EP4028707A1

EP4028707A1 - Cooling device and method for producing same

Info

Publication number: EP4028707A1
Application number: EP20775204.9A
Authority: EP
Inventors: Mostafa BIGLARI; Christina Kotzur; Moritz Vogel
Original assignee: Trumpf SE and Co KG
Current assignee: Trumpf SE and Co KG
Priority date: 2019-09-09
Filing date: 2020-09-09
Publication date: 2022-07-20
Also published as: CN114521226A; DE102019124110A1; WO2021048177A1; US20220196349A1

Abstract

The invention relates to a cooling device (100) for providing passive radiative cooling, comprising a base substrate and a coating (200) that absorbs light of a specific wavelength and that is arranged on the base substrate. The base substrate is a metal substrate (110).

Description

Cooling device and process for its manufacture

Technical area

The present invention relates to a cooling device and a method for the production thereof. The cooling device is in particular a filling device by means of which passive cooling can be achieved by emitting a heat flow. This is also known as radiation cooling.

State of the art

In order to replace conventional cooling solutions, such as, for example, compression cooling, absorption cooling or the use of cooling water, it is known from the prior art to cool surfaces by means of so-called radiation cooling. The systems according to the prior art make use of the fact that the black body radiation emitted by every warm body can be emitted in such a way that the body is cooled. In particular, the aim is to provide the radiation in the wavelength range of an atmospheric window, in which the atmosphere is particularly permeable to infrared radiation, in such a way that the heat is emitted again, as it were, into space.

This principle has already been used at night in many areas of the world.

Shanhui Fan et al., Nature 2014 "Passive radiative cooling below ambient airtemperature under direct sunlight" describe a 1.8 pm thin coating in which layers of silicon dioxide and hafnium oxide alternate and a highly reflective silver layer is applied on top. Accordingly, the incident sunlight can be reflected by the silver coating and the underlying layers of silicon dioxide and hafnium oxide can absorb the heat entering on their underside and release it again in the form of radiation, the wavelength range of the radiation emitted being between 8 pm and 13 pm, i.e. in the area of an atmospheric window for this infrared radiation, so that the Heat can penetrate the earth's atmosphere and is accordingly emitted into space.

From US 2017/0248381 A1 a structure is known in which plastic films with glass spheres are silver-plated in a vacuum in order to apply a coating in this way.

The known previous approaches focus on providing coatings that can be applied, for example, to solar cells or to glass in order to be able to bring about an increase in the efficiency of the solar cells or an improvement in the room climate in this way.

However, the approaches for the production of a cooling device which is cheap and can be produced in a simple manner in larger areas have so far been lacking.

Presentation of the invention

Starting from the known prior art, it is an object of the present invention to provide an improved cooling device and a simplified production method for such a cooling device.

This object is achieved by a cooling device with the features of claim 1. Advantageous further developments emerge from the subclaims, the present description and the attached figures.

Accordingly, a cooling device is proposed which comprises a base substrate and a coating that is arranged on the base substrate and absorbs light of specific wavelength ranges. According to the invention, the base substrate is a metal substrate.

By providing a cooling device in the manner described, a simplified cooling device can be specified which, due to the structure of the coating on the metal substrate, provides a particularly good heat flow for a body or a medium connected to the metal substrate.

Due to the construction on the metal substrate, it is also possible to build structures directly from the cooling device itself, for example to use the proposed cooling device to build a cooling element such as a housing for a media cooler / radiator. Correspondingly, a roof or a roof can also come directly from the cooling device Roof element are formed so that cooling of the underlying house or the rooms below can be achieved.

By constructing the cooling device on the metal substrate, it can also be achieved that the cooling device itself is particularly easy to manufacture, as can also be seen from the following description of the manufacturing method. In particular, a scalable mass production or a continuous production of the cooling device can be carried out, so that a cost-effective production of larger quantities of the proposed cooling device can be achieved.

Furthermore, the proposed cooling device can be provided in a particularly robust manner, so that it can be used outdoors without any problems and can be exposed to the weather for a few years and can still provide sufficient cooling capacity. It should be pointed out here that the plastic films known from the prior art, in contrast to the proposed cooling device, are only moderately weather-resistant, which can lead to a shorter service life.

The metal substrate is preferably a metal sheet and / or a metal plate and / or a metal band, the metal sheet and / or the metal plate and / or the metal band preferably comprising aluminum or an aluminum alloy or iron or an iron alloy, preferably steel, or copper or a copper alloy , or an aluminum sheet or an aluminum alloy sheet or an iron sheet or an iron alloy sheet or a copper sheet or a copper alloy sheet.

