Radiation refrigeration coating and preparation method thereof

Abstract

The invention discloses a radiation refrigeration coating and a preparation method thereof, and relates to the technical field of radiation refrigeration paints.The preparation method comprises the steps that firstly, a nanometer high-thermal-conductivity inorganic material solution is evenly dispersed in an organic solvent, and inorganic dispersion liquid is obtained; and adding a biopolymer material into the inorganic dispersion liquid, and uniformly mixing to obtain the radiation refrigeration coating. The method is simple in preparation process and low in raw material price, the coating surface of the prepared radiation refrigeration coating shows high thermal emissivity larger than or equal to 0.95 and high thermal conductivity in long-wave infrared radiation, and the radiation refrigeration coating can be applied to any base material of the outer surfaces of buildings, traffic, computers, electric power, umbrellas, hats, fabrics, tents, vehicle hoods or curtains.

Description

Technical Field

[0001] The invention relates to the technical field of radiation cooling coatings, in particular to a radiation cooling coating and a preparation method thereof. Background Art

[0002] The energy consumption and heat management problems caused by the increasingly prominent global climate change problem are becoming increasingly severe. Problems such as heat dissipation of electronic components, cooling of residential buildings, and management of industrial waste heat are all thorny problems that need to be solved in the new era. Therefore, it is imperative to develop new cooling technologies to replace traditional fan heat dissipation and air conditioning refrigeration. Among them, radiation cooling technology can transmit the heat on the surface of the building through the atmospheric window at a wavelength of 8 to 13 μm without the need for electrical energy input, and emit it into outer space in the form of long-wave infrared thermal radiation, thereby achieving the effect of cooling. Therefore, it is required that the radiation cooling coating has a high emissivity in the infrared atmospheric window area (wavelength 8 to 13 μm), which puts higher requirements on the preparation of materials. At present, most of the radiation cooling materials are devoted to photonic crystals, multi-layer film assembly, silver-based metamaterial films, etc., which often require higher equipment requirements and production costs, and the production process is complicated, and cannot be directly used for coating on the surface of the building; and most of them are organic coatings, which have poor durability in the building environment, which undoubtedly further increases the cost. In addition, there are also a variety of radiation cooling and heat dissipation coatings, but none of them can achieve a balanced state in terms of cooling effect, production difficulty, and use cost. Summary of the invention

[0003] In order to solve the problems of the prior art, the purpose of the present invention is to overcome the shortcomings of the existing technology and provide a radiant cooling coating and a preparation method thereof. By combining nano high thermal conductivity inorganic materials and biopolymer materials, the problem of poor cooling performance of the coating is effectively solved.

[0004] One of the purposes of the present invention is to provide a method for preparing a radiant cooling coating, and the technical scheme is as follows:

[0005] A method for preparing a radiant cooling coating comprises the following steps:

[0006] S1. Preparing an inorganic dispersion: uniformly dispersing a nanometer high thermal conductivity inorganic material solution in an organic solvent to obtain the inorganic dispersion;

[0007] S2. Preparing a radiation cooling coating: adding a biopolymer material to the inorganic dispersion and mixing them evenly to obtain the radiation cooling coating.

[0008] Preferably, the nano high thermal conductive material is at least one of aluminum oxide, magnesium oxide, copper oxide, manganese oxide and zinc oxide with a particle size of 20 to 50 nm.

[0009] Preferably, the mass proportion of the nano high thermal conductive material in the inorganic dispersion is 5-10wt%.

[0010] Preferably, the biopolymer material is cellulose or a cellulose derivative.

[0011] More preferably, the cellulose is at least one of cellulose acetate, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, cyanoethyl cellulose and hydroxypropyl cellulose.

[0012] Preferably, the biopolymer material accounts for 15-20 wt % of the inorganic dispersion.

[0013] The second object of the present invention is to provide a radiant cooling coating prepared by the above-mentioned preparation method of the radiant cooling coating, and the technical scheme is as follows:

[0014] A radiation cooling coating comprises an organic solvent, a nanometer high thermal conductivity material and a biopolymer material.

[0015] Preferably, the nano high thermal conductive material is at least one of aluminum oxide, magnesium oxide, copper oxide, manganese oxide and zinc oxide with a particle size of 20 to 50 nm.

[0016] Preferably, the biopolymer material is cellulose or a cellulose derivative.

[0017] The third object of the present invention is to provide an application of the above-mentioned radiation cooling coating, and the technical solution is as follows:

[0018] An application of a radiation cooling coating is to coat the radiation cooling material on a fabric or a metal substrate, the coating method is one of spraying, brushing or dipping, and the coating thickness is 0.1 to 0.5 mm.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a method for preparing a radiant cooling coating. The prepared coating comprises a mixture of an inorganic material and a biopolymer material, thereby achieving an excellent heat dissipation and cooling effect. The radiant cooling coating is obtained by coating on a substrate, and has excellent cooling performance and a high thermal emissivity. The preparation method is simple and easy, has high efficiency, and various technical parameters are easy to control. It is low-cost, highly efficient and economical, and has broad application prospects.

