Heat dissipation device for power transformer

Abstract

The invention relates to the technical field of power transformers, in particular to a heat dissipation device for a power transformer, which comprises a box body, a transformer, an insulator, a heat dissipation sheet and a base, and is characterized in that the heat dissipation sheet comprises porous ceramic radiation fins, a phase change energy storage cavity wrapped with a soft magnetic alloy layer, a liquid storage box, a wax storage pipe, a U-shaped pipe and a graphene-based bidirectional heat conduction diaphragm; the liquid storage box is communicated with the wax storage pipe, and the U-shaped pipe is communicated with the liquid storage box and the phase change energy storage cavity wrapped with the soft magnetic alloy layer. According to the heat dissipation device for the power transformer, the phase change energy storage cavity can dynamically store and release heat generated during operation of the transformer, excessive heat is absorbed during heavy load to avoid sudden rise of oil temperature, heat is released during light load to maintain the temperature stable, the heat dissipation path can be widened through infrared radiation heat dissipation of the porous ceramic radiation fins, and the heat dissipation efficiency is improved. And meanwhile, the graphene-based diaphragm and the gradient framework enhance the heat transfer efficiency, efficient temperature control under all working conditions is integrally achieved, and the insulating performance and the service life of the transformer are guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power transformers, in particular to a heat dissipation device for a power transformer. BACKGROUND

[0002] A power transformer is a core device for power transmission and distribution in a power system. During operation, the winding and core of the power transformer continuously generate heat. If the heat cannot be dissipated in time, the oil temperature will rise, the insulation performance will decrease, and even equipment failure will occur.

[0003] Currently, conventional power transformers mostly use a heat dissipation mode of a conventional fin-type radiator combined with natural air cooling or forced air cooling. However, this type of heat dissipation scheme has the core problem of insufficient heat dissipation efficiency and working condition adaptability. The heat dissipation structure of the conventional radiator is fixed, and only a single convection or conduction heat exchange mode can be used, which cannot reduce the instantaneous high temperature of the transformer during heavy load, and it is also difficult to maintain heat dissipation stability during light load. In addition, the fins are prone to dust accumulation and are inconvenient to disassemble and maintain, which further aggravates the decline of heat dissipation performance, and cannot meet the heat dissipation requirements of the long-term stable operation of the transformer under complex power grid working conditions. SUMMARY

[0004] The purpose of the present application is to provide a heat dissipation device for a power transformer to solve the problems raised in the background.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a heat dissipation device for a power transformer, comprising a box body, a transformer arranged in the box body, an insulator mounted on the top of the transformer, a fin connected to the bottom of the transformer, and a base for cleaning the fin, wherein the fin comprises porous ceramic radiation fins, a phase change energy storage cavity wrapped with a soft magnetic alloy layer, a liquid storage box, a wax storage tube, a U-shaped tube, and a graphene-based bidirectional heat conduction diaphragm, the liquid storage box is in communication with the wax storage tube, and the U-shaped tube is in communication with the liquid storage box and the phase change energy storage cavity wrapped with the soft magnetic alloy layer.

[0006] The liquid storage box is filled with nanofluid insulating oil, the nanofluid insulating oil is added with Al2O3 nanoparticles with a volume fraction of 0.5%, and the thermal conductivity thereof is ≥0.16 W / (m·K); the wax storage tube is filled with paraffin-based phase change material, and the phase change energy storage cavity wrapped with the soft magnetic alloy layer also has paraffin-based phase change material with a phase change temperature of 60℃.

[0007] Preferably, the phase change energy storage cavity wrapped with the soft magnetic alloy layer is filled with a gradient foam copper framework, the porosity of the gradient foam copper framework increases from 60% on the side of the heat source layer to 90% on the side of the heat dissipation layer, and the thermal conductivity of the gradient foam copper framework is >300 W / (m·K).