These metals are preferred as a building material and construction material for cooling elements because of their mechanical properties and their manufacturability and processability. In addition, the mass production of cooling devices can be achieved inexpensively with these materials.

Furthermore, the coating of metal substrates with polymers and other metals is possible in mass production and can therefore be implemented in a scalable and cost-effective manner. In addition, coated metal substrates can be processed into cooling elements and other components.

By providing the metal substrate in the form of a metal sheet or a metal plate or a metal band, a structure can be built up which is already mechanically stable in itself and which is suitable for the construction of components, roofs, Cooling elements, etc. can be used. For this purpose, the metal substrate can, for example, already be provided in a curved or geometrically structured shape, such as a corrugated iron structure.

Furthermore, the use of the metal sheet or the metal plate means that production, as can be seen from the production method described below, can be achieved in a simplified manner.

A mirror coating is preferably arranged between the metal substrate and the coating provided thereon, the mirror coating preferably having a high reflectivity at least at wavelengths in the visible range, in particular at wavelengths in a range from 400 nm to 1200 nm, with a silver coating formed as a mirror coating preferably directly on top the metal substrate is arranged between the metal substrate and the coating.

The application of the mirror coating between the metal substrate and the coating enables a highly scalable mirror coating step, since the mirror coating can be applied directly to the metal substrate. This can be achieved, for example, by known and scalable silver-plating processes such as, for example, the use of a galvanic silver-plating process. In contrast to the prior art, in which complex evaporation takes place in a vacuum, the production of the cooling device can be simplified and made scalable.

Furthermore, the reflective coating is well protected against environmental influences due to its arrangement between the metal substrate and the coating, so that the cooling device can be designed to have a correspondingly long service life. Compared to the vapor-coated plastic films known from the prior art, this results in an improvement in the durability of the cooling device.

By providing the high reflectivity in the wavelength range of visible light, it is possible for the sunlight radiated onto the cooling device to be largely reflected, so that it does not contribute, or not significantly, to heating the cooling device. Correspondingly, the cooling device can also be used under solar radiation, so that the proposed cooling device is also particularly suitable for mounting on house roofs, etc. The transparency of the coating at wavelengths in the visible range, in particular at wavelengths in a range from 400 nm to 1200 nm, is preferably at least 80%, preferably above 90% and particularly preferably above 95%.

In this way it can be achieved that the sunlight irradiated on the cooling device shines through the coating, is then reflected on the metal substrate or on the reflective layer or the pre-mirroring, and is then reflected away from the cooling element after passing through the coating again. This means that the cooling device can also be used well when exposed to direct sunlight.

The absorption of the coating at wavelengths in an atmospheric window permeable to IR radiation, in particular at wavelengths from 7 pm to 13 pm, is preferably at least 60%, preferably above 80%, particularly preferably above 90%.

In this way, an absorption and then a subsequent emission of heat, which are given off to the metal substrate by the metal substrate or by the bodies or media adjoining the metal substrate, can be re-emitted by the cooling device in the area of the atmospheric window permeable to the infrared radiation. In this way, radiation cooling can be achieved, since the heat present in the metal substrate is absorbed via the selective absorption of the coating and is then practically radiated into space in the area of the atmospheric window, so that a heat flow takes place away from the cooling device and, accordingly, heat from the metal substrate is radiated.

In this way it can be achieved that the metal substrate or the bodies or media adjoining the metal substrate can be kept at a temperature or brought to a temperature which is below the ambient temperature.

The coating preferably comprises particles and a polymer or a polymer precursor, preferably ceramic particles and a thermoplastic or thermosetting polymer, the particles particularly preferably comprising silicon dioxide and / or hafnium oxide and the polymers preferably comprising polymethyl acrylate, TPX or polymethacrylmethylimide.

A preferred mixing ratio is 1% -15% (percent by weight) of the ceramic particles in the polymer. The ceramic particles preferably have an average particle size (D50) between 1 pm and 20 pm, particularly preferably between 7 pm and 13 pm.

In this way, the above-described behavior of the coating and in particular of the ceramic particles of the coating, namely the absorption of heat or thermal radiation from the metal substrate and the subsequent emission in the range of the wavelengths of the atmospheric window, can be achieved. At the same time, the ceramic particles can be securely integrated through the polymer matrix. The provision of the polymer matrix also leads to a transparency of the coating in the range of the wavelengths of visible light, so that visible light can pass through the coating and can be reflected at the interface to the metal substrate.

