A composite molding method for embedded fins of phase change energy storage units

Abstract

The present invention relates to the field of phase change energy storage thermal management technology, and in particular to a composite molding method for embedded fins in a phase change energy storage unit. The method includes the following steps: Step 1: fractal interface crystallization point strengthening; Step 2: dynamic taper filling, constructing a tapered mold cavity with an inlet cross-sectional area larger than the outlet cross-sectional area. The taper ratio is calculated and determined using the phase change material's melt viscosity curve and a non-Newtonian fluid dynamics model; Step 3: multi-stage pressure control, controlling the injection pressure of the molten phase change material in three stages; and Step 4: magnetic field-oriented crystallization, applying a rotating magnetic field near the phase change material's crystallization point. The magnetic field intensity is calculated and determined based on the magnetization intensity-temperature curve of magnetic nano-additives, causing the additives to be oriented and arranged into thermally conductive chains. Through innovative design and optimization techniques, the thermal performance and reliability of the phase change energy storage unit under extreme operating conditions are significantly improved, providing an efficient and stable solution for spacecraft thermal control systems.

Description

Technical Field

[0001] The present invention relates to the technical field of phase change energy storage thermal management, and in particular to a composite molding method for embedded fins of a phase change energy storage unit. Background Art

[0002] Phase change energy storage technology, leveraging the latent heat properties of phase change materials (PCMs) to efficiently store and release heat in fluctuating temperature environments, has become a key technological solution to addressing the spatiotemporal mismatch between energy supply and demand. This technology holds particular value in the thermal management of aerospace electronics. Spacecraft electronics compartments face unique operating conditions such as extreme temperature fluctuations (-40°C to 120°C), high-frequency mechanical vibrations (up to 10g acceleration), and strict mass constraints. Conventional thermal control systems struggle to meet the cooling requirements of intermittent, high-power devices. Embedded fin-phase change material composite structures, by expanding the heat transfer area and providing a heat conduction path, are recognized as an effective solution for improving the thermal response rate of phase change units and have been widely adopted in spacecraft thermal management systems.

[0003] However, existing fin-PCM composite structure manufacturing technology has exposed a series of key technical bottlenecks when applied to aerospace scenarios. This has led to problems such as thermal performance degradation and structural failure of phase-change energy storage units during actual service. These issues have severely restricted the reliable application of phase-change energy storage technology in aerospace thermal control systems, necessitating breakthrough innovations in manufacturing processes.

[0004] In traditional manufacturing processes, there is a significant interfacial thermal resistance between the metal fins and the PCM, which is the core issue affecting the energy storage efficiency of the composite unit. Under the frequent thermal cycling conditions of spacecraft, the metal (such as aluminum alloy) and the organic PCM (such as paraffin) have different thermal expansion coefficients (about 23×10 -6 / K, PCM about 120×10 -6 / K) generates cyclic thermal stress, leading to the formation and expansion of microgaps at the interface. Studies have shown that after 200 thermal cycles from -40°C to 120°C, the interfacial contact thermal resistance increases by more than 30%, significantly reducing heat transfer efficiency.

[0005] This problem is particularly acute in aerospace applications: spacecraft experience approximately 16 extreme temperature fluctuations per day during on-orbit operation, resulting in over 5,000 thermal cycles per year. Traditional mechanical bonding processes are unable to adapt to these extreme conditions. Interfacial microgaps continue to expand with increasing cycles, ultimately leading to "thermal isolation"—the formation of an air gap between the fins and the PCM, which reduces the equivalent thermal conductivity to below 0.1 W / (m·K), reducing the energy storage efficiency of the phase change unit by over 40%.

[0006] Furthermore, existing PCM filling processes (such as vacuum infusion and gravity casting) are prone to creating air pockets and unfilled areas within the micro-fin gaps, reducing the effective heat transfer area. Especially when the fin spacing is less than 1 mm, the PCM's molten viscosity (paraffin wax, approximately 0.03 Pa·s) combined with capillary forces creates flow resistance, leading to air pockets as high as 5% to 8%. These gaps create localized thermal insulation, hindering heat transfer to areas away from the fins.

[0007] This issue poses a particular threat in the cooling of aerospace electronic equipment: the uneven distribution of heat sources within the equipment cabin requires isotropic thermal conductivity in the phase change unit. However, filling defects disrupt the heat conduction path, causing significant phase change lag in PCM regions farther from the fins. Experimental data shows that under pulsed heat loads with a power density greater than 1 W / cm², the temperature response delay in the defective region can exceed 120 seconds, leading to the risk of localized overheating (hotspot temperatures exceeding the specified limit by 15°C), directly threatening the safety of onboard electronic equipment.

[0008] Therefore, there is an urgent need to develop a composite molding method for embedded fins of phase change energy storage units to solve the above problems. Summary of the Invention

[0009] Based on the above objectives, the present invention provides a composite molding method for an embedded fin of a phase change energy storage unit, comprising:

[0010] Step 1: Fractal interface crystallization point strengthening: laser microtexturing is used to generate fractal dendritic grooves on the fin surface. The groove depth is determined by iterative calculation of the interface thermal stress simulation model based on the thermal expansion coefficient and curing shrinkage rate data of the phase change material.

[0011] Step 2: Dynamic taper filling: Construct a tapered mold cavity with an inlet cross-sectional area larger than the outlet cross-sectional area. The taper ratio is determined by the melt viscosity curve of the phase change material and the non-Newtonian fluid dynamics model.

[0012] Step 3: Multi-stage pressure control, which controls the injection pressure of the molten phase change material in three stages: in the first stage, the pressure is maintained higher than the set multiple of the saturated vapor pressure; in the second stage, the pressure is increased to the microbubble elimination threshold when the filling front reaches the set position in the cavity; in the third stage, reverse suction pressure is applied when the filling volume reaches the set threshold;

[0013] Step 4: Magnetic field oriented crystallization: a rotating magnetic field is applied near the crystallization point of the phase change material. The magnetic field strength is determined based on the magnetization intensity-temperature curve of the magnetic nano-additives, so that the additives are oriented to form thermal conductive chains.

[0014] Preferably, when generating the fractal branched grooves in step 1, the fractal dimension is optimized in the following manner:

[0015] collecting a scanning electron microscope image of the laser-processed groove, extracting self-similarity features of the branch structure, and calculating the fractal dimension based on the self-similarity features;

[0016] A correlation model between fractal dimension and interface bonding strength was established. By inputting the spacecraft vibration spectrum load into the finite element simulation model, the interface bonding strength under different fractal dimensions was predicted.

[0017] The interface peeling area of ​​samples with different fractal dimensions under a set acceleration spectrum was measured by vibration table test.

[0018] A fractal dimension range is selected that makes the peeling area below a critical threshold. The critical threshold is determined by the bonding strength distribution of the unpeeled area through micro-CT scanning. The interface bonding strength predicted by the correlation model and the vibration table test results are mutually verified and used together to determine the optimal fractal dimension range.

[0019] Preferably, the method for determining the taper ratio in step 2 specifically includes:

[0020] A high-speed particle imaging system is set at the inlet of the transparent mold to capture the streamline trajectory of the phase change material;

[0021] Extract streamline deflection angle data and establish a functional relationship between deflection angle and taper ratio;

[0022] The filling cavity volume of the cavity corners under different tapers is scanned in real time by micro-focus X-ray;

[0023] Select the taper ratio that makes the maximum cavity volume smaller than the set limit and minimizes the streamline deflection angle.

[0024] Preferably, in the multi-stage pressure control in step 3, the switching points of different stages are dynamically determined by the following method:

[0025] An ultrasonic transmitter-receiver array is installed in the middle of the mold to transmit detection signals with adjustable pulse frequency;

[0026] Real-time analysis of the receiving end signal amplitude attenuation rate and phase offset. The phase offset is used to calibrate the melt flow rate, and a mapping relationship is established with the amplitude attenuation rate and the melt front position.

