Season-adaptive double-layer phase change wall and regulation method thereof

Abstract

This application relates to the field of building energy conservation technology, and discloses a seasonally adaptive double-layer phase change wall and its control method. The phase change wall, from the indoor side to the outdoor side, includes a base wall, an inner protective layer, a first phase change functional layer, a heat insulation layer, a second phase change functional layer, and an outer protective layer. The first phase change functional layer uses a ternary core material of decanoic acid-lauric acid-palmitic acid with a phase change of 14-16 ℃; the second phase change functional layer uses a ternary core material of decanoic acid-stearic acid-myristic acid with a phase change of 24-26 ℃. Both phase change core materials are adsorbed inside a porous, highly thermally conductive carbon-based carrier and encapsulated by an interfacial microcapsule shell. This application avoids heat crosstalk by decoupling through a centrally located heat insulation layer structure; effectively enhances latent heat and suppresses supercooling by using a trace-doped ternary system; and solves the problems of slow heat conduction and long-term circulating leakage by combining the carbon-based carrier and microcapsules for dual shaping, thus achieving efficient and stable fully passive dual-season thermal control of the building.

Description

Technical Field

[0001] This application relates to the field of building energy conservation technology, and in particular to a seasonally adaptive double-layer phase change wall and its control method. Background Technology

[0002] With the increasing global climate change and stricter building energy efficiency standards, the application of phase change energy storage technology in building envelopes has gradually become a research hotspot. Phase change materials, with their unique latent heat storage capacity, can absorb or release large amounts of heat through changes in their physical state, thereby regulating the indoor thermal environment and reducing building energy consumption to a certain extent.

[0003] Early phase change walls mostly used materials with a single phase change temperature, making it difficult to simultaneously meet the dual-temperature control requirements of summer insulation and winter heat preservation. Therefore, existing technologies have gradually proposed double-layer or multi-layer phase change wall structures incorporating two different phase change materials. For example, some technical solutions arrange a high-temperature phase change layer for summer and a low-temperature phase change layer for winter within the wall, or use mechanical transmission devices to assist in control.

[0004] However, in practical engineering applications and under long-term, complex alternating natural climate conditions, the aforementioned existing technologies still reveal the following significant shortcomings: Firstly, in the selection of microscopic phase change core materials, existing technologies mostly adopt conventional binary eutectic fatty acid systems (such as pure decanoic acid-stearic acid or decanoic acid-lauric acid systems). Although these conventional binary systems can match specific phase change temperature ranges to a certain extent, their research and development ideas are mostly limited to finding the absolute lowest eutectic point. This traditional formulation method has revealed problems in practical applications, such as limited potential for increasing latent heat density and difficulty in further optimizing crystal regularity. At the same time, fatty acid materials inherently have high nucleation energy barriers, which easily lead to supercooling. This results in the material not being able to crystallize and release heat in time when the ambient temperature reaches the phase change point, thereby weakening the dynamic temperature regulation efficiency of the phase change wall.

[0005] Secondly, regarding macroscopic structure and thermodynamic coordination, existing double-layer phase change walls often involve simply physically bonding phase change layers from different temperature zones together, or rely heavily on complex mechanical active transmission devices for heat flow isolation. Under purely passive operating conditions, when the environment is in the transitional seasons of spring and autumn or experiences drastic diurnal temperature fluctuations, severe heat crosstalk and backflow can easily occur between the high-temperature and low-temperature phase change layers. This thermal coupling makes the phase change material highly susceptible to accidental triggering in non-target seasons, severely weakening the overall seasonal adaptability and thermal control efficiency of the system.

[0006] Furthermore, regarding the thermal response of microscopic material systems, existing technologies mostly employ traditional porous mineral materials such as diatomaceous earth as adsorbent carriers. Although these materials are relatively inexpensive, their thermal conductivity is generally low (only about 0.04~0.07 W / (m·K) at room temperature). This severely restricts the rate of heat transfer within the phase change layer, resulting in a significant lag in the thermal response of the material system to sudden changes in ambient temperature.

