Ehd-assisted two-phase heat dissipation element with condensation flow guide liquid return structure

Abstract

The application discloses an EHD-assisted two-phase heat dissipation element with a condensation flow guide liquid return structure and relates to the technical field of heat dissipation elements. The application is used for solving the problems of insufficient steam transport driving force in a thin sealed cavity, discontinuous condensate return path and difficulty in integrating a high-voltage electrode and a condensation structure. The application comprises a cover plate, a shell, a condensation flow guide liquid return assembly and two groups of needle-point high-voltage emission electrodes. The cover plate is arranged at the upper end of the shell and cooperates with the shell to form a sealed cavity. The bottom of the sealed cavity is filled with working liquid. The upper part of the sealed cavity is provided with a steam space area. The top of the middle of the cover plate is provided with a conductive grounding layer electrically connected to a grounding end. The inner side walls of the two sides of the shell are each provided with a group of needle-point high-voltage emission electrodes. The conductive needle points of the needle-point high-voltage emission electrodes are located in the steam space area and are arranged towards the conductive grounding layer. The conductive needle points are electrically connected to a direct-current high-voltage power supply. The application is used for structural heat dissipation.

Description

Technical Field

[0001] This invention relates to the field of heat dissipation element technology, and specifically to an EHD auxiliary two-phase heat dissipation element with a condensation guiding and liquid return structure. Background Technology

[0002] With the continuous upgrading of the performance of electronic components such as third-generation semiconductor power devices, high-speed processors, industrial lasers, and high-density integrated optoelectronic modules, the heat flux density per unit area of ​​the devices has increased significantly. The internal assembly space of the whole machine continues to become thinner and more compact. Problems such as local hot spots and uneven temperature distribution are very likely to occur in the narrow and sealed cavity. Overheating of hot spots will directly cause device performance degradation, operation drift, and shortened service life. In severe cases, it will cause device thermal failure. Therefore, the heat dissipation structure with ultra-thin, high temperature uniformity and high heat transfer limit has become the core requirement for the research and development of high-end electronic equipment.

[0003] Two-phase heat dissipation elements such as vapor chambers and flat plate heat pipes rely on the latent heat of phase change—the heat absorption during evaporation and the release of heat during condensation—to achieve rapid heat transfer across regions. They offer advantages such as no mechanical vibration, thin and lightweight structures, and high equivalent thermal conductivity, making them widely used in confined space heat dissipation scenarios such as consumer electronics, automotive power modules, and optical communication equipment. However, existing thin two-phase heat dissipation elements use capillary force as the sole driving force for working fluid circulation, resulting in inherent heat transfer bottlenecks: the flattened cavity compresses the vapor flow cross-section, drastically increasing flow resistance as vapor travels from the bottom evaporation zone to the top condensation surface, easily leading to vapor stagnation and localized air blockage under high-power conditions. Simultaneously, traditional capillary wick reflux structures rely on a single capillary channel for liquid guidance, lacking a layered, directional condensate flow structure. This results in fragmented and discontinuous condensate reflux paths, preventing rapid and stable condensate return to the evaporation zone, easily leading to problems such as drying out of the evaporation zone and a sharp drop in heat transfer limits, making it difficult to meet the long-term stable heat dissipation requirements of ultra-high heat flux densities.

[0004] To overcome the capillary-driven heat transfer limit, the industry has introduced electrohydrodynamics (EHD) to enhance two-phase flow circulation. EHD technology relies on a non-uniform high-voltage electric field to ionize gaseous working fluid molecules within the cavity, generating charged ions. These charged particles migrate directionally under the influence of the electric field and drag the neutral working fluid through momentum collisions, forming a directional flow. The entire process involves no moving mechanical parts such as fans or pumps, and can actively drive steam flow within a sealed cavity, significantly improving steam transport rates. Existing EHD auxiliary two-phase heat dissipation structures simply arrange the high-voltage emitting electrode and the grounding collecting electrode inside the cavity. In practical applications, this exposes two major structural defects: First, the high-voltage needle tip emitting end is completely blocked by the continuous solid wall and shell structure, the electric field lines between the electrode and the grounding end are interrupted, the effective electric field strength is greatly reduced, the ion ionization efficiency decreases, the charge directional transport channel is blocked, and the active steam-driven effect of EHD is severely weakened. Second, the existing scheme only focuses on the electric field-driven unidirectional flow of steam and does not independently design a continuous, layered liquid phase dedicated return channel. The condensate relies solely on gravity and weak capillary force to fall back naturally. Under conditions of equipment tilting and multi-position installation, problems such as liquid accumulation, liquid film covering the condensation surface, and interruption of liquid return are very likely to occur, which cannot guarantee a continuous and stable liquid supply to the evaporation zone and results in poor matching of the vapor-liquid two-phase circulation.

