Composite heat dissipation low-voltage switch cabinet based on radiation refrigeration

Abstract

This application relates to the field of heat dissipation technology for low-voltage power equipment in the power transmission and distribution sector, specifically to a composite heat dissipation low-voltage switchgear based on radiative cooling. It includes a main body, an outer casing radiative cooling system, a busbar radiative cooling system, a natural convection ventilation system, and an auxiliary monitoring module. Both the outer casing and busbar radiative cooling systems include a radiative cooling layer. The main body exchanges heat with the external environment or internal space through this radiative cooling layer. This application achieves a composite synergistic heat dissipation effect, requiring no additional energy consumption and simultaneously addressing internal heat generation and external solar radiation.

Description

Technical Field

[0001] This application relates to the field of heat dissipation technology for low-voltage power equipment in the power transmission and distribution sector, specifically to a composite heat dissipation low-voltage switchgear based on radiation cooling. Background Technology

[0002] Low-voltage switchgear, as a core node device in the power distribution network, undertakes important functions such as power distribution, control, and protection. Its operational stability directly affects the reliability of power supply. During actual operation, the core conductive components inside the switchgear, such as busbars and circuit breaker contacts, generate significant Joule heating due to carrying large currents. Simultaneously, outdoor-installed switchgear is exposed to intense solar radiation for extended periods, causing the metal casing to absorb large amounts of solar heat, resulting in a "greenhouse effect" inside the cabinet. This combined effect of internal heat sources and external heat loads can easily lead to a continuous rise in the cabinet temperature, accelerating the aging of insulation materials, increasing contact resistance, and in severe cases, even causing short circuits, fires, and other safety accidents.

[0003] Currently, heat dissipation in low-voltage switchgear mainly relies on natural ventilation, forced air cooling, or the installation of industrial air conditioning. Natural ventilation depends on various louver structures, resulting in low heat dissipation efficiency and being highly susceptible to ambient temperature, essentially failing when the outside temperature is high. While forced air cooling improves heat dissipation efficiency, fans are active devices, leading to high energy consumption and a high rate of mechanical failure. Furthermore, frequent air exchange can bring external dust and moisture into the cabinet, clogging dust filters and potentially accumulating on the surface of insulating components, inducing creepage and flashover. While air conditioning provides significant cooling, it is costly and bulky, contradicting the trend of energy conservation and emission reduction. In addition, regarding enclosure protection, most existing switchgear enclosures use traditional powder coating processes, primarily focusing on corrosion resistance. They lack the ability to actively manage the solar spectrum, failing to effectively block the intake of solar heat and unable to utilize atmospheric windows for passive heat dissipation.

[0004] Therefore, it is particularly important to develop a composite synergistic heat dissipation system that requires no additional energy consumption and can simultaneously cope with internal heat generation and external solar radiation. Summary of the Invention

[0005] This application provides a composite heat dissipation low-voltage switchgear based on radiation cooling, which has the effect of synergistic heat dissipation that can simultaneously cope with internal heat generation and external solar radiation without additional energy consumption.

[0006] The low-voltage switchgear based on radiative cooling provided in this application adopts the following technical solution:

[0007] A composite heat dissipation low-voltage switchgear based on radiation cooling is characterized in that it includes a device body, an outer shell radiation cooling system, a busbar radiation cooling system, a natural convection ventilation system, and an auxiliary monitoring module. The outer shell radiation cooling system and the busbar radiation cooling system both include a radiation cooling layer. The device body exchanges heat with the external environment or internal space through the radiation cooling layer.

[0008] By adopting the above technical solution, an active radiative heat dissipation channel with "internal conduction and external exhaust" is constructed by introducing radiative cooling layers at both the outer shell and the busbar. The outer shell radiative cooling system can efficiently reflect solar radiation and dissipate the accumulated heat to the outer space in the form of infrared radiation through the "atmospheric window," blocking external heat load and dissipating heat from the source. The busbar radiative cooling system directly acts on the core heat source, rapidly radiating the heat from the busbar to the cabinet space or having it absorbed by the outer shell and then discharged. Together with the natural convection ventilation system and auxiliary monitoring module, the two systems can reduce the greenhouse effect caused by heat absorption by the metal shell and the temperature rise caused by high-load operation of internal components, achieving low-energy consumption, all-weather, and highly efficient composite heat dissipation management. This solves the technical problem of low efficiency in traditional low-voltage switchgear that relies solely on convection heat dissipation.

[0009] Optionally, the radiative cooling and heat dissipation of the outer casing, from the outside to the inside, includes:

[0010] (1) Self-cleaning layer: The self-cleaning layer is a superhydrophobic or photocatalytic self-cleaning coating, the material of which includes silica sol-gel and titanium dioxide photocatalytic material, with a thickness of 10-30μm;

[0011] (2) Radiation cooling layer: The radiation cooling layer has a solar reflectivity ≥95% and an average emissivity ≥95% in the 8-13μm band, and adopts one of the following: radiation cooling coating, radiation cooling film and integrated radiation cooling metal plate;

[0012] (21) If it is a radiation cooling coating, the thickness is 50-200 μm;

[0013] (22) If it is a radiation-cooling film with a thickness of 100-500μm, it is bonded with an adhesive;

[0014] (23) If it is an integrated radiation cooling metal plate, the radiation cooling structure is directly formed on the surface of the metal plate by anodizing or microstructure etching;

[0015] (3) Substrate layer: The substrate layer is the main body of the shell structure, and the material includes 1.0-2.0mm thick galvanized steel plate, aluminum alloy plate and SMC composite material;

[0016] (4) Insulation layer: The insulation layer is made of low thermal conductivity material with a thermal conductivity of ≤0.05 W / (m·K) and a thickness of 3-10mm.

