Passive radiation-cold storage composite box body and preparation method thereof

Abstract

The invention discloses a passive radiation-cold storage composite box body and a preparation method. The box body sequentially comprises a composite radiation film, a heat insulation layer and a cold storage layer from outside to inside. The outer-layer radiation film is composed of an elastic organic matrix and high-reflection inorganic particles such as barium sulfate, has high solar reflectivity and mid-infrared high emissivity, and can effectively restrain solar absorption and achieve radiation heat dissipation in the daytime. The heat insulation layer is made of XPS, EPS, aerogel felt and other low-heat-conduction materials so as to reduce external heat transfer. Phase change microcapsules are dispersed in the cold storage layer, and flake graphite and other high-thermal-conductivity fillers can be added to improve the cold transfer efficiency and temperature uniformity. And the phase-change material realizes automatic cold storage and cold release through a latent heat mechanism, so that the temperature in the box body is kept stable. Through the synergistic effect of radiation refrigeration, heat insulation and phase change cold storage, long-time and recyclable passive cold chain temperature control is achieved, and the device has the advantages of being simple and convenient in structure, high in cost performance, flexible in application, uniform in internal temperature distribution and the like.

Description

Technical Field

[0001] This invention relates to the field of thermal management and energy-saving material application technology, specifically to a passive radiation-cold storage composite box and its preparation method. Background Technology

[0002] During cold chain transportation and storage, maintaining the stability of goods in low-temperature environments typically relies on active refrigeration systems such as compressor refrigeration, electrically driven cooling coils, or refrigerant circulation. However, these systems generally suffer from high energy consumption, complex structures, and difficult maintenance, making them unsuitable for continuous operation in remote areas or environments without electricity. Furthermore, traditional insulated boxes often rely solely on insulation materials (such as polystyrene and polyurethane) to slow down heat exchange, lacking the ability to store cold and regulate temperature, making them prone to rapid temperature rises during long-term transportation.

[0003] On the other hand, recent research on passive radiative cooling technology has shown that by using films with high emissivity in the mid-infrared band and high reflectivity in the solar band, heat dissipation through radiation into external space can be achieved without energy input, and the surface temperature can be reduced to below the ambient temperature, thus achieving passive cooling. However, most existing radiative cooling films are applied to building roofs or device surfaces and have not yet been integrated with cold chain storage structures.

[0004] Therefore, existing cold chain storage and transportation equipment generally suffers from high energy consumption and ineffective coupling of radiative refrigeration and cold storage functions, making it difficult to achieve long-term heat preservation and cyclic cold storage performance.

[0005] Existing technology (application number: 202121467809.7) discloses a cold chain box with phase change material, the structure of which includes: the inner wall of the box is filled with composite vacuum nanoplates, the top of the box is equipped with a lid, and low-temperature rubber sealing strips are set at the contact points; a support is set inside the box, and a phase change energy storage plate is fixed on the support, forming a space for placing items below the energy storage plate. The phase change energy storage plate adopts an independent energy storage block encapsulating phase change material, and is fixed by a pressure plate and a fastening structure. This cold chain box mainly relies on the heat insulation of the vacuum nanoplate and the solid-liquid transformation of the phase change energy storage plate to achieve cooling and heat preservation. However, the drawback of this patent is that relying solely on a single layer of phase change energy storage plate at the top for cold energy release can easily cause a large temperature gradient and uneven temperature distribution inside the box, affecting the actual temperature control effect.

[0006] Therefore, there is an urgent need for a new passive radiation-cooling composite box structure that can simultaneously solve the following technical challenges: 1) the problem that traditional cold chain boxes easily absorb solar radiation and have high external heat load during the day; 2) the problem of high energy consumption during the operation of existing cold chain storage and transportation equipment; 3) the problem of uneven temperature distribution inside the box due to the single arrangement of phase change materials and the difficulty in uniformly transferring cold energy; 4) the problem of poor synergy between radiation cooling and phase change cooling functions in existing structures. Summary of the Invention

[0007] Purpose of the invention: This invention addresses the problems of traditional cold chain containers relying on external energy, limited cold storage duration, and large temperature fluctuations. It overcomes the shortcomings of existing structures, such as insufficient radiative heat dissipation efficiency, low cold storage utilization rate, and limited thermal insulation performance. It provides a passive radiative-cold storage composite container and its preparation method, which is suitable for cold chain storage and transportation and passive temperature control applications. Through the synergistic design of multi-layer functional structures, it realizes a long-term, cyclical passive cold chain storage and insulation process.

