A multi-mode cooling system

Abstract

This invention discloses a multi-mode cooling system, including a transformer body, a primary cooling circuit, and a secondary cooling circuit. The transformer body includes a sealed outer shell and its internal iron core, windings, and submerged coolant. The primary cooling circuit includes radiators on the front and rear sides of the transformer body and a multi-needle-mesh ion air cooling device. The secondary cooling circuit includes an evaporator, a condenser, a water evaporation cooling device, and related connecting pipes. The water evaporation cooling device includes a top water tank, valves, a packing layer, an exhaust fan, and a receiving plate. When the transformer load increases, the valves are opened to supply cooling water, and the micro-capillaries of the packing layer form spray nozzles for water evaporation cooling. The exhaust fan is activated to accelerate the downward flow of water. This invention selects the cooling method according to the transformer's operating conditions. The entire device requires no additional driving force, and the refrigerant liquid can achieve self-driven circulation, reducing energy consumption while ensuring stable transformer operation.

Description

Technical Field

[0001] This invention relates to a cooling system for oil-immersed transformers. Background Technology

[0002] With the acceleration of urbanization, power systems are developing towards higher voltage, larger capacity, and longer-distance power transmission, leading to the emergence of numerous high-voltage, ultra-high-voltage, and extra-high-voltage transformers. However, during operation, transformers generate significant heat due to resistance losses, hysteresis losses, and eddy current losses in their windings and cores. Given the increasingly smaller external surface area to volume ratio, natural heat dissipation alone is far from sufficient. This has driven the development of transformer cooling systems towards compactness, high efficiency, and low noise. Therefore, it is necessary to construct efficient and low-noise cooling systems to meet the reliable heat dissipation requirements of transformers.

[0003] Currently, air cooling is the most common and widely used heat dissipation method for oil-immersed transformers, including oil-immersed air cooling and forced oil circulation air cooling. However, both of these air cooling modes are limited by the ambient temperature. In particular, the oil-immersed air cooling mode may cause the transformer oil temperature to be too high when operating in high temperatures in summer, which may pose certain electrical hazards. While the forced oil circulation air cooling mode can achieve forced air convection and improve the system's 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] Furthermore, forced oil circulation water cooling is commonly used in large-capacity and ultra-large-capacity oil-immersed transformers, which enhances the heat dissipation performance of the transformer cooling system to some extent. However, these methods suffer from uneven radiator distribution, easily leading to localized heat accumulation. They also only achieve heat dissipation under constant load and cannot adjust the cooling system's capacity according to the actual operating conditions of the transformer under varying loads, resulting in large fluctuations in transformer oil temperature and wasted cooling resources. In summary, to meet the heat dissipation and cooling requirements of oil-immersed transformers under varying operating conditions, there is an urgent need to develop a dynamic, efficient, and low-noise cooling technology. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to propose a multi-mode cooling system for immersion transformers that significantly improves the energy efficiency of the cooling system and matches the load.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A multi-mode cooling system, comprising:

[0008] The transformer body includes a sealed outer casing and an internal core and winding immersed in a cooling liquid. The core and winding are immersed in the cooling liquid.

[0009] A primary cooling circuit includes a radiator and a multi-needle-mesh ion wind cooling device; the radiator is located on the front and rear sides of the transformer body; the multi-needle-mesh ion wind cooling device uses the negative high voltage DC power provided by the transformer body as a power source to generate ion wind that blows towards the radiator;

[0010] The secondary cooling circuit includes an evaporator, a condenser, and a water evaporation cooling device. The evaporator is located on the left and right sides of the transformer body. The condenser and the water evaporation cooling device are located above the transformer body. The evaporator and condenser are connected by pipes. After the refrigerant absorbs heat from the submerged coolant in the evaporator and vaporizes, it flows spontaneously upwards to the condenser due to gravity. After condensation in the condenser, it falls back into the evaporator, achieving a self-driven cycle. The water evaporation cooling device includes a water tank, valves, a packing layer, an exhaust fan, and a receiving plate. The water tank, valves, and packing layer are distributed sequentially from top to bottom above the condenser. The exhaust fan and the receiving plate are located below the condenser. When the transformer load increases, the valves are opened to provide cooling water, and the exhaust fan is turned on to accelerate the flow of water droplets. The micro-capillaries of the packing layer serve as spray nozzles to form water evaporation cooling.