[0017] By adopting the above technical solutions, the outermost superhydrophobic or photocatalytic self-cleaning layer can effectively prevent dust accumulation and ensure that the lower radiative cooling layer maintains a high solar reflectivity of ≥95% for a long time, thus maintaining efficient optical performance. The core function of the radiative cooling layer (coating, film or metal plate) focuses on radiating heat outwards. The innermost thermal insulation layer with a thermal conductivity of ≤0.05 W / (m·K) plays a key role in thermal barrier. It can not only further block the conduction of residual solar heat absorbed by the outer shell into the cabinet, but also reduce the heat intrusion of the external high temperature environment into the cabinet. This structural synergy of "external reflection radiation and internal blocking conduction" greatly improves the thermal protection and heat dissipation capabilities of the outer shell.

[0018] Optionally, the busbar radiant cooling and heat dissipation system comprises, from the inside out:

[0019] (1) Busbar body: The busbar body is made of copper;

[0020] (2) Insulating and thermally conductive layer: The insulating and thermally conductive layer is made of ceramic fiber composite material and polyimide thermally conductive film. The insulating and thermally conductive layer is required to have a thermal conductivity ≥0.5 W / (m·K), a breakdown voltage ≥10kV, and a thickness of 20-50μm.

[0021] (3) Interface transition layer: The interface transition layer is made of silane coupling agent and has a thickness of 5-10 μm;

[0022] (4) Radiation cooling layer: The thickness of the busbar radiation cooling layer is 50-200μm, and it adopts one of the following: radiation cooling coating, radiation cooling film and integrated radiation cooling metal plate.

[0023] By adopting the above technical solutions, the insulating and thermally conductive layer provides electrical safety protection with a breakdown voltage of ≥10kV, while using highly thermally conductive materials to quickly dissipate heat from the copper busbar; the silane coupling agent component of the interface transition layer effectively solves the problem of poor interfacial bonding between the organic coating and the metal substrate, preventing coating peeling under thermal cycling; the outermost busbar radiative cooling layer breaks through the limitation of traditional busbars relying solely on convection heat transfer, and can actively dissipate heat in the form of infrared radiation, thereby reducing the operating temperature of the busbar, delaying insulation aging, and improving the current carrying capacity and safety of the equipment.

[0024] Optionally, the natural convection ventilation system includes an air inlet located at the bottom of the housing and an air outlet located at the top of the housing, both of which are equipped with dust filters with a filter opening of ≤5μm.

[0025] By adopting the above technical solution, while utilizing the natural convection airflow formed by the chimney effect to remove heat from the cabinet, the high-precision dust filter can effectively intercept fine particles from entering the equipment, preventing dust accumulation on the busbar or insulation surface from reducing heat dissipation capacity or creepage flashover risk, thereby maintaining the cleanliness and electrical insulation performance of the equipment while ensuring heat dissipation and ventilation efficiency.

[0026] Optionally, the auxiliary monitoring module includes a temperature sensor, a controller, and a low-power temperature-controlled fan. The temperature sensor is located in the hot spot area inside the equipment. The controller is electrically connected to the temperature sensor and can monitor the internal temperature of the equipment in real time and provide feedback data. The low-power temperature-controlled fan is automatically started and stopped by the controller based on the temperature data.

[0027] By adopting the above technical solution, an active auxiliary heat dissipation mechanism that responds on demand has been constructed. Under extreme high temperature or high load conditions, forced convection can quickly reduce the peak heat accumulation and fill the trough period of passive radiation heat dissipation. Under normal operating conditions, it stops to save energy, thus achieving a balance between energy saving and efficient temperature control.

[0028] Optionally, the radiation cooling layer comprises the following raw materials in parts by weight: 30-60 parts film-forming resin, 30-45 parts high-reflectivity filler, 10-20 parts infrared radiation filler, 5-15 parts heat insulation and reinforcing filler, 1-5 parts additives, 5-15 parts solvent, 10-20 parts aerogel-supported phase change microcapsule composite particles, and 1-2 parts interface modifier.

[0029] Optionally, the film-forming resin includes at least one of polyvinylidene fluoride, polyvinylidene fluoride, or polytetrafluoroethylene;

[0030] The high-reflectivity filler includes at least one of titanium dioxide, zinc oxide, and barium sulfate;

[0031] The infrared radiation filler includes at least one of silicon carbide, aluminum nitride, and boron nitride;

[0032] The heat insulation and reinforcing filler is air glass microspheres with a particle size of 10-50μm;

[0033] The additives include at least one of dispersants, leveling agents, and UV stabilizers;

[0034] The solvent includes at least one of acetone, ethyl acetate, or butanone.