[0008] Technical Solution: This invention discloses a passive radiation-cold storage composite enclosure, which comprises, from the outside to the inside, a composite radiation film, a heat insulation layer, and a cold storage layer. The composite radiation film achieves cooling through spectrally selective reflection and radiation, the heat insulation layer reduces the heat input from the external environment, and the cold storage layer maintains a constant temperature inside the enclosure through the solidification and melting release of phase change materials.

[0009] Preferably, the outermost layer is a composite radiation film consisting of barium sulfate particles doped into an elastic matrix. The barium sulfate particles have high solar reflectivity and high infrared emissivity, with a particle size distribution of 300-500 nm and a filling mass fraction of 10-50 wt%. The thickness of the composite radiation film is 50-1000 μm.

[0010] Preferably, the barium sulfate particles can be replaced or partially replaced with other inorganic particles with high reflectivity or mid-infrared emissivity, wherein the inorganic particles are selected from one or more of the following: zirconium dioxide, titanium dioxide, silicon dioxide, aluminum oxide, zinc oxide, calcium carbonate, hollow glass microspheres, and particles with a layered or sheet-like structure and a reflectivity of 80-99% in the 300-2500 nm band.

[0011] Preferably, the composite radiation film uses polymeric materials such as polydimethylsiloxane (PDMS), polyurethane, polyacrylate, or fluorosilicone elastomer as the elastic matrix, and the matrix is ​​doped with inorganic fillers that have high solar reflectivity and high infrared selective emission performance.

[0012] The insulation layer of the intermediate layer has a thermal conductivity of no more than 0.035 W·m. -1 ·K -1 Thermally conductive insulation materials are used to insulate against external heat conduction and support the overall structure. Preferred thermally conductive insulation materials include extruded polystyrene foam (XPS), expanded polystyrene (EPS), polyurethane foam, aerogel felt, or vacuum insulation panels.

[0013] The cold storage layer is preferably a gypsum-based composite layer, which uses gypsum as the matrix and disperses phase change microcapsules inside to store and release cold energy under temperature change conditions. The average particle size of the phase change microcapsules is 500 μm to 3 mm, the shell-core mass ratio is 1:3 to 1:100, and the mass fraction is preferably 30-50 wt%.

[0014] Preferably, the phase transition temperature range of the core layer material of the phase change microcapsule is -50 to 30 °C, and the core layer material includes the following types: low-temperature hydrocarbons / fluorocarbons (typical temperature range -50 to -10 °C): low-carbon alkanes, fluorocarbon refrigerants; medium-low temperature hydrocarbons (typical temperature range -10 to 10 °C): C10-C15 straight-chain alkanes, water / ice, PEG-based phase change materials; medium-temperature hydrocarbons and esters (typical temperature range 10 to 20 °C): C16–C17 straight-chain alkanes, some aliphatic esters; high-temperature hydrocarbons and hydrated salts (typical temperature range 20 to 30 °C): C18 straight-chain alkanes, near-room temperature hydrates (such as Na2HPO2·12H2O).

[0015] Preferably, the shell material of the phase change microcapsule can be selected from natural polymers or organic / inorganic composite materials, such as sodium alginate, chitosan, gelatin, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylamide or copolymers thereof, as well as inorganic particles or composite systems such as silica, alumina, titanium dioxide, and calcium carbonate.

[0016] Preferably, to enhance the efficiency of cold energy transfer, flake graphite powder is incorporated into the cold storage layer as a thermal conductivity enhancing filler. The mass fraction of the flake graphite powder is 1-30 wt%, preferably 3-25 wt%, and its average maximum particle size is 5-200 μm.

[0017] Preferably, the flake graphite powder can be partially or completely replaced with other high thermal conductivity particles, such as alumina powder, boron nitride powder, metal micro-flakes (copper, aluminum), carbon nanotubes or graphene sheets, etc.