[0021] The radiant cooling coating prepared by the present invention has a simple preparation process and low raw material price, and the coating surface exhibits a high thermal emissivity of ≧0.95 and high thermal conductivity in long-wave infrared radiation, and can be applied on any substrate of the outer surface of buildings, transportation, computers, electricity, umbrellas, hats, fabrics, tents, awnings or curtains. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a test spectrum of the emissivity test of Example 1 of the present invention;

[0023] Figure 2 This is a schematic diagram of an experiment for testing the actual cooling effect of the present invention;

[0024] Figure 3 This is a curve diagram of the temperature change of the three samples over time when sample A, a blank sample and an empty sample are at 4.8W in the actual cooling effect test of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] An embodiment of a method for preparing a radiant cooling coating is described below, specifically:

[0027] Example 1

[0028] S1. Prepare an inorganic dispersion: Disperse 30 nm aluminum oxide in a mixed solution of 20 ml acetone and 20 ml anhydrous ethanol to obtain an inorganic dispersion, wherein the mass ratio of aluminum oxide is 5 wt %;

[0029] S2. Preparation of biopolymer-inorganic composite coating: 6.5 g of cellulose acetate (CA) was added into an inorganic dispersion to dissolve, wherein the mass ratio of CA to the inorganic dispersion was 15 wt %, so that it was completely dissolved, and the biopolymer material and the inorganic material were evenly mixed. The prepared composite coating was marked as: Al2O3 / CA composite coating.

[0030] Example 2

[0031] The steps are basically the same as those in Example 1, except that:

[0032] In step S2, 6.5 g of CA is replaced by 6.5 g of hydroxyethyl cellulose (HEC), and the prepared composite coating is marked as: Al2O3 / HEC composite coating.

[0033] Example 3

[0034] The steps are basically the same as those in Example 2, except that:

[0035] In step S1, 30 nm of aluminum oxide is replaced by 30 nm of magnesium oxide, and the mass ratio of magnesium oxide in the inorganic dispersion is 5 wt %. The prepared composite coating is marked as MgO / HEC composite coating.

[0036] Example 4

[0037] The steps are basically the same as those in Example 3, except that:

[0038] In step S2, 6.5 g of HEC was replaced by 6.5 g of hydroxypropyl methylcellulose (HPMC), and the prepared composite coating was marked as: MgO / HPMC composite coating.

[0039] Example 5

[0040] The steps are basically the same as those in Example 1, except that:

[0041] In step S2, 6.5 g of HEC is replaced with 6.5 g of hydroxypropyl methylcellulose (HPMC), and the mass ratio of HPMC to the inorganic dispersion is 20 wt %. The prepared composite coating is marked as MgO / HPMC composite coating.

[0042] It should be noted that in the above five embodiments, a mixed solution of acetone and anhydrous ethanol is selected as the organic solution, and methanol, ethanol, isopropanol, n-butanol, etc. can also be selected.

[0043] In the preparation process of the above five embodiments, the method for mixing or dispersing the solution can be a method of stirring the mixture with a stirrer, a method of ultrasonic dispersion, or a method of shaking.

[0044] In the above five embodiments, in addition to the above-mentioned two high thermal conductivity inorganic materials of aluminum oxide and magnesium oxide, other high thermal conductivity inorganic materials can also be selected, such as copper oxide, manganese oxide, zinc oxide, etc. The particle size of these high thermal conductivity inorganic materials is preferably in the range of 20 to 50 nm, and the mass proportion of the high thermal conductivity inorganic material in the configured inorganic dispersion is preferably controlled at 5 to 10 wt%.

[0045] In the above five embodiments, in addition to the above-mentioned biopolymer materials such as CA, HEC, and HPMC, other biopolymer materials may also be selected, such as: methyl cellulose, carboxymethyl cellulose, ethyl cellulose, cyanoethyl cellulose, hydroxypropyl cellulose, etc., and derivatives of these celluloses may also be selected; preferably, the viscosity of these celluloses or cellulose derivatives ranges from 100 to 800 mPa·s.

[0046] In the above five embodiments, the prepared composite coating needs to be left to stand or be vacuumed to remove bubbles therein after preparation.

[0047] In order to test the performance of the composite coating samples of the above five embodiments, different composite coating samples were coated on an aluminum plate substrate and dried to obtain radiant cooling coatings corresponding to the five embodiments, namely samples A, B, C, D and E.

[0048] The emissivity of five radiative cooling coatings was tested. The test spectra corresponding to Example 1 are shown in FIG. Figure 1 As shown, the high thermal emissivity of the corresponding five radiation cooling coating samples in the infrared atmospheric window region (wavelength 8-13 μm) are listed in Table 1, and all five samples have a high thermal emissivity of more than 0.9.