[0007] Finally, regarding long-term cyclic stability, existing technologies often employ surface encapsulation with monomer polymers such as styrene-acrylic emulsions. Due to the relative rigidity of their polymer chains, when the phase change core material undergoes long-term solid-liquid phase change cycles, inevitably accompanied by approximately 10% volume expansion and contraction, the encapsulation shell is prone to microcracks due to thermomechanical stress concentration. This further leads to the gradual leakage of the liquid phase change core material, causing a decrease in the latent heat capacity of the wall after hundreds of thermal cycles, making it difficult to meet the engineering requirements for long-life building components. Summary of the Invention

[0008] To address the aforementioned issues, this application aims to provide a seasonally adaptive double-layer phase change wall and its control method, which can effectively block interlayer thermal interference and achieve dynamic adaptive thermal control in both winter and summer.

[0009] To achieve the above objectives, the technical solution adopted in this application is as follows: A seasonally adaptive double-layer phase change wall, comprising, from the indoor side to the outdoor side, a base wall, an inner protective layer, a first phase change functional layer, a heat insulation layer, a second phase change functional layer, and an outer protective layer; the first phase change functional layer contains a first composite phase change material, the phase change core material of which is a decanoic acid-lauric acid-palmitic acid ternary eutectic system with a first phase change temperature range; the second phase change functional layer contains a second composite phase change material, the phase change core material of which is a decanoic acid-stearic acid-myristic acid ternary eutectic system with a second phase change temperature range, and the second phase change temperature range is higher than the first phase change temperature range; The first composite phase change material and the second composite phase change material both include a porous high thermal conductivity carbon-based carrier and a phase change core material adsorbed inside the porous high thermal conductivity carbon-based carrier; and the outer surface of the porous high thermal conductivity carbon-based carrier is covered with an interface microcapsule encapsulation shell layer.

[0010] Through this technology, the central insulation layer not only functions as a traditional static thermal barrier but also reduces heat crosstalk between the first and second phase change functional layers during dynamic phase change cycles. This mitigates the possibility of false triggering of the phase change material or backflow of heat during transitional seasons or periods of significant diurnal temperature variation. Secondly, at the microscopic level, the porous, highly thermally conductive carbon-based carrier utilizes its rich micro / nano-scale pore network to lock in the liquid phase change core material and leverages its excellent phonon heat transfer characteristics to construct high-speed heat transfer channels, thereby effectively improving the material's thermal response rate. Simultaneously, the externally encapsulated interface microcapsule shell exhibits high cross-linking chemical density, effectively resisting the permeation and leakage of tiny molecules. Furthermore, it acts like a microscopic balloon, effectively absorbing approximately 10% of the volumetric expansion stress generated during the solid-liquid phase change process, demonstrating excellent thermomechanical stress buffering capacity and long-term thermal cycling stability.

[0011] Furthermore, in the decanoic acid-lauric acid-palmitic acid ternary system, the mass percentage of decanoic acid is 65%-70%, the mass percentage of lauric acid is 28%-32%, and the mass percentage of palmitic acid is 1%-3%.

[0012] This technique avoids the conventional approach of pursuing the absolute lowest eutectic point in traditional ternary systems, instead employing a "micro-doping" method that deviates from the eutectic point. A trace amount of a long-chain third fatty acid molecule (palmitic acid) is forcibly introduced into the main binary system (decanoic acid-lauric acid), causing localized spatial geometry adjustments at the microscopic crystal growth interface, acting as a crystallization guide. This not only preserves the macroscopic crystal structure of the main fatty acid but also effectively lowers the nucleation energy barrier and suppresses the inherent supercooling phenomenon of the fatty acid system. Under specific verification conditions, a specific ratio range can optimize crystal regularity without significantly deviating from the core phase transition temperature, and has the technical potential to increase the latent heat of this first composite system by approximately 10%-15%.

[0013] Furthermore, in the decanoic acid-stearic acid-myristic acid ternary system, decanoic acid accounts for 80%-85% of the mass, stearic acid accounts for 12%-18% of the mass, and myristic acid accounts for 1%-3% of the mass.

[0014] This technique utilizes the specific long-chain structure of trace amounts of myristic acid to form appropriate steric hindrance within the decanoic acid-stearic acid lattice, acting as an induction center for heterogeneous nucleation and altering the crystallization kinetics. Similar to the aforementioned control mechanism of winter phase transition systems, the trace doping ratio can effectively overcome the technical bottleneck of limited latent heat enhancement in pure binary systems without causing uncontrollable drift in the overall phase transition temperature. Under accelerated thermodynamic verification conditions, the microscopic modification within this ratio range demonstrated a promising effect of increasing the latent heat of the second composite system by approximately 8%-12%, thereby providing a superior heat storage capacity for building envelopes with the same wall thickness.

