A microgravity spray cooling closed-loop heat dissipation device based on piezoelectric atomization and electrostatic trapping cooperation

Abstract

The application discloses a microgravity spray cooling closed-loop heat dissipation device based on piezoelectric atomization and electrostatic trapping cooperation, adopts piezoelectric atomization to replace traditional mechanical pressure atomization, and has the advantages of uniform liquid drops, near constant pressure operation, low power consumption, no wear and fast regulation and control response, and the heat exchange efficiency and on-orbit reliability are greatly improved; the liquid drops are innovatively actively trapped by electrostatic force, and the trapping efficiency is over 98% and the additional power consumption is extremely low, so that the working medium loss is greatly reduced; a microgravity circulation guarantee module is matched to realize gas-liquid separation, bubble collection and stable liquid supply in multiple postures, and multiple sensors and controllers are matched to complete intelligent self-adaptive regulation and control in the whole process; the overall heat dissipation capacity is outstanding, the device is suitable for super-high heat flux density heat sources, has high temperature control precision, is light in weight, has small working medium loss, and can meet the long-term on-orbit stable thermal control demand of a spacecraft for more than ten years.

Description

Technical Field

[0001] This invention belongs to the field of spacecraft thermal control technology, specifically relating to a microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping. Background Technology

[0002] As spacecraft payloads rapidly develop towards higher power and greater integration, the heat flux density of onboard electronic devices (such as high-power microwave devices, phased array radar T / R modules, and onboard computer processors) continues to rise. The heat flux density of some core devices has exceeded 50~100 W / cm², and the next generation of space payloads may even face extreme heat dissipation requirements exceeding 200 W / cm².

[0003] Chinese patent CN102514733A discloses a spray cooling circuit scheme based on a micro high-pressure diaphragm pump. This device uses a mechanical pump to pressurize and drive liquid through an atomizer for spraying. The working fluid is stored and pre-cooled via a liquid storage component and a heat sink structure. A liquid collection component completes gas-liquid separation and working fluid recovery. The droplet capture in this scheme relies on a mechanical collection structure and surface tension.

[0004] The US NSA Glenn Research Center conducted microgravity spray cooling experiments on the KC-135 parabolic flight platform. Regarding the application of piezoelectric atomization technology, the article "Research Progress of Piezoelectric Atomization Devices" (Zhang Jianhui et al., Journal of Nanjing University of Aeronautics and Astronautics, 2020, Vol. 1) reviews the application potential of piezoelectric atomization technology in the field of spray cooling, pointing out that piezoelectric atomization has advantages such as simple structure, low energy consumption, controllable atomization particle size (Sauter average diameter can reach 10~50μm), and no need for a high-pressure liquid supply system.

[0005] While the aforementioned existing technologies have achieved certain results in their respective applicable scenarios, the following key issues still exist when addressing the heat dissipation requirements of high heat flux density heat sources in the microgravity environment of space: (1) Existing microgravity spray cooling schemes have insufficient atomization driving force: Existing schemes, represented by CN102514733A, use a micro high-pressure diaphragm pump as the driving force, and use hydraulic drive to spray the working fluid through a pressure atomizing nozzle. This method has the following problems: it requires a high-pressure sealing structure, which increases the risk of leakage and complexity of the system; the droplet size distribution of pressure atomization is wide (usually 50~200 μm), with poor uniformity, resulting in large fluctuations in heat exchange efficiency; the mechanical pump has moving parts, which limits the reliability and lifespan of long-term operation; the pump has high power consumption, which puts an additional burden on the energy supply of the spacecraft.

[0006] (2) Low efficiency of droplet collection and working fluid recovery under microgravity: This is the most critical problem restricting the engineering of microgravity spray cooling. Under ground gravity, the sprayed droplets and liquid film can flow naturally to the collection tank under gravity; however, under microgravity (10... -3 g~10 -6 g) In the environment: the droplets lose the gravity settling effect and float in the cavity to form an aerosol suspension; the liquid film formed after the surface impact cannot rely on gravity to spread and displace, and is prone to accumulate on the heated surface, leading to drying or overflow.

[0007] Existing mechanical collection structures (such as the porous collection plate in CN102514733A) rely solely on surface tension and geometric interception to capture droplets, resulting in limited collection efficiency (estimated to be less than 70%). Uncaptured droplets disperse, causing gradual loss of the working medium, which cannot meet the requirements for long-term on-orbit operation.

[0008] (3) Lack of proactive microgravity fluid management and circulation guarantee mechanism: Most existing microgravity spray cooling schemes passively rely on capillary structure or surface tension for fluid management, lacking proactive control means: Under microgravity, there is no effective separation between the gas and liquid phases, and gas entrainment into the circulation pipeline will cause "gas blockage" phenomenon, affecting the normal operation of pumps / drive components; residual acceleration disturbances caused by different attitude changes (orbit maneuvering, attitude adjustment) will cause instability of fluid behavior in the cavity; lack of real-time monitoring and adaptive adjustment capability for liquid film thickness, droplet distribution, and working fluid quantity.

[0009] (4) Insufficient system closed-loop and integration: The system has a large volume and mass, making it difficult to meet the stringent requirements of spacecraft payloads for lightweight and compact design. Summary of the Invention

[0010] The purpose of this invention is to provide a microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping. This invention improves the atomization heat exchange performance and equipment reliability through piezoelectric atomization, and achieves efficient and low-consumption working fluid recovery under microgravity through electrostatic active trapping. It is combined with a microgravity circulation support module and system controller with gas-liquid separation, bubble treatment, multi-attitude adaptation and multi-sensor monitoring functions to achieve intelligent adaptive control. The overall heat dissipation performance is excellent, the temperature control is precise, the structure is lightweight, and the working fluid loss is low. It can meet the stable thermal control requirements of high heat flux density heat sources for long-term on-orbit operation of spacecraft for more than ten years, thereby solving the problems mentioned in the background art.

