KR20220124954A - Temperature sensitive and color expression smart radiative cooling device - Google Patents

Abstract

The present invention relates to a temperature sensitive and color type smart radiant cooling device, which uses nanofiber having a function of changing an expression color and a smart radiation cooling function of naturally controlling the cooling and heating according to external temperature, and a method for cooling or warming an object by using the temperature sensitive and color type smart radiant cooling device.

Description

TEMPERATURE SENSITIVE AND COLOR EXPRESSION SMART RADIATIVE COOLING DEVICE

The present application provides a temperature-sensitive and color-type radiation cooling device, and the temperature-sensitive smart radiation cooling device, using a nanofiber having a smart radiation cooling function that naturally controls heating and cooling according to the external temperature and a function of changing the expression color. It relates to a method of cooling or warming an object used.

A radiant cooling device is a material that cools itself down to the ambient temperature even under sunlight without external energy inflow. The presence of such cooling devices as helpful could have a major impact on the global energy industry.

Because high solar reflectance is important for radiative cooling, most of the radiation cooling materials of the prior art are designed to include a silver thin film of 100 nm or more. In this case, not only is it difficult to use it as a fabric, but also a problem of causing glare due to strong specular reflection may occur due to the nature of the silver mirror. Therefore, to avoid this, radiation cooling materials using scatterers such as nanoparticles have been studied, but most of them must be used in the form of paint or airgel, so there are points to be complemented in relative durability and flexibility (International Patent Publication No. WO2019/152952) . In addition, there is a problem in that it is difficult to realize a radiation cooling material using a scattering body as a smart radiation cooling device because there are few scattering-type structures capable of smart switching of heating and cooling according to the external temperature.

In order to solve the above problems, the present application relates to a temperature-sensitive and color-type radiation cooling device using nanofibers that enable natural heating and cooling according to the external temperature without additional scatterers, and at the same time the expression color changes.

However, the problems to be solved by the present application are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

A first aspect of the present application provides a temperature-sensitive and color-type radiant cooling device, comprising a nanofiber-containing nanofiber structure, having a radiative cooling function and a color expression function.

A second aspect of the present application provides a method for cooling or warming an object using the temperature-sensitive and color-type radiant cooling device according to the first aspect.

The temperature-sensitive and color-type radiation cooling device according to the embodiments of the present application scatters sunlight without using an additional scatterer by using a fiber structure having a radiation cooling function and a color expression function, and the thickness of the nanofiber structure and the According to the volume ratio of nanofibers, mid-infrared rays can be transmitted or blackbody radiation can be transmitted, so it can be used as a radiation cooling material.

The temperature-sensitive and color-type radiation cooling device according to the embodiments of the present application can be used as a radiation cooling material for water tanks, buildings, automobiles, solar panels, windows, etc. that require smart cloth and flexible materials to implement a radiation cooling function. There is this. In addition, the temperature-sensitive and color-type radiation cooling device can exhibit a more aesthetically superior effect by including a thermal pigment in the nanofiber so that the smart cloth and the radiation-cooling material implement a color.

The temperature-sensitive and color-type radiation cooling device according to the embodiments of the present application includes a temperature-sensitive pigment that changes color according to the external temperature in the nanofiber, so that the color changes according to the external temperature and the radiative cooling function is exhibited, so that the temperature-sensitive It has a characteristic that can be used as a type smart radiant cooling material.