[0027] When it is determined based on the mapping relationship that the melt front reaches the set position of the cavity, the second stage pressure increase is triggered;

[0028] The real-time filling volume is calculated by volume integration of the ultrasonic signal. When the filling volume reaches the set threshold, the third stage of reverse suction is triggered. At the same time, the gas pressure change in the cavity is monitored by the pressure differential sensor. The gas pressure data is used to verify the integrity of the reverse suction.

[0029] Preferably, when applying the rotating magnetic field in step 4, the direction of the rotating magnetic field is optimized according to the following process:

[0030] A cylindrical sample of phase change material containing magnetic nano-additives was prepared, and micro thermocouples were embedded in the axial and radial directions of the sample.

[0031] A constant heat flux density is applied under different magnetic field direction angles, and the ratio of axial to radial thermal conductivity is calculated based on thermocouple measurement data as the first quantitative indicator of thermal conductivity anisotropy;

[0032] The surface temperature distribution of the sample is captured by an infrared thermal imager, and the second quantitative index of thermal conductivity anisotropy is calculated based on the temperature gradient distribution;

[0033] The first quantitative index and the second quantitative index are weightedly fused to calculate the comprehensive thermal conductivity anisotropy, and the magnetic field direction angle range that makes the comprehensive thermal conductivity anisotropy reach the maximum value is selected.

[0034] Preferably, the specific temperature range near the crystallization point in step 4 is calibrated as follows:

[0035] The lattice constants of phase change materials are collected in real time using synchrotron X-ray diffractometer;

[0036] The corresponding function between the lattice constant change rate and the volume shrinkage rate is calculated by first principles;

[0037] Locate the inflection point of volume shrinkage on the differential scanning calorimetry curve;

[0038] The temperature window is expanded forward and backward with the inflection point as the magnetic field application range.

[0039] Preferably, the method further includes step 5: generating an in-situ oxidation enhancement layer, which specifically includes:

[0040] The fins are placed in a closed reaction chamber with controllable oxygen partial pressure, and a mixture of inert gas and oxygen is introduced;

[0041] Heating with a segmented heating curve: in the first stage, heating to the intermediate temperature at a set rate and keeping the temperature, so as to pre-oxidize the surface of the aluminum substrate;

[0042] In the second stage, a halogen-containing activation gas is introduced, and the temperature is continued to rise to the target temperature and maintained to form a nano-needle oxide layer;

[0043] The morphology of the oxide layer was characterized by scanning electron microscopy, and a combination of process parameters was selected that made the contact angle of the phase change material smaller than a critical value.

[0044] Preferably, the component ratio of the halogen-containing activation gas is optimized according to the following process:

[0045] Samples treated with different gas compositions were prepared, and the thickness and refractive index of the oxide layer were measured using ellipsometer.

[0046] An atomic force microscope is used to scan the three-dimensional surface topography and calculate the surface energy components;

[0047] Establishing a database of physical properties of the oxide layer, the database including mapping relationships between thickness, refractive index, surface energy components and activation gas compositions;

[0048] The contact angle hysteresis curve of the molten phase change material on the modified surface was measured by the sessile drop method;

[0049] constructing a gas component-wettability correlation model based on the physical property database and the contact angle hysteresis curve;

[0050] The activated gas component ratio is selected so that the contact angle hysteresis value is lower than the set threshold and the surface energy component is within the target range.

[0051] Preferably, verification for aerospace applications includes:

[0052] The random vibration spectrum specified in the MIL-STD-810G standard is applied through a vibration table, and the frequency range covers the set wide frequency band;

[0053] An infrared thermal imager was used to monitor the temperature field uniformity of the fin-PCM interface during vibration;

[0054] After the vibration is completed, a micro-focus CT scan is performed to reconstruct the interface micro-crack distribution model;

[0055] When the total volume score of microcracks is lower than the set limit, it is judged to be qualified.

[0056] Preferably, the action time of the reverse suction pressure in step 3 is determined as follows:

[0057] A mass spectrometer is installed at the exhaust port of the mold, and the mass-to-charge ratio signal of the characteristic volatiles of the phase change material is tracked in the selected ion monitoring mode;

[0058] A correlation model between the concentration of volatiles in a phase change material in a gas and the amount of residual cavitation at the interface is established, wherein the model establishes a quantitative relationship between the concentration and the amount of residual cavitation through calibration experiments;

[0059] converting the real-time monitored volatile concentration into an estimated value of cavitation residual amount based on the correlation model;

[0060] The pumping process is terminated when the estimated value of the cavitation residual amount is lower than the safety threshold and the concentration decay rate for three consecutive sampling cycles is less than the set tolerance.

[0061] Beneficial effects of the present invention:

[0062] 1. This invention utilizes fractal interface crystallization point strengthening technology, using laser microtexturing to create fractal dendritic grooves on the fin surface. This optimizes the interface structure and increases the contact area between the fin and the phase change material. This method effectively reduces interfacial thermal resistance, strengthens the thermal contact strength between the metal fin and the PCM, significantly improves heat transfer efficiency, and reduces the impact of cyclic thermal stress on the structure. This technology effectively solves the interfacial thermal resistance problem, especially in the frequent thermal cycling environments of aerospace applications, and avoids the occurrence of thermal isolation.

[0063] 2. This invention utilizes dynamic taper filling technology and a tapered cavity in the mold design to ensure material fluidity during the filling process, avoiding issues such as cavitation and uneven filling. Furthermore, multi-stage pressure control effectively controls the injection pressure of the phase change material, eliminating microbubbles and ensuring filling quality. This design effectively mitigates stress issues caused by differential thermal expansion during thermal cycling by reducing the formation of microgaps at the interface, significantly improving structural stability and reliability.

[0064] 3. This invention optimizes the filling process and improves the thermal conductivity of the phase change material through multi-stage pressure control and magnetic field-oriented crystallization technology. Multi-stage pressure control ensures the maximum elimination of bubbles during the filling process and avoids thermal conductivity defects caused by uneven filling. Magnetic field-oriented crystallization technology aligns the magnetic nano-additives in the phase change material by applying a rotating magnetic field, enhancing the thermal conductivity of the phase change material. This improves isotropic thermal conductivity and avoids the problem of delayed thermal response.

[0065] 4. This invention utilizes in-situ oxidation enhancement layer formation technology to create a nanoscale oxide layer on the fin surface, enhancing the interfacial bonding between the metal and the phase-change material. By precisely controlling the oxidation process and optimizing the morphology of the oxide layer, the surface energy is effectively regulated, reducing the risk of interfacial delamination. This technology significantly increases the contact angle between the metal fin and the phase-change material, maintaining stable thermal performance even in high-frequency vibration environments.

[0066] 5. This invention has been rigorously validated in actual spaceflight environments using a vibration table and ultrasonic transmitter-receiver array technology, ensuring the thermal stability of the phase-change energy storage unit under frequent vibration. Ultrasonic monitoring and microfocus CT scanning have been used to verify the effects of vibration on the interface and thermal conductivity, effectively ensuring the material's long-term stable operation during spacecraft operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0068] Figure 1 is a flow chart of the steps of the method of the present invention;

[0069] Figure 2 Flowchart of the steps for determining the taper ratio in step 2 of the method of the present invention;

[0070] Figure 3 The present invention is a flowchart of the steps for verifying the aerospace application of the method of the present invention. DETAILED DESCRIPTION

[0071] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. It is also noted that, to provide a more detailed description, the following embodiments are best and preferred embodiments, and those skilled in the art may employ alternative methods for implementing certain known technologies. Furthermore, the accompanying drawings are intended only to provide a more detailed description of the embodiments and are not intended to limit the present invention.

