JP6733010B1 - Cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve cooling efficiency in a cooling device provided with a radiator having wavelength selectivity. A cooling device capable of selectively radiating an electromagnetic wave having a specific wavelength and including a radiator having a concavo-convex structure on its surface. The concavo-convex structure is preferably a structure in which peaks and valleys are arranged alternately and continuously in a predetermined direction. [Selection diagram] Figure 1

Description

The present invention relates to a cooling device.

Conventionally, regarding a cooling and heating device using radiation, the wavelength of infrared radiation to be radiated is controlled, and an infrared ray of a specific wavelength that is easily absorbed by an object to be heated such as a human body is used as a main wavelength of radiation, and directivity of the infrared radiation to be radiated A technique has been proposed in which the heating and cooling efficiency is increased and the heating and cooling efficiency is improved by selectively heating the object to be heated.

Patent Document 1 discloses a technique in which a heat conductive sheet is bent and arranged so as to be in contact with a heat exchange pipe, thereby increasing a contact area with a radiant panel to increase the amount of heat transfer and improving efficiency of cooling and heating.

Further, in Patent Document 2, wavelength-selective radiative cooling can be achieved by the fact that the atmosphere on the earth transmits infrared rays of a specific wavelength without absorbing them, and by a film in which a metal reflective layer is combined with a polymer layer mixed with particles. It is disclosed that this is possible.

Japanese Patent No. 6372004 International publication 2017/151514

However, in the heat conductor having the bent structure described in Patent Document 2, since infrared rays radiated from the heat conductor are absorbed in other parts of the heat conductor, the amount of heat transfer to the outside is reduced, and the heating and cooling are performed. Efficiency is reduced.

The present invention has been made in view of the above, and an object thereof is to improve the cooling efficiency in a cooling device including a radiator having wavelength selectivity.

(1) The present invention is a cooling device (for example, a cooling device described later) that is capable of selectively radiating an electromagnetic wave of a specific wavelength and that includes a radiator (for example, a radiator 3 described later) having an uneven structure on its surface. 1) is provided.

(2) In the invention of (1), in the concavo-convex structure, a mountain portion (for example, a mountain portion 35 described later) and a valley portion (for example, a valley portion 33 described later) are alternately arranged in a predetermined direction. It is a bellows structure, and it is preferable that two surfaces (for example, facing surfaces 34a and 34b, which will be described later) that are opposed to each other and that configure the valley have different wavelength selectivity.

(3) In the invention of (1), the concavo-convex structure is a bellows structure in which peaks and valleys are arranged alternately and continuously in a predetermined direction, and the two surfaces forming the valleys and facing each other The two surfaces have the same wavelength selectivity, and the angles formed by the two surfaces with respect to the surface extending in the predetermined direction (for example, an angle θ described below) are the same, and the angle formed is 75. It is preferably at least 90° and less than 90°.

(4) In the invention of (2) or (3), it is preferable that the wavelength of the electromagnetic wave radiated from at least one of the two surfaces partially includes a wavelength region in which the transmittance of the atmosphere is larger than zero. ..

(5) In the inventions of (2) to (4), it is preferable that both of the wavelengths of the electromagnetic waves emitted from the two surfaces include a part of a wavelength region in which the transmittance of the atmosphere is larger than zero.

(6) In the inventions of (1) to (5), the radiator includes a polymer layer (for example, a polymer layer 31 described later) and a metal reflection layer (for example, a metal reflection layer described below) laminated with the polymer layer. 32), and the polymer layer includes a dispersion medium (for example, a dispersion medium 312 described below) and a plurality of dielectric particles (for example, a dielectric particle 311 described below) dispersed in the dispersion medium. ) And, the dielectric particles are preferably composed of at least one selected from the group consisting of silicon dioxide, calcium carbonate, silicon carbide, zinc oxide, titanium dioxide and alumina.

(7) In the invention of (6), the dispersion medium is at least one selected from the group consisting of 4-methyl-1-pentene polymer, 4-methyl-1-pentene copolymer, polyvinyl fluoride and polyethylene terephthalate. It is preferable that

(8) In the inventions of (1) to (7), it is preferable that the cooling device is installed outdoors, and the radiator is installed so as to radiate upward from a horizontal direction toward outer space. ..

According to the present invention, it is possible to improve cooling efficiency in a cooling device including a radiator having wavelength selectivity.