The particles and the polymer or the polymer precursor preferably have the same or similar refractive indices at wavelengths in the visible range, in particular at wavelengths from 400 nm to 1200 nm, and the particles and the polymer or the polymer precursor have wavelengths in the atmospheric window, in particular at wavelengths of 7 pm to 13pm, preferably diverging refractive indices.

The refractive indices preferably diverge by less than 10%, preferably less than 5%, in the wavelength range from 400 nm to 1200 nm. In the wavelength range from 7 pm to 13 pm, on the other hand, the refractive indices diverge preferably more than 20%, particularly preferably more than 40%.

In this way, the preferred behavior of the coating, namely the transmission of visible light through the coating to the metal substrate or to a reflective layer arranged on the metal substrate, and the absorption and subsequent emission of radiation in the infrared range can also be achieved.

Correspondingly, by means of the cooling device described above in all of the variants and preferred configurations described, radiation cooling can be achieved in which heat can be removed from the metal substrate by the emission of heat in the infrared range.

As a result of the selective absorption of the coating, a selective release of thermal energy via the cooling device can accordingly be achieved. The coating preferably has an embossing in order in this way to further improve the absorption and emission of thermal radiation. The embossing enables the effective surface to be enlarged in a simple manner.

A further metal layer is preferably arranged between the metal substrate and the reflective layer, the metal layer comprising zinc or a zinc alloy or aluminum or an aluminum alloy or tin or a tin alloy. In this way, corrosion protection can be provided in particular for the metal substrate.

The object set above is also achieved by a method for producing a cooling device having the features of claim 10. Preferred developments result from the present description, the figures and the subclaims.

Accordingly, a method for producing a cooling device, preferably for providing passive radiation cooling, is proposed, comprising the steps of providing a metal substrate, preparing the metal substrate for subsequent processing and coating the metal substrate with a coating that absorbs light in certain wavelength ranges.

In this way, a cooling device can be manufactured easily and for mass production.

Before coating the metal substrate, a reflective layer is preferably provided on the metal substrate and the coating is applied to the reflective layer, the reflective layer preferably being produced by applying a silver plating to the metal substrate.

The application of the reflective layer and in particular the silver plating takes place particularly preferably by galvanic or chemical processes. The galvanic process for applying or coating the reflective layer is particularly scalable, cost-effective and flexible. In particular, the thickness of the deposited material can be controlled very well, the method can still be carried out at atmospheric pressures and in a simple environment and the method can be combined with other method steps for producing the cooling device in a continuous method.

The production of the cooling device can thus be designed to be particularly scalable and mass production of the proposed cooling device becomes possible. Before applying the reflective layer, further coatings can be applied to the metal substrate. For example, a steel substrate with a galvanizing, a coating with aluminum or a tinning for corrosion protection and / or to improve the interaction and / or adhesion with the reflective layer can be applied.

The advantages already described above for the cooling device are achieved by applying the reflective layer.

The metal substrate is preferably cleaned in a cleaning device before coating and / or polished in an electropolishing device before coating.

This preparation of the metal substrate simplifies the subsequent processing and a surface of the metal substrate can be provided which supports the optical properties.

A coating can be applied particularly easily to at least one side of the metal substrate by means of a roller application device. The coating can preferably also be applied to at least one side of the metal substrate by means of a doctor blade application device or an extrusion device or a laminating device.

The metal substrate is preferably provided in the form of a metal strip, preferably in the form of an aluminum strip or a steel strip or a copper strip, and a connecting device for connecting successive metal strips is preferably provided.

The provided metal substrate can preferably already comprise a coating, such as, for example, corrosion protection, to which the reflective layer is then applied.

In a preferred development, the metal strip coated with the coating is embossed in an embossing device.

The metal substrate is preferably provided in the form of a coated metal strip, preferably in the form of a strip with a zinc coating or a coating with a zinc alloy, or with an aluminum coating or a coating with an aluminum alloy, or with a tin coating or a coating with a tin alloy, or with a magnesium coating or a coating with a magnesium alloy. Brief description of the figures

Preferred further embodiments of the invention are illustrated by the following

Description of the figures explained in more detail. Show:

FIG. 1 shows a schematic sectional illustration through a cooling device according to the present disclosure;

Figure 2 is a schematic representation of a production line for producing a

Cooling device and for carrying out a manufacturing method for manufacturing a cooling device;

FIG. 3 shows a schematic representation of an alternative manufacturing method for manufacturing a cooling device;

FIGS. 4A to 4C show a schematic representation of a further alternative production method for producing a cooling device; and

FIG. 5 shows a schematic illustration of yet another alternative manufacturing method for manufacturing a cooling device.