[0049] The actual cooling effect of five radiative cooling coatings was tested, and a blank sample (substrate without coating) and an unadded sample (air) were added for comparative testing. The test process is as follows: Figure 2 As shown, an electric heating sheet is placed under each substrate. The dimensions of the five substrates are 10×10×0.1 cm, and the thickness of the composite coating is 300 μm. When the power of the electric heating sheet is set to 4.8 W or 10 W at an ambient temperature of 25°C, the cooling amplitude of the five radiation cooling coatings is higher than that of the blank control sample. Figure 3 The temperature of sample A, blank sample and empty sample changes with time when the temperature is 4.8W. 基体-i =T 基体-i -T 基体-0 , where T represents the temperature of the sample after stabilization, the subscript substrate-0 corresponds to the blank control sample, and substrate-i corresponds to one of the five radiation cooling coating samples. The corresponding data are listed in Table 1. It can be seen that the five radiation cooling coatings can effectively reduce the substrate surface temperature.

[0050] The composite coatings prepared in the five embodiments were coated on computer heat sinks respectively, and an uncoated computer heat sink was used as a comparison test. At 19.8W, the temperature difference ΔT of the computer heat sinks of different samples was 散热片-i =T 散热片-i -T 散热片-0, T represents the temperature of different heat sinks, the subscript heat sink-0 represents an uncoated computer heat sink, and heat sink-i represents a computer heat sink coated with the composite coatings of the five embodiments. The results are listed in Table 1. The computer heat sink coated with the composite coating has better heat dissipation performance.

[0051] The composite coatings prepared in the five embodiments were tested for thermal conductivity after drying. The results are listed in Table 1. The thermal conductivities were all above 2w / m / k.

[0052] Table 1 Partial performance test data of five examples

[0053]

[0054] Heat dissipation effect test: The composite coating of Example 1 was applied to several positions of the integrated lamp, and compared with the uncoated lamp, the temperature was measured when the lamp was lit at different times, and a comparative temperature test was performed. As shown in Table 2, it can be seen that the temperature of the shell coated with the composite coating is lower than that of the uncoated shell, and the heating rate of the coated shell is slower.

[0055] Table 2 Partial performance test data of five examples

[0056]

[0057] The composite coating prepared above can be coated on a substrate such as a fabric or metal, and the coating method can be spraying, brushing or dipping, etc. The coating thickness is preferably controlled at 0.1 to 0.5 mm, which can increase the thermal conductivity and cooling performance of the substrate.

[0058] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is limited by the attached embodiments and their equivalents.

Claims

1. A method for preparing a radiant cooling coating, characterized in that: The following steps are involved: S1. Preparing an inorganic dispersion: uniformly dispersing a nanometer high thermal conductivity inorganic material solution in an organic solvent to obtain the inorganic dispersion; S2. Preparing a radiation cooling coating: adding a biopolymer material to the inorganic dispersion and mixing them evenly to obtain the radiation cooling coating.

2. The method for preparing the radiation cooling coating according to claim 1, characterized in that: The nanometer high thermal conductive material is at least one of aluminum oxide, magnesium oxide, copper oxide, manganese oxide and zinc oxide with a particle size of 20 to 50 nm.

3. The method for preparing the radiation cooling coating according to claim 1, characterized in that: The mass percentage of the nano high thermal conductive material in the inorganic dispersion is 5-10wt%.

4. The method for preparing the radiation cooling coating according to claim 1, characterized in that: The biopolymer material is cellulose or a cellulose derivative.

5. The method for preparing the radiation cooling coating according to claim 4, characterized in that: The cellulose is at least one of cellulose acetate, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, cyanoethyl cellulose and hydroxypropyl cellulose.

6. The method for preparing the radiation cooling coating according to claim 1, characterized in that: The biopolymer material accounts for 15-20 wt % of the inorganic dispersion.

7. A radiation cooling coating, characterized in that: The radiant cooling coating is prepared by the preparation method of the radiant cooling coating according to any one of claims 1 to 6, wherein the radiant cooling coating comprises an organic solvent, a nano high thermal conductive material and a biopolymer material.

8. The radiation cooling coating according to claim 7, characterized in that: The nanometer high thermal conductive material is at least one of aluminum oxide, magnesium oxide, copper oxide, manganese oxide and zinc oxide with a particle size of 20 to 50 nm.

9. The radiation cooling coating according to claim 7, characterized in that: The biopolymer material is cellulose or a cellulose derivative.

10. An application of a radiation cooling coating, characterized in that: The radiation cooling coating according to any one of claims 7 to 8 is coated on a fabric or a metal substrate, the coating method is one of spraying, brushing or dipping, and the coating thickness is 0.1 to 0.5 mm.

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