[0018] Preferably, the present invention also proposes a method for preparing a passive radiation-cold storage composite box, comprising the following steps:

[0019] S1. Preparation of radiation film composite paste: Mix the organic elastomer matrix material with its curing agent and high refractive index inorganic filler evenly, and then degas it to obtain a radiation film composite paste with coatability.

[0020] S2. Outer coating curing: The composite slurry is coated on one side of the heat insulation substrate and cured by heating or room temperature to form an outer radiation film with high infrared radiation performance.

[0021] S3. Cold storage layer laying and slurry preparation: The phase change microcapsules are evenly laid on the other side of the insulation layer in a single or multi-layer stacking manner; the gypsum slurry is prepared by mixing gypsum:water:thermal conductive particles in a mass ratio of 100:30-50:3-25.

[0022] S4. Casting and molding: The gypsum slurry is poured onto the surface of the heat insulation layer with microcapsules, allowing the slurry to penetrate into the gaps between the microcapsules and cover their surface. The slurry is then lightly vibrated to release air, and cured at room temperature for 1-2 hours or at 40-60 °C for 30-60 minutes to form a cold storage layer.

[0023] S5. Container Structure Assembly: After the cold storage layer has cured, the composite panels forming the radiant membrane, insulation substrate, and cold storage layer are assembled with the container frame structure. Through bonding and interlocking methods, the composite panels form the side walls, bottom plate, and top cover structure, creating a closed container.

[0024] Preferably, the process further includes a cooling operation step, wherein the cooling operation involves placing the box in an open state in a cold source environment at least 5 to 30 °C below the phase change temperature of the phase change material, so that the phase change microcapsules in the cold storage layer complete the phase change cold storage process from liquid to solid; the cooling time is 0.5 to 12 h, and is adjusted according to the temperature difference between the cold source temperature and the phase change temperature to ensure that the cold storage layer reaches a fully cooled state.

[0025] Beneficial Effects: This invention achieves significant passive temperature control performance through the synergistic effect of radiative cooling, phase change cold storage, and insulation structures. The composite radiative film combines high solar reflectivity with high infrared emissivity in the atmospheric window, effectively suppressing solar absorption and rapidly dissipating heat during the day, reducing the heat load on the enclosure from the source. The insulation layer significantly reduces the transfer of external heat inward, increasing the duration of cold storage. The phase change microcapsules in the cold storage layer utilize a latent heat regulation mechanism to automatically release and store cold under temperature fluctuations, achieving long-term temperature stability. Simultaneously, the addition of highly thermally conductive fillers such as flake graphite powder constructs heat conduction channels, improving cold transfer efficiency and phase change utilization, making the cold storage process more thorough. Through the synergy of multiple layers, this composite enclosure achieves efficient and recyclable cold chain cold storage and insulation effects. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the passive radiation-cold storage composite box of the present invention.

[0027] Figure 2 This is a flowchart of the passive radiation-cold storage composite box preparation method of the present invention.

[0028] Attached reference numerals: 1-composite radiant film, 2-sealing strip, 3-insulation layer, 4-cold storage layer, 5-refrigerated items. Detailed Implementation

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. The test materials used in the embodiments can be obtained through conventional means.

[0030] Example 1:

[0031] This invention provides a passive radiation-cold storage composite enclosure, such as... Figure 1 As shown, it includes a composite radiation film 1, a heat insulation layer 3, and a cold storage layer 4 arranged sequentially from the outside to the inside.

[0032] The outermost composite radiation film 1 can be an elastic matrix doped with barium sulfate particles, wherein the barium sulfate particles have a particle size distribution of 300-500 nm and a filling mass fraction of 10-50 wt%. The outermost composite radiation film 1 can also be an elastic matrix doped with inorganic particles, wherein the inorganic particles are selected from one or more of the following: zirconium dioxide, titanium dioxide, silicon dioxide, hexagonal aluminum nitride, alumina, zinc oxide, calcium carbonate, hollow glass microspheres, and particles with a layered or sheet-like structure and a reflectivity of 80-99% in the 300-2500 nm band.