[0011] To achieve the above objectives, the present invention novelly adopts the following technical solution: A microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping includes: A piezoelectric atomization module is disposed in the spray chamber with the nozzle facing the surface of the heat source to be cooled. It is used to break the liquid cooling medium into micron-sized uniform droplets using piezoelectric vibration energy and spray them onto the surface of the heat source to be cooled. An electrostatic capture module is disposed on the inner wall of the spray chamber and located downstream of the droplet flight path of the piezoelectric atomization module. It is used to actively adsorb, capture, guide, and recover charged spray droplets through electrostatic field force. The microgravity circulation protection module is located outside the spray chamber and is connected to the working fluid supply chamber of the piezoelectric atomization module and the collection and storage area of ​​the electrostatic capture module, respectively. It is used to realize gas-liquid separation, bubble removal and directional transport of working fluid in a microgravity environment. A closed-loop pipeline connects the piezoelectric atomization module, the electrostatic capture module, and the microgravity circulation protection module, forming a closed-loop circulation path for the working fluid; The system controller is electrically connected to the piezoelectric atomization module, the electrostatic capture module, and the microgravity circulation protection module, and is used to coordinate and control the atomization parameters, electrostatic capture parameters, and circulation flow parameters according to the heat source temperature feedback signal to achieve adaptive thermal control; The liquid working fluid recovered by the electrostatic capture module is processed by the microgravity circulation protection module and then returned to the piezoelectric atomization module through the closed loop pipeline, forming a complete closed-loop circulation of the working fluid.

[0012] Preferably, the piezoelectric atomization module includes: A piezoelectric vibration unit includes a piezoelectric ceramic actuator and a resonant cavity. The piezoelectric ceramic actuator is fixedly disposed on the wall of the resonant cavity and is used to generate high-frequency ultrasonic vibration. A microporous atomizing grid is sealed at the nozzle of the resonant cavity. The microporous atomizing grid has an array of micropores and serves as a direct coupling component for piezoelectric vibration, used to break the working fluid into uniform droplets. The working fluid supply chamber is connected to the upstream end of the resonant cavity and is used to contain liquid cooling working fluid and supply liquid to the microporous atomizing grid. A phase controller, electrically connected to the piezoelectric ceramic actuator and communicatively connected to the system controller, is used to receive control commands from the system controller to adjust the frequency, amplitude, and waveform of the drive signal.

[0013] Preferably, the pore size of the micropores on the microporous atomizing grid is 5~30μm; the operating frequency of the piezoelectric ceramic actuator is 20kHz~2MHz, and the peak-to-peak driving voltage is 20~150Vpp; the average diameter of the atomized droplets generated by the piezoelectric atomizing module is 10~60μm, and the initial velocity of the droplet ejection is 0.5~5m / s.

[0014] Preferably, the electrostatic capture module includes: A charge application unit is disposed at the microporous atomizing grid of the piezoelectric atomization module to enable the spray droplets to carry a net charge when leaving the nozzle. The charge application unit has a built-in inductive charge electrode, which is fixedly attached to the outer periphery of the microporous atomizing grid. The inductive charge electrode is externally connected to a DC bias power supply line and electrically connected to the system controller to apply a DC bias voltage to the microporous atomizing grid, so that the sprayed droplets are charged upon contact and carry a net charge. The electrostatic field generating unit includes at least one set of opposing electrodes, which consists of an anode collecting plate and a cathode, and is fixedly disposed on the inner wall surface of the spray cavity to establish an electrostatic field inside the cavity. A liquid film guiding structure, covering the liquid-facing surface of the anode collecting plate, includes a porous capillary core layer and a hydrophilic coating, used to absorb, gather, and guide the electrostatically adsorbed droplets to the collection and storage area.

[0015] Preferably, the charging unit employs an inductive charging method, applying a DC bias voltage to the microporous atomizing grid of the piezoelectric atomizing module, causing the droplets ejected from the micropores to carry a net charge due to contact charging; the electric field strength of the electrostatic field generating unit is 0.5~5kV / cm, and the positive voltage applied to the anode collecting plate is in the range of +1kV~+10kV; the capillary wick of the liquid film guiding structure has an equivalent pore size of 1~50μm, and the hydrophilic coating is a hydrophilic surface modified with titanium oxide or aluminum oxide nanoparticles, with a contact angle of less than 30°.

[0016] Preferably, the microgravity cycle protection module includes: A capillary pump, with its inlet end connected to the collection and storage area and its outlet end connected to the reflux section of the closed-loop pipeline, includes a capillary core structure and a gas-liquid separation chamber. It is used to draw liquid working fluid from the collection and storage area to the reflux pipeline using capillary force, and to separate and discharge dissolved gas in the gas-liquid separation chamber. A bubble trapping structure is installed at a high point in the closed-loop pipeline to capture and remove free bubbles in the loop. A heat exchanger is located on the return path of the closed-loop pipeline and downstream of the capillary pump and upstream of the working fluid supply chamber. It is used to cool the recovered and heated working fluid to a set temperature before supplying it to the piezoelectric atomization module.

[0017] Preferably, the capillary core structure of the capillary pump adopts a stainless steel powder sintering and multi-layer composite wire mesh structure, and the capillary lifting height is not less than 200mm; the gas-liquid separation chamber is provided with a non-condensable gas exhaust port for connecting to the on-orbit exhaust system; the microgravity circulation protection module also includes a surface tension balancer, which is set on the closed loop pipeline and located upstream of the working fluid supply chamber, for maintaining liquid coverage at the liquid supply port under different gravity orientations.

[0018] Preferably, the microgravity circulation protection module further includes a microgravity liquid level sensing and control unit. The microgravity liquid level sensing and control unit has a built-in capacitive liquid level sensor and a differential pressure liquid level sensor. The capacitive liquid level sensor is respectively arranged in the collection and storage area and the working fluid supply chamber to detect the liquid level of the two internal working fluids. The differential pressure liquid level sensor is set between the inlet and outlet of the capillary pump and is used to determine the real-time liquid supply status based on the pressure difference between the two sides. All monitoring signals collected by this unit are fed back to the system controller.

