Evaporative heat dissipation device and control method thereof

Abstract

The application discloses an evaporative heat dissipation device and a control method thereof. The device comprises a water distribution device which distributes the cooling liquid to the outer surface of the lower serpentine heat dissipation assembly to form a liquid film. The serpentine heat dissipation assembly comprises a plurality of heat dissipation pipe sections arranged from top to bottom, and a communication part which communicates each heat dissipation pipe section in sequence. The device further comprises a hydrophilic flow guide plate arranged between two adjacent heat dissipation pipe sections. The cooling liquid flowing down from the outer surface of the upper heat dissipation pipe section flows to the outer surface of the lower heat dissipation pipe section after being guided by the hydrophilic flow guide plate. The hydrophilic flow guide plate and the super-hydrophilic surface work together to promote the rapid spreading of the cooling liquid into a uniform thin liquid film through capillary action, significantly increasing the gas-liquid contact area, solving the problem of uneven distribution of liquid film and easy local dryness in the traditional way, and greatly improving the heat exchange efficiency.

Description

Technical Field

[0001] This invention relates to the field of heat dissipation and cooling technology, and in particular to an evaporative heat dissipation device and its control method. Background Technology

[0002] Evaporative cooling technology achieves efficient cooling through the principle of water evaporation and heat absorption, and is widely used in various applications requiring heat dissipation. Conventional plate-tube evaporative cooling devices typically include a heat exchanger, a spray system, a fan, and a water collection tank. Cooling water forms a film on the heat exchanger surface through the spray system, absorbing heat, while the fan drives airflow, accelerating the evaporation of the water film and carrying away heat. However, existing technologies have several drawbacks: Uneven liquid film distribution: Due to the cohesive forces of water molecules, cooling water is difficult to spread evenly on the surface of the heat exchange tubes, easily forming water droplets or localized thick films, resulting in a reduced effective heat exchange area and potentially causing localized drying and heat accumulation, thus reducing heat dissipation efficiency. Decreased heat dissipation efficiency: If the water film formed by the spray fails to evaporate and dissipate heat in time, the cooling water temperature will gradually rise during circulation, thus limiting its subsequent heat exchange capacity. Poor adaptability and difficult maintenance: Other cooling technologies, such as microchannel radiators, although having a large specific surface area, require extremely high processing precision and water quality, are prone to channel blockage, have high maintenance costs, and are difficult to dynamically adjust according to non-uniform heat loads. Therefore, there is an urgent need for an evaporative cooling device that can achieve uniform liquid film distribution, efficient evaporative heat dissipation, and easy maintenance.

[0003] A patent document published in China, titled "An Evaporation Device for a Heat Pipe Radiator," with publication number CN113758062A and publication date of 2021-12-07, includes a heat dissipation box. A condensate storage tank is fixedly connected to the lower end of the heat dissipation box. A driving water pump is installed inside one side of the condensate storage tank. A spray pipe is fixedly connected to the output end of the driving water pump. Multiple spray guides are evenly connected to the front side of the upper end of the spray pipe, and multiple spray heads are installed at the ends of the spray guides. The spray pipe extends through the condensate storage tank to the upper part of the heat dissipation box, and the spray guide at the front end of the spray pipe penetrates the upper side wall of the heat dissipation box. A fan is fixedly connected to the center of the upper side of the heat dissipation box, and circulation pipes are fixedly connected to both sides of the heat dissipation box. This technology solves the problem that the gaseous condensate after heat absorption cannot continuously participate in the circulating cooling process as it is discharged with the airflow. However, this technology still has the defects of conventional plate-tube evaporative cooling devices. The cooling water is difficult to spread evenly on the surface of the heat exchange tube section, easily forming local dryness or thick films, thereby reducing the heat exchange area and lowering the heat dissipation efficiency. Summary of the Invention

[0004] The present invention aims to overcome the problems in the prior art where the cooling water sprayed by the plate-tube evaporative heat dissipation device is difficult to spread evenly on the surface of the heat exchange tube section, easily forming local dryness or local thick film, thereby reducing the heat exchange area and reducing the heat dissipation efficiency, as well as the problems of the high requirements for processing precision and water quality when using microchannel radiator technology, which easily clogs the flow channel and increases maintenance costs. The present invention provides an evaporative heat dissipation device and its control method.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: An evaporative heat dissipation device includes a water distribution device that distributes coolant to the outer surface of a lower serpentine heat dissipation component to form a liquid film. The serpentine heat dissipation assembly includes several heat dissipation pipe segments arranged from top to bottom, and a connecting part that connects each heat dissipation pipe segment in sequence; it also includes a hydrophilic guide plate disposed between two adjacent heat dissipation pipe segments, so that the coolant flowing down from the outer surface of the upper heat dissipation pipe segment flows to the outer surface of the lower heat dissipation pipe segment after being guided by the hydrophilic guide plate.