It is a figure which shows typically the building in which the cooling device 1 which concerns on 1st Embodiment of this invention was installed. It is a figure which shows the cooling device 1 which concerns on this embodiment. It is a graph which shows the infrared transmittance of the gas contained in the atmosphere. It is a figure which shows the cross-sectional structure of the radiator 3 which concerns on this embodiment. It is an appearance perspective view showing an example of radiator 3 concerning this embodiment. It is a figure which shows the advancing direction of the infrared rays radiated from a certain point on the radiator 3. It is a figure which shows the angle (theta) _k which concerns on the infrared radiation from the radiator 3. It is a figure which shows the angle (theta) _k regarding the infrared radiation from the radiator 3, when the wavelength selectivity of the radiator 3 which opposes is the same. FIG. 9 is a diagram showing an angle θ _k related to infrared radiation from the radiator 3 when the wavelength selectivity of the radiator 3 facing each other is different. It is a graph showing the inclination angle θ dependency of the area term. It is a graph showing inclination-angle (theta) dependence of an angle term. It is a graph showing the inclination angle θ dependence of the amount of infrared radiation. It is a figure showing the radiator 103 which concerns on 2nd Embodiment of this invention. It is a figure showing the radiator 203 which concerns on 3rd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

(First embodiment)
FIG. 1 is a diagram showing a usage example in which the cooling device 1 of the present embodiment is installed on a roof of a building. FIG. 2 is a diagram showing the cooling device 1 according to the first embodiment of the present invention.
As shown in FIG. 2, the cooling device 1 according to the present embodiment is configured to include a housing portion 2 and a radiator 3. The cooling device 1 according to this embodiment is used, for example, as a cooling device for a building. Specifically, for example, as shown in FIG. 1, it is installed on a roof of a building or the like and performs radiative cooling toward the sky.

The housing 2 has a structure capable of housing the radiator 3. The material and shape of the housing portion 2 are not particularly limited, but in order to house the radiator 3 to be heated, it is preferable that the housing portion 2 is made of a material having a certain heat resistance such as metal or heat resistant resin. The accommodating portion 2 may be, for example, embedded in a roof, a wall, a ceiling, or the like to be a part of a building, or may be an independent housing.

The radiator 3 radiates the heat energy received from the heat source as an electromagnetic wave (infrared ray in this embodiment) having a certain wavelength region. At this time, if the radiated infrared rays are absorbed by the atmosphere, the temperature around the object to be cooled will rise, and the cooling efficiency will decrease. Therefore, when the thermal energy is radiated by infrared rays, it is preferable that the thermal energy is radiated at a wavelength that is difficult to be absorbed by the atmosphere and is radiated to outer space.

When radiating at a wavelength that does not easily pass through the atmosphere, radiant heat is absorbed by the air around the cooling device during the hot and humid time of day such as summer, and the heat from the hot air is transferred to the device. The effect of is hard to feel. In this respect, when the radiation is not absorbed by the atmosphere but is radiated toward outer space, the amount of heat transferred from the air is small, and the effect of radiation cooling can be felt higher.

FIG. 3 is a graph showing the infrared transmittance of gas contained in the atmosphere. The bottom row is a graph showing the infrared transmittance of the atmosphere.
As shown in FIG. 3, the transmittance of infrared rays in the atmosphere differs depending on the wavelength of the infrared rays. For example, infrared rays having a wavelength of 8 to 13 μm are hardly absorbed by the atmosphere and most of them are transmitted. Such a wavelength range that can pass through the atmosphere is called a window of the atmosphere. Therefore, if infrared rays having a wavelength of 8 to 13 μm are radiated upward from the horizontal, thermal energy can be efficiently emitted to outer space.

The heat source from which the heat energy is released is cooled and the temperature is lowered. If a coolant such as water or gas is used as a heat source for supplying heat to the radiator 3, the coolant cooled to a low temperature by the radiation cooling of the radiator 3 is passed through a heat exchange tube passing through each room of the building to cool the room. After that, the radiator 3 is used to cool the refrigerant having a high temperature again, so that it can be used as a cooling system for a building.

FIG. 4 is a diagram showing a cross-sectional configuration example of the radiator 3 according to the present embodiment.
The radiator 3 includes, for example, as shown in FIG. 4, a polymer layer 31 and a metal reflection layer 32. The polymer layer 31 is configured by dispersing a plurality of dielectric particles 311 in a dispersion medium 312. A desired wavelength selectivity can be obtained by appropriately selecting the particle size and material of the dielectric particles 311 or the physical properties of the dispersion medium.
The dispersion medium 312 is preferably made of a material that can transmit infrared rays having a wavelength of 8 to 13 μm. This is because the thermal energy is efficiently released from the atmospheric window to outer space.

