity from 8 μm to 14 μm must be 40% or more (the thermal radiation intensity in the atmospheric window band is 50 W / m 2 or more) in order to be used in lowlands in the mid-latitude zone. Therefore, by adjusting the thickness of the resin material layer to be within the range of the above-described optical specifications, the heat dissipation in the atmospheric window becomes larger than the heat input due to the light absorption of sunlight, and it becomes possible to perform radiative cooling outdoors even in a daytime solar radiation environment. That is, when the resin material layer is formed of a vinyl chloride-based resin, the thickness of the resin material layer is preferably 100 μm or less and 10 μm or more.

[0051] In short, according to a further characteristic configuration of the suction air cooling device for an air conditioner outdoor unit of the present invention, the heat dissipation in the atmospheric window becomes larger than the heat input due to the light absorption of sunlight, and the suction air sucked into the air conditioner outdoor unit can be appropriately cooled even in a solar radiation environment.

[0052] A further characteristic configuration of the suction air cooling device for an air conditioner outdoor unit of the present invention is that the light reflection layer has a reflectance of 90% or more at a wavelength of 0.4 μm to 0.5 μm and a reflectance of 96% or more at a wavelength longer than 0.5 μm.

[0053] That is, the solar spectrum exists from a wavelength of 0.295 μm to 4 μm, and as the wavelength increases from 0.4 μm, the intensity increases, and particularly the intensity from a wavelength of 0.5 μm to a wavelength of 2.5 μm is large. When the light reflection layer exhibits a reflectance of 90% or more from a wavelength of 0.4 μm to 0.5 μm and a reflectance of 96% or more at a wavelength longer than 0.5 μm, the light reflection layer absorbs only about 5% or less of the solar energy.

[0054] As a result, during the summer, at midday, the light-reflecting layer absorbs 50 W / m² of solar energy. 2 This can be kept below a certain level, allowing for effective radiative cooling by the resin material layer. In this specification, unless otherwise specified, the spectrum of sunlight shall conform to the AM1.5G standard.

[0055] In short, according to the further characteristic configuration of the suction air cooling device for air conditioning outdoor units of the present invention, the absorption of solar energy by the light-reflecting layer is suppressed, and radiative cooling by the resin material layer can be performed effectively.

[0056] A further characteristic feature of the suction air cooling device for air conditioning outdoor units of the present invention is that the light-reflecting layer is made of silver or a silver alloy and has a thickness of 50 nm or more.

[0057] In other words, in order to give the light-reflecting layer the above-mentioned reflectivity characteristics, that is, reflectivity of 90% or more at wavelengths of 0.4 μm to 0.5 μm and reflectivity of 96% or more at wavelengths longer than 0.5 μm, the reflective material on the radiating surface side of the light-reflecting layer must be silver or a silver alloy. Furthermore, when reflecting sunlight using only silver or a silver alloy while maintaining the aforementioned reflectivity characteristics, a thickness of 50 nm or more is required.

[0058] In short, according to the further characteristic configuration of the suction air cooling device for air conditioning outdoor units of the present invention, the absorption of solar energy by the light-reflecting layer can be effectively suppressed, and radiative cooling by the resin material layer can be performed effectively.

[0059] A further characteristic feature of the suction air cooling device for air conditioning outdoor units of the present invention is that the light-reflecting layer has a laminated structure of silver or a silver alloy and aluminum or an aluminum alloy located on the side away from the resin material layer.

[0060] In other words, in order to give the light-reflecting layer the aforementioned reflectivity characteristics, a structure in which silver or a silver alloy and aluminum or an aluminum alloy are laminated may be used. In this case as well, the reflective material on the radiating surface side must be silver or a silver alloy. In this case, the thickness of the silver must be 10 nm or more, and the thickness of the aluminum must be 30 nm or more.

[0061] Furthermore, since aluminum or aluminum alloys are cheaper than silver or silver alloys, it is possible to reduce the cost of the light-reflecting layer while maintaining appropriate reflectivity characteristics. In other words, by thinning expensive silver or silver alloy to reduce the cost of the light-reflecting layer, and by creating a laminated structure of silver or silver alloy and aluminum or aluminum alloy in the light-reflecting layer, it is possible to reduce the cost of the light-reflecting layer while maintaining appropriate reflectivity characteristics.

[0062] In short, according to the further characteristic configuration of the suction air cooling device for air conditioning outdoor units of the present invention, it is possible to reduce the cost of the light reflective layer while maintaining appropriate reflectivity characteristics.

[0063] A further characteristic configuration of the suction air cooling device for air conditioning outdoor units of the present invention is that the resin material forming the resin material layer is a vinyl chloride resin mixed with a plasticizer. The key feature is that the plasticizer consists of one or more compounds selected from the group consisting of phthalates, aliphatic dibasic acid esters, and phosphate esters.

[0064] In other words, as mentioned above, thin-film polyvinyl chloride resins become flexible when plasticizers are added, so they can avoid being damaged by contact with other objects by flexibly changing shape to conform to those objects, thus maintaining their beautiful appearance for a long period of time. Incidentally, thin-film fluororesins are rigid, so they cannot flexibly change shape when contacted with other objects, making them easily damaged and difficult to maintain their beautiful appearance. Incidentally, by mixing a plasticizer into the vinyl chloride resin in an amount of 1 part by weight to 200 parts by weight per 100 parts by weight of the vinyl chloride resin, the vinyl chloride resin can be given appropriate flexibility.

[0065] Furthermore, by adding plasticizers to polyvinyl chloride resin, as mentioned above, even if it gets scratched, heating it to over 80°C will deform it and smooth out the surface scratches, meaning it can self-repair. Fluoropolymers and silicone rubber do not possess this property. This property of polyvinyl chloride resin allows it to maintain a clean appearance for a long period of time. This contributes to maintaining long-term radiative cooling performance.

[0066] Furthermore, since the plasticizer mixed into the vinyl chloride resin consists of one or more compounds selected from the group consisting of phthalates, aliphatic dibasic acids, and phosphate esters, the plasticizer is less likely to absorb ultraviolet light (ultraviolet light with wavelengths from 295 nm to 400 nm) contained in sunlight, thus improving the weather resistance of the vinyl chloride resin mixed with the plasticizer. In other words, when a plasticizer mixed into a polyvinyl chloride resin absorbs ultraviolet light, hydrolysis of the plasticizer progresses, resulting in the polyvinyl chloride resin undergoing dehydrochlorination and other processes, causing discoloration (brown color) and potentially reducing its mechanical strength. However, by making the plasticizer less likely to absorb ultraviolet light contained in sunlight, the weather resistance of the polyvinyl chloride resin mixed with the plasticizer can be improved.

[0067] In short, according to the further characteristic configuration of the suction air cooling device for air conditioning outdoor units of the present invention, radiative cooling performance can be maintained over a long period of time, and weather resistance can be improved.

[0068] A further characteristic configuration of the suction air cooling device for an air conditioning outdoor unit of the present invention is that it is configured to include a protective layer between the infrared radiation layer and the light reflection layer. The protective layer is made of a polyolefin resin with a thickness of 300 nm or more and a thickness of 40 μm or less, or a polyethylene terephthalate resin with a thickness of 17 μm or more and a thickness of 40 μm or less.

[0069] In other words, sunlight incident on the radiating surface of the resin material layer, which acts as an infrared radiation layer, passes through the resin material layer and the protective layer, and is then reflected by the light-reflecting layer on the opposite side of the radiating surface of the resin material layer, and escapes from the radiating surface to the outside of the system.

[0070] Furthermore, since the protective layer is formed of polyolefin resin with a thickness of 300 nm or more and a thickness of 40 μm or less, or ethylene terephthalate resin with a thickness of 17 μm or more and a thickness of 40 μm or less, discoloration of the silver or silver alloy in the light-reflecting layer can be suppressed even in daytime sunlight conditions. This allows the cooling function to be effectively performed even in daytime sunlight conditions while appropriately reflecting sunlight with the light-reflecting layer.

[0071] In other words, if a protective layer is not present, radicals generated in the resin material layer may reach the silver or silver alloy forming the light-reflecting layer, or moisture permeating the resin material layer may reach the silver or silver alloy forming the light-reflecting layer, potentially causing the silver or silver alloy in the light-reflecting layer to discolor in a short period of time and failing to properly perform its light-reflecting function. However, the presence of a protective layer can suppress the discoloration of the silver or silver alloy in the light-reflecting layer in a short period of time.

[0072] An explanation will be provided regarding how the protective layer suppresses the discoloration of the silver or silver alloy in the light-reflecting layer. When the protective layer is formed from a polyolefin resin with a thickness of 300 nm or more and a thickness of 40 μm or less, the polyolefin resin is a synthetic resin in which the light absorption rate of ultraviolet rays is 10% or less across the entire ultraviolet wavelength range from 0.295 μm to 0.4 μm. Therefore, the protective layer is less likely to deteriorate due to ultraviolet absorption.

[0073] Furthermore, since the thickness of the polyolefin resin forming the protective layer is 300 nm or more, it effectively blocks radicals generated in the resin material layer from reaching the silver or silver alloy forming the light-reflecting layer, and also blocks moisture that permeates the resin material layer from reaching the silver or silver alloy forming the light-reflecting layer. As a result, discoloration of the silver or silver alloy forming the light-reflecting layer can be suppressed.

[0074] In other words, the protective layer formed from polyolefin resin degrades by absorbing ultraviolet light, forming radicals on the surface side away from the reflective layer. However, because its thickness is 300 nm or more, the formed radicals do not reach the light reflective layer. Furthermore, even if degradation occurs while forming radicals, the rate of degradation is slow due to the low absorption of ultraviolet light, thus allowing the aforementioned blocking function to be maintained over a long period.

[0075] When the protective layer is formed from ethylene terephthalate resin with a thickness of 17 μm or more and a form of 40 μm or less, ethylene terephthalate resin is a resin material that has a higher ultraviolet light absorption rate than polyolefin resins in the ultraviolet wavelength range of 0.295 μm to 0.4 μm. However, because the thickness is 17 μm or more, it effectively blocks radicals generated in the resin material layer from reaching the silver or silver alloy forming the light-reflecting layer, and also blocks moisture that penetrates the resin material layer from reaching the silver or silver alloy forming the light-reflecting layer. As a result, it effectively exhibits these blocking functions over a long period of time, thereby suppressing discoloration of the silver or silver alloy forming the protective layer.

[0076] In other words, the protective layer formed from ethylene terephthalate resin degrades by absorbing ultraviolet light, forming radicals on the surface side away from the reflective layer. However, because its thickness is 17 μm or more, the formed radicals do not reach the reflective layer. Furthermore, even if degradation occurs while forming radicals, the thickness of 17 μm or more ensures that the aforementioned shielding function is maintained over a long period of time.