[0015] Furthermore, the porous, highly thermally conductive carbon-based carrier is expanded graphite, and the interface microcapsule encapsulation shell is a polyurethane microcapsule wall.

[0016] Through this technique, the three-dimensional graphene network inside expanded graphite can serve as a heterogeneous nucleation center to promote fatty acid crystallization. Especially after high-temperature pre-drying to remove microporous moisture, its capillary adsorption efficiency and the thermal conductivity of the composite material show a significant improvement. The polyurethane microcapsule walls are generated in situ through a condensation reaction between isocyanate and polyol at the emulsion interface. Its polymeric block copolymer structure maintains a low mass loss rate even after undergoing over 500 cycles of severe thermal stress, providing a solid material guarantee for the long-term service life of the phase change wall.

[0017] Furthermore, the outer protective layer is a metal plate or waterproof coating; the heat insulation layer is polystyrene foam or rock wool; and the inner protective layer is gypsum board or waterproof gypsum board.

[0018] Through this technical means and by selecting the best materials, the outer protective layer can effectively resist external climate erosion; the inner protective layer can meet the flatness requirements of interior decoration while also providing structural support; and the insulation layer made of polystyrene foam or rock wool, with its low thermal conductivity and lightweight physical properties, complements the thermal resistance of the phase change functional layers on both sides, thus balancing economy and process operability as much as possible in engineering implementation.

[0019] Furthermore, the first phase transition temperature range is 14 ℃ to 16 ℃.

[0020] Furthermore, the second phase transition temperature range is 24 ℃ to 26 ℃.

[0021] This application also provides a method for heat transfer regulation of a seasonally adaptive double-layer phase change wall as described above, including: When the heat from the external environment is transferred to the second phase change functional layer through the outer protective layer, and the temperature of the second phase change functional layer rises to the second phase change temperature range, the decanoic acid-stearic acid-myristic acid ternary eutectic system undergoes a phase change and absorbs heat. At the same time, the heat insulation layer blocks the remaining heat from being transferred to the indoor side. When indoor heat is transferred to the first phase change functional layer through the inner protective layer, and the temperature of the first phase change functional layer drops to the first phase change temperature range, the decanoic acid-lauric acid-palmitic acid ternary eutectic system undergoes a phase change and releases latent heat. At the same time, the insulation layer reduces heat loss to the outside.

[0022] This design creates a control system that does not rely on external energy input or mechanical transmission. Driven by the alternating temperatures of the actual natural environment, it cleverly utilizes the inherent temperature gradient between the inside and outside of the building, achieving a leap in the thermal performance of the walls from "static insulation" to "dynamic seasonal adaptive control".

[0023] In summary, this application has the following beneficial effects: 1. This application employs an asymmetric design of "first phase change functional layer - insulation layer - second phase change functional layer," combined with two ternary eutectic systems within specific phase change temperature ranges, to provide targeted heat interception and compensation for winter and summer operating conditions. The centrally located insulation layer substantially reduces heat crosstalk between the two phase change layers during dynamic phase change cycles, helping to reduce the possibility of false triggering of phase change materials or heat backflow during the spring and autumn transition seasons or when there are significant day-night temperature differences. Simultaneously, the dual-structure design at the microscopic level, employing a porous, highly thermally conductive carbon-based carrier and an interface microcapsule encapsulation shell, not only effectively enhances the overall thermal response rate of the system by utilizing the high thermal conductivity of the carbon-based network, but also effectively absorbs the volume expansion stress generated during material phase change and resists micro-molecular leakage due to the cross-linked chemical density and buffer elasticity of the microcapsule walls. This provides the wall with better thermomechanical stress buffering capacity and long-term thermal cycling stability.

[0024] 2. This application employs a "micro-doping" strategy that deviates from the absolute minimum eutectic point in the specific mass ratio design of the composite phase change material. By introducing trace amounts of a third fatty acid molecule (palmitic acid or myristic acid) with a relatively long carbon chain into the decanoic acid-lauric acid or decanoic acid-stearic acid binary system, the local spatial geometry at the microcrystalline growth interface can be moderately adjusted, acting as a crystallization guide or dislocation nucleus. This not only effectively reduces the nucleation energy barrier of the system and suppresses the inherent supercooling phenomenon of the fatty acid system without significantly shifting the core phase transition temperature, but also demonstrates the effect of optimizing crystal regularity, possessing the technical potential to increase the latent heat of the composite system by approximately 8%-15%, thereby providing a better heat storage capacity for building envelope structures with the same wall thickness.