[0033] The composite radiation film 1 uses polydimethylsiloxane, polyurethane, polyacrylate or fluorosilicone elastomer as the elastic matrix, and inorganic fillers are incorporated into the matrix; the thickness of the composite radiation film 1 is 50-1000 μm.

[0034] The insulation layer 3 of the intermediate layer has a thermal conductivity of no more than 0.035 W·m. -1 ·K -1 The thermal conductivity insulation material is selected from one or more of the following: extruded polystyrene foam, expanded polystyrene foam, polyurethane foam, aerogel felt, and vacuum insulation board; the thickness of the insulation layer 3 is 5-50 mm.

[0035] The cold storage layer 4 is a gypsum-based composite layer, in which phase change microcapsules are dispersed in the gypsum matrix. The average particle size of the phase change microcapsules is 500 μm to 3 mm, and the shell-core mass ratio is 1:3 to 1:100. The mass fraction of the phase change microcapsules in the cold storage layer 4 is 30 to 50 wt%, and the phase change temperature range is -50 to 30 °C.

[0036] The phase change temperature range of the core layer material of the phase change microcapsules is -50 to 30 °C. The core layer material includes low-temperature hydrocarbons / fluorocarbons, medium-low temperature hydrocarbons, medium-temperature hydrocarbons and esters, and high-temperature hydrocarbons and hydrated salts. The low-temperature hydrocarbons / fluorocarbons include low-carbon alkanes and fluorocarbon refrigerants, with a typical temperature range of -50 to -10 °C. The medium-low temperature hydrocarbons include C10–C15 straight-chain alkanes, water / ice, and PEG-based phase change materials, with a typical temperature range of -10 to 10 °C. The medium-temperature hydrocarbons and esters include C16–C17 straight-chain alkanes and some aliphatic esters, with a typical temperature range of 10 to 20 °C. The high-temperature hydrocarbons and hydrated salts include C18 straight-chain alkanes and near-room temperature salt hydrates, with a typical temperature range of 20 to 30 °C.

[0037] The shell material of the phase change microcapsule is selected from one or more of the following natural polymers, organic polymers and inorganic composite materials, including sodium alginate, chitosan, gelatin, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylate or copolymers thereof, as well as silicon dioxide, alumina, titanium dioxide, calcium carbonate or composite systems thereof.

[0038] The cold storage layer 4 may be doped with flake graphite powder, with a mass fraction of 1-30 wt%, an optimal mass fraction of 3-25 wt%, and an average maximum particle size of 5-200 μm. The cold storage layer 4 may also be doped with materials having a thermal conductivity of 10-500 W·m. -1 ·K -1 The particles include alumina powder, boron nitride powder, metal flakes, carbon nanotubes, and graphene sheets.

[0039] Invention principle: The passive radiation-cold storage composite box of the present invention comprehensively utilizes multiple thermal management principles such as radiation spectrum regulation, phase change latent heat storage, and thermal insulation. Through the synergistic design of multi-layer functional structures, the box realizes a long-term, cyclical passive cold chain storage and insulation process.

[0040] In the natural environment, all objects dissipate heat to the outside world through infrared radiation. If a material surface has high reflectivity to short-wave solar radiation and high emissivity in the atmospheric window band (8–13 μm), its radiant heat energy can penetrate the atmosphere and dissipate directly into outer space. This effectively suppresses solar radiation absorption and rapidly dissipates heat during the day, reducing the thermal load on the enclosure from the source. Based on this principle, this invention incorporates a composite radiative film on the outer layer of the enclosure:

[0041] The outer radiation film is a composite system made of an elastic matrix (such as PDMS) doped with barium sulfate or other highly reflective and highly emissive inorganic particles, which combines mechanical flexibility with spectral selectivity. Its high solar reflectivity can effectively reflect more than 90% of visible light and near-infrared radiation during the day, significantly reducing solar energy absorption; at the same time, it maintains high emissivity in the mid-infrared band, which allows it to dissipate heat quickly through its own radiation, reducing heat accumulation on the outer surface of the enclosure.

[0042] The intermediate insulation layer uses low thermal conductivity materials (such as XPS, EPS or aerogel felt) to block heat conduction, isolate external temperature fluctuations from the cold storage layer, and improve the efficiency of cold storage utilization.