[0019] Preferably, the closed-loop pipeline is further provided with a flow regulating valve and a pressure sensor, and the flow regulating valve, the pressure sensor and the temperature sensor located on the surface of the heat source to be cooled are all communicatively connected to the system controller.

[0020] Preferably, the flow regulating valve works in conjunction with the pressure sensor to achieve closed-loop feedback control, and the temperature sensor is used to provide real-time feedback of the heat source temperature signal to the system controller.

[0021] Technical effects and advantages of the present invention: The microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping proposed in this invention has the following advantages compared with the prior art: 1. Atomization performance is significantly better than existing mechanical pump drive solutions. This invention employs piezoelectric vibration atomization instead of the traditional high-pressure diaphragm pump + pressure nozzle solution, offering the following advantages: Excellent droplet uniformity: The Sauter droplet diameter generated by piezoelectric microporous atomization can reach 15~35μm, with a particle size distribution variance coefficient (CV) of less than 15%, far superior to the 50~200μm and CV value greater than 30% level of pressure atomization. The uniform and fine droplets increase the specific surface area per unit volume, significantly enhancing evaporative heat transfer and phase change heat transfer efficiency.

[0022] No high-pressure sealing required: Piezoelectric atomization can operate under near-normal pressure conditions (the working fluid supply pressure only needs to be 5~30kPa to overcome flow resistance), avoiding the leakage risk of high-pressure sealing structures and improving reliability in aerospace environments.

[0023] Low power consumption: The typical power consumption of piezoelectric actuators is only in the range of 1~10W, which is about 60%~80% lower than that of micro high-pressure diaphragm pumps (usually 20~50W or more), which helps to save the precious electrical energy resources of spacecraft.

[0024] No moving parts: The piezoelectric ceramic actuator only performs high-frequency vibrations at the micron level, with no rotating or reciprocating mechanical moving parts, eliminating mechanical wear problems and theoretically having a service life far exceeding that of a mechanical pump.

[0025] Rapid response and precise control: The start-stop response time of piezoelectric atomization is less than 10ms, and the atomization rate and droplet size can be precisely controlled by electrical parameters (frequency, voltage, waveform), providing a hardware foundation for realizing on-demand variable frequency heating control.

[0026] 2. First achievement of efficient active electrostatic droplet capture under microgravity environment This is one of the core innovations and greatest benefits of this invention. Compared with the passive mechanical interception / surface tension collection methods in the prior art, electrostatic capture has the following revolutionary advantages: Significantly improved capture efficiency: By rationally designing the electric field strength and droplet charge parameters, a droplet capture efficiency of over 98% can theoretically be achieved, far exceeding the approximately 70% level of existing passive collection methods. This means that the propellant loss rate can be controlled to below 2% per year, meeting the propellant retention requirements of long-life spacecraft (10-15 years of on-orbit service).

[0027] Unrestricted by microgravity: The basic principle of electrostatic trapping is Coulomb force ( Since it is independent of gravity, its collection ability will not degrade in a microgravity environment, which is a fundamental advantage compared to all gravity-dependent collection methods.

[0028] Active and controllable: The magnitude of the collecting force can be controlled in real time by adjusting the electrode voltage, adapting to different atomization flow conditions and achieving dynamic matching and coordination of "atomization-collection".

[0029] Low additional power consumption: The static power consumption after the electrostatic field is established is close to zero (only a trace of leakage current), and there is only microampere current when droplet deposition causes a current path. The total additional power consumption is usually less than 1W.

[0030] 3. A comprehensive microgravity circulation system ensures long-term stable operation of the system. The microgravity circulation protection module of this invention solves several microgravity-specific problems that are overlooked in existing solutions: active gas-liquid separation: through a dedicated capillary pump / separator combination unit, dissolved gas and entrained gas are effectively separated and discharged during the working fluid reflux process, preventing gas blockage from interfering with the normal operation of piezoelectric atomization and electrostatic capture.

[0031] Full-loop bubble management: The bubble trapping structure is set at key locations in the pipeline to actively capture and remove free bubbles in the loop. This is a microgravity fluid management design that has never been addressed in existing solutions.

[0032] Multi-degree-of-freedom attitude adaptability: The introduction of the surface tension balancer enables the system to maintain normal liquid supply under various gravity environments such as high overload in the launch phase, microgravity in orbit, and orbital maneuvers.

[0033] Intelligent coordinated control: The system controller integrates multi-dimensional sensing and control of thermal control loop, atomization loop, collection loop and circulation loop, realizing true adaptive thermal management.

[0034] 4. High heat flux density heat dissipation capacity Based on the above technological innovations, the thermal control performance indicators that the device of this invention is expected to achieve are as follows: Maximum heat flux density: ≥100W / cm² (when using fluorinated ethers such as FC-72), ≥300W / cm² (when using high latent heat working fluids such as ammonia or water); Heat source surface temperature control accuracy: ±2℃ (steady-state conditions); Total system mass (excluding working fluid): ≤3kg (for compact designs with 100W-class heat sources); Working fluid closed-loop circulation utilization rate: ≥95% (annual loss rate ≤2%); Designed on-orbit service life: ≥10 years.