[0077] Furthermore, when forming a protective layer with polyolefin resin and ethylene terephthalate resin, the reason for setting an upper limit on its thickness is to avoid, as much as possible, the protective layer exhibiting insulating properties that do not contribute to radiative cooling. In other words, the thicker the protective layer, the more insulating properties it exhibits that do not contribute to radiative cooling. Therefore, an upper limit on the thickness is set to ensure that the protective layer functions properly while avoiding, as much as possible, the insulating properties that do not contribute to radiative cooling.

[0078] In short, according to the further characteristic configuration of the suction air cooling device for air conditioning outdoor units of the present invention, effective cooling can be achieved while suppressing discoloration of the silver or silver alloy of the light-reflecting layer in a short period of time.

[0079] A further characteristic feature of the suction air cooling device for an air conditioning outdoor unit of the present invention is that the radiant cooling membrane comprises a membrane material and a radiant cooling layer, and the radiant cooling layer is attached to the outer surface of the membrane material by a connecting layer of adhesive or bonding agent.

[0080] In other words, the radiative cooling layer can be precisely attached to the outer surface of the flexible film material using an adhesive or bonding layer. Incidentally, the outer surface of the film material is generally not mirror-like, but rather formed with irregularities. However, since the radiative cooling layer is connected to the outer surface of the film material with an adhesive or bonding layer, the reflection of the irregularities on the outer surface of the film material on the light-reflecting layer is suppressed, and the light-reflecting layer can be maintained in a flat state.

[0081] In other words, when the surface irregularities of the film material are reflected in the light-reflecting layer, the light scattering caused by these irregularities reduces the reflectivity of the light-reflecting layer, resulting in the undesirable condition of light absorption. However, by maintaining the light-reflecting layer in a flat state, the decrease in the reflectivity of the light-reflecting layer can be suppressed.

[0082] In short, according to the further characteristic configuration of the suction air cooling device for air conditioning outdoor units of the present invention, the radiative cooling layer can be precisely attached to the outer surface of the flexible membrane material in close contact with it.

[0083] A further characteristic feature of the suction air cooling device for air conditioning outdoor units of the present invention is that the back surface of the membrane material, which is separated from the radiative cooling layer, is provided with a membrane material side resin layer made of a polyvinyl chloride resin.

[0084] In other words, in addition to the resin material layer being formed from a polyvinyl chloride resin, a resin layer on the back side of the film material that is separated from the radiative cooling layer is also provided, so when joining a pair of radiative cooling film materials, the resin layer on the film side of one radiative cooling film material can be brought into contact with the resin material layer of the other radiative cooling film material and joined by thermal bonding. This improves productivity when joining multiple radiative cooling films to form a canvas-like structure.

[0085] In other words, when joining multiple radiative cooling films to form a canvas-like structure, the films are joined by, for example, joining the edges of rectangular films. While sewing would be a time-consuming process, thermal bonding can be used to join the films, thus improving productivity when joining multiple radiative cooling films to form a canvas-like structure. Incidentally, for thermal bonding, high-frequency welding, hot air welding, and hot welding can be applied.

[0086] Incidentally, it is also preferable to incorporate a plasticizer into the resin layer on the film material side. In this case, the absorption of ultraviolet rays by the plasticizer incorporated into the resin layer on the film material side can be suppressed by mixing in an ultraviolet absorber or coloring it with a color that easily absorbs ultraviolet rays. For this reason, in addition to phthalates, aliphatic dibasic acid esters, and phosphate esters, trimellitic acid esters (TOTM) and epoxidized fatty acid esters (epoxidized soybean oil) can also be used as plasticizers to be incorporated into the resin layer on the film material side.

[0087] In short, according to the further characteristic configuration of the suction air cooling device for air conditioning outdoor units of the present invention, productivity can be improved when joining multiple radiative cooling films to form a canvas-like structure.

[0088] The characteristic configuration of the air intake air cooling method for an air conditioner's outdoor unit of the present invention is that a radiant cooling film is attached to the air intake air drawn into the air conditioner's outdoor unit in a cooling state. Furthermore, when the outdoor unit of the air conditioner is in cooling operation, the radiant cooling film is installed in the cooling operation state, and when the outdoor unit of the air conditioner is in heating operation, the radiant cooling film is installed in a cooling stop state where the intake air is not cooled. A transparent heat-insulating sheet is provided to cover the upper part of the installation space of the outdoor unit of the air conditioner, and the radiant cooling film is installed in a state that covers the upper part of the transparent heat-insulating sheet in the cooling operation state, and in a state that leaves the upper part of the transparent heat-insulating sheet open in the cooling stop state. It's at a single point.

[0089] In other words, A transparent heat-insulating sheet is provided to cover the upper part of the space where the air conditioner outdoor unit is installed. Radiative cooling film , covering the top of the transparent heat-insulating sheet in the cooling state Because it is attached to the condition, During high temperatures such as in summer, the radiative cooling film cools the transparent heat-insulating sheet, which in turn cools the outside air located below the sheet, thereby cooling the intake air drawn into the air conditioning outdoor unit. Even if the air conditioner's outdoor unit is installed facing south, the air drawn into the unit will be at a lower temperature, resulting in improved cooling capacity during hot periods such as summer. Furthermore, during heating operation of the outdoor unit of an air conditioner in low temperatures such as winter, the radiant cooling film is kept in a cooling-off state, preventing the intake air drawn into the outdoor unit from becoming unnecessarily cold, thereby improving heating capacity. In particular, if the air conditioning outdoor unit is installed facing south on the building, the outside air in the space where the unit is installed tends to become hotter even in cold weather such as winter due to direct or indirect heating by sunlight, thus allowing for an appropriate improvement in heating capacity. Furthermore, when the cooling is stopped, the radiative cooling membrane opens up the top of the transparent heat-insulating sheet that covers the upper part of the installation space of the outdoor unit of the air conditioner. Therefore, if the outdoor unit of the air conditioner is installed in a location facing south on the building, sunlight will irradiate the transparent heat-insulating sheet, causing the outside air located below the sheet to reach an appropriate temperature. This will also raise the temperature of the intake air drawn into the outdoor unit of the air conditioner, thereby further improving the heating capacity.

[0090] In other words, the radiative cooling film cools down by emitting electromagnetic waves such as infrared rays to the outside (for example, the sky), and as a result, the intake air drawn into the outdoor unit of the air conditioner is cooled during high temperatures such as in summer, improving the cooling capacity.

[0091] In short, the characteristic configuration of the suction air cooling method for outdoor air conditioning units of the present invention improves cooling capacity during high temperatures such as in summer. This allows for improved heating capacity during low-temperature periods such as winter. . [Brief explanation of the drawing]

[0096] [Figure 1] This is a schematic diagram illustrating a suction air cooling system for an air conditioning outdoor unit. [Figure 2] This is a side view showing the cooling state of the radiative cooling film. [Figure 3] This is a side view showing the state in which the radiative cooling film has stopped cooling. [Figure 4] This figure shows the relationship between the light absorption rate of a resin material and its wavelength. [Figure 5]This figure shows the emissivity spectrum of polyvinyl chloride resin. [Figure 6] This figure shows the emissivity spectrum of vinylidene chloride resin. [Figure 7] This figure shows the optical reflectance spectrum of a silver-based optical reflective layer. [Figure 8] This figure shows the specific structure of the radiative cooling film. [Figure 9] This figure shows the specific structure of the radiative cooling film. [Figure 10] This figure shows the specific structure of the radiative cooling film. [Figure 11] This figure shows the specific structure of the radiative cooling film. [Figure 12] This figure shows the relationship between the light transmittance of polyethylene and wavelength. [Figure 13] This is a diagram illustrating the test configuration. [Figure 14] This figure shows the test results when the protective layer is polyethylene. [Figure 15] This figure shows the test results when the protective layer is made of UV-absorbing acrylic. [Figure 16] This figure shows the emissivity spectrum of polyethylene. [Figure 17] This figure shows the experimental results of plasticizers mixed into polyvinyl chloride resin. [Figure 18] This diagram illustrates an alternative configuration of the radiative cooling layer. [Figure 19] This figure shows the bonding state of the radiative cooling film. [Figure 20] This figure shows a structure in which the radiative cooling layer is formed in an uneven manner. [Figure 21] This figure shows a specific example of the uneven surface of a radiative cooling layer. [Figure 22] This figure shows a specific example of the uneven surface of a radiative cooling layer. [Figure 23] This diagram illustrates a structure in which a filler is mixed into a resin material layer. [Figure 24] This diagram illustrates a structure in which a filler is mixed into a resin material layer. [Figure 25]This diagram illustrates the structure in which filler is mixed into the adhesive layer. [Figure 26] This diagram illustrates the structure in which filler is mixed into the adhesive layer. [Figure 27] This diagram illustrates a structure in which the front and back surfaces of a resin material layer are made uneven. [Figure 28] This is a schematic diagram showing another configuration of a suction air cooling device for an air conditioning outdoor unit. [Figure 29] This is a schematic diagram showing another configuration of a suction air cooling device for an air conditioning outdoor unit. [Figure 30] This is a schematic diagram showing the state after installing the transparent heat-insulating sheet. [Figure 31] This is a schematic diagram showing the state in which the radiative cooling film covers the transparent heat-insulating sheet. [Figure 32] This is a schematic diagram showing another configuration of a suction air cooling device for an air conditioning outdoor unit. [Figure 33] This is a schematic diagram showing another configuration of a suction air cooling device for an air conditioning outdoor unit. [Figure 34] This is a schematic diagram showing another configuration of a suction air cooling device for an air conditioning outdoor unit. [Modes for carrying out the invention]

[0097] Embodiments of the present invention will be described below with reference to the drawings. [Basic configuration of a suction air cooling system for air conditioning outdoor units] As shown in Figure 1, the outdoor unit K of a heat pump air conditioning system is installed near the ground on the south-facing side of the building, and a canvas-like radiant cooling membrane W is installed in a cooling state to cool the intake air drawn into the outdoor unit K. In other words, in this embodiment, the canvas-like radiant cooling membrane W is installed in a state that covers the upper part of the installation space of the outdoor unit K in the cooling state. Incidentally, the radiant cooling membrane W installed in the cooling state has both sides of the installation space open.

[0098] As shown in Figures 2 and 3, the example air conditioner outdoor unit K is equipped with an outside air intake section 1 on the rear side for drawing air into the interior of the air conditioner outdoor unit K, and an air outlet section 2 on the front side for discharging air from the interior of the air conditioner outdoor unit K. The canvas-like radiative cooling film W is formed by joining the edges of multiple rectangular radiative cooling films W, and the details of this will be described later. Therefore, when the air conditioning system operates in cooling mode during the summer, the intake air drawn into the outdoor unit K is cooled, thereby improving its cooling capacity.