[0043] The cold storage layer uses gypsum as its matrix and disperses phase change microcapsules within it, providing both structural strength and energy regulation. The core material of the phase change microcapsules (such as paraffin wax or water) releases cold energy and undergoes a solid-liquid transition when the temperature rises; it absorbs cold energy and re-solidifies when the temperature drops. Through this latent heat mechanism of phase change, the cold storage layer can automatically release and store cold energy in environments with fluctuating temperatures, acting as a thermal buffer to maintain a stable internal temperature.

[0044] Meanwhile, the introduction of flake graphite powder or other high thermal conductivity fillers (such as alumina, boron nitride, etc.) into the cold storage layer creates a thermal conductivity pathway in the gypsum matrix through its layered structure, thereby improving the cold transfer rate and the temperature uniformity inside the cold storage layer, and making the phase change process more complete.

[0045] Example 2:

[0046] like Figure 2 As shown, a method for preparing a passive radiation-cold storage composite box includes:

[0047] S1. Preparation of radiation film composite paste: Mix PDMS reagent Sylgard 184 as main agent, curing agent and barium sulfate particles at a ratio of 10:1:(2-6) evenly, and degas for 5-10 min to obtain a coatable composite paste.

[0048] S2. Outer coating and curing: The PDMS composite paste is coated with a thickness of 50–1000 μm onto one side of a 15 mm thick polystyrene foam and cured at 60–90 °C for 1–3 h to form a radiation film.

[0049] S3. Cold storage layer laying and slurry preparation: Phase change microcapsules with a particle size of 2.5 mm and a phase change temperature of 18℃ are laid at a density of 4 capsules / cm³. 2 The density of the single layer is uniformly laid on the other side of the polystyrene foam; a castable gypsum slurry is prepared by mixing gypsum: water: flake graphite in a mass ratio of 100:(30–50):(3–25).

[0050] S4. Casting and molding: The gypsum-graphite slurry is poured onto the surface of the insulation layer with microcapsules, allowing the slurry to penetrate into the gaps between the microcapsules and cover their surface. After slight vibration to remove air, it is cured at room temperature for 1–2 h or at 40–60 °C for 30–60 min to form a cold storage layer with a thickness of 0.3 cm.

[0051] S5. Enclosure Assembly: Cut the heat insulation board with radiation film and the formed cold storage layer to a 10×10 cm internal cavity size, then glue the four side walls together and install the bottom plate, keeping the radiation film facing outwards and the cold storage layer facing inwards; the top cover is equipped with a sealing strip to allow it to open and close to the side walls. After overall curing, a composite enclosure structure with a 10×10 cm internal space is formed.

[0052] Example 3:

[0053] A method for preparing a passive radiation-cold storage composite box includes:

[0054] S1. Preparation of radiation film composite slurry: Acrylic resin, photoinitiator 2-hydroxy-2-methylphenylacetone and TiO2 particles with a particle size of 300–500 nm are mixed evenly at a mass ratio of 10:0.2:(10–40), and after degassing, a coatable radiation film slurry is obtained.

[0055] S2. Radiation film coating and curing: The slurry is coated with a thickness of 50–400 μm onto one side of a 15 mm thick polyurethane foam insulation layer, and cured into a film by irradiation with ultraviolet light for 3–5 min.

[0056] S3. Cold Storage Layer Laying and Thermally Conductive Composite Gypsum Slurry: Microcapsule Laying: Microcapsules with PEG-1000 as the core material, a core-shell ratio of 1:10, a particle size of 500–700 μm, and a phase transition temperature of 15 ℃ are uniformly laid on the other side of the insulation layer in a single-layer dense packing manner. Preparation of Gypsum-Graphene Sheet Slurry: Gypsum: Water: Graphene Sheet = 100 : (35–50) : (1–10) are mixed to obtain a castable thermally conductive gypsum slurry.

[0057] S4. Casting and curing: The gypsum-graphene slurry is cast onto the microcapsule layer, compacted and degassed, and then cured at 40–60 ℃ for 30–60 min to obtain a cold storage layer with a thickness of 2–5 mm.

