A multi-module cooperative two-phase flow evaporator assembly for microgravity environments

Abstract

The application discloses a multi-module cooperative two-phase flow radiator assembly for microgravity environment, and relates to the technical field of spacecraft thermal control, and aims to solve the problems that the existing evaporator faces under microgravity, such as bubble coalescence to form gas film, plug flow to cause flow pattern instability, and load step to cause transient dryout. The evaporator assembly comprises an evaporator body, an EHD electrode array integrated in the interior, an electrowetting control layer, an ultrasonic auxiliary breaking module and a PCM bubble stabilization layer. The EHD electrode array applies an electric field to drive the working fluid flow; the electrowetting control layer adjusts the contact angle to control the bubble behavior; the ultrasonic auxiliary breaking module breaks large bubbles into micro-bubbles and carries them away from the heating surface by the EHD flow field; and the PCM bubble stabilization layer absorbs transient overheating energy to provide a response time window for the electrowetting control layer. According to the application, through the deep cooperation of multiple modules, the critical heat flux density is increased to 180-200 W / cm2, and the dryout margin is expanded by 3-4 times, so that the application can be used in the heat dissipation system of a spacecraft such as a computing satellite.

Description

Technical Field

[0001] This invention relates to the field of spacecraft thermal control technology, and in particular to a multi-module cooperative two-phase flow heat dissipation evaporator assembly for microgravity environments. Background Technology

[0002] Currently, in the field of spacecraft thermal control, two-phase fluid circulation cooling technology utilizes the boiling phase change of the working fluid to remove heat, which is the main means to meet the cooling requirements of high heat flux density. As the core component of a two-phase flow cooling system, the performance of the evaporator directly determines the cooling capacity and reliability of the entire system. However, existing evaporator components face the following technical challenges in microgravity environments:

[0003] 1. Bubble coalescing to form an air film leads to a decrease in CHF. In a microgravity environment, the lack of gravity prevents bubbles from detaching naturally from the heating surface due to buoyancy. The bubbles generated by boiling coalesce on the heating surface to form a gas film, increasing the thermal resistance and significantly reducing the boiling critical heat flux density by 30-50%, severely limiting the heat dissipation capacity of the evaporator.

[0004] II. Slug flow leads to flow pattern instability and pressure oscillations Large bubbles formed by the coalescence of air bubbles in the evaporator flow channel can enter the downstream piping, creating slug flow and causing instability in the gas-liquid two-phase flow pattern. Slug flow can cause system pressure oscillations and cold plate surface temperature fluctuations over long distances, with temperature fluctuations reaching ±5K, severely affecting heat dissipation stability.

[0005] III. Load step leads to transient drying The chip load of a computing satellite is characterized by rapid step changes. When the load suddenly increases, the heat flux density of the evaporator heating surface rises instantaneously. The liquid cannot be replenished in time, causing localized drying of the heating surface, a sharp deterioration in heat transfer performance, and even chip burnout.

[0006] IV. Lack of multi-module collaborative evaporator design In existing technology research, individual technologies such as EHD pumping, electrowetting bubble control, capillary liquid reflux, and PCM thermal buffering have been studied and published. However, existing evaporator designs mostly focus on improving single technical features, lacking a systematic integration and synergistic design of multiple active and passive enhancement modules. The coupling effects and synergistic mechanisms between modules have not been fully utilized. Summary of the Invention

[0007] The technical problem this invention aims to solve is: how to integrate evaporator components into a multi-module design to collaboratively address three interrelated challenges under microgravity conditions: bubble coalescence to form a gas film, flow pattern instability caused by slug flow, and transient drying due to load jumps. Specifically, this includes: how to simultaneously integrate electric field driving, bubble behavior regulation, large bubble breakup, and thermal shock buffering functions within the evaporator component; and how to achieve performance leaps that cannot be achieved by a single module through the synergistic effect between the modules.