[0008] Preferably, the porous ceramic radiating fins have micron-level radiating grooves on their surface, and the infrared emissivity of the fins corresponding to the micron-level radiating grooves is >0.9; the porous ceramic radiating fins are embedded with phase change microcapsules with a phase change temperature of 55°C, and the porous ceramic radiating fins are connected to the phase change energy storage cavity wrapped with the soft magnetic alloy layer through heat-conducting pillars.

[0009] Preferably, the graphene-based bidirectional thermally conductive membrane is a composite structure of graphene sheets and polyimide support network with a thickness of 0.2 mm. The graphene sheets are laid perpendicular to the heat flow path. The polyimide support network has a buffered phase change material volume expansion rate of ≤15%, and the thermal conductivity of the graphene sheets is >1500 W / (m·K).

[0010] Preferably, the inner wall of the heat sink is further embedded with a ring-shaped permanent magnet, the magnetic field strength of which is 200 mT; the soft magnetic alloy layer on the outer wall of the phase change energy storage cavity encasing the soft magnetic alloy layer can generate a magnetic attraction force >500 N with the ring-shaped permanent magnet, and the contact thermal resistance between the phase change energy storage cavity encasing the soft magnetic alloy layer and the heat sink is ≤0.002 m. 2 ·K / W.

[0011] Preferably, the section of the U-shaped tube near the heat source layer is a spiral section, and the section near the heat dissipation layer is a straight section. Both ends of the U-shaped tube are also provided with capillary cores made of sintered copper powder, which can drive the circulation of nanofluid insulating oil through the thermosiphon effect.

[0012] Preferably, the surface of the heat sink is further coated with a heat dissipation coating, and a metal sheet is embedded inside the heat sink.

[0013] Preferably, the base includes a mounting frame, a motor, a lead screw, a bearing bracket, a lead screw nut, a connecting rod, a movable rod, a insert plate, and a cleaning block. The motor is mounted on the mounting frame. One end of the lead screw is connected to the motor output shaft, and the other end engages with a bearing in the bearing bracket. The lead screw nut is sleeved on the lead screw. The two ends of the connecting rod are respectively connected to the lead screw nut and the movable rod. The insert plate is connected to the movable rod. The cleaning block is disposed on the side of the insert plate facing the heat sink. The base also has a through groove, through which the movable rod passes. After the motor is started, it can drive the cleaning block to reciprocate along the surface of the heat sink to achieve cleaning.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] 1. This heat dissipation device for power transformers features a phase change energy storage chamber that dynamically stores and releases the heat generated during transformer operation. Under heavy load, it absorbs excess heat to prevent a sudden rise in oil temperature, while under light load, it releases heat to maintain temperature stability. Combined with the infrared radiation heat dissipation of porous ceramic radiating fins, it can broaden the heat dissipation path. At the same time, the graphene-based diaphragm and gradient skeleton enhance the heat transfer efficiency, achieving efficient temperature control under all operating conditions and ensuring the insulation performance and service life of the transformer.

[0016] 2. This heat dissipation device for power transformers features a magnetic phase change energy storage chamber with boltless connection, allowing for easy assembly and disassembly without specialized tools, thus reducing the difficulty of on-site maintenance. The soft magnetic alloy layer can shield the transformer from electromagnetic interference, preventing the phase change material from experiencing a decrease in thermal stability due to electromagnetic influence. In addition, the automatic cleaning component can promptly remove dust accumulation on the heat sink, preventing blockage of the heat dissipation channels, ensuring long-term stable heat dissipation performance, and reducing the frequency of manual maintenance.

[0017] 3. This heat dissipation device for power transformers uses nanofluid insulating oil, which improves thermal conductivity while maintaining good electrical insulation, avoiding the problem of traditional heat dissipation media having difficulty in balancing thermal conductivity and insulation performance. The special coating on the surface of the heat sink and the three-proof protection design can resist the corrosion of coastal areas with high salt spray and dust. At the same time, the shock absorption and sealing structure can buffer equipment vibration and prevent medium leakage, ensuring the reliable operation of the device under harsh working conditions and expanding the applicable scenarios of transformers. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0020] Figure 2 This is a schematic diagram of the bottom structure of the transformer of the present invention;

[0021] Figure 3 for Figure 2 Enlarged schematic diagram of the structure at point A in the middle;

[0022] Figure 4 This is a cross-sectional view of the heat sink of the present invention;

[0023] Figure 5 This is a schematic diagram of the porous ceramic radiating fin structure of the present invention;

[0024] Figure 6 This is a schematic diagram of the base structure of the present invention.

