Stepped heat insulation system for multi-element heat insulation

Abstract

The invention discloses a multi-element heat insulation stepped heat insulation system, and belongs to the technical field of heat protection. The system comprises a plurality of layers of thermal insulation materials formed by alternately bonding aluminized polyimide films and spacing materials, wherein the uppermost layer and the lowermost layer are films; the lower surface of the lowermost layer of film is bonded with a middle layer of hard heat insulation plate; the lowest layer of the system is provided with an inner-layer hard heat insulation plate, and the space between the middle layer and the inner-layer hard heat insulation plate is filled with a composite phase change material. According to the idea of multi-element heat insulation and stepped protection, high-temperature radiation is efficiently reflected and blocked through multiple layers of heat insulation materials, two layers of hard heat insulation plates are used for providing structural support and blocking heat conduction, and heat transfer is delayed by means of phase change latent heat of a composite phase change material. The system integrates three mechanisms of radiation blocking, heat conduction blocking and heat absorption delay, has the advantages of being high in heat insulation performance, small in size and weight and stable and reliable in structure, and is suitable for guaranteeing the thermal environment of a high-speed aircraft airborne test equipment cabin under the near space long-time cruise condition.

Description

Technical Field

[0001] This invention belongs to the field of thermal protection technology, specifically relating to a multi-element heat-blocking tiered thermal insulation system. Background Technology

[0002] With the development of aerospace technology, long-duration cruise missions in near-space for high-speed vehicles (such as hypersonic vehicles) have become an important development direction. When a vehicle flies at high speed in near-space, its surface undergoes intense compression and friction with the thin atmosphere, generating extremely high aerodynamic heating effects and forming a strong external heat flow. This heat is mainly transferred to the interior of the vehicle through thermal radiation and thermal conduction, causing a rapid increase in internal temperature. The airborne test equipment compartment houses sophisticated testing instruments, sensors, and cables, which have strict requirements for the operating environment temperature. Excessively high internal temperatures will lead to performance degradation, data distortion, or even permanent damage. Therefore, designing an efficient, reliable, and lightweight thermal protection system to ensure that the interior of the test equipment compartment remains within a safe temperature range is one of the major challenges in high-speed vehicle design.

[0003] Traditional aircraft cabin thermal protection solutions often employ single insulation materials, such as aerogel felt, inorganic fiber cotton, or homogeneous thermal insulation panels. These materials primarily rely on their low thermal conductivity to block heat conduction, have relatively simple structures, and possess a certain degree of high-temperature resistance. However, facing the continuous, high-intensity, and significantly radiative heat loads generated during long-term cruises in near space, traditional solutions relying solely on thermal conductivity become inadequate. To achieve the required insulation effect, it is often necessary to continuously increase the thickness of the insulation layer. This not only significantly increases the size and weight of the protection system, violating the design principles of lightweight and compact aircraft structures, but may also encroach on valuable equipment installation space.

[0004] In the field of spacecraft thermal control, multi-layer insulation (MLI) is a mature passive thermal control technology. It typically consists of alternating layers of high-reflectivity thin films (such as aluminized polyimide films) and low-thermal-conductivity spacers. Its insulation principle is primarily based on the efficient blocking of radiative heat transfer: each reflective layer reflects most of the incident thermal radiation back, and this layer-by-layer reflection greatly attenuates the radiative heat flow. MLI is particularly effective at suppressing radiative heat transfer in vacuum or low-pressure environments (such as space or near-space).

[0005] On the other hand, aerogel materials are known as "super insulation materials" due to their extremely low thermal conductivity (often lower than that of still air). In particular, silica aerogel insulation boards reinforced with inorganic fibers (such as quartz fibers and ceramic fibers) maintain extremely low thermal conductivity while also possessing good mechanical strength and dimensional stability. They can withstand vibrations and impacts during flight and are suitable as structural load-bearing or structural components.

[0006] Phase change materials (PCMs) offer a unique thermal protection mechanism based on latent heat absorption. During a phase change (such as a solid-liquid phase change), PCMs can absorb and store a significant amount of latent heat while maintaining a relatively constant temperature throughout the process. Applying PCMs to thermal protection systems can effectively delay the transfer of heat to the protected area, buying valuable time to respond to transient or sustained thermal loads—crucial for aircraft requiring long-duration operation. However, traditional solid-liquid PCMs are prone to leakage and flow after melting, affecting system reliability and stability. Utilizing porous media (such as aerogels) to adsorb PCMs, forming shaped composite PCMs, is an effective way to address this problem.