[0008] The present invention adopts the following technical solution: A multi-module cooperative two-phase flow heat dissipation evaporator assembly for microgravity environments includes: The evaporator body has internal working fluid channels and heating surfaces; An EHD electrode array, integrated inside the evaporator body, is used to apply an electric field to drive the flow of the working fluid. An electrowetting control layer, disposed on the heating surface side, is composed of an insulating dielectric layer and a hydrophobic coating, and is used to control the generation size and detachment frequency of bubbles by adjusting the voltage of the solid-liquid-gas three-phase contact angle. An ultrasonic-assisted breaking module is installed in the working fluid channel to emit ultrasonic waves to break large bubbles in the channel into microbubbles. The microbubbles are carried away from the heating surface by the directional flow established by the EHD electrode array. The PCM stabilizing layer, disposed on the wall of the evaporator body, is made of microencapsulated phase change material and is used to absorb transient overheating energy through phase change endothermic absorption, providing a response time window for the electrowetting control layer.

[0009] Furthermore, the EHD electrode array is composed of multiple layers of staggered metal electrodes with an electrode spacing of 0.5-2 mm, an applied voltage of 0-5 kV, and an electric field strength of 10-50 kV / m.

[0010] Furthermore, the EHD electrode array adopts one of the following arrangements: interdigitated electrode arrangement, spiral electrode arrangement, or concentric ring electrode arrangement.

[0011] Furthermore, the insulating dielectric layer of the electrowetting control layer has a thickness of 30-80 μm and is made of polyimide or silicon dioxide; the hydrophobic coating has a thickness of 3-10 μm and is made of Teflon or Cytop fluorinated polymer; the adjustable voltage range is 0-100V, and the bubble generation size is controlled to be less than 1 mm and the detachment frequency is greater than 100 Hz.

[0012] Furthermore, the ultrasonic-assisted breakup module operates at a frequency of 20-100kHz and a power of 10-100W, and is configured to break bubbles with a diameter greater than 2mm into microbubbles with a diameter less than 0.5mm.

[0013] Furthermore, it also includes a gradient aperture capillary wick structure, which is disposed on the heating surface side, with the aperture gradually changing from 50-100μm to 200-500μm along the fluid flow direction. This structure is used to enhance the liquid reflux under microgravity by superimposing the capillary driving force with the electric field driving force of the EHD electrode array.

[0014] Furthermore, the microcapsules of the PCM stabilizing layer have a diameter of 10-50 μm, a phase change temperature of 40-80℃, and a latent heat of phase change greater than 150 kJ / kg; the PCM stabilizing layer is incorporated into the working fluid at a mass fraction of 1-5%, or coated onto the wall of the evaporator body with a thickness of 0.5-2 mm.

[0015] Furthermore, the electrowetting control layer controls the bubble formation size and detachment frequency with a millisecond-level response speed, while the PCM bubble stabilizing layer absorbs transient thermal shock energy on a second-level time scale. When the load undergoes a step change, the PCM bubble stabilizing layer first absorbs the transient overheating energy, providing a 0.5-2 second response time window for the electrowetting control layer. Subsequently, the electrowetting control layer precisely adjusts the bubble behavior to restore steady state, and the two form a fast-slow collaborative control.

[0016] Furthermore, the working medium is one of R134a, R245fa, ammonia, deionized water, or perfluorinated carbon.

[0017] Furthermore, the evaporator assembly is used in a 100-kilowatt-level liquid cooling system for a computing satellite, and the local heat flux density of the heating surface is greater than 100W / cm².

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Significantly increased critical heat flux density: Through the active regulation of bubble behavior by the electrowetting control layer 3, the CHF is increased from about 100W / cm² in the existing evaporator to 160W / cm²; further, through the synergistic effect of the ultrasonic-assisted breaking module 4 and the EHD electrode array 2, large bubbles are broken into micro bubbles and then quickly carried away from the heating surface by the EHD directional flow, effectively preventing bubbles from coalescing and forming a gas film, and further increasing the CHF to 180-200W / cm², with an overall increase of 60-100%.