For example, the dielectric particles 311 are preferably made of at least one selected from the group consisting of silicon dioxide, calcium carbonate, silicon carbide, zinc oxide, titanium dioxide, and alumina. The dispersion medium 312 is preferably made of at least one selected from the group consisting of 4-methyl-1-pentene polymer, 4-methyl-1-pentene copolymer, polyvinyl fluoride and polyethylene terephthalate. For example, the dispersion medium 312 can be formed by using TPX ^™ manufactured by Mitsui Chemicals, Inc.
As the structure having wavelength selectivity, for example, in addition to the radiator of this embodiment, a MIM (metal-insulator-metal) structure or a cavity structure can be used.

FIG. 5 is an external perspective view showing an example of the radiator 3 according to the present embodiment.
The radiation efficiency changes depending on the shape of the radiator 3. That is, by providing the radiator 3 with the concavo-convex structure, it is possible to increase the surface area of the radiator 3 and increase the amount of thermal energy to be emitted. However, it is possible that the infrared ray radiated from itself is re-absorbed by having the uneven structure. Therefore, it is preferable that the radiator 3 has a shape and a configuration such that the surface area is increased and the amount of infrared rays emitted from itself is reduced.

Specifically, the radiator 3 of the present embodiment is formed in a bellows shape in which peaks 35 and valleys 33 are alternately arranged in a predetermined direction as shown in FIG. 6 to 9 are cross-sectional views of one valley portion 33 of the bellows structure. Opposing surfaces 34a and 34b of the valley portion 33 are configured symmetrically to each other with respect to a normal line passing through the point O of the OH plane in FIG. 6 and form an angle θ with the OH plane (0°<θ<90°. ). If the length of the orthogonal projection of the OR surface from the top R to the bottom O of one of the facing surfaces 34a and 34b to the OH plane is L, the horizontal distance between the tops R and R of the facing surfaces is 2L. In the present disclosure, this distance is also referred to as the width of the valley portion 33.

FIG. 6 is a diagram showing a traveling direction of infrared rays emitted from a certain point on the radiator 3.
Infrared rays are radiated from each point on the radiator 3. As shown in FIG. 6A, the infrared rays radiated from the surface 34a include a component A that advances toward the air as it is and a component B that advances toward the opposite surface 34b. When the faces 34a and 34b facing each other of the valley portion 33 of the radiator 3 have the same wavelength selectivity, the component B is absorbed by the faces 34b facing each other.

When the wavelength selectivity of the surfaces 34a and 34b facing each other of the valley portion 33 of the radiator 3 is different, as shown in FIG. 6B, the light is reflected and further travels into the air (B1) or the opposite right side. Toward the surface 34a (B2). Compared with the case where the wavelength selectivity of the left and right surfaces of the radiator 3 is the same, the amount of infrared rays radiated into the air increases by the amount of the component B1, so that the cooling efficiency is improved. The component B2 is absorbed by the right side surface 34a.

It should be noted that the ratio of the component absorbed by the facing surface to the component radiated into the air changes depending on the angle θ in FIG. 6. The smaller the angle θ, the smaller the ratio of absorbed components, and the larger the angle θ, the larger the ratio of absorbed components. However, if the angle θ is large, the surface area of the radiator increases, so that the total amount of infrared rays emitted increases. The cooling efficiency needs to be calculated by combining the total amount of infrared rays and the ratio of components radiated in the air.

Here, the total amount of infrared rays that contribute to cooling will be concretely considered by a mathematical formula. The total amount P of infrared rays is represented by the product of the amount of radiation p(T) per unit area, the area term L/cos θ of the radiator 3 and the angle term that is the angular component radiated in the air. Considering in the plane of, the total amount of infrared rays is given by the following equation (1). Note that P(T) indicates that the amount of infrared radiation depends on temperature, and L and θ are defined as shown in FIG.

…（１）

…(1)

The angles θ _ka and θ _kb shown in FIGS. 7A and 7B are the angles formed by the angle component group of infrared rays emitted from a certain point on the surface 34 a of the radiator 3 with the surface 34 a of the radiator 3. Of these, the maximum angle that is not emitted into the air is shown.
Similarly, the angles θ _1α , θ _2α,. ． ． (Α=a, b) are points 1, 2,. ． ． The angle component group of the infrared rays radiated from is the maximum angle of the infrared components not radiated into the air among the angles formed with the surface 34 a of the radiator 3. Of these, FIG. 8 shows components radiated from the surface 34a to the surface 34b, and FIG. 9 shows components reflected from the surface 34b and incident on the surface 34a. Here, points 1, 2,. ． ． If n is set, the radiation from the surface 34a can be more accurately taken into consideration as n is increased. 8 and 9, the surface 34a is divided into five parts, and five points 1 to 5 are illustrated.

