Multi-mode cooling system

Abstract

The invention discloses a multi-mode cooling system, which comprises a transformer main body, a primary cooling loop and a secondary cooling loop, and is characterized in that the transformer main body comprises a sealed shell, and an iron core, a winding and an immersed cooling liquid which are arranged in the sealed shell; the primary cooling loop comprises radiators on the front side and the rear side of the transformer main body and a multi-needle-net type ion wind radiating device; the secondary cooling loop comprises an evaporator, a condenser, a water evaporation cooling device and related connecting pipelines, the water evaporation cooling device comprises a water tank at the top, a valve, a packing layer, an air draft fan and a receiving disc, when the load of the transformer is increased, the valve is opened to provide cooling water, micro capillary pores of the packing layer are utilized to form a spraying opening for water evaporation cooling, and the water evaporation cooling device is connected with the condenser. And the air draft fan is started to accelerate the air to flow from top to bottom. The cooling mode is selected according to the operation working condition of the transformer, the whole device does not need to additionally provide driving force, refrigerant liquid can achieve self-driven circulation, and energy consumption is reduced while stable work of the transformer is guaranteed.

Description

Technical Field

[0001] The invention relates to a cooling system for an oil-immersed transformer. Background Art

[0002] With the acceleration of urbanization, power systems are evolving toward high voltage, large capacity, and long-distance transmission, resulting in the emergence of numerous high-voltage, extra-high-voltage, and ultra-high-voltage transformers. However, during transformer operation, the windings and core generate significant heat due to resistance losses, hysteresis losses, and eddy current losses. However, the ratio of surface area to volume is shrinking, making natural heat dissipation alone insufficient. This is driving the development of transformer cooling systems that are more compact, efficient, and low-noise. Therefore, a highly efficient and low-noise cooling system is needed to reliably dissipate heat from the transformer.

[0003] At present, air cooling is the most common and widely used cooling method for oil-immersed transformers, including oil-immersed air cooling and forced oil circulation air cooling. However, both air cooling modes are limited by the external ambient temperature. In particular, when the oil-immersed air cooling mode is operated under high temperatures in summer, the cooling mode may cause the transformer oil temperature to be too high, posing certain electrical hazards. Although the forced oil circulation air cooling mode can achieve forced air convection and improve the system cooling capacity, it relies on fan equipment and has problems such as high noise, high energy consumption, low cooling efficiency, and high operation and maintenance costs. Overall, the heat dissipation reliability is not high.

[0004] In addition, forced oil circulation and water cooling are often used in large-capacity and ultra-large-capacity oil-immersed transformers. This has enhanced the heat dissipation performance of the transformer cooling system to a certain extent. However, these methods all have the problem of uneven distribution of radiators, which easily causes local heat accumulation. Moreover, they can only achieve heat dissipation under a fixed load and cannot adjust the cooling system's heat dissipation capacity according to the actual operating conditions of the transformer's variable load operation. This causes large fluctuations in the transformer's oil temperature and wastes cooling resources. In summary, in order to meet the heat dissipation and cooling needs of oil-immersed transformers under variable operating conditions, it is urgent to develop a set of dynamic, efficient, and low-noise cooling technologies. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to propose a multi-mode cooling system for an immersed transformer which significantly improves the energy efficiency level of the cooling system and matches the load.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: A multi-mode cooling system comprising: The transformer body includes a sealed housing and an iron core and windings immersed in a cooling liquid, wherein the iron core and windings are immersed in the cooling liquid; A primary cooling circuit includes a radiator and a multi-needle-mesh ion wind heat dissipation device; the radiator is located on the front and rear sides of the transformer body; the multi-needle-mesh ion wind heat dissipation device uses negative high-voltage direct current provided by the transformer body as a power source to generate ion wind blowing toward the radiator; The secondary cooling circuit includes an evaporator, a condenser and a water evaporative cooling device; the evaporator is located on the left and right sides of the transformer body; the condenser and the water evaporative cooling device are located above the transformer body; the evaporator and the condenser are connected by a pipe; after the refrigerant absorbs the heat of the immersion coolant in the evaporator and vaporizes, it spontaneously flows to the condenser above under the influence of gravity, and after condensation in the condenser, it falls back into the evaporator to realize a self-driven cycle; the water evaporative cooling device includes a water tank, a valve, a packing layer, an exhaust fan and a receiving tray, and the water tank, valve and packing layer are distributed in sequence from top to bottom above the condenser, and the exhaust fan and the receiving tray are located below the condenser. When the transformer load increases, the valve is opened to provide cooling water, and the exhaust fan is turned on to accelerate the flow of water droplets, and the micro-capillary pores of the packing layer are used as spray ports to form water evaporative cooling.