[0072] See Figure 1-Figure 3 The embodiment of the present invention provides a composite molding method for embedded fins of a phase change energy storage unit. In step 1, a high thermal conductivity aluminum alloy (such as 6061-T6) is first selected as the fin material; a femtosecond laser is used to perform micro-texturing on the fin surface to form a dense fractal dendritic groove structure (the fractal dimension is controlled at 1.5-1.8); the groove depth is based on the thermal expansion coefficient of the PCM (such as paraffin: ~120×10 -6 The researchers used a coupled simulation to calculate the shrinkage rate (typically 2% to 4%) during the curing process. A finite element thermal stress analysis model was used to iteratively optimize the groove geometry under multiple rounds of thermal cycling simulation (-40°C to 120°C) to ensure that the groove structure maintained effective engagement and contact during thermal expansion and contraction. Finally, low-temperature plasma cleaning was used for the surface treatment to remove laser processing residues and improve wettability.

[0073] Through the above method, the fractal structure significantly increases the actual contact area of ​​the interface and reduces the thermal resistance per unit area; the microtexture can serve as a "locking site" to enhance the mechanical bite force of the PCM after curing and inhibit the interface peeling caused by thermal cycling; experiments show that this structure can reduce the interface thermal resistance by more than 35%, and the performance degradation rate is less than 10% after 200 thermal cycles.

[0074] In step 2, a tapered mold is constructed with an inlet width of 1.5 mm, an outlet width of 0.5 mm, and a length controlled between 20 and 30 mm. Based on the molten rheological curve of a phase change material (such as paraffin wax) (between 0.02 and 0.05 Pa·s), a non-Newtonian fluid dynamics model (such as the Herschel-Bulkley model) is introduced. CFD simulations are performed using software such as COMSOL to determine the optimal taper ratio (approximately 3:1) to control the shear rate and improve the material's ability to fill narrow gaps. The mold is preheated to 5–10°C above the PCM melting point to reduce viscosity. Bottom-feeding and top-exhaust ventilation are used to ensure no residual gas.

[0075] Through the above method, the dynamic taper design effectively guides the material to be evenly distributed in the tiny fin gap, significantly reducing the cavitation rate; improving the uniformity of filling pressure and avoiding local overfilling or cavities; the measured filling completeness in the fin gap is increased to more than 97%, and the cavitation rate is reduced to less than 2%, ensuring the continuity of the heat conduction path.

[0076] In step 3, the first stage is to maintain the injection pressure at 3 to 5 times the PCM saturated vapor pressure during the initial filling phase to prevent evaporation and bubble formation. The second stage is to monitor the filling front using infrared thermal imaging. When the front reaches a set position in the middle of the mold cavity (e.g., 70% volume), the pressure is instantly increased by 20 to 30% to ensure that there are no bubble tails at the front. The third stage is to immediately apply negative pressure (approximately -30 to -50 kPa) after the filling volume reaches the 95% threshold to expel residual gas from the outlet and enhance contact between the PCM and the fin surface.

[0077] Through this method, the pressure distribution of the molten PCM is effectively controlled to avoid bubble entrainment; dynamic pressure regulation is combined with thermodynamic state switching to improve filling density; comparative experiments show that compared with conventional static pressure injection, the three-stage control strategy reduces the number of microbubbles by 60% and increases the overall thermal conductivity by more than 20%.

[0078] In step 4, magnetic nanoparticles (such as Fe3O4, Ni, etc.) are added to the PCM at a mass fraction of 1-3%. During the PCM cooling stage, a rotating magnetic field of 0.3-0.6 T (frequency 1-5 Hz) is applied using a programmable electromagnetic coil. The magnetic field is controlled to open in the material's supercooling temperature window (2-5°C below the PCM melting point). The field strength stability is monitored using a real-time Hall sensor array to ensure that the nanoparticles are oriented in the crystalline region to form thermal chains. After solidification, CT scanning is used to verify the continuity of the thermal chain distribution.

[0079] Through the above method, a deep heat conduction path is effectively constructed, and the isotropic thermal conductivity inside the phase change unit is improved; the thermal hysteresis problem is reduced, especially the heat transfer capacity is significantly enhanced in the area far away from the fins; thermal response tests show that the temperature response time in the hot spot area is shortened by more than 30%, and the overheating temperature rise is reduced by 10~15℃, thereby enhancing the thermal management capability of the equipment.

[0080] Through integrated process design, focusing on four dimensions—interface structure, material flow, filling control, and microscopic thermal chain construction—this system systematically addresses the issues inherent in traditional PCM embedded fin structures, such as high thermal resistance, thermal cycling failure, filling defects, and interrupted thermal paths. Overall thermal performance has been significantly improved. In typical aerospace thermal cycling simulations, the thermal decay rate of the energy storage unit was kept below 5%, far exceeding existing technologies and demonstrating high engineering application value.

[0081] In one possible implementation, a fractal, branch-like groove structure is first generated on the fin surface using femtosecond laser processing. The groove surface topography is then scanned at high resolution using a scanning electron microscope (SEM) to obtain detailed images of the microstructure. These images clearly demonstrate the branching structure of the laser-processed grooves on the fin surface, particularly the self-similarity of the branches.

[0082] Extract the self-similarity characteristics of branching structures from scanning electron microscopy images. Analyze the images using image processing software (such as ImageJ or Matlab) to identify the key geometric features of the branches (such as branch angles and length distribution). Then, calculate the self-similarity index to obtain the fractal dimension. This calculation method uses the box counting method or fractal dimension regression analysis to estimate the fractal dimension based on the changes in the number of branches at different scales.

[0083] Based on experimental data and numerical simulations, a correlation model between fractal dimension and interface bonding strength was established. Specifically, the groove surface generated by laser processing exhibits fractal structures, which have self-similarity characteristics. To establish the correlation model, it is first necessary to use a scanning electron microscope (SEM) to scan the microstructure of these grooves with high precision and obtain an image. The self-similarity characteristics of the fractal dendritic structure are extracted through image processing methods (edge ​​detection). Self-similarity is a basic property of fractal structures, represented by the fractal dimension, which is used to describe the degree of similarity of structures at different scales.

[0084] The relationship between fractal dimension and interfacial bonding strength can be quantified by establishing a finite element simulation model. The basic idea behind this model is that an increase in fractal dimension indicates greater surface complexity and a larger contact area between the fin and the phase change material. This generally increases interfacial bonding strength because a larger contact area implies more molecular or atomic-level interactions.

[0085] However, too high a fractal dimension may lead to an overly complex structure, increase stress concentration, affect the stability of the interface area, and even lead to the formation of fragile areas between materials, thereby reducing the bonding strength.

[0086] During finite element simulations, the model inputs external vibration loads, such as spacecraft vibration spectrum loads, to simulate the material's response under dynamic loads. This allows the impact of different fractal dimensions on interface strength to be evaluated, and the stress distribution, deformation, and changes in bond strength at the interface to be calculated.

[0087] Finite element simulation provides theoretical data support for the model, but the ultimate verification is conducted through shaker table testing. During these tests, samples with varying fractal dimensions are designed and manufactured to simulate the actual vibration loads experienced in a spacecraft environment. The debonding area at the sample interface is then measured. The size of the debonding area is a key indicator of interfacial bond strength. Generally speaking, the smaller the interfacial debonding area, the higher the bond strength.

[0088] After the shaking table test, the specimens were imaged at high resolution using micro-CT scanning technology to scan and evaluate the bond strength distribution of the undebonded areas of the interface. Micro-CT provides detailed structural images of the interface, including the bond strength between the fins and the phase change material. The scanning results identify a critical threshold—the tipping point between the debonded area and the material bond strength. Beyond this threshold, the debonded area increases significantly, resulting in a decrease in bond strength. Ultimately, by analyzing the variation in debonded area at different fractal dimensions, the optimal fractal dimension range can be determined.