[0058] S5. Box assembly: The heat insulation board with radiation film and the molded cold storage layer are cut to the internal cavity size of 10×10 cm, and then the four side walls, bottom plate and top cover are assembled by adhesive to form a completely closed cold storage box. The top cover is equipped with a sealing strip to maintain good sealing performance.

[0059] Example 4:

[0060] A method for preparing a passive radiation-cold storage composite box includes:

[0061] S1. Preparation of radiation film composite slurry: Mix fluorosilicone elastomer, crosslinking agent and hollow glass microspheres with a particle size of 350–500 nm at a ratio of 10:1:(20–50) until homogeneous. Degas under reduced pressure for 5–8 min to obtain a low-density high-reflectivity film slurry.

[0062] S2. Outer layer coating and curing: The above slurry is coated on one side of a 10 mm thick aerogel felt with a thickness of 80–300 μm, and cured at 60 ℃ for 2 h to form a lightweight radiation film layer.

[0063] S3. Cold Storage Layer Laying and Composite Slurry Preparation: Microcapsule Laying: Microcapsules with C16–C17 alkanes as cores, a core-shell ratio of 1:15, an average particle size of 1.5 mm, and a phase transition temperature of 17 ℃ were selected and laid in a double-layer staggered arrangement on the back side of the aerogel felt. Preparation of Gypsum-Aluminum Sheet Composite Slurry: A castable slurry was prepared by mixing gypsum: water: aluminum sheets (thickness 10–30 μm) = 100 : (30–40) : (2–15).

[0064] S4. Casting and curing: The gypsum-aluminum sheet slurry is cast onto the surface of the microcapsules, so that it completely covers the capsules and penetrates into the gaps. After curing at room temperature for 1–2 hours, a cold storage layer with a thickness of about 3 mm is obtained.

[0065] S5. Assembly of the enclosure structure: Cut the enclosure to 10 × 10 cm dimensions and glue the four walls and bottom plate in sequence. Install the top cover with the radiant membrane facing outwards and the cold storage layer facing inwards. The top cover is fixed with a sealing strip in an openable and closable manner. After the entire structure is cured, a composite enclosure structure is formed.

[0066] To verify the performance of the passive radiation-cold storage composite box preparation method proposed in this invention, three comparative examples are provided for comparison.

[0067] Comparative Example 1:

[0068] A method for preparing a passive radiation-cooling composite box without phase change microcapsules includes:

[0069] S1. Preparation of radiation film composite paste: Mix PDMS main agent, curing agent and barium sulfate particles in a mass ratio of 10:1:(2–6) evenly and degas for 5–10 min to obtain a coatable composite paste.

[0070] S2. Outer coating and curing: The PDMS composite paste is coated with a thickness of 50–1000 μm onto one side of a 1.5 cm thick polystyrene foam board and cured at 60–90 °C for 1–3 h to form a radiation film.

[0071] S3. Preparation of cold storage layer slurry: Mix gypsum: water: flake graphite in a mass ratio of 100:(30–50):(3–25) and stir evenly to obtain a castable gypsum-graphite slurry.

[0072] S4. Casting and molding: The gypsum-graphite slurry is directly poured onto the surface of the insulation layer, and after slight vibration to remove air, it is cured at room temperature for 1–2 h or at 40–60 °C for 30–60 min to obtain a cured layer with a thickness of about 3 mm.

[0073] S5. Enclosure Assembly: Cut the heat insulation board with radiation film and the curing layer to a 10×10 cm inner cavity size, then glue the four side walls in sequence and install the bottom plate with the radiation film facing outwards. The top cover is fixed with a sealing strip in an openable / closable manner. After overall curing, a composite enclosure structure is formed.

[0074] Comparative Example 2:

[0075] A method for manufacturing a box consisting only of a thermal insulation layer, comprising:

[0076] S1. Insulation layer preparation: 1.5 cm thick polystyrene foam board is selected as the main structure, without radiation film coating treatment or cold storage layer.

[0077] S2. Sheet cutting: Cut the insulation board to meet the specifications of 10×10 cm inner cavity size.