[0025] In the diagram: 1. Housing; 2. Transformer; 3. Insulator; 4. Heat sink; 401. Porous ceramic radiating fins; 4011. Micron-level radiating groove; 4012. Heat-conducting column; 4013. Phase change microcapsule; 402. Phase change energy storage cavity encased in a soft magnetic alloy layer; 403. Liquid storage box; 404. Wax storage tube; 405. Heat dissipation coating; 406. Metal sheet; 407. Ring permanent magnet; 408. Gradient foam 409. Copper frame; 410. Heat source layer; 411. Graphene-based bidirectional thermal insulation membrane; 412. Heat dissipation layer; 413. U-shaped tube; 414. Straight section; 415. Capillary wick; 5. Base; 501. Mounting bracket; 502. Motor; 503. Lead screw; 504. Bearing bracket; 505. Through groove; 506. Lead screw nut; 507. Connecting rod; 508. Movable rod; 509. Insert plate; 510. Cleaning block. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] Please see Figures 1-6 This invention provides a technical solution: a heat dissipation device for a power transformer, comprising a housing 1, a transformer 2, insulators 3, heat sinks 4, and a base 5. The transformer 2 is fixedly installed in the internal cavity of the housing 1 by shock-absorbing pads made of nitrile rubber with a thickness of 20mm, which can buffer the vibration of the transformer during operation. The insulators 3 are symmetrically installed on the outside of the terminals on the top of the transformer 2. The insulators 3 are made of ceramic and have a creepage distance ≥300mm. The heat sinks 4 are welded and fixed to the heat dissipation area at the bottom of the transformer 2 by vacuum brazing. The thermal conductivity of the welded joint is ≥100W / (m·K). The base 5 is symmetrically arranged at the bottom of the housing 1 and is adapted to the bottom of the heat sinks 4. The base 5 is made of Q235 carbon steel and the surface is hot-dip galvanized for rust prevention, with a coating thickness ≥8μm.

[0029] The core heat dissipation structure of the heat sink 4 includes porous ceramic radiating fins 401, a phase change energy storage cavity 402 wrapped with a soft magnetic alloy layer, a liquid storage box 403, a wax storage tube 404, a U-shaped tube 412, and a graphene-based bidirectional thermal conductive membrane 410. The liquid inlet of the liquid storage box 403 and the liquid outlet of the wax storage tube 404 are connected by a fluororubber hose with an inner diameter of 10mm, and the connection is sealed with a clamp. One end of the U-shaped tube 412 is inserted into the bottom of the liquid storage box 403, and the other end extends into the phase change energy storage cavity 402 wrapped with a soft magnetic alloy layer. 2 is made of copper tubing with a wall thickness of 1.5mm. The inner wall is polished and has a roughness Ra≤0.8μm. The graphene-based bidirectional thermally conductive membrane 410 is embedded in the interlayer between the phase change energy storage cavity 402 wrapped with a soft magnetic alloy layer and the heat source layer 409 of the heat sink 4 using a high-temperature resistant adhesive. The temperature resistance range of the adhesive is -40℃~200℃. The porous ceramic radiating fins 401 are fixedly connected to the outer wall of the phase change energy storage cavity 402 wrapped with a soft magnetic alloy layer through a heat-conducting column 4012. The heat-conducting column 4012 is made of oxygen-free copper, with a diameter of 8mm and a length of 15mm.