[0025] 3. This application uses expanded graphite as a porous, highly thermally conductive adsorption carrier and polyurethane microcapsules as an encapsulation shell to form a more efficient synergistic protection through a nested physical and chemical approach. The three-dimensional graphene network inside the expanded graphite can serve as a heterogeneous nucleation center to further promote fatty acid crystallization, and after removing microporous moisture through a combined process, the macroscopic thermal conductivity of the composite material can be significantly improved. Furthermore, the polyurethane microcapsule wall, due to its combination of rigid and flexible polymer block copolymer structure, is expected to maintain a low mass loss rate even after undergoing high-frequency, severe alternating thermal stress, providing a solid material science guarantee for long-term service life in practical engineering applications.

[0026] 4. The materials and temperature ranges of each functional layer in this application have been specifically matched to different scenarios, demonstrating excellent adaptability for engineering implementation. They precisely meet the typical indoor thermal environment requirements of winter and summer, avoiding performance confusion under complex meteorological conditions. The combination of inner and outer protective layers with traditional static insulation materials (such as polystyrene foam or rock wool) ensures the wall's resistance to external climate erosion and basic support performance, while forming an effective "dynamic-static" thermal resistance complementarity with the phase change layers on both sides. This approach effectively balances the system's economy with the feasibility of on-site construction at the engineering implementation level. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the structure of an optional seasonally adaptive double-layer phase change wall in an embodiment of this application; Figure 2 This is a line graph comparing the latent heat values ​​of the second phase change functional layer (CA-SA-MA system) in the embodiments of this application; Figure 3 This is a line graph comparing the latent heat values ​​of the first phase change functional layer (CA-LA-PA system) in the embodiments of this application; Figure 4 This is a schematic diagram showing the arrangement of measuring points for testing the heat transfer performance of a phase change wall, which is an optional feature of this application embodiment.

[0028] The components are: 1. Base wall; 201. Inner protective layer; 202. First phase change functional layer; 203. Insulation layer; 204. Second phase change functional layer; 205. Outer protective layer. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solutions of this application, the technical solutions of this application will be further described below in conjunction with the accompanying drawings and embodiments.

[0030] Example 1 Reference Figure 1 This embodiment provides a seasonally adaptive double-layer phase change wall, which, from the indoor side to the outdoor side, includes a base wall 1, an inner protective layer 201, a first phase change functional layer 202, a heat insulation layer 203, a second phase change functional layer 204, and an outer protective layer 205. The layers are tightly bonded together using high thermal conductivity structural adhesive or mechanical anchors to reduce interlayer contact thermal resistance and ensure continuous heat conduction. The first phase change functional layer 202 contains a first composite phase change material, the phase change core of which is a decanoic acid-lauric acid-palmitic acid ternary eutectic system with a first phase change temperature range. The second phase change functional layer 204 contains a second composite phase change material, the phase change core of which is a decanoic acid-stearic acid-myristic acid ternary eutectic system with a second phase change temperature range higher than the first phase change temperature range. Both the first and second composite phase change materials comprise a porous, highly thermally conductive carbon-based support and a phase change core material adsorbed within the porous, highly thermally conductive carbon-based support; the porous, highly thermally conductive carbon-based support is coated with an interface microcapsule encapsulation shell. In this spatial topology, the centrally located thermal insulation layer 203 not only serves the traditional static thermal blocking function but also substantially reduces thermal crosstalk between the first phase change functional layer 202 and the second phase change functional layer 204 during dynamic phase change cycling, thereby reducing the possibility of false triggering of the phase change material or backflow of heat during the transitional seasons of spring and autumn or when there are drastic temperature differences between day and night. At the microscopic level, the porous, highly thermally conductive carbon-based support utilizes its rich micro- and nano-scale pore structure network to provide strong capillary forces to lock in the liquid phase change core material, and leverages its excellent phonon heat transfer characteristics to construct a high-speed heat transfer channel, thereby effectively improving the overall thermal response rate of the material. Meanwhile, the outer layer of the interface microcapsule encapsulation has high cross-linked chemical density, which can not only effectively resist the permeation and leakage of small molecules, but also absorb about 10% of the volume expansion stress generated by the phase change material during the solid-liquid phase change process, just like a micro balloon, showing good thermomechanical stress buffering ability and long-term thermal cycling stability.