Of the angular component group of infrared rays radiated from a certain point on the surface 34a of the radiator 3, the angle component whose angle with the surface 34a of the radiator 3 is larger than θ _k is radiated into the air and contributes to cooling. To do. That is, the meaning of the angle term of the above formula (1) is (angle component larger than θ _k )/(total radiating angular range=180°).

When the angle term is expressed by a mathematical expression, it becomes as shown in Expression (2). The expression (2) is obtained by dividing the surface 34a of the radiator 3 into n pieces, and adding the angles of radiation at the respective points radiated into the air into n→∞. Thereby, the ratio of the component radiated in the air among the infrared rays radiated from each point of the radiator 3 can be expressed as an angle term.

…（２）

…(2)

In addition, the calculation method of the term of the angle component is different when the wavelength selectivity between the left and right surfaces of the radiator 3 is the same or different. When the right and left surfaces of the radiator 3 have the same wavelength selectivity, the components of the emitted infrared rays that are incident on the opposing radiator 3 are absorbed, so that only the components that are directly emitted into the air are included in the angle terms. To consider as. That is, an angle larger than θ _ka shown in FIG. 7A may be considered.

In the case where the right and left surfaces of the radiator 3 have different wavelength selectivity, the components of the emitted infrared rays that are incident on the opposing radiator 3 are reflected. The reflected component is divided into a component that returns to the original radiator 3 and a component that is reflected into the air, but since the former is absorbed, only the latter is considered as an angular term. That is, the sum of the component directly radiated from the original radiator 3 into the air and the component reflected by the opposing radiator 3 into the air is considered as an angle term. At this time, an angle larger than θ _kb shown in FIG. 7B may be considered.

FIG. 10 is a graph showing the inclination angle θ dependency of the area term.
As described above, when considered in the plane of FIG. 6, the area term of the radiator 3 is represented by L/cos θ. Therefore, as θ increases, the area term becomes 1/cos θ times, and therefore increases as shown in FIG. 10 at 0°<θ<90°. Further, the area term when θ=0 is set to 1.

FIG. 11 is a graph showing the inclination angle θ dependency of the angle term.
When θ=0°, that is, when the radiator 3 has a planar structure having no concavo-convex structure, all infrared rays emitted from the radiator 3 are emitted into the air. Therefore, θ _k =0°, and the angle term is 180°/180°=1.

When the right and left surfaces of the radiator 3 have the same wavelength selectivity, the ratio of infrared rays absorbed by the surfaces of the radiator 3 facing each other increases with an increase in θ in the entire range of 0°<θ<90°. , The angle term becomes smaller.

When the right and left surfaces of the radiator 3 have different wavelength selectivity, when 0°<θ≦45°, all infrared rays reflected by the opposing radiator 3 are reflected in the air. All infrared rays emitted from 3 will be emitted into the air. Therefore, θ _k =0°, and the angle term is always 1 in this θ range. When 45°<θ<90°, the angle term becomes smaller as θ increases, as in the case where the left and right surfaces of the radiator 3 have the same wavelength selectivity.

FIG. 12 is a graph showing the inclination angle θ dependence of the amount of infrared radiation.
This is a calculation of the total infrared ray amount P expressed by the equation (1), and is proportional to the product of the area term and the angle term shown in FIGS. The angle term was set to n=5, and the point where the incident angle and the reflection angle were equal was calculated based on the principle of geometrical optics. Further, the radiation amount is set to 1 when θ=0°, that is, when the radiator 3 has a planar structure having no uneven structure.

It can be seen that when the right and left surfaces of the radiator 3 have the same wavelength selectivity, the radiation amount increases in the range of 75°≦θ<90° as compared with the case of θ=0°. Further, when the right and left surfaces of the radiator 3 have different wavelength selectivity, the radiation amount increases with the increase of θ in the entire range of 0°<θ<90°. The larger the θ is, the more the radiation amount increases. Especially, in the range of 75°≦θ<90°, the radiation amount is more than double that in the case where the radiator 3 has a planar structure, and highly efficient radiation is possible. Is.

As described above, according to the cooling device 1 of the present embodiment, infrared rays having a specific wavelength can be radiated, and the cooling efficiency is improved by increasing the surface area by the uneven structure of the radiator. In the present embodiment, the facing surfaces 34a and 34b of the valley 33 are formed symmetrically with respect to the normal line passing through the point O of the OH plane in FIG. 6, but the facing surfaces 34a and 34b of the valley 33 are asymmetrical. It may be formed, and the cooling efficiency is similarly improved.

