Roof component based on evaporation and radiation synergistic cooling and preparation and construction thereof

Abstract

The invention discloses a roof component based on evaporation and radiation collaborative cooling and preparation and construction thereof. The roof component breaks through the limitation of a single cooling mode through a multi-layer structure coupling evaporative cooling and radiation cooling technology. The reflective film specifically comprises a base layer, an evaporation radiation synergistic cooling material layer and a reflective protection layer. The synergistic material layer is formed by modifying polyacrylamide hydrogel through lithium bromide moisture absorption salt, titanium dioxide nanoparticles are embedded to improve the short-wave reflectivity and long-wave emissivity, and the synergistic material layer has the functions of radiation cooling and moisture absorption evaporation; the reflective protective layer is made of polyvinylidene fluoride-hexafluoropropylene copolymer, so that radiation cooling power is supplemented and pollution is prevented on the premise of moisture permeability; the heat entering a room is reduced by combining an evaporation radiation synergistic cooling material and a reflection protection material; by means of the roof component based on evaporation and radiation collaborative cooling, the limitation of cooling power can be broken through, the cooling effect is enhanced, and the purpose of building energy saving is achieved.

Description

Technical Field

[0001] The present invention relates to the field of cooling of building envelope structures, and in particular to a roof component based on evaporative radiation coordinated cooling and the preparation and construction thereof. Background Art

[0002] In the context of global warming, building roof cooling load accounts for 40%-60% of the total building energy consumption (determined by ASHRAE standards).

[0003] The high energy consumption and exacerbated heat island effect of traditional air conditioning systems have necessitated the development of passive cooling technologies. Among these passive cooling technologies, radiative cooling and evaporative cooling have attracted considerable attention due to their lack of energy input.

[0004] Radiative cooling relies on a transparent window in the atmosphere (8-13 μm) to radiate heat into outer space, but its efficiency is easily affected by cloud cover; evaporative cooling uses water evaporation to absorb heat and cool down, but at night the liquefaction and release of heat from water will cause the temperature to rise.

[0005] In existing technologies, the single application of radiation or evaporative cooling has significant limitations: the efficiency of radiation cooling drops sharply on cloudy days, while evaporative cooling requires a continuous water supply and faces thermal fluctuations between day and night.

[0006] Research shows that combining the two to form a synergistic cooling mechanism can break through their respective bottlenecks: daytime evaporative cooling compensates for weather fluctuations in radiation efficiency, while nighttime radiative cooling offsets liquefaction heat release, while reducing dependence on stable water sources.

[0007] However, current research lacks a systematic solution for the coupling structure, energy efficiency synergy mechanism and environmental adaptability of the two. There is an urgent need to design an efficient and integrated passive collaborative cooling component to match complex climatic conditions and improve the overall cooling stability. Summary of the Invention

[0008] The present invention aims to overcome the shortcomings and deficiencies of the prior art by providing a roof structure based on evaporative and radiative synergistic cooling, as well as its preparation and construction. This invention overcomes the limitations of existing technologies that rely solely on cooling power and mitigates the degradation of cooling performance caused by the coupling and mutual influence of the two. The present invention combines evaporative and radiative synergistic cooling with reflective protection, significantly reducing heat entering the room.

[0009] The present invention is achieved through the following technical solutions:

[0010] A roof component based on evaporative radiation synergistic cooling, comprising a reflective protective layer 1, an evaporative radiation synergistic cooling material layer 2 and a base layer 3;

[0011] The reflective protection layer 1, the evaporative radiation cooperative cooling material layer 2 and the base layer 3 are stacked in sequence from top to bottom.

[0012] The evaporative radiation collaborative cooling material layer 2 comprises the following components:

[0013] Polyacrylamide hydrogel matrix;

[0014] Lithium bromide hygroscopic salt loaded by impregnation method, the hygroscopic salt accounts for 15%-45% of the hydrogel, preferably 35%;

[0015] The uniformly dispersed titanium dioxide nanoparticles have a particle size of 20-100 nm and account for 5%-15% of the hydrogel by mass.

