Cooperative phase change uniform temperature type thermal buffer with overload adaptability

Abstract

The invention discloses a synergetic phase change uniform temperature type thermal buffer with overload adaptability, and relates to the technical field of aerospace thermal management and heat dissipation of high-power electronic devices. The uniform-temperature type heat buffer comprises a heat storage cavity, a heat pipe assembly, a liquid filling opening and a fractal tree rib structure arranged in the heat storage cavity. The condensation section shell, the heat storage cavity base body and the three-dimensional fractal tree rib structure of the heat pipe assembly are integrally formed through additive manufacturing, so that a continuous metal heat conduction channel is formed, and the interface heat resistance between the heat pipe assembly and the heat storage cavity is reduced. The fractal tree rib structure is of a main vein-branch-tip step-by-step bifurcated self-similar topological configuration in the direction away from the condensation section of the heat pipe assembly, is used for rapidly expanding heat from the condensation section to the phase change material in the heat storage space, and serves as a crystallization nucleation framework in the phase change material solidification process. Cooperative coupling of rapid heat transfer of the heat pipe and latent heat storage of the phase change material is achieved, the internal temperature gradient of the phase change material can be reduced, and the temperature uniformity, the cycling stability and the high-overload working condition adaptive capacity in the heat buffering process are improved.

Description

Technical Field

[0001] This invention relates to the field of aerospace thermal management and heat dissipation technology for high-power electronic devices. Specifically, it relates to a synergistic phase change isothermal thermal buffer suitable for high overload and variable operating conditions such as ultra-high speed aircraft. Background Technology

[0002] During maneuvering flight, near-space hypersonic vehicles face extreme thermo-mechanical coupling environments for their internal guidance systems, phased-array radars, and other sophisticated electronic equipment. On one hand, the instantaneous switching of equipment generates high-frequency, high-density pulsed heat flows; on the other hand, the vehicle must withstand large-amplitude, variable-direction mechanical overloads (hypergravity). Existing thermal management solutions have significant technical shortcomings: while single heat pipes possess extremely high equivalent thermal conductivity, enabling rapid heat transport, their operation relies on capillary force. Under high overload conditions, volume forces severely disrupt the capillary balance at the gas-liquid interface, hindering liquid reflux and easily triggering capillary limit (drying-out failure), lacking heat buffering capacity and exhibiting poor thermal shock resistance. Although single phase change thermal storage devices utilize the latent heat of fusion of materials for thermal buffering, phase change materials generally suffer from the inherent defect of extremely low thermal conductivity. Under high overload, natural convection is strongly suppressed, leading to heat conduction dominating the melting process, slow phase change interface advancement, extreme internal temperature gradient, and poor surface temperature uniformity of the heat storage cavity, which fails to meet the temperature control requirements of precision components. Therefore, there is an urgent need for a thermal management device that can deeply couple rapid heat conduction with efficient thermal buffering, and maintain the coordinated stability of gas-liquid and solid-liquid phase changes even under hypergravity environments. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a synergistic phase change isothermal thermal buffer with overload adaptability that can effectively cope with high heat flux density, pulsed and strong transient thermal load impacts.

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A synergistic phase change isothermal thermal buffer with overload adaptability, comprising: A heat storage chamber is provided with a liquid filling port, through which phase change material is filled into the heat storage chamber; A heat pipe assembly having an evaporation section and a condensation section; the evaporation section is disposed at a heat source, and the condensation section is at least partially embedded in the heat storage cavity; A three-dimensional fractal tree rib structure is provided in the heat storage cavity. The fractal tree rib structure is immersed in the phase change material and divides the internal space of the heat storage cavity into multiple interconnected local heat storage units. This shortens the heat conduction path of the heat pipe assembly releasing heat into the phase change material in the condensation section, thereby suppressing the local migration and thermal stratification of the liquid phase change material under overload conditions.

[0005] The fractal tree rib structure follows a self-similar fractal law, exhibiting a topological configuration of main vein-branch-terminus branching along the direction away from the condensation section of the heat pipe assembly. This structure is used to progressively extend the heat introduced from the condensation section to different regions of the heat storage space. The fractal tree rib structure not only serves as a thermally conductive framework during the melting process of the phase change material, enhancing heat flow expansion and homogenization, but also as a nucleation framework during solidification, inducing uniform solidification of the phase change material and thus improving the cyclic operational stability of the heat buffer.

[0006] Furthermore, the fractal tree rib structure adopts a bifurcation or multifurcation form, and its fractal dimension is preferably 1.5 to 2.5, so as to take into account the heat flow expansion coverage, structural specific surface area and additive manufacturing feasibility.