1 is a graph for explaining the principle of implementation of a radiative cooling device, a) AM1.5 solar intensity spectrum; and b) the atmospheric absorption spectrum in the mid-infrared (MIR).
2A is a graph showing the mid-infrared refractive index of polydimethylsiloxane (PDMS).
2B is a graph showing the mid-infrared refractive index of polyimide (PI).
2C is a graph showing the mid-infrared refractive index of polymethyl methacrylate (PMMA).
3a is a graph showing the average mid-infrared (8 μm to 13 μm) transmittance according to the thickness and volume fraction of the nanofiber structure (woven type) including the PDMS fiber in an embodiment of the present application .
3b is a graph showing the average mid-infrared (8 μm to 13 μm) transmittance according to the thickness and volume fraction of the nanofiber structure (woven type) including the PI fiber, in an embodiment of the present application .
3c is a graph showing the average mid-infrared (8 μm to 13 μm) transmittance according to the thickness and volume fraction of the nanofiber structure (woven type) including the PMMA fiber, in an embodiment of the present application .
Figure 4, in one embodiment of the present application, according to the radius of the PDMS nanofibers, a) sunlight scattering efficiency spectrum; and b) a graph showing the mid-infrared scattering efficiency spectrum.
Figure 5, in one embodiment of the present application, according to the radius of the PMMA nanofibers, a) sunlight scattering efficiency spectrum; and b) a graph showing the mid-infrared scattering efficiency spectrum.
6 is a diagram showing a transmissive nanofiber structure implemented by forming the volume ratio of nanofibers to be 10% or less in one embodiment of the present application.
7 is a diagram showing an absorption/radiation type nanofiber structure implemented by forming a volume ratio of nanofibers in excess of 10% in one embodiment of the present application.

Throughout this specification, when a part is “connected” with another part, it includes not only the case of “directly connected” but also the case of “electrically connected” with another element interposed therebetween. do.

Throughout this specification, when a member is said to be located “on” another member, this includes not only a case in which a member is in contact with another member but also a case in which another member is present between the two members.

Throughout this specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated. As used throughout this specification, the terms “about,” “substantially,” and the like are used in a sense at or close to the numerical value when the manufacturing and material tolerances inherent in the stated meaning are presented, and are intended to enhance the understanding of the present application. To help, precise or absolute figures are used to prevent unfair use by unscrupulous infringers of the stated disclosure.

As used throughout this specification, the term “step of (to)” or “step of” does not mean “step for”.

Throughout this specification, the term “combination(s)” included in the expression of the Markush form means one or more mixtures or combinations selected from the group consisting of the components described in the expression of the Markush form, It means to include one or more selected from the group consisting of the above components.

Throughout this specification, reference to “A and/or B” means “A or B, or A and B”.

Throughout this specification, “sunlight” refers to electromagnetic waves that enter from the sun and include ultraviolet light, visible light, and near-infrared light (0.3 μm to 4 μm).

Throughout the present specification, "mid-IR (MIR)" refers to electromagnetic waves having a wavelength of 8 μm to 13 μm that the atmosphere does not absorb among infrared rays radiated by a black body by an object at room temperature.

Hereinafter, embodiments and examples of the present application will be described in detail with reference to the accompanying drawings. However, the present application may not be limited to these embodiments and examples and drawings.

A first aspect of the present application provides a temperature-sensitive and color-type radiant cooling device, comprising a nanofiber-containing nanofiber structure, having a radiative cooling function and a color expression function.

Referring to FIG. 1, the radiative cooling function is self-reflecting most of the incident solar radiation (300 nm to 4 μm) and absorbing and emitting most of the mid-infrared wavelength (8 μm to 13 μm). It means that a cooling function can be implemented (FIG. 1a). In addition, since the wavelength of 8 μm to 13 μm has high atmospheric transmittance, the mid-infrared black body radiation emitted by the object can reach the universe (FIG. By doing this, the object can be cooled without energy consumption. Therefore, the radiation cooling function of the nanofiber structure can be implemented by designing the nanofiber structure to reflect/scatter sunlight from the outside and be transparent to mid-infrared rays (high transmittance). Alternatively, the radiation cooling function of the nanofiber structure may be implemented as the nanofiber structure is designed to reflect/scatter sunlight from the outside, absorb mid-infrared rays and radiate blackbody (low transmittance).

In one embodiment of the present application, the nanofiber structure includes a first space including the nanofiber; and a second space other than the first space. Specifically, the second space may include air or vacuum.

In one embodiment of the present application, the nanofiber may include a thermosensitive pigment. Specifically, the thermal pigment may include a leuco dye.