[0016] The reflection protection layer 1 is made of polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, with a thickness of 0.5-2 mm and a water vapor permeability of ≥300 g / m 2 24h, shortwave reflectivity>0.88.

[0017] The base layer 3 is a waterproof facing brick or metal plate with a thickness of 5-15 mm.

[0018] The preparation of the polyacrylamide hydrogel matrix comprises the following steps:

[0019] S1, preparing a prepolymer solution by mixing 2.00-4.00 mol / L acrylamide monomer, 0.001-0.004 mol / L cross-linking agent N,N'-methylenebisacrylamide BIS, and 0.0024-0.0048 mol / L initiator potassium persulfate KPS;

[0020] S2, the prepolymer solution was deoxygenated and polymerized under argon atmosphere for 60–90 min to form a PAAm gel;

[0021] S3, the PAAm gel is freeze-dried and then immersed in a lithium bromide solution, wherein the concentration of the salt solution is 15%-45% wt% lithium bromide solution, and the immersion time is ≥48 hours.

[0022] The evaporative radiation cooperative cooling material layer 2 has a short-wave reflectivity greater than 0.85, with a wavelength range of 0.3-2.5 μm, and a long-wave emissivity greater than 0.95, with a wavelength range of 2.5-25 μm.

[0023] The porosity of the reflection protection layer 1 is 15%-30%, and the pore size is 1-5 μm.

[0024] The interface bonding strength between the base layer 3 and the evaporative radiation collaborative cooling material layer 2 is ≥1.5MPa;

[0025] The impregnation pressure of the lithium bromide solution is 0.1-0.3 MPa.

[0026] The construction method of the roof component of the present invention includes the following steps: sequentially compounding a base layer 3, an evaporative radiation collaborative cooling material layer 2, and a reflective protective layer 1 into a prefabricated board; coating an epoxy resin interface agent on the surface of a roof 4, and attaching the prefabricated board to the roof; and hot-melt sealing the joints between the prefabricated boards with a PVDF-HFP film.

[0027] Compared with the prior art, the present invention has the following advantages and effects:

[0028] The present invention is a roof component based on evaporative radiation synergistic cooling. An evaporative radiation synergistic cooling material layer is adhered to a roof facing brick layer. The facing bricks serve as the base layer of the entire structure, and the top layer is a reflective protective layer with microscopic holes.

[0029] The evaporative radiation collaborative cooling material layer of the present invention is prepared to have both evaporative cooling and radiative cooling capabilities. The reflective protective layer can not only supplement a portion of the radiative cooling power, but also effectively allow moisture to be fully exchanged between the evaporative radiation collaborative cooling material layer and the atmosphere.

[0030] The evaporative radiation synergistic cooling material of the present invention is combined with the reflective protective material to reduce the heat entering the room.

[0031] By using the roof component based on evaporation-radiation coordinated cooling of the present invention, the limitation of cooling power can be broken through, the cooling effect can be enhanced, and the purpose of building energy saving can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic cross-section of a roof component based on evaporative radiation synergistic cooling according to the present invention;

[0033] Figure 2 It is a schematic diagram of the roof component and roof construction of the present invention. DETAILED DESCRIPTION

[0034] The present invention is described in further detail below with reference to specific embodiments.

[0035] like Figure 1 As shown, the present invention discloses a roof component based on evaporative radiation synergistic cooling, comprising a reflective protective layer 1, an evaporative radiation synergistic cooling material layer 2 and a base layer 3 (facing brick);

[0036] The reflective protection layer 1, the evaporative radiation cooperative cooling material layer 2 and the base layer 3 are stacked in sequence from top to bottom.

[0037] The evaporative radiation collaborative cooling material layer 2 comprises the following components:

[0038] Polyacrylamide hydrogel matrix;

[0039] Lithium bromide hygroscopic salt loaded by impregnation method, the hygroscopic salt accounts for 15%-35% of the hydrogel;

[0040] The uniformly dispersed titanium dioxide nanoparticles have a particle size of 20-100 nm and account for 5%-15% of the hydrogel by mass.