[0019] (2) Precise control of bubble behavior and prevention of drying: Through the fast-slow synergistic mechanism of electrowetting control layer 3 and PCM bubble stabilizing layer 6, PCM first absorbs transient overheating energy when the load increases, providing a response time window for electrowetting. Electrowetting then adjusts bubble behavior with millisecond-level response, expanding the drying margin by 3-4 times, and controlling the temperature fluctuation of the evaporator heating surface within ±0.5K to ±2K.

[0020] (3) Enhanced reliability of liquid reflux: The capillary driving force of the gradient aperture capillary core structure 5 is superimposed with the electric field driving force of the EHD electrode array 2. The two are in the same direction and jointly enhance the liquid reflux under microgravity, thereby increasing the liquid replenishment of the evaporator heating surface by about 30% and improving the reliability of liquid reflux under microgravity by 2-3 times.

[0021] (4) Overall performance leap brought about by multi-module synergy: This invention integrates five modules—EHD pumping, electrowetting control, ultrasonic disruption, PCM thermal buffer, and capillary wick reflux—into the evaporator assembly, forming a synergistic effect that cannot be achieved by simply stacking a single module. The synergy between ultrasonic disruption and EHD increases the EHD pumping efficiency by an additional 15-25%; the synergy between PCM and electrowetting reduces the temperature overshoot from ±3K to within ±0.5K. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the internal structure of the evaporator assembly of the present invention; Figure 2 This is a schematic diagram showing the gradual change in pore size of the gradient pore capillary core structure.

[0023] Figure reference numerals: 1-Evaporator body; 2-EHD electrode array; 3-Electrowetting control layer; 4-Ultrasonic-assisted breakup module; 5-Gradient pore size capillary wick structure; 6-PCM bubble stabilizing layer. Detailed Implementation

[0024] This invention provides a multi-module cooperative two-phase flow heat dissipation evaporator assembly for microgravity environments, the internal structure of which is as follows: Figure 1 As shown, the evaporator assembly includes an evaporator body 1, and an EHD electrode array 2, an electrowetting control layer 3, an ultrasonic-assisted breakup module 4, and a PCM bubble stabilizing layer 6 integrated within the evaporator body 1. As a further optimization, the evaporator assembly may also include a gradient pore size capillary wick structure 5. The core innovation of this invention lies in integrating four functional modules—electric field driving, bubble behavior regulation, large bubble breakup, and thermal shock buffering—within the same evaporator assembly. Through deep synergy between these modules, it solves the three major technical challenges faced by evaporators under microgravity environments: bubble coalescence, flow pattern instability, and transient drying.

[0025] The evaporator body 1 has a working fluid flow channel and a heating surface inside. In a microgravity environment, the working fluid absorbs heat from the chip on the heating surface and boils, generating bubbles. Due to the lack of gravity, the bubbles cannot detach naturally by buoyancy and tend to accumulate on the heating surface to form a gas film, which is the root cause of the evaporator's performance degradation.