[0035] Optionally, the aerogel-supported phase change microcapsule composite particles comprise the following raw materials in parts by weight: 30-40 parts of n-octadecane, 10-15 parts of melamine, 20-30 parts of formaldehyde solution, 2-5 parts of modified boron nitride nanosheets, 15-25 parts of hydrophobic silica aerogel powder, and 1-3 parts of silane coupling agent KH-560.

[0036] By adopting the above technical solutions, high-reflectivity fillers and infrared radiation fillers provide a basic radiative cooling channel. The key lies in the introduction of aerogel-supported phase change microcapsule composite particles. The octacosane phase change core material inside these particles can absorb heat and melt when the temperature rises, providing latent heat storage capacity to mitigate temperature shocks. Meanwhile, the externally supported hydrophobic silica aerogel has ultra-low thermal conductivity and can construct countless micro-nano thermal insulation units within the coating, blocking the conduction of ambient heat to the substrate. The addition of modified boron nitride nanosheets compensates for the poor thermal conductivity of the phase change material and improves the heat absorption response speed. This composite material system, which integrates "reflection, radiation, phase change heat storage, and aerogel insulation," endows the coating with excellent thermal regulation capabilities and passive cooling effects.

[0037] Optionally, the preparation method of the aerogel-supported phase change microcapsule composite particles includes the following steps:

[0038] S1: Mix melamine with 35-40wt% formaldehyde aqueous solution, adjust the pH to 8.5-9.0 with triethanolamine, and heat and stir in a water bath at 65-75℃ for 30-60 minutes to obtain a prepolymer solution;

[0039] S2: Modified boron nitride nanosheets are ultrasonically dispersed in deionized water, heated to 65-75℃, molten n-octacosan, and sheared at high speed at 8000-10000 rpm for 15-30 min to obtain an emulsion.

[0040] S3: Adjust the pH of the emulsion to 3.5-4.5 with citric acid, add the prepolymer solution from step S1 dropwise to the emulsion within 30-45 min, stir and react at 75-80℃ for 2-3 h to solidify into a shell, filter, wash and vacuum dry at 55-60℃ for 10-12 h to obtain phase change microcapsules.

[0041] S4: The dried phase change microcapsules and aerogel powder were dispersed in anhydrous ethanol and mixed and adsorbed at a low speed of 300-500 rpm at 25-30℃ for 2-3 hours; then silane coupling agent KH-560 was added, and the temperature was raised to 65-70℃ and refluxed for 3-4 hours; after the reaction was completed, the mixture was filtered and vacuum dried at 65-75℃ for 10-12 hours to obtain aerogel-supported phase change microcapsule composite particles.

[0042] By adopting the above technical solution, in steps S1-S3, pH value adjustment and high-speed shearing process are used to tightly encapsulate boron nitride-modified n-octacosane with melamine-formaldehyde resin, forming phase change microcapsules with complete core-shell structure, uniform particle size and fast thermal response. In step S4, a low-speed mixing and adsorption process is used to embed the microcapsules into the aerogel network without damaging the aerogel pore structure, and a strong chemical bond between the two is achieved by using silane coupling agent KH-560 in the reflux reaction. This method effectively solves the problems of difficult dispersion of aerogel and easy leakage of phase change microcapsules, and successfully prepares composite functional particles with both high heat storage density and low thermal conductivity.

[0043] Optionally, the method for preparing the radiation cooling layer includes the following steps:

[0044] S1 (Preparation of matrix slurry): Mix film-forming resin, high reflectivity filler, infrared radiation filler, heat insulation and reinforcing filler, additives and solvent, keep the temperature between 20-30℃, and perform sand milling at 2000-2500rpm for 1-2 hours to obtain matrix slurry.

[0045] S2 (Preparation of coating slurry): Add hydrophobic silica aerogel powder and silane coupling agent KH-560 to the matrix slurry, control the system temperature to not exceed 35℃, and disperse at a low shear speed of 600-800rpm for 30-45min to obtain radiation cooling coating slurry.

[0046] S3 (Coating and Segmented Curing): The slurry obtained from S1 and S2 is applied to the surface of the substrate, and then cured using a segmented curing process to form a radiation cooling layer;

[0047] The segmented curing process includes: a first stage of leveling by standing at room temperature of 20-25℃ for 15-20 minutes; a second stage of pre-curing by heating to 80-90℃ for 20-30 minutes; and a third stage of final curing by heating to 150-160℃ for 45-60 minutes.

[0048] By adopting the above technical solution, step S1 first ensures the nanoscale dispersion of the base filler in the film-forming resin through high-speed sand milling, thus guaranteeing the density of the coating; step S2 strictly controls the temperature to not exceed 35℃ and adds aerogel and phase change microcapsules at low shear speed, effectively avoiding mechanical shear force from damaging the brittle aerogel skeleton and microcapsule shell, and preserving the complete functionality of the particles; the segmented curing process in step S3, through room temperature leveling, low temperature pre-curing and high temperature final curing, prevents pinholes and microcracks caused by excessive solvent evaporation, ensuring that the film surface has a high degree of optical smoothness, thereby maximizing the solar reflectivity and infrared emissivity of the coating and obtaining the best radiative cooling performance.