[0007] The multi-needle-mesh ion wind heat dissipation device includes an auxiliary guide channel, a mesh electrode, a needle electrode, an insulating bracket and a slide rail. The mesh electrode is welded to the top of the auxiliary guide channel, and the needle electrode is located above the mesh electrode; insulating brackets with slide rails are provided outside the needle electrode and the mesh electrode; the transformer body provides negative high-voltage direct current to the needle electrode, the mesh electrode is grounded, the auxiliary guide channel is a tapered tube structure, and the end of the channel is located at the top of the radiator.

[0008] The multi-needle-mesh ion wind heat dissipation device utilizes the characteristic of small curvature radius at the needle electrode tip to obtain high electric field strength under high voltage, thereby ionizing the neutral molecules between the electrodes and generating a gas flow from the electrode with small curvature radius to the electrode with large curvature radius, namely the ion wind. Both the needle electrode and the mesh electrode are made of stainless steel. Several needle tips are processed on the stainless steel ring by precision machining to ensure that all needle tips are in the same plane to form a crown structure. Each needle tip is a discharge needle, and the entire crown-shaped ring serves as the cathode, which is provided with negative high-voltage direct current through the transformer body. The mesh electrode is the anode and is grounded to ensure that the needle tip plane of the needle electrode is parallel to the mesh electrode plane. The auxiliary guide channel is a tapered tube structure, and the end of the channel is located at the top of the radiator. According to the continuity equation and the Bernoulli equation principle, it can be seen that this structure can further increase the ion wind speed.

[0009] The evaporators on the left and right sides of the transformer body are shell-and-tube heat exchangers. Inspired by the typical tree-like structures of plant growth in nature, the heat exchangers are engineered into a tree-like fractal structure, achieving a large heat exchange area within a limited space. This allows the fluid to continuously change direction and speed during flow, enhancing heat transfer while reducing flow resistance. The condenser on top of the transformer body is a plate-fin heat exchanger. Inspired by the biological structure of sea urchin skeletal plates, the heat exchange plate surfaces undergo TPMS (Transport-by-Special-Metrics) reverse curvature processing, further increasing the fluid heat exchange area while ensuring an orderly and complex flow between the plates, effectively improving heat exchange efficiency.

[0010] When the transformer is running at low load, the primary cooling circuit relies solely on the natural convection of the primary cooling circuit radiator and the self-driving force of the working fluid in the secondary cooling circuit for cooling. When the transformer is running at medium load, a multi-needle-mesh ion wind heat dissipation device is connected, that is, forced convection heat exchange is used in the primary cooling circuit. When the transformer is running at high load, the valve of the water evaporative cooling device in the secondary cooling circuit is opened to provide cooling water for the condenser.

[0011] The working fluid of the evaporator and the condenser is refrigerant R134a, and the secondary fluid cooling medium of the condenser is water.

[0012] The packing layer is made of relatively low-cost plastic packing such as PP, PVDF orifice plate corrugated packing, etc.