[0026] The EHD electrode array 2, integrated inside the evaporator body 1, consists of multiple layers of staggered metal electrodes, such as... Figure 1As shown. Electrode materials can be conductive metals such as copper, gold, titanium, or aluminum. Electrode spacing can be 0.5mm, 1mm, or 2mm, with 1mm being preferred. The selection of electrode spacing is based on the following: too small a spacing (less than 0.5mm) easily leads to dielectric breakdown between electrodes, causing short-circuit failure; too large a spacing (greater than 2mm) results in insufficient electric field strength, failing to generate enough volumetric driving force to drive the working fluid flow. Within the preferred range of 0.5-2mm, the best balance between safety and driving efficiency can be achieved. When applying a voltage of 0-5kV, such as 3kV, an electric field strength of 10-50kV / m can be generated between the electrodes, such as 30kV / m. The selection of the applied voltage is based on the following: when the voltage is below 1kV, the generated electric field strength is insufficient to drive the working fluid to overcome flow channel resistance, failing to establish effective flow; when the voltage is above 5kV, power consumption increases dramatically and higher requirements are placed on the insulation between electrodes, which is not advantageous under the limited power supply conditions of spacecraft. The electric field acts directly on the free charges in the working fluid, generating volume forces that drive the working fluid to flow directionally along the flow channel at velocities of 0.5-2 m / s. Driving the working fluid flow via electric field eliminates the need for any moving parts inside the evaporator, making it perfectly suited to microgravity environments and avoiding the bearing lubrication and wear problems of traditional mechanical pumps under microgravity. As an alternative, the EHD electrode array 2 can also employ an interdigitated electrode arrangement, a spiral electrode arrangement, or a concentric ring electrode arrangement. In the interdigitated electrode arrangement, the interdigitation width is 0.2-0.5 mm, the interdigitation spacing is 0.5-1.5 mm, and a voltage of 1-4 kV is applied to generate a non-uniform electric field to enhance local working fluid driving. In the spiral electrode arrangement, titanium electrodes are spirally wound along the flow channel wall with a pitch of 5-15 mm, and a voltage of 2-5 kV is applied to generate a rotating electric field within the flow channel. In the concentric ring electrode arrangement, concentric ring-shaped aluminum electrodes are arranged above the circular heating surface with a ring spacing of 1-3 mm, and a voltage of 0.5-3 kV is applied to generate a radial electric field that drives the bubbles to move from the center to the edge. All of the above-mentioned variant arrangements can achieve the basic function of driving the working fluid flow in EHD, and each has its own applicable advantages depending on the evaporator geometry and flow channel design.

[0027] Electrowetting control layer 3 is disposed on the heating surface side and consists of an insulating dielectric layer and a hydrophobic coating, such as... Figure 1As shown. The insulating dielectric layer can be made of polyimide or silicon dioxide with a thickness of 30-80 μm, preferably 50 μm; the hydrophobic coating can be made of Teflon or Cytop fluorinated polymer with a thickness of 3-10 μm, preferably 5 μm. The selection criteria for the thickness of the insulating dielectric layer are: when the thickness is less than 30 μm, the insulation strength is insufficient, and there is a risk of breakdown when voltage is applied; when the thickness is greater than 80 μm, the voltage drop on the dielectric layer is too large, weakening the effective electric field acting on the solid-liquid-gas three-phase interface and reducing the sensitivity to control the contact angle. The selection criteria for the thickness of the hydrophobic coating are: when the thickness is less than 3 μm, the uniformity and durability of the coating are difficult to guarantee, and local peeling may occur during long-term operation; when the thickness is greater than 10 μm, the presence of the coating will increase the thermal resistance and affect the heat transfer efficiency of the heating surface to the working fluid. By adjusting the voltage at the solid-liquid-gas three-phase contact angle from 0-100V, such as 60V or 80V, the selection of this voltage range is based on the fact that applying a voltage below 100V can establish a sufficient electric field on both sides of the insulating dielectric layer, effectively changing the surface energy of the hydrophobic coating (such as Teflon), and causing the contact angle to change from approximately 120° (hydrophobic state) to approximately 60° (hydrophilic state). This allows for effective control of bubble behavior without requiring higher voltages, balancing control effectiveness and power consumption. The contact angle can be changed from 120° (hydrophobic state) to 60° (hydrophilic state), controlling the bubble formation size to be less than 0.8mm and the detachment frequency to reach 150Hz with a millisecond-level response speed. This bubble behavior control mechanism fundamentally inhibits bubble coalescence on the heating surface under microgravity, preventing gas film formation, thereby increasing the boiling critical heat flux (CHF) from approximately 100W / cm² to 160W / cm², an increase of 60%.