[0005] Furthermore, existing EHD heat dissipation electrodes and condensation guiding structures are mostly arranged separately, leading to interference between the electrode structure, condensate collection tank, and return channel. This results in low utilization of the internal space of the cavity, making it difficult to simultaneously achieve efficient electric field drive and stable liquid phase reflux in ultra-thin cavities. Conventional grounding electrodes are arranged in a scattered point or narrow strip pattern, failing to form a uniform electric field region that fully covers and directionally guides steam upwards. This results in scattered and chaotic steam flow and insufficient heat exchange utilization on the condensation surface. In summary, existing thin two-phase heat dissipation elements cannot simultaneously solve the multiple technical contradictions of insufficient steam transport driving force, discontinuous condensate reflux path, and difficulty in integrating high-voltage electrodes and condensation guiding structures. Consequently, they cannot meet the high-efficiency heat dissipation requirements of highly integrated, high-power electronic devices in long-term, multi-position, and ultra-thin spaces. Summary of the Invention

[0006] In order to solve the problems of insufficient steam transport driving force, discontinuous condensate return path, and difficulty in integrating high-voltage electrodes with condensation structure in existing thin-walled closed cavities, this invention proposes an EHD auxiliary two-phase heat dissipation element with condensate guiding and return structure.

[0007] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0008] An EHD auxiliary two-phase heat dissipation element with a condensation guiding and return liquid structure includes a cover plate, a housing, a condensation guiding and return liquid assembly, and two sets of needle-tip high-voltage emitting electrodes. The cover plate is located at the upper end of the housing and forms a sealed cavity with the housing. The bottom of the sealed cavity is filled with working liquid, and the upper part of the sealed cavity is provided with a vapor space area. A conductive grounding layer with an electrical connection to the grounding terminal is provided at the top of the middle of the cover plate. A set of needle-tip high-voltage emitting electrodes is provided on each of the inner sidewalls of the two sides of the housing. The conductive needle tip of the needle-tip high-voltage emitting electrode is located in the vapor space area and is set towards the conductive grounding layer. The conductive needle tip is electrically connected to a DC high-voltage power supply. The vapor generated by the working liquid in the vapor space area moves to the inner end face of the cover plate and condenses into liquid condensate. The condensate flows to the working liquid through the condensation guiding and return liquid assembly.

[0009] Furthermore, a set of needle-tip high-voltage emitting electrodes includes multiple needle-tip high-voltage emitting electrodes evenly distributed along the length of the sidewall of the housing, with the needle-tip high-voltage emitting electrodes on both sides of the housing arranged opposite to each other.

[0010] Furthermore, the needle-tip high-voltage emission electrode passes through the sidewall of the housing via a ceramic insulating seal.

[0011] Furthermore, in the needle-type high-voltage transmitting electrode, all conductive connectors other than the conductive needle tip are covered with a continuous insulating layer.

[0012] Furthermore, the cover plate is shaped like a triangular roof ridge, and the conductive grounding layer is located at the highest edge of the cover plate.

[0013] Furthermore, the condensate guiding and return liquid assembly includes two sets of hydrophilic guiding channels, two gravity-widening guiding sections, two gapped edge collection tanks, and two return liquid channels. The two sets of hydrophilic guiding channels are arranged opposite each other on both sides of the inner end face of the cover plate. The upper ends of the inner sidewalls at both ends of the shell are provided with gravity-widening guiding sections, and the upper ends of the inner sidewalls on both sides of the shell are provided with gapped edge collection tanks. Each gapped edge collection tank is connected to a return liquid channel. Under the action of gravity, the liquid condensate inside the cover plate flows through the hydrophilic guiding channels into the gravity-widening guiding sections and the gapped edge collection tanks. The liquid condensate in the gravity-widening guiding sections flows into the gapped edge collection tanks, and the liquid condensate in the gapped edge collection tanks flows back into the working liquid through the return liquid channels.

[0014] Furthermore, the guide port of the gravity-widening guide section is generally shaped as high in the middle and low on both sides, and the diameter of the guide port of the gravity-widening guide section gradually increases from the middle to both sides. The two ends of the gravity-widening guide section are provided with guide section outlet ports. The guide section outlet ports are located above the inflow end of the gap edge liquid collection tank. The return liquid channel is vertically located below the outflow end of the gap edge liquid collection tank. The outflow end of the gap edge liquid collection tank is connected to the upper inflow end of the return liquid channel. The gap edge liquid collection tank is inclined downward from the inflow end to the outflow end. The lower side wall of the return liquid channel is provided with a return port.

[0015] Furthermore, the hydrophilic drainage channel is inclined in a herringbone shape on the inner end face of the cover plate.

[0016] Furthermore, the surface of the hydrophilic guide channel is laser-textured to form a hydrophilic surface.

[0017] Furthermore, a temperature sensor is provided on the inner wall of the bottom surface of the housing, and the controller of the DC high voltage power supply can adjust the voltage intensity of the DC high voltage power supply according to the real-time temperature monitored by the temperature sensor.