In one embodiment of the present application, the nanofiber structure may be a woven or tangled network type. Specifically, the nanofiber structure may be in the form of a material in which nanofibers of several hundred nanometers in diameter are formed like a fabric or in a randomly tangled form, and a thermal pigment may be added thereto. Accordingly, the nanofiber structure may have a color expression function as well as a radiative cooling function. The added nanofiber of the thermosensitive pigment may be prepared through electrospinning technology.

In one embodiment of the present application, the thickness of the nanofiber structure may be 50 μm to 1000 μm.

In one embodiment of the present application, the radius of the nanofiber may be 250 nm to 750 nm.

In one embodiment of the present application, the volume fraction of the first space with respect to the nanofiber structure may be 90% or less. Specifically, the volume fraction of the first space for the nanofiber structure is 90% or less, 80% or less, 5% to 90%, 5% to 80%, 5% to 70%, 5% to It may be 10%, 30% to 90%, 30% to 80%, or 30% to 70%.

In one embodiment of the present application, when the volume ratio of the first space with respect to the nanofiber structure is 10% or less, the nanofiber structure may reflect or scatter sunlight and transmit mid-infrared rays. Specifically, when lowering the volume ratio of the nanofibers in the nanofiber structure, or thinning the thickness of the nanofiber structure, or both, the nanofiber structure is the transmission type temperature response and color radiation of FIG. It can be implemented as a cooling device. 1) In the case where there is no black body under the nanofiber structure, 1-1) when the external temperature is high, the nanofiber structure can reflect or scatter sunlight and transmit mid-infrared rays to absorb and The human body can cause mid-infrared radiation to blackbody. As a result, radiative cooling of the human body can be realized by transferring heat to space through the blackbody radiation of the human body. 1-2) When the external temperature is low, the thermal pigment of the nanofiber structure may partially absorb sunlight, and the nanofiber structure may transmit mid-infrared rays. At this time, since the energy of the partially absorbed sunlight is significantly larger than that of the black body radiation energy of the human body, the temperature of the nanofiber structure may rise, so that the human body can be kept warm through heat conduction. 2) In the case where a black body exists under the nanofiber structure, 2-1) when the external temperature is high, the nanofiber structure can reflect or scatter sunlight and transmit mid-infrared light to the lower black body It can absorb mid-infrared radiation from the black body and cause the black body to radiate it. Accordingly, the black body can be cooled through black body radiation, and the body can be cooled through heat conduction with the body. 2-2) When the external temperature is low, the thermal pigment of the nanofiber structure may partially absorb sunlight, and the nanofiber structure may transmit mid-infrared rays. At this time, since the energy of the partially absorbed sunlight is significantly larger than the black body radiation energy of the black body, the temperature of the nanofiber structure may rise, so that the human body can be kept warm through heat conduction.

In one embodiment of the present application, when the volume ratio of the first space with respect to the nanofiber structure is 30% to 90%, the nanofiber structure reflects or scatters sunlight, and blackbody radiation of mid-infrared rays can Specifically, in the case of increasing the volume ratio of the nanofibers in the nanofiber structure, or thickening the thickness of the nanofiber structure, or both, the nanofiber structure is the absorption / radiation type temperature response and color of FIG. It can be implemented as a type radiative cooling device. 3) In the case where there is no blackbody under the nanofiber structure, 3-1) when the external temperature is high, the nanofiber structure can reflect or scatter sunlight and absorb mid-infrared rays and radiate the blackbody have. Thereby, radiative cooling of the nanofiber structure is realized by transferring heat to space through the blackbody radiation of the nanofiber structure, and thus the temperature of the nanofiber structure can be lowered, and the human body is cooled through heat conduction with the human body. can 3-2) When the external temperature is low, the thermal pigment of the nanofiber structure may partially absorb sunlight, and the nanofiber structure may absorb mid-infrared rays and blackbody radiation. At this time, since the energy of the partially absorbed sunlight is significantly greater than the black body radiation energy of the nanofiber structure, the temperature of the nanofiber structure may rise, so that the human body can be kept warm through heat conduction.