[0031] Furthermore, in the phase change core material of the first composite phase change material (i.e., the decanoic acid-lauric acid-palmitic acid ternary system), the preferred mass percentage of decanoic acid is 65%-70%, lauric acid is 28%-32%, and palmitic acid is 1%-3%. This mass percentage configuration avoids the conventional approach of solely pursuing the absolute lowest eutectic point in traditional research, instead employing a "micro-doping" method that deviates from the eutectic point. A trace amount of the long-chain (containing 16 carbon atoms) third fatty acid molecule, palmitic acid, is forcibly introduced into the binary system dominated by 10-carbon decanoic acid and 12-carbon lauric acid. This can induce local spatial geometry adjustments at the microcrystalline growth interface, acting as a crystallization guide or dislocation nucleus. This microcrystalline lattice perturbation not only does not destroy the macroscopic crystal structure of the main fatty acids but also effectively lowers the nucleation energy barrier of the system, suppressing the inherent supercooling phenomenon of the fatty acid system. Under specific engineering verification conditions, this specific ratio range can optimize crystal regularity without significantly deviating from the core phase transition temperature, and has the technical potential to increase the latent heat of the first composite system by about 10%-15%.

[0032] Furthermore, in the phase change core material of the second composite phase change material (i.e., the decanoic acid-stearic acid-myristic acid ternary system), the mass percentage of decanoic acid is 80%-85%, the mass percentage of stearic acid is 12%-18%, and the mass percentage of myristic acid is 1%-3%. This configuration utilizes the specific long-chain structure of trace amounts of myristic acid to form appropriate steric hindrance in the decanoic acid-stearic acid lattice, serving as an induction center for heterogeneous nucleation to alter the crystallization kinetics. Similar to the control mechanism of the aforementioned winter phase change system (first phase change functional layer 202), this trace doping ratio can effectively overcome the technical bottleneck of limited latent heat enhancement in pure binary systems without causing uncontrollable drift in the overall phase change temperature. Under accelerated thermodynamic verification conditions, the micro-modification within this ratio range showed a good expected effect of increasing the latent heat of the second composite system by approximately 8%-12%, thereby providing a better heat storage capacity for the building envelope without increasing the wall thickness by the same amount.

[0033] Furthermore, the porous, high thermal conductivity carbon-based carrier can specifically be expanded graphite, and the interface microcapsule encapsulation shell can specifically be the polyurethane microcapsule wall. In material preparation and implementation, the three-dimensional graphene network inside the expanded graphite can serve as a heterogeneous nucleation center to promote fatty acid crystallization. Especially after high-temperature pre-drying treatment to remove microporous moisture during the preparation stage, combined with vacuum impregnation or melt blending processes, its capillary adsorption efficiency and the macroscopic thermal conductivity of the composite material show a significant improvement, with the thermal conductivity jumping to the range of 0.6-1.2 W / (m·K). The polyurethane microcapsule wall can be generated in situ through the condensation reaction of isocyanate and polyol at the emulsion interface. Its high-molecular block copolymer structure, combining rigid and flexible segments, allows the encapsulated material to maintain a low mass loss rate of approximately 0.2%-0.3% even after undergoing more than 500 severe alternating thermal stress shocks, providing a solid material science guarantee for the long-term service life and anti-leakage performance of the phase change wall.

[0034] Furthermore, the outer protective layer 205 of the wall can be made of metal plate or high-performance waterproof coating; the insulation layer 203 can be made of polystyrene foam or rock wool; and the inner protective layer 201 can be made of gypsum board or waterproof gypsum board. Through targeted selection of building materials, the outer protective layer 205 can effectively resist external ultraviolet rays, rainwater and other climatic erosion; the inner protective layer 201 can meet the flatness requirements of interior decoration while also taking into account the structural support of the wall; and the insulation layer 203, made of materials such as polystyrene foam or rock wool, with its low thermal conductivity and lightweight physical properties, forms an effective thermal resistance complement to the phase change functional layers on both sides in terms of thermal performance, taking into account both system economy and on-site construction process operability at the engineering implementation level.

[0035] Furthermore, the first phase change temperature range is set to 14°C to 16°C, which is mainly adapted to the typical indoor thermal environment requirements in winter.