[0011] The multi-needle-mesh ion wind heat dissipation device includes an auxiliary flow 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 flow channel, and the needle electrode is located above the mesh electrode. An insulating bracket with a slide rail is provided on the outside of both the needle electrode and the mesh electrode. The transformer body provides negative high-voltage DC power to the needle electrode, and the mesh electrode is grounded. The auxiliary flow channel has a tapered tube structure, and the end of the channel is located at the top of the heat sink.

[0012] The multi-needle-mesh ion wind cooling device utilizes the small radius of curvature at the needle tip of the needle electrode to obtain a high electric field strength under high voltage, thereby ionizing neutral molecules between the electrodes and generating gas flow from the electrode with the small radius of curvature to the electrode with the large radius of curvature, i.e., the ion wind. Both the needle electrode and the mesh electrode are made of stainless steel, and several needle tips are precision-machined onto a stainless steel ring, ensuring that all needle tips are on 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, supplied with negative high-voltage direct current through the transformer body. The mesh electrode is the anode and is grounded, ensuring that the needle tip plane of the needle electrode is parallel to the mesh electrode plane. The auxiliary flow channel is a tapered tube structure, with the end of the channel located at the top of the heat sink. According to the continuity equation and Bernoulli's equation, this structure can further increase the ion wind velocity.

[0013] The evaporators on both sides of the transformer body are shell-and-tube heat exchangers. Inspired by the typical tree-like structure of plants in nature, the heat exchangers are designed with a tree-like fractal structure, which can achieve a large heat exchange area within a limited space. This allows the fluid to continuously change direction and velocity during flow, enhancing the heat exchange effect while reducing flow resistance. The condenser at the top of the transformer body is a plate-fin heat exchanger. Inspired by the skeletal structure of sea urchins, the surface of the heat exchange plates is processed with TPMS inverted curved surfaces to further increase the fluid heat exchange area. At the same time, while ensuring orderly fluid flow between the plates, the increased complexity effectively improves heat exchange efficiency.

[0014] When the transformer is running at low load, the primary cooling circuit relies solely on the natural convection of the radiator in the primary cooling circuit 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, i.e., forced convection heat exchange is used in the primary cooling circuit. When the transformer is running at high load, the valve of the water evaporation cooling device in the secondary cooling circuit is opened to provide cooling water for the condenser.

[0015] The working fluid in the evaporator and condenser is refrigerant R134a, and the secondary fluid cooling medium in the condenser is water.

[0016] The filler layer is made of low-cost plastic fillers such as PP or PVDF perforated plate corrugated fillers.

[0017] The immersion coolant is a hydrofluoric acid saturated compound, a hydrofluoric acid unsaturated compound, a perfluorinated saturated compound, a perfluorinated unsaturated compound, or a mineral oil.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. This invention proposes a multi-mode air-liquid cooling system for oil-immersed transformers. By arranging two radiators coupled with ion winds around the transformer, two evaporators, and a wind / liquid-cooled condenser on top, a composite cooling structure integrating multiple heat exchange mechanisms is constructed. This achieves efficient energy transfer and improves the heat dissipation performance of the transformer under varying operating conditions. An ion wind generator without mechanical rotating parts is introduced and directly driven by the high voltage characteristics generated by the transformer body to form an ion wind field, replacing the traditional high-speed fan, greatly reducing operating noise and achieving low-noise auxiliary heat exchange on the radiator surface. The refrigerant working fluid is self-driven to circulate using the gravitational potential difference between the evaporator and condenser, eliminating the need for an external pump to drive the circulation and solving the high energy consumption problem of fans and pumps in traditional cooling schemes, achieving low-energy operation of the two-phase heat exchange loop. Furthermore, the system achieves dynamic and precise matching and adaptive response between cooling capacity and heat dissipation requirements through a multi-mode switching strategy of oil-immersed air cooling, liquid cooling, and forced air cooling, effectively avoiding overcooling or cooling lag, and is particularly suitable for long-term stable operation under complex operating conditions and varying loads. This air-liquid cooling multi-mode cooling system not only achieves compact integration in structure, but also demonstrates comprehensive advantages such as low noise, high energy efficiency, and strong load adaptability, providing a reliable solution for the green, efficient, and intelligent thermal management of oil-immersed transformers.