[0006] This invention constructs a core cascaded heat dissipation architecture for an evaporative heat dissipation device (heat dissipation pipe section - hydrophilic guide plate - heat dissipation pipe section). The serpentine heat dissipation component ensures that the fluid to be cooled has sufficient flow and time for heat exchange within the heat dissipation pipes of the device. Furthermore, this invention embeds a hydrophilic guide plate into the traditional pipe-to-pipe vertical heat dissipation path, altering the flow pattern and path of the coolant flowing across the outer surface of the serpentine heat dissipation component. Instead of potentially discontinuous dripping or concentrated flow, the coolant is first redistributed and spread on the hydrophilic guide plate before being evenly transported to the next stage of heat dissipation pipe section. The hydrophilic guide plate acts as a liquid film regeneration and intermediate cooling mechanism, thereby improving the heat dissipation efficiency of the evaporative heat sink.

[0007] Preferably, the hydrophilic guide plate includes a substrate and a guide structure disposed on the substrate; The outer surface of the substrate is coated with a hydrophilic functional layer or a micro / nano structure is constructed to form a hydrophilic interface. The flow guiding structure includes several spaced-apart flow guiding units, which adopt a branched, radial, or matrix-type flow channel layout.

[0008] Preferably, the flow guiding structure is located in the middle of the hydrophilic flow guiding plate, with the uppermost end of the flow guiding structure and the uppermost end of the hydrophilic flow guiding plate separated by a certain distance, and the lowermost end of the flow guiding structure and the lowermost end of the hydrophilic flow guiding plate separated by a certain distance.

[0009] Preferably, the flow guiding structure is positioned close to the upper heat dissipation pipe section, with the uppermost end of the flow guiding structure close to or flush with the uppermost end of the hydrophilic flow guiding plate, and the lowermost end of the flow guiding structure spaced a certain distance from the lowermost end of the hydrophilic flow guiding plate.

[0010] Preferably, the flow guiding structure is positioned close to the lower heat dissipation pipe section, with the lowest end of the flow guiding structure close to or flush with the lowest end of the hydrophilic flow guiding plate, and the highest end of the flow guiding structure spaced a certain distance from the highest end of the hydrophilic flow guiding plate.

[0011] Preferably, the water distribution device is provided with several openings or flow equalization structures at equal intervals facing the bottom of the serpentine heat dissipation component, so that the coolant drips onto the outer surface of the serpentine heat dissipation component. A water storage device is provided below the serpentine heat dissipation component to receive the coolant dripping from the serpentine heat dissipation component. The water storage device and the water distribution device are connected by a circulating pump, which transports the coolant from the water storage device to the water distribution device.

[0012] Preferably, the evaporative cooling device further includes a circulating fan, which drives outside air to enter from the lower air inlet of the evaporative cooling device, flow upward over the surface of the liquid film, and then exit from the upper air outlet of the evaporative cooling device.

[0013] A method for controlling an evaporative heat dissipation device includes: Obtain the initial thickness of the liquid film at the uppermost inlet of the hydrophilic guide plate; Track the dynamic thickness changes of the liquid film at various points as it flows downward along the hydrophilic guide plate; The minimum allowable thickness is determined by the mass flow rate of the liquid film, combined with dynamic force balance and stability analysis of the liquid film flow. The maximum allowable thickness for heat dissipation dominated by evaporation is calculated by inversely using the heat transfer coefficient threshold. If the actual liquid film thickness at any position on the hydrophilic guide plate exceeds the safe range between the minimum and maximum allowable thickness, adjust the wind speed or water flow rate to bring the liquid film thickness back to the safe range.

[0014] The control method of this invention elevates the operation and management of evaporative cooling devices to an intelligent level. By real-time monitoring of the key parameter of liquid film thickness and comparing it with the safe range (minimum allowable thickness, maximum allowable thickness) calculated based on fluid mechanics and heat transfer theories, it dynamically adjusts operating parameters, including wind speed and water flow rate. This prevents both localized drying and thermal failure caused by an excessively thin liquid film and a decrease in evaporation efficiency caused by an excessively thick liquid film. Through dynamic control, the liquid film thickness is maintained within the safe range, ensuring that the device always operates under conditions of high evaporative cooling efficiency.

[0015] Preferably, the minimum allowable thickness is proportional to the third power of the interfacial tension, inversely proportional to the third power of the coolant density, inversely proportional to the square of the third of the interfacial shear force, and proportional to the third power of the difference between 1 and the cosine of the contact angle.

[0016] Preferably, the maximum allowable thickness is obtained by dividing the thermal conductivity of the coolant by a preset heat transfer coefficient threshold.

[0017] The present invention has the following beneficial effects: 1. Highly efficient and uniform liquid film distribution: The flow guiding structure of the hydrophilic guide plate works in synergy with the superhydrophilic surface to promote the rapid spread of coolant into a uniform thin liquid film through capillary action, which significantly increases the gas-liquid contact area and solves the problems of uneven liquid film distribution and easy local drying in traditional methods, thereby greatly improving heat exchange efficiency.