[0089] The results obtained from the above experimental data (including finite element simulation, vibration table test, micro-CT scanning, etc.) ultimately enabled the establishment of a complete mathematical model of fractal dimension and interface bonding strength. The core of this model is:

[0090] There is a nonlinear relationship between fractal dimension and interface bonding strength; by optimizing the fractal dimension, a balance point can be found that provides sufficient bonding strength without introducing excessive stress concentration problems.

[0091] By inputting different fractal dimensions and combining them with vibration spectrum loads and other external conditions, the most suitable fractal dimension range can be finally selected. The materials within this range have the lowest interface debonding area and the best bonding strength.

[0092] A mathematical model linking fractal dimension and interfacial bonding strength was established by leveraging the self-similarity characteristics captured by scanning electron microscope images, verifying this through finite element simulation and vibration table testing, and ultimately determining the critical threshold through micro-CT scanning. This model effectively helps optimize the fractal structure of the fin surface, ensuring the reliability and performance of the phase change energy storage unit, particularly its stability in vibration environments. This optimization method ensures optimal bonding strength between the fin and the phase change material, thereby improving the service life and performance stability of the entire energy storage unit.

[0093] Dynamic loading tests were conducted on fin samples with different fractal dimensions using a vibration table. The tests simulated the vibration loads experienced in a spacecraft operating environment. The vibration table tests employed an acceleration spectrum to simulate typical spacecraft vibration conditions. During the experiments, the area of ​​interfacial delamination was measured under accelerated vibration. By monitoring the changes in the delamination area, the effect of different fractal dimensions on interfacial strength was evaluated.

[0094] After the vibration table test, the specimens were analyzed internally using micro-CT scanning to determine the bond strength distribution in the unpeeled areas. CT scanning allows for detailed observation of the bond between the fin and the phase change material, analyzing the interface structure and strength distribution in the unpeeled areas. Combined with the vibration test results, a critical threshold was determined, above which the interfacial bond strength significantly decreases, leading to debonding.

[0095] Based on vibration table tests and micro-CT scan results, a fractal dimension range was selected that kept the interfacial debonding area below a critical threshold. This optimization process achieved a balance between fractal dimension and interfacial bonding strength, ensuring a strong bond between the fin and the phase change material without compromising the material's thermal conductivity.

[0096] In one possible implementation, a high-speed particle imaging system is installed at the mold inlet to capture the streamlines of the flowing phase-change material in real time. This imaging system uses high-speed video and laser illumination to generate images of the particle paths during fluid flow, accurately reflecting the path and velocity of the phase-change material within the mold.

[0097] In an embodiment of the present invention, a high-speed camera captures the phase change material flowing in a transparent mold, and a laser is used as a light source to generate scattered light during the particle flow process, helping the imaging system capture streamline trajectories.

[0098] The captured images are analyzed for streamlines using image processing software to extract particle movement trajectories, and the deflection angle data of the fluid at different tapers is obtained using a flow analysis algorithm.

[0099] Real-time tracking of the flow path can accurately grasp the velocity distribution and streamline direction of the flow, providing basic data for further optimization of the taper ratio.

[0100] Capturing the streamline deflection angle reveals the flow pattern of the material in the mold, which helps to reduce uneven flow and cooling and prevent local defects in the cavity.

[0101] Furthermore, by statistically analyzing streamline deflection angle data obtained by a high-speed particle imaging system, a functional relationship between the deflection angle and the mold taper ratio was established. Specifically, changes in taper directly affect the deflection angle during material flow, which in turn affects the filling effect.

[0102] In this embodiment, particle imaging results at various taper ratios were used to calculate streamline deflection angles. In combination with fluid dynamics principles, a mathematical model was established to determine the functional relationship between deflection angle and taper ratio. Computational fluid dynamics (CFD) software was used for simulation verification, and numerical simulations were compared with experimental data to further optimize the relationship between deflection angle and taper ratio.

[0103] By accurately calculating the relationship between deflection angle and taper, the mold taper ratio can be rationally designed, optimizing the material flow path to ensure flow uniformity and filling integrity. This improves the controllability of the production process and reduces material waste and defects caused by improper design.

[0104] Microfocus X-ray scanning technology can accurately detect the filling effect of composite materials in mold corners and complex areas. By scanning the cavity corners at different tapers in real time, it can accurately measure the filling volume and provide data support for subsequent optimization.

[0105] In this embodiment of the present invention, a microfocus X-ray machine is deployed to obtain void volume data in corner areas by scanning the filling effect under different taper conditions in real time within the mold. The void volume is calculated based on the scan data and compared with the set limit to determine the taper ratio that effectively reduces voids and ensures mold filling integrity.

[0106] This method can accurately evaluate filling performance at different taper angles, preventing large voids or defects within the cavity caused by uneven flow. It also provides a non-destructive testing method for real-time monitoring of production process issues and ensuring product quality.

[0107] On the basis of the above steps, by comprehensively considering factors such as the maximum cavity volume and the streamline deflection angle, the taper ratio that makes the maximum cavity volume smaller than the set limit and the streamline deflection angle the smallest is selected.

[0108] In the present embodiment, the optimal taper ratio is selected by comparing the filled cavity volume and streamline deflection angle data at various taper ratios, combined with experimental verification results. If certain taper ratios result in excessive deflection angles or excessive cavity volume, the mold design needs to be adjusted and iterative optimization needs to be performed.

[0109] By minimizing the void volume and deflection angle, the filling quality of the composite material can be greatly improved, reducing the need for later repairs or rework. This helps improve production efficiency, reduce the scrap rate caused by material defects, and lower production costs.

[0110] By combining advanced technologies such as high-speed particle imaging, deflection angle modeling, and microfocus X-ray scanning, the mold taper design was optimized to ensure good flow and filling of the composite material during the molding process. This not only improves molding quality but also significantly reduces material waste and production costs, making it a key step in improving the performance of the embedded fin composite molding method for phase change energy storage units.

[0111] In one possible implementation, an ultrasonic transmitter-receiver array is installed in the middle of the mold to monitor the flow of the phase change material in real time. By transmitting pulse signals and receiving echo signals, the ultrasonic transmitter-receiver array can obtain information about the dynamic changes of the material in the mold.

[0112] An array of multiple ultrasonic sensors is installed in the middle of the mold. These sensors transmit pulse signals with adjustable frequencies, penetrating the material and generating feedback signals. The frequency of the ultrasonic pulses is adjusted to suit the mold and material, ensuring the signal effectively penetrates and reflects back to the receiving array, providing accurate reflection data.

[0113] Ultrasonic technology monitors the flow dynamics of phase change materials, enabling real-time determination of the material's frontier position, providing accurate timing and data support for subsequent pressure control. This technology enables contactless, real-time monitoring of the melt's flow state, minimizing disruption to the production process and improving production efficiency.

[0114] The amplitude decay rate and phase offset of the receiving signal are key parameters for evaluating the position of the melt front. By analyzing these parameters in real time, it is possible to accurately determine the melt progress and the pressure change requirements during the molding process.

[0115] By analyzing the amplitude decay rate and phase offset of the received ultrasonic signal, parameters representing the position of the melt front are extracted. These parameters are closely related to the flow of the material in the mold and can accurately indicate the flow state of the melt. Through experimental data and numerical simulation, a mathematical mapping relationship between the amplitude decay rate and phase offset and the position of the melt front is established, making it possible to accurately determine the position of the material by analyzing the signal changes.

[0116] Accurately determining the position of the melt front provides a dynamic basis for subsequent pressure adjustments, preventing defects caused by incomplete mold filling. Real-time analysis of signal changes enables timely pressure adjustments to prevent excessive or slow material flow during molding, thereby optimizing the filling process.