[0030] Furthermore, the liquid storage box 403 is pre-filled with nanofluid insulating oil, which is prepared by adding 0.5% by volume of Al2O3 nanoparticles to the base mineral insulating oil. The preparation process is as follows: first, the Al2O3 nanoparticles are modified with silane coupling agent KH550, then mixed with the base insulating oil and ultrasonically dispersed. Its thermal conductivity is stably maintained at ≥0.16W / (m·K), and the breakdown voltage is ≥45kV. The wax storage tube 404 is filled with solid paraffin-based phase change material, which is an octadecane-high-density polyethylene composite system with a melting point of 60℃ and a latent heat of phase change of ≥180kV. J / kg; The phase change energy storage cavity 402, which is wrapped with a soft magnetic alloy layer, also contains the paraffin-based phase change material with a phase change temperature of 60°C. The cavity is also filled with a gradient foam copper skeleton 408, which is prepared by electrodeposition. The porosity is distributed in a gradient, gradually increasing from 60% on the side near the heat source layer 409 to 90% on the side near the heat dissipation layer 411. Its thermal conductivity is >300W / (m·K). The skeleton pore size increases from 0.5mm on the heat source side to 2mm on the heat dissipation side, which can realize the directional and efficient transfer of heat, while providing a buffer space for the volume expansion of the phase change material.

[0031] Furthermore, the substrate of the porous ceramic radiating fin 401 is silicon carbide porous ceramic with a porosity of 35%. Its outer surface is uniformly processed with micron-level radiating grooves 4011 by laser etching. The depth of the radiating grooves 4011 is 2-3 μm, the width is 5-8 μm, and the groove spacing is 10 μm, so that the overall infrared emissivity of the fin is >0.9. At the same time, the porous ceramic radiating fin 401 has a honeycomb-shaped accommodating cavity prefabricated inside, and the cavity is embedded with phase change microcapsules 4013 with a phase change temperature of 55℃. The phase change microcapsules are urea-formaldehyde resin coated with paraffin system, with a particle size of 50-80 μm and a latent heat of phase change ≥150kJ / kg, which can realize the storage and release of heat in the medium and low temperature range, and the filling amount of microcapsules is 40% of the fin volume.

[0032] Furthermore, the graphene-based bidirectional thermally conductive diaphragm 410 is manufactured using a composite molding process of graphene sheets and a polyimide support mesh. The specific process is as follows: first, graphene sheets are laid flat along the direction perpendicular to the heat flow, and then a polyimide support mesh is laid on top. The diaphragm is then hot-pressed at 150℃ and 5MPa, with the overall thickness precisely controlled to 0.2mm. The in-plane thermal conductivity of the graphene sheets is >1500W / (m·K), which enables unidirectional rapid heat transfer from the nanofluid to the phase change material, avoiding heat backflow when the phase change material releases heat. The polyimide support mesh has a cross-linked structure with an elongation at break of ≥30%, which can buffer the volume expansion rate of the phase change material of ≤15%, ensuring that the cavity is free from stress damage and leakage risk. The diaphragm's operating temperature range is -20℃ to 180℃.

[0033] Furthermore, an annular permanent magnet 407 with a magnetic field strength of 200mT is embedded in the annular groove of the inner wall of the heat sink 4. The permanent magnet is of neodymium iron boron N35 type and is nickel-plated for rust prevention. The outer wall of the phase change energy storage cavity 402, which is wrapped with a soft magnetic alloy layer, is wrapped with a soft magnetic alloy layer through an electroplating process. The soft magnetic alloy is 1J50 iron-nickel alloy with a plating thickness of 50μm. After the two are assembled, they can generate a magnetic attraction force of >500N. On the one hand, this enables boltless quick disassembly and assembly of the phase change energy storage cavity, with a disassembly and assembly time of ≤5min, which is convenient for later maintenance. On the other hand, it can reduce the contact thermal resistance between the phase change energy storage cavity and the heat sink 4 to ≤0.002m. 2 • K / W, while the soft magnetic alloy layer can shield the low-frequency electromagnetic interference generated during transformer operation, with an interference shielding rate of ≥80%, improving the thermal stability of the phase change material.

