An all-season adaptive building thermal management system

Abstract

The application relates to a full-season adaptive building thermal management system, and relates to the technical field of building energy-saving thermal management, which comprises a temperature-sensitive hydrogel layer and a composite photothermal phase change material layer stacked from top to bottom; the temperature-sensitive hydrogel layer is a PNIPAM and PAM copolymer crosslinked network structure, and is internally doped with sodium chloride and calcium chloride; the low critical solution temperature LCST of the temperature-sensitive hydrogel layer is 32 DEG C, and the thickness is 0.5 cm; the composite photothermal phase change material layer is prepared by preparing a three-dimensional aerogel skeleton from cellulose nanofiber, carbon nanotube, graphene oxide and silane coupling agent, and vacuum impregnating octadecane to form the three-dimensional aerogel skeleton; the phase change temperature is 28 DEG C, and the thickness is 3 cm. The application adopts a double-layer composite structure of a temperature-sensitive hydrogel layer and a composite photothermal phase change material layer, relies on specific temperature-sensitive response temperatures and phase change temperatures of the two layers of materials, perfectly adapts to building thermal management requirements in summer and winter, and solves the problem of indoor supercooling and sharp increase of heating energy consumption caused by continuous heat dissipation of single radiation refrigeration materials in winter.

Description

Technical Field

[0001] This invention relates to the field of building energy-saving thermal management technology, and in particular to an all-season adaptive building thermal management system. Background Technology

[0002] Building cooling and heating energy consumption accounts for more than one-third of the total building energy consumption. The roof receives much higher solar radiation than the exterior walls, making it a core area for building heat loss. Existing single-evapor radiant cooling materials can only achieve cooling in summer, while continuous radiative heat loss in winter causes indoor overcooling, significantly increasing heating energy consumption. Traditional insulating bricks and aluminum foil reflective films lack temperature self-adaptation capabilities and cannot automatically adjust light transmission / reflection performance according to the season, resulting in short periods of constant temperature throughout the year and building energy savings of less than 45%. Currently, there is a lack of a dual-layer coupled adaptive building thermal management structure that can simultaneously achieve heat insulation and heat dissipation in summer and light transmission and heat storage in winter. Summary of the Invention

[0003] This invention proposes an all-season adaptive building thermal management system.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A seasonal adaptive building thermal management system comprises a thermosensitive hydrogel layer and a composite photothermal phase change material layer stacked from top to bottom. The thermosensitive hydrogel layer has a PNIPAM and PAM copolymer crosslinked network structure, internally doped with sodium chloride and calcium chloride. The thermosensitive hydrogel layer has a low critical solution temperature (LCST) of 32°C and a thickness of 0.5 cm. The composite photothermal phase change material layer is formed by vacuum impregnation of octadecane with a three-dimensional aerogel framework made of cellulose nanofibers, carbon nanotubes, graphene oxide, and silane coupling agent, with a phase change temperature of 28°C and a thickness of 3 cm.

[0005] A further preferred embodiment of the present invention is that the mass ratio of PNIPAM to PAM monomers is 4:1.

[0006] A further preferred embodiment of the present invention is that the temperature-sensitive hydrogel layer is soaked in a 10wt% sodium chloride solution to regulate LCST, and calcium chloride is uniformly dispersed inside the cross-linked network.

[0007] A further preferred embodiment of the present invention: the raw materials for preparing the composite photothermal phase change material layer include 1.55wt% cellulose nanofiber suspension, multi-walled carbon nanotubes, graphene oxide suspension, and APTES silane coupling agent. After acidification at pH=4 and vacuum freeze-drying to obtain an aerogel framework, it is impregnated with octadecane.

[0008] A further preferred embodiment of the present invention is that the liquid phase leakage rate of the composite photothermal phase change material layer is less than 1.5% after continuous heating at 90°C for 24 hours.

[0009] A further preferred embodiment of the present invention: the temperature-sensitive hydrogel layer has a solar radiation reflectance of 71% when the temperature is above 32℃, a solar radiation reflectance of 16% when the temperature is below 32℃, and an infrared emissivity of 0.8 across the entire temperature range; and a saturated water absorption rate of 6g / g at 20℃ and 80% relative humidity.