[0117] During multi-stage pressure control, when the signal amplitude decay rate reaches the set first characteristic value, the system automatically triggers the second stage of pressure increase. At this point, the material flow has reached a certain depth or front position, and the pressure needs to be increased to ensure that the material can completely fill the mold.

[0118] The first characteristic value of the amplitude decay rate is set based on experimental data. When the amplitude reaches this value, indicating that the material has flowed to a critical point, the system will automatically increase the pressure. Using an electric or hydraulic control system, the pressure in the mold is rapidly increased, allowing the melt to continue to advance and fill the incomplete area.

[0119] The melt progress is determined by the amplitude decay rate, accurately triggering the pressure increase to avoid unnecessary pressure fluctuations and ensure that the material is fully filled at the correct time. The automatic control process reduces human intervention and improves the stability and consistency of the molding process.

[0120] During the molding process, the system monitors changes in the gas pressure within the cavity to determine when to enter the reverse suction phase. When the gas pressure drops to a second set characteristic value, the system automatically triggers the reverse suction phase. This phase further optimizes the removal of gas from the mold, ensuring that the material completely fills the mold and reducing internal bubbles and defects.

[0121] A differential pressure sensor is installed to monitor changes in gas pressure within the mold cavity in real time. When the gas pressure drops to a preset second characteristic value, the system automatically detects this change. Based on the pressure sensor's feedback, the control system activates a reverse suction mechanism to extract excess gas or bubbles, ensuring that the material completely fills the mold.

[0122] Precisely control the gas pressure changes within the cavity to avoid defects caused by gas failure and improve molding quality. Reverse suction technology ensures that there are no bubbles in the mold, reducing product defects and improving the mechanical and thermal properties of the product.

[0123] By combining an ultrasonic transmitter-receiver array, amplitude attenuation and phase offset analysis, gas pressure monitoring, and dynamic pressure control, precise multi-stage pressure control can be achieved. This method effectively improves material flowability and filling integrity during the composite molding process of embedded fins in phase change energy storage units. Real-time monitoring and dynamic adjustments ensure an efficient and stable molding process. Ultimately, this helps improve product quality and production efficiency, reducing defects and waste.

[0124] In one possible implementation, a phase-change material sample is first prepared, containing magnetic nanoparticle additives. These additives enhance the material's thermal conductivity and response to external magnetic fields. Microthermocouples are embedded in the sample at axial and radial locations to monitor temperature changes in the material in real time. This temperature data is used for subsequent thermal conductivity calculations and thermal imaging analysis.

[0125] Select a suitable phase-change material and add magnetic nanomaterials during its preparation. Common additives include ferromagnetic nanoparticles (such as Fe3O4 and NiFe2O4). These additives can enhance the phase-change material's responsiveness to magnetic fields. Microthermocouples are embedded in the sample at different axial and radial locations to collect temperature data in real time in different directions, ensuring a comprehensive analysis of the material's thermal conductivity in different directions.

[0126] Ensure that the sample temperature changes can be monitored in real time when a magnetic field is applied, obtaining accurate thermal conductivity data. Magnetic nano-additives enhance the thermal conductivity of the material, helping to optimize the transfer and storage of thermal energy.

[0127] By applying a constant heat flux and varying the magnetic field angle, the thermal conductivity characteristics of the phase change material under different magnetic field directions can be analyzed. By measuring the ratio of the axial to radial thermal conductivity coefficients in different directions, the effect of the magnetic field direction on thermal conductivity can be evaluated.

[0128] A constant heat flux is applied to the sample surface, and the stability of the heat flux is maintained by controlling the heating power. The thermal conductivity of the sample in the axial and radial directions is measured at different magnetic field angles, and their ratio is calculated to evaluate the difference in thermal conductivity in different directions.

[0129] By measuring the ratio of thermal conductivity coefficients at different directions and angles, we can clearly understand whether the material's thermal conductivity is anisotropic and the impact of different magnetic field directions on the material's thermal conductivity. This provides a basis for optimizing the direction of the rotating magnetic field to ensure the greatest improvement in the material's thermal conductivity efficiency.

[0130] The temperature field distribution on the sample surface is captured by an infrared thermal imager, and the temperature changes in different directions are further analyzed. By calculating the thermal conductivity anisotropy, the difference in thermal conductivity of the material under different magnetic field directions can be obtained.

[0131] An infrared thermal imager is used to capture real-time images of the sample surface, capturing temperature field distribution images. Analysis of the temperature distribution in these images reveals the heat flow path and anisotropic distribution within the material. By comparing the temperature field distribution in different directions, the material's thermal conductivity anisotropy—the difference in thermal conductivity in different directions—is calculated. A larger value indicates a more uneven thermal conductivity, potentially affecting its energy storage performance.

[0132] Infrared thermal imaging technology can observe surface temperature changes in real time and accurately quantify the material's thermal conductivity anisotropy through data analysis, providing an intuitive basis for subsequent optimization of the magnetic field direction. This method can reveal the thermal conductivity characteristics of materials and help improve material design, enabling more efficient thermal management in various applications.

[0133] The data from the aforementioned experiments allows us to select the magnetic field angle that maximizes the thermal conductivity anisotropy. Optimizing the direction of the rotating magnetic field can effectively improve the material's thermal conductivity, thereby enhancing its thermal response.

[0134] Based on experimental data on the ratio of thermal conductivity to thermal anisotropy at different magnetic field angles, the magnetic field angle that maximizes thermal anisotropy is selected. During the final molding process, a rotating magnetic field is applied at the optimized magnetic field angle, adjusting the magnetic field direction to improve the thermal conductivity of the phase change material.

[0135] By precisely selecting the optimal magnetic field orientation angle, the thermal conductivity of the material can be maximized, thereby improving the thermal management capabilities of the phase-change energy storage unit. This improves the thermal efficiency of the material in practical applications, reduces heat energy waste, and enhances the heat storage and release capabilities of the phase-change energy storage unit.

[0136] Through this optimization process, the direction of the applied rotating magnetic field can be precisely controlled to optimize the material's thermal conductivity in terms of anisotropy. By conducting multi-angle, all-round tests on phase-change materials containing magnetic nano-additives, combined with infrared thermal imaging and thermal conductivity ratio analysis, the material's thermal management capabilities can be significantly improved, reducing heat energy waste and laying the foundation for efficient operation of phase-change energy storage units. Ultimately, the optimized magnetic field direction can significantly improve the material's thermal conductivity and enhance its thermal response speed and stability, providing technical support for efficient thermal energy storage and release.

[0137] In one possible implementation, a synchrotron X-ray diffractometer is first used to measure the lattice constant changes of the phase-change material at different temperatures in real time. Synchrotron X-ray diffraction provides highly accurate lattice constant data. By monitoring the lattice constant changes of the phase-change material during heating or cooling in real time, the phase transition temperature range of the material can be clearly identified.

[0138] A phase-change material sample is placed in an X-ray diffractometer and scanned at different temperatures, recording in real time the changes in the lattice constant of the material during heating or cooling. Synchrotron radiation provides high-brightness X-rays, allowing precise capture of even tiny changes in lattice constants.

[0139] The data recorded at different temperatures will be used to analyze the changes in the material's lattice structure during phase transitions, especially the characteristics of the changes near the crystallization point.

[0140] Accurately measuring the lattice constant can help clarify the starting and ending points of the material's phase transition. It also provides accurate temperature information, providing experimental data support for subsequent calibration of the applied magnetic field temperature range.

[0141] Next, first-principles calculations were used to derive the mathematical relationship between the rate of change of the lattice constant and the volume shrinkage rate. This calculation provides a theoretical basis for optimizing the magnetic field application range.

[0142] Specifically, quantum mechanics simulations were used to calculate the rate of change of the lattice constant of the phase-change material at different temperatures and to derive a mathematical functional relationship between this rate and the volume shrinkage. Through simulation and fitting, the functional relationship between the lattice constant change rate and the volume shrinkage rate was obtained, revealing the structural changes characteristic of the material during the phase transition.