In one embodiment of the present application, the nanofiber is polydimethylsiloxane (PDMS), polyimide (PI), poly methyl methacrylate (PMMA), polyacrylonitrile (PAN) ), polyester, nylon, polyethylene (PE), poly(vinylidene fluoride-co-hexafluoropropylene) (Poly(vinylidene fluoride-co-hexafluoropropylene); PVdF-HFP) may include. Specifically, the nanofiber may have high mechanical strength and relatively low transmittance in the mid-infrared wavelength. That is, the nanofiber may have a low mid-infrared transmittance compared to the nanofiber structure having a volume ratio of 10% or less.

Referring to FIGS. 2A to 2C , mid-infrared transmittance can be confirmed through refractive index spectra of three types of polymers: polydimethylsiloxane (PDMS), polyimide (PI), and polymethyl methacrylate (PMMA). It can be confirmed that the imaginary part of the refractive index of all three polymers is large in the mid-infrared rays, and through this, it can be confirmed that they have high mid-infrared absorption (low transmittance). However, the nanofiber structure can achieve high transmittance for mid-infrared rays by including a second space (air, etc.) other than the first space containing the nanofibers. Specifically, the high transmittance can be achieved when the volume ratio of the nanofiber to the nanofiber structure is 10% or less. In particular, when the nanofiber structure is a loosely entangled fabric structure, the volume ratio of the second space to the total volume of the nanofiber structure is large, so that the mid-infrared transmittance can be increased when compared to a simple thin film of the same thickness.

Referring to FIGS. 3A to 3C , the mid-infrared transmittance according to the thickness of the nanofiber structure (fabric type) and the volume fraction of the first space (nanofiber) for the nanofiber structure can be confirmed (bright color) the higher the transmittance). Specifically, in a fabric-type nanostructure using three types of polymers: polydimethylsiloxane (PDMS), polyimide (PI) and polymethyl methacrylate (PMMA), a) the volume ratio of the first space (nanofiber) is In the case of 10% or less, it can be seen that a high transmittance of 50% or more appears in most fabric thicknesses. In addition, considering that the lower limit of the thickness of a typical fabric is about 200 μm, it can be confirmed that a very high mid-infrared transmittance appears when the volume ratio is about 10% or less at the thickness. The above high transmittance is satisfied even if there is only about 2.6 times the diameter in all directions around the nanofiber, so if the diameter of the nanofiber is reduced through electrospinning, sufficient possibility to be used as a radiation cooling material can be secured. means On the other hand, b) when the volume ratio of the first space (nanofibers) is 30% to 90%, it can be confirmed that the low transmittance of 30% or less of transmittance is shown in most fabric thicknesses of 200 μm or more in the thickness of the nanofiber structure. .

Referring to FIGS. 4 and 5 , the reflectance of sunlight can be confirmed through the scattering efficiency spectrum of the nanofiber. Specifically, when the radius of the nanofiber is about 5 nm to 1 μm, the scattering efficiency is high for the wavelength of the solar region and the scattering efficiency is low for the mid-infrared rays. In particular, when the radius of the nanofiber is about 250 nm to 750 nm, the highest point of the scattering efficiency spectrum may enter a wavelength of about 400 nm to 1 μm. Since solar radiation is strongest in the wavelength band of 400 nm to 1 μm, it can be confirmed that the nanofiber having the above radius is very effective in scattering sunlight.

In one embodiment of the present application, the temperature-sensitive and color-type radiation cooling device of the present application may further include a blackbody radiator. Specifically, the temperature sensitive and chromatic radiative cooling device of the present disclosure may be used without a blackbody radiator or may further include a blackbody radiator. When the blackbody radiator is not included, the temperature-sensitive and color-type radiation cooling device having a volume ratio of 10% or less of the nanofiber can be used as a smart cloth, and in this case, the human body can act as a mid-infrared absorber and emitter. In addition, in the case of not including the blackbody radiator, the temperature-sensitive and color-type radiation cooling device having a volume ratio of 30% to 90% of the nanofiber itself can act as a mid-infrared absorber and emitter, so that the smart It can be used as a fabric. In addition, since the temperature-sensitive and color-type radiation cooling device can express color by itself, when used as a smart cloth, it has high utility in terms of design. In addition, when the blackbody radiator is included, the temperature-sensitive and color-type radiation cooling device can be utilized as a radiation cooling material where a flexible material is required. Specifically, the temperature-sensitive and color-type radiant cooling device is used in water tanks, buildings, automobiles, solar panels, windows, etc. that require flexible materials to express colors along with radiative cooling performance.