[0099] The radiative cooling film W is installed in a way that allows it to be switched between a cooling action state and a cooling stop state where the intake air is not cooled. In other words, the system is configured such that when the air conditioner outdoor unit K is in cooling operation, the radiant cooling membrane W is set to a cooling state that covers the upper part of the installation space of the air conditioner outdoor unit K, and when the air conditioner outdoor unit K is in heating operation, the radiant cooling membrane W is switched to a cooling stop state that leaves the upper part of the installation space of the air conditioner outdoor unit K open. Incidentally, in this embodiment, when the radiative cooling film W is in a cooling state that covers the upper part of the installation space of the air conditioner outdoor unit K, the building (exterior wall) is located on the rear side of the air conditioner outdoor unit K, so only the two sides of the installation space of the air conditioner outdoor unit K are open. Furthermore, in the cooling state, the radiative cooling film W is designed to expose the air outlet 2 of the air conditioning outdoor unit K and to form a passage on the lower side of the radiative cooling film W that allows the exhaust air from the air outlet 2 to flow forward.

[0100] Specifically, as shown in Figures 2 and 3, a storage unit 4 for winding and unwinding the radiative cooling film W is provided at the top of the support column 3, and a support arm 5 for supporting the tip of the radiative cooling film W is provided at the bottom of the support column 3 so as to be able to swing. In the cooling operation state, as shown in Figure 2, the radiant cooling film W is unwound from the storage unit 4, covering the upper part of the installation space of the air conditioner outdoor unit K, with the air outlet 2 of the air conditioner outdoor unit K exposed. In the cooling stop state, as shown in Figure 3, the radiant cooling film W is wound back into the storage unit 4, storing the film in a state that leaves the upper part of the installation space of the air conditioner outdoor unit K open.

[0101] [Basic structure of radiative cooling film] As shown in Figure 1, the radiative cooling membrane W of this embodiment is configured such that a film-like radiative cooling layer CP is attached to the outer surface of the membrane material E, and the membrane material E is cooled by the radiative cooling action of the radiative cooling layer CP. In other words, the radiative cooling membrane W is installed with the membrane material E facing the installation space of the air conditioner outdoor unit K and the radiative cooling layer CP facing outwards. Therefore, in this embodiment, during the cooling operation, the membrane material E cooled by the radiative cooling layer CP is configured to cool the air present in the installation space of the air conditioning outdoor unit K. The radiative cooling layer CP is attached (connected) to the outer surface of the film material E by a connecting layer S made of adhesive or a bonding agent.

[0102] The radiative cooling layer CP comprises an infrared radiation layer A that emits infrared light (IR) from a radiation surface H, and a light-reflecting layer B positioned on the side of the infrared radiation layer A opposite to the radiation surface H, and also includes a protective layer D between the infrared radiation layer A and the light-reflecting layer B. The radiative cooling layer CP is formed in a film-like manner, with the infrared radiation layer A, protective layer D, and light-reflecting layer B arranged in a laminated state. In other words, the radiative cooling layer CP is configured as a radiative cooling film.

[0103] The light-reflecting layer B reflects light L, such as sunlight, that has passed through the infrared radiation layer A and the protective layer D. Its reflection characteristics are such that the reflectance is 90% or more for wavelengths from 400 nm to 500 nm, and 96% or more for wavelengths longer than 500 nm. The solar spectrum exists in the wavelength range from 300 nm to 4000 nm, with intensity increasing as the wavelength increases from 400 nm, and particularly high intensity between 500 nm and 1800 nm.

[0104] Furthermore, while the light-reflecting layer B not only reflects light transmitted through the infrared radiation layer A but also reflects light emitted from the infrared radiation layer A towards the side where the light-reflecting layer B is located, in the following explanation, the purpose of providing the light-reflecting layer B will be assumed to be to reflect light (ultraviolet light, visible light, and infrared light) transmitted through the infrared radiation layer A.

[0105] In this embodiment, light L includes ultraviolet light, visible light, and infrared light. When these are described in terms of wavelengths of light as electromagnetic waves, they include electromagnetic waves with wavelengths from 10 nm to 20,000 nm (electromagnetic waves from 0.01 μm to 20 μm). In this document, the wavelength range of ultraviolet light is assumed to be between 295 nm and 400 nm.

[0106] Because the light-reflecting layer B exhibits a reflectivity of 90% or more in the wavelength range of 400 nm to 500 nm, and a reflectivity of 96% or more in the wavelength range longer than 500 nm, the amount of solar energy absorbed by the light-reflecting layer B by the radiative cooling layer CP (radiative cooling film) can be reduced to 5% or less, and the amount of solar energy absorbed at midday in summer can be reduced to about 50 W.

[0107] The light-reflecting layer B is composed of silver or a silver alloy, or is configured as a laminated structure of silver or a silver alloy located adjacent to the protective layer D and aluminum or an aluminum alloy located away from the protective layer D (infrared radiation layer A), and is flexible. Details thereof will be described later.

[0108] The infrared radiation layer A is composed of a resin material layer J made of a polyvinyl chloride resin whose thickness is adjusted to emit thermal radiation energy greater than the absorbed solar energy in the wavelength band from 8 μm to 14 μm, and its details will be described later. Incidentally, the vinyl chloride resin used in this invention is a homopolymer of vinyl chloride or vinylidene chloride, and a copolymer of vinyl chloride or vinylidene chloride, and is manufactured by conventionally known polymerization methods.

[0109] Therefore, the radiative cooling layer CP is configured to reflect some of the light L incident on the radiative cooling layer CP at the radiating surface H of the infrared radiating layer A, and to reflect the light L that has passed through the resin material layer J and the protective layer D (such as sunlight) at the light reflection layer B, allowing it to escape to the outside from the radiating surface H.

[0110] Furthermore, the system is configured to cool the film material E by converting the heat input from the film material E located on the opposite side of the light-reflecting layer B from the resin material layer J (for example, heat input due to heat conduction from the film material E) into infrared light (IR) by the resin material layer J and radiating it.

[0111] In other words, the radiative cooling layer CP is configured to reflect light L irradiated onto it and to radiate heat transfer to the radiative cooling layer CP (for example, heat transfer from the atmosphere or heat transfer from the film material E) to the outside as infrared light IR. Furthermore, the resin material layer J, protective layer D, and light-reflecting layer B are configured to be flexible, thereby enabling the radiative cooling layer CP (radiative cooling film) to be flexible as well. In addition, the film material E is configured to be flexible, which in turn makes the radiative cooling film W flexible.

[0112] A film material side resin layer Ej, formed of polyvinyl chloride resin or vinylidene chloride resin, is provided on the back surface of the film material E that is separated from the radiative cooling layer CP. In other words, the film material E is formed in a form in which the film material body Eh and the film material side resin layer Ej are laminated together. The membrane material Eh can be formed from woven natural fibers such as cotton and linen, woven inorganic fibers, synthetic fibers, or special fibers, or from nonwoven fabrics such as spunbond, spunlace, or needle-punched fabrics. The thickness of the membrane material Eh is, for example, approximately 0.1 mm to 5 mm. In addition, inorganic fibers include metal fibers and glass fibers, synthetic fibers include polyamide, polyester, polyacrylonitrile, polyvinyl alcohol, polypropyl, and polyethylene, and special fibers include aramid fibers, carbon fibers, and biodegradable fibers.

[0113] [Overview of the resin material layer] The resin material forming the resin material layer J exhibits changes in light absorption and emissivity (photoluminescence) depending on its thickness. Therefore, it is necessary to adjust the thickness of the resin material layer J so as to absorb as little sunlight as possible and emit large amounts of thermal radiation in the wavelength range of the so-called atmospheric window (wavelengths from 8 μm to 14 μm).

[0114] Specifically, from the perspective of sunlight light absorption, the thickness of the resin material layer J needs to be adjusted so that the wavelength average of light absorption from wavelengths of 0.4 μm to 0.5 μm is 13% or less, the wavelength average of light absorption from wavelengths of 0.5 μm to 0.8 μm is 4% or less, the wavelength average of light absorption from wavelengths of 0.8 μm to 1.5 μm is 1% or less, the wavelength average of light absorption from wavelengths of 1.5 μm to 2.5 μm is 40% or less, and the wavelength average of light absorption from wavelengths of 2.5 μm to 4 μm is 100% or less. In this type of absorption distribution, the light absorption rate of sunlight is less than 10%, which translates to less than 100W of energy.

[0115] As described later, the light absorption rate of resin materials increases as the film thickness of the resin material increases. When the resin material is made into a thick film, the emissivity of the atmospheric window becomes approximately 1, and the thermal radiation emitted into space at that time is 125 W / m 2 From 160W / m 2 The amount of sunlight absorbed by protective layer D and light-reflecting layer B is 50 W / m². 2The following applies: The sum of the sunlight absorption in the resin material layer J, protective layer D, and light-reflecting layer B is 150 W / m². 2 The following conditions apply, and cooling will proceed if atmospheric conditions are favorable. The resin material forming the resin layer J should preferably be one with a low light absorption rate near the peak of the solar spectrum, as described above.

[0116] Furthermore, the thickness of the resin material layer J needs to be adjusted so that, from the perspective of infrared radiation (thermal radiation), the wavelength-averaged emissivity in the wavelength range of 8 μm to 14 μm is 40% or more. 50 W / m² is absorbed by protective layer D and light-reflecting layer B. 2 In order for a certain amount of solar thermal energy to be released into space from the resin material layer J through thermal radiation, the resin material layer J needs to emit even greater thermal radiation. For example, when the outside temperature is 30°C, the maximum thermal radiation through an atmospheric window of 8 μm to 14 μm is 200 W / m². 2 This value is obtained (calculated assuming an emissivity of 1). This value is obtained in clear skies in dry environments with thin air, such as high mountains. In lowlands, the thickness of the atmosphere is greater than in high mountains, so the wavelength range of the atmospheric window narrows, and the transmittance decreases. Incidentally, this is called "the atmospheric window narrowing."

[0117] Furthermore, the environment in which the radiative cooling film W, equipped with a radiative cooling layer CP (radiative cooling film), is actually used is often humid, and in that case the atmospheric window also narrows. When used in low-lying areas, the thermal radiation generated in the atmospheric window area is 160 W / m² at 30°C under ideal conditions. 2 It is estimated to be (calculated assuming an emissivity of 1). Also, as is common in Japan, when there is haze or smog in the sky, the atmospheric window becomes even narrower, and the radiation into space is 125 W / m². 2 It will be to that extent. In light of these circumstances, the wavelength-averaged emissivity between 8 μm and 14 μm should be 40% or higher (the thermal radiation intensity in the atmospheric window band is 50 W / m²). 2 Without it, it cannot be used in low-lying areas of the mid-latitude zone.