[0013] The immersion cooling liquid is a hydrofluoric saturated compound, a hydrofluoric unsaturated compound, a perfluorinated saturated compound, a perfluorinated unsaturated compound or mineral oil.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention proposes an air-liquid multi-mode cooling system for oil-immersed transformers. By arranging two ion-wind-coupled radiators, two evaporators, and an air / liquid-cooled condenser on the top of the transformer, this system integrates multiple heat exchange mechanisms into a composite cooling structure, achieving efficient energy transfer and improving the transformer's heat dissipation performance under variable operating conditions. By introducing an ion wind generator without mechanical rotating parts and directly driving it using the high voltage generated by the transformer body to form an ion wind field, it replaces the traditional high-speed fan, significantly reducing operating noise and achieving low-noise auxiliary heat exchange on the radiator surface. By utilizing the gravitational potential difference between the evaporator and condenser to form a self-driven refrigerant circulation, eliminating the need for an external pump to drive the refrigerant circulation, this system solves the high energy consumption of fans and pumps in traditional cooling solutions and achieves low-energy operation of the two-phase heat exchange circuit. Furthermore, through a multi-mode switching operation strategy involving oil-immersed air cooling, liquid cooling, and forced air cooling, the system achieves dynamic and precise matching and adaptive response between cooling capacity and heat dissipation requirements, effectively avoiding overcooling or cooling lag. The system is particularly suitable for long-term stable operation under complex operating conditions and variable loads. This air-liquid cooling multi-mode cooling system not only achieves compact integration in structure, but also demonstrates comprehensive advantages in performance such as low noise, high energy efficiency, and strong load adaptability, providing a reliable solution for green, efficient, and intelligent thermal management of oil-immersed transformers.

[0015] 2. Utilizing the transformer's inherent high voltage characteristics, an ion wind cooling device is constructed. High voltage and multi-needle-mesh electrodes generate high-speed ion wind, and a tapered tube-structured auxiliary flow channel is constructed to further increase the ion wind speed and enhance the radiator's heat exchange capacity. Furthermore, the ion wind device can be periodically activated to clean the radiator surface, ensuring efficient operation.

[0016] 3. The evaporator and condenser adopt a tree-like fractal structure and a TPMS inverse surface structure, respectively, which effectively increases the heat exchange area of ​​the heat exchanger and improves the overall heat exchange capacity of the cooling system. By utilizing the height difference of the transformer itself to arrange the evaporator and condenser, a self-driven cycle within the secondary cooling circuit is achieved, eliminating the need for additional energy and ensuring low-noise and low-consumption operation of the entire cooling system.

[0017] 4. The multi-mode cooling system can switch between multiple cooling modes under low, medium and high load conditions of the transformer by controlling the start and stop of the multi-needle-mesh ion wind heat dissipation device and the water evaporative cooling device, thereby improving the cooling system's adaptability to load changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the overall structure of an embodiment of the present invention; Figure 2 This is a schematic structural diagram of a multi-needle-net type ion wind heat dissipation device according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the self-driving principle of the secondary cooling circuit according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the tree-like fractal structure of an evaporator according to an embodiment of the present invention; Figure 5 yes Figure 4 AA cross-section of Figure 6 This is a schematic diagram of the reverse curved surface structure of the condenser TPMS according to an embodiment of the present invention; Figure 7 for Figure 6 An enlarged schematic diagram of part B; Figure 8 Schematic diagram of cooling mode switching under variable load operating conditions according to an embodiment of the present invention; Among them: 1-transformer body; 2-primary cooling circuit; 3-secondary cooling circuit; 11-sealed housing; 12-iron core; 13-winding; 21-radiator; 22-stainless steel bracket; 23-multi-needle-mesh ion wind cooling device; 31-evaporator; 32-condenser; 33-water evaporative cooling device; 231-auxiliary guide channel; 232-mesh electrode; 233-needle electrode; 234-insulating bracket; 235-slide rail; 331-receiving tray; 332-exhaust fan; 333-packing layer; 334-valve; 335-water tank. DETAILED DESCRIPTION