[0078] S3. Box assembly: The cut panels are glued to the four side walls in sequence and the bottom plate is installed to form a cavity structure; the top cover is equipped with a sealing strip and assembled into an openable structure.

[0079] The enclosure obtained in this comparative example relies solely on the insulation layer for temperature control, and does not include radiative cooling or phase change cold storage structures.

[0080] Comparative Example 3:

[0081] Prior art (application number: 202121467809.7) discloses a cold chain box with phase change material, the structure of which includes: the inner wall of the box is filled with composite vacuum nanoplates, the top of the box is provided with a lid, and low-temperature rubber sealing strips are provided at the contact points; a support is set inside the box, and a phase change energy storage plate is fixed on the support, forming a space for placing items below the energy storage plate. The phase change energy storage plate adopts an independent energy storage block encapsulating phase change material, and is fixed by a pressure plate and a fastening structure; the box can be equipped with a temperature monitoring module. This cold chain box mainly relies on the heat insulation of the vacuum nanoplates and the solid-liquid transformation of the phase change energy storage plate to achieve cooling and heat preservation.

[0082] This invention achieves a performance leap at the system level through a multi-layered composite structure consisting of a radiative cooling layer, a heat insulation layer, and a cold storage layer. Compared to Comparative Example 2, which relies solely on a heat insulation layer in a traditional insulated box, the outermost composite radiative film of this invention can reflect sunlight from the source and radiate heat to outer space, actively reducing the heat load. Compared to Comparative Example 3, which only has a phase change plate at the top, the cold storage layer of this invention forms a fully enclosed lining and, combined with highly thermally conductive filler, achieves three-dimensional uniform and stable temperature control, fundamentally eliminating the problem of excessive temperature differences between the top and bottom.

[0083] The invention generates a significant synergistic effect among its functional layers: the efficient heat dissipation of the composite radiative film reduces the burden on the insulation layer, enabling it to achieve long-term insulation with a thinner thickness; while the tightly protected cold storage layer can focus on using the latent heat of phase change to buffer internal temperature fluctuations. This systematic design, from source heat blocking to path insulation to end-point temperature stabilization, allows the invention to simultaneously optimize cold retention time, temperature stability, and space utilization without requiring energy input.

[0084] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical principles and scope disclosed in the present invention, such as equivalent selection of material types, reasonable adjustment of proportional parameters, or simple changes to preparation steps, should be covered within the scope of protection of the present invention.

Claims

1. A passive radiation-cold storage composite enclosure, characterized in that, It includes a composite radiation membrane (1), a heat insulation layer (3), and a cold storage layer (4) arranged sequentially from the outside to the inside.

2. The passive radiation-cold storage composite enclosure according to claim 1, characterized in that, The outermost composite radiation film (1) is an elastic matrix doped with barium sulfate particles, wherein the barium sulfate particles have a particle size distribution of 300-500 nm and a filling mass fraction of 10-50 wt%.

3. The passive radiation-cold storage composite enclosure according to claim 1, characterized in that, The outermost composite radiation film (1) is an elastic matrix doped with inorganic particles, which are selected from one or more of the following: zirconium dioxide, titanium dioxide, silicon dioxide, hexagonal aluminum nitride, aluminum oxide, zinc oxide, calcium carbonate, hollow glass microspheres, and particles with a reflectivity of 80-99% in the 300-2500 nm band having a layered or sheet-like structure.

4. The passive radiation-cold storage composite enclosure according to any one of claims 2-3, characterized in that, The composite radiation film (1) uses polydimethylsiloxane, polyurethane, polyacrylate or fluorosilicone elastomer as elastic matrix, and inorganic fillers are incorporated into the matrix; the thickness of the composite radiation film (1) is 50-1000 μm.

5. The passive radiation-cold storage composite enclosure according to claim 1, characterized in that, The insulation layer (3) of the intermediate layer has a thermal conductivity of no more than 0.035 W·m. -1 ·K -1 The thermal conductivity insulation material is selected from one or more of the following: extruded polystyrene foam, expanded polystyrene foam, polyurethane foam, aerogel felt, vacuum insulation board; the insulation layer (3) has a thickness of 5-50 mm.