In one embodiment of the present application, the nanofiber may change color depending on the external temperature. Specifically, the nanofiber may include a thermal pigment, and in this case, the thermal pigment may include a leuco dye. The thermal pigment can reversibly switch between color expression and transparent state depending on the external temperature, and the color expression can be controlled by repeating generation and decomposition of the polymer complex of the thermal pigment according to the external temperature. In addition, the temperature-sensitive and color-type radiation cooling device according to the present application can be implemented with temperature-sensitive smart driving by using a temperature-sensitive pigment that shows color at low temperatures and is transparent at high temperatures. Specifically, when the thermal pigment absorbs a portion of visible light (sunlight) to express color (at low temperature), the temperature of the nanofiber increases to realize a thermal insulation function of the human body, and at high temperature, visible light (sunlight) Since the thermal pigment becomes transparent again due to reflection or scattering of the nanofibers to express white color, the nanofibers to which the thermal pigment is added may exhibit a radiative cooling function.

A second aspect of the present application provides a method for cooling or warming an object using the temperature-sensitive and color-type radiant cooling device according to the first aspect.

In the first aspect and the second aspect, content that may be common to each other may be applied even if the description thereof is omitted.

The foregoing description of the present application is for illustration, and those of ordinary skill in the art to which the present application pertains will understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present application. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and likewise components described as distributed may also be implemented in a combined form.

The scope of the present application is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present application.

Claims (15)

Nanofiber structure containing nanofibers with radiation cooling function and color expression function
A temperature-sensitive and color-type radiant cooling device comprising a.
The method of claim 1,
The nanofiber structure may include: a first space including the nanofiber; and
and a second space other than the first space.
The method of claim 1,
Wherein the nanofiber comprises a thermosensitive pigment, a temperature-sensitive and color-type radiation cooling device.
The method of claim 1,
The nanofiber structure has a thickness of 50 μm to 1000 μm, a temperature-sensitive and color-type radiation cooling device.
The method of claim 1,
The nanofiber has a radius of 250 nm to 750 nm, a temperature-sensitive and color-type radiation cooling device.
3. The method of claim 2,
wherein the volume fraction of the first space for the nanofiber structure is less than or equal to 90%.
7. The method of claim 6,
When the volume ratio of the first space with respect to the nanofiber structure is 10% or less, the nanofiber structure reflects or scatters sunlight and transmits mid-infrared rays, a temperature-sensitive and color-type radiation cooling device.
7. The method of claim 6,
When the volume ratio of the first space with respect to the nanofiber structure is 30% to 90%, the nanofiber structure reflects or scatters sunlight, and black body radiation of mid-infrared radiation, temperature-sensitive and color-type radiation cooling device.
The method of claim 1,
The nanofiber structure is a fabric-type or tangled network type, temperature-sensitive and color-type radiation cooling device.
3. The method of claim 2,
wherein the second space comprises air or vacuum.
The method of claim 1,
The nanofiber is polydimethylsiloxane (PDMS), polyimide (PI), poly methyl methacrylate (PMMA), polyacrylonitrile (PAN), polyester, nylon, polyethylene Temperature-sensitive and Color radiant cooling device.
4. The method of claim 3,
wherein the thermal pigment comprises a leuco dye.
The method of claim 1,
A temperature-sensitive and color-type radiation cooling device further comprising a black body radiator under the nanofiber structure.
The method of claim 1,
The nanofiber will change color depending on the external temperature, temperature-sensitive and color-type radiation cooling device.
A method of cooling or warming an object using the temperature-sensitive and color-type radiant cooling device according to claim 1 .

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