[0018] 2. Effectively prevents heat accumulation: Through the cascaded heat dissipation design (heat dissipation pipe section - hydrophilic guide plate - heat dissipation pipe section), the coolant is fully cooled when flowing through the hydrophilic guide plate, avoiding the decrease in heat dissipation efficiency caused by the rise in water temperature circulation, and ensuring the continuous and efficient operation of the system.

[0019] 3. Adaptability and maintainability: The flow guide structure and hydrophilic properties can be customized according to the heat load to achieve precise zoned cooling; at the same time, compared with the complex microchannel design, the hydrophilic flow guide plate has a simpler structure, is less demanding on water quality, and reduces the risk of blockage and maintenance difficulty.

[0020] 4. Intelligent thickness control: By monitoring and adjusting the liquid film thickness in real time, it is kept in the optimal range for evaporative heat dissipation, further optimizing the performance and energy efficiency of the device and realizing dynamic intelligent thermal management. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the serpentine heat dissipation component in this invention.

[0022] Figure 2 This is a schematic diagram of a hydrophilic guide plate in this invention.

[0023] Figure 3 This is a flowchart of the control method for the evaporative heat dissipation device in this invention.

[0024] In the diagram: 1. Heat dissipation pipe section; 2. Connecting part; 3. Hydrophilic guide plate; 11. Fluid inlet; 12. Fluid outlet; 31. Guide structure. Detailed Implementation

[0025] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0026] An evaporative heat dissipation device includes a water distribution device that distributes coolant to the outer surface of a lower serpentine heat dissipation component to form a liquid film. like Figure 1The serpentine heat dissipation assembly shown includes several heat dissipation pipe segments 1 arranged from top to bottom, and a connecting part 2 that connects each heat dissipation pipe segment 1 in sequence; it also includes a hydrophilic guide plate 3 disposed between two adjacent heat dissipation pipe segments 1, and the coolant flowing down from the outer surface of the upper heat dissipation pipe segment 1 flows to the outer surface of the lower heat dissipation pipe segment 1 after being guided by the hydrophilic guide plate 3.

[0027] This invention constructs a core cascaded heat dissipation architecture for an evaporative heat dissipation device (heat dissipation pipe section - hydrophilic guide plate - heat dissipation pipe section). The serpentine heat dissipation component ensures that the fluid to be cooled has sufficient flow and time for heat exchange within the heat dissipation pipes of the device. Furthermore, this invention embeds a hydrophilic guide plate into the traditional pipe-to-pipe vertical heat dissipation path, altering the flow pattern and path of the coolant flowing across the outer surface of the serpentine heat dissipation component. Instead of potentially discontinuous dripping or concentrated flow, the coolant is first redistributed and spread on the hydrophilic guide plate before being evenly transported to the next stage of heat dissipation pipe section. The hydrophilic guide plate acts as a liquid film regeneration and intermediate cooling mechanism, thereby improving the heat dissipation efficiency of the evaporative heat sink.

[0028] Due to the cohesive forces within water molecules, the liquid film on the surface of conventional heat exchange tubes exhibits poor spreadability and uneven distribution. During heat exchange, the strong cohesive forces between water molecules prevent the liquid from spreading evenly on the pipe surface, easily forming discontinuous water droplets or localized thick films. This uneven distribution significantly reduces the effective heat exchange area and causes localized drying and heat accumulation, ultimately reducing overall heat dissipation efficiency. This invention, through the intervention of a hydrophilic guide plate, effectively overcomes the problems of liquid film contraction and uneven distribution caused by the cohesive forces of water molecules. It ensures that each stage of the heat dissipation tubes receives a uniform and continuous liquid film coverage, significantly increasing the effective heat exchange area and preventing localized drying and heat accumulation.

[0029] In conventional evaporative cooling devices, the water film formed by spraying is not evaporated and dissipated in time, easily leading to a gradual increase in the cooling water temperature and further limiting its heat exchange efficiency. When water flows over the surface of heat pipes or heat sources, it tends to fall in a concentrated vertical flow pattern, preventing subsequent heat exchange pipe sections from being adequately wetted. This flow pattern significantly reduces the contact time and area between water and air, weakening the heat dissipation effect, causing heat to accumulate continuously, and ultimately leading to a continuous rise in water temperature. In this invention, the coolant, after flowing through each stage of the cooling pipe section, does not fall directly into the water storage tank, but first evaporates and dissipates heat on the surface of the hydrophilic guide plate, effectively reducing its temperature before entering the next cycle. This design breaks through the bottleneck of heat dissipation efficiency reduction caused by the temperature rise of circulating cooling water in traditional systems.

[0030] The water distribution device has several openings or flow equalization structures at equal intervals facing the bottom of the serpentine heat dissipation component, which drip coolant onto the outer surface of the serpentine heat dissipation component; a water storage device is set below the serpentine heat dissipation component to receive the coolant dripping from the serpentine heat dissipation component; the water storage device and the water distribution device are connected by a circulation pump to transport the coolant in the water storage device to the water distribution device.