[0041] The reflection protection layer 1 is made of polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP, with a thickness of 0.5-2 mm and a water vapor permeability of ≥300 g / m 2 24h, shortwave reflectivity>0.88.

[0042] The base layer 3 is a waterproof facing brick or metal plate with a thickness of 5-15 mm.

[0043] The preparation of the polyacrylamide hydrogel matrix comprises the following steps:

[0044] S1, preparing a prepolymer solution by mixing 2.00-4.00 mol / L acrylamide monomer, 0.001-0.004 mol / L cross-linking agent N,N'-methylenebisacrylamide BIS, and 0.0024-0.0048 mol / L initiator potassium persulfate KPS;

[0045] S2, the prepolymer solution was deoxygenated and polymerized under argon atmosphere for 60–90 min to form a PAAm gel;

[0046] S3, the PAAm gel is freeze-dried and then immersed in a lithium bromide solution, wherein the concentration of the salt solution is 15%-45% wt% lithium bromide solution, and the immersion time is ≥48 hours.

[0047] The short-wave reflectivity of the evaporative radiation cooperative cooling material layer 2 is greater than 0.85, with a wavelength range of 0.3-2.5 μm, and the long-wave emissivity is greater than 0.95, with a wavelength range of 8-13 μm.

[0048] The porosity of the reflection protection layer 1 is 15%-30%, and the pore size is 1-5 μm.

[0049] The interface bonding strength between the base layer 3 and the evaporative radiation collaborative cooling material layer 2 is ≥1.5MPa;

[0050] The impregnation pressure of the lithium bromide solution is 0.1-0.3 MPa.

[0051] like Figure 2 As shown, the construction method of the roof component of the present invention includes the following steps: the base layer 3, the evaporative radiation collaborative cooling material layer 2 and the reflective protective layer 1 are sequentially compounded into a prefabricated board; the epoxy resin interface agent is applied to the surface of the roof 4, and the prefabricated board is attached to the roof; the joints between the prefabricated boards are sealed with a PVDF-HFP film by hot-melt sealing.

[0052] Since the base layer 3, the evaporative radiation cooperative cooling material layer 2 and the reflective protective layer 1 themselves have a certain viscosity, they can be compounded into a prefabricated board solely by their own viscosity.

[0053] The roofing element of the present invention provides the synergistic cooling element with performance tailored to the specific characteristics of the roof, enabling adaptation to various roof types while also ensuring the strength of the synergistic cooling element itself. Furthermore, this element technology concept can be used as a cooling method for elements other than the roof of a structure, such as the walls, doorposts, door headers, and doors of the exterior envelope.

[0054] The evaporative-radiative synergistic cooling material layer of the present invention, when applied to a roof surface, is reusable, exhibits stable radiative cooling performance, and exhibits self-replenishing evaporative performance, meaning it maintains long-term performance. This allows for extended use of the cooling component without requiring refills or frequent replacement, contributing to economic efficiency.

[0055] The present invention combines evaporative cooling with radiant cooling. This component can cool building roofs after placement without requiring manual replacement or additional energy. The use of a base layer ensures the component's performance matches the roof's characteristics, while also supporting the structure and preventing moisture penetration and corrosion. Another advantage is that, compared to single cooling methods, the component's multi-layered structure rationally couples radiant and evaporative cooling.

[0056] The evaporative radiation synergistic cooling material layer 2 of the present invention is the main functional layer, and the reflective protective layer 1 is the supplementary cooling and protective layer. The three layers are combined to form an evaporative radiation synergistic cooling roof component.

[0057] To achieve evaporative cooling within the evaporative-radiative synergistic cooling material layer, a hydrogel with a certain evaporative cooling capacity was chosen as the base material. However, hydrogels lack the ability to absorb water, meaning they cannot be recycled. Therefore, a hygroscopic salt was added to the hydrogel to enhance the material's moisture absorption and release properties. Considering both hygroscopic capacity and economic efficiency, lithium bromide was chosen as the hygroscopic salt.