[0118] Therefore, by adjusting the thickness of the resin material layer J to fall within the optically defined range considering the above factors, the heat output through the window to the atmosphere becomes greater than the heat input due to light absorption from sunlight, enabling radiative cooling outdoors even in a solar environment. In this embodiment, the thickness of the vinyl chloride-based resin (vinyl chloride resin or vinylidene chloride resin) forming the resin material layer J is 100 μm or less and 10 μm or more.

[0119] [Details of the resin material] According to Kirchhoff's laws, emissivity (ε) and light absorptivity (A) are equal. Light absorptivity can be calculated from the absorption coefficient (α) using the relationship A = 1 - exp(-αt) (hereinafter referred to as the light absorptivity relationship), where t is the film thickness. In other words, by adjusting the film thickness of the resin material layer J, a large amount of thermal radiation can be obtained in the wavelength band with a large absorption coefficient. When radiative cooling outdoors, it is advisable to use a material with a large absorption coefficient in the wavelength band of 8 μm to 14 μm, which is the atmospheric window wavelength band. Furthermore, to suppress the absorption of sunlight, it is advisable to use materials that have no or small absorption coefficient in the wavelength range of 0.3 μm to 4 μm, and especially in the range of 0.4 μm to 2.5 μm. As can be seen from the relationship between the absorption coefficient and the absorption rate, the light absorption rate (emissivity) changes depending on the film thickness of the resin material.

[0120] To lower the temperature of a material below that of the surrounding atmosphere through radiative cooling in a solar environment, it is possible to select a material that has a large absorption coefficient in the wavelength range of the atmospheric window and almost no absorption coefficient in the wavelength range of sunlight. By adjusting the film thickness, it is possible to create a state where sunlight is hardly absorbed, but a large amount of thermal radiation is emitted through the atmospheric window, meaning that the output from radiative cooling is greater than the input from sunlight.

[0121] The solar spectrum consists only of wavelengths longer than 0.295 μm. Ultraviolet light is defined as the range of wavelengths shorter than 0.4 μm, visible light as the range of wavelengths from 0.4 μm to 0.8 μm, near-infrared light as the range of wavelengths from 0.8 μm to 3 μm, mid-infrared light as the range of wavelengths from 3 μm to 8 μm, and far-infrared light as the range of wavelengths longer than 8 μm.

[0122] Regarding carbon-chlorine bonds (C-Cl), the bond energy between carbon and chlorine in alkenes is 3.28 eV, and its wavelength is 0.378 μm. Therefore, alkenes absorb a large amount of ultraviolet light from sunlight but hardly absorb any light in the visible range. Figure 4 shows the ultraviolet to visible absorption spectrum of a 100 μm thick polyvinyl chloride resin, where light absorption is greater at wavelengths shorter than 0.38 μm. Figure 4 shows the ultraviolet to visible absorption spectrum of a 100 μm thick vinylidene chloride resin, and a slight increase in the absorption spectrum is observed at wavelengths shorter than 0.4 μm.

[0123] Incidentally, Figure 4 shows the UV-to-visible absorption spectrum of ethylene terephthalate resin (PET) with a thickness of 40 μm, as well as the UV-to-visible absorption spectrum of ethylene resin (polyethylene).

[0124] Figure 5 shows the emissivity of polyvinyl chloride (PVC) resin with carbon-chlorine bonds in the atmospheric window. Figure 6 shows the emissivity of vinylidene chloride (PVDC) resin with carbon-chlorine bonds in the atmospheric window. Regarding carbon-chlorine bonds, the absorption coefficient due to C-Cl stretching vibration appears in a broadband with a full width at half maximum of 1 μm or more, centered around a wavelength of 12 μm. Furthermore, in the case of polyvinyl chloride resin, the absorption coefficient originating from the bending vibration of the CH group of the alkene contained in the main chain appears around a wavelength of 10 μm due to the effect of electron withdrawal by chlorine. The same is true for vinylidene chloride resin. Due to these effects, the wavelength-averaged emissivity of a 10 μm thick film is 43% at wavelengths from 8 μm to 14 μm, which falls within the requirement of a wavelength-averaged emissivity of 40% or more. As shown in the figure, the emissivity in the atmospheric window region increases as the film thickness increases.

[0125] As shown in Figure 5, in the case of polyvinyl chloride resin, even when the thickness exceeds 100 μm, the increase in thermal radiation in the atmospheric window region is almost negligible. In other words, in the case of polyvinyl chloride resin, thermal radiation in the atmospheric window occurs in the part within approximately 100 μm of the surface, and radiation from deeper parts does not escape. As shown in Figure 6, vinylidene chloride resin is similar to vinyl chloride resin.

[0126] As described above, thermal radiation from the atmospheric window region originating from the resin material surface occurs in a portion within approximately 100 μm of the surface depth. As the resin thickness increases beyond this point, the resin material, which does not contribute to thermal radiation, insulates the radiative cooling of the radiative cooling layer CP. Ideally, we would like to fabricate a resin material layer J that absorbs no sunlight at all on top of a light-reflecting layer B. In this case, sunlight is absorbed only by the light-reflecting layer B of the radiative cooling layer CP. The thermal conductivity of resin materials is generally around 0.2 W / m / K. Considering this thermal conductivity, calculations show that when the thickness of the resin material layer J exceeds 20 mm, the temperature of the cooling surface (the side of the light-reflecting layer B opposite to the side where the resin material layer J is present) rises.

[0127] Even if an ideal resin material existed that absorbed no sunlight at all, the thermal conductivity of resin materials is generally around 0.2 W / m / K. Therefore, if the thickness exceeds 20 mm, the light-reflecting layer B will be heated by solar radiation, and the film material E installed on the light-reflecting layer side will also be heated. In other words, the thickness of the resin material in the radiative cooling layer (CP) must be 20 mm or less.

[0128] [Regarding the thickness of the resin material layer] From a practical standpoint, a thinner resin material layer J is preferable for the radiative cooling layer CP. The thermal conductivity of resin materials is generally lower than that of metals and glass. To effectively cool the film material E, the thickness of the resin material layer J should be kept to the minimum necessary. The thicker the resin material layer J is, the greater the thermal radiation from the atmospheric window, and beyond a certain thickness, the thermal radiation energy at the atmospheric window saturates.

[0129] The film thickness at which saturation occurs depends on the resin material, but in the case of resins containing carbon-chlorine bonds, saturation occurs even at a thickness of 100 μm, and sufficient thermal radiation can be obtained in the atmospheric window region even at a thickness of 50 μm. As the thickness of the resin material decreases, the thermal transmittance increases and the temperature of the film material E can be lowered more effectively. Therefore, in the case of resins containing carbon-chlorine bonds, if the thickness is 50 μm or less, the thermal insulation is reduced and the film material E can be cooled effectively. In the case of carbon-chlorine bonds, the film material E can be cooled effectively at a thickness of 100 μm or less.

[0130] Thinning the material has benefits beyond reducing thermal insulation and thus facilitating the transfer of heat and cold. It also suppresses near-infrared light absorption in the near-infrared region, which is caused by carbon-chlorine bond-containing resins originating from CH, CH2, and CH3 atoms. Thinning the material reduces this absorption of sunlight, thereby increasing the cooling capacity of the radiative cooling layer (CP). From the above perspective, in the case of vinyl chloride resins (vinyl chloride resin and vinylidene chloride resin), which are resins containing carbon-chlorine bonds, a thickness of 50 μm or less can more effectively produce a radiative cooling effect under sunlight.

[0131] [Details of the light-reflecting layer] In order for the light-reflecting layer B to have the above-described reflectivity characteristics, the reflective material on the side where the radiating surface H is located (the side where the resin material layer J is located) must be silver or a silver alloy. As shown in Figure 7, if the light-reflecting layer B is constructed using silver as the base, the required reflectivity for the light-reflecting layer B can be obtained.

[0132] When reflecting sunlight using only silver or a silver alloy while maintaining the aforementioned reflectivity characteristics, a thickness of 50 nm or more is required. However, in order to give the light-reflecting layer B flexibility, its thickness must be 100 μm or less. Any thicker and it will become difficult to bend. Incidentally, as a "silver alloy," an alloy can be used in which one of the following elements—copper, palladium, gold, zinc, tin, magnesium, nickel, or titanium—is added to silver in amounts ranging from approximately 0.4% to 4.5% by mass. A specific example is "APC-TR (Furuya Metal)," a silver alloy created by adding copper and palladium to silver.

[0133] In order to give the light-reflecting layer B the above-described reflectivity characteristics, a structure may be used in which silver or a silver alloy located adjacent to the protective layer D is laminated with aluminum or an aluminum alloy located on the side away from the protective layer D (resin material layer J). In this case as well, the reflective material on the side where the radiating surface H is located (the side where the resin material layer J is located) must be silver or a silver alloy. When constructed with two layers of silver (silver alloy) and aluminum (aluminum alloy), the silver layer must be at least 10 nm thick, and the aluminum layer must be at least 30 nm thick. However, in order to give the light-reflecting layer B flexibility, the combined thickness of the silver and aluminum must be 100 μm or less. Any thicker and it will become difficult to bend.

[0134] Incidentally, as for "aluminum alloys," alloys can be made by adding copper, manganese, silicon, magnesium, zinc, carbon steel for machine structures, yttrium, lanthanum, gadolinium, and terbium to aluminum.

[0135] Silver and silver alloys are susceptible to rain and humidity and require protection from these elements, as well as to prevent discoloration. Therefore, as shown in Figures 8 to 11, a protective layer D is necessary to protect the silver, positioned adjacent to the silver or silver alloy. Details of protective layer D will be described later.

[0136] [Specific composition of the radiative cooling film] Because the resin material forming the resin material layer J and the protective layer D of the radiative cooling layer CP is flexible, if the light-reflecting layer B is made into a thin film, the light-reflecting layer B can also be made flexible, and as a result, the radiative cooling layer CP can be made into a flexible film (radiative cooling film).

[0137] Then, as shown in Figures 8 to 11, the film material E can be cooled by attaching the radiative cooling layer CP (radiative cooling film) to the outer surface of the film material E with an adhesive or bonding layer S. Adhesives or adhesives used for the connecting layer S include urethane-based adhesives (adhesives), acrylic-based adhesives (adhesives), and EVA (ethylene vinyl acetate)-based adhesives (adhesives).

[0138] In Figures 8 to 11, the membrane material E is exemplified by a membrane material E obtained by immersing the membrane material body Eh in a resin solution of polyvinyl chloride resin or vinylidene chloride resin, thereby impregnating the membrane material body Eh with polyvinyl chloride resin or vinylidene chloride resin. Therefore, the film material E is configured to have a film material side resin layer Ej formed of polyvinyl chloride resin or vinylidene chloride resin on the back surface away from the radiative cooling layer CP, and a surface side resin layer Ek formed of polyvinyl chloride resin or vinylidene chloride resin on the surface that approaches the radiative cooling layer CP. In other words, the film material E is formed in a form in which a surface resin layer Ek, ​​a film material body Eh, and a film material side resin layer Ej are laminated together.