[0007] In summary, single types of thermal protection materials or single thermal barrier mechanisms are insufficient to meet the stringent requirements of high-efficiency, lightweight, and long-term thermal protection for the onboard equipment bays of near-space high-speed aircraft. Therefore, there is an urgent need for an innovative thermal protection system design that can comprehensively utilize multiple thermal barrier mechanisms, and achieve optimal overall thermal insulation performance within limited space and weight constraints through optimized material combinations and gradient structural design. Summary of the Invention

[0008] To address the aforementioned shortcomings of existing technologies, this invention provides a multi-element thermal barrier tiered insulation system to solve the problem that existing single-type thermal protection materials or single thermal barrier mechanisms are insufficient to meet the stringent requirements of high-efficiency, lightweight, and long-term thermal protection for the onboard equipment compartments of near-space high-speed aircraft.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a multi-layer heat-blocking tiered insulation system, comprising an intermediate rigid insulation board and an inner rigid insulation board. The upper surface of the intermediate rigid insulation board is bonded with multiple layers of insulation material, which consists of alternating layers of aluminized polyimide film and spacer material. The uppermost and lowermost layers of the multiple insulation material are both aluminized polyimide film. A composite phase change material is filled between the intermediate and inner rigid insulation boards.

[0010] In the multi-layer thermal barrier tiered insulation system of this invention, multi-layer insulation materials serve as radiation protection layers, the middle rigid insulation board serves as the first thermally conductive barrier and separation layer, the composite phase change material serves as the heat absorption delay layer, and the inner rigid insulation board serves as the second thermally conductive barrier and support layer. This tiered arrangement of "reflection-barrier-heat absorption-re-barrier" constitutes a multi-layered and synergistic thermal barrier path. The multi-layer insulation materials face the external high-temperature environment, mainly dealing with heat flow dominated by radiation; the middle rigid board acts as a physical separator, dividing the system into a high-temperature side and a low-temperature side, and preventing rapid heat transfer downwards; the composite phase change material, as the core heat absorption delay layer, utilizes the latent heat of phase change to absorb a large amount of heat and delay temperature rise; the inner rigid board provides the final thermal barrier and integrates with the equipment compartment wall to ensure structural integrity. This multi-layer thermal barrier tiered insulation system integrates multi-layer insulation materials, rigid aerogel insulation boards, and shaped composite phase change materials into a compact system in a specific tiered sequence. It is not a simple accumulation of materials, but a directional and orderly functional design based on the heat transfer mechanism (radiation → conduction → latent heat absorption → conduction). Compared with single materials or simple composites, the tiered insulation system of this invention achieves comprehensive and progressive reduction of the two main heat transfer modes, radiation and conduction, as well as transient heat accumulation. The system's insulation efficiency is significantly improved. At the same time, the structure is clearly layered and the functions are well-defined, which facilitates optimized design and performance evaluation.

[0011] Furthermore, the multilayer thermal insulation material is composed of at least two layers of aluminized polyimide film and at least one layer of spacer material, alternately stacked and bonded together in parallel. The number of layers in the multilayer thermal insulation material can be increased or decreased according to the actual heat flux density, which defines the basic structure of the multilayer thermal insulation material and ensures the effective realization of its radiative thermal insulation function. By specifying that the uppermost and lowermost layers are both reflective films, the thermal radiation characteristics of the first and last interfaces are optimized, and the overall reflection efficiency is improved.

[0012] Furthermore, both the intermediate rigid insulation board and the inner rigid insulation board are inorganic fiber-reinforced silica aerogel insulation boards, and they are arranged in parallel to each other.

[0013] Furthermore, the inorganic fiber-reinforced silica aerogel insulation board has a density of 280 kg / m³, a tensile strength greater than 1.5 MPa, and a thermal conductivity of 0.02 W / m·K.