[0018] The beneficial effects of this invention compared to the prior art are:

[0019] First, this invention completely exposes all needle tips as high-voltage transmitters, while the remaining conductive substrate of the needle tips is covered with an insulating layer. Simultaneously, a 10mm wide strip-shaped grounding area is located at the center of the top of the cover plate to serve as a grounding collector. On one hand, the exposed needle tips and the central strip-shaped grounding area can construct a continuous and concentrated electric field channel, forming a directional EHD driving airflow, significantly enhancing the transport efficiency of steam from the evaporation zone to the condensation surface, and alleviating the problems of steam retention and blockage inside the thin cavity. On the other hand, grounding is limited to the narrow central strip area, eliminating the need for grounding the entire cover plate, reducing the difficulty of the cavity's insulation and conductive structure layout, and avoiding the defects of electric field dispersion and reduced driving efficiency caused by large-area grounding. This achieves efficient charge ionization and directional transport within an ultra-thin, sealed cavity.

[0020] Secondly, this invention features a zoned and independently designed flow path for both the vapor and liquid phases. The EHD electric field specifically enhances the upward transport of the vapor phase, while the condensed liquid phase returns via a dedicated flow-guiding structure. The two circulation channels for vapor and liquid do not interfere with each other, and their mechanisms are clearly defined. Unlike traditional EHD heat dissipation structures that involve mixed vapor and liquid flow without a dedicated return channel, this invention achieves coordinated operation of active vapor-phase drive and directional liquid-phase return, preventing condensate dispersion from obstructing the electrode emitter, ensuring a stable and continuous electric field, significantly improving the matching degree of the two-phase working fluid circulation, and enhancing the ultimate heat dissipation power of the component.

[0021] Third, the top condensing surface is designed with a funnel-shaped gravity-guided slope that gradually widens from top to bottom. Under the action of gravity potential energy, the condensate flows smoothly along the slope to the liquid collection tank at the edge of the gap. The gradually widening slope structure can accelerate the condensate collection speed, effectively reduce the phenomenon of local accumulation of condensate on the condensing surface and stagnation of liquid at the end of the tank, ensure full utilization of the heat exchange area of ​​the condensing surface, and avoid the thick liquid film weakening the condensation heat transfer coefficient.

[0022] Fourth, the edge collection tank has a reserved flow guide gap, which, together with the side wall return liquid channel through the cavity, forms a complete and continuous liquid phase return link. The condensate can be stably returned to the bottom evaporation liquid pool along the fixed channel. Even if the equipment is in various tilted installation postures, it can continuously replenish the liquid working medium to the evaporation zone, prevent the evaporation zone from drying out and failing, and improve the multi-condition adaptability of the heat dissipation element.

[0023] Fifth, the overall heat dissipation device has no mechanical moving parts such as fans and hydraulic pumps, and its structure is compact and thin, making it suitable for the small and ultra-thin assembly space of highly integrated electronic devices. At the same time, it can dynamically adjust the output voltage of the high-voltage power supply according to the real-time heat load of the device, flexibly change the magnitude of the EHD electric field driving force, reduce the output energy consumption when the heat load is low, and improve the steam transport capacity under high heat flow conditions, so as to achieve a dynamic balance between heat dissipation performance and energy consumption.

[0024] Sixth, this invention integrates the electric field driving electrode, condensation guide groove, liquid collection structure, and side wall liquid return channel into a single unit. The spatial layout of each structural unit does not interfere with each other, resulting in higher utilization of the internal space of the cavity. It simplifies the internal structure layout of the ultra-thin two-phase heat dissipation element, reduces the difficulty of overall processing and sealing assembly, and enhances product consistency and production feasibility. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall exploded structure of the present invention;

[0026] Figure 2 This is a bottom view of the cover plate structure in this invention;

[0027] Figure 3 This is a schematic diagram of the side end face structure of the present invention;

[0028] Figure 4 yes Figure 3 Schematic diagram of the AA-direction cross-section structure;

[0029] Figure 5 This is a side view of the present invention;

[0030] Figure 6 yes Figure 5 Schematic diagram of the BB-direction cross-sectional structure in the middle;

[0031] Figure 7 yes Figure 5 Schematic diagram of the CC-direction cross-section structure in the middle

[0032] Figure 8 This is a schematic diagram of the overall shape of the invention;

[0033] Figure 9 This is a schematic diagram illustrating the working principle of the present invention;

[0034] Figure 10This diagram illustrates the electrodynamic flow and temperature distribution of the gaseous working fluid within a sealed cavity under different needle extension lengths. The top row shows velocity contour plots and streamlines, while the bottom row shows temperature contour plots.