[0139] Incidentally, in Figures 8 to 11, the film material E may be formed by omitting the surface resin layer Ek and laminating the film material body Eh and the film material side resin layer Ej, as shown in Figure 1. To form a film material E in a laminated form consisting of a film material body Eh and a film material side resin layer Ej, one can use a manufacturing procedure such as applying polyvinyl chloride resin or vinylidene chloride resin to the film material body Eh to form the film material side resin layer Ej, or attaching a separately manufactured film of polyvinyl chloride resin or vinylidene chloride resin to the film material body Eh to form the film material side resin layer Ej.

[0140] Various forms are possible for fabricating the radiative cooling layer CP in film form. For example, it can be fabricated by coating a protective layer D and a resin material layer J onto a light-reflecting layer B fabricated in film form. Alternatively, it can be fabricated by attaching the protective layer D and the resin material layer J to a light-reflecting layer B fabricated in film form. Alternatively, it can be fabricated by coating or attaching the protective layer D onto a resin material layer J fabricated in film form, and then fabricating the light-reflecting layer B on top of the protective layer D by vapor deposition, sputtering, ion plating, silver mirror reaction, etc.

[0141] To explain in more detail, the radiative cooling layer CP (radiative cooling film) in Figure 8 is formed when the light-reflecting layer B is formed as a single layer of silver or a silver alloy, or when it is composed of two layers of silver (silver alloy) and aluminum (aluminum alloy). A protective layer D is formed above the light-reflecting layer B, and a resin material layer J is formed above the protective layer D. Furthermore, a lower protective layer Ds is also formed below the light-reflecting layer B. Incidentally, the lower protective layer Ds is formed of, for example, acrylic resin.

[0142] As a method for creating the radiative cooling layer CP (radiative cooling film) shown in Figure 8, a method can be employed in which a protective layer D, a light-reflecting layer B, and an underside protective layer Ds are sequentially applied to a film-like resin material layer J and integrally molded.

[0143] The radiative cooling layer CP (radiative cooling film) in Figure 9 consists of a light-reflecting layer B composed of an aluminum layer B1 made of aluminum foil that functions as aluminum (aluminum alloy) and a silver layer B2 made of silver or a silver alloy. A protective layer D is formed above the light-reflecting layer B, and a resin material layer J is formed above the protective layer D.

[0144] As a method for creating the radiative cooling layer CP (radiative cooling film) shown in Figure 9, a method can be employed in which a silver layer B2, a protective layer D, and a resin material layer J are sequentially applied to an aluminum layer B1 made of aluminum foil, and then integrally molded. Alternatively, a manufacturing method can be employed in which the resin material layer J is formed into a film, the protective layer D and the silver layer B2 are sequentially applied onto the film-like resin material layer J, and the aluminum layer B1 is attached to the silver layer B2.

[0145] The radiative cooling layer CP (radiative cooling film) in Figure 10 is formed when the light-reflecting layer B is made of a single layer of silver or a silver alloy, or when it is made of two layers of silver (silver alloy) and aluminum (aluminum alloy), a protective layer D is formed on the upper side of the light-reflecting layer B, a resin material layer J is formed on the upper side of the protective layer D, and a film layer F such as PET is formed on the lower side of the light-reflecting layer B.

[0146] As a method for creating the radiative cooling layer CP (radiative cooling film) shown in Figure 10, a light-reflecting layer B and a protective layer D are sequentially applied to a film layer F (corresponding to the substrate) formed in film form from PET (ethylene terephthalate resin) or the like, and the layers are integrally molded. A separately formed film-like resin material layer J is then bonded to the protective layer D with an adhesive layer N. Adhesives used in the adhesive layer N include, for example, urethane-based adhesives, acrylic-based adhesives, and EVA (ethylene vinyl acetate)-based adhesives, and those with high transparency to sunlight are desirable.

[0147] The radiative cooling layer CP (radiative cooling film) in Figure 11 consists of a light-reflecting layer B composed of an aluminum layer B1 that functions as aluminum (aluminum alloy) and a silver layer B2 made of silver or a silver alloy (alternative silver). The aluminum layer B1 is formed on top of a film layer F (corresponding to the base material) which is formed in the form of a film using PET (ethylene terephthalate resin) or the like. A protective layer D is formed on the upper side of the silver layer B2, and a resin material layer J is formed on the upper side of the protective layer D.

[0148] As a method for creating the radiative cooling layer CP (radiative cooling film) shown in Figure 11, an aluminum layer B1 is applied to a film layer F to integrally form the film layer F and the aluminum layer B1. Separately, a protective layer D and a silver layer B2 are applied to a film-like resin material layer J to integrally form the resin material layer J, protective layer D, and silver layer B2, and the aluminum layer B1 and silver layer B2 are bonded together with an adhesive layer N. Adhesives used in the adhesive layer N include, for example, urethane-based adhesives, acrylic-based adhesives, and EVA (ethylene vinyl acetate)-based adhesives, and those with high transparency to sunlight are desirable.

[0149] [Details of the protective layer] The protective layer D is a polyolefin resin with a thickness of 300 nm or more and a thickness of 40 μm or less, or polyethylene terephthalate with a thickness of 17 μm or more and a thickness of 40 μm or less. Polyolefin resins include polyethylene and polypropylene.

[0150] As mentioned above, Figure 4 shows the ultraviolet absorption rate of polyethylene (olefin resin). Figure 12 also shows the light transmittance of polyethylene, which is suitable as a synthetic resin for forming the protective layer D.

[0151] Since the radiative cooling layer CP (radiative cooling film) exhibits radiative cooling not only at night but also in sunlight, in order to maintain the light-reflecting function of the light-reflecting layer B, it is necessary to protect the light-reflecting layer B with the protective layer D so that the silver of the light-reflecting layer B does not discolor in sunlight.

[0152] When the protective layer D is formed from a polyolefin resin with a thickness of 300 nm or more and a thickness of 40 μm or less, the polyolefin resin is a synthetic resin in which the light absorption rate of ultraviolet light is 10% or less across the entire ultraviolet wavelength range from 0.295 μm to 0.4 μm. Therefore, the protective layer D is less likely to deteriorate due to ultraviolet light absorption.

[0153] Furthermore, since the thickness of the polyolefin resin forming the protective layer D is 300 nm or more, it effectively blocks radicals generated in the resin material layer J from reaching the silver or silver alloy forming the light-reflecting layer, and also blocks moisture passing through the resin material layer J from reaching the silver or silver alloy forming the light-reflecting layer B. As a result, discoloration of the silver or silver alloy forming the light-reflecting layer B can be suppressed.

[0154] Incidentally, the protective layer D, which is made of polyolefin resin, deteriorates by absorbing ultraviolet light, forming radicals on the surface side away from the light-reflecting layer B. However, since its thickness is 300 nm or more, the formed radicals do not reach the light-reflecting layer B. Furthermore, even though it deteriorates while forming radicals, the rate of deterioration is slow due to the low absorption of ultraviolet light, so the aforementioned blocking function is maintained over a long period of time.

[0155] When the protective layer D is formed of ethylene terephthalate resin with a thickness of 17 μm or more and a thickness of 40 μm or less, ethylene terephthalate resin is a resin material that has a higher ultraviolet light absorption rate than polyolefin resins in the ultraviolet wavelength range of 0.295 μm to 0.4 μm. However, because the thickness is 17 μm or more, it effectively blocks radicals generated in the resin material layer J from reaching the silver or silver alloy forming the light-reflecting layer B, and also blocks moisture passing through the resin material layer J from reaching the silver or silver alloy forming the light-reflecting layer. This effectively provides a long-term blocking function, thereby suppressing discoloration of the silver or silver alloy forming the light-reflecting layer B.

[0156] In other words, the protective layer D, formed from ethylene terephthalate resin, degrades by absorbing ultraviolet light, forming radicals on the surface side away from the light-reflecting layer B. However, because its thickness is 17 μm or more, the formed radicals do not reach the light-reflecting layer B. Furthermore, even if it degrades while forming radicals, its thickness of 17 μm or more ensures that the aforementioned shielding function is maintained over a long period of time.

[0157] To elaborate, the degradation of ethylene terephthalate resin (PET) is caused by the cleavage of the ester bond between ethylene glycol and terephthalic acid due to ultraviolet light, which forms radicals. This degradation progresses sequentially from the surface of the ethylene terephthalate resin (PET) that is irradiated with ultraviolet light.

[0158] For example, when ethylene terephthalate resin (PET) is irradiated with ultraviolet light of the same intensity as in Osaka, the ester bonds of the ethylene terephthalate resin (PET) break down at a rate of approximately 9 nm per day, starting from the irradiated surface. Since the ethylene terephthalate resin (PET) is sufficiently polymerized, the cleaved ethylene terephthalate resin (PET) on the surface does not attack the silver (silver alloy) in the light-reflecting layer B. However, if the cleaved edges of the ethylene terephthalate resin (PET) reach the silver (silver alloy) in the light-reflecting layer B, the silver (silver alloy) will discolor.

[0159] Therefore, in order to ensure that protective layer D lasts for more than one year when used outdoors, a thickness of approximately 3 μm is required, calculated by adding up 9 nm / day and 365 days. To ensure that the ethylene terephthalate resin (PET) of protective layer D lasts for more than three years, a thickness of 10 μm or more is required. To ensure it lasts for more than five years, a thickness of 17 μm or more is required.

[0160] Furthermore, when forming the protective layer D with polyolefin resin and ethylene terephthalate resin, the reason for setting an upper limit on its thickness is to avoid the protective layer D exhibiting thermal insulation properties that do not contribute to radiative cooling. In other words, the thicker the protective layer D becomes, the less it contributes to radiative cooling. Therefore, an upper limit on its thickness is set to ensure that it performs its function of protecting the light-reflecting layer B while avoiding thermal insulation properties that do not contribute to radiative cooling.

[0161] In other words, while increasing the thickness of protective layer D does not create any disadvantages in preventing discoloration of the silver (silver alloy) in light-reflecting layer B, it does create problems in radiative cooling. That is, increasing the thickness increases the thermal insulation of the radiative cooling material. For example, a resin whose main component is polyethylene, which is excellent as a synthetic resin for forming protective layer D, does not contribute to radiative cooling even when formed thickly, because its emissivity in the atmospheric window is low, as shown in Figure 16. On the contrary, increasing its thickness increases the thermal insulation of the radiative cooling material. Next, as the thickness increases, the absorption in the near-infrared region due to vibrations of the main chain increases, and the effect of increasing solar absorption increases. Due to these factors, a thick protective layer D is disadvantageous for radiative cooling. From this viewpoint, the thickness of the protective layer D formed from polyolefin resin is preferably 5 μm or less, and more preferably 1 μm.