[0010] A further preferred embodiment of the present invention is that the temperature-sensitive hydrogel layer and the composite photothermal phase change material layer are directly bonded together and laid on the outer surface of the building roof enclosure structure.

[0011] The present invention has the following technical effects: 1. This invention adopts a double-layer composite structure of a temperature-sensitive hydrogel layer and a composite photothermal phase change material layer. Relying on the specific temperature-sensitive response temperature and phase change temperature of the two layers, it achieves bidirectional adaptive regulation of heat insulation and heat dissipation in summer and light transmission and heat storage in winter. It perfectly adapts to the building thermal management needs in summer and winter, and solves the problem of excessive indoor cooling and a surge in heating energy consumption caused by continuous heat dissipation of a single radiant cooling material in winter.

[0012] 2. The present invention has a layered composite integrated structure. The temperature-sensitive hydrogel layer and the composite photothermal phase change material layer are directly bonded together. The overall structure is regular and the thickness is controllable. It can be directly laid on the outer surface of the building roof enclosure structure without complicated construction process. It is suitable for various civil and industrial building roof renovation and new construction projects. Attached Figure Description

[0013] Figure 1 This is a simulation and optimization data graph showing the combination of LCST and phase transition temperature in this invention; Figure 2 This is a simulation and optimization data diagram of the double-layer thickness of the present invention; Figure 3 This is an experimental test diagram of the leakage rate of the composite photothermal phase change material of the present invention; Figure 4 This is a latent heat test curve of the composite photothermal phase change material of the present invention; Figure 5 This is a diagram showing the heating and cooling curves of the composite photothermal phase change material of the present invention. Figure 6 The temperature change curve and SEM characterization test image of the composite photothermal phase change material of the present invention are shown below. Figure 7 This is a test graph showing the reflectance of the thermosensitive hydrogel layer of the present invention; Figure 8 This is a test diagram of the water absorption and evaporation of the thermosensitive hydrogel of the present invention; Figure 9 This is a test diagram of the water absorption and evaporation of the thermosensitive hydrogel of the present invention; Figure 10 This is a temperature change rate test graph for the present invention; Detailed Implementation

[0014] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0015] according to Figure 1-10 As shown, an all-season adaptive building thermal management system includes a thermosensitive hydrogel layer and a composite photothermal phase change material layer stacked from top to bottom. The thermosensitive hydrogel layer has a PNIPAM and PAM copolymer crosslinked network structure, internally doped with sodium chloride and calcium chloride. The thermosensitive hydrogel layer has a low critical solution temperature (LCST) of 32℃ and a thickness of 0.5cm. The composite photothermal phase change material layer is formed by vacuum impregnation of octadecane with a three-dimensional aerogel framework made of cellulose nanofibers, carbon nanotubes, graphene oxide, and silane coupling agent, with a phase change temperature of 28℃ and a thickness of 3cm.

[0016] The mass ratio of PNIPAM to PAM monomers is 4:1.

[0017] The temperature-sensitive hydrogel layer was soaked in a 10wt% sodium chloride solution to regulate LCST, and calcium chloride was uniformly dispersed inside the cross-linked network.

[0018] The raw materials for preparing the composite photothermal phase change material layer include 1.55wt% cellulose nanofiber suspension, multi-walled carbon nanotubes, graphene oxide suspension, and APTES silane coupling agent. After acidification at pH=4 and vacuum freeze-drying to obtain an aerogel framework, it is impregnated with octadecane.

[0019] The liquid phase leakage rate of the composite photothermal phase change material layer is less than 1.5% after continuous heating at 90℃ for 24 hours.

[0020] The thermosensitive hydrogel layer has a solar radiation reflectance of 71% when the temperature is above 32℃ and 16% when the temperature is below 32℃, with an infrared emissivity of 0.8 across the entire temperature range; and a saturated water absorption rate of 6g / g at 20℃ and 80% relative humidity.

[0021] The thermosensitive hydrogel layer and the composite photothermal phase change material layer are directly bonded together and laid on the outer surface of the building roof enclosure structure.

