Radiation refrigeration storage device based on phase change volume change self-regulation

Abstract

This invention discloses a radiative cooling and cold storage device based on self-regulation of phase change volume change, belonging to the field of sky radiative cooling technology. It solves the problem that traditional direct-contact structures struggle to achieve controllable storage and efficient utilization of cooling capacity. The device includes a radiative cooling plate, a phase change cold storage unit, and an insulation layer. The phase change cold storage unit is located inside the insulation layer and below the radiative cooling plate. The phase change cold storage unit includes a sealed cavity and a phase change material filled within it. During the phase change process, as the volume of the phase change material changes, the sealed cavity adaptively adjusts its height, shifting towards the upper surface of the radiative cooling plate, thereby altering the contact state between the cavity and the plate. This invention achieves adjustment of radiative cooling capacity under different operating conditions by adaptively regulating contact thermal resistance through phase change volume change, thus improving cooling capacity utilization efficiency and mitigating the day-night cooling mismatch problem.

Description

Technical Field

[0001] This invention relates to the field of sky radiation cooling and phase change energy storage technology, and in particular to a radiation cooling and cold storage device based on phase change volume change self-regulating interface thermal resistance. Background Technology

[0002] Sky radiation cooling is a typical zero-energy passive cooling technology. Its core mechanism is to use an 8-13 μm atmospheric infrared transparent window to directionally release heat from the surface of an object to a deep-space cold source in the form of infrared radiation, thereby achieving continuous cooling of the device itself. The entire process requires no external energy input and has important application value in fields such as building refrigeration, condensate collection, and thermal management devices.

[0003] However, radiative cooling exhibits significant diurnal asymmetry. During the day, under the combined effects of solar radiation and high ambient temperatures, the cooling capacity of radiative cooling materials decreases significantly, and they may even absorb heat and rise in temperature. At night, when there is no solar radiation, the cooling power increases significantly, easily leading to overcooling where the cooling capacity exceeds actual demand. The cooling demand patterns in typical cooling scenarios such as buildings do not match the diurnal characteristics of radiative cooling. Therefore, to achieve efficient utilization of radiative cooling energy, a supporting cold energy storage and regulation scheme is necessary.

[0004] Solid-liquid phase change materials (PCMs) can absorb or release a large amount of latent heat of phase change during melting and solidification, and the temperature of the phase change process is approximately constant, making them an ideal medium for high-density storage of cold energy. The conventional utilization method is as follows: at night, the surplus cold energy from radiative cooling is used to solidify the PCM for cold storage; during the day, when radiative cooling capacity is insufficient, the PCM melts to release cold energy, thereby smoothing out diurnal cooling fluctuations and achieving a match between cold energy supply and demand.

[0005] Existing technologies mostly employ a two-layer structure with a radiative cooling layer and a phase change energy storage layer directly bonded together. While this allows for rapid transfer of cooling capacity, it still has certain limitations: Firstly, during the day, the temperature of the radiative cooling surface may be higher than the temperature of the phase change material, and heat will be transferred to the storage unit through the interface, resulting in the loss of stored cooling capacity. Secondly, even after the phase change material has completely solidified at night, the radiative cooling and storage process may continue, easily leading to overcooling of the system. Therefore, in traditional direct-contact structures, the interface contact state is fixed, making it difficult to adjust the interface thermal resistance according to different operating conditions, thus hindering the controllable storage and efficient utilization of cooling capacity. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a radiation refrigeration and cold storage device based on phase change volume change self-regulation that can solve the above problems. It can utilize the volume change of the phase change material during the phase change process to adaptively adjust the interfacial contact thermal resistance, thereby regulating the transfer of cold energy and realizing the storage and release of cold energy according to day and night operating conditions, thus improving the efficiency of cold energy utilization.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A radiative cooling and cold storage device based on phase change volume change self-regulation includes a radiative cooling plate, a phase change cold storage unit, and an insulation layer. The phase change cold storage unit is located inside the insulation layer and below the radiative cooling plate. The phase change cold storage unit includes a sealed cavity and a phase change material filled in the sealed cavity. As the volume of the phase change material changes, the height of the sealed cavity can adaptively adjust, thereby changing the contact state between the upper surface of the sealed cavity facing the radiative cooling plate and the radiative cooling plate.

[0008] Optionally, the sealing cavity includes an upper surface, a lower surface opposite to the upper surface, and a side surface connecting the upper surface and the lower surface; the upper surface and the lower surface are rigid metal surfaces, and the side surface is a stretchable corrugated surface.