[0162] Incidentally, as shown in Figure 10, when an adhesive layer N is located between the resin material layer J and the protective layer D, radicals will also be generated from the adhesive layer N. However, if the thickness of the polyolefin resin forming the protective layer D is 300 nm or more, and the thickness of the ethylene terephthalate resin forming the protective layer D is 17 μm or more, then the radicals generated in the adhesive layer N can be suppressed from reaching the light reflection layer B over a long period of time.

[0163] [Consideration of protective layers] To investigate the differences in how silver is colored by the protective layer D, a sample was prepared in which the protective layer D was exposed without the resin material layer J acting as the infrared radiation layer A, as shown in Figure 13, and the coloration of the silver after irradiation with simulated sunlight was examined. Specifically, two types of protective layers D were formed by coating a film layer F (corresponding to the substrate) containing silver as the light-reflecting layer B, using a bar coater. These two layers were a general acrylic resin that absorbs ultraviolet light (for example, methyl methacrylate resin mixed with a benzotriazole-based ultraviolet absorber) and polyethylene. The function of these protective layers D was then investigated. The thicknesses of the coated protective layers D were 10 μm and 1 μm, respectively. Furthermore, the film layer F (corresponding to the base material) is formed in film form from PET (ethylene terephthalate resin) or the like.

[0164] As shown in Figure 15, if the protective layer D is an acrylic resin that absorbs ultraviolet light well, the protective layer D is decomposed by ultraviolet light and forms radicals, causing the silver to quickly yellow and cease to function as a radiative cooling layer CP (it absorbs sunlight and its temperature rises when exposed to sunlight, like ordinary materials). Note that the 600h line in the diagram represents the xenon weather test conducted under the conditions of JIS standard 5600-7-7 (ultraviolet light energy of 60 W / m²). 2 This is the reflectance spectrum after 600 hours of testing. The line at 0h represents the reflectance spectrum before the xenon weather test.

[0165] As shown in Figure 14, when the protective layer D is made of polyethylene, which has a low ultraviolet light absorption rate, no decrease in reflectivity is observed in the near-infrared to visible regions. In other words, since the main component of the resin is polyethylene (polyolefin resin), it hardly absorbs the ultraviolet rays of sunlight that reach the ground, and therefore does not easily form radicals even when exposed to sunlight, so the silver coloration of the light-reflecting layer B does not occur even when exposed to sunlight. Note that the 600h line in the diagram represents the xenon weather test conducted under the conditions of JIS standard 5600-7-7 (ultraviolet light energy of 60 W / m²). 2 This is the reflectance spectrum after 600 hours of testing. The line at 0h represents the reflectance spectrum before the xenon weather test.

[0166] The reason the reflectance spectrum in this wavelength range is wavy is due to the Fabry-Perot resonance of the polyethylene layer. While the resonance position differs slightly between the 0h and 600h lines due to changes in the polyethylene layer's thickness caused by the heat of the xenon weather test, no significant decrease in reflectance in the ultraviolet-visible range due to silver yellowing is observed.

[0167] Furthermore, while fluororesin-based materials can also be used as materials for forming protective layer D from the standpoint of UV absorption, they cannot actually be used as materials for forming protective layer D because they become discolored and deteriorate during the formation process. Furthermore, while silicone can also be used as a material to form protective layer D from the standpoint of UV absorption, its adhesion to silver (silver alloy) is extremely poor, making it unsuitable as a material for forming protective layer D.

[0168] [Regarding the inclusion of plasticizers] When forming the resin material layer J with a vinyl chloride resin, it is preferable to mix a plasticizer into the vinyl chloride resin to improve flexibility. The plasticizers used in polyvinyl chloride resins are phthalates, aliphatic dibasic acid esters, or phosphate esters. Furthermore, the plasticizer is mixed in at a rate of 1 part by weight or more and 200 parts by weight or less per 100 parts by weight of the vinyl chloride resin. Ideally, from a processing standpoint, the amount of plasticizer should be 100 parts by weight or less.

[0169] The aliphatic dibasic acid ester of the plasticizer may be composed of adipic acid esters, adipic acid ester copolymers, azelaic acid esters, azelaic acid ester copolymers, sebaciate esters, sebaciate ester copolymers, succinic acid esters, or succinic acid ester copolymers, either individually or in combination of several of these.

[0170] The aliphatic dibasic acid ester of the plasticizer is preferably one in which an aliphatic dibasic acid and two molecules of saturated aliphatic alcohol are esterified together. The phthalate ester plasticizer is preferably formed by esterifying phthalic acid with two molecules of saturated aliphatic alcohol. The phosphate ester of the plasticizer is preferably a triester phosphate or an aromatic phosphate ester.

[0171] <Details on phthalates> The following is a list of phthalate esters: Dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DPP), di-2-ethylhexyl phthalate (DOP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), diundecyl phthalate (DUP), ditridecyl phthalate (DTDP), bis(2-ethylhexyl) terephthalate (DOTP), bis(2-ethylhexyl) isophthalate (DOIP), etc.

[0172] <Details of aliphatic dibasic acid esters> The aliphatic dibasic acid esters are listed below. Dibutyl adipate (DBA), diisobutyl adipate (DIBA), di-2-ethylhexyl adipate (DOA), diisononyl adipate (DINA), diisodecyl adipate (DIDA), bis-2-ethylhexyl azelaate (DOZ), dibutyl sebacate (DBS), di-2-ethylhexyl sebacate (DOS), diisononyl sebacate (DINS), diethyl succinate (DESU), etc. Additionally, aliphatic polyesters with a molecular weight of 400-4000 are synthesized by copolymerization (polyesterification) of dibasic acids such as adipic acid with diols (difunctional alcohols or glycols).

[0173] <Triester Phosphate> The following is a list of phosphate triesters: Trimethyl phosphate (TMP), triethyl phosphate (TEP), tributyl phosphate (TBP), tris(2-ethylhexyl) phosphate (TOP).

[0174] <Aromatic phosphate esters> The aromatic phosphate esters are listed below. Triphenyl phosphate (TPP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), trezyl diphenyl phosphate (CDP), 2-ethylhexyl diphenyl phosphate.

[0175] <Regarding the proper evaluation of plasticizers> Plasticizers for polyvinyl chloride resins include phthalates, aliphatic dibasic acids, phosphate triesters, aromatic phosphates, trimellitic acids, and epoxidized fatty acid esters. From these plasticizers, the following compounds were selected, and 43 parts by weight of each plasticizer were mixed with 100 parts by weight of polyvinyl chloride and evaluated by xenon weather testing. Furthermore, the vinyl chloride resin was mixed with 0.5 parts by weight each of a triazine-based ultraviolet absorber and a hindered amine-based light stabilizer per 100 parts by weight of vinyl chloride.

[0176] Representative examples of phthalate esters include di-2-ethylhexyl phthalate (DOP) and diisodecyl phthalate (DIDP). Representative aliphatic dibasic acid esters include di-2-ethylhexyl adipate (DOA), butanediol adipate copolymer (average molecular weight around 1000), and diisononyl adipate (DINA). A representative example of phosphate triesters is tributyl phosphate (TBP). A representative example of aromatic phosphate esters is tricresyl phosphate (TCP). A representative example of trimellitic acid esters is trimellitic 2-ethylhexyl trimellitic acid (TOTM). A representative example of an epoxidized fatty acid ester is epoxidized soybean oil.

[0177] Durability testing involved a xenon weather test lasting 1920 hours (equivalent to 4 years of actual exposure), and the results were used to determine the superiority or inferiority of durability. Note that 487 hours of UV exposure is equivalent to one year. The conditions for the xenon weather test are as follows: UV intensity 180W / m 2 (wavelength 295-400nm). <Conditions without watering> BPT 89℃, humidity 50%, 1 hour 42 minutes. <Conditions with watering> Tank temperature 38°C, humidity 90%, 18 minutes.

[0178] The results of the 1920-hour test are shown in Figure 17. Incidentally, although the experiment was conducted using polyvinyl chloride resin in this embodiment, the results are similar for vinylidene chloride resin. The results of the above experiment revealed that using trimellitic acid ester (TOTM) and epoxidized fatty acid ester (epoxidized soybean oil) as plasticizers significantly reduced durability. Note that the epoxidized fatty acid turned brown after 1120 hours, making it impossible to continue the test, and is therefore not shown in the figure.

[0179] In contrast, it was found that phthalate esters, aliphatic dibasic acid esters, phosphate triesters, and aromatic phosphate esters could be used to maintain durability for about four years. In other words, when phthalate esters, aliphatic dibasic acid esters, phosphate triesters, and aromatic phosphate esters were used as plasticizers mixed into vinyl chloride resin, the reflectivity of the radiative cooling layer CP did not decrease even after about four years. However, when trimellitic acid esters and epoxidized fatty acid esters were used as plasticizers mixed into vinyl chloride resin, the reflectivity of the radiative cooling layer CP decreased significantly even before about four years had passed.

[0180] Based on the above test results, it can be seen that phthalates, aliphatic dibasic acid esters, phosphate triesters, and aromatic phosphate esters have excellent durability as plasticizers for vinyl chloride resins, while trimellitic acid esters and epoxidized fatty acid esters have no durability. Furthermore, the reasons for this will be examined and systematized as described later.

[0181] [Regarding other additives] The vinyl chloride resin forming the resin material layer J may contain flame retardants, stabilizers, stabilizing aids, fillers, antioxidants, ultraviolet absorbers, and light stabilizers.

[0182] [Alternative configuration of the radiative cooling layer] As shown in Figure 18, the radiative cooling layer CP may be configured such that it has an anchor layer G on top of a film layer F (corresponding to the substrate), and a light reflection layer B, a protective layer D, and an infrared radiation layer A on top of the anchor layer G. Furthermore, the film layer F (corresponding to the substrate) is formed in film form from, for example, PET (ethylene terephthalate resin).

[0183] The anchor layer is introduced to strengthen the adhesion between the film layer F and the light-reflecting layer B. In other words, if silver (Ag) were to be directly deposited on the film layer F, there is a risk of it easily peeling off. The anchor layer G is mainly composed of acrylic, polyolefin, or urethane, and preferably contains compounds with isocyanate groups or melamine resin. Since it is a coating for parts that are not directly exposed to sunlight, it is acceptable to use a material that absorbs ultraviolet rays. Furthermore, there are other methods to strengthen the adhesion between the film layer F and the light-reflecting layer B besides inserting an anchor layer G. For example, roughening the surface of the film layer F by irradiating it with plasma will improve adhesion.