[0049] In summary, this application includes at least one of the following beneficial technical effects:

[0050] 1. An active thermal management mechanism of "external heat rejection + internal heat dissipation" is constructed through the synergy of the dual radiative cooling system of the outer shell and busbar. Unlike the traditional passive heat dissipation method that relies solely on natural ventilation or forced convection by fans, the outer shell radiative cooling layer utilizes the high solar reflectivity and high emissivity of the wavelength band to reflect solar radiation energy and dissipate heat outward through the "atmospheric window". Combined with the low thermal conductivity insulation layer set on the inner side, a thermal barrier is formed, effectively blocking the conduction of external environmental heat into the cabinet. At the same time, the busbar radiative cooling layer breaks through the limitation of traditional conductive components relying solely on surface convection heat exchange. It uses a high thermal conductivity insulation layer to quickly conduct Joule heat generated by the copper busbar and actively dissipate it into the cabinet space in the form of infrared radiation. The interaction between the two reduces the temperature rise of the switchgear caused by the "greenhouse effect" and high internal load operation, thereby improving the safety and lifespan of the equipment.

[0051] 2. By introducing self-made aerogel-supported phase change microcapsule composite particles into the radiative cooling layer, multifunctional coupling of the coating at the microscopic level is achieved. The composite particles use n-octacosane as the phase change core material, which undergoes a solid-liquid phase change to absorb latent heat when the ambient temperature or equipment temperature fluctuates, playing a "peak-shaving and valley-filling" thermal buffering role. The thermal response speed inside the microcapsules is improved by modifying boron nitride filler. More importantly, by utilizing the ultra-low thermal conductivity of the hydrophobic silica aerogel it encapsulates, a "micro-nano thermal insulation island" is constructed in the coating matrix, so that the coating integrates the functions of "reflection-radiation-phase change heat storage-aerogel thermal insulation", effectively solving the problem that traditional single-function radiative cooling coatings cannot cope with sudden high temperature shocks and insufficient thermal resistance. Detailed Implementation

[0052] Preparation Example A1

[0053] Aerogel-supported phase change microcapsule composite particles are prepared by the following steps:

[0054] S1: Melamine is mixed with 37wt% formaldehyde aqueous solution, the pH is adjusted to 8.5-9.0 with triethanolamine, and the mixture is heated and stirred in a water bath at 70℃ for 45 min to obtain a prepolymer solution;

[0055] S2: 3 parts by weight of modified boron nitride nanosheets were ultrasonically dispersed in deionized water, heated to 70°C, and 35 parts by weight of molten n-octadecane were added. The mixture was sheared at 9000 rpm for 20 min to obtain an emulsion.

[0056] S3: Adjust the pH of the emulsion to 4.0 with 10wt% citric acid, add the prepolymer solution from step S1 dropwise to the emulsion within 40 min, and stir at 75℃ for 2.5 h to solidify into a shell; filter, wash, and vacuum dry at 60℃ for 12 h to obtain phase change microcapsules.

[0057] S4: The dried phase change microcapsules and 20 parts by weight of hydrophobic silica aerogel powder were dispersed in anhydrous ethanol and mixed and adsorbed at a low speed of 400 rpm at 25 °C for 2.5 h; then silane coupling agent KH-560 was added, and the mixture was heated to 65 °C and refluxed for 3.5 h; after the reaction was completed, the mixture was filtered and vacuum dried at 70 °C for 12 h to obtain aerogel-supported phase change microcapsule composite particles.

[0058] Preparation Example A2

[0059] The aerogel-supported phase change microcapsule composite particles differ from those in Preparation Example 1 in that the amount of n-octacosane is 30 parts by weight, the amount of modified boron nitride is 2 parts, and the amount of aerogel powder is 15 parts.

[0060] Preparation Example A3

[0061] The aerogel-supported phase change microcapsule composite particles differ from those in Preparation Example 1 in that the amount of n-octacosane is 40 parts by weight, the amount of modified boron nitride is 5 parts, and the amount of aerogel powder is 25 parts.

[0062] Preparation Example A4

[0063] The aerogel-supported phase change microcapsule composite particles differ from those in Preparation Example 1 in that an equal amount of liquid paraffin oil is used instead of n-octacosane.

[0064] Preparation Example A5

[0065] The aerogel-supported phase change microcapsule composite particles differ from those in Preparation Example 1 in that an equal amount of talc powder is used instead of modified boron nitride.

[0066] Preparation Example A6

[0067] The aerogel-loaded phase change microcapsule composite particles differ from those in Preparation Example 1 in that an equal amount of solid silica microspheres are used instead of hydrophobic silica aerogel.

[0068] Preparation Example B1

[0069] The radiation cooling coating is composed of the following raw materials in parts by weight: 45 parts of film-forming resin (PVDF), 38 parts of high-reflectivity filler (TiO2), 15 parts of infrared radiation filler (SiC), 10 parts of heat-insulating and reinforcing filler (glass microspheres), 3 parts of additive (dispersant BYK-161), 10 parts of solvent (butanone), 15 parts of aerogel-supported phase change microcapsule composite particles obtained in preparation example A1, and 1.5 parts of interface modifier.