[0007] Furthermore, the length and diameter of each branch of the fractal tree rib structure satisfy a preset scaling relationship, so that the heat flow can be extended step by step in different scale ranges, shortening the internal heat conduction path of the phase change material and reducing the temperature non-uniformity in the heat storage space.

[0008] Furthermore, the bifurcation angle of the fractal tree rib structure is preferably 30° to 60°, and the number of fractal levels is preferably 2 to 4, in order to avoid excessive local heat flow concentration or excessively fine final branches leading to manufacturing defects and increased thermal resistance.

[0009] Furthermore, the heat pipe assembly is provided with a liquid wick structure inside. The liquid wick structure is any one of a sintered liquid wick, a grooved liquid wick, or a composite liquid wick, in order to maintain the working fluid reflux capability under high overload or variable posture conditions and ensure the stable operation of the heat pipe assembly.

[0010] Furthermore, the fractal tree rib structure is immersed in the phase change material and divides the heat storage space into multiple interconnected local heat storage units, thereby suppressing the local migration and thermal stratification of the liquid phase change material under overload conditions.

[0011] Furthermore, the filling port is equipped with a detachable mechanical seal interface or a welded seal interface to seal the heat storage cavity after the phase change material is filled.

[0012] Beneficial effects Compared with the prior art, the present invention has the following beneficial effects: 1. This invention synergistically couples the rapid heat transport capability of the heat pipe assembly with the latent heat storage capability of the phase change material within the same module. The heat storage cavity can prevent the heat pipe from reaching its heat transfer limit. The heat pipe is added to this cavity, which allows the phase change material inside the cavity to melt better and more uniformly. The heat storage cavity and the heat pipe reinforce each other, realizing rapid heat introduction, uniform storage and rapid heat export, which can effectively cope with high heat flux density, pulse and strong transient heat load impact.

[0013] 2. The fractal tree rib structure forms multi-point support and local thermal storage unit division in the thermal storage space, which helps to suppress the local migration and thermal stratification of liquid phase change materials under high overload and variable posture conditions, and improves the working reliability of the device in complex force-thermal coupling environment.

[0014] 3. The fractal tree rib structure adopts a self-similar topology that expands step by step from the main vein to the branch to the end, which can expand the concentrated heat flow input from the heat pipe condensation section in the heat storage space in multiple scales, so that the heat input is transformed into the dispersed transfer in the volume domain, significantly shortening the internal heat conduction path of the phase change material, increasing the effective heat exchange area, and reducing the radial and axial temperature gradient inside the phase change material.

[0015] 4. The fractal tree rib structure not only serves as a heat-conducting skeleton to enhance thermal diffusion during the melting stage, but also serves as a crystal nucleation skeleton to induce uniform nucleation and solidification of the phase change material during the solidification stage, thereby improving the interface propagation consistency and repeatable cycle stability during the phase change cycle process.

[0016] 5. The heat pipe assembly condenser section shell, the heat storage cavity substrate, and the fractal tree rib structure are integrally formed through additive manufacturing, forming a continuous metal heat conduction path from the heat pipe assembly to the inside of the heat storage cavity. This avoids the problems of high interfacial contact thermal resistance, lag in thermal response, and poor connection stability that exist in traditional assembly connections, thereby improving the efficiency of heat transfer to the heat storage module. Attached Figure Description

[0017] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings, in which: Figure 1 This is a structural diagram of a uniform temperature thermal buffer in an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of the internal structure of the heat storage cavity in an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram illustrating the working principle of the uniform temperature thermal buffer in an embodiment of the present invention.

[0020] In the diagram, 1 – heat storage cavity, 2 – heat pipe assembly, 3 – liquid filling port, and 4 – fractal tree rib structure. Detailed Implementation

[0021] Figure 1 This is a structural diagram of a uniform temperature heat buffer according to an embodiment of the present invention. The uniform temperature heat buffer includes a heat storage chamber 1 and a heat pipe assembly 2. A liquid filling port 3 is provided on the heat storage chamber 1. A fractal tree rib structure 4 is provided inside the heat storage chamber 1.

[0022] It should be noted that the heat pipe assembly 2, the fractal tree rib structure 4, and the phase change material are not simple, independent parallel units, but rather an integrated design centered around the coordinated regulation of heat in both spatial and temporal dimensions. Specifically, the heat pipe assembly 2 is responsible for rapidly transporting the transient heat load generated by the heat source to the interior of the heat storage cavity 1, the fractal tree rib structure 4 is responsible for the multi-scale expansion and redistribution of the input heat flow within the heat storage space, and the phase change material is responsible for absorbing and releasing heat in the form of latent heat. Together, these three components constitute a coupled homogeneous thermal buffer system.