[0019] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings. The embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0020] Figure 1A specific embodiment of an air-liquid-cooled multi-mode cooling system for an oil-immersed transformer is presented, comprising: a transformer body 1, a primary cooling circuit 2, and a secondary cooling circuit 3. The transformer body 1 includes a sealed casing 11 and an iron core 12, windings 13, and immersion coolant therein. The iron core 12 and windings 13 are immersed in the immersion coolant, and the sensible heat of the coolant is used to carry away the heat generated during transformer operation. Three cooling modes are proposed based on the different operating conditions of the transformer. When the transformer is operating under low load, the coolant is cooled by the radiator 21 in the primary cooling circuit 2 and the evaporator 31 and condenser 32 in the secondary cooling circuit 3. The radiator 21 uses natural air convection as the main heat exchange method, while the evaporator 31 and condenser 32 achieve self-driving of the cooling circuit by relying on the density difference caused by the phase change heat transfer of the internal refrigerant. When the transformer is operating under medium load, in addition to the above, the multi-needle-mesh ion wind heat dissipation device in the primary cooling circuit 2 is opened to achieve a transition from natural air convection to forced convection in the heat exchange mode of the radiator 21, thereby improving the comprehensive heat dissipation capacity of the cooling system. When the transformer is operating under high load, the valve 334 in the secondary cooling system 3 is opened, and water is used as the cooling source for the condenser 32, achieving a transition from air cooling to water cooling in the secondary cooling circuit, further improving the heat transfer coefficient and ensuring that the refrigerant in the secondary cooling circuit quickly condenses into liquid and falls back to the evaporator 31, continuously removing heat from the immersion coolant, thereby maintaining stable operation of the transformer.

[0021] The primary cooling circuit 2 includes a radiator 21 , a stainless steel bracket 22 and a multi-needle-net type ion wind heat dissipation device 23 .

[0022] Figure 2This is a schematic diagram of a multi-needle-mesh ionized air cooling device. The multi-needle-mesh ionized air cooling device 23 is positioned on the midline of two adjacent main flow channel tubes of the radiator 21 using stainless steel brackets 22 welded to the sealed housing and slide rails. The multi-needle-mesh ionized air cooling device 23 comprises needle electrodes 233, mesh electrodes 232, and auxiliary flow channels 231. The bottom of the auxiliary flow channels 231 is kept at least 10 cm from the top of the fins of the radiator 21 to ensure that the air reaching the fins is fully developed. The mesh electrode 232 is welded to the top of the auxiliary guide channel 231 and is provided with an insulating bracket 234 on the outside. The insulating bracket 234 is connected to the stainless steel bracket 22 through a slide rail 235, which can adjust the distance between the air outlet and the fins of the radiator 21; the needle electrode 233 is also provided with an insulating bracket 234 on the outside and is connected to the stainless steel bracket 22 through a slide rail 235. By changing the position of the slide rail 235 connected to the needle electrode 233, the distance between the needle electrode 233 and the mesh electrode 232 can be flexibly changed, thereby dynamically adjusting the ion wind speed. Both the needle electrode 233 and the mesh electrode 232 are made of stainless steel. Precision machining is used to create a crown structure with several needle tips on a stainless steel ring. The ring dimensions are aligned with the spacing between two adjacent main pipes in the radiator 21 to effectively utilize the layout space and optimize the ion wind's heat dissipation. The outlet radius of the auxiliary flow channel 231 is 1 / 5 to 1 / 2 the radius of the ring containing the needle electrode 233 to maximize the outlet wind speed. The number of needle electrodes is approximately 1 / 150 to 1 / 100 of the voltage provided by the transformer body to fully utilize the transformer's voltage and ensure high ion wind speeds. Each needle tip is a discharge needle. The entire crown-shaped ring serves as the cathode, supplied with negative high-voltage direct current by the transformer body 1. The mesh electrode 232 serves as the anode and is grounded. The auxiliary flow channel 231 is a tapered tube structure, with the channel terminus located at the top of the radiator 21. According to aerodynamics, when gas flows through a tapered tube, the cross-sectional area of ​​the tube decreases, resulting in a decrease in pressure while maintaining constant flow rate, thereby increasing the gas flow rate. This can further increase the ion wind speed and the convective heat transfer coefficient, thereby significantly improving the heat transfer capacity of the radiator 21. Furthermore, ion wind does not require a fan and meets the requirements of a high-efficiency and low-noise transformer cooling system. When the transformer is continuously operating at a low load, the power supply circuit from the transformer to the ion wind heat sink can be periodically connected to open the ion wind heat sink 23 and remove dust from the surface of the radiator 21. This can effectively reduce the thermal resistance of dirt, improve the heat transfer coefficient, and ensure efficient heat transfer of the cooling system.