Detailed description of preferred exemplary embodiments

Preferred exemplary embodiments are described below with reference to the figures. Identical, similar or identically acting elements are provided with identical reference symbols in the different figures, and a repeated description of these elements is in some cases dispensed with in order to avoid redundancies.

FIG. 1 shows a schematic sectional illustration through a cooling device 100, the cooling device 100 comprising a metal substrate 110 to which a coating 200 absorbing light of specific wavelength ranges is applied.

The cooling device 100 provides passive radiation cooling.

The coating 200 can comprise a polymer matrix 210 in which ceramic particles 220 are embedded. The metal substrate 110 is preferably a metal sheet or a metal plate to which the coating 200 is applied. The metal sheet or the metal plate can particularly preferably be provided in the form of an aluminum structure or a steel structure or a copper structure, for example in the form of a sheet metal or a plate or a metal strip. The thickness of the metal substrate is preferably between 10 pm and 2 mm, particularly preferably between 10 pm and 0.5 mm.

The ceramic particles 220 can be provided, for example, in the form of silicon dioxide or hafnium oxide, the ceramic particles preferably having an average particle size (D50) between 1 pm and 20 pm, preferably between 7 pm and 13 pm.

The polymer matrix 210 can be, for example, a thermoplastic polymer or a thermosetting polymer. Preferred polymers are polymethyl acrylate, TPX or polymethacrylmethylimide.

The refractive index of the ceramic particles 220 and the polymer matrix 210 is particularly preferably selected such that the refractive indices of the ceramic particles 220 and the polymer matrix 210 are essentially the same in the visible wavelength range, i.e. in a range between 400 nm and 1200 nm.

In other areas in other wavelength ranges, however, in particular in the area of an atmospheric window through which energy can be emitted into space in the infrared range, in particular in a wavelength range between 7 pm and 13 gm, the refractive indices of the ceramic particles 220 and the polymer matrix 210 are preferred diverging and particularly preferably very different. The strong light diffusion in the wavelength range from 7pm to 13pm causes the desired high emmisivity in this range. In the exemplary embodiment shown in FIG. 1, a reflective layer 120 is provided between the coating 200 and the metal substrate 110, which can be implemented, for example, in the form of a pre-mirroring. In the exemplary embodiment shown, the reflective layer 120 is provided in the form of a silver plating, it being possible for the silver plating to be provided, for example, by applying a thin silver plating layer.

The silver plating layer is preferably galvanized or provided. In order to reduce the costs of producing the silver-plating layer, the silver-plating layer is preferably provided in a layer thickness of less than 10 μm, particularly preferably a layer thickness of less than 500 nm. The reflective layer 120 is preferably designed in such a way that it provides a high degree of reflection at least in the range of the visible wavelengths, that is to say between 400 nm and 1200 nm.

The proposed cooling device 100 makes it possible, on the one hand, to achieve increased absorption and thus also increased subsequent emission of energy in the area of the atmospheric window, so that radiation cooling can be provided by means of which thermal energy is emitted into space in the area of the atmospheric window can be in order to achieve radiation cooling in this way.

Furthermore, the increased transmission of the coating 200 in the visible range simultaneously results in a reflection of the sunlight falling on the cooling device 100 such that the visible sunlight hits through the coating 200, then hits the reflective layer 120, and then again through the coating 200 to be reflected through and is accordingly reflected away from the metal substrate 110 and is thus also reflected away from the cooling device 100.

Correspondingly, heat, which is to be given off as black body radiation or as thermal radiation and which is introduced into the metal substrate 110, can also be emitted through the atmospheric window when exposed to sunlight, the radiation of the visible light from the sun correspondingly being irrelevant or only of minor importance plays.

Due to the ceramic particles 220 and in particular the provision of the ceramic particles 220 in the form of silicon dioxide or hafnium oxide, the heat provided there can be withdrawn from the metal substrate 110 and released again by the ceramic particles in the wavelength range of the atmospheric window. Correspondingly, there can always be an emission of heat from the metal substrate 110. The occurrence of solar radiation causes no or no special supply of heat to the metal substrate 110.