[0036] Furthermore, the second phase change temperature range is set to 24°C to 26°C, which is mainly adapted to the typical indoor thermal environment requirements in summer. By setting the dual temperature zones independently, the performance of the composite wall can be avoided under complex meteorological conditions.

[0037] Example 2 This implementation uses thermodynamic testing to compare and verify the differences in latent heat density and microcrystalline characteristics between the "micro-doped" ternary eutectic composite system used in this application and the pure binary system and the conventional high-proportion doped ternary system.

[0038] For the decanoic acid-lauric acid-palmitic acid (CA-LA-PA) system in the first phase change functional layer (winter condition) and the decanoic acid-stearic acid-myristic acid (CA-SA-MA) system in the second phase change functional layer (summer condition), this test separately set up control and experimental groups for summer and winter conditions: 1. Decanoic acid-stearic acid-myristic acid (CA-SA-MA) system for the second phase change functional layer (summer operating conditions): D1S (Pure Binary Standard Control Group): Contains only the optimally proportioned pure decanoic acid-stearic acid (CA-SA) binary system.

[0039] D2S (Conventional High-Ratio Doping Control Group): Based on the pure CA-SA system, myristic acid (MA) with a mass ratio of 10% is introduced.

[0040] E1S, E2S, and E3S (the experimental group of trace doping in this application): Myristic acid (MA) was introduced at a mass ratio of 1%, 2%, and 3% respectively on the basis of the pure CA-SA system.

[0041] 2. Decanoic acid-lauric acid-palmitic acid (CA-LA-PA) system for the first phase change functional layer (winter operating conditions): D1W (Pure Binary Standard Control Group): Contains only the optimally proportioned pure decanoic acid-lauric acid (CA-LA) binary system.

[0042] D2W (Conventional High-Ratio Doping Control Group): Based on the pure CA-LA system, 10% by mass of palmitic acid (PA) is introduced.

[0043] E1W, E2W, and E3W (the trace doping experimental group of this application): Based on the pure CA-LA system, palmitic acid (PA) with a mass ratio of 1%, 2%, and 3% was introduced, respectively.

[0044] The latent heat value test data is recorded as follows: Under the same accelerated thermodynamic verification conditions, the DSC latent heat values ​​of each sample are shown in Table 1 below: Table 1. Results of DSC Thermodynamic Tests

[0045] Reference Figure 2 and Figure 3Based on the test data in Table 1 above, the test data shows that, in both the summer phase change layer (CA-SA-MA system) and the winter phase change layer (CA-LA-PA system), as the doping amount of the third fatty acid increases from 0% (D1S / D1W group) to 2% (E2S / E2W group), the latent heat value of the composite system shows a significant increase, with increases of 14.14% and 14.06%, respectively. However, when the doping amount is further increased to the conventional 10% (D2S / D2W group), the latent heat increase rate drops back to about 5.1%. This demonstrates that the 1%-3% trace doping limit specified in this application produces excellent nonlinear gains.

[0046] For the D2S and D2W groups (10% doping), excessive intervention of the third component disrupts the originally stable molecular arrangement of the binary eutectic, interferes with the eutectic bonds, and leads to morphological disorder, increased grain boundary defects, and a decrease in overall eutecticness during crystal growth, thus significantly limiting the latent heat gain. Conversely, the 1%-3% trace third component specified in this application does not destroy the core framework structure of the main binary fatty acid but acts as dispersed heterogeneous nucleation sites, effectively inducing uniform crystal refinement. This local perturbation at the micro-lattice level significantly improves the overall crystal regularity and crystal arrangement compactness, reduces intergranular voids and defects, and allows for more complete enthalpy release during the phase transition, ultimately achieving a 10%-15% increase in latent heat.

[0047] Comparative data from the two systems show that the latent heat value of the system exhibits a highly consistent trend of first increasing and then decreasing with the increase of the mass proportion of the third component. Furthermore, when the mass proportion of the third component is 2% (i.e., E2S and E2W groups), both composite phase change systems reach the peak state of latent heat release. At the same time, their DSC curves maintain a single, sharp melting peak, ensuring that phase separation does not occur and maintaining excellent single-phase eutectic stability and thermal cycling life. Therefore, a 2% mass proportion is the optimal ratio for maximizing the latent heat of phase change and optimizing the structure in this application.