[0023] Figure 3This is a schematic diagram of the self-driving principle of the secondary cooling circuit in an embodiment of the present invention. The secondary cooling circuit 3 includes evaporators 31 on the left and right sides of the transformer body 1, a condenser 32 at the top, a water evaporative cooling device 33, and related connecting pipes. After the refrigerant absorbs heat from the immersion coolant in the evaporator 31 and vaporizes, it flows spontaneously to the condenser 32 at the top under the influence of gravity. After condensation in the condenser 32, it falls back into the evaporator 31, achieving a self-driving cycle. The water evaporative cooling device 33 includes a water tank 335 at the top, a valve 334, a packing layer 333, an exhaust fan 332, and a receiving tray 331. The water tank 335, valve 334, and packing layer 333 are arranged in sequence above the condenser 32 from top to bottom. The exhaust fan 332 and receiving tray 331 are located below the condenser 32. Cooling water is obtained from the water tank 335 above the condenser 32. When the transformer load increases, the valve 334 opens to provide cooling water. In addition, exhaust fan 332 is activated to accelerate the downward flow of water droplets, and the micro-pores of packing layer 333 are used as spray nozzles, creating a water evaporative cooling mode. Exhaust fan 334 is powered by the transformer itself. The entire circuit fully utilizes the system characteristics and the density difference caused by phase change to achieve self-circulation of the working fluid without requiring additional power consumption, greatly improving the economic efficiency of the cooling system.

[0024] Figure 4 、 Figure 5 They are respectively the tree-like fractal structures of the evaporator according to the embodiment of the present invention; Figure 6 、 Figure 7 Schematic diagram of the condenser TPMS reverse curved surface structure, where the evaporator 31 is a shell and tube heat exchanger and the condenser 32 is a plate-fin heat exchanger. Inspired by the growth of plants in nature and the biological structure of sea urchin skeletal plates, respectively, the evaporator 31 is given a tree-like fractal structure, which can achieve a larger heat exchange area within a limited space. The fluid can continuously change direction and speed during the flow process, enhancing the heat transfer effect while reducing flow resistance. The surface of the heat exchange plate of the condenser 32 is processed with TPMS reverse curved surface to further increase the fluid heat exchange area. At the same time, it ensures that the fluid flows in an orderly and complex manner between the plates, thereby enhancing the heat exchange time of the hot and cold fluids and effectively improving the heat exchange efficiency.

[0025] Figure 8 This is a schematic diagram of cooling mode switching under variable load operating conditions in an embodiment of the present invention. According to the actual operating load of the transformer, the embodiment of the present invention proposes three different cooling modes, namely, oil-immersed self-cooling and self-driven secondary cooling mode under low load operation, oil-immersed forced air cooling and self-driven secondary cooling mode under medium load operation, and oil-immersed forced air cooling and self-driven mixed air / liquid cooling secondary cooling mode under high load operation, which effectively improves the adaptability of the transformer cooling system to load changes.

[0026] The working fluid of the evaporator and condenser is refrigerant R134a, and the secondary fluid cooling medium of the condenser is water.

[0027] The packing layer should be made of low-cost plastic packing such as PP, PVDF orifice plate corrugated packing, etc.

[0028] The immersion coolant is a hydrofluoric saturated compound, a hydrofluoric unsaturated compound, a perfluorinated saturated compound, a perfluorinated unsaturated compound or mineral oil.