[0143] Theoretical calculations can accurately predict the physical behavior of materials at different temperatures, helping to design experimental conditions. This step provides a theoretical basis for locating the material's phase transition temperature and volume change, allowing for more precise setting of the temperature range for applying the magnetic field.

[0144] Differential scanning calorimetry is used to analyze the thermal response curve of the phase change material and locate the inflection point of the volume shrinkage change on the curve. This inflection point usually corresponds to the crystallization point temperature or critical phase transition temperature of the phase change material. Accurately determining this inflection point helps to better define the magnetic field application range.

[0145] By heating or cooling a phase change material using a differential scanning calorimeter (DSC), the changes in heat flow are recorded to produce a DSC curve. By analyzing the inflection point of the volume shrinkage change in the curve, the phase change temperature range of the material can be determined.

[0146] Identify and accurately locate the inflection point on the DSC curve where the volume shrinkage changes significantly, that is, the phase transition temperature of the material.

[0147] DSC testing can visually demonstrate the thermal response of a material at different temperatures, facilitating accurate determination of phase transition points. Determining the inflection point of volume shrinkage helps to more precisely define the temperature range for applying the magnetic field, thereby improving the performance of phase change materials.

[0148] Finally, based on the inflection point of the volume shrinkage change located on the DSC curve, a certain temperature range is expanded forward and backward with the inflection point as the center to set the temperature window for applying the magnetic field.

[0149] A temperature range is established around the inflection point to ensure that the magnetic field application interval covers the material's phase transition process. Applying a rotating magnetic field within this temperature window can effectively enhance the material's phase transition response. Applying a rotating magnetic field within this temperature window optimizes the material's phase transition properties, improving its heat storage capacity and thermal response speed.

[0150] Precisely setting the temperature window helps optimize the application of the magnetic field, ensuring optimal thermal management of the material during the phase change process. By applying a rotating magnetic field within the phase change temperature range, the material's thermal conductivity, heat storage and release properties can be further improved, thereby increasing the efficiency of the phase change energy storage unit.

[0151] By precisely calibrating the temperature range near the crystallization point of the phase change material, the temperature window for applying the magnetic field can be effectively optimized, thereby improving the thermal conductivity and phase change efficiency of the material. The combination of various technical means, such as synchrotron X-ray diffraction, first-principles calculations, and differential scanning calorimetry, provides a scientific basis for setting the magnetic field application range, enabling precise control of temperature changes during the phase change process, thereby improving the overall performance of the phase change energy storage unit. This method not only improves the thermal conductivity of the phase change material, but also enhances its stability and efficiency during the energy storage process.

[0152] In one possible implementation, the fins are first placed in a sealed reaction chamber with a controllable oxygen partial pressure. The chamber's design allows for precise control of the oxygen partial pressure, ensuring a controllable oxidation process. A gas mixture consisting of an inert gas (such as nitrogen or argon) and oxygen is introduced into the chamber. The inert gas prevents unwanted reactions between other gases and the fin surface, while oxygen is a core component required for the oxidation process, promoting the formation of the aluminum oxide layer.

[0153] According to the oxidation requirements, the ratio of oxygen and inert gas is reasonably adjusted to keep the oxygen partial pressure within the most suitable range for oxidation to avoid excessive oxidation or incomplete oxidation.

[0154] Precisely controlling the oxygen concentration helps stabilize the oxidation process and avoid uneven or excessive oxidation on the fin surface.

[0155] The presence of inert gas can prevent unnecessary side reactions and ensure the quality of the oxide layer.

[0156] Furthermore, a staged heating curve is used for control. In the first stage, the aluminum substrate of the fin is heated at a set rate until it reaches an intermediate temperature and then remains at that temperature. This stage primarily pre-oxidizes the aluminum substrate, forming a thin oxide layer. The purpose of pre-oxidation is to provide a foundation for subsequent deep oxidation and to prevent the formation of an irregular oxide layer during the subsequent heating process.

[0157] An appropriate heating rate is set so that the aluminum substrate surface can gradually reach the predetermined temperature to ensure uniformity of the oxidation process. Insulation is performed at an intermediate temperature to ensure that the oxidation reaction occurs at an appropriate temperature, providing a good starting point for the subsequent oxide layer.

[0158] The formation of a pre-oxidation layer helps the subsequent oxide layer grow uniformly, avoiding stress damage caused by temperature changes. Reasonable heating rate and holding time can control the thickness and quality of the oxide layer.

[0159] In the second stage, halogen-containing activation gases (such as hydrogen chloride and hydrogen fluoride) are introduced. These gases activate the oxidation process, significantly increasing the oxidation rate. The halogen gas accelerates the oxidation reaction, forming an oxide layer with a nano-needle structure. This oxide layer has a large specific surface area, effectively enhancing the adhesion between the fins and the phase change material, thereby improving heat transfer efficiency and energy storage.

[0160] By controlling the gas flow and concentration, the activation effect of the halogen gas is precisely controlled to promote the rapid formation of the aluminum oxide layer. Continuing to heat to the target temperature and maintaining the temperature ensures the formation and stability of the oxide layer.

[0161] The activation effect of halogen gas can significantly increase the oxidation rate, reduce the oxidation time, and improve production efficiency. The nano-needle structure of the oxide layer can significantly increase the surface area, enhance the contact force and thermal conductivity between the fin and the phase change material.

[0162] The final morphology of the oxide layer is characterized using scanning electron microscopy (SEM) to ensure the oxide layer possesses a nanoneedle-like structure and to assess its contact properties with the phase-change material. Based on the SEM results, the optimal process parameter combination is selected to achieve a contact angle between the phase-change material and the oxide layer below a critical value. A smaller contact angle indicates good contact between the phase-change material and the oxide layer, improving the material's thermal conductivity and energy storage performance.

[0163] The oxide layer was analyzed to determine the distribution and uniformity of the nanoneedle-like structures. Based on the SEM results, process parameters were adjusted to ensure the contact angle met the requirements, thereby improving the adhesion of the phase change material.

[0164] Electron microscopy characterization allows for effective monitoring of the oxide layer morphology, and allows for optimization of material performance through process parameter adjustments. The optimized contact angle ensures better contact between the phase change material and the fin surface, enhancing overall thermal management.

[0165] By generating an oxide layer with a nano-needle structure on the surface of the aluminum substrate fin, the bonding strength and thermal conductivity of the fin to the phase change material are significantly improved. By combining staged heating, halogen gas activation, and scanning electron microscopy characterization, the quality and structure of the oxide layer are optimized, thereby improving the thermal conductivity and energy storage capacity of the phase change energy storage unit. This technology enables precise control of the material's surface properties and enhances the performance of the energy storage unit by optimizing process parameters.

[0166] In one possible implementation, samples are first prepared using different halogen-containing activation gas compositions. These samples are treated with varying gas composition ratios to achieve different oxide layer properties. The halogen-containing gas ratio influences the degree of activation of the oxidation reaction and oxide layer formation, thus directly impacting the final surface properties.

[0167] By adjusting the ratio of halogen gases such as chlorine and fluorine to oxygen, multiple samples were prepared to ensure controllable and consistent oxidation. In a sealed reaction chamber, samples were oxidized under different gas compositions and processing conditions to ensure that the oxide layer can form in a variety of gas environments.

[0168] By combining various gas components, different oxide layer characteristics can be obtained, and the optimal oxidation conditions can be found.

[0169] Next, ellipsometers were used to characterize the samples treated with different gas compositions, measuring the thickness and refractive index of the oxide layer. These parameters are crucial for evaluating the quality of the oxide layer, as changes in the refractive index can reflect the density and optical properties of the oxide layer.