[0058] There are many types of hydrogels, and when using them on building roofs, it's crucial to consider whether the material will harm the building itself, so choosing a neutral hydrogel is crucial. The amount of hygroscopic salt added is also a factor in selecting the type of hydrogel to achieve a moisture absorption and release cycle across multiple climate zones. Taking all these factors into consideration, polyacrylamide hydrogel was chosen as the base material for the evaporative radiation synergistic cooling layer. This hydrogel is both neutral, non-toxic, and durable, and can also support varying concentrations of lithium bromide hygroscopic salt.

[0059] The hydrogel was prepared by thermally initiated polymerization. First, 2.00 mol / L monomer acrylamide (AM) and 0.001 mol / L chemical crosslinker N,N'-methylenebisacrylamide (BIS) were added to deionized, deoxygenated water and stirred uniformly. Argon was passed through the mixture for 15 minutes to remove oxygen from the mixture. Subsequently, 0.0024 mol / L initiator KPS was quickly added to the solution and stirred for 1 minute to form a uniform prepolymer solution. The prepolymer solution was ultrasonically treated for 5 minutes to remove bubbles; the prepolymer solution was then injected into a glass mold via a syringe, and the mold was placed in a 60°C forced air oven for 1 hour to obtain the PAAm gel.

[0060] There are two ways to add hygroscopic salt to the hydrogel. One is to add a certain concentration of salt solution to the prepolymer solution before polymerization. The other is to soak the freeze-dried hydrogel in the salt solution after polymerization (i.e., adding salt by immersion).

[0061] To be used on roofs in multiple climate zones, the salt concentration added to the hydrogel should have a wide range of flexibility. The second of the two methods allows for the addition of more salt, so lithium bromide is added using the immersion method. Furthermore, freeze-drying the hydrogel rather than baking it preserves its structure, minimizing deformation during moisture absorption and desorption. The freeze-dried gel also provides greater strength and durability.

[0062] At the same time, in order to achieve a radiative cooling effect in the evaporative radiation collaborative cooling material layer, the short-wave reflectivity and long-wave emissivity of the above-mentioned salt water gel (hereinafter referred to as Li-PAAM) were measured. It was found that the emissivity of Li-PAAM itself in the mid-infrared band is greater than 0.95, and only its reflectivity in the solar shortwave band needs to be modulated.

[0063] To achieve radiative cooling, titanium dioxide nanoparticles were added to the hydrogel during preparation to enhance short-wave reflectivity. This resulted in a short-wave reflectivity greater than 0.85 and a long-wave emissivity greater than 0.99 for the evaporative radiation synergistic cooling material layer. Because titanium dioxide is relatively inexpensive compared to other nanoparticles, this approach effectively considered economic benefits.

[0064] Furthermore, the addition of nanoparticles is beneficial because their particle size is controllable and they don't undergo electrolysis in water, thus preventing damage to evaporation performance. The addition of nanoparticles and hygroscopic salts does not conflict with each other, ensuring that the evaporative and radiative cooling layers deliver simultaneous cooling.

[0065] The evaporative radiation synergistic cooling material layer of the present invention contains hygroscopic salts that enhance evaporative cooling and nanoparticles that enhance radiative cooling. The evaporative radiation synergistic cooling material layer contains nanoparticles of titanium dioxide, bromide ions, and lithium ions, and the three particles are evenly distributed inside the hydrogel.

[0066] As a supplementary cooling and protective layer, the passive protective layer 3 is placed on the outermost layer, in direct contact with the atmosphere. This layer acts as a protective layer, blocking contamination of the evaporative radiation synergistic cooling material layer while allowing water vapor to pass smoothly through the passive protective layer to maintain the evaporative performance of the evaporative radiation synergistic cooling material layer.