[0023] Laser selective melting additive manufacturing technology was used to integrally form the outer shell of the heat storage cavity 1 and the heat pipe assembly 2. After forming, a coordinate measuring machine was used for precision inspection to ensure that the deviation of all structural dimensions was controlled within ±0.1 mm to meet the requirements of high-precision assembly. The heat pipe assembly 2 has a sintered liquid wick inside, one end of which (evaporation section) is tightly connected to the heat source, and the other end (condensation section) is tightly thermally connected to the bottom of the heat storage cavity 1 for heat exchange. Phase change material was poured in through the filling port 3 on the side wall of the heat storage cavity 1 and sealed with a mechanical seal interface to complete the preparation of the entire sample. Under high overload or variable posture conditions, liquid phase change material is prone to local migration, gravitational agglomeration, and thermal stratification, resulting in a decrease in heat storage efficiency and uneven solidification process. The heat pipe assembly 2 maintains stable reflux of the working fluid by using a liquid wick structure, and the heat storage space is supported at multiple points and divided into local units by using a fractal tree rib structure 4, thereby reducing the large-scale flow of the liquid phase change material and improving the temperature stability and cycle reliability of the device under complex mechanical environment.

[0024] Figure 2 This is a schematic diagram of the internal structure of the heat storage cavity in an embodiment of the present invention. The heat storage cavity 1 is designed with a fractal tree rib structure 4. Unlike conventional parallel straight ribs, needle ribs, or grid rib structures, the fractal tree rib structure 4 of the present invention has a self-similar topological feature of hierarchical branching. In the region near the condensation section of the heat pipe assembly 2, it maintains a large main vein cross section to bear a high heat flux density. In the region away from the condensation section, the heat flux is further diffused to the outer region of the heat storage space through multi-level refined branches, so that the heat is distributed hierarchically from the macroscopic to the microscopic scale, thereby improving the uniformity of the overall temperature field of the phase change material.

[0025] Furthermore, the fractal tree rib structure 4 serves to enhance thermal conductivity during the melting stage and to induce heterogeneous nucleation during the solidification stage. Because the fractal tree rib structure 4 has a large specific surface area and a uniformly distributed skeletal network, it can provide multiple nucleation initiation sites for the phase change material, promoting simultaneous advancement of the solidification interface from multiple points and avoiding delayed solidification in localized areas, thereby improving the repetitive working performance of the homogeneous thermal buffer.

[0026] The length and diameter of each branch are progressively reduced according to a specific fractal dimension, forming a highly efficient heat flow expansion channel. This structure is embedded in the subsequently infused phase change material to significantly improve overall thermal conductivity.

[0027] Specifically, fractal tree rib structure 4 adopts a binary branching form, with the total number of branches being... N ( N ≥ 2), the length and diameter of each branch satisfy the following scaling relationship:

[0028] in, and These are the length and diameter of the main vein (first level), respectively. The length fractal coefficient, Let be the diameter fractal coefficient, and satisfy 0 < α <1, 0< β <1. According to fractal geometry theory, the fractal dimension of this structure is... D It can be determined by the number of branches and the diameter scaling ratio:

[0029] In the formula, n The number of branches at each level (in this embodiment, it is a binary branch, i.e.) n = 2). By making a reasonable choice and This can increase the fractal dimension. D Within the range of 1.5 to 2.5, efficient expansion and uniform distribution of heat flow along the tree rib network are achieved.

[0030] Figure 3 This is a schematic diagram illustrating the working principle of the uniform temperature heat buffer in this embodiment of the invention. It should be noted that the heat pipe assembly 2, the fractal rib structure 4, and the phase change material in this invention are not independent parallel units, but rather an integrated design centered on the coordinated control of heat in both time and space dimensions. Specifically, the heat pipe assembly 2 is responsible for rapidly introducing external transient heat loads into the heat storage cavity 1; the fractal rib structure 4 is responsible for multi-scale expansion and distribution of the input heat flow to different heat storage regions; and the phase change material undertakes the function of latent heat absorption and release. Together, these three components constitute a coupled heat buffer system.

[0031] Phase 1: Thermal Shock Absorption and Rapid Dissipation (Heat Pipe Dominant). When the guidance system or electronic devices are activated instantaneously, a high heat flux density acts on the evaporation section of heat pipe assembly 2. The working fluid inside heat pipe assembly 2 evaporates rapidly in a vacuum environment, and the vapor carries latent heat to the condensation section. At this time, because the initial temperature of the heat storage chamber 1 is below the phase change point, the temperature of the condensation section is relatively low, and the vapor rapidly condenses and releases heat. This process is completed within seconds or even milliseconds, efficiently dissipating the pulsed heat flux and avoiding the formation of temperature spikes on the heat source surface.