[0034] Furthermore, the U-shaped tube 412 adopts a segmented design for its piping structure. The section near the heat source layer 409 is a spiral section with a pitch of 20 mm and a spiral diameter of 30 mm. This section utilizes centrifugal force to enhance the turbulence of the nanofluid, increasing the turbulence intensity by 15%, resulting in a more uniform distribution of Al2O3 nanoparticles and a 15% increase in heat exchange efficiency. The section near the heat dissipation layer 411 is a straight section 413 with a length of 50 mm. The channel is parallel to the surface of the heat sink, forming a thin-film heat exchange layer with a thickness of 0.2 mm, reducing the flow resistance of the nanofluid. Simultaneously, both ends of the U-shaped tube 412 are sintered and fixed with capillary cores 414 made of sintered copper powder. The porosity of the capillary cores is 65%, and the permeability is 1×10⁻⁶. -12 m 2 The nanofluid insulating oil can be driven to circulate autonomously through the thermosiphon effect of phase change materials, with a circulation flow rate ≥0.5L / min, without the need for an additional power source.

[0035] In addition, the outer surface of the heat sink 4 is coated with a high thermal conductivity heat dissipation coating 405 by electrostatic spraying. The coating material is a nano-silicon carbide-acrylic resin composite coating with a thickness of 0.1-0.15mm and a thermal conductivity of ≥20W / (m·K), which can further reduce the surface thermal resistance of the heat sink. The heat sink 4 is also embedded with copper metal sheets 406. The metal sheets 406 are distributed in a grid pattern with a grid aperture of 5mm and a metal sheet thickness of 0.5mm. They are integrally brazed with the heat sink body to enhance the thermal conductivity of the heat sink body and increase the overall thermal conductivity of the heat sink by 25%.

[0036] For cleaning and maintenance of the heat sink 4, the base 5 is equipped with an automatic cleaning mechanism, the specific structure of which includes a mounting bracket 501, a motor 502, a lead screw 503, a bearing bracket 504, a lead screw nut 506, a connecting rod 507, a movable rod 508, a plug plate 509, and a cleaning block 510; the mounting bracket 501 and the bearing bracket 504 are symmetrically welded to the top of the base 5, the weld is a fillet weld with a weld leg height of 8mm; the motor 502 is a stepper motor, model 57BYG250, with a rated speed of 1000r / min, and is fixed to the mounting surface of the mounting bracket 501 by bolts; the lead screw 503 is a ball screw with a lead of 5mm, one end of which is connected to the output shaft of the motor 502 through a flexible coupling, and the other end is rotated with a deep groove ball bearing in the bearing bracket 504. The bearing is model 6203 with an IP65 sealing rating; the lead screw nut 506 is threaded onto the outer wall of the lead screw 503 with a clearance ≤0.01mm; the two ends of the connecting rod 507 are hinged to the lead screw nut 506 and the movable rod 508 respectively via spherical bearings; one end of the insert plate 509 is welded to the movable rod 508, and the other end is bonded to a cleaning block 510, which is made of polyurethane sponge with a Shore A hardness of 30A and is impregnated with an insulating cleaning agent, which is a mixture of isopropyl alcohol and deionized water with a volume ratio of 1:1; a through groove 505 with a width of 20mm is provided in the middle of the base 5, through which the movable rod 508 slides, and a nylon guide sleeve is provided between the movable rod and the through groove, with a friction coefficient ≤0.15.

[0037] When transformer 2 generates heat during operation, the heat is first conducted to the heat source layer 409 of heat sink 4. When the temperature of the heat source layer rises to 60℃, the solid paraffin-based phase change material in the wax storage tube 404 melts due to the heat. The nanofluid insulating oil in the liquid storage box 403 enters the phase change energy storage cavity 402 wrapped with a soft magnetic alloy layer through the spiral section of the U-shaped tube 412 under the thermosiphon effect. The heat carried by the nanofluid is quickly introduced into the phase change energy storage cavity through the graphene-based bidirectional thermal conductive membrane 410. The gradient foam copper skeleton 408 evenly disperses the heat to the paraffin-based phase change material. The phase change material absorbs the heat and changes from solid to liquid, realizing peak heat storage. The volume of each component is 100cm³. 3 The energy storage chamber has a heat storage capacity of ≥18kJ. When the transformer load decreases and the oil temperature drops below 55℃, the phase change material solidifies from a liquid state to release heat. The heat is carried back to the transformer oil tank by the nanofluid, so that the overall oil temperature fluctuation range is controlled within ±5℃, and the transformer insulation aging is avoided due to sudden changes in oil temperature.