[0070] The preparation method of radiation-cooling coating includes the following steps:

[0071] S1 (Preparation of matrix slurry): Mix film-forming resin, high reflectivity filler, infrared radiation filler, heat insulation and reinforcing filler, additives and solvent, keep the temperature between 25°C and grind at 2200 rpm for 1-2 hours to obtain matrix slurry.

[0072] S2 (Preparation of coating slurry): The aerogel-supported phase change microcapsule composite particles and interface modifier obtained in Preparation Example 1 were added to the matrix slurry. The system temperature was controlled at 30°C, and the mixture was dispersed at a low shear speed of 700 rpm for 40 min to obtain the radiation cooling coating slurry.

[0073] Preparation Example B2

[0074] The radiation cooling coating differs from Preparation Example B1 in that it is composed of the following raw materials in parts by weight: 30 parts of film-forming resin (PVDF), 30 parts of high-reflectivity filler (TiO2), 10 parts of infrared radiation filler (SiC), 5 parts of heat-insulating and reinforcing filler (glass microspheres), 1 part of additive (dispersant BYK-161), 5 parts of solvent (butanone), and 15 parts of aerogel-supported phase change microcapsule composite particles and 1 part of interface modifier obtained in Preparation Example A2.

[0075] Preparation Example B3

[0076] The radiation cooling coating differs from Preparation Example B1 in that it is composed of the following raw materials in parts by weight: 60 parts of film-forming resin (PVDF), 45 parts of high-reflectivity filler (TiO2), 20 parts of infrared radiation filler (SiC), 15 parts of heat-insulating and reinforcing filler (glass microspheres), 5 parts of additive (dispersant BYK-161), 15 parts of solvent (butanone), and 20 parts of aerogel-supported phase change microcapsule composite particles and 2 parts of interface modifier obtained in Preparation Example A3.

[0077] Preparation Example B4

[0078] The radiation-cooling coating differs from Preparation Example B1 in that the aerogel-supported phase change microcapsule composite particles are specifically obtained using Preparation Example A4.

[0079] Preparation Example B5

[0080] The radiation-cooling coating differs from Preparation Example B1 in that the aerogel-supported phase change microcapsule composite particles are specifically obtained using Preparation Example A5.

[0081] Preparation Example B6

[0082] The radiation-cooling coating differs from Preparation Example B1 in that the aerogel-supported phase change microcapsule composite particles are specifically obtained using Preparation Example A6.

[0083] Preparation Example B7

[0084] The radiation cooling coating differs from Preparation Example B1 in that the aerogel-supported phase change microcapsule composite particles are replaced with an equal mass ratio of 1:1:1 of infrared radiation filler, high reflectance filler, and heat insulation enhancement filler mixture.

[0085] Example 1

[0086] This embodiment uses a new type of outdoor low-voltage distribution cabinet with a rated current of 630A as an example:

[0087] 1. Equipment Structure and Material Selection

[0088] (1) Equipment body: standard GGD type outdoor power distribution cabinet.

[0089] (2) Radiative cooling and heat dissipation system of the outer shell:

[0090] Substrate layer: 1.5mm thick galvanized steel sheet;

[0091] Radiation cooling layer: A spray coating process was used. The coating material, prepared as in Example B1, was ground, coated, and then cured by baking at 150°C for 20 minutes to form a coating approximately 120 μm thick.

[0092] Self-cleaning layer: A silica sol-gel superhydrophobic coating with a thickness of about 20 μm is sprayed onto the surface of the radiation cooling layer;

[0093] Thermal insulation layer: A 5mm thick aerogel felt (thermal conductivity 0.02 W / (m·K)) is pasted on the inside of the substrate layer.

[0094] (3) Busbar radiant cooling and heat dissipation system:

[0095] Busbar body: TMY-60×6 copper busbar;

[0096] Insulating and thermally conductive layer: A 50μm thick polyimide (PI) thermally conductive film (thermal conductivity 1.2 W / (m·K), breakdown voltage 12kV) is used to tightly wrap the copper busbar through a hot-pressing process;

[0097] Interface transition layer: KH-550 silane coupling agent is coated on the surface of the polyimide film and cured at room temperature for 12 hours;

[0098] Busbar radiant cooling layer: High-temperature resistant coating is applied, and the filler is removed to enhance the heat insulation. The curing is done in stages: first, pre-curing at 80℃ for 10 minutes, then final curing at 180℃ for 30 minutes, with a coating thickness of about 80μm.

[0099] (4) Natural convection ventilation system: The bottom of the cabinet is equipped with a strip louvered air inlet (with G4 grade dustproof filter), and the top is equipped with an umbrella-shaped rainproof air outlet (with the same filter), forming an effective convection channel.

[0100] (5) Auxiliary monitoring module: Install PT100 temperature sensors at the busbar connection and circuit breaker contacts, connect them to the temperature controller on the cabinet door, set the upper limit of 60℃ to link a 4W small axial fan.