[0035] In summary, this invention employs piezoelectric atomization instead of traditional mechanical pressure atomization, resulting in uniform droplets, near-normal pressure operation, low power consumption, no wear, and rapid control response, significantly improving heat exchange efficiency and on-orbit reliability. It innovatively uses electrostatic active droplet capture, relying on Coulomb force to avoid the influence of microgravity, achieving a capture efficiency exceeding 98% with extremely low additional power consumption, greatly reducing working fluid loss. A supporting microgravity circulation module enables gas-liquid separation, bubble collection, and stable liquid supply in multiple attitudes, while multiple sensors and controllers complete intelligent adaptive control throughout the entire process. The overall heat dissipation capability is outstanding, adaptable to ultra-high heat flux density heat sources, with high temperature control accuracy, lightweight equipment, and low working fluid loss, meeting the long-term on-orbit stable thermal control requirements of spacecraft for more than ten years. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the piezoelectric atomization module structure of the present invention; Figure 3 This is a schematic diagram of the electrostatic capture module structure of the present invention; Figure 4 This is a schematic diagram of the microgravity cycle protection module structure of the present invention; Figure 5 This is a flowchart of the microgravity spray cooling closed-loop heat dissipation method of the present invention.

[0037] In the diagram: 1. Piezoelectric atomization module; 11. Piezoelectric vibration unit; 111. Piezoelectric ceramic actuator; 112. Resonant cavity; 12. Microporous atomization grid; 13. Working fluid supply cavity; 14. Phase controller; 2. Electrostatic capture module; 21. Charge application unit; 211. Inductively charged electrode; 22. Electrostatic field generation unit; 221. Anode collecting plate; 222. Cathode; 23. Liquid film guiding structure; 231. Capillary core layer; 232. Hydrophilic coating; 3. Microgravity circulation protection module; 31. Capillary pump; 311. Capillary core structure; 312. Gas-liquid separation chamber; 32. Microgravity liquid level sensing and control unit; 33. Bubble capture structure; 34. Heat exchanger; 35. Surface tension balancer; 4. Closed loop pipeline; 5. Heat source to be cooled; 51. Temperature sensor; 6. Spray cavity; 7. Collection and storage area. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] This invention provides, for example Figure 1-5 A microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic capture includes a piezoelectric atomization module 1, an electrostatic capture module 2, a microgravity circulation protection module 3, a closed-loop pipeline 4, and a system controller. The device consists of five main parts: a piezoelectric atomization module 1, an electrostatic collection module 2, a microgravity circulation protection module 3, a closed-loop pipeline 4, and a system controller. The piezoelectric atomization module 1 and the electrostatic capture module 2 are both installed inside the spray chamber 6, while the microgravity circulation protection module 3 is arranged outside the spray chamber 6. The closed loop pipeline 4 connects the three major functional modules to form a complete working fluid circulation channel. The system controller is electrically connected to each module and can uniformly adjust the relevant parameters of atomization, electrostatic capture, and circulation flow based on the heat source temperature feedback signal to realize the adaptive thermal control operation of the equipment.

[0040] During operation, the liquid working fluid captured and collected by the electrostatic capture module 2 is first sent to the microgravity circulation protection module 3 to complete gas-liquid separation, pressure stabilization and flow regulation, and then flows back to the piezoelectric atomization module 1 through the closed loop pipeline 4, thereby constructing a leak-free and continuously operating closed cooling cycle.

[0041] The piezoelectric atomization module 1 is arranged facing the heat source 5 to be cooled. It relies on high-frequency piezoelectric vibration to tear the cooling working medium into micron-sized droplets and spray them onto the surface of the heat source for heat exchange. The piezoelectric atomization module 1 contains a piezoelectric vibration unit 11, a microporous atomization grid 12 and a working medium supply chamber 13, and is also equipped with a phase controller 14. The piezoelectric vibration unit 11 is equipped with a piezoelectric ceramic actuator 111 and a resonant cavity 112. The piezoelectric ceramic actuator 111 is fixed to the wall of the resonant cavity to generate high-frequency ultrasonic vibration. The piezoelectric vibration unit 11 consists of a ring-shaped piezoelectric ceramic actuator 111 and a resonant cavity 112. The piezoelectric ceramic actuator 111 is made of PZT lead zirconate titanate piezoelectric material, with an outer diameter of 20 mm, an inner diameter of 12 mm, and a thickness of 1 mm. It is bonded and fixed to the outer wall of the resonant cavity 112. The resonant cavity 112 is made of 304L or 316L stainless steel and is precision machined into a cylindrical thin-walled shell. The bottom opening of the cavity is sealed to the microporous atomizing grid 12, and the top pipeline is connected to the working fluid supply cavity 13.

[0042] The microporous atomizing grid 12 is sealed and installed at the nozzle position of the resonant cavity 112. The grid is covered with an array of micropores and directly coupled with piezoelectric vibration to break up the liquid working fluid. The microporous atomizing grid 12 is the core atomizing component of this device. It is made by laser drilling of a 50-100μm thick stainless steel sheet. The plate surface is arranged with a regular circular array of micropores. The micropore diameter is 15μm, the micropore center pitch is 80μm, and the overall porosity is about 3%. The total number of micropores is set to 5000-8000 according to the cross-sectional area of ​​the resonant cavity 112. The microporous atomizing grid 12 also serves as a piezoelectric vibration coupling component. When the piezoelectric ceramic actuator 111 excites the resonant cavity 112 to generate ultrasonic longitudinal vibration, the thin wall of the micropores undergoes micron-level high-frequency vibration, which continuously shears and stretches the liquid working fluid in the cavity, breaking it up into uniform microdroplets. This atomization form is vibration mesh atomization.

[0043] The working fluid supply chamber 13 is connected to the upstream of the resonant cavity 112 and is used to store the cooling working fluid and continuously supply liquid to the microporous atomizing mesh. The working fluid supply chamber 13 is arranged upstream of the resonant cavity 112 and connected to the liquid supply branch of the closed loop pipeline 4. The cavity is equipped with a baffle structure to eliminate fluid pulsation and ensure that the working fluid is stably delivered to the resonant cavity 112. The cavity volume is set at 5-10mL to play a buffering and stabilizing role.