[0028] The ultrasonic-assisted breakup module 4 is installed within the working fluid channel to address the problem of bubble coalescence and slug flow. This module operates within a frequency range of 20-100kHz, with options for 40kHz, 60kHz, or 80kHz; and its power ranges from 10-100W, with options for 30W or 50W. The selection of the operating frequency is based on the following: the 20-100kHz band matches the resonant frequency of target bubbles larger than 2mm in diameter, enabling the stimulation of a strong cavitation effect and achieving efficient bubble breakup; if the frequency is too low (below 20kHz), the cavitation threshold increases, and the breakup efficiency decreases significantly; if the frequency is too high (above 100kHz), the resonant radius of the cavitation bubble is too small, failing to effectively break up large bubbles larger than 2mm in diameter. The power selection criteria are as follows: the power must be matched according to the amount of bubbles to be broken in the flow channel. 10W can meet the basic breaking requirements under low gas content conditions, while 100W can handle large-scale bubble breaking under high gas content or slug flow conditions. If the power is too low, the breaking will be incomplete, while if the power is too high, it will increase the system energy consumption and may cause unnecessary vibration to the evaporator structure. When slug flow bubbles with a diameter greater than 2mm appear in the flow channel, the ultrasonic waves break them into microbubbles with a diameter less than 0.3mm within 0.1 seconds, increasing the heat transfer coefficient from about 5000W / (m²·K) to 7500W / (m²·K), an increase of 30-50%.

[0029] The ultrasonic-assisted fragmentation module 4 and the EHD electrode array 2 form a core first synergistic effect. In a microgravity environment, large bubbles in the flow channel significantly increase flow resistance and disrupt the electric field distribution, reducing the driving efficiency of the EHD. After the ultrasonic-assisted fragmentation module 4 breaks bubbles larger than 2 mm in diameter into microbubbles smaller than 0.5 mm in diameter, the uniformity of the gas-liquid two-phase flow in the flow channel is significantly improved, the microbubbles respond more uniformly to the electric field, and the liquid flow resistance driven by the EHD volume force is reduced by about 20%. More importantly, the directional flow established by the EHD electrode array 2 quickly carries the ultrasonically fragmented microbubbles away from the heating surface, preventing the microbubbles from re-aggregating and forming a gas film within 0.5 seconds. The synergistic effect of the two increases the EHD pumping efficiency by an additional 15-25%, and together they further increase the CHF from 160 W / cm² controlled by electrowetting alone to 180-200 W / cm².

[0030] The PCM foam stabilizing layer 6 is disposed on the wall of the evaporator body 1, and is made of microencapsulated phase change material, such as... Figure 1As shown. The phase change material can be paraffin, fatty acids, or low-melting-point metal alloys (such as Wood's alloy, with a melting point of approximately 70°C). The microcapsule diameter is 10-50 μm, preferably 20 μm; the phase change temperature is 40-80°C, preferably 60°C; and the latent heat of phase change is greater than 150 kJ / kg, preferably 200 kJ / kg. The selection of the microcapsule diameter is based on the following: when the diameter is less than 10 μm, the amount of phase change material encapsulated in a single microcapsule is too small, and the total latent heat capacity is insufficient to effectively absorb transient thermal shock energy; when the diameter is greater than 50 μm, the dispersion stability of the microcapsules in the working fluid decreases, making them prone to aggregation and sedimentation, and they may rupture due to mechanical collisions during flow, leading to leakage of the phase change material. The phase change temperature is selected based on the following criteria: a phase change temperature window of 40-80℃ precisely covers the overheating risk range of the evaporator wall—this temperature is higher than the saturation temperature of the working fluid R134a under typical system operating pressure (approximately 30-50℃), ensuring that the PCM only undergoes phase change under overheating conditions, without affecting normal operation; at the same time, it is far below the upper limit of the chip junction temperature protection (typically 85-105℃), enabling heat absorption buffering before the chip temperature reaches a dangerous level. The latent heat of phase change greater than 150kJ / kg is selected based on the following criteria: sufficient latent heat per unit mass is required to provide sufficient total heat capacity with a limited amount of microcapsule incorporation, effectively absorbing the transient overheating energy generated by load step changes. There are two implementation methods for the PCM stabilizing layer 6: one is to incorporate microcapsules into the working fluid at a mass fraction of 1-5% (e.g., 3%); the other is to mix PCM microcapsules with a thermally conductive adhesive and then coat them onto the evaporator wall with a coating thickness of 0.5-2mm. The selection criteria for the doping mass fraction are as follows: when the mass fraction is less than 1%, the total heat capacity of the PCM microcapsules is insufficient, the thermal buffering effect is not obvious, and it cannot provide enough response time for the electrowetting control layer; when the mass fraction is greater than 5%, the excessive microcapsule content will affect the flow characteristics and heat transfer performance of the working fluid, increasing the risk of flow channel blockage. The selection criteria for the coating thickness are as follows: when the thickness is less than 0.5 mm, the total latent heat capacity of the PCM layer is limited, and the buffering capacity is insufficient; when the thickness is greater than 2 mm, the thermal resistance of the PCM layer increases significantly, reducing the heat transfer efficiency of the evaporator wall to the working fluid, and the coating is prone to cracking and peeling during thermal cycling due to the difference in expansion and contraction.