[0009] Optionally, the upper and lower surfaces of the sealing cavity are smooth, high thermal conductivity metal surfaces with a thermal conductivity ≥15W / (m·K); the corrugated surface of the side can cause the sealing cavity to change in height by 0.1-0.5 mm as the volume of the phase change material changes.

[0010] Optionally, the metal plates on the upper and lower surfaces of the sealed cavity are made of aluminum alloy or stainless steel; the corrugated surface of the side is a metal bellows, a flexible polymer corrugated structure, or a rubber corrugated structure. The flexible polymer corrugated structure can be a corrugated structure made of TPU film, polyurethane film, or other flexible polymer materials.

[0011] Optionally, the sealed cavity is provided with a thermally enhanced structure.

[0012] Optionally, when the phase change material absorbs heat and melts and expands, it increases the contact between the upper surface of the sealed cavity and the radiative cooling plate, thereby reducing the contact thermal resistance and enhancing the transfer of cold energy; when the phase change material cools down, solidifies and shrinks, the contact between the upper surface of the sealed cavity and the radiative cooling plate decreases and the contact thermal resistance increases, thereby reducing the transfer of cold energy and the reverse transfer of heat.

[0013] Optionally, the radiative cooling plate includes a substrate and a radiative cooling material layer coated on the substrate; the radiative cooling material layer is a commercial coating in which inorganic dielectric particles are dispersed in a polymer, and its visible and near-infrared reflectivity is ≥0.9, and its emissivity in the 8-13 μm infrared atmospheric window is ≥0.9; the substrate is a high thermal conductivity metal with a thermal conductivity ≥30W / (m·K).

[0014] Optionally, the phase change material is a straight-chain alkane with a phase change temperature of 20-30°C. C, latent heat of phase change ≥180 J / g, volume shrinkage during solidification 3%-10%.

[0015] Optionally, the insulation layer includes an insulation layer body and a light-transmitting protective layer; the insulation layer body is a hollow body with an opening at one end, and the light-transmitting protective layer seals the opening of the insulation layer body; the insulation layer body and the light-transmitting protective layer together form a receiving space, in which the radiative cooling plate and the phase change cold storage unit are both placed, and the radiative cooling plate is located between the light-transmitting protective layer and the phase change cold storage unit; the light-transmitting protective layer is a low-density polyethylene film, used to reduce convection and conductive heat transfer between the radiative cooling plate and the environment.

[0016] Optionally, the insulation layer body includes an inner layer and an outer layer; the inner layer is a rigid metal layer used to fix the radiant cooling plate; the outer layer is the insulation body with a thermal conductivity ≤0.03 W / (m·K).

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: 1. The radiative cooling and cold storage device based on phase change volume change self-regulation provided by the present invention can adjust the radiative cooling capacity under different operating conditions by adaptively regulating the interface contact thermal resistance through phase change volume change, thereby improving the day-night mismatch problem of radiative cooling and improving the efficiency of cold capacity utilization. The present invention can realize the adaptive storage and release of cold capacity without external control, and has the advantages of simple structure, reliable operation and zero energy consumption, and is suitable for scenarios such as passive cooling of buildings.

[0018] 2. In this invention, the corrugated structure on the side of the sealed cavity can adaptively expand and contract with the volume change of the phase change material to adjust the cavity height: when the phase change material absorbs heat and melts, the degree of interfacial contact increases and the contact thermal resistance decreases, thereby enhancing the transfer of cold energy; when the phase change material cools down and solidifies, the degree of interfacial contact decreases and the contact thermal resistance increases, thereby reducing the transfer of cold energy and the reverse transfer of heat. Attached Figure Description

[0019] Figure 1 A schematic diagram of a radiation refrigeration and cold storage device based on phase change volume change self-regulation according to an embodiment of the present invention is shown, wherein the phase change material is in a solidified state and its volume shrinks.

[0020] Figure 2 A schematic diagram of a radiation refrigeration and cold storage device based on phase change volume change self-regulation according to an embodiment of the present invention is shown, wherein the phase change material is in a molten state and its volume expands.

[0021] Explanation of reference numerals in the attached diagram: 1-Radiative cooling plate; 2-Phase change cold storage unit; 3-Insulation layer; 4-Light-transmitting protective layer. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] like Figure 1 As shown, the radiative cooling and cold storage device based on phase change volume change self-regulation provided by the embodiments of the present invention includes a radiative cooling plate 1, a phase change cold storage unit 2, and an insulation layer 3. The phase change cold storage unit 2 is located inside the insulation layer 3 and below the radiative cooling plate 1.