[0014] The use of inorganic fiber-reinforced silica aerogel insulation panels allows both the intermediate and inner rigid insulation layers to simultaneously meet the dual requirements of "thermal insulation" and "shape retention." Its low density contributes to system weight reduction; sufficient mechanical strength ensures it is not easily broken in the vibration environment of an aircraft, providing stable support and separation between the upper and lower layers; and its extremely low thermal conductivity provides a fundamental guarantee against heat conduction through the panels. The specific parameter limitations make this technical solution repeatable and industrially feasible, and provide a basis for performance prediction.

[0015] Furthermore, the substrate of the aluminized polyimide film is a polyimide film, and the metal film layer is aluminum; wherein the thickness of the polyimide film is 2 μm to 20 μm, and the thickness of the aluminum film layer is 400 Å to 1200 Å. The polyimide film, as a substrate, possesses excellent high and low temperature resistance, flexibility, and mechanical strength. Vacuum deposition aluminization can form a uniform, dense, and highly reflective aluminum film. The preferred ranges for the film thickness and the aluminum layer thickness represent a balance between ensuring sufficient mechanical strength and flexibility and achieving high reflectivity and low weight.

[0016] Furthermore, the spacer material is glass fiber cloth with a porosity of 0.6 to 0.8, a thermal conductivity of 0.01 W m·K, and a thickness of 1.5 mm to 2.5 mm. Glass fiber cloth is resistant to high temperatures and has stable chemical properties, making it an ideal spacer material for MLI. The porosity of 0.6 to 0.8 ensures that the internal gas is in a near-static state, and convective heat transfer is negligible. The thermal conductivity of 0.01 W m·K indicates that it has high solid thermal resistance. The thickness of 1.5 mm to 2.5 mm provides a suitable interlayer distance, which is beneficial for reducing inter-membrane contact and avoiding unnecessary increase in volume and weight due to excessive thickness.

[0017] By limiting the specific parameters of the spacer material, it is ensured that the spacer layer can effectively isolate the reflective film, minimize the solid heat conduction and residual gas heat conduction between the film layers, and thus give full play to the radiation insulation advantages of the multilayer heat insulation material.

[0018] Furthermore, the composite phase change material is composed of 60% to 80% paraffin wax and 20% to 40% hydrophobic silica aerogel by mass impregnation. Vacuum impregnation ensures that the paraffin wax is fully filled into the nanopores of the aerogel, forming a shaped composite material and solving the leakage problem.

[0019] Furthermore, the latent heat of phase change of the composite phase change material is 113.0 kJ / kg ~ 150.8 kJ / kg, and the thermal conductivity is 0.092 W / m·K.

[0020] Furthermore, the phase transition temperature of the paraffin is 60.82℃, and the latent heat of phase transition is 188.44 kJ / kg; the hydrophobic silica aerogel has a pore size of 20 nm, a porosity greater than 90%, and a hydrophobicity greater than or equal to 99%. These parameters enable the hydrophobic silica aerogel to efficiently adsorb paraffin and prevent its performance from being affected by environmental humidity.

[0021] Furthermore, the intermediate rigid insulation board divides the entire system into a high-temperature side and a low-temperature side; wherein, the high-temperature side is the multi-layer insulation material; the low-temperature side is the composite phase change material; and the inner rigid insulation board is located in the innermost layer of the system.

[0022] The present invention provides a multi-element heat-blocking tiered insulation system, the beneficial effects of which are: 1. The tiered insulation system integrates three mechanisms—radiation blocking, thermal conduction blocking, and heat absorption delay—by setting up multiple layers of insulation materials, a middle layer of rigid insulation board, an inner layer of rigid insulation board, and composite phase change materials. It has the advantages of strong insulation performance, small size and weight, and stable and reliable structure. Its overall insulation efficiency is far higher than that of traditional single-layer or homogeneous insulation solutions. It is suitable for ensuring the thermal environment of the airborne test equipment cabin of high-speed aircraft under long-term cruise conditions in near space.

[0023] 2. The tiered insulation system, through material selection and tiered functional allocation, can significantly reduce the total thickness and weight of the required insulation layer while achieving the same or better insulation performance. This aligns with the trend of lightweight aircraft design and saves valuable cabin space.