[0170] Ellipsometers were used to precisely measure the thickness of the oxide layer on the sample surface, and optical reflectometry was used to determine its refractive index. The quality of the oxide layer was assessed by comparing changes in thickness and refractive index based on the treatment conditions of different gas components.

[0171] Ellipsometers provide highly accurate data on oxide layer thickness and refractive index, helping to determine the uniformity and quality of the oxide layer. This optical property data can be used to adjust the oxidation process to achieve optimal oxidation results.

[0172] By using an atomic force microscope (AFM), the three-dimensional morphology of the oxide layer surface is scanned and the surface energy components are calculated. The surface energy directly affects the interaction between the phase change material and the fin oxide layer, which in turn affects the thermal conductivity and stability of the phase change energy storage unit.

[0173] Atomic force microscopy is used to capture the surface morphology of the oxide layer and analyze its roughness and nanostructure. The surface energy components of the oxide layer are calculated from AFM data to assess the adhesion and wetting properties of the surface.

[0174] By accurately analyzing surface energy and morphology, we can better understand the interface characteristics between the phase change material and the oxide layer, providing a theoretical basis for optimizing process parameters. Increasing the surface energy component can enhance the adhesion between the phase change material and the fin surface, improving the overall performance of the energy storage unit.

[0175] Next, the sessile drop method was used to measure the contact angle hysteresis curve of the molten phase change material on the modified surface. The contact angle hysteresis curve reflects the wettability and adhesion between the phase change material and the oxide layer. A smaller contact angle hysteresis value indicates that the phase change material is able to spread better on the surface, reducing thermal resistance and improving heat transfer efficiency.

[0176] Drop a molten phase change material onto the oxide layer, observe its spreading behavior, and record the contact angle curve. The hysteresis curve morphology allows analysis of the degree of contact angle hysteresis and the wettability of the surface.

[0177] The sessile drop method effectively evaluates the interaction between the modified surface and the phase change material and optimizes the surface treatment process. Selecting the activation gas component ratio that results in a contact angle hysteresis value below a set threshold ensures that the phase change material has good spreadability on the surface, reducing thermal resistance and improving thermal management performance.

[0178] Based on the data analysis from the previous step, the activation gas composition ratio is selected to achieve a contact angle hysteresis value below the set threshold. The goal of this step is to optimize the oxidation process and achieve the best surface properties of the oxide layer, thereby improving the contact performance between the phase change material and the oxide layer and promoting efficient heat transfer.

[0179] Based on the contact angle hysteresis curve and surface energy analysis results, the optimal gas component ratio is screened. The type and concentration of the halogen gas are adjusted so that the final contact angle hysteresis value meets the set threshold.

[0180] By precisely controlling the activation gas composition ratio, we optimize surface properties, ensuring maximum contact between the phase change material and the oxide layer, and improving the thermal conductivity and energy storage capacity of the energy storage unit. The resulting optimized gas composition ratio helps improve process stability and repeatability, ensuring consistency throughout production.

[0181] Through this optimization process, advanced techniques such as ellipsometry, atomic force microscopy, and the sessile drop method are utilized to comprehensively evaluate the effects of different gas components on the oxide layer, enabling the accurate selection of the optimal activation gas ratio. Ultimately, this optimization step helps improve the quality of the oxide layer and enhance the bonding strength between the phase change material and the surface, thereby enhancing the performance of the phase change energy storage unit and achieving more efficient energy storage and thermal management.

[0182] In one possible implementation, random vibration spectrum testing is performed according to the MIL-STD-810G standard, which is primarily used to verify the reliability of equipment in random vibration environments. The vibration table test frequency range needs to cover a predetermined wide frequency band to simulate the various vibration conditions experienced during launch, flight, and operation of a spacecraft. This test comprehensively evaluates the dynamic response of the fin-PCM composite material under vibration and provides data support for subsequent thermal performance and structural stability analysis.

[0183] During vibration testing, an infrared thermal imager was used to monitor the temperature distribution at the fin-PCM interface in real time. By monitoring the material's temperature changes during vibration, the thermal conductivity and interfacial stability of the phase change material under vibration loads can be determined. Temperature uniformity is a key indicator for verifying the material's thermal conductivity efficiency and stability, effectively indicating any potential thermal failure risks, especially under high dynamic loads.

[0184] After the vibration test, the samples were examined using microfocus CT scanning to reconstruct a model of the interfacial microcrack distribution. This step accurately detects cracks or delamination at the fin-PCM interface, thereby assessing the structural integrity of the interface. This step is crucial because the presence of microcracks can affect thermal conductivity and the long-term reliability of the material.

[0185] Based on the microfocus CT scan results, the total volume fraction of interface microcracks is calculated. If the total number of microcracks is below a preset limit, the phase change energy storage unit is considered qualified. Conversely, if the number of cracks exceeds the set threshold, it indicates that the material structure may have defects and does not meet application requirements. This judgment standard ensures high reliability and long life in aerospace applications.

[0186] Through this verification process, the present invention can effectively detect and evaluate the performance of phase-change energy storage units in extreme environments such as vibration, temperature, and long-term loads. The combination of vibration table testing, infrared thermal imaging monitoring, and microfocus CT scanning ensures the structural stability and thermal conductivity of the phase-change energy storage unit under highly dynamic and harsh environmental conditions. This series of rigorous verification methods can ensure the reliability of phase-change energy storage units in demanding applications such as aerospace, providing a solid foundation for practical application. By controlling the generation and development of microcracks, the material's service life can be extended, and the system's thermal management efficiency and operational stability can be improved.

[0187] In one possible implementation, a mass spectrometer is installed at the mold's exhaust port to monitor the concentration changes of the exhaust gas in real time. The mass spectrometer can accurately analyze the various volatile components in the gas, particularly organic compounds that may volatilize from phase-change materials under high temperature or high pressure. This real-time monitoring ensures that changes in gas composition are constantly monitored during the extraction process, preventing excessively long or short extraction times and thus avoiding unnecessary energy waste or material loss.

[0188] Based on experimental data, a correlation model was established between volatile concentration and the amount of residual interfacial cavitation. During the molding process of phase change materials, cavitation may form, which can affect the interfacial bonding strength and thermal conductivity between the fin and the phase change material. By analyzing changes in the volatile concentration of the gas, the residual cavitation during the molding process can be indirectly determined. When the volatile concentration in the gas reaches a certain level, interfacial cavitation is essentially eliminated, resulting in a more compact molded part and optimized thermal conductivity.

[0189] When the mass spectrometer detects that the concentration of volatiles in the exhaust gas has dropped to the background noise level, it can be assumed that cavitation has been essentially eliminated and the volatiles in the material have been completely removed. At this point, the reverse suction process should be terminated promptly. This control strategy ensures that the suction process is terminated neither too early, resulting in incomplete removal of cavitation, nor too late, avoiding the adverse effects of excessive suction on the mold and material.

[0190] By real-time monitoring of the volatile components of the exhaust gas, the risks of cavitation and residual volatiles are avoided, ensuring a good interface between the fin and the phase change material, thereby improving the thermal conductivity and stability of the phase change energy storage unit. Furthermore, by establishing a correlation model between the concentration of gas volatiles and the amount of residual cavitation, the timing and conditions of the extraction process can be precisely controlled, making the entire molding process more accurate and efficient. This method effectively avoids over- or under-extraction, reduces defects in the molding process, and improves product quality and reliability.

[0191] The present invention encompasses any alternatives, modifications, equivalents, and solutions that fall within the spirit and scope of the present invention. To provide a thorough understanding of the present invention, specific details are described in detail below in connection with the preferred embodiments of the present invention, but those skilled in the art will be able to fully understand the present invention without these detailed descriptions. Furthermore, to avoid unnecessary confusion regarding the essence of the present invention, well-known methods, processes, procedures, components, and circuits have not been described in detail.