[0029] The above specific implementation methods are only for illustrating the technical concept and structural features of the present invention, and the purpose is to enable relevant persons familiar with this technology to implement them accordingly. However, the above content does not limit the scope of protection of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A multi-mode cooling system, characterized in that: include: The transformer body (1) comprises a sealed housing (11) and an iron core (12), a winding (13) and an immersion coolant therein, wherein the iron core (12) and the winding (13) are immersed in the immersion coolant; A primary cooling circuit (2) includes a radiator (21) and a multi-needle-mesh type ion wind heat dissipation device (23); the radiator (21) is located at the front and rear sides of the transformer body (1); the multi-needle-mesh type ion wind heat dissipation device (23) uses the negative high-voltage direct current provided by the transformer body (1) as a power source to generate ion wind that blows toward the radiator (21); A secondary cooling circuit (3) includes an evaporator (31), a condenser (32), and a water evaporation cooling device (33); the evaporator (31) is located on the left and right sides of the transformer body (1); the condenser (32) and the water evaporation cooling device (33) are located above the transformer body (1); the evaporator (31) and the condenser (32) are connected via a pipe; after the refrigerant absorbs the heat of the immersion cooling liquid in the evaporator (31) and vaporizes, it flows spontaneously to the condenser (32) above under the influence of gravity, and then falls back into the evaporator (31) after being condensed in the condenser (32), thereby realizing a self-driven cycle; The water evaporative cooling device (33) comprises a water tank (335), a valve (334), a packing layer (333), an exhaust fan (332) and a receiving plate (331). The water tank (335), the valve (334) and the packing layer (333) are sequentially distributed above the condenser (32) from top to bottom. The exhaust fan (332) and the receiving plate (331) are located below the condenser (32). When the transformer load increases, the valve (334) is opened to provide cooling water, and the exhaust fan (332) is turned on to accelerate the flow of water droplets, so that the micro-capillary pores of the packing layer (333) are used as spraying ports to form water evaporative cooling.

2. The multi-mode cooling system according to claim 1, wherein: The multi-needle-mesh ion wind heat dissipation device (23) comprises an auxiliary flow guide channel (231), a mesh electrode (232), a needle electrode (233), an insulating bracket (234) and a slide rail (235); the mesh electrode (232) is welded to the top of the auxiliary flow guide channel (231), and the needle electrode (233) is located above the mesh electrode (232); an insulating bracket (234) with a slide rail (235) is provided outside the needle electrode (233) and the mesh electrode (232); the transformer body (1) provides negative high-voltage direct current to the needle electrode (233), the mesh electrode (232) is grounded, the auxiliary flow guide channel (231) is a tapered tube structure, and the end of the channel is located at the top of the radiator (21).

3. The multi-mode cooling system according to claim 2, wherein: The multi-needle-net type ion wind heat dissipation device (23) is placed on the midline of two adjacent main flow channel pipes of the radiator (21).

4. The multi-mode cooling system according to claim 2, wherein: The primary cooling circuit (2) further comprises a stainless steel guide rail support (22); the insulating support (234) of the needle electrode (233) and the mesh electrode (232) can slide on the stainless steel guide rail support (22) via the slide rail (235).

5. The multi-mode cooling system according to any one of claims 1 to 4, characterized in that: The evaporator (31) is a shell and tube heat exchanger, the interior of which has a tree-like fractal structure to enhance heat exchange.

6. The multi-mode cooling system according to any one of claims 1 to 4, characterized in that: The variable condenser (32) is a plate-fin heat exchanger, and the surface of the plate-fin heat exchanger adopts a TPMS reverse curved surface structure.

7. The multi-mode cooling system according to any one of claims 1 to 4, characterized in that: The working fluid of the evaporator (31) and the condenser (32) is the refrigerant R134a, and the secondary fluid cooling medium of the condenser is water.

8. The multi-mode cooling system according to claim 1, wherein: The filler layer (332) is made of plastic filler.

9. The multi-mode cooling system according to claim 1, wherein: The immersion cooling liquid is a hydrofluoric saturated compound, a hydrofluoric unsaturated compound, a perfluorinated saturated compound, a perfluorinated unsaturated compound or mineral oil.

10. The multi-mode cooling system according to claim 1, wherein: The primary cooling circuit (2) is connected to a multi-needle-mesh ion wind heat dissipation device (23) when the transformer is operating at medium load, and the valve (334) of the water evaporation cooling device (33) in the secondary cooling circuit (3) is adjusted when the transformer is operating at high load to provide cooling water for the condenser (32).

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