[0024] 3. The intermediate and inner rigid insulation panels of the tiered insulation system provide a solid framework for the system, enabling it to withstand mechanical environments such as vibration and overload during high-speed flight, maintain the relative stability of each functional layer, and ensure long-term reliability. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a multi-element heat-blocking tiered insulation system.

[0026] The components include: 1. Aluminum-coated polyimide film; 2. Spacer material; 3. Rigid insulation board in the middle layer; 4. Composite phase change material; and 5. Rigid insulation board in the inner layer. Detailed Implementation

[0027] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0028] like Figure 1As shown, the present invention provides a multi-layer heat-blocking tiered insulation system, comprising an intermediate rigid insulation board 3 and an inner rigid insulation board 5. Preferably, but not limited to, both the intermediate rigid insulation board 3 and the inner rigid insulation board 5 are inorganic fiber-reinforced silica aerogel insulation boards, and are arranged parallel to each other. The inorganic fiber-reinforced silica aerogel insulation board has a density of 280 kg / m³, a tensile strength greater than 1.5 MPa, and a thermal conductivity of 0.02 W / m·K.

[0029] The upper surface of the intermediate rigid insulation board 3 is bonded with multiple layers of insulation material. These multiple layers consist of alternating layers of aluminized polyimide film 1 and spacer material 2, with the aluminized polyimide film 1 forming both the uppermost and lowermost layers. The substrate of the aluminized polyimide film 1 is a polyimide film, and the metal layer is aluminum. The thickness of the polyimide film is 2 μm to 20 μm, and the thickness of the aluminum film layer is 400 Å to 1200 Å. The polyimide film, as the substrate, possesses excellent high and low temperature resistance, flexibility, and mechanical strength. Vacuum deposition aluminization can form a uniform, dense, and highly reflective aluminum film. The preferred ranges for the film thickness and aluminum layer thickness represent a balance between ensuring sufficient mechanical strength and flexibility and achieving high reflectivity and low weight.

[0030] Specifically, the multilayer thermal insulation material is composed of at least two layers of aluminized polyimide film 1 and at least one layer of spacer material 2, alternately stacked and bonded in parallel. The spacer material 2 is fiberglass cloth with a porosity of 0.6 to 0.8, a thermal conductivity of 0.01 W / m·K, and a thickness of 1.5 mm to 2.5 mm. Fiberglass cloth is heat-resistant and chemically stable, making it an ideal spacer material 2 for MLI (Multilayer Insulation). The porosity of 0.6 to 0.8 ensures that the internal gas is in a near-static state, and convective heat transfer is negligible. The thermal conductivity of 0.01 W / m·K indicates its high solid-state thermal resistance. The thickness of 1.5 mm to 2.5 mm provides a suitable interlayer distance, which helps reduce interlayer contact and avoids unnecessary volume and weight increase due to excessive thickness. By limiting the specific parameters of the spacer material 2, it is ensured that the spacer layer can effectively isolate the reflective film, minimizing solid-state heat conduction and residual gas heat conduction between film layers, thereby fully utilizing the radiative thermal insulation advantages of the multilayer thermal insulation material.

[0031] The number of layers in a multi-layer thermal insulation material can be increased or decreased according to the actual heat flux density, which limits the basic structure of the multi-layer thermal insulation material and ensures the effective realization of its radiative thermal insulation function. By specifying that the top and bottom layers are both reflective films, the thermal radiation characteristics of the first and last interfaces are optimized, and the overall reflection efficiency is improved.

[0032] A composite phase change material 4 is filled between the intermediate rigid insulation board 3 and the inner rigid insulation board 5. The specific parameters of the composite phase change material 4 are as follows: it is composed of 60% to 80% paraffin wax and 20% to 40% hydrophobic silica aerogel by mass impregnation. The vacuum impregnation method ensures that the paraffin wax is fully filled into the nanopores of the aerogel, forming a shaped composite material and solving the leakage problem.

[0033] Furthermore, the latent heat of phase change of the composite phase change material 4 is 113.0 kJ / kg ~ 150.8 kJ / kg, and its thermal conductivity is 0.092 W / m·K. The paraffin wax has a phase change temperature of 60.82℃ and a latent heat of phase change of 188.44 kJ / kg; the hydrophobic silica aerogel has a pore size of 20 nm, a porosity greater than 90%, and a hydrophobicity greater than or equal to 99%. These parameters enable the hydrophobic silica aerogel to efficiently adsorb paraffin wax and prevent its performance from being affected by environmental humidity.