From the metal substrate 110 with the correspondingly applied coating 200 it can thus be achieved that, for example when building a roof or when building a heat exchanger, the medium connected to the metal substrate 110, for example air or a cooling medium, is kept at a temperature which is below the ambient temperature lies. In this way, passive radiation cooling can be provided. By using the metal substrate 110, a stable structure can be built up from the cooling device 100, for example a self-supporting structure in the sense that a cooling element in the form of a radiator or a cooling element in the form of a roof or a roof element can be formed from the cooling device 100, for example . Due to the use of the metal substrate, such an element can be bent or assembled directly from the cooling device. The cooling device itself is easy to process and can be processed in the same way as metal sheets or metal plates are to be processed. In particular, the cooling device can be welded, sawed, drilled, ground, glued, etc., in order to enable the construction of structures directly with the cooling device.

In FIG. 2, a production line 1 for producing a cooling device, as described in relation to FIG. 1, is shown schematically. In the following, the production line 1 will be described taking into account the individual processing positions which are denoted by the letters.

An unwinding device A is provided at the first position, into which a roll 30 or a “coil” with a rolled up metal sheet or metal strip can be loaded, and through which the metal sheet wound on this roll 30 can be unwound for further use in the production line 1 .

In a preferred embodiment, which produces a cooling device 100 with the properties and advantages described above, the metal sheet can be provided, for example, in the form of an aluminum sheet, which can be rolled up on the roll 30, inserted into the unwinding device A and accordingly unwound by the unwinding device A. can.

Following the unwinding device A, a connecting device B is provided downstream, by means of which a previous metal sheet can be connected to a subsequent metal sheet. This is important, for example, if continuous production is to be achieved and, accordingly, after the complete processing of a previous roll 30 of sheet metal that was used in unwinding device A, a subsequent roll 30 of sheet metal is to be unwound from unwinding device A and accordingly that The end of the sheet metal of the previous roll 30 is to be connected to the beginning of the following roll 30. In this way, by joining metal tracks, a quasi-endless sheet metal can be provided, whereby a continuous manufacturing process can be achieved accordingly. The connection of the end of the metal strip unwound in the unwinding device A with the beginning of a metal strip inserted thereon in the unwinding device A can be achieved, for example, by welding the end of the strip to the new beginning of the strip. Such a connecting device B is also referred to as a stitching / welder.

At the subsequent processing position, a cleaning device C is provided, by means of which the metal strip 10 unwound from the unwinding device A is cleaned. The metal strip 10 can pass through a cleaning bath 32 in the cleaning device C in order to achieve cleaning of the metal strip 10 in this way. The cleaning can for example achieve dust removal and degreasing of the metal strip 10. In this way, the reflectivity of the metal strip 10 is improved and the subsequent processing steps, such as coating in particular, can be prepared and improved.

By cleaning the metal strip 10, the surface of the metal strip 10 can also be homogenized, so that the basis for a consistent quality of the coating and further processing steps is laid.

The cleaning bath 32 can be provided, for example, in the form of a suitable acid and / or suitable surfactants and / or a suitable lye and / or other cleaning media, which are adapted to both the material of the respective metal strip 10 and the expected soiling of the metal strip 10. Several cleaning baths can also be run through one after the other.

Following the cleaning bath 32 or following the cleaning device C, a storage device D is provided in the illustrated embodiment of the production line 1, in which the metal strip 10 is stored with the formation of loops 12. The loop-shaped guidance of the metal strip 10, which leads to the loops 12, is achieved in the storage device D by rollers 34 and counter rollers 36, which are each arranged at a distance from one another perpendicular to the conveying direction.

Correspondingly, a predetermined length of the metal strip 10 can be stored or taken up in the loops 12 in the area of the storage device D, so that in the event that the roll 30 inserted in the unwinding device A has ended, a new roll 30 is inserted into the unwinding device A. and then the end of the previous tape is to be connected to the beginning of the new tape in the connecting device B, but there is still a continuous tape flow after the Storage device D can be achieved in that the metal strip 10 received in the form of a loop in the loops 12 of the storage device D can be continuously guided into the downstream areas of the production line 1.

For this purpose, in the event that the connecting device B has to connect a tape end to a new tape beginning, the metal tape 10 is held in the area of the connecting device B and the metal tape 10 wound in the loops 12 is moved onto the rollers 34 by a movement of the counter rollers 36 to released for the downstream processing steps.

The number of loops 12 shown in FIG. 2 in the storage device D can, depending on the flow rate of the metal strip 10 and depending on the time requirement in the area of the connecting device B, with a larger number of loops or a smaller number of loops and a greater distance between two opposite ones Rollers 34, 36 or a smaller distance between two successive rollers 34, 36 can be adjusted so that, taking into account a corresponding safety margin, a continuous flow of the metal strip 10 downstream of the storage device D can be guaranteed during normal operating conditions.