[0035] In the figure: 1-cover plate; 2-shell; 3-1-hydrophilic guide channel; 3-2-gravity gradually widening guide section; 3-3-gap edge liquid collection tank; 3-4-return channel; 4-working liquid and bottom liquid pool; 5-needle-tip high-voltage emission electrode. Detailed Implementation

[0036] To make the technical problems solved, the technical solutions, and the beneficial effects of the present invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0037] Specific implementation method one: Combining Figures 1 to 10 This embodiment describes an EHD auxiliary two-phase heat dissipation element with a condensation-guided return liquid structure, comprising a cover plate 1, a housing 2, a condensation-guided return liquid assembly, and two sets of needle-tip high-voltage emitting electrodes 5. The cover plate 1 is located at the upper end of the housing 2 and together with the housing 2 forms a sealed cavity. The bottom of the sealed cavity is filled with working liquid 4, and the upper part of the sealed cavity is provided with a vapor space area. The top of the middle of the cover plate 1 is provided with a conductive grounding layer that is electrically connected to the grounding terminal. Each of the two inner sidewalls of the housing 2 is provided with a set of needle-tip high-voltage emitting electrodes 5. The conductive needle tip of the needle-tip high-voltage emitting electrode 5 is located in the vapor space area and is set towards the conductive grounding layer. The conductive needle tip is electrically connected to a DC high-voltage power supply. The vapor generated by the working liquid 4 in the vapor space area moves to the inner end face of the cover plate 1 and condenses into liquid condensate. The condensate flows to the working liquid 4 through the condensation-guided return liquid assembly.

[0038] The upper end face of the housing 2 is open, and the cover plate 1 is fixedly installed on the open end of the housing 2. The cover plate 1 and the housing 2 together form a sealed cavity. The liquid level of the working liquid 4 is lower than the height of the conductive needle tip of the needle-type high-voltage emission electrode 5.

[0039] The cover plate 1 and the housing 2 are sealed together to form a closed cavity; the working liquid 4 is partially filled into the lower part of the cavity, forming a continuous liquid pool covering the bottom evaporation zone under the designed working posture of the device. The external chip is set on the outside of the bottom wall of the housing 2, and heat is transferred to the liquid pool through the bottom wall, causing the working liquid 4 to vaporize in the evaporation zone.

[0040] The cover plate 1 supports the condensation guiding structure and transfers the latent heat of condensation outward. A 10mm wide strip-shaped conductive grounding layer is disposed at the center of its top. This conductive grounding layer is grounded and serves as the EHD collector terminal. The remaining area of ​​the cover plate 1 is ungrounded and electrically isolated from the grounding layer. Multiple needle-tip high-voltage emitting electrodes 5 are installed on the side wall of the housing 2 through an insulating and sealed introduction structure. All conductive needle tips are directly exposed in the vapor space above the liquid surface and face the conductive grounding layer. All conductive connectors other than the needle tips are covered by a continuous insulating layer. A non-uniform electric field is formed between the conductive needle tips and the conductive grounding layer. Charged particles migrate towards the conductive grounding layer under the action of the electric field force and transfer momentum to the gaseous working fluid, thereby enhancing the transport of steam from the bottom evaporation zone to the top condensation zone.

[0041] The steam generated by the working liquid 4 in the steam space area moves to the inner end face of the cover plate 1 and condenses into liquid condensate. The condensate flows back to the working liquid 4 through the condensate guide return liquid assembly.

[0042] In this invention, the EHD function is only used to enhance the transport of the gaseous working fluid and does not handle liquid reflux. Liquid reflux is accomplished by the condenser-guided liquid return component and gravity, which separates the gas and liquid transport paths and reduces the mutual interference between the vapor flow and the reflux liquid.

[0043] The shell 2 has a bottom wall and circumferential side walls. The cover plate 1 covers the upper opening of the shell 2 and is connected to the shell 2 by brazing to form an airtight sealed cavity. The internal dimensions of the sealed cavity are 50mm × 50mm × 10mm.

[0044] The external chip is attached to the outer surface of the bottom wall of the housing 2, with its heating area located in the center of the bottom wall. The working liquid 4 is injected into the sealed cavity at a predetermined filling volume, so that it forms a continuous liquid layer covering the evaporation area of ​​the bottom wall in the working position; thus, the chip does not directly contact the liquid, and the heat is transferred to the liquid through the bottom wall, and the bottom liquid pool expands horizontally and continuously wets the heated area.

[0045] In this invention, a fluorinated dielectric liquid is used as the working liquid 4.

[0046] The cover plate 1 includes a thermally conductive substrate for transferring latent heat of condensation and a conductive grounding layer electrically isolated from the thermally conductive substrate. The conductive grounding layer is located at the top center of the cover plate 1, is a strip extending along the length of the cover plate 1, has a width of 10 mm, and is grounded through an independent conductive lead-out terminal; the area of ​​the cover plate 1 other than the conductive grounding layer is not grounded. Thus, the cover plate 1 as a whole serves as a condensing plate, and the conductive grounding layer serves as the grounding collector for the EHD electric field. The conductive tips of all the needle-type high-voltage emitting electrodes 5 are connected to the high-potential end of the DC high-voltage power supply and are inclined towards the conductive grounding layer. After the voltage is increased to a stable charge injection range without a sustained electric arc, charged particles are generated near the conductive tips; these charged particles migrate towards the conductive grounding layer and collide with steam molecules, forming an overall EHD volume force towards the top condensing area, thereby reducing steam transport resistance, promoting steam departure from the high-heat-flux evaporation zone, and improving the utilization rate of the condensing surface.