[0031] In the evaporative heat dissipation device of this invention, the structural combination of the water distribution device, the water storage device, and the circulating pump provides a complete coolant circulation system. The evenly spaced openings or uniform flow structure of the water distribution device is the first guarantee for forming an initial uniform liquid film. The uniform flow structure is committed to forming a uniform initial liquid film from the source, laying a good foundation for efficient heat exchange in subsequent stages. The circulating pump and the water storage device constitute a closed loop, reducing coolant consumption, and the circulating pump ensures a continuous supply of coolant, making the entire system operate stably and reliably.

[0032] The evaporative cooling device also includes a circulating fan, which drives outside air to enter from the lower air inlet of the evaporative cooling device, flow upward over the surface of the liquid film, and then exit from the upper air outlet of the evaporative cooling device.

[0033] In this invention, the fan creates a forced convection environment, a necessary condition for evaporative cooling. This significantly enhances the convection and evaporation between the air and the liquid film, promptly removing water vapor and preventing the retention of saturated, humid air, thereby maintaining high heat dissipation efficiency. Furthermore, the bottom-in, top-out airflow direction creates counter-current heat exchange with the liquid film under gravity, further improving heat exchange efficiency.

[0034] As a specific example, such as Figure 2 The hydrophilic guide plate 3 shown includes a substrate and a guide structure 31 disposed on the substrate; The outer surface of the substrate is coated with a hydrophilic functional layer or a micro / nano structure is constructed to form a superhydrophilic interface with a contact angle of less than 20 degrees; The flow guiding structure includes several spaced-apart flow guiding units, which adopt a branched, radial, or matrix flow channel layout.

[0035] It should be noted that the flow-guiding structure in the hydrophilic guide plate, together with the hydrophilic substrate, forms a highly efficient capillary flow combination. By automatically and rapidly guiding and uniformly dispersing the fluid, it achieves continuous and stable replenishment of coolant between pipe sections, effectively preventing localized drying. Simultaneously, based on the evaporative heat dissipation capacity achieved by the hydrophilic substrate, the coolant has fully released heat before flowing to the next heat dissipation pipe section, effectively avoiding a continuous rise in water temperature caused by heat accumulation, thereby maintaining and enhancing the system's continuous evaporative heat dissipation performance.

[0036] Specifically, the substrate of the hydrophilic guide plate can be made of metal or composite material, and its hydrophilicity can be achieved by setting a hydrophilic functional layer or constructing micro-nano structures on its surface. For example, when aluminum is used as the substrate, an anodizing process can be used to prepare an integral hydrophilic aluminum plate with a porous microstructure; its surface functional layer can be achieved through processes such as metal oxide deposition, nanoparticle composite, or chemical modification to enhance the spreadability of the liquid film and the stability of the interface.

[0037] The aluminum plate undergoes anodizing to create a porous, hydrophilic surface. Its microporous structure significantly increases the effective heat dissipation area and promotes uniform liquid film spreading, thereby greatly improving evaporation efficiency. This structure also inhibits the formation of large droplets and, while increasing the gas-liquid contact area, effectively reduces the risk of condensation and water accumulation caused by droplet aggregation, optimizing heat dissipation performance and operational stability.

[0038] Specifically, the flow-guiding structure on the hydrophilic guide plate can be fabricated using micromachining (including etching, laser processing, CNC machining, or imprinting) or chemical methods. The flow-guiding structure can be designed as multi-layered, branched, radial, or matrix structures, with the spacing between flow-guiding units controlled within 0.5 mm. The length of the flow-guiding structure along the vertical direction of the hydrophilic guide plate is approximately 20 mm to achieve directional guidance and uniform distribution of the coolant. The specific structural dimensions of the flow-guiding structure can be determined according to actual heat dissipation requirements. Both the flow-guiding structure and the surface hydrophilic properties can be customized according to the heat load requirements of different cooling zones. By flexibly adjusting its distribution density and structural parameters, precise zoning management and dynamic control of the cooling medium can be achieved.

[0039] In this embodiment, to demonstrate the difference in liquid film coverage and spreading effect between the hydrophilic guide plate of the present invention and conventional non-hydrophilic plates, four different types of plates were selected for testing. The liquid film coverage area was tested at positions A, B, and C, respectively, 5 cm, 15 cm, and 25 cm from the top of the guide plate. Type 1 is a pure aluminum plate with a contact angle of 97.66 degrees; Type 2 is an anodized aluminum plate with a contact angle of 88.71 degrees; Type 3 is a hydrophilic anodized aluminum plate with a contact angle of 16 degrees; and Type 4 is an acrylic hydrophilic aluminum plate with a contact angle of 13.5 degrees. Specific liquid film coverage area data are shown in Table 1.

[0040] Table 1. Coverage area of ​​the liquid film on hydrophilic and non-hydrophilic materials. Data shows that Model 1 and Model 2, due to their lack of hydrophilicity (contact angle close to or greater than 90 degrees), consistently have an effective wetting area of ​​less than 30%. In contrast, Model 3 and Model 4, with their superhydrophilic properties (contact angle <20 degrees), achieve a stable coverage rate of over 75%. Furthermore, when the initial water temperature is increased to 45 degrees Celsius, the liquid film coverage area of ​​Model 3 and Model 4 decreases slightly, indicating that controlling the initial water temperature is particularly important.