6. The passive radiation-cold storage composite enclosure according to claim 1, characterized in that, The cold storage layer (4) is a gypsum-based composite layer. Phase change microcapsules are dispersed in the gypsum matrix of the gypsum-based composite layer. The average particle size of the phase change microcapsules is 500 μm to 3 mm, and the shell-core mass ratio is 1:3 to 1:

100. The mass fraction of the phase change microcapsules in the cold storage layer (4) is 30 to 50 wt%, and the phase change temperature range is -50 to 30 °C. The phase change temperature range of the core layer material of the phase change microcapsules is -50 to 30 °C. The core layer material includes low-temperature hydrocarbons / fluorocarbons, medium-low temperature hydrocarbons, medium-temperature hydrocarbons and esters, and high-temperature hydrocarbons and hydrated salts. The low-temperature hydrocarbons / fluorocarbons include low-carbon alkanes and fluorocarbon refrigerants, with a typical temperature range of -50 to -10 °C. The medium-low temperature hydrocarbons include C10–C15 straight-chain alkanes, water / ice, and PEG-based phase change materials, with a typical temperature range of -10 to 10 °C. The medium-temperature hydrocarbons and esters include C16–C17 straight-chain alkanes and some aliphatic esters, with a typical temperature range of 10 to 20 °C. The high-temperature hydrocarbons and hydrated salts include C18 straight-chain alkanes and near-room temperature salt hydrates, with a typical temperature range of 20 to 30 °C. The shell material of the phase change microcapsule is selected from one or more of the following natural polymers, organic polymers and inorganic composite materials, including sodium alginate, chitosan, gelatin, sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylate or copolymers thereof, as well as silicon dioxide, alumina, titanium dioxide, calcium carbonate or composite systems thereof.

7. The passive radiation-cold storage composite enclosure according to claim 6, characterized in that, The cold storage layer (4) is doped with flake graphite powder, the mass fraction of which is 1-30 wt%, the optimal mass fraction is 3-25 wt%, and the average maximum particle size is 5-200 μm.

8. The passive radiation-cold storage composite enclosure according to claim 6, characterized in that, The cold storage layer (4) is doped with a thermal conductivity of 10-500 W·m -1 ·K -1 The particles include alumina powder, boron nitride powder, metal flakes, carbon nanotubes, and graphene sheets.

9. The method for preparing the passive radiation-cold storage composite box according to claim 1, characterized in that, Includes the following steps: S1. Preparation of radiation film composite paste: Mix the organic elastomer matrix material with its curing agent and inorganic filler evenly, and then degas it to obtain a radiation film composite paste with coating properties. S2, Outer Coating and Curing: The composite paste is coated on one side of the heat insulation substrate and cured by heating or room temperature to form an outer radiation film with infrared radiation properties. S3. Cold storage layer laying and slurry preparation: The phase change microcapsules are evenly laid on the other side of the insulation layer in a single layer or multiple layers; the gypsum slurry is prepared by mixing gypsum:water:thermal conductive particles in a mass ratio of 100:30-50:3-25. S4. Casting and molding: The gypsum slurry is poured onto the surface of the heat insulation layer with phase change microcapsules, so that the slurry penetrates into the gaps between the phase change microcapsules and covers their surface. The slurry is then vibrated to remove air, and cured at room temperature for 1-2 hours or at 40-60 °C for 30-60 minutes to form a cold storage layer. S5. Box structure assembly: After the cold storage layer is cured, the composite board that forms the radiation film, heat insulation substrate and cold storage layer is assembled with the box frame structure; by using adhesive and interlocking methods, the composite board forms the side wall, bottom plate and top cover structure, and forms a closed box.

10. The method for preparing the passive radiation-cold storage composite box according to claim 9, characterized in that, It also includes a cooling operation step, which is as follows: the passive radiation-cooling storage composite box is placed in an open state in a cold source environment at least 5~30 ℃ lower than the phase change temperature of the phase change material, so that the phase change microcapsules in the cooling storage layer complete the phase change cooling process from liquid to solid; the cooling time is 0.5~12 h, and is adjusted according to the temperature difference between the cold source temperature and the phase change temperature to ensure that the cooling storage layer reaches a fully cooled state.

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