[0184] [Consideration of the connection layer] When a radiative cooling layer CP is attached to the outer surface of the film material E, it is preferable to make the thickness of the connecting layer S 5 μm or more and 100 μm or less. In other words, the outer surface (surface) of film material E is often not mirror-like. The outer surface (material surface) of film material E, which is not mirror-like, often has countless scratches and irregularities on the order of a few micrometers. When micrometer-level irregularities present on the outer surface (material surface) of the film material E are transferred to the light-reflecting layer B (silver layer) of the radiative cooling layer CP, the reflectivity decreases. Therefore, it is necessary to introduce a structure that prevents the irregularities present on the outer surface (material surface) from being reflected in the radiative cooling layer CP. For this purpose, it is preferable to bond the radiative cooling layer CP to the outer surface of the film material E with a connecting layer S with a thickness of approximately 5 μm to 100 μm.

[0185] If a connecting layer S of 5 μm or more, composed of adhesive or bonding agent, is present, the connecting layer S absorbs the irregularities on the outer surface of the film material E, and the light-reflecting layer B (silver layer) of the radiative cooling layer CP becomes flat. When the light-reflecting layer B (silver layer) becomes flat, it prevents a decrease in the reflectivity of sunlight (in other words, an increase in the absorption rate of sunlight). However, increasing the thickness of the connecting layer S improves thermal insulation. Improved thermal insulation is undesirable because it insulates the radiative cooling layer CP from its cold energy. From this perspective, an unnecessarily thick connecting layer S is not needed; a thickness of 100 μm is sufficient.

[0186] [Connecting the radiative cooling film] To manufacture canvas using a radiative cooling film W, multiple radiative cooling films W are joined together to form the canvas. On the surface side of the radiative cooling film W, there is a resin material layer J (infrared radiation layer A) made of polyvinyl chloride resin or vinylidene chloride resin, and on the back side of the radiative cooling film W, there is a film material side resin layer Ej made of polyvinyl chloride resin or vinylidene chloride resin. Therefore, as shown in Figure 19, multiple radiative cooling films W are joined together by thermal welding.

[0187] In other words, when forming canvas, multiple radiative cooling films W are joined together, for example, by joining the edges of rectangular films W. Since this joining can be done by heat welding, the productivity of forming canvas can be improved. Incidentally, for heat welding, high-frequency welding, hot air welding, and hot welding can be applied.

[0188] [Another example of a radiative cooling film] When the structure is made of canvas formed by joining multiple radiative cooling films W, it is preferable to form the radiating surface H of the radiative cooling layer CP in an uneven shape, as shown in Figure 20. In other words, for example, it may be formed in such a state that a convex portion U exists on the radiating surface H. Specific examples of the uneven surface include a line-and-space structure with rectangular convex U sections arranged in a row (see Figure 21), a structure with conical prism-shaped convex U sections arranged vertically and horizontally (see Figure 22), and although not shown in the illustration, various configurations can be adopted, such as a structure with triangular prism or pyramidal convex U sections arranged in a line-and-space pattern, a structure with rectangular convex U sections arranged vertically and horizontally, and a structure with randomly formed convex U sections. Incidentally, the height difference when forming the uneven surface H is approximately 100 μm.

[0189] One advantage of forming the radiating surface H in an uneven shape is that, due to wind or other factors, outside air flows, and the heat from the radiative cooling layer CP is released into the outside air through heat exchange. From this perspective, as shown in Figure 20, it is preferable to increase the surface area of ​​the infrared radiation layer A of the radiative cooling layer CP by forming an uneven surface through embossing or the like.

[0190] Forming the radiating surface H with an uneven surface also has aesthetic advantages. When the radiating surface H (top surface) of the radiating cooling layer CP is formed with an uneven surface, sunlight is scattered more effectively than when the radiating surface H is mirror-like, thus reducing the glare of the radiating cooling layer CP. Furthermore, even if the radiating surface H is given the function of "scattering," the light absorption in the silver (silver alloy) of the light-reflecting layer B does not increase, so radiative cooling can be performed effectively.

[0191] [Alternative configuration of the radiative cooling layer] As shown in Figures 23 and 24, an inorganic filler Q may be mixed into the resin material layer J that constitutes the infrared radiation layer A to provide a light scattering structure. Furthermore, as shown in Figures 25 and 26, if an adhesive layer N connecting the resin material layer J and the protective layer D is provided between the resin material layer J and the protective layer D, an inorganic filler Q may be mixed into the adhesive layer N to provide a light scattering structure. Suitable adhesives or sealants for the adhesive layer include urethane-based, acrylic-based, and ethylene vinyl acetate-based adhesives. In other words, the adhesive used in the adhesive layer N includes, for example, urethane-based adhesives, acrylic-based adhesives, and EVA (ethylene vinyl acetate)-based adhesives, and those with high transparency to sunlight are applied. Incidentally, the thickness of the adhesive layer N is, for example, about 10 μm.

[0192] Incidentally, the radiative cooling film W shown in Figures 23 to 26 has the same configuration as the radiative cooling film W shown in Figure 10 (a configuration in which a lower protective layer Ds is provided as a film layer F). However, when an inorganic material filler Q is mixed into the resin material layer J, the radiative cooling film W with the configurations shown in Figures 8, 9, and 11 can be applied.

[0193] By incorporating inorganic filler Q into the resin material layer J, when the radiative cooling layer CP is viewed from the side of the radiating surface H, the inorganic filler Q mixed into the transparent resin material layer J is visible. Due to the light scattering effect of the inorganic filler Q, the color of the radiative cooling film W when viewed from the side of the radiating surface H becomes white, thereby improving its aesthetic appearance.

[0194] Furthermore, by incorporating an inorganic filler Q into the adhesive layer N connecting the resin material layer J and the protective layer D, when the radiative cooling layer CP is viewed from the side where the radiating surface H is located, the inorganic filler Q mixed into the adhesive layer N is seen through the transparent resin material layer J. As a result, the light scattering effect of the inorganic filler Q causes the radiative cooling film W to appear white when viewed from the side where the radiating surface H is located, thereby improving its aesthetic appearance. Furthermore, filler Q may be mixed into both the resin material layer J and the adhesive layer N.

[0195] Suitable inorganic materials for forming filler Q include silicon dioxide (SiO2), titanium dioxide (TiO2), aluminum oxide (Al2O3), magnesium oxide (MgO), calcium carbonate (CaCO3), and the like. In particular, titanium dioxide (TiO2) of about 200 nm, which does not exhibit photocatalytic activity, can be suitably used. Furthermore, titanium dioxide (TiO2) may be coated with at least one of the following: alumina, silica, or zirconia. By doing so, the filler can be appropriately made non-photocatalytically active, making it easier to suppress the degradation of the resin material layer J.

[0196] Incidentally, when filler Q is mixed into the resin material layer J, both the front and back surfaces of the resin material layer J become uneven. If the back surface of the resin material layer J is uneven, it is desirable to position the adhesive layer N between the resin material layer J and the protective layer D. In other words, even if the back surface of the resin material layer J is uneven, the adhesive layer N (bonding layer) is located between the resin material layer J and the protective layer D, so the resin material layer J and the protective layer D can be properly bonded together. Furthermore, if the back surface of the resin material layer J is uneven, the resin material layer J and the protective layer D may be directly joined by, for example, plasma bonding. Plasma bonding is a method in which radicals are formed by the emission of plasma from the bonding surface of the resin material layer J and the bonding surface of the protective layer D, and the materials are joined by these radicals.

[0197] [Regarding the inclusion of fillers in the protective layer] Incidentally, if filler Q is mixed into protective layer D, the back surface of protective layer D that is in contact with light-reflecting layer B will become uneven, causing the surface of light-reflecting layer B to deform into an uneven state. Therefore, it is necessary to avoid mixing filler Q into protective layer D. In other words, if the surface of light-reflecting layer B deforms into an uneven state, it will not be able to reflect light properly, and as a result, radiative cooling will not be able to occur properly.

[0198] [Alternative configuration of the infrared radiation layer] As shown in Figure 27, the front and back surfaces of the resin material layer J constituting the infrared radiation layer A may be formed in an uneven manner to provide a light scattering structure. This configuration allows for the suppression of glare from the radiating surface H when viewed.

[0199] In other words, the resin material layer J of the radiative cooling layer CP shown in Figures 8 to 11 has a configuration in which both the front and back surfaces are flat and filler Q is not mixed in. However, in such a configuration, the radiating surface H becomes mirror-like, so when the radiating surface H is viewed, a glare is perceived. However, this glare can be suppressed by incorporating a light scattering configuration.

[0200] To create an uneven surface on both the front and back surfaces of the resin material layer J, methods such as embossing or scratching the surface can be used. Even if the back surface of the resin material layer J is uneven, the resin material layer J and the protective layer D can be properly bonded together by positioning the adhesive layer N between the resin material layer J and the protective layer D.

[0201] [Alternative configuration of suction air cooling system for air conditioning outdoor units] As shown in Figure 28, the radiative cooling film W may be provided in such a way that it also covers the front side of the air conditioner outdoor unit K when the cooling is in operation. In this case, it is preferable to form an exhaust hole 6 in the radiative cooling film W at a location facing the air outlet 2 of the air conditioner outdoor unit K, which discharges the air blown out from the air outlet 2 to the outside, thereby forming a passage that causes the exhaust air from the air outlet 2 to flow forward.

[0202] Figures 1 to 3 illustrate the case where the radiative cooling film W is installed to cover the entire installation space of the air conditioner outdoor unit K. However, as shown in Figure 29, if the outside air intake section 1 is formed on the side of the air conditioner outdoor unit K, the radiative cooling film W may be installed to cover the space on the side of the installation space of the air conditioner outdoor unit K where the outside air intake section 1 is located. Incidentally, when the radiative cooling film W is installed in a cooling operation state, both sides of the installation space are open.

[0203] Although not shown in the diagram, the outer surface of the air conditioning outdoor unit K and the floor on which the air conditioning outdoor unit K is placed may be painted black to make them more likely to absorb heat from sunlight when the cooling of the radiative cooling film W is stopped.

[0204] As shown in Figure 28, when the radiative cooling membrane W is installed in a manner that covers the entire installation space of the air conditioner outdoor unit K, a transparent heat-insulating sheet 7 is provided to cover the upper part of the installation space of the air conditioner outdoor unit K, as shown in Figures 30 and 31. Furthermore, the radiative cooling film W may be provided in such a manner that it covers the upper part of the transparent heat-insulating sheet 7 when the cooling is in progress, and leaves the upper part of the transparent heat-insulating sheet 7 open when the cooling has stopped.