[0047] Specific Implementation Method Two: Combining Figures 1 to 10 This embodiment describes a set of needle-tip high-voltage emitting electrodes 5, which includes multiple needle-tip high-voltage emitting electrodes 5 evenly distributed along the length of the sidewall of the housing 2, with the needle-tip high-voltage emitting electrodes 5 on both sides of the housing 2 arranged opposite to each other.

[0048] The undisclosed technical features in this embodiment are the same as those in Specific Embodiment 1.

[0049] Multiple needle-tip high-voltage emission electrodes 5 are arranged at equal intervals along the two opposite sidewalls of the housing 2.

[0050] Specific implementation method three: Combining Figures 1 to 10 This embodiment describes a needle-tip high-voltage emission electrode 5 that passes through the side wall of the housing 2 via a ceramic insulating seal introduction member.

[0051] The undisclosed technical features in this embodiment are the same as those in Specific Embodiment 1.

[0052] Each needle-tip high-voltage transmitting electrode 5 passes through the sidewall via a ceramic insulating seal inlet, which serves both electrical isolation and gas sealing functions.

[0053] Specific implementation method four: Combination Figures 1 to 10 In this embodiment, the conductive connectors other than the conductive needle tip in the needle-tip type high-voltage transmitting electrode 5 are all covered with a continuous insulating layer.

[0054] The undisclosed technical features in this embodiment are the same as those in Specific Embodiment 1.

[0055] The highest level of the working fluid 4 is lower than all the conductive needle tips. The high-voltage conductive connectors outside the conductive needle tips are covered by a continuous insulating layer, thereby avoiding liquid bridging and creepage.

[0056] All conductive needle tips enter the steam space area and are connected to a high-voltage power supply. All conductive connectors other than the conductive needle tips are covered by a continuous insulating layer to allow charge to be injected from the exposed needle tips and to increase the creepage distance between the high-voltage part and the housing 2 and the cover plate 1.

[0057] Specific Implementation Method Five: Combining Figures 1 to 10 This embodiment describes a cover plate 1 with a triangular roof shape, and a conductive grounding layer is located at the highest edge of the cover plate 1.

[0058] The undisclosed technical features in this embodiment are the same as those in Specific Embodiment 1.

[0059] The effective condensation zone on the inner surface of cover plate 1 has a size of 48mm × 48mm, with the central ridge located on the center line of the width of the effective condensation zone. The height difference between the central ridge and the liquid collection troughs at the gap edges on both sides is 1.68mm, forming a slope that continuously descends from the central ridge to the lower edges on both sides.

[0060] Specific Implementation Method Six: Combination Figures 1 to 10 This embodiment describes a condensation guide and return liquid assembly comprising two sets of hydrophilic guide channels 3-1, two gravity-widened guide sections 3-2, two gapped edge collection tanks 3-3, and two return liquid channels 3-4. The two sets of hydrophilic guide channels 3-1 are arranged opposite each other on both sides of the inner end face of the cover plate 1. The upper ends of the inner sidewalls at both ends of the housing 2 are provided with gravity-widened guide sections 3-2, and the upper ends of the inner sidewalls on both sides of the housing 2 are provided with gapped edge collection tanks 3-3. Each gapped edge collection tank 3-3 is connected to a return liquid channel 3-4. Under the action of gravity, the liquid condensate inside the cover plate 1 flows through the hydrophilic guide channels 3-1 into the gravity-widened guide sections 3-2 and the gapped edge collection tanks 3-3. The liquid condensate in the gravity-widened guide sections 3-2 flows into the gapped edge collection tanks 3-3, and the liquid condensate in the gapped edge collection tanks 3-3 flows back to the working liquid 4 through the return liquid channels 3-4.

[0061] The undisclosed technical features in this embodiment are the same as those in Specific Embodiment 1.

[0062] A condensation guiding and return liquid assembly is formed on the inner surface of the cover plate 1. This assembly includes a hydrophilic guiding channel 3-1, a gravity-widening guiding section 3-2 located at the end of the hydrophilic guiding channel 3-1, a gapped edge collection channel 3-3 located at the edge of the cover plate 1, and a return liquid channel 3-4 extending downward along the side wall of the shell 2. After the condensate forms droplets and liquid film on the downward condensation surface, it enters the hydrophilic guiding channel 3-1 along the slope of the cover plate under the action of gravity. The hydrophilic guiding channel 3-1 guides the liquid to the lower edge, and the funnel-shaped gravity-widening guiding section 3-2 causes the liquid to flow down the continuous slope into the gapped edge collection channel 3-3, and then continues to return to the bottom working liquid 4 under the action of gravity through the return liquid channel 3-4.

[0063] Specific implementation method seven: Combining Figures 1 to 10 In this embodiment, the flow port of the gravity-widening guide section 3-2 is generally shaped as high in the middle and low on both sides, and the diameter of the flow port of the gravity-widening guide section 3-2 gradually increases from the middle to both sides. The two ends of the gravity-widening guide section 3-2 are provided with flow port. The flow port is located above the inflow end of the gap edge collecting tank 3-3. The return channel 3-4 is vertically located below the outflow end of the gap edge collecting tank 3-3. The outflow end of the gap edge collecting tank 3-3 is connected to the upper inflow end of the return channel 3-4. The gap edge collecting tank 3-3 is inclined downward from the inflow end to the outflow end. The lower side wall of the return channel 3-4 is provided with a return port.