[0020] 2. Utilizing the high-voltage characteristics of the transformer itself, an ion wind cooling device is constructed. High voltage and multi-needle-mesh electrodes generate a high-speed ion wind, and a tapered tube structure is built as an auxiliary flow channel to further increase the ion wind velocity and enhance the heat exchange capacity of the radiator. In addition, the ion wind device can be periodically activated to clean the radiator surface, ensuring efficient operation.

[0021] 3. The evaporator and condenser adopt tree-like fractal and TPMS inverted curved surface structures respectively, which can effectively increase the heat exchange area of ​​the heat exchangers and improve the overall heat exchange capacity of the cooling system. Utilizing the height difference of the transformer itself to arrange the evaporator and condenser enables self-driven circulation within the secondary cooling loop, requiring no additional energy supply and achieving low-noise and low-consumption operation of the entire cooling system.

[0022] 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 air heat dissipation device and the water evaporation cooling device, thereby improving the adaptability of the cooling system to load changes. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the present invention;

[0024] Figure 2This is a schematic diagram of the multi-needle-mesh ion wind heat dissipation device according to an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of the self-driving principle of the secondary cooling circuit in an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the tree-like fractal structure of the evaporator according to an embodiment of the present invention;

[0027] Figure 5 yes Figure 4 AA cross-section view;

[0028] Figure 6 This is a schematic diagram of the TPMS inverted curved surface structure of the condenser in an embodiment of the present invention;

[0029] Figure 7 for Figure 6 Enlarged schematic diagram of part B;

[0030] Figure 8 This is a schematic diagram of cooling mode switching under variable load operation conditions according to an embodiment of the present invention;

[0031] Wherein: 1-Transformer body; 2-Primary cooling circuit; 3-Secondary cooling circuit; 11-Sealed outer shell; 12-Iron core; 13-Windings; 21-Radiator; 22-Stainless steel bracket; 23-Multi-needle-mesh ion air cooling device; 31-Evaporator; 32-Condenser; 33-Water evaporation cooling device; 231-Auxiliary flow channel; 232-Mesh electrode; 233-Needle electrode; 234-Insulating bracket; 235-Slide rail; 331-Receiving plate; 332-Exhaust fan; 333-Packing layer; 334-Valve; 335-Water tank. Detailed Implementation

[0032] To enhance understanding of the present invention, we will now describe it in further detail with reference to the accompanying drawings. These embodiments are for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0033] Figure 1A specific embodiment of an oil-immersed transformer air-liquid cooling multi-mode cooling system is shown, including: transformer body 1, primary cooling circuit 2 and secondary cooling circuit 3, wherein the transformer body 1 includes a sealed shell 11 and an iron core 12, windings 13 and immersion coolant inside it, the iron core 12 and windings 13 are immersed in the immersion coolant, and the heat generated by the transformer during operation is carried away by the sensible heat of the coolant. Three cooling modes are provided according to different operating conditions of the transformer. When the transformer is running at low load, the radiator 21 in the primary cooling circuit 2 and the evaporator 31 and condenser 32 in the secondary cooling circuit 3 are used to cool the coolant. The radiator 21 mainly uses natural air convection as the heat exchange method, while the evaporator 31 and condenser 32 rely on the density difference caused by the phase change heat of the internal refrigerant to achieve self-drive of the cooling circuit. When the transformer is running at medium load, the multi-needle-mesh ion air heat dissipation device in the primary cooling circuit 2 is opened to realize the transformation of the heat exchange method in the radiator 21 from natural air convection to forced convection mode, which improves the overall heat dissipation capacity of the cooling system. When the transformer is running at high load, the valve 334 in the secondary cooling system 3 is opened to use water as the cold source of the condenser 32, realizing the transformation of the secondary cooling circuit from air cooling to water cooling, further improving the heat transfer coefficient, ensuring that the refrigerant inside quickly condenses into liquid and falls back to the evaporator 31, continuously removing the heat of the submerged coolant, thereby maintaining the stable operation of the transformer.

[0034] The primary cooling circuit 2 includes a radiator 21, a stainless steel bracket 22, and a multi-needle-mesh ion air cooling device 23.