As an example of the usage of the cooling device 1 of the present invention, as shown in FIG. 1, the cooling device 1 can be attached to the roof of a building 6 to be used as a cooling system 10 for the building. At that time, by installing the photovoltaic power generation panel 7 on the sunny roof of the south side and installing the cooling device 1 on the vacant roof of the north side, the roof space can be effectively used and the power generation and the radiation cooling can be performed at the same time. It can be carried out. Further, if the electric power generated by the panel 7 is used as a power source for circulating the refrigerant, cooling can be performed with higher efficiency.

Further, the radiator 3 has a wavelength selectivity that allows the atmosphere to pass therethrough, and can directly exhaust heat to outer space. That is, the exhaust heat of cooling does not affect the vicinity of the use location of the device.
If the cooling device 1 is introduced in an urban area where the building is overcrowded, it may lead to alleviation of the heat island phenomenon. Furthermore, the cooling device 1 of the present embodiment may be used to form a cold storage system.

Next, a cooling device according to another embodiment of the present invention will be described.

(Second embodiment)
FIG. 13: is a figure showing the radiator 103 which concerns on 2nd Embodiment of this invention.
The cooling device 101 according to the second embodiment of the present invention is different from the first embodiment in the shape of the radiator 3. The radiator 103 according to the second embodiment is configured such that the bellows structure of the radiator 3 is formed by alternately arranging peaks and valleys in a direction orthogonal to the predetermined direction. That is, the quadrangular pyramids are continuously arranged. As a result, the surface area of the radiator 3 is increased, so that the cooling efficiency is further improved. Further, in the lower part of FIG. 13, a cross section of the radiator 103 in a plane that passes through the line segments X ₁ X ₂ and is perpendicular to the bottom surface of the quadrangular pyramid is shown.

(Third Embodiment)
FIG. 14 is a diagram showing a radiator 203 according to the third embodiment of the present invention.
The cooling device 201 according to the third embodiment of the present invention is configured by arranging quadrangular pyramid pyramids instead of quadrangular pyramids in the radiator 103 according to the second embodiment. Also in this form, the surface area of the radiator is increased as compared with the case where the uneven structure is not provided, so that the cooling efficiency is improved. In the lower part of FIG. 14, a cross section of the radiator 203 is shown in a plane that passes through the line segment Y ₁ Y ₂ and is perpendicular to the top and bottom surfaces of the truncated pyramid.
The same effect can be obtained even if the trapezoids are continuously arranged in the continuous direction of the bellows structure in the first embodiment.

The embodiments of the present invention have been described above. The embodiment of the present invention is not limited to this, and improvements and modifications are also included in the present invention. For example, the shape of the radiator may be changed in addition to the second and third embodiments, but the radiation efficiency may be improved by increasing the surface area of the radiator and reflecting by utilizing the difference in wavelength selectivity. For example, it is included in the present invention.

1, 101, 201 Cooling device 2 Housing part 3, 103, 203 Radiator 31 Polymer layer 311 Dielectric particles 312 Dispersion medium 32 Metal reflective layer 33 Valleys 34a, b Faces of valleys 35 Mountains 4 Heat exchange tube 5 Atmospheric windows 6 Buildings 7 Solar panels 10 Cooling system

Claims (6)

A cooling device that is capable of selectively emitting infrared rays of a specific wavelength and that includes a radiator having an uneven structure on its surface ,
The concavo-convex structure is a structure in which peaks and valleys are alternately arranged in a predetermined direction,
The cooling device in which the two surfaces that constitute the valley portion and face each other have different wavelength selectivity. The cooling device according to claim 1, wherein the wavelength of the electromagnetic wave radiated from at least one of the two surfaces partially includes a wavelength region in which the transmittance of the atmosphere is greater than zero. The cooling device according to claim 1, wherein the wavelengths of the electromagnetic waves emitted from the two surfaces include a part of a wavelength region in which the transmittance of the atmosphere is greater than zero. The radiator is configured to have a polymer layer and a metal reflective layer laminated on the polymer layer,
The polymer layer has a dispersion medium and a plurality of dielectric particles dispersed in the dispersion medium,
The cooling device according to claim 1, wherein the dielectric particles are made of at least one selected from the group consisting of silicon dioxide, calcium carbonate, silicon carbide, zinc oxide, titanium dioxide and alumina. The cooling device according to claim 4, wherein the dispersion medium is at least one selected from the group consisting of 4-methyl-1-pentene polymer, 4-methyl-1-pentene copolymer, polyvinyl fluoride and polyethylene terephthalate. .. As well as being installed outdoors,
The cooling device according to claim 1, wherein the radiator is installed so as to radiate upward from a horizontal direction toward outer space.

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