[0025] The radiative cooling plate 1 includes a substrate and a radiative cooling material layer coated on the substrate. Preferably, the substrate is made of a high thermal conductivity metal with a thermal conductivity ≥30 W / (m·K), and can be copper foil or aluminum alloy sheet. The radiative cooling material is a commercially available coating of inorganic dielectric particles dispersed in a polymer, possessing high solar reflectivity (visible and near-infrared reflectivity ≥0.9) and high emissivity (emissivity ≥0.9) in an 8-13 μm infrared atmospheric window. More preferably, the thickness of the radiative cooling material layer is 200-500 μm.

[0026] The phase change energy storage unit 2 includes a sealed cavity and a phase change material filled within the sealed cavity. As the volume of the phase change material changes, the contact state between the upper surface of the sealed cavity facing the radiative cooling plate 1 and the radiative cooling plate 1 changes. Preferably, the phase change material is a straight-chain alkane with a phase change temperature of 20-30°C. C, latent heat of phase change ≥180 J / g, volume shrinkage during solidification 3%-10%. The sealing cavity includes an upper surface, a lower surface opposite to the upper surface, and a side surface connecting the upper and lower surfaces. The upper and lower surfaces of the sealing cavity are smooth, high thermal conductivity metal plates with a thermal conductivity ≥15 W / (m·K), which can be made of aluminum alloy or stainless steel. The side surface is a stretchable corrugated surface, which can be made of metal corrugated pipe, flexible polymer corrugated structure, or rubber corrugated structure. Preferably, the corrugated surface can cause a height change of 0.1-0.5 mm in the sealing cavity with the volume change of the phase change material to ensure the sealing performance during structural deformation. Optionally, the corrugation height of the corrugated surface is 1-3 mm, and the corrugation spacing is 5-10 mm.

[0027] The contact state between the upper surface of the sealed cavity and the radiative cooling plate 1 can be adjusted according to the volume change of the phase change material. Specifically, when the phase change material absorbs heat and melts and expands, the contact degree between the upper surface of the sealed cavity and the radiative cooling plate 1 increases, thereby reducing the contact thermal resistance and enhancing the transfer of cold energy; when the phase change material cools down, solidifies, and shrinks, the contact degree between the upper surface of the sealed cavity and the radiative cooling plate 1 decreases, the contact thermal resistance increases, thereby reducing the transfer of cold energy and the reverse transfer of heat. In addition, a thermally conductive enhancement structure is provided inside the sealed cavity. Preferably, the thermally conductive enhancement structure is a metal mesh, metal fiber, or graphite material, with a volume fraction of 5%-15%, used to improve the thermal conductivity efficiency of the phase change material.

[0028] The insulation layer 3 includes an insulation layer body and a light-transmitting protective layer 4. The insulation layer body is generally a hollow body with an opening at one end. The light-transmitting protective layer 4 seals the opening of the insulation layer body. Preferably, the insulation layer body and the light-transmitting protective layer 4 enclose a receiving space, in which the radiant cooling plate 1 and the phase change cold storage unit 2 are both placed, with the radiant cooling plate 1 located between the light-transmitting protective layer 4 and the phase change cold storage unit 2. The insulation layer body includes an inner layer and an outer layer. The inner layer is a rigid metal layer used to fix and support the radiant cooling plate, and the outer layer is the insulation body with a thermal conductivity ≤0.03 W / (m·K). Preferably, the light-transmitting protective layer 4 is a light-transmitting film, which can be selected as a low-density polyethylene film, used to reduce convection and conductive heat transfer between the radiant cooling plate and the external environment.

[0029] This invention adaptively regulates the interfacial contact thermal resistance through phase change volume change, enabling adaptive storage and release of cooling capacity under day and night conditions without external control. This improves the problems of easy cooling capacity loss and overcooling in traditional structures, achieving "peak shaving and valley filling" of cooling capacity. It has the advantages of simple structure, reliable operation, and zero-energy self-adaptation, and is suitable for scenarios such as passive cooling in buildings.

[0030] Example 1 The radiative cooling and cold storage device based on phase change volume change self-regulation provided in this embodiment is adapted to passive cooling scenarios in buildings. It includes a radiative cooling plate 1, a phase change cold storage unit 2, and an insulation layer 3. The designs of the radiative cooling plate 1, the phase change cold storage unit 2, and the insulation layer 3 are described below.