[0038] During phase change heat storage, the heat from the heat sink 4 is transferred to the porous ceramic radiant fins 401 via heat conduction through the heat-conducting column 4012, with a heat flux ≥500W / m. 2Under high-temperature conditions (fin temperature > 55℃), the phase change microcapsules 4013 inside the fins first absorb some heat, which delays the temperature rise of the fins by 3-5 minutes. The remaining heat is dissipated to the environment through the micron-level radiation grooves 4011 in the form of infrared radiation, with radiative heat dissipation accounting for 40% of the total heat dissipation. Under low-temperature conditions (fin temperature < 55℃), the phase change microcapsules 4013 release the stored heat, and the porous ceramic radiation fins 401, acting as a heat-conducting extension surface, transfer the heat to the air through convection, with a convective heat transfer coefficient ≥ 25 W / (m²). 2 ·K), achieving efficient heat dissipation under all operating conditions.

[0039] When the dust accumulation thickness on the surface of heat sink 4 is ≥0.1mm, the temperature difference between the inner and outer walls of the heat sink is monitored by an infrared temperature sensor. When the temperature difference is >5℃, cleaning is initiated. The external controller PLC (model S7-200SMART) sends a command to start motor 502. The output shaft of motor 502 drives the lead screw 503 to rotate. The lead screw nut 506 moves along the axial direction of the lead screw 503 at a speed of 5mm / s. Through connecting rod 507 and movable rod 508, the insert plate 509 and cleaning block 510 move back and forth along the surface of heat sink 4. The reciprocating stroke is 90% of the height of the heat sink. The flexible cleaning layer of cleaning block 510 can effectively wipe away the accumulated dust and debris on the surface of the heat sink, with a cleaning efficiency of ≥95%, ensuring unobstructed heat dissipation channels. After cleaning, the motor automatically stops. The cleaning cycle can be set to 7 days / time through the controller.

[0040] All fluid connections in this device are sealed with fluororubber sealing rings. The sealing rings have a Shore hardness of 70A and an operating temperature range of -20℃ to 200℃, ensuring no leakage of the nanofluid insulating oil with a leakage rate of <0.01mL / h. The top of the enclosure 1 is equipped with a rain cover made of stainless steel with a 30° tilt angle to prevent outdoor rainwater from entering. The non-heat-conducting areas of the heat sink 4 are coated with a three-proof paint, which can prevent moisture, mildew, and salt spray, achieving an IP65 protection rating, suitable for complex outdoor environments such as coastal and dusty areas.

[0041] It should be noted that the power supply voltage of the motor 502 in this invention is 220VAC, the power is 50W, and its operating status can be controlled by an external controller to start / stop, stroke and speed; the phase change energy storage cavity 402 is made of 304 stainless steel with a wall thickness of 2mm and a pressure resistance of ≥1MPa, which can withstand the pressure generated by the expansion of the phase change material.

[0042] Working principle:

[0043] When using transformer 2, the heat generated by transformer 2 is transferred to the heat sink 4 at the bottom. The wax strip filled in the wax storage tube 404 melts after reaching a certain temperature, causing the nanofluid insulating oil inside the liquid storage box 403 to flow into the phase change energy storage cavity 402 wrapped with soft magnetic alloy layer. The nanofluid insulating oil has 0.5% volume fraction Al2O3 nanoparticles added, and the thermal conductivity is increased to 0.16W / (m·K). The phase change energy storage cavity 402 has a built-in paraffin-based phase change material integrated into the heat sink 4. It absorbs the heat of the oil under heavy load and releases the heat under light load, so that the oil temperature fluctuation range is controlled within ±5℃.