[0067] In addition, the use of a passive protective layer will also affect the radiation characteristics of the evaporative radiation collaborative cooling material layer. Therefore, this layer should supplement the affected part of the radiation cooling so that the collaborative cooling can function normally.

[0068] Poly(vinylidene fluoride-hexafluoropropylene) is selected as the passive protective layer, which not only meets the requirements of water vapor passage, but also effectively supplements radiation cooling, so that the overall component can effectively achieve evaporation and radiation coordinated cooling, and ensure the stability and durability of the component.

[0069] As described above, the present invention can be implemented well.

[0070] The implementation methods of the present invention are not limited to the above-mentioned embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A roof component based on evaporative radiation synergistic cooling, characterized in that: It comprises a reflective protective layer (1), an evaporative radiation cooperative cooling material layer (2) and a base layer (3); The reflective protection layer (1), the evaporative radiation cooperative cooling material layer (2) and the base layer (3) are stacked in sequence from top to bottom.

2. The roof component based on evaporative radiation synergistic cooling according to claim 1, characterized in that: The evaporative radiation collaborative cooling material layer (2) comprises the following components: Polyacrylamide hydrogel matrix; Lithium bromide hygroscopic salt loaded by impregnation method, the hygroscopic salt accounts for 15%-45% of the hydrogel; The uniformly dispersed titanium dioxide nanoparticles have a particle size of 20-100 nm and account for 5%-15% of the hydrogel by mass.

3. The roof component based on evaporative radiation synergistic cooling according to claim 1, characterized in that: The reflection protection layer (1) is a polyvinylidene fluoride-hexafluoropropylene copolymer with a thickness of 0.5-2 mm and a water vapor permeability of ≥300 g / m 2 24h, shortwave reflectivity>0.

88.

4. The roof component based on evaporative radiation synergistic cooling according to claim 1, characterized in that: The base layer (3) is a waterproof facing brick or metal plate with a thickness of 5-15 mm.

5. The roof component based on evaporative radiation synergistic cooling according to claim 2, characterized in that: The preparation of the polyacrylamide hydrogel matrix comprises the following steps: S1, preparing a prepolymer solution by combining 2.00-4.00 mol / L acrylamide monomer, 0.001-0.004 mol / L crosslinker N,N'-methylenebisacrylamide (BIS), and 0.0024-0.0048 mol / L initiator potassium persulfate; S2, the prepolymer solution was deoxygenated and polymerized under argon atmosphere for 60–90 min to form a PAAm gel; S3, the PAAm gel is freeze-dried and then immersed in a lithium bromide solution, wherein the concentration of the salt solution is 15%-45% wt% lithium bromide solution, and the immersion time is ≥48 hours.

6. The roof component based on evaporative radiation synergistic cooling according to claim 1, characterized in that: The evaporative radiation cooperative cooling material layer (2) has a short-wave reflectivity greater than 0.85, a wavelength range of 0.3-2.5 μm, and a long-wave emissivity greater than 0.95, a wavelength range of 2.5-25 μm.

7. The roof structure based on evaporative radiation synergistic cooling according to claim 1, characterized in that: The porosity of the reflection protection layer (1) is 15%-30%, and the pore size is 1-5 μm.

8. The roof component based on evaporative radiation synergistic cooling according to claim 1, characterized in that: The interface bonding strength between the base layer (3) and the evaporative radiation collaborative cooling material layer (2) is ≥1.5 MPa.

9. The roof element according to claim 5, characterized in that In step S3, the immersion pressure of the lithium bromide solution is 0.1-0.3 MPa.

10. The construction method of the roof member according to any one of claims 1 to 9, characterized in that The method comprises the following steps: compounding a base layer (3), an evaporative radiation collaborative cooling material layer (2) and a reflective protective layer (1) in sequence into a prefabricated board; coating an epoxy resin interface agent on the surface of a roof (4) and attaching the prefabricated board to the roof; and hot-melt sealing the joints between the prefabricated boards with a PVDF-HFP film.

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