[0031] The radiative cooling plate 1 includes a substrate and a layer of radiative cooling material coated on the substrate. The substrate is made of aluminum alloy sheet with a thermal conductivity of 160 W / (m²). K); The surface is coated with a radiation cooling material layer, preferably a commercially available coating, in which inorganic dielectric particles are dispersed in a polymer, the coating thickness is 500 μm, the reflectivity of visible and near-infrared light is 0.92, the emissivity of the 8-13 μm band is 0.9, and it can generate stable cooling at night.

[0032] Phase change energy storage unit 2 includes a sealed cavity and a phase change material filled within the sealed cavity. The phase change material is n-octadecane, with a phase change temperature of 28°C. C, latent heat of phase change 244 J / g, volume shrinkage during solidification 10%, fills the interior of a sealed cavity; the upper and lower surfaces of the sealed cavity are made of stainless steel with a thermal conductivity of 16 W / (m²). K), the side is a flexible polyurethane corrugated structure, which can produce a height change of 0.3 mm in the sealing cavity as the volume of the phase change material changes, thereby ensuring the sealing performance during the structural deformation process; the sealing cavity is equipped with a metal mesh thermal conductivity enhancement structure (volume fraction of about 5%) to improve the efficiency of cold energy transfer.

[0033] The insulation layer 3 comprises an insulation layer body and a light-transmitting protective layer 4. The inner layer of the insulation layer body is made of rigid stainless steel and is used to fix the radiant cooling plate 1; the outer layer is the main insulation component with a thermal conductivity of 0.027 W / (m²). K); The top is provided with a light-transmitting protective layer 4, which is a low-density polyethylene film (94% light transmittance) to reduce convection and heat transfer between the radiant cooling plate and the external environment.

[0034] Work process: At the start of the night, the phase change material in the phase change storage unit 2 is in a molten state. The upper surface of the sealed cavity has a high degree of contact with the radiative cooling plate 1, and the interfacial contact thermal resistance is small. The cold energy generated by the radiative cooling plate 1 can be transferred to the phase change material more efficiently to achieve cold storage. As the phase change material gradually solidifies and shrinks, the corrugated structure of the sealed cavity deforms, the degree of contact between the upper surface and the radiative cooling plate 1 decreases, the contact thermal resistance increases, and the cold energy transfer efficiency decreases accordingly. When the phase change material is basically solidified, the degree of interfacial contact is low, which can reduce the further transfer of excess cold energy, thereby mitigating the supercooling phenomenon.

[0035] At the beginning of the day, the phase change material is in a solid contraction state, and the contact between the upper surface of the sealed cavity and the radiative cooling plate 1 is low, resulting in a large interfacial thermal resistance, which reduces the transfer of external heat to the cold storage unit. As the ambient temperature rises during the day, the phase change material gradually absorbs heat, melts, and expands, causing the sealed cavity to deform and gradually increasing the contact between it and the radiative cooling plate 1, thus providing favorable conditions for the next nighttime cold storage process.

[0036] Example 2 The radiative cooling and cold storage device based on phase change volume change self-regulation provided in this embodiment is suitable for small building cooling. The design of the radiative cooling plate 1, the phase change cold storage unit 2, and the insulation layer 3 are described below.

[0037] The radiative cooling plate 1 includes a substrate and a radiative cooling material layer coated on the substrate. The substrate is a copper foil with a thermal conductivity of 380 W / (m·K); the surface is coated with a radiative cooling material layer with a thickness of 300 μm. This coating is a commercially available inorganic dielectric particle dispersion coating with a visible and near-infrared light reflectance of 0.9 and an emissivity of 0.91 in the 8-13 μm band, and can stably generate cooling at night.

[0038] The phase change energy storage unit 2 includes a sealed cavity and a phase change material filled in the sealed cavity. The phase change material is n-heptadecane, which has a phase change temperature of 22 ℃, a latent heat of phase change of 220 J / g, and a volume shrinkage rate of 10% upon solidification. It is filled in the sealed cavity. The upper and lower surfaces of the sealed cavity are made of aluminum alloy, which is smooth and has high thermal conductivity, with a thermal conductivity of 124 W / (m·K). The sides have a flexible polymer corrugated structure, which can cause a height change of about 0.5 mm in the sealed cavity as the volume of the phase change material changes, so as to adapt to the volume change of the phase change material and ensure the structural sealing performance.