[0035] Figure 2This is a schematic diagram of a multi-needle-mesh ion air cooling device. The multi-needle-mesh ion air cooling device 23 is placed on the midline of two adjacent main flow channels of the radiator 21 via a stainless steel bracket 22 welded to the sealed outer shell and a slide rail. The multi-needle-mesh ion air cooling device 23 includes needle electrodes 233, mesh electrodes 232, and auxiliary flow channels 231. The bottom of the auxiliary flow channels 231 is kept at a distance of more than 10 cm from the top of the fins of the radiator 21 to ensure that the air reaching the fins is in a fully developed stage. The mesh electrode 232 is welded to the top of the auxiliary flow 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 the slide rail 235, which can adjust the distance between the air outlet and the fins of the heat sink 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 the 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. A crown structure is formed by precision machining of several needle tips on a stainless steel ring. The size of the ring matches the spacing between two adjacent main pipes in the radiator 21 to effectively utilize the arrangement space and optimize the ion wind cooling effect. The outlet radius of the auxiliary flow channel 231 is 1 / 5 to 1 / 2 of the radius of the ring where the needle electrode 233 is located 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 voltage supplied by the transformer body and ensure that the obtained ion wind is at a high wind speed. Each needle tip is a discharge needle, and the entire crown-shaped ring is the cathode, which is supplied with negative high-voltage DC power by the transformer body 1. The mesh electrode 232 is the anode and is grounded. The auxiliary flow channel 231 is a tapered tube structure, with the end of the channel located at the top of the radiator 21. According to aerodynamics, when gas flows through the tapered tube, the pressure decreases due to the reduced cross-sectional area of ​​the tube, resulting in an increase in gas velocity while maintaining the same flow rate. This allows for further increases in ion air velocity and convective heat transfer coefficient, thereby significantly improving the heat exchange capacity of radiator 21. Furthermore, ion air eliminates the need for a fan, simultaneously meeting the high-efficiency and low-noise requirements of the transformer cooling system. When the transformer operates under continuous low load, the power supply circuit to the ion air cooling device can be periodically switched on to open the ion air cooling device 23, removing accumulated dust from the surface of radiator 21. This effectively reduces the thermal resistance of the fouling, improves the heat transfer coefficient, and ensures efficient heat exchange in the cooling system.

[0036] 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 both sides of the transformer body 1, a condenser 32 at the top, a water evaporation cooling device 33, and related connecting pipes. After the refrigerant absorbs heat from the submerged coolant in the evaporator 31 and vaporizes, it flows spontaneously to the condenser 32 at the top under the influence of gravity. After being condensed in the condenser 32, it falls back into the evaporator 31, thus achieving a self-driving cycle. The water evaporation 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 plate 331. The water tank 335, valve 334, and packing layer 333 are distributed sequentially from top to bottom above the condenser 32, while the exhaust fan 332 and receiving plate 331 are located below the condenser 32. Cooling water is obtained through the water tank 335 at the top of the condenser 32. When the transformer load increases, the valve 334 is opened to provide cooling water. In addition, the exhaust fan 332 is activated to accelerate the downward flow of water droplets, and the microcapillaries of the packing layer 333 are used as spray nozzles to form a water evaporation cooling mode. The exhaust fan 334 is powered by the transformer itself. The entire circuit makes full use of the system characteristics and the density difference caused by the phase change to achieve self-circulation of the working fluid without additional power consumption, which greatly improves the economy of the cooling system.

[0037] Figure 4 , Figure 5 These are respectively the tree-like fractal structures of the evaporator in embodiments of the present invention; Figure 6 , Figure 7 A schematic diagram of the TPMS inverted curved surface structure of the condenser is shown. 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 skeletal structure of sea urchins, the evaporator 31 is treated with a tree-like fractal structure, which can achieve a large heat exchange area in a limited space. This allows the fluid to continuously change direction and velocity during flow, enhancing the heat exchange effect while reducing flow resistance. Furthermore, the surface of the heat exchange plate of the condenser 32 is processed with TPMS inverted curved surface to further increase the fluid heat exchange area. At the same time, it ensures that the fluid flows in an orderly manner between the plates while making it more complex, thereby increasing the heat exchange time between hot and cold fluids and effectively improving the heat exchange efficiency.