Following the storage device D, an electropolishing device E is provided, in which the metal strip 10 discharged from the storage device D passes through a polishing bath 38 in which an electropolishing takes place. The electropolishing in the electropolishing device E enables the surfaces of the metal strip 10 to be improved even further and, for example, to provide a high degree of reflection on the surface of the metal strip 10 treated in the electropolishing device E.

The electropolishing in the electropolishing device E takes place in a manner known per se by means of an electrochemical removal process with an external power source. The electrolyte used for this is again matched to the material of the metal strip 10 in such a way that the desired result of a metal strip 10 polished in this way is achieved in the electropolishing process in the electropolishing device E. Depending on the material used for the metal strip 10, the electrolytes to be used are then different.

In the electropolishing process, the metal on the surface of the metal strip 10 is removed anodically, so that the metallic workpiece in the form of the metal strip 10 forms the anode of an electrochemical cell. Subsequent to the electropolishing device E, the cleaned and polished metal strip 10 is immersed in a silver plating device F, which has a silver plating bath 40, and provided with a silver plating therein. A reflective layer can correspondingly be applied to the metal strip 10 by means of the silvering device F.

The silver plating or the reflective layer which is applied to the metal strip 10 is in turn dependent on the material properties of the metal strip. In the silver plating device F and in the silver plating bath 40 of the silver plating device F, for example, in a preferred exemplary embodiment, the metal strip 10 can be immersed in a silver electrolyte, for example potassium silver cyanide, a silver coating then being deposited on the surfaces of the metal strip 10 by applying an electrical voltage. In other words, the metal strip 10 is subjected to electroplating in order to obtain a corresponding electroplated coating of silver.

The process step of silvering can also be omitted if the surface quality of the metal strip 10 polished in the electropolishing device E is correspondingly high. In other words, the silver plating can be omitted if the surface provided by the cleaned and polished metal strip 10 is already sufficiently reflective for the visible sunlight. Whether this is the case can also depend on the material used for the metal strip 10.

In a priming device G following the silvering device F, a primer is applied to at least one side of the metal strip 10, the priming device G being provided by means of a roller application device 42, by means of which the primer is applied to the underside of the metal strip shown in FIG 10 can be applied.

The primer serves to improve the application behavior or the adhesion between the coating to be applied later and the mirrored metal strip 10. Here, too, depending on the materials used and in particular on the material applied in the silvering device F, the primer can be selected so that the subsequent application of the coating is easily possible.

Subsequent to the priming device G, a curing device H is provided, by means of which the previously applied primer is cured. This can be achieved, for example, in that a curing oven 44 is provided in the curing device H so that thermal curing of the primer can be achieved. Following the curing device H, the metal strip 10, which is now mirrored and provided with a cured primer at least on one side, then passes through a coating device I, in which a coating is applied to the side of the metal strip 10 provided with the mirror and the primer by means of a further roller application device 46.

The coating, which is applied to the metal strip in the coating device I by means of the roller application device 46, can be, for example, a mixture of ceramic particles such as silicon dioxide particles (SiO 2) and a precursor of a thermosetting polymer.

The polymer and the ceramic particles preferably have similar refractive indices in the visible wavelength range, whereas the refractive indices of these materials preferably differ significantly in the area of the atmospheric window, i.e. wavelengths between 8 and 10 micrometers.

Subsequent to the coating device I, the metal strip 10 provided with the coating passes through a coating hardening J, in which, for example, a hardening oven 48 is provided. In other words, the metal strip 10 provided with the coating in the coating device 1 now passes through a curing oven 48, by means of which the coating and in particular the polymer can cure.

Subsequent to the hardening of the coating J, an embossing device K can be provided, which applies an embossing to the metal strip 10 provided with the coating by means of two embossing rollers 50.

By applying a corresponding structure, the cooling performance of the cooling device in the form of the metal strip 10 provided with the coating can be further improved and the optical properties of the surface can thereby be adapted to the respective application. An output storage device L in turn serves to place coated metal strip 10 around rollers 52 and counter-rollers 54 in loops 14 in order to be able to receive the metal strip 10 in a continuous process when a tape reel 58 is completely wound up in a subsequent winding device N, and must be removed from the winding device N again in order to provide space for a new roll 58. In order to separate the metal strip 10 when the desired roll thickness of the roll 58 has been reached in the winding device N or the desired length of strip has been wound onto the roll 58, a separating device M is provided, which cuts through the metal strip 10 with a corresponding knife 56 enables.