[0205] Incidentally, in this configuration, a sheet-side discharge hole 7A is formed in the transparent heat-insulating sheet 7 at a location facing the air outlet 2 of the air conditioning outdoor unit K, to discharge the air blown out from the air outlet 2 to the outside. Also, the radiative cooling membrane W has a discharge hole 6, similar to Figure 28, to discharge the air blown out from the air outlet 2 to the outside. In other words, when the cooling of the radiative cooling membrane W is stopped, a passage portion for directing the exhaust air from the air outlet 2 forward is formed by the sheet-side discharge hole 7A, and when the cooling of the radiative cooling membrane W is in operation, a passage portion for directing the exhaust air from the air outlet 2 forward is formed by the sheet-side discharge hole 7A and the discharge hole 6.

[0206] As shown in Figure 32, the radiative cooling film W may be provided in a cylindrical shape extending upward from the outside air intake section 1 of the air conditioning outdoor unit K to the upper part of the building. In other words, for example, the radiative cooling film W may be provided in a cylindrical shape by providing a base material formed from a plate or mesh material made of synthetic resin, and holding the radiative cooling film W in a cylindrical shape on the outer surface of the base material. In this configuration, when stopping the cooling of the radiant cooling membrane W, the connection between the radiant cooling membrane W and the air conditioning outdoor unit K is disconnected, or the radiant cooling membrane W is removed, so that the outside air intake unit 1 can draw in outside air from the radiant cooling membrane W.

[0207] As shown in Figure 33, if a hood 8 is provided to surround the upper and side portions of the outside air intake section 1 of the outdoor air conditioning unit K, the radiative cooling film W may be attached to the outer surface of the hood 8. In other words, in snowy regions, the air conditioning outdoor unit K is supported high above the ground by a frame 9, and a hood 8 is provided to surround the top and sides of the outside air intake section 1, and an outlet-side hood 10 is provided to surround the top and sides of the air outlet section 2. In such cases, a radiative cooling film W may be attached to the outer surface of the hood 8 surrounding the top and sides of the outside air intake section 1.

[0208] Incidentally, the radiative cooling film W attached to the outer surface of the hood 8 can be one that includes a film material E, but a radiative cooling film W without the film material E may also be used. In other words, for example, a radiative cooling layer CP in the form shown in Figure 10, in which the film material E is omitted, may be used as the radiative cooling film W, and the radiative cooling film W may be attached to the outer surface of the hood 8 by adhesive. Various adhesives such as urethane-based, acrylic-based, and ethylene vinyl acetate-based adhesives can be used.

[0209] As shown in Figure 28, when an exhaust hole 6 is formed in the radiative cooling membrane W at a location facing the air outlet 2 of the air conditioning outdoor unit K to discharge the air blown out from the air outlet 2 to the outside, the radiative cooling membrane W may be arranged in close contact with the front surface of the air conditioning outdoor unit K, as shown in Figure 34, with the exhaust hole 6 corresponding to the air outlet 2.

[0210] In this configuration, for example, the support arm 5 is configured to be extendable and retractable. When unwinding the radiant cooling film W from the storage unit 4 or winding the radiant cooling film W back into the storage unit 4, the support arm 5 is extended to prevent the radiant cooling film W from coming into contact with the outdoor air conditioning unit K. During the cooling operation, the radiant cooling film W is unwinded from the storage unit 4 to cover the upper part of the installation space of the outdoor air conditioning unit K, and then the support arm 5 is shortened to bring the radiant cooling film W into close contact with the front of the outdoor air conditioning unit K.

[0211] Incidentally, although not shown in the diagram, as shown in Figures 30 and 31, when a transparent heat-insulating sheet 7 and a radiative cooling film W are provided to cover the upper part of the installation space of the air conditioner outdoor unit K, the transparent heat-insulating sheet 7 is made to be in close contact with the front surface of the air conditioner outdoor unit K with the sheet-side discharge holes 7A corresponding to the air outlet 2. Alternatively, the radiative cooling film W may be made to cover the upper part of the transparent heat-insulating sheet 7 with the discharge holes 6 in close contact with the upper surface of the transparent heat-insulating sheet 7 with the sheet-side discharge holes 7A corresponding to the air outlet 2 when the cooling is in operation. Furthermore, in winter, when the radiative cooling membrane W was shut off, and the transparent heat-insulating sheet 7 was placed in close contact with the front of the outdoor air conditioning unit K with the sheet-side discharge holes 7A aligned with the air outlet 2, it was found that the air conditioning cost from 8:00 to 16:00 decreased by approximately 5.7% when the heating operation was performed.

[0212] [Another embodiment] The following lists other embodiments. (1) In the above embodiment, an example was given in which the radiative cooling layer CP is provided with a protective layer D, but the embodiment may also be carried out in which the protective layer D is omitted.

[0213] (2) In the above embodiment, when joining multiple radiative cooling membranes W to form canvas, the example was given in which the membrane material E is provided with a membrane material side resin layer Ej and the multiple radiative cooling membranes W are joined by heat welding. However, the membrane material side resin layer Ej may be omitted and the multiple radiative cooling membranes W may be joined by sewing to form canvas.

[0214] (3) When installing the radiative cooling film W in a cooling state that covers the upper part of the installation space of the air conditioner outdoor unit K, it is desirable to configure it as a passage that allows the exhaust air from the air outlet 2 to flow forward, as described in the above embodiment. However, the specific form of the passage that forms the passage that allows the exhaust air from the air outlet 2 to flow forward can be changed in various ways, such as providing a duct that guides the exhaust air from the air outlet 2 so as to penetrate the radiative cooling film W. Furthermore, even when a transparent heat-insulating sheet 7 is provided, the specific form of the passage can be changed in various ways, such as providing the duct so as to penetrate the transparent heat-insulating sheet 7.

[0215] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies hereinafter) can be applied in combination with configurations disclosed in other embodiments, as long as no inconsistencies arise. Moreover, the embodiments disclosed herein are illustrative, and the embodiments of the present invention are not limited thereto, and can be modified as appropriate without departing from the object of the present invention. [Explanation of symbols]

[0216] 1 Outdoor air suction part 7 Transparent heat-insulating sheet 8 Hood A Infrared radiation layer B Light reflection layer CP Radiation cooling layer D Protective layer E Film material Eh Film material body Ej Resin layer on film material side H Radiation surface J Resin material layer K Outdoor unit of air conditioner N Adhesive layer Q Filler S Connection layer W Radiation cooling film

Claims

1. The radiative cooling film is installed in a state where it cools the intake air drawn into the outdoor unit of the air conditioner, The radiative cooling film is mounted in a manner that allows switching between the cooling action state and the cooling stop state in which the intake air is not cooled. A transparent heat-insulating sheet is provided to cover the upper part of the installation space for the outdoor unit of the air conditioner. An air intake air cooling device for an outdoor air conditioning unit, wherein the radiative cooling film covers the upper part of the transparent heat-insulating sheet when the cooling is in operation, and leaves the upper part of the transparent heat-insulating sheet open when the cooling is stopped.

2. The suction air cooling device for an outdoor air conditioning unit according to claim 1, wherein the radiative cooling membrane is installed in a manner that covers the upper part of the installation space of the outdoor air conditioning unit.

3. The radiative cooling film comprises a radiative cooling layer, The radiative cooling layer is configured to include an infrared radiation layer that emits infrared light from a radiation surface, and a light reflection layer positioned on the side of the infrared radiation layer opposite to the side where the radiation surface is located. The infrared radiation layer is a resin material layer made of a polyvinyl chloride resin whose thickness is adjusted to emit thermal radiation energy greater than the absorbed solar energy in the wavelength band from 8 μm to 14 μm. The suction air cooling device for an outdoor air conditioning unit according to claim 1 or 2, wherein the light-reflecting layer comprises silver or a silver alloy.

4. The film thickness of the aforementioned resin material layer is The suction air cooling device for an outdoor air conditioning unit according to claim 3, wherein the thickness is adjusted to have light absorption characteristics such that the wavelength average of the light absorption rate from 0.4 μm to 0.5 μm is 13% or less, the wavelength average of the light absorption rate from 0.5 μm to 0.8 μm is 4% or less, the wavelength average of the light absorption rate from 0.8 μm to 1.5 μm is 1% or less, the wavelength average of the light absorption rate from 1.5 μm to 2.5 μm is 40% or less, and the thickness is adjusted to have thermal radiation characteristics such that the wavelength average of the emissivity from 8 μm to 14 μm is 40% or more.

5. The suction air cooling device for an outdoor air conditioning unit according to claim 3 or 4, wherein the light-reflecting layer has a reflectance of 90% or more at wavelengths of 0.4 μm to 0.5 μm and a reflectance of 96% or more at wavelengths longer than 0.5 μm.

6. The suction air cooling device for an outdoor air conditioning unit according to any one of claims 3 to 5, wherein the light-reflecting layer is composed of silver or a silver alloy and has a thickness of 50 nm or more.

7. The suction air cooling device for an outdoor air conditioning unit according to any one of claims 3 to 6, wherein the light-reflecting layer has a laminated structure of silver or a silver alloy and aluminum or an aluminum alloy located on the side away from the resin material layer.

8. The resin material forming the aforementioned resin material layer is a vinyl chloride resin mixed with a plasticizer. The suction air cooling device for an outdoor air conditioning unit according to any one of claims 3 to 7, wherein the plasticizer comprises one or more compounds selected from the group consisting of phthalates, aliphatic dibasic acid esters, and phosphate esters.

9. The system is configured to include a protective layer between the resin material layer and the light-reflecting layer, The suction air cooling device for an outdoor air conditioning unit according to any one of claims 3 to 8, wherein the protective layer is a polyolefin resin with a thickness of 300 nm or more and 40 μm or less, or a polyethylene terephthalate resin with a thickness of 17 μm or more and 40 μm or less.

10. The suction air cooling device for an outdoor air conditioning unit according to any one of claims 3 to 9, wherein the radiative cooling membrane comprises a membrane material and the radiative cooling layer, and the radiative cooling layer is attached to the outer surface of the membrane material by a connecting layer of adhesive or bonding agent.

11. The suction air cooling device for an air conditioning outdoor unit according to claim 10, wherein the back surface of the membrane material away from the radiative cooling layer is provided with a membrane material side resin layer formed of a vinyl chloride resin.

12. The radiative cooling film is attached to the outdoor unit of the air conditioner to cool the intake air, When the air conditioner outdoor unit is in cooling operation, the radiant cooling film is set to the cooling operation state. During heating operation of the outdoor unit of the air conditioner, the mounting state of the radiant cooling film is switched to a cooling stop state in which the intake air is not cooled. A transparent heat-insulating sheet is provided to cover the upper part of the installation space for the outdoor unit of the air conditioner. A method for cooling an outdoor unit of an air conditioner using suction air, wherein the radiative cooling film covers the upper part of the transparent heat-insulating sheet when the cooling is in operation, and the upper part of the transparent heat-insulating sheet is left open when the cooling is stopped.

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