[0041] Therefore, to achieve optimized water distribution uniformity, the substrate must simultaneously meet two key conditions: firstly, its surface must possess superhydrophilic properties (contact angle <20 degrees); and secondly, it must be equipped with a precision flow-guiding structure with a width of less than 0.55 mm. Test data shows that at a distance of 25 cm downstream of the hydrophilic flow guide plate, this composite design can still achieve a liquid film coverage area of ​​over 85%, ensuring continuous and stable wetting.

[0042] In this embodiment, the temperature changes at different liquid film positions on the hydrophilic guide plate and the conventional non-hydrophilic plate were compared, demonstrating the superior heat dissipation effect of the hydrophilic guide plate. Three different types of plates were selected for testing, and liquid film temperatures were measured at positions A, B, and C, respectively, at distances of 5 cm, 15 cm, and 25 cm from the top of the guide plate. Type 1 was a pure aluminum plate, Type 2 was a hydrophilic anodized aluminum plate, and Type 3 was an acrylic hydrophilic aluminum plate. Specific liquid film temperature changes are shown in Tables 2-4.

[0043] Table 2 Temperature of the liquid film on a pure aluminum plate Table 3 shows the temperature of the liquid film on the hydrophilic anodized aluminum plate, with a flow guiding unit spacing of 0.5 mm. Table 4 shows the temperature of the liquid film on the acrylic hydrophilic aluminum plate, with a flow guiding unit spacing of 0.5 mm. Data shows that with pure aluminum plates, the contact area between the liquid film and air is small, making it difficult to cool down. However, with hydrophilic aluminum plates, the contact area between the liquid film and air is larger, which can effectively reduce the temperature of the heated water to approximately room temperature.

[0044] The surface of hydrophilic anodized aluminum plates is an aluminum oxide layer with a thermal conductivity of 5~45 W / (m·K), exhibiting strong thermal conductivity. Therefore, its cooling time is significantly shorter than that of pure aluminum plates. Acrylic hydrophilic aluminum plates, on the other hand, have an acrylic acid surface with a thermal conductivity of 0.5 W / (m·K), lower than that of the aluminum oxide layer. Although the temperature can be brought to a level comparable to that of hydrophilic anodized aluminum plates, it takes much longer. Furthermore, hydrophilic polymers can adsorb and store large amounts of water, while anodized aluminum itself does not possess water-absorbing properties. However, its nanoporous structure gives it extremely high surface energy, making the surface superhydrophilic to liquids. The contact angle can be adjusted to below 10 degrees while ensuring that water does not penetrate the interior but spreads rapidly on the surface. Therefore, a superior cooling effect can be achieved.

[0045] As a specific embodiment, the flow guiding structure is located in the middle of the hydrophilic flow guiding plate, with the uppermost end of the flow guiding structure and the uppermost end of the hydrophilic flow guiding plate separated by a certain distance, and the lowermost end of the flow guiding structure and the lowermost end of the hydrophilic flow guiding plate separated by a certain distance.

[0046] This structural design positions the flow guide structure as the central processing unit of the plate. The upper and lower ends of the flow guide structure maintain a distance from the plate edge, providing a buffer space before the liquid film flows into the flow guide zone and allowing sufficient length for it to spread on the hydrophilic surface after leaving the flow guide zone. This ensures the liquid film smoothly enters and leaves the flow guide zone, avoiding turbulence or splashing at the edges, making the liquid film reformation process more stable and controllable, suitable for scenarios with extremely high requirements for liquid film stability.

[0047] Optionally, the flow guiding structure is positioned close to the upper heat dissipation pipe section, with the uppermost end of the flow guiding structure close to or flush with the uppermost end of the hydrophilic flow guiding plate, and the lowermost end of the flow guiding structure being spaced a certain distance from the lowermost end of the hydrophilic flow guiding plate.

[0048] This structural design places the flow guide zone at the front, allowing coolant dripping from the upper heat dissipation pipes to be immediately captured and distributed. This maximizes the distribution capacity of the flow guide structure and is particularly suitable for applications with high liquid flow rates or strong downward impacts. It quickly disperses any concentrated water flow, improving distribution efficiency and preventing liquid accumulation at the top of the plate.

[0049] Optionally, the flow guiding structure is positioned close to the lower heat dissipation pipe section, with the lowest end of the flow guiding structure close to or flush with the lowest end of the hydrophilic flow guiding plate, and the highest end of the flow guiding structure spaced a certain distance from the highest end of the hydrophilic flow guiding plate.

[0050] This structural design places the flow guide zone at the rear, allowing the coolant to flow naturally under gravity and due to the hydrophilicity of the plate surface. Near the outlet, the flow guide structure then performs final shaping. This facilitates final homogenization of the liquid flow before it reaches the next stage of heat dissipation pipes, ensuring optimal uniformity in the liquid distribution as it drips down. Simultaneously, the larger hydrophilic surface area at the top of the plate can be used to assist in evaporative cooling.