[0044] In this application, the cooling medium selected is 3M FC-72 perfluorinated ether, suitable for electrostatic atomization conditions of the device: the volume resistivity of this medium is greater than... It has excellent insulation properties to prevent short circuits in electrostatic modules; its boiling point at normal pressure is 56℃, which is suitable for the normal operating range of spacecraft electronic devices from 0-85℃; its surface tension is about 10mN / m, which makes it easy to generate micro-atomized droplets; it has strong chemical inertness and is compatible with stainless steel, aluminum alloy, titanium alloy and other commonly used aerospace materials, and its ozone depletion potential value ODP=0, which meets the aerospace environmental protection standards.

[0045] The phase controller 14 communicates with the piezoelectric ceramic actuator 111 and the system controller, respectively, and can receive control commands and flexibly adjust the frequency, amplitude and waveform of the piezoelectric drive signal.

[0046] In this application, the micropore diameter of the microporous atomizing grid 12 is controlled between 5 and 30 μm, the piezoelectric ceramic actuator 111 operates in the frequency range of 20 kHz to 2 MHz, the peak-to-peak driving voltage is 20 to 150 Vpp, the average Sottle diameter of the atomized droplets is 10 to 60 μm, the initial velocity of the droplet jet is 0.5 to 5 m / s, and the atomization uniformity is excellent.

[0047] The electrostatic capture module 2 is arranged inside the spray chamber 6, downstream of the droplet flight area of ​​the piezoelectric atomization module 1. It actively adsorbs charged droplets and guides them back by relying on electrostatic field force. The electrostatic capture module 2 includes a charge application unit 21, an electrostatic field generation unit 22, and a liquid film guiding structure 23. The charge application unit 21 is assembled at the position of the microporous atomization grid 12. It has an induction charge electrode 211 inside. The electrode is attached and fixed to the outer periphery of the microporous atomization grid 12. It is connected to an external DC bias power supply line and electrically connected to the system controller. By applying a DC bias voltage to the grid, the sprayed droplets are charged upon contact and carry a net charge. The electrostatic capture module 2 is the core innovative component of this invention, which distinguishes it from existing microgravity spray cooling solutions. It can efficiently capture floating droplets in a zero-gravity environment and ensure closed-loop recycling of the working fluid.

[0048] The electrostatic capture module 2 comprises three main parts: a charge application unit 21, an electrostatic field generation unit 22, and a liquid film guiding structure 23. The structural arrangement is shown in the attached diagram. The charge application unit 21 employs an inductive charge scheme, applying a -200V to 1000V DC negative bias voltage to the microporous atomizing grid 12; in this embodiment, -500V is preferred. Upon ejection of the liquid working fluid, contact charge transfer occurs with the metal grid, and the droplets carry a positive charge. This scheme eliminates the need for additional discharge electrodes, resulting in a simplified structure and a single droplet charge-to-mass ratio of up to 10. -6 -10 -5 C / kg.

[0049] The electrostatic field generating unit 22 consists of a non-parallel opposing electrode composed of an anode collecting plate 221 and a grounded cathode 222, both of which are fixed to the inner wall of the spray cavity 6. The anode collecting plate 221 has a concave curved surface structure, facing the spray plume area, and is subjected to a +3kV positive high voltage. The remaining metal wall surface of the cavity serves as the grounded cathode 222. The electric field strength at the center of the cavity is about 1.5kV / cm, forming a non-uniform electrostatic field that converges towards the anode.

[0050] The liquid film guiding structure 23 fully covers the liquid-facing surface of the anode collecting plate 221 and has a double-layer structure: the inner layer is a capillary core layer 231, which is formed by sintering 3-5 layers of 400-mesh stainless steel wire mesh with a thickness of 0.5 mm and an equivalent pore size of 15 μm. It can quickly adsorb discrete droplets and form a continuous liquid film to prevent droplets from accumulating and falling off under microgravity; the outer layer is a nano-TiO2 sintered hydrophilic coating 232 with a particle size of 20 nm. The contact angle with the FC-72 working fluid is less than 5°, which enhances the liquid spreading and flow performance; the bottom end of the liquid film guiding structure 23 is connected to the collection and storage area 7, and the collected liquid is directionally transported to the storage area by capillary force and Marangoni effect.

[0051] The complete electrostatic capture process consists of four stages: ① During the charging stage, the droplets pass through the microporous atomizing grid 12 with a -500V bias voltage, and are charged upon contact, carrying 10 -14 -10 -13 C is a positive charge; ②Drifting stage: After the charged droplet with an initial velocity of about 2m / s hits the heat source, the remaining secondary droplet floats in the cavity at a low speed. ③ During the collection stage, the Coulomb electric field force drives the droplets to move toward the anode collecting plate 221 and is adsorbed by the liquid film guiding structure 23; ④ During the recovery stage, the adsorbent flows along the guide structure into the collection and storage area 7, completing the recovery of the liquid working fluid.

[0052] This application adopts an inductive charging mode. The electrostatic field generating unit 22 is equipped with one or more opposing electrodes, consisting of an anode collecting plate 221 and a cathode 222, which are fixed to the inner wall of the cavity. An electrostatic field with an intensity of 0.5 to 5 kV / cm can be established inside the cavity. The positive voltage applied to the anode collecting plate 221 is in the range of +1 kV to +10 kV. The liquid-facing surface of the anode collecting plate 221 is covered with a liquid film guiding structure 23, which is composed of a capillary core layer 231 and a hydrophilic coating 232. The equivalent pore size of the capillary core is 1 to 50 μm, and the coating is prepared by nano-modification of titanium dioxide and aluminum oxide. The water contact angle is less than 30°, which can quickly gather and guide the droplets captured by the plate to the collection and storage area 7.