By means of the production line 1 it is accordingly possible to guide a metal strip from an unwinding device A through a cleaning bath, a polishing bath and a silvering bath in order to then provide at least one side of the metal strip 10 with a coating. The coating has a selective absorption in that it has an absorption in the atmospheric window of, for example, 7-13 micrometers wavelength, which is above 60 percent, preferably above 80 percent, particularly preferably above 90 percent. At the same time, the transparency of the coating in the visible wavelength range between 400 nm and 1200 nm is above 80 percent, preferably above 90 percent, particularly preferably above 95 percent.

In this way it can be achieved that light in the visible range is reflected on the mirror coating, whereas light in the area of the atmospheric window is absorbed by the coating and then emitted again.

In the production line 1, the cooling device 100 produced in this way can accordingly be produced continuously and — quasi — in an infinitely long form. Accordingly, it is possible to produce structures in very different dimensions in one piece from the cooling device 1 produced by means of the production line 1. In addition, inexpensive mass production can be achieved by means of which the cooling device can be widely used.

In the alternative embodiment shown in FIG. 3, instead of the continuous production of a metal strip described in relation to FIG. 2, individual metal plates 14 can now also be coated in FIG.

Here, for example, a pretreatment A ′ is carried out in a first step and an uncoated metal plate 14 is transported, for example, on a roller table 60, and cleaned and pretreated. For example, the metal plate 14 can also be polished or electropolished. A reflective layer can then also be applied. In the second step, a coating B ′ is then carried out, the coating being applied to one side of the metal plate 14 by means of a roller application device 46. The coating can be the mixture, already described for FIG. 2, of a thermosetting polymer or a thermosetting polymer matrix and ceramic particles, for example in the form of silicon dioxide.

After the coating in step B, the metal plate 14, which is then provided with the coating, is brought into a curing oven 48 for curing C ‘in order to cure there, in a manner similar to that described for FIG.

In a further embodiment, instead of a thermosetting polymer or a thermosetting polymer matrix, a thermoplastic polymer which is mixed with ceramic particles can also be applied for the coating.

This thermoplastic polymer can, as shown for example in FIG. 4A, be applied to a metal strip 10 pretreated in a pretreatment A ″ for coating B ″ in a hot, molten state, with the polymer then either being able to be spread, being sprayed on Metal tape can be dipped into the hot polymer, or the polymer can be extruded.

The thermoplastic polymer applied in this way can then cure by cooling, for example by cooling using fans 62 or by cooling rollers 64 shown in FIG. 3B, or by spraying a cooling medium from cooling nozzles 66, as shown in FIG. 4C.

In a further preferred embodiment, as shown in FIG. 5, an already prepared coating film 70 can be laminated onto the prepared metal strip 10. The metal strip 10 can be cleaned, polished and provided with a reflective layer before the coating film 70 is laminated on.

The coating film 70 is brought together with the metal strip 10, preferably in a laminating roller 72, in such a way that it is securely connected to the metal strip 10 by the rolling step or by further mechanical merging.

The coating film 70 can already be pre-produced in this way and accordingly also comprise a polymer matrix in which the ceramic particles are introduced. In order to improve the stability and longevity of the polymer coating, several steps of connecting the metal strip 10 or metal plates 14 with the polymer can be carried out, so that correspondingly several layers of the polymer applied to one another are connected to the metal strip. In further advantageous embodiments, the curing of a polymer can also be achieved, for example, by irradiating with ultraviolet light.

As far as applicable, all of the individual features shown in the exemplary embodiments can be combined with one another and / or exchanged without departing from the scope of the invention.

Reference list

1 production line 10 metal band 12 loop 14 metal plate

100 cooling device 110 metal substrate 120 reflective layer 200 coating 210 polymer matrix

220 ceramic particles 30 roll

32 Cleaning bath 34 Roller 36 Counter roller

38 Polishing bath 40 Silver plating bath 42 Roller application device 44 Curing oven 46 Roller application device

48 curing oven 50 embossing roller 52 roller 54 counter roller 56 knife

58 Roller 60 Roller table 62 Fan 64 Cooling roller 66 Cooling nozzle

70 Coating film 72 Laminating roller A Unwinding device B Connecting device C Cleaning device D Storage device E Electropolishing device F Silver plating device G Priming device H Curing device I Coating device J Coating curing K Embossing device L Output storage device M Separating device N Winding device A ', A “Pretreatment B', B“ Coating C ', C “curing

Claims

Expectations

1. Cooling device (100) for providing passive radiation cooling, comprising a base substrate and a coating (200) which is arranged on the base substrate and absorbs light of specific wavelength ranges, characterized in that the base substrate is a metal substrate (110).