[0101] Example 2

[0102] The difference between the new type of outdoor low-voltage distribution cabinet and Example 1 is that the busbar radiant cooling layer of the outer shell radiant cooling heat dissipation system specifically adopts the coating obtained in Preparation Example B2.

[0103] Example 3

[0104] The difference between the new type of outdoor low-voltage distribution cabinet and Example 1 is that the busbar radiant cooling layer of the outer shell radiant cooling heat dissipation system specifically adopts the coating obtained in Preparation Example B3.

[0105] Example 4

[0106] This embodiment is for a ring main unit of a substation on the Qinghai-Tibet Plateau, which is located at an altitude of 4,500 meters, with thin air, large temperature difference between day and night, and strong ultraviolet radiation.

[0107] (1) Radiative cooling and heat dissipation system of the outer shell:

[0108] Substrate layer: 2.0mm thick stainless steel plate;

[0109] Radiation cooling layer: An integrated radiation cooling metal plate is used, and the substrate is an aluminum alloy plate that has undergone anodizing and microstructure etching (multi-scale micro-nano structures are formed on the surface).

[0110] Insulation layer: specially thickened aerogel felt up to 10mm.

[0111] (2) Busbar radiant cooling and heat dissipation system: Same as in Example 1.

[0112] (3) Natural convection ventilation system: The ventilation opening area is increased by 30% in the design, and low resistance and high filtration precision filter media are used.

[0113] (4) Auxiliary monitoring and hybrid heat dissipation: Configure multi-point temperature monitoring and install a DC brushless fan that can intelligently adjust the speed according to the temperature gradient, and only start briefly in the afternoon on extremely hot days.

[0114] Comparative Example 1

[0115] The difference between the new type of outdoor low-voltage distribution cabinet and Example 1 is that the busbar radiant cooling layer of the outer shell radiant cooling heat dissipation system specifically adopts the coating obtained in Preparation Example B4.

[0116] Comparative Example 2

[0117] The difference between the new type of outdoor low-voltage distribution cabinet and Example 1 is that the busbar radiant cooling layer of the outer shell radiant cooling heat dissipation system specifically adopts the coating obtained in Preparation Example B5.

[0118] Comparative Example 3

[0119] The difference between the new type of outdoor low-voltage distribution cabinet and Example 1 is that the busbar radiant cooling layer of the outer shell radiant cooling heat dissipation system specifically adopts the coating obtained in Preparation Example B6.

[0120] Comparative Example 4

[0121] The difference between the new type of outdoor low-voltage distribution cabinet and Example 1 is that the busbar radiant cooling layer of the outer shell radiant cooling heat dissipation system specifically adopts the coating obtained in Preparation Example B7.

[0122] Detection example

[0123] Test environment setup: Place each group of switch cabinets in an artificial climate chamber;

[0124] Light source simulation: A solar simulator is set at the top, and the radiation intensity is set to 1000 W / m² (simulating strong midday sunlight).

[0125] Internal heat source: A rated current (e.g., 2000A) is applied to the busbar to generate Joule heat;

[0126] Ambient temperature: set to 35℃.

[0127] 1. Basic performance test of coating:

[0128] Solar reflectance: Tested according to ASTM E903-12 standard using a UV-Vis-NIR spectrophotometer with an integrating sphere (wavelength range 0.3-2.5μm).

[0129] Thermal emissivity: Tested using an infrared emissivity meter (8-13μm band) according to ASTM E408-13 standard.

[0130] The specific results are shown in Table 1.

[0131] 2. Switchgear thermal management performance test:

[0132] Inner surface temperature of the outer casing: Attach a thermocouple to the inside of the outer casing. The lower the value, the better the effect of radiative cooling + insulation layer.

[0133] Busbar temperature rise: Attach a thermocouple to the busbar overlap and record the temperature after stabilization minus the ambient temperature. The lower the value, the more effective the busbar radiant heat dissipation system is.

[0134] Average air temperature inside the cabinet: Temperature sensors are placed in the upper, middle and lower areas inside the cabinet to obtain the average value;

[0135] Thermal shock response time: The time required for the busbar temperature to reach 90% of its peak value from the initial temperature was recorded when the solar simulator was suddenly turned on and the current surge was increased.

[0136] The specific results are shown in Table 2.

[0137] Table 1: Basic performance test data of the radiation-cooling coating obtained in Preparation Example B

[0138]

[0139] Table 2: Overall Thermal Management Performance Test Data of Switchgear in Examples and Comparative Cases

[0140]

[0141] A comprehensive comparative analysis of the coating basic performance data in Table 1 and the switchgear thermal management performance data in Table 2 shows that the technical solution proposed in this application has significant synergistic advantages in terms of material micro-modification and macro-system heat dissipation. The specific analysis is as follows:

[0142] 1. Regarding the influence of microstructure on optical performance and thermal insulation effect, Table 1 shows that Example B1, which uses an aerogel-supported phase change microcapsule structure, has a solar reflectivity as high as 97.2%, far exceeding that of Example B7 (91.2%), which uses a simple mixed filler. This indicates that the special structure and uniform dispersion of the aerogel effectively improve the optical smoothness and backscattering capability of the coating. Further combining the data in Table 2, the inner surface temperature of the outer shell in Example 1 (38.5℃) is lower than that in Comparative Example 4 (49.8℃), and the average air temperature inside the cabinet is reduced by 13℃. This confirms that the micro-nano thermal insulation network constructed by the aerogel-supported microcapsule structure in the coating effectively blocks the conduction of external heat to the inside of the cabinet, demonstrating a synergistic effect of "reflection + thermal insulation."