[0038] Figure 8 This is a schematic diagram of cooling mode switching under variable load operation conditions in an embodiment of the present invention. According to the different actual operating loads of the transformer, the present invention proposes three different cooling modes: 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.

[0039] The working fluid in both the evaporator and condenser is refrigerant R134a, and the secondary fluid cooling medium in the condenser is water.

[0040] For the packing layer, choose low-cost plastic packings such as PP or PVDF perforated plate corrugated packings.

[0041] The immersion coolant is a hydrofluoric acid saturated compound, a hydrofluoric acid unsaturated compound, a perfluorinated saturated compound, a perfluorinated unsaturated compound, or a mineral oil.

[0042] The above specific embodiments are only for illustrating the technical concept and structural features of the present invention, and are intended to enable those skilled in the art to implement them. However, the above content does not limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit and essence of the present invention should fall within the scope of protection of the present invention.

Claims

1. A multi-mode cooling system, characterized by: include: The transformer body (1) includes a sealed outer shell (11) and its internal iron core (12), windings (13) and immersion coolant, wherein the iron core (12) and windings (13) are immersed in the immersion coolant; A primary cooling circuit (2) includes a radiator (21) and a multi-needle-mesh ion wind cooling device (23); the radiator (21) is located on the front and rear sides of the transformer body (1); the multi-needle-mesh ion wind cooling device (23) uses the negative high voltage DC power provided by the transformer body (1) as a power source to generate ion wind that blows toward the radiator (21). The 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 by pipes; after the refrigerant absorbs the heat of the submerged coolant in the evaporator (31) and vaporizes, it flows spontaneously to the condenser (32) above due to gravity, and after being condensed in the condenser (32), it falls back into the evaporator (31), thus realizing a self-driven cycle; The water evaporation cooling device (33) includes a water tank (335), a valve (334), a packing layer (333), an exhaust fan (332), and a receiving plate (331). The water tank (335), valve (334), and packing layer (333) are distributed from top to bottom above the condenser (32), and the exhaust fan (332) and 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. The microcapillaries of the packing layer (333) serve as spray nozzles to form water evaporation cooling. The multi-needle-mesh ion wind heat dissipation device (23) includes an auxiliary flow 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 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 on the outside of both the needle electrode (233) and the mesh electrode (232). The transformer body (1) provides negative high voltage DC power to the needle electrode (233), the mesh electrode (232) is grounded, and the auxiliary flow channel (231) is a tapered tube structure with the end of the channel located on the top of the heat sink (21). When the transformer is under load, the primary cooling circuit (2) is connected to the multi-needle-mesh ion wind heat dissipation device (23). When the transformer is under high load, the valve (334) of the water evaporation cooling device (33) in the secondary cooling circuit (3) is adjusted to provide cooling water for the condenser (32).

2. The multi-mode cooling system according to claim 1, characterized in that: The multi-needle-mesh ion wind heat dissipation device (23) is placed on the midline of the two main channel pipes adjacent to the heat sink (21).

3. The multi-mode cooling system according to claim 1, characterized in that: The primary cooling circuit (2) also includes a stainless steel guide rail bracket (22); the insulating bracket (234) of the needle electrode (233) and the mesh electrode (232) slides on the stainless steel guide rail bracket (22) via the slide rail (235).

4. The multi-mode cooling system according to any one of claims 1-3, characterized in that: The evaporator (31) is a shell-and-tube heat exchanger with a tree-like fractal structure inside to enhance heat transfer.

5. The multi-mode cooling system according to any one of claims 1-3, characterized in that: The condenser (32) is a plate-fin heat exchanger, and the surface of the plate-fin heat exchanger adopts a TPMS inverted curved surface structure.

6. The multi-mode cooling system according to any one of claims 1-3, characterized in that: The working fluid of the evaporator (31) and condenser (32) is refrigerant R134a, and the cooling medium of the secondary fluid of the condenser is water.

7. The multi-mode cooling system according to claim 1, characterized in that: The filler layer (333) is made of plastic filler.

8. The multi-mode cooling system according to claim 1, characterized in that: The immersion coolant is a hydrofluoric acid saturated compound, a hydrofluoric acid unsaturated compound, a perfluorinated saturated compound, a perfluorinated unsaturated compound, or a mineral oil.

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