[0051] Taking anodized aluminum plate as a hydrophilic guide plate as an example, during the operation of the evaporative heat dissipation device, the fluid to be cooled circulates inside the heat dissipation pipe section, and a water distribution device is installed above the heat dissipation pipe section. For example, by making precise openings at 1mm intervals at the bottom of the water distribution device or using other flow equalization structures, and by driving the circulation pump, the coolant is quantitatively distributed. When the coolant drips evenly onto the outer surface of the heat dissipation pipe section, a continuous and uniform thin liquid film is formed. At the same time, based on the forced convection of the circulating fan, air flows from bottom to top across the surface of the liquid film at a specific flow rate, allowing the liquid film to effectively absorb the heat released by the fluid medium inside the pipe. In this process, the liquid film achieves efficient heat exchange through two dominant mechanisms: on the one hand, it absorbs the sensible and latent heat transferred by the fluid inside the pipe; on the other hand, it transfers heat to the air medium through phase change mass transfer and convective heat transfer. The saturated humid air that has completed the heat exchange is finally discharged in an orderly manner through the system exhaust structure.

[0052] Subsequently, the coolant, after initial heat exchange, falls onto the surface of the hydrophilic guide plate under gravity. This hydrophilic guide plate features a micro-nano structure design, with a flow channel spacing of less than 0.5 mm in the initial region. Through a multi-branched, radial, or matrix-shaped flow channel layout (approximately 20 mm in length, with specific dimensions dynamically adjustable according to the heat load), the falling droplets are redistributed into multiple uniform water streams, effectively avoiding localized drying caused by water accumulation and ensuring complete wetting of the heat exchange surface. When the liquid film leaves the guide area, it naturally contracts under surface tension. At this point, the porous superhydrophilic properties of the anodized aluminum plate play a crucial role, rapidly redistributing the droplets through capillary action to form a stable thin liquid film. This process increases the gas-liquid contact area, improving evaporation mass transfer efficiency. Simultaneously, the increased surface area achieved through the porous structure further enhances heat dissipation performance. Furthermore, this surface characteristic effectively suppresses droplet aggregation, reducing the risk of water accumulation and ensuring a stable and efficient heat and mass transfer process.

[0053] Through the synergistic effect of flow distribution, surface spreading, and evaporative heat dissipation, the coolant cools down as it flows through the hydrophilic guide plate, effectively overcoming the problem of heat dissipation efficiency degradation caused by heat accumulation in traditional systems. The cooled coolant then enters the next heat dissipation pipe section to continue the heat dissipation cycle. This modular, cascaded heat dissipation architecture ensures that the system maintains stable heat dissipation performance under different load conditions, achieving continuously optimized thermal management.

[0054] In addition to providing an evaporative cooling device, the present invention also provides, for example, Figure 3 A control method for an evaporative heat dissipation device is shown, comprising: Obtain the initial thickness of the liquid film at the uppermost inlet of the hydrophilic guide plate; Track the dynamic thickness changes of the liquid film at various points as it flows downward along the hydrophilic guide plate; The minimum allowable thickness is determined by the mass flow rate of the liquid film, combined with dynamic force balance and stability analysis of the liquid film flow. The maximum allowable thickness for heat dissipation dominated by evaporation is calculated by inversely using the heat transfer coefficient threshold. If the actual liquid film thickness at any position on the hydrophilic guide plate exceeds the safe range between the minimum and maximum allowable thickness, adjust the wind speed or water flow rate to bring the liquid film thickness back to the safe range.

[0055] The control method of this invention elevates the operation and management of evaporative cooling devices to an intelligent level. By real-time monitoring of the key parameter of liquid film thickness and comparing it with the safe range (minimum allowable thickness, maximum allowable thickness) calculated based on fluid mechanics and heat transfer theories, it dynamically adjusts operating parameters, including wind speed and water flow rate. This prevents both localized drying and thermal failure caused by an excessively thin liquid film and a decrease in evaporation efficiency caused by an excessively thick liquid film. Through dynamic control, the liquid film thickness is maintained within the safe range, ensuring that the device always operates under conditions of high evaporative cooling efficiency.

[0056] Specifically, the coolant enters from the top inlet of the hydrophilic baffle. Due to the hydrophilicity of the baffle, a liquid film forms on its surface. The thickness of this film significantly impacts the actual evaporative cooling efficiency. If the film is too thin, it is prone to breakage and drying; if it is too thick, sensible heat transfer will replace latent heat phase transformation as the dominant heat dissipation factor, both reducing cooling efficiency. Therefore, the liquid film at the top inlet must first be within a safe thickness range. If it is not within this range, the initial thickness is adjusted by regulating the water flow rate and / or airflow to bring it within the safe range. Correspondingly, the dynamic thickness of the liquid film at various locations on the hydrophilic baffle must also be within a safe range to ensure that the film is neither too thin nor too thick at any point.