[0034] The intermediate rigid insulation board 3 divides the entire system into a high-temperature side and a low-temperature side; wherein, the high-temperature side is the multi-layer insulation material; the low-temperature side is the composite phase change material 4; and the inner rigid insulation board 5 is located in the innermost layer of the system.

[0035] In the multi-layer heat-blocking tiered insulation system of this invention, the aluminized polyimide film 1, as one of the components of the multi-layer insulation material, is alternately bonded and stacked with the spacer material 2 on the outer layer of the tiered insulation system. The uppermost and lowermost layers of the multi-layer insulation material are both aluminized polyimide films 1, which mainly bear the high-temperature heat radiation in the low-pressure environment of near space. When a high-speed aircraft cruises at high speed in near space, due to the low ambient air pressure, radiative heat transfer becomes the main heat load. The surface of the aluminized polyimide film 1 is coated with a highly reflective aluminum film layer. When heat radiation is transferred to the surface of the outermost aluminized polyimide film 1, most of the heat radiation is reflected back to the outside. The remaining transmitted heat radiation is reflected again by the second layer of aluminized polyimide film 1, and so on. After layer-by-layer reflection, only a small amount of heat is transferred to the middle rigid insulation board 3.

[0036] Spacer material 2, as one of the components of the multilayer thermal insulation material, is alternately bonded and stacked with aluminized polyimide film 1 on the outer layer of the tiered thermal insulation system, and each layer of spacer material 2 has a layer of aluminized polyimide film 1 on both its upper and lower surfaces. The main function of spacer material 2 is to physically separate the layers of aluminized polyimide film 1, cut off the continuous path of solid heat conduction, and greatly improve the thermal resistance of the solid by relying on its extremely low thermal conductivity.

[0037] The intermediate rigid insulation board 3 is located between the bottom aluminum-plated polyimide film 1 and the composite phase change material 4. Its main function is to separate the multi-layer insulation material and the composite phase change material 4, so as to prevent the composite phase change material 4 from corroding the metal aluminum film layer of the aluminum-plated polyimide film 1. It divides the tiered insulation system into the upper high-temperature side and the lower low-temperature side. At the same time, the intermediate rigid insulation board 3 itself has a low thermal conductivity and excellent mechanical strength, which improves the solid thermal resistance of the tiered insulation system and maintains the structural stability.

[0038] The composite phase change material 4 is located between the intermediate rigid heat insulation board 3 and the inner rigid heat insulation board 5. Its main function is to absorb a small amount of heat transferred from the intermediate rigid heat insulation board 3 to the low-temperature side and provide a certain solid thermal resistance to prevent heat from entering the airborne test equipment compartment, delay the heat transfer process, and improve the flight time of the aircraft.

[0039] The inner rigid insulation board 5 is located at the innermost layer of the entire tiered insulation system and is in direct contact with the wall of the airborne test equipment compartment. Its main function is to isolate the composite phase change material 4 from the airborne test equipment compartment, while improving the thermal resistance of the solid and maintaining the stability of the structure.

[0040] Through the above design, when the high-speed aircraft cruises at high speed in near space, the large amount of aerodynamic heat generated outside the aircraft is mainly transferred to the tiered heat insulation system in the form of thermal radiation. The heat is first transferred to the high-temperature side of the tiered heat insulation system, which is a multi-layer heat insulation material composed of alternating layers of aluminized polyimide film 1 and spacer material 2. The thermal radiation is reflected layer by layer by the multi-layer aluminized polyimide film 1, and only a small amount of thermal radiation is transferred to the middle rigid heat insulation board 3. Other aerodynamic heat transferred to the high-temperature side of the tiered heat insulation system is mainly transferred in the form of thermal conduction. The spacer material 2 is glass fiber cloth, which has high solid thermal resistance and can effectively hinder the heat conduction transfer on the high-temperature side. After all the heat is transferred to the middle rigid heat insulation board 3, it will be transferred almost entirely in the form of thermal conduction on the low-temperature side. The low-temperature side is a composite phase change material 4, which absorbs the transferred heat by relying on its phase change characteristics, preventing the heat from entering the airborne test cabin and delaying the heat transfer process, effectively improving the cruise time of the high-speed aircraft. The intermediate rigid insulation board 3 and the inner rigid insulation board 5 provide regional isolation for the entire tiered insulation system, and improve the thermal resistance of solids and maintain structural stability.