[0064] The undisclosed technical features in this embodiment are the same as those in Specific Embodiment Six.

[0065] The hydrophilic guide channels 3-1 are arranged in a herringbone-shaped oblique arrangement. The hydrophilic guide channels 3-1 near the edge gradually turn towards the gravity-widened guide section 3-2 and the gapped edge liquid collection channel 3-3. The gravity-widened guide section 3-2 forms a funnel-shaped gradually widening downward slope, so that the liquid continuously flows into the gapped edge liquid collection channel 3-3 under the action of gravity.

[0066] The hydrophilic guide channel 3-1 has a width of 0.2 mm, a depth of 0.1 mm, and a spacing of 1.0 mm; the end of the flared downward slope of the gravity-widened guide section 3-2 is connected to the gap-edge liquid collection channel 3-3 through a connecting gap with a width of 0.3 to 0.6 mm; the gap-edge liquid collection channel 3-3 has a cross-sectional width of 1 mm and a depth of 1 mm, and is connected to the side wall return channel 3-4 at the lowest position.

[0067] The hydrophilic guide channel 3-1 near the edge of the cover plate 1 enters the gravity-widened guide section 3-2 and the gapped edge collection channel 3-3. The gravity-widened guide section 3-2 is a funnel-shaped downward slope with a length of 0.8 to 1.5 mm, and its width gradually increases towards the gapped edge collection channel 3-3. Its end connects to the gapped edge collection channel 3-3 through a connecting gap. After the condensate flows to the end of the gapped edge collection channel 3-3, it expands along the continuously downward funnel-shaped slope under the action of gravity and flows through the connecting gap, and then enters the gapped edge collection channel 3-3.

[0068] The edge-gap liquid collection tank 3-3 is located at the lower edge of the cover plate 1, and neither the edge-gap liquid collection tank 3-3 nor its inlet has rounded corners. The edge-gap liquid collection tank 3-3 is open to the sealed cavity through the connecting gap and is directly connected to the return liquid channel 3-4 at its lowest position. The return liquid channel 3-4 extends downward along the side wall of the shell 2, and its lower end opens at the liquid surface of the bottom liquid pool, allowing the condensate entering the edge-gap liquid collection tank 3-3 to continue flowing back to the bottom liquid pool under the action of gravity.

[0069] Specific implementation method eight: Combination Figures 1 to 10 In this embodiment, the hydrophilic guide groove 3-1 is inclined in a herringbone shape on the inner end face of the cover plate 1.

[0070] The undisclosed technical features in this embodiment are the same as those in Specific Embodiment Six.

[0071] The inner end face of the cover plate 1 is machined with multiple hydrophilic guide grooves 3-1, which are arranged in a herringbone diagonal pattern when viewed from below.

[0072] Specific Implementation Method Nine: Combining Figures 1 to 10 This embodiment describes a hydrophilic surface formed by laser micro-texturing of the surface of the hydrophilic guide groove 3-1.

[0073] The undisclosed technical features in this embodiment are the same as those in Specific Embodiment Six.

[0074] Specific Implementation Method Ten: Combining Figures 1 to 10 In this embodiment, a temperature sensor is provided on the inner side wall of the bottom surface of the housing 2. The controller of the DC high voltage power supply can adjust the voltage intensity of the DC high voltage power supply according to the real-time temperature monitored by the temperature sensor.

[0075] The undisclosed technical features in this embodiment are the same as those in Specific Embodiment 1.

[0076] A temperature sensor is located in the center of the bottom wall, and the controller adjusts the DC high-voltage power supply according to the temperature. When the temperature is below a first threshold, the voltage is maintained at a low level; as the temperature rises, the voltage is gradually increased; and the power supply is immediately cut off when an abnormal discharge current is detected. The actual voltage, electrode spacing, and needle tip curvature radius are determined experimentally based on the vapor pressure of the fluorinated dielectric liquid and the insulation distance, ensuring that the device operates within a stable charge injection range without continuous arcing.

[0077] Working principle

[0078] During operation, the working liquid 4 at the bottom absorbs heat from the external chip and generates steam. The EHD (Electronic Heat Dissipation) effect concentrates the steam and transports it to the 10mm wide contact area at the top center of the cover plate 1. After reaching the top condensation zone, the steam releases latent heat on the condensation surface of the cover plate 1 and forms droplets and liquid films. Under the action of gravity, the condensate flows down the slope of the cover plate 1 into the hydrophilic guide channel 3-1, then flows along the gravity-widening guide section 3-2 into the gapped edge collection tank 3-3, and finally returns to the bottom liquid pool by gravity through the return channel 3-4, thus forming a closed two-phase cycle of "bottom evaporation - EHD-assisted rise - top condensation - slope gravity collection - sidewall gravity return".