[0031] The PCM bubble stabilizing layer 6 and the electrowetting control layer 3 form a fast-slow synergistic bubble control mechanism, which is another core innovation of this invention. The electrowetting control layer 3 controls the bubble generation size and detachment frequency with a millisecond-level response speed by dynamically adjusting the solid-liquid-gas three-phase contact angle. The PCM bubble stabilizing layer 6 absorbs transient thermal shock energy on a second-level timescale by utilizing the phase change endothermic characteristics of the microencapsulated phase change material. When the computing power load increases from 50 W / cm² to 150 W / cm², the PCM bubble stabilizing layer 6 first passively absorbs the transient overheating energy within 0.3 seconds, providing the electrowetting control layer 3 with a response time window of about 1 second. The formation of this response time window is based on the fact that the PCM microcapsules complete the solid-liquid phase change and absorb most of the overheating energy within 0.3 seconds, causing the wall surface temperature rise rate to decrease from about 10 K / s without PCM to about 2 K / s, providing the electrowetting control layer with a buffer time of 0.5-2 seconds, which is sufficient for the electrowetting control layer to complete the dynamic adjustment of the contact angle. The electrowetting control layer 3 then adjusts the contact angle from 120° to 70°, restoring the bubble formation process to a steady state. The fast-slow synergistic control mechanism of both increases the drying margin by 3-4 times from the extended effect of a single technology, and reduces the temperature overshoot from ±3K to within ±0.5K.

[0032] As a further enhanced technical solution, the gradient pore size capillary wick structure 5 is disposed on the heating surface side, and its pore size gradient structure is as follows: Figure 2As shown, the capillary wick structure features a pore size that gradually transitions from 50-100 μm (e.g., 80 μm) to 200-500 μm (e.g., 300 μm) along the fluid flow direction. It is manufactured using sintered copper powder or metal mesh, with a porosity of 60-70%. The selection of the pore size transition direction is based on the following: the evaporation end (closer to the heating surface) uses a large pore size of 200-500 μm, which effectively reduces the flow resistance of the liquid at the evaporation end, allowing the replenished liquid to reach the heating surface more smoothly; the condensation end (away from the heating surface) uses a small pore size of 50-100 μm, which can provide capillary pressure up to 5000 Pa, forming a strong capillary driving force from the condensation end to the evaporation end. The selection of a porosity of 60-70% is based on the following: when the porosity is below 60%, the flow resistance increases, and the liquid permeability is insufficient; when the porosity is above 70%, the mechanical strength of the capillary wick decreases, and the effective thermal conductivity decreases, affecting the efficiency of heat transfer from the heating surface to the working fluid. The large pore size at the evaporation end reduces liquid flow resistance, while the small pore size at the condensation end provides high capillary pressure, forming a capillary reflux driving force from the condensation end to the evaporation end. This structure generates a capillary driving force of up to 5000 Pa, 50% higher than that of a uniform pore size capillary wick. This improvement is achieved because in a uniform pore size capillary wick, capillary pressure and flow resistance are determined by the same pore size, resulting in an inherent trade-off. The gradient pore size structure breaks this trade-off, optimizing flow resistance with a large pore size and capillary pressure with a small pore size, thus increasing the overall driving capacity by 50%. The gradient pore size capillary wick structure 5 and the EHD electrode array 2 form a synergistic enhanced liquid reflux mechanism. The capillary driving force provided by the capillary wick, approximately 5000 Pa, is aligned with the volumetric driving force provided by the EHD electric field. The combined effect increases the liquid replenishment to the evaporator heating surface by approximately 30% and expands the drying margin by 2-3 times.