[0143] 2. Regarding the crucial role of aerogel components in thermal insulation and heat dissipation: As shown in Table 1, when solid microspheres were used instead of hydrophobic aerogel (Preparation Example B6), the thermal emissivity of the coating decreased significantly to 92.1%. Corresponding to the data in Comparative Example 3 in Table 2, the inner surface temperature of its outer shell soared to 47.6℃, approaching the state without thermal insulation treatment. This indicates that the nanoporous structure of the aerogel is key to achieving efficient thermal insulation. Solid microspheres, due to their high thermal conductivity, cannot form an effective thermal barrier, leading to a large amount of external heat penetrating in and weakening the overall cooling effect of the system.

[0144] 3. Regarding the thermal buffering and response mechanism of phase change materials and thermally conductive fillers: Although the optical properties of prepared examples B4 (liquid paraffin) and B5 (talc) in Table 1 are not significantly different from those of B1 (both have reflectivities above 96%), they show differences in the dynamic thermal tests in Table 2:

[0145] The effect of latent heat of phase change: The thermal shock response time of Comparative Example 1 (liquid paraffin) was only 22 min, far lower than the 48 min of Example 1. This indicates that the solid-liquid phase change endothermic mechanism of n-octadecane in Example 1 provides a huge latent heat capacity, which can effectively delay the temperature rise rate caused by the current impact and play a "peak-shaving" role;

[0146] The effect of enhanced thermal conductivity: The busbar temperature of Comparative Example 2 (talc replacing boron nitride) increased by 41.2K, which is higher than that of Example 1 (32.4K). This shows that even with phase change materials, without the assistance of a highly thermally conductive boron nitride network, the heat conduction inside the microcapsule is hindered, and the heat cannot be absorbed by the core material in time, resulting in a significant reduction in the heat dissipation efficiency of the busbar.

[0147] Looking at Tables 1 and 2, as the content of functional particles increases (from Example 2 to Example 3), the reflectivity increases slightly, especially the thermal shock response time, which increases from 42 min to 52 min, indicating enhanced heat storage capacity. However, Example 1 achieves excellent overall cost-effectiveness with a suitable ratio (both temperature rise control and reflectivity are at a high level), verifying the rationality and efficiency of the formulation design of this scheme.

[0148] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. The above embodiments only illustrate several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A composite heat-dissipation low-voltage switchgear based on radiation refrigeration, characterized in that, It includes the equipment body, the outer shell radiant cooling and heat dissipation system, the busbar radiant cooling and heat dissipation system, the natural convection ventilation system, and the auxiliary monitoring module. The outer shell radiant cooling and heat dissipation system and the busbar radiant cooling and heat dissipation system both include a radiant cooling layer. The equipment body exchanges heat with the external environment or internal space through the radiant cooling layer.

2. The composite heat-dissipation low-voltage switch cabinet based on radiation refrigeration according to claim 1, characterized in that, The radiative cooling and heat dissipation of the outer casing, from the outside to the inside, includes the following: (1) Self-cleaning layer: The self-cleaning layer is a superhydrophobic or photocatalytic self-cleaning coating, the material of which includes silica sol-gel and titanium dioxide photocatalytic material, with a thickness of 10-30μm; (2) Radiation cooling layer: The radiation cooling layer has a solar reflectivity ≥95% and an average emissivity ≥95% in the 8-13μm band, and adopts one of the following: radiation cooling coating, radiation cooling film and integrated radiation cooling metal plate; (21) If it is a radiation cooling coating, the thickness is 50-200 μm; (22) If it is a radiation-cooling film with a thickness of 100-500 μm, it is bonded with an adhesive; (23) If it is an integrated radiation cooling metal plate, the radiation cooling structure is directly formed on the surface of the metal plate by anodizing or microstructure etching; (3) Substrate layer: The substrate layer is the main body of the shell structure, and the material includes 1.0-2.0mm thick galvanized steel plate, aluminum alloy plate and SMC composite material; (4) Insulation layer: The insulation layer is made of low thermal conductivity material with a thermal conductivity of ≤0.05 W / (m·K) and a thickness of 3-10mm.

3. The composite heat-dissipation low-voltage switch cabinet based on radiation refrigeration according to claim 1, characterized in that, The busbar radiant cooling and heat dissipation system comprises, from the inside out: (1) Busbar body: The busbar body is made of copper; (2) Insulating and thermally conductive layer: The insulating and thermally conductive layer is made of ceramic fiber composite material and polyimide thermally conductive film. The insulating and thermally conductive layer is required to have a thermal conductivity ≥0.5 W / (m·K), a breakdown voltage ≥10kV, and a thickness of 20-50μm. (3) Interface transition layer: The interface transition layer is made of silane coupling agent and has a thickness of 5-10 μm; (4) Radiation cooling layer: The thickness of the busbar radiation cooling layer is 50-200μm, and it adopts one of the following: radiation cooling coating, radiation cooling film and integrated radiation cooling metal plate.