[0041] In summary, this invention proposes a multi-layered thermal insulation system with multiple thermal barriers. On the high-temperature side, multi-layered thermal insulation materials are used to block radiative heat transfer in the high-temperature environment of near space. On the low-temperature side, phase change materials are used to absorb heat and delay heat transfer. Qualitative phase change materials are constructed based on hydrophobic silica aerogel to solve the leakage problem of phase change materials. Two layers of rigid thermal insulation boards are used to block heat conduction and maintain the structural stability of the multi-layered thermal insulation system. The multi-layered thermal barrier comprehensively improves the thermal insulation performance and significantly reduces the volume and weight, ensuring a safe and stable thermal environment for the airborne test equipment cabin of high-speed aircraft during long-term cruise in near space.

Claims

1. A multi-element heat-barrier tiered insulation system, characterized in that, It includes an intermediate rigid heat insulation board (3) and an inner rigid heat insulation board (5). The upper surface of the intermediate rigid heat insulation board (3) is bonded with multiple layers of heat insulation material. The multiple layers of heat insulation material are composed of alternating bonding of aluminized polyimide film (1) and spacer material (2). The uppermost and lowermost layers of the multiple layers of heat insulation material are both aluminized polyimide film (1). A composite phase change material (4) is filled between the intermediate rigid heat insulation board (3) and the inner rigid heat insulation board (5).

2. The multi-element heat-blocking tiered insulation system according to claim 1, characterized in that, The multilayer thermal insulation material is composed of at least two layers of aluminized polyimide film (1) and at least one layer of spacer material (2) stacked and bonded in parallel.

3. The multi-element thermal barrier cascade insulation system according to claim 1 or 2, characterized in that, The intermediate rigid insulation board (3) and the inner rigid insulation board (5) are both inorganic fiber reinforced silica aerogel insulation boards, and are arranged in parallel to each other.

4. The multi-element heat-blocking tiered insulation system according to claim 3, characterized in that, The inorganic fiber-reinforced silica aerogel insulation board has a density of 280 kg / m³, a tensile strength greater than 1.5 MPa, and a thermal conductivity of 0.02 W / m·K.

5. The multi-element thermal barrier tiered insulation system according to claim 1 or 2, characterized in that, The substrate of the aluminized polyimide film (1) is a polyimide film, and the metal film layer is aluminum; wherein, the thickness of the polyimide film is 2 μm to 20 μm, and the thickness of the aluminum film layer is 400 Å to 1200 Å.

6. The multi-element thermal barrier cascade insulation system according to claim 1 or 2, characterized in that, The spacer material (2) is glass fiber cloth with a porosity of 0.6 to 0.8, a thermal conductivity of 0.01 W / m·K, and a thickness of 1.5 mm to 2.5 mm.

7. The multi-element heat-blocking tiered insulation system according to claim 1, characterized in that, The composite phase change material (4) is composed of 60% to 80% paraffin and 20% to 40% hydrophobic silica aerogel by vacuum impregnation.

8. The multi-element thermal barrier tiered insulation system according to claim 7, characterized in that, The latent heat of phase change of the composite phase change material (4) is 113.0 kJ / kg ~ 150.8 kJ / kg, and the thermal conductivity is 0.092 W / m·K.

9. The multi-element thermal barrier tiered insulation system according to claim 7, characterized in that, The paraffin wax has a phase transition temperature of 60.82℃ and a latent heat of phase transition of 188.44 kJ / kg; the hydrophobic silica aerogel has a pore size of 20 nm, a porosity greater than 90%, and a hydrophobicity greater than or equal to 99%.

10. The multi-element thermal barrier tiered insulation system according to claim 9, characterized in that, The intermediate rigid insulation board (3) divides the entire system into a high-temperature side and a low-temperature side; wherein, the high-temperature side is the multi-layer insulation material; the low-temperature side is the composite phase change material (4); and the inner rigid insulation board (5) is located in the innermost layer of the system.

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