[0192] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A composite molding method for embedded fins of a phase change energy storage unit, characterized in that: include: Step 1: Fractal interface crystallization point strengthening: laser microtexturing is used to generate fractal dendritic grooves on the fin surface. The groove depth is determined by iterative calculation of the interface thermal stress simulation model based on the thermal expansion coefficient and curing shrinkage rate data of the phase change material. Step 2: Dynamic taper filling: Construct a tapered mold cavity with an inlet cross-sectional area larger than the outlet cross-sectional area. The taper ratio is determined by the melt viscosity curve of the phase change material and the non-Newtonian fluid dynamics model. Step 3: Multi-stage pressure control, which controls the injection pressure of the molten phase change material in three stages: in the first stage, the pressure is maintained higher than the set multiple of the saturated vapor pressure; in the second stage, the pressure is increased to the threshold for eliminating microbubbles when the filling front reaches the set position in the cavity; The third stage applies reverse suction pressure when the fill volume reaches a set threshold; Step 4: Magnetic field oriented crystallization: a rotating magnetic field is applied near the crystallization point of the phase change material. The magnetic field strength is determined based on the magnetization intensity-temperature curve of the magnetic nano-additives, so that the additives are oriented to form thermal conductive chains.

2. A composite molding method for embedded fins of a phase change energy storage unit according to claim 1, characterized in that: When generating the fractal branched grooves in step 1, the fractal dimension is optimized in the following manner: collecting a scanning electron microscope image of the laser-processed groove, extracting self-similarity features of the branch structure, and calculating the fractal dimension based on the self-similarity features; A correlation model between fractal dimension and interface bonding strength was established. By inputting the spacecraft vibration spectrum load into the finite element simulation model, the interface bonding strength under different fractal dimensions was predicted. The interface debonding area of ​​samples with different fractal dimensions under a set acceleration spectrum was measured by vibration table test. A fractal dimension range is selected that makes the peeling area below a critical threshold. The critical threshold is determined by the bonding strength distribution of the unpeeled area through micro-CT scanning. The interface bonding strength predicted by the correlation model and the vibration table test results are mutually verified and used together to determine the optimal fractal dimension range.

3. The method for composite molding of embedded fins of a phase change energy storage unit according to claim 1, characterized in that: The method for determining the taper ratio in step 2 specifically includes: A high-speed particle imaging system is set at the inlet of the transparent mold to capture the streamline trajectory of the phase change material; Extract streamline deflection angle data and establish a functional relationship between deflection angle and taper ratio; The filling cavity volume of the cavity corners under different tapers is scanned in real time by micro-focus X-ray; Select the taper ratio that makes the maximum cavity volume smaller than the set limit and minimizes the streamline deflection angle.

4. A composite molding method for embedded fins of a phase change energy storage unit according to claim 1, characterized in that: In the multi-stage pressure control in step 3, the switching points of different stages are dynamically determined by the following method: An ultrasonic transmitter-receiver array is installed in the middle of the mold to transmit detection signals with adjustable pulse frequency; Real-time analysis of the receiving end signal amplitude attenuation rate and phase offset. The phase offset is used to calibrate the melt flow rate, and a mapping relationship is established with the amplitude attenuation rate and the melt front position. When it is determined based on the mapping relationship that the melt front reaches the set position of the cavity, the second stage pressure increase is triggered; The real-time filling volume is calculated by volume integration of the ultrasonic signal. When the filling volume reaches the set threshold, the third stage of reverse suction is triggered. At the same time, the gas pressure change in the cavity is monitored by the pressure differential sensor. The gas pressure data is used to verify the integrity of the reverse suction.

5. The method for composite molding of embedded fins of a phase change energy storage unit according to claim 1, characterized in that: When applying the rotating magnetic field in step 4, the direction of the rotating magnetic field is optimized according to the following process: A cylindrical sample of phase change material containing magnetic nano-additives was prepared, and micro thermocouples were embedded in the axial and radial directions of the sample. A constant heat flux density is applied under different magnetic field direction angles, and the ratio of axial to radial thermal conductivity is calculated based on thermocouple measurement data as the first quantitative indicator of thermal conductivity anisotropy; The surface temperature distribution of the sample is captured by an infrared thermal imager, and the second quantitative index of thermal conductivity anisotropy is calculated based on the temperature gradient distribution; The first quantitative index and the second quantitative index are weightedly fused to calculate the comprehensive thermal conductivity anisotropy, and the magnetic field direction angle range that makes the comprehensive thermal conductivity anisotropy reach the maximum value is selected.

6. A composite molding method for embedded fins of a phase change energy storage unit according to claim 1, characterized in that: The specific temperature range near the crystallization point in step 4 is calibrated as follows: The lattice constants of phase change materials are collected in real time using synchrotron X-ray diffractometer; The corresponding function between the lattice constant change rate and the volume shrinkage rate is calculated by first principles; Locate the inflection point of volume shrinkage on the differential scanning calorimetry curve; The temperature window is expanded forward and backward with the inflection point as the magnetic field application range.

7. The method for composite molding of embedded fins of a phase change energy storage unit according to claim 1, characterized in that: The step 5 is also included: generating an in-situ oxidation enhancement layer, which specifically includes: The fins are placed in a closed reaction chamber with controllable oxygen partial pressure, and a mixture of inert gas and oxygen is introduced; Heating with a segmented heating curve: in the first stage, heating to the intermediate temperature at a set rate and keeping the temperature, so as to pre-oxidize the surface of the aluminum substrate; In the second stage, a halogen-containing activation gas is introduced, and the temperature is continued to rise to the target temperature and maintained to form a nano-needle oxide layer; The morphology of the oxide layer was characterized by scanning electron microscopy, and a combination of process parameters was selected that made the contact angle of the phase change material smaller than a critical value.

8. A composite molding method for embedded fins of a phase change energy storage unit according to claim 7, characterized in that: The component ratio of the halogen-containing activation gas is optimized according to the following process: Samples treated with different gas compositions were prepared, and the thickness and refractive index of the oxide layer were measured using ellipsometer. An atomic force microscope is used to scan the three-dimensional surface topography and calculate the surface energy components; Establishing a database of physical properties of the oxide layer, the database including mapping relationships between thickness, refractive index, surface energy components and activation gas compositions; The contact angle hysteresis curve of the molten phase change material on the modified surface was measured by the sessile drop method; constructing a gas component-wettability correlation model based on the physical property database and the contact angle hysteresis curve; The activated gas component ratio is selected so that the contact angle hysteresis value is lower than the set threshold and the surface energy component is within the target range.

9. A composite molding method for embedded fins of a phase change energy storage unit according to any one of claims 1 to 8, characterized in that: Validation for aerospace applications includes: The random vibration spectrum specified in the MIL-STD-810G standard is applied through a vibration table, and the frequency range covers the set wide frequency band; An infrared thermal imager was used to monitor the temperature field uniformity of the fin-PCM interface during vibration; After the vibration is completed, a micro-focus CT scan is performed to reconstruct the interface micro-crack distribution model; When the total volume score of microcracks is lower than the set limit, it is judged to be qualified.

10. The method for composite molding of embedded fins of a phase change energy storage unit according to claim 1, characterized in that: The action time of the reverse suction pressure in step 3 is determined as follows: A mass spectrometer is installed at the exhaust port of the mold, and the mass-to-charge ratio signal of the characteristic volatiles of the phase change material is tracked in the selected ion monitoring mode; A correlation model between the concentration of volatiles in a phase change material in a gas and the amount of residual cavitation at the interface is established, wherein the model establishes a quantitative relationship between the concentration and the amount of residual cavitation through calibration experiments; converting the real-time monitored volatile concentration into an estimated value of cavitation residual amount based on the correlation model; The pumping process is terminated when the estimated value of the cavitation residual amount is lower than the safety threshold and the concentration decay rate for three consecutive sampling cycles is less than the set tolerance.

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