4. The composite heat-dissipation low-voltage switch cabinet based on radiation refrigeration according to claim 1, characterized in that, The natural convection ventilation system includes an air inlet located at the bottom of the housing and an air outlet located at the top of the housing. Both the air inlet and the air outlet are equipped with dust filters with a filter opening of ≤5μm.

5. The composite heat-dissipation low-voltage switch cabinet based on radiation refrigeration according to claim 1, characterized in that, The auxiliary monitoring module includes a temperature sensor, a controller, and a low-power temperature-controlled fan. The temperature sensor is located in the hot spot area inside the equipment. The controller is electrically connected to the temperature sensor and can monitor the internal temperature of the equipment in real time and provide feedback data. The low-power temperature-controlled fan is automatically started and stopped by the controller based on the temperature data.

6. The composite heat-dissipation low-voltage switch cabinet based on radiation refrigeration according to claim 1, characterized in that, The radiation cooling layer comprises the following raw materials in parts by weight: 30-60 parts film-forming resin, 30-45 parts high-reflectivity filler, 10-20 parts infrared radiation filler, 5-15 parts heat insulation and strengthening filler, 1-5 parts additives, 5-15 parts solvent, 10-20 parts aerogel-supported phase change microcapsule composite particles, and 1-2 parts interface modifier.

7. A composite heat dissipation low-voltage switchgear based on radiative cooling according to claim 6, characterized in that, The film-forming resin includes at least one of polyvinylidene fluoride, polyvinylidene fluoride, or polytetrafluoroethylene. The high-reflectivity filler includes at least one of titanium dioxide, zinc oxide, and barium sulfate; The infrared radiation filler includes at least one of silicon carbide, aluminum nitride, and boron nitride; The heat insulation and reinforcing filler is air glass microspheres with a particle size of 10-50μm; The additives include at least one of dispersants, leveling agents, and UV stabilizers; The solvent includes at least one of acetone, ethyl acetate, or butanone.

8. A composite heat dissipation low-voltage switchgear based on radiative cooling according to claim 6, characterized in that, The aerogel-supported phase change microcapsule composite particles comprise the following raw materials in parts by weight: 30-40 parts of n-octadecane, 10-15 parts of melamine, 20-30 parts of formaldehyde solution, 2-5 parts of modified boron nitride nanosheets, 15-25 parts of hydrophobic silica aerogel powder, and 1-3 parts of silane coupling agent KH-560.

9. The composite heat-dissipation low-voltage switch cabinet based on radiation refrigeration according to claim 8, characterized in that, The preparation method of the aerogel-supported phase change microcapsule composite particles includes the following steps: S1: Mix melamine with 35-40wt% formaldehyde aqueous solution, adjust the pH to 8.5-9.0 with triethanolamine, and heat and stir in a water bath at 65-75℃ for 30-60 minutes to obtain a prepolymer solution; S2: Modified boron nitride nanosheets are ultrasonically dispersed in deionized water, heated to 65-75℃, molten n-octacosan, and sheared at high speed at 8000-10000 rpm for 15-30 min to obtain an emulsion. S3: Adjust the pH of the emulsion to 3.5-4.5 with citric acid, add the prepolymer solution from step S1 dropwise to the emulsion within 30-45 min, stir and react at 75-80℃ for 2-3 h to solidify into a shell, filter, wash and vacuum dry at 55-60℃ for 10-12 h to obtain phase change microcapsules. S4: The dried phase change microcapsules and aerogel powder were dispersed in anhydrous ethanol and mixed and adsorbed at a low speed of 300-500 rpm at 25-30℃ for 2-3 hours; then silane coupling agent KH-560 was added, and the temperature was raised to 65-70℃ and refluxed for 3-4 hours; after the reaction was completed, the mixture was filtered and vacuum dried at 65-75℃ for 10-12 hours to obtain aerogel-supported phase change microcapsule composite particles.

10. The composite heat-dissipation low-voltage switch cabinet based on radiation refrigeration according to claim 6, characterized in that, The method for preparing the radiation cooling layer includes the following steps: S1 (Preparation of matrix slurry): Mix film-forming resin, high reflectivity filler, infrared radiation filler, heat insulation and reinforcing filler, additives and solvent, keep the temperature between 20-30℃, and perform sand milling at 2000-2500rpm for 1-2 hours to obtain matrix slurry. S2 (Preparation of coating slurry): Add hydrophobic silica aerogel powder and silane coupling agent KH-560 to the matrix slurry, control the system temperature to not exceed 35℃, and disperse at a low shear speed of 600-800rpm for 30-45min to obtain radiation cooling coating slurry. S3 (Coating and Segmented Curing): The slurry obtained from S1 and S2 is applied to the surface of the substrate, and then cured using a segmented curing process to form a radiation cooling layer; The segmental curing process comprises: a first stage of leveling at room temperature of 20-25 DEG C for 15-20 min; a second stage of pre-curing by baking at 80-90 DEG C for 20-30 min; and a third stage of final curing by baking at 150-160 DEG C for 45-60 min.

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