[0022] Working principle: In summer, the ambient temperature is generally higher than 28℃. When the temperature exceeds 32℃ during the daytime high-temperature conditions, the upper temperature-sensitive hydrogel layer triggers a reversible structural response, increasing the solar radiation reflectivity to 71%. This effectively blocks the intrusion of high-intensity shortwave solar radiation from the outside into the room. At the same time, relying on the stable infrared emissivity of 0.8 across the entire range, it radiates outward to dissipate the heat accumulated on the roof. Furthermore, with a high saturated water absorption rate of 6g / g, the cooling effect is further enhanced through water evaporation. At this time, the octadecane medium in the lower composite photothermal phase change material layer is in a liquid state. With the help of the porous thermal insulation performance of the three-dimensional aerogel skeleton, it blocks the vertical conduction of heat. At the same time, it absorbs excess ambient heat through the latent heat of phase change, buffering the impact of extreme high temperatures on indoor temperature rise, and effectively reducing the building's cooling energy consumption in summer. In winter, the ambient temperature is generally below 32℃ and usually below 28℃. The temperature-sensitive hydrogel layer maintains its permeability, reducing solar radiation reflectivity to 16%, maximizing the transmission of short-wave solar radiation, and efficiently transferring light energy to the underlying materials. Octadecylane within the composite photothermal phase change material layer solidifies, continuously absorbing transmitted solar energy during the day and storing it as latent heat of phase change. At night, when the ambient temperature drops and indoor heat is lost, it continuously replenishes indoor heat through condensation and heat release, reducing winter heating energy consumption. During the spring and autumn transitional seasons, the ambient temperature ranges from 28℃ to 32℃. The system achieves dynamic adaptive regulation. When the temperature is above 28℃, the phase change material activates its heat storage buffer in advance, suppressing the stuffiness caused by slight daytime temperature increases. When the temperature is below 32℃, the hydrogel maintains high light transmittance, fully utilizing natural light and heat to supplement indoor temperature, effectively mitigating the impact of diurnal temperature fluctuations on the indoor environment, and significantly extending the building's year-round constant temperature duration.

[0023] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A year-round adaptive building thermal management system, characterized in that: It includes a thermosensitive hydrogel layer and a composite photothermal phase change material layer stacked from top to bottom; the thermosensitive hydrogel layer is a cross-linked network structure of PNIPAM and PAM copolymer, with sodium chloride and calcium chloride doped inside; the low critical solution temperature (LCST) of the thermosensitive hydrogel layer is 32℃, and the thickness is 0.5cm; the composite photothermal phase change material layer is a three-dimensional aerogel framework prepared by cellulose nanofibers, carbon nanotubes, graphene oxide, and silane coupling agent, which is then vacuum impregnated with octadecane, with a phase change temperature of 28℃ and a thickness of 3cm.

2. The all-season adaptive building thermal management system according to claim 1, characterized in that: The mass ratio of PNIPAM to PAM monomers is 4:

1.

3. The all-season adaptive building thermal management system according to claim 1, characterized in that: The temperature-sensitive hydrogel layer was soaked in a 10wt% sodium chloride solution to regulate LCST, and calcium chloride was uniformly dispersed inside the cross-linked network.

4. The all-season adaptive building thermal management system according to claim 1, characterized in that: The raw materials for preparing the composite photothermal phase change material layer include 1.55wt% cellulose nanofiber suspension, multi-walled carbon nanotubes, graphene oxide suspension, and APTES silane coupling agent. After acidification at pH=4 and vacuum freeze-drying to obtain an aerogel framework, it is impregnated with octadecane.

5. The all-season adaptive building thermal management system according to claim 1, characterized in that: The liquid phase leakage rate of the composite photothermal phase change material layer is less than 1.5% after continuous heating at 90℃ for 24 hours.

6. The all-season adaptive building thermal management system according to claim 1, characterized in that: The thermosensitive hydrogel layer has a solar radiation reflectance of 71% when the temperature is above 32℃ and 16% when the temperature is below 32℃, with an infrared emissivity of 0.8 across the entire temperature range; and a saturated water absorption rate of 6g / g at 20℃ and 80% relative humidity.

7. The all-season adaptive building thermal management system according to claim 1, characterized in that: The thermosensitive hydrogel layer and the composite photothermal phase change material layer are directly bonded together and laid on the outer surface of the building roof enclosure structure.

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