[0053] The microgravity circulation support module 3 is connected to the working fluid supply chamber 13 and the collection and storage area 7 respectively. It is specially adapted to the microgravity environment in space to complete gas-liquid separation, bubble discharge and directional transport of working fluid. The microgravity circulation support module 3 includes a capillary pump 31, a bubble trapping structure 33, a heat exchanger 34, a surface tension balancer 35 and a microgravity liquid level sensor and control unit 32. The microgravity circulation support module 3 is a key support structure for the long-term stable operation of the entire device in orbit. It consists of five sub-units: capillary pump 31, microgravity liquid level sensing and control unit 32, bubble trapping structure 33, heat exchanger 34, and surface tension balancer 35.

[0054] The capillary pump 31 has an inlet connected to the liquid collection and storage system and an outlet connected to the closed-loop return pipeline. It integrates a capillary core structure 311 and a gas-liquid separation chamber 312. The capillary core is made of stainless steel powder sintered composite multi-layer wire mesh, with a capillary lifting height of no less than 200mm. The gas-liquid separation chamber has a reserved non-condensable gas exhaust port for docking with the spacecraft's on-orbit exhaust system. The capillary pump 31 relies on capillary force to draw in the liquid working fluid and simultaneously separates and discharges dissolved gases within the working fluid. As the core of the loop fluid transport, the capillary pump 31 combines liquid suction and gas-liquid separation functions. The capillary core structure 311 is a stainless steel powder sintered disc with a diameter of 30 mm, a thickness of 5 mm, a porosity of 40%, and an equivalent pore size of 8 μm. One end is immersed in the collection and storage area 7, and the working fluid is drawn in by capillary force. The FC-72 working fluid can be capillarily lifted to a height of 150 mm in a 1 g environment on Earth, and there is sufficient margin for delivery under microgravity conditions. Downstream is a 20 mL gas-liquid separation chamber 312. After the fluid flows in, the flow rate drops sharply, and the gas phase accumulates at the top of the chamber. The top is reserved with a non-condensable gas exhaust port, which can be connected to the spacecraft's on-orbit exhaust valve system.

[0055] The bubble trapping structure 33 is installed at the highest point of the closed loop pipeline 4 to specifically trap and discharge free bubbles in the pipeline. The bubble trapping structure 33 is installed at the highest point of the space in the closed loop pipeline 4, and is equipped with a 200-mesh stainless steel interception net inside. It allows liquid to flow and traps free bubbles. The bubbles gather in the top air bladder cavity and can be automatically discharged through the pressure sensor-linked micro exhaust valve.

[0056] The heat exchanger 34 is connected in series downstream of the capillary pump 31 and upstream of the working fluid supply chamber 13. It precools the working fluid after the reflux heating to the set temperature before supplying it to the atomization module. The heat exchanger 34 is connected in series downstream of the capillary pump 31 and upstream of the working fluid supply chamber 13. It adopts a plate-fin heat exchange structure and is coupled with the spacecraft's radiation cold source. It is designed to have a heat exchange power of 100-200W. It can cool the 45℃ high-temperature reflux working fluid to 25℃, keep the working fluid in a supercooled liquid state, and avoid flash boiling before atomization.

[0057] The surface tension balancer 35 is installed on the front end pipeline of the working propellant supply chamber 13. Under different gravity attitudes such as launch overload, on-orbit microgravity, and orbital maneuvering, it stably maintains the liquid surface coverage of the supply port. The surface tension balancer 35 is installed on the upstream pipeline of the working propellant supply chamber 13. The internal structure is composed of sponge titanium and stainless steel wire mesh to form a propellant management capillary structure. Under conditions of high launch overload, on-orbit microgravity, and variable acceleration during orbital maneuvering, it relies on surface tension to continuously maintain the liquid coverage of the pipeline outlet, ensuring uninterrupted and stable liquid supply.

[0058] The matching microgravity liquid level sensing and control unit 32 integrates a capacitive liquid level sensor and a differential pressure liquid level sensor. The capacitive sensor is arranged in the liquid collection and storage area 7 and the working fluid supply chamber 13 respectively to monitor the internal liquid volume in real time. The differential pressure sensor is connected across the inlet and outlet of the capillary pump 31 to determine the real-time liquid supply condition through the pressure difference between the two sides. All liquid level and differential pressure monitoring signals collected by the unit are uniformly transmitted back to the system controller.

[0059] The microgravity level sensing and control unit 32 abandons the float level gauge that fails in microgravity environments and uses two types of sensors for collaborative monitoring: capacitive level sensors are respectively arranged in the collection and storage area 7 and the working fluid supply chamber 13, which detect the level by utilizing the difference in dielectric constant between the working fluid and the vapor, with a range of 0-30mm and a resolution of 0.1mm; differential pressure level sensors are connected across the inlet and outlet of the capillary pump 31, and the capillary core supply and drying conditions are determined by the pressure difference between the two ends. All monitoring signals are transmitted to the system controller in real time.

[0060] Meanwhile, a flow regulating valve and a pressure sensor are also installed on the closed loop pipeline 4, and a temperature sensor 51 is installed on the surface of the heat source 5 to be cooled. The flow regulating valve, pressure sensor, and temperature sensor 51 are all connected to the system controller. The flow regulating valve, together with the pressure sensor, realizes closed-loop feedback regulation of pipeline flow. The temperature sensor 51 collects the temperature of the heat source in real time and uploads it to the system controller, providing temperature basis for the adaptive thermal control of the whole device.

[0061] The entire device integrates working fluid atomization, charged collection, microgravity circulation, and intelligent control into a complete closed-loop operation process. First, the system controller performs a self-test to confirm that all sensors are functioning normally and that the liquid levels in each chamber meet the requirements. Then, the electrostatic field generating unit 22 is activated, applying a rated positive high voltage (+3kV) to the anode collecting plate 221 and a negative bias voltage (-500V) to the microporous atomizing grid 12 to establish an electrostatic trapping field. Next, the heat exchanger 34 is started to begin pre-cooling of the working fluid. After the working fluid temperature drops to the set range, the piezoelectric atomization module 1—phase controller 14—outputs a 65kHz / 50Vpp sinusoidal excitation signal to the piezoelectric ceramic actuator 111, and the microporous atomizing grid 12 begins to generate a uniform spray of FC-22 droplets.