[0079] To illustrate the fundamental principle of electrohydrodynamic-driven gaseous working fluid transport in this invention, a two-dimensional numerical model was established, comprising a high-voltage launching needle, a grounded condensation wall, a high-temperature region at the bottom, and a low-temperature region at the top. While maintaining the same applied voltage, charge injection intensity, and thermal boundary conditions, comparative calculations were performed on three structures with launching needle extension lengths of L=1.86mm, 2L=3.72mm, and 3L=5.58mm. The resulting steady-state velocity field, streamlines, and temperature field are shown below. Figure 7 As shown.

[0080] Depend on Figure 10 As shown in the top row, space charge, under the influence of a non-uniform electric field, experiences Coulomb force and transfers momentum to the gaseous working fluid through collisions with neutral gas molecules, thus forming a stable electrohydrodynamic circulation within the sealed cavity. The left and right emission needles each drive a main vortex rotating in opposite directions. The gaseous working fluid moves along the needle tip and side regions towards the top condensation wall, converging in the upper part of the cavity towards the center, then flowing downwards along the central region and replenishing itself at the bottom. This forms a continuous cyclic transport path consisting of a "bottom hot zone - top condensation zone - central reflux zone." This flow structure indicates that even if the net volumetric flow rate on any complete cross-section of the sealed cavity is zero, electrohydrodynamic action can still promote the exchange between the gaseous working fluid near the bottom hot zone and the top condensation wall by enhancing the upward transport branches and the intracavity circulation intensity.

[0081] As the extension length of the transmitting needle increases, the effective distance between the needle tip and the receiving electrode shortens, the concentration of the electric field and the area affected by space charge are enhanced, the region of higher velocity gradually expands, and the two main vortices within the cavity become clearer and more stable. Under the numerical conditions of this embodiment, with transmitting needle lengths of L, 2L, and 3L, the calculated maximum gas phase velocities are approximately 0.295 m / s, 0.377 m / s, and 0.470 m / s, respectively, and the volume-average velocities are approximately 0.130 m / s, 0.164 m / s, and 0.199 m / s, respectively. The 3L transmitting needle increases the maximum velocity by approximately 59.5% and the volume-average velocity by approximately 52.8% compared to the L transmitting needle, indicating that increasing the effective extension length of the transmitting needle can significantly enhance the ion wind driving capability within the cavity.

[0082] Figure 10The temperature distribution shown in the lower row corresponds to the double-vortex flow structure in the upper row. The hot gaseous working fluid generated in the high-temperature region at the bottom is transported upwards along both sides and near the needle tip under the action of the ion wind, mixing with the low-temperature gaseous fluid near the low-temperature wall at the top. The cooled gaseous working fluid at the top then moves back to the bottom through the central recirculation region. This circulating flow alters the temperature stratification state that relies solely on heat conduction and natural convection, which helps reduce local heat accumulation and expands the effective gaseous heat exchange range between the bottom hot zone and the top condensation zone. As the length of the ejector needle increases, the gaseous circulation speed and mixing effect increase simultaneously, thus facilitating the faster transport of steam generated near the evaporation zone to the top condensation zone and improving the effective utilization of the condensation wall surface.

[0083] The above calculation results demonstrate that, by setting a high-voltage transmitting needle on the sidewall and using the top condensation structure as a grounding receiver, the present invention can establish a directional transport channel between the evaporation and condensation regions, composed of space charge, electric field, and gas-phase circulation. This channel enhances the transport of the gaseous working fluid from the bottom hot zone to the top condensation zone and maintains continuous circulation through internal reflux, thereby providing a kinetic basis for enhancing the evaporation-condensation process and improving the heat transfer capacity of the device. The above numerical results are used to illustrate the gas-phase electrodynamic transport mechanism of the present invention and do not constitute a limitation on the specific length of the transmitting needle, voltage, or charge injection intensity.

[0084] During manufacturing, a 4° downward slope, a hydrophilic flow channel 3-1, a gravity-widened flow guide 3-2, and a gapped edge liquid collection channel 3-3 are first machined on the inner surface of the cover plate 1. A strip-shaped conductive grounding layer with a width of 10mm extending along the length of the cover plate is formed in the middle of the top of the cover plate 1. An insulating isolation layer is set between the conductive grounding layer and the thermally conductive substrate of the cover plate 1, and an independent grounding lead is connected. The rest of the cover plate 1 remains ungrounded. Subsequently, a return liquid channel 3-4 and an electrode inlet hole are machined on the side wall of the shell 2. A ceramic insulating sealing inlet and a needle-tip high-voltage emitting electrode 5 are installed, exposing all conductive needle tips to the vapor space and facing the conductive grounding area, while keeping the conductive connectors other than the needle tips insulated. Then, the cover plate 1 is sealed to the shell 2, the sealed cavity is evacuated, a predetermined amount of fluorinated dielectric liquid is filled as the working liquid 4, and the cavity is sealed. Finally, airtightness, insulation, charge injection initiation voltage, abnormal discharge, and thermal performance tests are performed.