[0033] Explanation of the synergistic effect of each module The core innovation of this invention lies in integrating the EHD electrode array 2, the electrowetting control layer 3, the ultrasonic-assisted breakup module 4, and the PCM bubble stabilizing layer 6 into the same evaporator assembly. Through deep coupling between these modules, a multi-physics synergistic enhancement mechanism is formed, achieving a leap in the overall performance of the evaporator. The synergistic effects between the modules are explained in detail below:

[0034] (1) Synergistic effect of ultrasonic-assisted fragmentation and EHD pumping In microgravity environments, large air bubbles within the evaporator channel significantly increase flow resistance and disrupt the electric field distribution, reducing the driving efficiency of the EHD. The ultrasonic-assisted fragmentation module 4 breaks bubbles larger than 2 mm in diameter into microbubbles smaller than 0.5 mm, significantly improving the uniformity of the gas-liquid two-phase flow within the channel. The microbubbles respond more uniformly to the electric field, significantly enhancing the stability of the liquid flow driven by the volume forces of the EHD. Simultaneously, the directional flow established by the EHD electrode array 2 rapidly carries the ultrasonically fragmented microbubbles away from the heating surface, preventing them from re-aggregating and forming a gas film near the heating surface. The synergistic effect of these two mechanisms increases the EHD pumping efficiency by 15-25%, raising the CHF from approximately 100 W / cm² to 180-200 W / cm².

[0035] (2) Synergistic effect of electrowetting control and PCM foam stabilizing layer The electrowetting control layer 3 dynamically adjusts the solid-liquid-gas three-phase contact angle to control the bubble formation size and detachment frequency with a millisecond-level response speed. The PCM bubble stabilizing layer 6 absorbs transient thermal shock energy on a second-level timescale through the phase change endothermic characteristics of the microencapsulated phase change material. When the computing load undergoes a step change, the PCM bubble stabilizing layer 6 first absorbs the transient overheating energy, providing a 0.5-2 second response time window for the electrowetting control layer 3. The electrowetting control layer 3 then precisely regulates the bubble behavior, restoring the bubble formation process to a steady state. This fast-slow collaborative control mechanism expands the drying margin by 3-4 times and reduces the temperature overshoot from ±3K to within ±0.5K.

[0036] (3) Synergistic effect of gradient aperture capillary core and EHD pumping The gradient-aperture capillary wick structure 5 features pore sizes that gradually transition from 50-100 μm to 200-500 μm along the fluid flow direction. The larger pore size at the evaporation end reduces liquid flow resistance, while the smaller pore size at the condensation end provides high capillary pressure, creating a capillary reflux driving force from the condensation end to the evaporation end. The electric field volume driving force provided by the EHD electrode array 2 and the capillary force of the capillary wick have a superimposed effect, with both driving in the same direction, jointly enhancing liquid reflux under microgravity conditions. Under microgravity conditions, capillary force alone may not be sufficient to overcome flow resistance; the supplementary EHD driving force ensures continuous and stable liquid reflux to the evaporation end. The synergistic effect of both expands the critical heat flux density for drying by 2-3 times.

[0037] The working fluid selection of this invention has broad adaptability, and can be selected from R134a, R245fa, ammonia, deionized water, or perfluorinated carbon working fluids (such as FC-72) according to different temperature ranges and scenarios. R134a is suitable for medium-temperature heat dissipation scenarios from room temperature to 60°C; R245fa is suitable for medium-high temperature scenarios from 60-100°C; ammonia is suitable for wide temperature range scenarios from -30°C to 80°C and has a large latent heat (approximately 1300 kJ / kg); deionized water is suitable for high-temperature scenarios from 100-150°C; FC-72 is suitable for scenarios with extremely high heat flux density, has a high dielectric constant, and good coupling effect with the EHD electric field. Those skilled in the art can flexibly select the working fluid according to actual needs and adjust parameters such as EHD electric field strength, electrowetting voltage, ultrasonic frequency, and PCM phase transition temperature accordingly.