[0062] Stable operation phase: The FC-72 working fluid enters the resonant cavity 112 from the working fluid supply cavity 13. At the high-frequency vibrating microporous atomizing grid 12, it is broken into tiny droplets with an SMD of approximately 22 μm, which are then sprayed onto the surface of the heat source 5 to be cooled at a speed of approximately 2 m / s. The droplets spread into a thin liquid film on the heat source surface, rapidly absorbing heat through both forced convection heat transfer and nucleus boiling phase change heat transfer mechanisms. Some droplets splash after collision or evaporate upon heating and then re-condense; these "secondary droplets" float and move within the spray cavity 6.

[0063] Positively charged droplets (acquired through induced charging upon ejection) are electrostatically attracted by the anode collecting plate 221, overcoming the floating tendency of the microgravity environment, and adsorbed onto the surface of the liquid film guiding structure 23 covering the anode plate. The droplets are rapidly absorbed by the capillary core layer 231 and flow directionally along the surface of the superhydrophilic coating to the bottom collection reservoir 7.

[0064] The FC-72 liquid collected in the storage area 7 is drawn into the return pipeline by the capillary action of the capillary pump 31. During the process, the possible entrained air bubbles are removed by the bubble trapping structure 33, and then cooled to about 25°C by the heat exchanger 34. Finally, after the surface tension balancer 35 ensures continuous liquid supply, the liquid returns to the working fluid supply chamber 13, completing one closed cycle.

[0065] Throughout the operation, the system controller coordinates and adjusts the atomization amount and collection parameters in real time according to the changes in T_s to maintain the heat source temperature within the set range (e.g., 40±2℃).

[0066] Shutdown phase: The system controller first stops the piezoelectric atomization drive (the spray is immediately terminated), delays for 30-60 seconds (waiting for the residual droplets in the cavity to be fully captured by the electrostatic field), then turns off the electrostatic field, and finally shuts down the heat exchanger 34 and the auxiliary system.

[0067] The heat dissipation working principle of this application is as follows: S1: Piezoelectric atomizing agent spraying procedure The microporous atomizing grid 12 is driven by the piezoelectric vibration unit 11 to vibrate at high frequency, breaking the liquid cooling medium into a uniform droplet group with an average diameter of 1060 μm. The droplets are sprayed onto the surface of the heat source 5 to be cooled with an initial velocity of 0.55 m / s. The droplets spread on the surface of the heat source to form a thin liquid film and achieve efficient heat exchange through nucleation boiling and forced convection. S2: Droplet charging and electrostatic trapping steps This ensures that the ejected droplets carry a net charge (charge amount of 10) as they leave the nozzle. -6 10 -4 (on the order of C / kg), the charged droplets enter the electrostatic collection area with the spray airflow. Under the action of an electrostatic field with an electric field strength of 0.55kV / cm, they are actively adsorbed onto the surface of the anode collecting plate 221. The collected droplets are then gathered by the liquid film guiding structure 23 and flow into the collection storage area 7. S3: Microgravity Cycling Protection Procedures The liquid working fluid in the collection storage area 7 is drawn by the capillary pump 31. During the drawing process, gas-liquid separation and bubble discharge are achieved. Then, it is pre-cooled to the set temperature (preferably 5~15K below the working fluid saturation temperature) by the heat exchanger 34. The treated working fluid is returned to the working fluid supply chamber 13 of the piezoelectric atomization module 1 to complete one closed cycle. S4: Adaptive Coordination Control Steps The system controller adjusts the driving frequency and driving voltage of the piezoelectric atomization module 1 in real time to change the atomization flow rate based on the temperature signal fed back by the heat source surface temperature sensor 51. It also adjusts the electrode voltage of the electrostatic capture module 2 in sync to ensure that the capture efficiency matches the atomization flow rate. Furthermore, it adjusts the circulation flow rate based on the liquid level sensor signal to ensure the thermal balance and working fluid mass conservation of the system.

[0068] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping, characterized in that: include: The piezoelectric atomization module (1) is set inside the spray chamber (6) with the nozzle facing the surface of the heat source (5) to be cooled. It is used to break the liquid cooling medium into micron-sized uniform droplet groups using piezoelectric vibration energy and spray them onto the surface of the heat source (5) to be cooled. The electrostatic capture module (2) is disposed on the inner wall of the spray cavity (6) and located in the downstream region of the droplet flight path of the piezoelectric atomization module (1). It is used to actively adsorb, capture and guide the charged spray droplets through electrostatic field force. The microgravity circulation protection module (3) is located outside the spray chamber (6) and is connected to the working fluid supply chamber (13) of the piezoelectric atomization module (1) and the collection and storage area (7) of the electrostatic capture module (2) respectively. It is used to realize gas-liquid separation, bubble removal and directional transport of working fluid in a microgravity environment. A closed-loop pipeline (4) connects the piezoelectric atomization module (1), the electrostatic collection module (2), and the microgravity circulation protection module (3) to form a closed-loop circulation path for the working fluid. The system controller is electrically connected to the piezoelectric atomization module (1), the electrostatic capture module (2) and the microgravity circulation protection module (3), and is used to coordinate and control the atomization parameters, electrostatic capture parameters and circulation flow parameters according to the heat source temperature feedback signal to achieve adaptive thermal control; The liquid working fluid recovered by the electrostatic capture module (2) is processed by the microgravity circulation protection module (3) and then flows back to the piezoelectric atomization module (1) through the closed loop pipeline (4) to form a complete closed circulation of the working fluid.