[0039] The insulation layer 3 includes an insulation layer body and a light-transmitting protective layer 4. The inner layer of the insulation layer body is a rigid metal layer used to fix the radiant cooling plate 1; the outer layer is the insulation body with a thermal conductivity of 0.025 W / (m·K), and the top is provided with a light-transmitting protective layer 4, which is a low-density polyethylene film (94% light transmittance) used to reduce convection and heat transfer between the radiant cooling plate and the external environment, thereby reducing cooling loss.

[0040] The working process is the same as in Example 1, and will not be repeated here.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A radiative cooling and cold storage device based on phase change volume change self-regulation, comprising a radiative cooling plate, a phase change cold storage unit, and an insulation layer, wherein the phase change cold storage unit is located inside the insulation layer and below the radiative cooling plate; characterized in that, The phase change cold storage unit includes a sealed cavity and a phase change material filled in the sealed cavity; As the volume of the phase change material changes, the sealing cavity can adaptively adjust its height, causing the upper surface of the sealing cavity facing the radiative cooling plate to shift under the influence of the phase change material's volume change, thereby altering its contact state with the radiative cooling plate.

2. The radiation refrigeration and cold storage device based on phase change volume change self-regulation according to claim 1, characterized in that, The sealed cavity includes an upper surface, a lower surface opposite to the upper surface, and a side surface connecting the upper surface and the lower surface; the upper surface and the lower surface are rigid metal surfaces, and the side surface is a stretchable corrugated surface.

3. The radiation refrigeration and cold storage device based on phase change volume change self-regulation according to claim 2, characterized in that, The upper and lower surfaces of the sealed cavity are smooth, highly thermally conductive metal surfaces with a thermal conductivity ≥15 W / (m·K); the corrugated surface of the side can produce a height change of 0.1-0.5 mm with the volume change of the phase change material.

4. The radiation refrigeration and cold storage device based on phase change volume change self-regulation according to claim 3, characterized in that, The upper and lower surfaces of the sealed cavity are made of aluminum alloy or stainless steel; the corrugated surface of the side is a metal bellows, a flexible polymer corrugated structure, or a rubber corrugated structure.

5. The radiation refrigeration and cold storage device based on phase change volume change self-regulation according to claim 2, characterized in that, The sealed cavity is equipped with a thermally enhanced structure.

6. The radiation refrigeration and cold storage device based on phase change volume change self-regulation according to any one of claims 1 to 5, characterized in that, When the phase change material absorbs heat and melts and expands, it increases the contact between the upper surface of the sealed cavity and the radiative cooling plate, reduces the contact thermal resistance, and enhances the transfer of cold energy. When the phase change material cools down, solidifies, and shrinks, the contact between the upper surface of the sealed cavity and the radiative cooling plate decreases, the contact thermal resistance increases, thereby reducing the transfer of cold energy and the reverse transfer of heat.

7. The radiation refrigeration and cold storage device based on phase change volume change self-regulation according to any one of claims 1 to 5, characterized in that, The radiation cooling plate includes a substrate and a radiation cooling material layer coated on the substrate; the radiation cooling material layer is a commercial coating in which inorganic dielectric particles are dispersed in a polymer, and its visible and near-infrared reflectivity is ≥0.9, and its emissivity in the 8-13 μm infrared atmospheric window is ≥0.9; the substrate is a high thermal conductivity metal with a thermal conductivity ≥30W / (m·K).

8. The radiation refrigeration and cold storage device based on phase change volume change self-regulation according to any one of claims 1 to 5, characterized in that, The phase change material is a straight-chain alkane, with a phase change temperature of 20-30°C. C, latent heat of phase change ≥180 J / g, volume shrinkage during solidification 3%-10%.

9. The radiation refrigeration and cold storage device based on phase change volume change self-regulation according to any one of claims 1 to 5, characterized in that, The insulation layer includes an insulation layer body and a light-transmitting protective layer; the insulation layer body is a hollow body with an opening at one end, and the light-transmitting protective layer seals the opening of the insulation layer body; the insulation layer body and the light-transmitting protective layer together form a receiving space, in which the radiative cooling plate and the phase change cold storage unit are both placed, and the radiative cooling plate is located between the light-transmitting protective layer and the phase change cold storage unit; the light-transmitting protective layer is a low-density polyethylene film, used to reduce convection and conductive heat transfer between the radiative cooling plate and the environment.

10. The radiation refrigeration and cold storage device based on phase change volume change self-regulation according to claim 9, characterized in that, The insulation layer body includes an inner layer and an outer layer; the inner layer is a rigid metal layer used to fix the radiant cooling plate; the outer layer is the insulation body with a thermal conductivity ≤0.03 W / (m·K).

Images