[0044] A non-uniform pore size gradient foam copper skeleton is filled inside the phase change energy storage cavity, with the porosity increasing from 60% on the heat source side to 90% on the heat dissipation side, and then impregnated with a paraffin-based phase change material.

[0045] Heat source layer: The high thermal conductivity of the foamed copper skeleton enhances the transfer of heat from nanofluid to phase change material, solving the problem of poor thermal conductivity in traditional phase change materials;

[0046] Heat dissipation layer: Increases the contact area between the phase change material and the heat sink, while providing a buffer space for the volume expansion of the phase change material and avoiding leakage in the cavity.

[0047] A porous ceramic radiating fin 401 is added to the outside of the heat sink 4 and connected to the phase change energy storage cavity through a heat-conducting column 4012.

[0048] The surface of the fin 401 is processed with micron-level radiative grooves 4011, and the internal microcapsules of phase change material 4013 are embedded.

[0049] At high temperatures: the phase change microcapsule 4013 absorbs heat, while the radiating fins 4 dissipate heat to the environment through infrared radiation;

[0050] At low temperatures: the phase change microcapsule 4013 releases heat, and the radiating fins 4 act as a heat-conducting extension surface to accelerate heat dissipation;

[0051] The graphene-based bidirectional thermal insulation membrane 410 adopts a composite structure of graphene sheets and polyimide support network, with the sheet direction perpendicular to the heat flow path and a thickness of only 0.2 mm.

[0052] The high thermal conductivity of graphene sheets allows heat to be unidirectionally introduced into the phase change material through the flow channel, preventing heat from flowing back when the phase change material releases heat.

[0053] The elastic structure of the polyimide support network can buffer the volume expansion of the phase change material;

[0054] A ring-shaped permanent magnet is embedded in the inner wall of the heat sink; the outer wall of the phase change energy storage cavity is wrapped with a soft magnetic alloy layer, and positioning grooves are machined on the surface; magnetic attraction enables quick disassembly and assembly during cavity maintenance; magnetic attraction pressure reduces the contact thermal resistance between the cavity wall and the heat sink to 0.002m. 2• Below K / W; the soft magnetic alloy layer can shield the electromagnetic interference of the transformer and improve the thermal stability of the phase change material.

[0055] Spiral section: Centrifugal force is used to enhance the turbulence of the nanofluid, making the nanoparticles more uniformly distributed and improving the heat exchange efficiency by 15%; Inline section: The channel is parallel to the surface of the heat sink, forming a thin film heat exchange layer to reduce the flow resistance of the nanofluid; Capillary wicks are set at both ends of the channel, and the nanofluid is driven to circulate through the thermosiphon effect of the phase change material without the need for additional power.

[0056] Two bases 5 are connected to mounting bracket 501 and bearing bracket 504. Mounting bracket 501 is used to mount motor 502. The bearing bracket 504 is equipped with ball bearings connected to lead screw 503. Motor 502 is started by controller. The output shaft of motor 502 drives lead screw 503 to rotate. Lead screw 503 drives lead screw nut 506 on its surface to move. When lead screw nut 507 moves, it drives insert plate 509 to move through connecting rod 507 and movable rod 508. After insert plate 509 and cleaning block 510 move, the surface of heat sink 4 can be cleaned.

[0057] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0058] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A heat dissipation device for a power transformer, comprising a housing (1), a transformer (2) disposed within the housing (1), an insulator (3) mounted on the top of the transformer (2), heat sinks (4) connected to the bottom of the transformer (2), and a base (5) for cleaning the heat sinks (4), characterized in that: The heat sink (4) includes porous ceramic radiating fins (401), a phase change energy storage cavity (402) wrapped with a soft magnetic alloy layer, a liquid storage box (403), a wax storage tube (404), a U-shaped tube (412), and a graphene-based bidirectional thermally conductive membrane (410). The liquid storage box (403) is connected to the wax storage tube (404), and the U-shaped tube (412) is connected to the liquid storage box (403) and the phase change energy storage cavity (402) wrapped with the soft magnetic alloy layer. The liquid storage box (403) is filled with nanofluid insulating oil, which contains Al2O3 nanoparticles with a volume fraction of 0.5% and a thermal conductivity ≥0.16W / (m·K); the wax storage tube (404) is filled with paraffin-based phase change material, and the phase change energy storage cavity (402) wrapped with soft magnetic alloy layer is also filled with paraffin-based phase change material with a phase change temperature of 60℃.