[0057] Determining the safe zone first involves identifying the minimum and maximum allowable thicknesses, using the minimum allowable thickness as the lower limit and the maximum allowable thickness as the upper limit to define the safe zone. The minimum allowable thickness is determined based on the liquid film's mass flow rate, combined with the balance between interfacial tension, gravity, interfacial shear force, and wall hydrophilicity. The maximum allowable thickness is calculated using the expression for the heat transfer coefficient with respect to the liquid film thickness, and by inversely calculating the corresponding maximum allowable thickness based on the lower limit threshold of the heat transfer coefficient. The calculation of the minimum and maximum allowable thicknesses requires real-time acquisition of allowable parameters of the heat dissipation device and environmental parameters for dynamic updates to the safe zone. These parameters include, but are not limited to, the temperature of the fluid to be cooled within the heat dissipation pipe section, the wind speed and direction blowing across the surface of the serpentine heat dissipation component, the water flow rate entering from the top of the hydrophilic guide plate, and ambient temperature and humidity. The safe zone is dynamically updated based on these parameters, thereby enabling real-time monitoring and adjustment of the liquid film thickness.

[0058] If the initial thickness or dynamic thickness is less than the minimum allowable thickness, at least one of the following adjustment methods should be selected: increasing the water flow rate or increasing the wind speed in the downstream direction. If the initial thickness or dynamic thickness is greater than the maximum allowable thickness, at least one of the following adjustment methods should be selected: decreasing the water flow rate or increasing the wind speed in the upstream direction.

[0059] In this invention, the initial thickness and dynamic thickness can be obtained in various ways. For example, the thickness of the liquid film at each position can be obtained by acquiring images of the liquid film covering the hydrophilic guide plate in real time from the side, or it can be calculated based on actual parameters combined with a theoretical model. Any method that can obtain the initial thickness and dynamic thickness can be applied to the control method of this invention.

[0060] As a specific embodiment, the minimum allowable thickness is directly proportional to the third power of the interfacial tension, inversely proportional to the third power of the coolant density, inversely proportional to the square of the third of the interfacial shear force, and directly proportional to the third power of the difference between 1 and the cosine of the contact angle.

[0061] In determining the minimum allowable thickness, the key to preventing localized drying on the surface of the hydrophilic guide plate is ensuring that the liquid film thickness δ is greater than the critical minimum value δmin at all locations. This critical value is based on the stability analysis of the liquid film flow, considering the dynamic balance between interfacial tension γ, gravity, interfacial shear force τi, and wall hydrophilicity (contact angle β). When the liquid film is too thin, the interfacial tension cannot resist the combined effect of flow inertia and interfacial shear force (especially the upward pull in the opposite wind direction), causing the liquid film to break or form dry spots. The core of the anti-drying assumption is to determine the minimum thickness (critical film thickness δmin) for the liquid film to maintain stable flow, avoiding wall drying due to liquid film breakage. Its derivation is based on dynamic force balance and interfacial stability analysis, and considers the influence of wind speed direction on shear force. When the liquid film thickness decreases to the critical value, the interfacial tension cannot resist the combined effect of flow inertia and interfacial shear force, leading to liquid film breakage.

[0062] Specifically, the minimum allowable thickness δmin is calculated by multiplying a coefficient of 1.82 by the power of one-third of the first film thickness parameter, and then by the power of the square of three of the second film thickness parameter. The first film thickness parameter is the product of the difference between the cosine of the contact angle β and the interfacial tension, divided by the density of the coolant. The second film thickness parameter is the dynamic viscosity μi of the coolant divided by the interfacial shear force. The interfacial tension is calculated using the Harkins empirical formula: 75.796 - (0.145 multiplied by the interfacial temperature Ti at the liquid-gas interface) - (0.00024 multiplied by the square of the interfacial temperature Ti), in millinewtons per meter (mN / m). Under downstream wind conditions, the interfacial shear force is greater than 0, increasing the net driving force and decreasing the minimum allowable thickness. Under upstream wind conditions, the interfacial shear force is less than 0, decreasing the net driving force and increasing the minimum allowable thickness.

[0063] As a better option, in order to leave a margin in engineering and prevent drying fracture at the critical state of the minimum allowable thickness, the calculated minimum allowable thickness can be enlarged to a certain extent to obtain the final minimum allowable thickness; for example, the calculated minimum allowable thickness can be multiplied by 1.5 to obtain the final minimum allowable thickness for determining the safe range.

[0064] Optionally, the maximum allowable thickness is obtained by dividing the thermal conductivity of the coolant by a preset heat transfer coefficient threshold.

[0065] The core of determining the maximum allowable thickness is to ensure that evaporation is the dominant process on the surface of the hydrophilic guide plate. A thicker liquid film means a higher mass flow rate and coolant velocity, causing heat transfer to gradually shift to convection (similar to the heat exchange pattern of traditional water-cooled condensers, with a similar cooling effect). This significantly reduces the heat transfer coefficient, i.e., the cooling effect. Therefore, the liquid film thickness needs to be controlled within a certain range to prevent it from becoming excessive, ensuring that latent heat phase change remains the dominant heat dissipation factor. The maximum allowable thickness δmax is less than or equal to the minimum threshold of the thermal conductivity kl of water divided by the heat transfer coefficient α (usually set to 2000 W / (m²)). 2 ·K)).