[0085] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. An EHD auxiliary two-phase heat dissipation element with a condensation guiding and liquid return structure, characterized in that: The device includes a cover plate (1), a housing (2), a condenser guide return liquid assembly, and two sets of needle-tip high-voltage emission electrodes (5). The cover plate (1) is located at the upper end of the housing (2) and together with the housing (2) forms a sealed cavity. The bottom of the sealed cavity is filled with working liquid (4). The upper part of the sealed cavity is provided with a steam space area. The top of the middle of the cover plate (1) is provided with a conductive grounding layer that is electrically connected to the grounding terminal. Each of the inner sidewalls of the housing (2) is provided with a set of needle-tip high-voltage emission electrodes (5). The conductive needle tip of the needle-tip high-voltage emission electrode (5) is located in the steam space area and is set towards the conductive grounding layer. The conductive needle tip is electrically connected to a DC high-voltage power supply. The steam generated by the working liquid (4) in the steam space area moves to the inner end face of the cover plate (1) and condenses into liquid condensate. The condensate flows to the working liquid (4) through the condenser guide return liquid assembly.

2. The EHD auxiliary two-phase heat dissipation element with a condensation guiding and liquid return structure according to claim 1, characterized in that: A set of needle-tip high-voltage emission electrodes (5) includes multiple needle-tip high-voltage emission electrodes (5) evenly distributed along the length of the sidewall of the housing (2), with the needle-tip high-voltage emission electrodes (5) on both sides of the housing (2) arranged opposite to each other.

3. The EHD auxiliary two-phase heat dissipation element with a condensation guiding and liquid return structure according to claim 1, characterized in that: The needle-tip high-voltage emission electrode (5) passes through the side wall of the housing (2) via a ceramic insulating seal.

4. The EHD auxiliary two-phase heat dissipation element with a condensation guiding and liquid return structure according to claim 1, characterized in that: In the needle-tip type high voltage emission electrode (5), all conductive connectors other than the conductive needle tip are covered with a continuous insulating layer.

5. The EHD auxiliary two-phase heat dissipation element with a condensation guiding and liquid return structure according to claim 1, characterized in that: The cover plate (1) is triangular in shape, and the conductive grounding layer is located at the highest edge of the cover plate (1).

6. The EHD auxiliary two-phase heat dissipation element with a condensation guiding and liquid return structure according to claim 1, characterized in that: The condensation guide and return liquid assembly includes two sets of hydrophilic guide channels (3-1), two gravity-widened guide sections (3-2), two gapped edge collection channels (3-3), and two return liquid channels (3-4). The two sets of hydrophilic guide channels (3-1) are arranged opposite to each other on both sides of the inner end face of the cover plate (1). The upper ends of the inner sidewalls at both ends of the shell (2) are provided with gravity-widened guide sections (3-2), and the upper ends of the inner sidewalls on both sides of the shell (2) are provided with gapped edge collection channels (3-3). Each gapped edge collection channel... The tank (3-3) is connected to a return channel (3-4) respectively. The liquid condensate inside the cover plate (1) flows into the gravity gradually widening guide section (3-2) and the gap edge collection tank (3-3) under the action of gravity through the hydrophilic guide channel (3-1). The liquid condensate in the gravity gradually widening guide section (3-2) flows into the gap edge collection tank (3-3). The liquid condensate in the gap edge collection tank (3-3) flows back to the working liquid (4) through the return channel (3-4).

7. An EHD auxiliary two-phase heat dissipation element with a condensation guiding and liquid return structure according to claim 6, characterized in that: The flow port of the gravity-widening guide section (3-2) is generally high in the middle and low on both sides. The diameter of the flow port of the gravity-widening guide section (3-2) gradually increases from the middle to both sides. The two ends of the gravity-widening guide section (3-2) are provided with flow port. The flow port is located above the inflow end of the gap edge collecting tank (3-3). The return channel (3-4) is vertically located below the outflow end of the gap edge collecting tank (3-3). The outflow end of the gap edge collecting tank (3-3) is connected to the upper inflow end of the return channel (3-4). The gap edge collecting tank (3-3) is inclined downward from the inflow end to the outflow end. The lower side wall of the return channel (3-4) is provided with a return port.

8. The EHD auxiliary two-phase heat dissipation element with a condensation guiding and liquid return structure according to claim 6, characterized in that: The hydrophilic flow channel (3-1) is inclined in a V-shape on the inner end face of the cover plate (1).

9. An EHD auxiliary two-phase heat dissipation element with a condensation guiding and liquid return structure according to claim 6, characterized in that: The surface of the hydrophilic guide groove (3-1) is laser-textured to form a hydrophilic surface.

10. An EHD auxiliary two-phase heat dissipation element with a condensation guiding and liquid return structure according to claim 1, characterized in that: A temperature sensor is provided on the inner side wall of the bottom surface of the housing (2). The controller of the DC high voltage power supply can adjust the voltage intensity of the DC high voltage power supply according to the real-time temperature monitored by the temperature sensor.

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