2. Cooling device according to claim 1, characterized in that the metal substrate (110) is a metal sheet and / or a metal plate and / or a metal band, the metal sheet and / or the metal plate and / or the metal band preferably being aluminum or an aluminum alloy or iron or an iron alloy, preferably steel, or copper or a copper alloy, or an aluminum sheet or a sheet made of an aluminum alloy or an iron sheet or a sheet made of an iron alloy or a copper sheet or a sheet made of a copper alloy.

3. Cooling device according to claim 1 or 2, characterized in that a reflective layer (120) is arranged between the metal substrate (110) and the coating (200), the reflective layer (120) preferably having a high reflectivity at least at wavelengths in the visible range, in particular at wavelengths in a range from 400nm to 1200nm, a silver plating formed as a reflective coating preferably being arranged as a reflective layer (120) directly on the metal substrate (110) between the metal substrate (110) and the coating (200).

4. Cooling device according to one of the preceding claims, characterized in that the absorption of the coating (200) at wavelengths in an atmospheric window permeable to infrared radiation, in particular at wavelengths from 7pm to 13pm, at least 60%, preferably above 80%, in particular preferably above 90%.

5. Cooling device according to one of the preceding claims, characterized in that the transparency of the coating (200) at wavelengths in the visible range, in particular at wavelengths in a range from 400 nm to 1200 nm, at at least 80%, preferably above 90% and particularly preferably above 95%.

6. Cooling device according to one of the preceding claims, characterized in that the coating (200) comprises particles (220) and a polymer (210) or a polymer precursor, preferably ceramic particles and a thermoplastic or thermosetting polymer, the particles particularly preferably silicon dioxide or Hafnium oxide and the polymers preferably comprise polymethyl acrylate, TPX or polymethacrylmethylimide, a particularly preferred mixing ratio of 1% -15% (percent by weight) of the ceramic particles in the polymer being preferred.

7. Cooling device according to claim 6, characterized in that the particles (220) and the polymer (210) or the polymer precursor have the same or similar refractive indices at wavelengths in the visible range, in particular at wavelengths from 400nm to 1200nm, and the particles and the polymer or the polymer precursor have diverging refractive indices at wavelengths in the atmospheric window, in particular at wavelengths from 7pm to 13pm.

8. Cooling device according to one of the preceding claims, characterized in that the coating (200) has an embossing.

9. Cooling device according to one of the preceding claims, characterized in that a further metal layer is arranged between the metal substrate (110) and the reflective layer (120), the metal layer comprising zinc or a zinc alloy or aluminum or an aluminum alloy or tin or a tin alloy.

10. A method for producing a cooling device (100), preferably for providing passive radiation cooling, comprising the steps:

Providing a metal substrate (110);

Preparing the metal substrate (110) for subsequent processing;

Coating the metal substrate (110) with a coating (200) which absorbs light of specific wavelength ranges.

11. Method according to claim 10, characterized in that before the coating of the metal substrate (110) a reflective layer (120) on the metal substrate (110) is provided and the coating (200) is applied to the reflective layer (120), the reflective layer (120) preferably being produced by applying a silver plating to the metal substrate (110).

12. The method according to claim 10 or 11, characterized in that the metal substrate (110) is cleaned in a cleaning device (C) before coating and / or is polished in an electropolishing device (E) before coating.

13. The method according to any one of claims 10 to 12, characterized in that the coating (200) is applied to at least one side of the metal substrate (110) by means of a roller application device (46) or a doctor blade application device or an extrusion device or a laminating device.

14. The method according to any one of claims 10 to 13, characterized in that the metal substrate (110) is provided in the form of a metal band (10), preferably in the form of an aluminum band or an iron band or a copper band or a band made of an aluminum alloy or a band made of an iron alloy or a strip made of a copper alloy, and preferably a connecting device (B) for connecting successive metal strips (10) is provided.

15. The method according to any one of claims 10 to 14, characterized in that the metal strip (10) coated with the coating (200) is embossed in an embossing device (K).

16. The method according to any one of claims 10 to 15, characterized in that the metal substrate (110) is provided in the form of a coated metal strip (10), preferably in the form of a strip with a zinc coating or a coating with a zinc alloy, or with an aluminum coating or a coating with an aluminum alloy, or with a tin coating or a coating with a tin alloy, or with a magnesium coating or a coating with a magnesium alloy.