[0048] To verify the thermophysical properties of the composite phase change material described in this application, as well as the dynamic thermal control effect of the seasonally adaptive double-layer phase change wall on a macroscopic scale, this embodiment provides corresponding performance testing and verification methods and results.

[0049] For the composite phase change material prepared in this application that adsorbs porous, highly thermally conductive carbon-based support (expanded graphite), the thermal conductivity was qualitatively and quantitatively tested using the transient hot-wire method. The specific testing steps included: assembling probes at both ends of the powdered sample; placing it in a standard rectangular container, smoothing and compacting it, and fixing the sensor sheet; fixing it under constant pressure with a 500g weight and then placing it in a constant-temperature chamber; and monitoring and measuring after the chamber reached thermal equilibrium.

[0050] Results: Using expanded graphite as the adsorption carrier, the adsorption capacity of the phase change material can be increased to 75-85 wt%, and the macroscopic thermal conductivity of the composite material is significantly improved to 0.6-1.2 W / (m·K). Compared with the scheme using traditional diatomaceous earth carrier, the thermal conductivity is improved by about 3-5 times, thus physically verifying that the high-speed heat transfer channel of the carbon-based network can effectively improve the endothermic and exothermic response efficiency of the phase change material.

[0051] To verify the actual seasonal adaptability of the double-layer phase change wall structure proposed in this application, a one-dimensional wall heat transfer test bench was constructed. Combined with... Figure 4 The diagram showing the wall measuring point setup illustrates the arrangement of main measuring points a-1 to a-7 along the wall's heat transfer direction (thickness 50 mm + 115 mm + 50 mm), from the outdoor side to the indoor side, along with auxiliary verification measuring point sequences b-1 to b-7. Temperature responses at each level are collected in real-time by simulating outdoor temperature wave functions in both winter and summer.

[0052] The results show that under summer conditions, when external heat waves intrude and cause the temperature at the outer measuring point to exceed 24-26 ℃, the summer phase change layer (CA-SA-MA) undergoes a phase change and efficiently absorbs heat. Combined with the thermal blocking effect of the central insulation layer, this effectively reduces the heat flow entering the room, and is expected to reduce the summer air conditioning load by more than 30%. Under winter conditions, when the temperature near the indoor measuring point fluctuates to 14-16 ℃, the winter phase change layer (CA-LA-PA) undergoes a phase change and actively releases latent heat, thereby compensating for indoor heat loss, and the overall energy saving rate can reach 25%-40%. The above comprehensive evaluation based on dynamic monitoring of the measuring points fully confirms that the double-layer phase change wall of this application has excellent seasonal adaptive heat transfer regulation capabilities.

[0053] Based on the aforementioned performance tests, this embodiment further confirms the multidimensional synergistic effect produced by combining a porous, highly thermally conductive carbon-based support (expanded graphite) with a microcapsule encapsulation shell (polyurethane). Regarding adsorption and thermal stability, the polyurethane microcapsules not only provide a stable support and secondary channels for the easily agglomerated expanded graphite, but the carbon skeleton generated by its thermal decomposition also acts as a densification support for the loose, worm-like carbon layer of the expanded graphite. The two work synergistically to form a high-strength, low-thermal-conductivity composite insulating carbon layer.

[0054] Furthermore, in terms of interfacial mechanics and weather resistance, polyurethane microcapsules, acting as an interfacial transition layer, significantly improve the poor compatibility between pure expanded graphite and the polymer matrix, thereby enhancing the mechanical strength of the system. Addressing the weakness of pure expanded graphite's susceptibility to moisture absorption and failure, the hydrophobic properties of polyurethane microcapsules provide an excellent protective barrier. Accelerated aging environmental testing shows that this shaped composite material, after being immersed in water at 70 °C for 168 hours, still maintains excellent flame retardant properties and thermodynamic regulation activity, achieving a synergistic gain of long-term effectiveness and long lifespan that cannot be achieved by a single material.