[0066] As a better option, in order to avoid approaching the limit of the maximum allowable thickness and to ensure the stable operation of the heat dissipation process, the calculated maximum allowable thickness can be reduced to a certain extent to obtain the final maximum allowable thickness; for example, the calculated maximum allowable thickness can be multiplied by 0.9 to obtain the final maximum allowable thickness for determining the safe range.

[0067] The above embodiments are further elaborations and descriptions of the present invention to facilitate understanding, and are not intended to limit the present invention in any way. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An evaporative heat dissipation device, characterized in that, It includes a water distribution device that distributes coolant to the outer surface of the lower serpentine heat dissipation component to form a liquid film; The serpentine heat dissipation assembly includes several heat dissipation pipe segments arranged from top to bottom, and a connecting part that connects each heat dissipation pipe segment in sequence; it also includes a hydrophilic guide plate disposed between two adjacent heat dissipation pipe segments, so that the coolant flowing down from the outer surface of the upper heat dissipation pipe segment flows to the outer surface of the lower heat dissipation pipe segment after being guided by the hydrophilic guide plate.

2. The evaporative cooling device according to claim 1, characterized in that, The hydrophilic guide plate includes a substrate and a guide structure disposed on the substrate; The outer surface of the substrate is coated with a hydrophilic functional layer or a micro / nano structure is constructed to form a hydrophilic interface. The flow guiding structure includes several spaced-apart flow guiding units, which adopt a branched, radial, or matrix-type flow channel layout.

3. The evaporative cooling device according to claim 2, characterized in that, The flow guiding structure is located in the middle of the hydrophilic flow guiding plate. The uppermost end of the flow guiding structure is spaced a certain distance from the uppermost end of the hydrophilic flow guiding plate, and the lowermost end of the flow guiding structure is spaced a certain distance from the lowermost end of the hydrophilic flow guiding plate.

4. The evaporative cooling device according to claim 2, characterized in that, The flow guiding structure is positioned close to the upper heat dissipation pipe section, with the uppermost end of the flow guiding structure close to or flush with the uppermost end of the hydrophilic flow guiding plate, and the lowermost end of the flow guiding structure being a certain distance away from the lowermost end of the hydrophilic flow guiding plate.

5. The evaporative heat dissipation device according to claim 2, characterized in that, The flow guiding structure is positioned close to the lower heat dissipation pipe section, with the lowest end of the flow guiding structure close to or flush with the lowest end of the hydrophilic flow guiding plate, and the highest end of the flow guiding structure being a certain distance away from the highest end of the hydrophilic flow guiding plate.

6. An evaporative heat dissipation device according to any one of claims 1-5, characterized in that, The water distribution device is provided with several openings or flow equalization structures at equal intervals facing the bottom of the serpentine heat dissipation component, so that the coolant drips onto the outer surface of the serpentine heat dissipation component. A water storage device is provided below the serpentine heat dissipation component to receive the coolant dripping from the serpentine heat dissipation component. The water storage device and the water distribution device are connected by a circulating pump, which transports the coolant from the water storage device to the water distribution device.

7. An evaporative heat dissipation device according to any one of claims 1-5, characterized in that, The evaporative cooling device also includes a circulating fan, which drives outside air to enter from the lower air inlet of the evaporative cooling device, flow upward over the surface of the liquid film, and then exit from the upper air outlet of the evaporative cooling device.

8. A control method for an evaporative heat dissipation device, applicable to the evaporative heat dissipation device as described in any one of claims 1-7, characterized in that, include: Obtain the initial thickness of the liquid film at the uppermost inlet of the hydrophilic guide plate; Track the dynamic thickness changes of the liquid film at various points as it flows downward along the hydrophilic guide plate; The minimum allowable thickness is determined by the mass flow rate of the liquid film, combined with dynamic force balance and stability analysis of the liquid film flow. The maximum allowable thickness for heat dissipation dominated by evaporation is calculated by inversely using the heat transfer coefficient threshold. If the actual liquid film thickness at any position on the hydrophilic guide plate exceeds the safe range between the minimum and maximum allowable thickness, adjust the wind speed or water flow rate to bring the liquid film thickness back to the safe range.

9. The control method for an evaporative heat dissipation device according to claim 8, characterized in that, The minimum allowable thickness is directly proportional to the third power of the interfacial tension, inversely proportional to the third power of the coolant density, inversely proportional to the square third power of the interfacial shear force, and directly proportional to the third power of the difference between 1 and the cosine of the contact angle.

10. A control method for an evaporative heat dissipation device according to claim 8 or 9, characterized in that, The maximum allowable thickness is obtained by dividing the thermal conductivity of the coolant by a preset heat transfer coefficient threshold.

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