2. A heat dissipation device for a power transformer according to claim 1, characterized in that: The phase change energy storage cavity (402) encasing the soft magnetic alloy layer is filled with a gradient foam copper skeleton (408). The porosity of the gradient foam copper skeleton (408) increases from 60% on the heat source layer (409) side to 90% on the heat dissipation layer (411) side, and the thermal conductivity of the gradient foam copper skeleton (408) is >300W / (m·K).

3. A heat dissipation device for a power transformer according to claim 1, characterized in that: The porous ceramic radiating fin (401) has micron-level radiating grooves (4011) on its surface, and the infrared emissivity of the fin corresponding to the micron-level radiating grooves (4011) is >0.9; the porous ceramic radiating fin (401) is embedded with a phase change microcapsule (4013) with a phase change temperature of 55°C, and the porous ceramic radiating fin (401) is connected to the phase change energy storage cavity (402) wrapped with a soft magnetic alloy layer through a heat-conducting column (4012).

4. A heat dissipation device for a power transformer according to claim 1, characterized in that: The graphene-based bidirectional thermal insulation membrane (410) is a composite structure of graphene sheets and polyimide support network with a thickness of 0.2 mm. The graphene sheets are laid in a direction perpendicular to the heat flow path. The polyimide support network has a buffered phase change material volume expansion rate of ≤15%, and the graphene sheet has a thermal conductivity of >1500W / (m·K).

5. A heat dissipation device for a power transformer according to claim 1, characterized in that: The inner wall of the heat sink (4) is also embedded with a ring-shaped permanent magnet (407), the magnetic field strength of which is 200mT; the soft magnetic alloy layer on the outer wall of the phase change energy storage cavity (402) wrapped with the soft magnetic alloy layer can generate a magnetic attraction force of >500N with the ring-shaped permanent magnet (407), and the contact thermal resistance between the phase change energy storage cavity (402) wrapped with the soft magnetic alloy layer and the heat sink (4) is ≤0.002m. 2 ·K / W.

6. A heat dissipation device for a power transformer according to claim 1, characterized in that: The section of the U-shaped tube (412) near the heat source layer (409) is a spiral section, and the section near the heat dissipation layer (411) is a straight section (413). Both ends of the U-shaped tube (412) are also provided with capillary cores (414) made of sintered copper powder, which can drive the circulation of nanofluid insulating oil through the thermosiphon effect.

7. A heat dissipation device for a power transformer according to claim 1, characterized in that: The surface of the heat sink (4) is also coated with a heat dissipation coating (405), and a metal sheet (406) is also embedded inside the heat sink (4).

8. A heat dissipation device for a power transformer according to claim 1, characterized in that: The base (5) includes a mounting bracket (501), a motor (502), a lead screw (503), a bearing bracket (504), a lead screw nut (506), a connecting rod (507), a movable rod (508), a insert plate (509), and a cleaning block (510). The motor (502) is mounted on the mounting bracket (501). One end of the lead screw (503) is connected to the output shaft of the motor (502), and the other end is engaged with the bearing inside the bearing bracket (504). The lead screw nut (506) is sleeved on the lead screw (503). The connecting rod (507) is connected to the lead screw nut (506) and the movable rod (508) at both ends respectively. The insert plate (509) is connected to the movable rod (508). The cleaning block (510) is set on the side of the insert plate (509) facing the heat sink (4). The base (5) is also provided with a through groove (505). The movable rod (508) passes through the through groove (505). After the motor (502) is started, it can drive the cleaning block (510) to move back and forth along the surface of the heat sink (4) to achieve cleaning.

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