[0055] Example 3 This embodiment provides a heat transfer control method for a seasonally adaptive double-layer phase change wall as described above, the specific control steps of which include: Under summer operating conditions, when the heat from the external environment is transferred to the second phase change functional layer through the outer protective layer, and the local temperature in the second phase change functional layer rises to the second phase change temperature range of 24°C to 26°C, the decanoic acid-stearic acid-myristic acid ternary eutectic system adsorbed therein passively triggers solid-liquid phase change and absorbs the heat from the environment. At the same time, the heat insulation layer in the middle further blocks the remaining heat from being transferred to the indoor side, thereby weakening the impact of outdoor heat waves on the indoor environment. In winter, when indoor heat is transferred to the first phase change functional layer through the inner protective layer, and the temperature of the first phase change functional layer drops to the first phase change temperature range of 14°C to 16°C due to fluctuations in ambient temperature, the decanoic acid-lauric acid-palmitic acid ternary eutectic system undergoes a liquid-solid phase change and releases the pre-stored latent heat to compensate for part of the indoor heat loss. At the same time, the middle insulation layer can reduce the continued loss of indoor heat to the outdoor side.

[0056] The heat transfer control method in this embodiment forms a passive control system that does not rely on external active energy input or complex mechanical transmission devices. Driven by the actual alternating temperature of the natural environment, it makes reasonable use of the inherent temperature gradient inside and outside the building, enabling the building envelope to have an adaptive thermal resistance response capability, thereby promoting a smooth transition of the wall thermal performance from the traditional "static insulation" to "dynamic seasonal adaptive control".

[0057] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the appended claims and their equivalents.

Claims

1. A seasonally adaptive double-layer phase change wall, characterized in that, From the indoor side to the outdoor side, it includes, in sequence, the base wall, the inner protective layer, the first phase change functional layer, the heat insulation layer, the second phase change functional layer, and the outer protective layer; The first phase change functional layer includes a first composite phase change material, and the phase change core material of the first composite phase change material is a ternary eutectic system of decanoic acid-lauric acid-palmitic acid with a first phase change temperature range. The second phase change functional layer includes a second composite phase change material. The phase change core material of the second composite phase change material is a decanoic acid-stearic acid-myristic acid ternary eutectic system with a second phase change temperature range, and the second phase change temperature range is higher than the first phase change temperature range. The first composite phase change material and the second composite phase change material both include a porous high thermal conductivity carbon-based carrier and a phase change core material adsorbed inside the porous high thermal conductivity carbon-based carrier; and the outer surface of the porous high thermal conductivity carbon-based carrier is covered with an interface microcapsule encapsulation shell layer.

2. The seasonally adaptive double-layer phase change wall according to claim 1, characterized in that, In the decanoic acid-lauric acid-palmitic acid ternary system, the mass percentage of decanoic acid is 65%-70%, the mass percentage of lauric acid is 28%-32%, and the mass percentage of palmitic acid is 1%-3%.

3. The seasonally adaptive double-layer phase change wall according to claim 1, characterized in that, In the decanoic acid-stearic acid-myristic acid ternary system, the mass percentage of decanoic acid is 80%-85%, the mass percentage of stearic acid is 12%-18%, and the mass percentage of myristic acid is 1%-3%.

4. The seasonally adaptive double-layer phase change wall according to claim 1, characterized in that, The porous, highly thermally conductive carbon-based carrier is expanded graphite, and the interface microcapsule encapsulation shell is a polyurethane microcapsule wall.

5. The seasonally adaptive double-layer phase change wall according to claim 1, characterized in that, The outer protective layer is a metal plate or a waterproof coating; the heat insulation layer is polystyrene foam or rock wool; and the inner protective layer is gypsum board or waterproof gypsum board.

6. The seasonally adaptive double-layer phase change wall according to claim 1, characterized in that, The first phase transition temperature range is 14 ℃ to 16 ℃.

7. The seasonally adaptive double-layer phase change wall according to claim 1, characterized in that, The second phase transition temperature range is 24 ℃ to 26 ℃.

8. A method for heat transfer regulation of a seasonally adaptive double-layer phase change wall as described in any one of claims 1-7, characterized in that, include: When the heat from the external environment is transferred to the second phase change functional layer through the outer protective layer, and the temperature of the second phase change functional layer rises to the second phase change temperature range, the decanoic acid-stearic acid-myristic acid ternary eutectic system undergoes a phase change and absorbs heat. At the same time, the heat insulation layer blocks the remaining heat from being transferred to the indoor side. When indoor heat is transferred to the first phase change functional layer through the inner protective layer, and the temperature of the first phase change functional layer drops to the first phase change temperature range, the decanoic acid-lauric acid-palmitic acid ternary eutectic system undergoes a phase change and releases latent heat. At the same time, the insulation layer reduces heat loss to the outside.

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