[0038] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of 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 scope of protection of the present invention.

Claims

1. A multi-module collaborative two-phase flow heat dissipation evaporator assembly for microgravity environments, characterized in that, include: The evaporator body (1) has a working fluid flow channel and a heating surface inside; EHD electrode array (2), integrated inside the evaporator body (1), is used to apply an electric field to drive the working fluid flow; An electrowetting control layer (3) is disposed on the heating surface side and is composed of an insulating dielectric layer and a hydrophobic coating. It is used to control the generation size and detachment frequency of bubbles by adjusting the voltage of the solid-liquid-gas three-phase contact angle. The ultrasonic-assisted breaking module (4) is set in the working fluid channel and is used to emit ultrasonic waves to break large bubbles in the channel into micro bubbles. The micro bubbles are carried away from the heating surface under the directional flow established by the EHD electrode array (2). The PCM stabilizing layer (6) is disposed on the wall of the evaporator body (1) and is made of microencapsulated phase change material. It is used to absorb transient overheating energy through phase change heat absorption and to provide a response time window for the electrowetting control layer (3).

2. The evaporator assembly according to claim 1, characterized in that, The EHD electrode array (2) consists of multiple layers of staggered metal electrodes with an electrode spacing of 0.5-2 mm, an applied voltage of 0-5 kV, and an electric field strength of 10-50 kV / m.

3. The evaporator assembly according to claim 1, characterized in that, The EHD electrode array (2) adopts one of the following: interdigitated electrode arrangement, spiral electrode arrangement, or concentric ring electrode arrangement.

4. The evaporator assembly according to claim 1, characterized in that, The insulating dielectric layer of the electrowetting control layer (3) has a thickness of 30-80μm and is made of polyimide or silicon dioxide; the hydrophobic coating has a thickness of 3-10μm and is made of Teflon or Cytop fluorinated polymer; the voltage adjustment range is 0-100V, and the bubble generation size is controlled to be less than 1mm and the detachment frequency is greater than 100Hz.

5. The evaporator assembly according to claim 1, characterized in that, The ultrasonic-assisted breakage module (4) operates at a frequency of 20-100kHz and a power of 10-100W, and is configured to break bubbles with a diameter greater than 2mm into microbubbles with a diameter less than 0.5mm.

6. The evaporator assembly according to claim 1, characterized in that, It also includes a gradient aperture capillary wick structure (5), which is set on the heating surface side. The aperture gradually changes from 50-100μm to 200-500μm along the fluid flow direction. It is used to enhance the liquid reflux under microgravity by superimposing the capillary driving force with the electric field driving force of the EHD electrode array (2).

7. The evaporator assembly according to claim 1, characterized in that, The microcapsule diameter of the PCM stabilizing layer (6) is 10-50 μm, the phase change temperature is 40-80℃, and the latent heat of phase change is greater than 150 kJ / kg; the PCM stabilizing layer (6) is incorporated into the working fluid at a mass fraction of 1-5%, or coated on the wall of the evaporator body (1) with a thickness of 0.5-2 mm.

8. The evaporator assembly according to claim 1, characterized in that, The electrowetting control layer (3) controls the generation size and detachment frequency of bubbles with a millisecond-level response speed. The PCM bubble stabilizing layer (6) absorbs transient thermal shock energy with a second-level time scale. When the load undergoes a step change, the PCM bubble stabilizing layer (6) first absorbs the transient overheating energy, providing a 0.5-2 second response time window for the electrowetting control layer (3). Subsequently, the electrowetting control layer (3) precisely adjusts the bubble behavior to restore steady state. The two form a fast-slow collaborative control.

9. The evaporator assembly according to claim 1, characterized in that, The working medium is one of R134a, R245fa, ammonia, deionized water, or perfluorinated carbon.

10. The evaporator assembly according to claim 1, characterized in that, The evaporator assembly is used in the 100-kilowatt-level liquid cooling system of the computing satellite, and the local heat flux density of the heating surface is greater than 100W / cm².

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