2. The microgravity spray cooling closed-loop heat dissipation device based on the synergistic effect of piezoelectric atomization and electrostatic trapping as described in claim 1, characterized in that: The piezoelectric atomization module (1) includes: The piezoelectric vibration unit (11) includes a piezoelectric ceramic actuator (111) and a resonant cavity (112). The piezoelectric ceramic actuator (111) is fixedly disposed on the wall of the resonant cavity (112) and is used to generate high-frequency ultrasonic vibration. A microporous atomizing grid (12) is sealed at the nozzle of the resonant cavity (112). The microporous atomizing grid (12) has an array of micropores distributed on it, and the microporous atomizing grid (12) itself serves as a direct coupling component for piezoelectric vibration, used to break the working fluid into uniform droplets. The working fluid supply chamber (13) is connected to the upstream end of the resonant cavity (112) and is used to contain liquid cooling working fluid and supply liquid to the microporous atomizing grid (12); The phase controller (14) is electrically connected to the piezoelectric ceramic actuator (111) and communicatively connected to the system controller, and is used to receive control commands from the system controller to adjust the frequency, amplitude and waveform of the drive signal.

3. The microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping as described in claim 2, characterized in that: The micropore diameter on the microporous atomizing grid (12) is 5-30μm; the operating frequency of the piezoelectric ceramic actuator (111) is 20kHz-2MHz, and the peak-to-peak driving voltage is 20-150Vpp; the average diameter of the atomized droplets generated by the piezoelectric atomizing module (1) is 10-60μm, and the initial velocity of the droplet jet is 0.5-5m / s.

4. The microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping as described in claim 1, characterized in that: The electrostatic capture module (2) includes: A charge application unit (21) is disposed at the microporous atomizing grid (12) of the piezoelectric atomizing module (1) to enable the spray droplets to carry a net charge when leaving the nozzle. The charge application unit (21) has a built-in inductive charge electrode (211). The inductive charge electrode (211) is fixedly attached to the outer periphery of the microporous atomizing grid (12). The inductive charge electrode (211) is externally connected to a DC bias power supply line and electrically connected to the system controller to apply a DC bias voltage to the microporous atomizing grid (12) so that the sprayed droplets are charged upon contact and carry a net charge. The electrostatic field generating unit (22) includes at least one set of opposing electrodes, which consists of an anode collecting plate (221) and a cathode (222), and is fixedly disposed on the inner wall surface of the spray cavity (6) for establishing an electrostatic field inside the cavity; A liquid film guiding structure (23) covers the liquid-facing surface of the anode collecting plate (221), including a porous capillary core layer (231) and a hydrophilic coating (232), for absorbing, converging and guiding the electrostatically adsorbed droplets to the collection storage area (7).

5. The microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping as described in claim 4, characterized in that: The charge application unit (21) adopts an inductive charge method, applying a DC bias voltage to the microporous atomizing grid (12) of the piezoelectric atomizing module (1), so that the droplets ejected from the micropores carry a net charge due to contact charging; the electric field strength of the electrostatic field generating unit (22) is 0.5~5kV / cm, and the positive voltage applied by the anode collecting plate (221) is in the range of +1kV~+10kV; the capillary wick equivalent pore size of the liquid film guiding structure (23) is 1~50μm, and the hydrophilic coating (232) is a hydrophilic surface modified with titanium oxide or aluminum oxide nanoparticles, with a contact angle of less than 30°.

6. The microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping as described in claim 1, characterized in that: The microgravity circulation protection module (3) includes: The capillary pump (31) has its inlet end connected to the collection and storage area (7) and its outlet end connected to the reflux section of the closed loop pipeline (4). It includes a capillary core structure (311) and a gas-liquid separation chamber (312), which is used to draw the liquid working medium from the collection and storage area (7) to the reflux pipeline by using capillary force, and to separate and discharge the dissolved gas in the gas-liquid separation chamber (312). A bubble trapping structure (33) is set at a high point in the closed loop pipeline (4) to capture and discharge free bubbles in the loop; The heat exchanger (34) is located on the return path of the closed loop pipeline (4) and downstream of the capillary pump (31) and upstream of the working fluid supply chamber (13). It is used to cool the recovered and heated working fluid to a set temperature and then supply it to the piezoelectric atomizing module (1).

7. The microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping as described in claim 6, characterized in that: The capillary core structure (311) of the capillary pump (31) adopts a stainless steel powder sintering and multi-layer composite wire mesh structure, and the capillary lifting height is not less than 200mm; the gas-liquid separation chamber (312) is provided with a non-condensable gas exhaust port for connecting to the on-orbit exhaust system. The microgravity circulation protection module (3) also includes a surface tension balancer (35), which is installed on the closed loop pipeline (4) and located upstream of the working fluid supply chamber (13) to maintain the liquid coverage of the liquid supply port under different gravity orientations.

8. The microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping as described in claim 1, characterized in that: The microgravity circulation protection module (3) also includes a microgravity liquid level sensing and control unit (32). The microgravity liquid level sensing and control unit (32) has a built-in capacitive liquid level sensor and a differential pressure liquid level sensor. The capacitive liquid level sensor is arranged in the collection storage area (7) and the working fluid supply chamber (13) to detect the liquid level of the two internal working fluids. The differential pressure liquid level sensor is set between the inlet and outlet of the capillary pump (31) and is used to determine the real-time liquid supply status by relying on the pressure difference on both sides. All monitoring signals collected by this unit are fed back to the system controller.

9. The microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping as described in claim 1, characterized in that: The closed loop pipeline (4) is also equipped with a flow regulating valve and a pressure sensor. The flow regulating valve, the pressure sensor and the temperature sensor (51) located on the surface of the heat source to be cooled (5) are all connected to the system controller.

10. A microgravity spray cooling closed-loop heat dissipation device based on the synergy of piezoelectric atomization and electrostatic trapping as described in claim 9, characterized in that: The flow regulating valve works in conjunction with the pressure sensor to achieve closed-loop feedback control, and the temperature sensor (51) is used to provide real-time feedback of the heat source temperature signal to the system controller.

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