[0032] Phase Two: Volume Diffusion and Latent Heat Storage (Dominated by the Heat Storage Chamber). Heat transferred to the condensation section enters the fractal rib structure 4 with extremely low thermal resistance due to the integrally molded structure. This structure follows fractal principles, with heat flow rapidly expanding along the main vein to each branch, transforming the point or surface heat source concentrated at the bottom into a volumetric heat source filling the entire heat storage chamber 1. After absorbing heat, the phase change material begins to melt, and the solid-liquid phase change interface uniformly advances along the fractal rib structure 4 from the root to the tip and from the bottom to the top. During this process, even with external overload, the skeletal support of the fractal ribs prevents natural convection instability of the liquid phase material due to density differences or volume forces, ensuring a uniform and controllable melting process.

[0033] Phase 3: Intermittent Heat Release and Reversible Recovery (Collaborative Reflux). When the equipment enters an intermittent period (heat source power reduced or shut down), the temperature of the evaporation section drops. At this time, the heat stored in the heat storage chamber 1 is conducted back to the condensation section through the fractal rib structure. The working fluid inside the heat pipe assembly 2 stops evaporating, and the liquid in the condensation section accumulates and flows back to the evaporation section by capillary force (the heat pipe operates in reverse). This process slowly and controllably releases the latent heat in the heat storage chamber 1 to the external cold source. At the same time, the fractal rib structure 4 acts as a crystal framework, inducing the phase change material to solidify on its surface, avoiding void defects caused by supercooling or volume shrinkage, and ensuring the cyclic stability of the system.

[0034] Throughout the entire working cycle, heat pipe assembly 2 acts as a high-speed switch and heat transporter, while heat storage chamber 1 acts as a reservoir and voltage regulator. The two are seamlessly connected in space, complementary in time (fast heat pipe response, large heat storage chamber capacity), and mutually supportive in mechanics, jointly achieving effective suppression of thermal shock and orderly management of heat under complex overload conditions.

Claims

1. A synergistic phase change uniform temperature thermal buffer with overload adaptability, characterized in that, include: A heat storage chamber (1) is provided with a filling port (3), through which phase change material is filled into the heat storage chamber (1); The heat pipe assembly (2) has an evaporation section and a condensation section; the evaporation section is located at the heat source, and the condensation section is at least partially embedded in the heat storage cavity (1); A three-dimensional fractal tree rib structure (4) is provided in the heat storage cavity (1). The fractal tree rib structure (4) is immersed in the phase change material and divides the internal space of the heat storage cavity (1) into multiple interconnected local heat storage units, so as to shorten the heat conduction path of the heat pipe assembly (2) releasing heat into the phase change material in the condensation section, thereby suppressing the local migration and thermal stratification of the liquid phase change material under overload conditions.

2. The synergistic phase change uniform temperature thermal buffer according to claim 1, characterized in that, The condenser section shell of the heat pipe assembly (2), the substrate of the heat storage cavity (1), and the three-dimensional fractal tree rib structure (4) are integrally formed by additive manufacturing to form a continuous metal heat conduction path between the heat pipe assembly (2) and the heat storage cavity (1) and reduce the interface thermal resistance.

3. The synergistic phase change uniform temperature thermal buffer according to claim 1, characterized in that, The three-dimensional fractal tree rib structure (4) follows the self-similar fractal law and has a topological configuration of main vein-branch-terminus branching along the direction away from the condensation section of the heat pipe assembly (2). It is used to extend the heat introduced by the condensation section of the heat pipe assembly (2) to different regions of the heat storage space in stages, and to serve as a heat-conducting skeleton and crystal nucleation skeleton in the melting and solidification process of the phase change material, so as to reduce the internal temperature gradient of the phase change material and improve the temperature uniformity and cycle stability in the heat buffer process.

4. The synergistic phase change uniform temperature thermal buffer according to claim 3, characterized in that, The fractal tree rib structure (4) adopts a binary or multi-branched form, with each branch gradually decreasing in size along the direction of heat expansion, and its fractal dimension is... D The fractal dimension is 1.5–2.

5. D for: in, n This represents the number of branches at each level. is the diameter fractal coefficient.

5. The synergistic phase change uniform temperature thermal buffer according to claim 3, characterized in that, The lengths and diameters of the branches at each level of the fractal tree rib structure (4) satisfy a scaling relationship: in, and The first i The length and diameter of the first-order branches, and These are the length and diameter of the main vein, respectively. The length fractal coefficient, Let be the diameter fractal coefficient, and satisfy 0 < . < 1, 0 < < 1.

6. The synergistic phase change uniform temperature thermal buffer according to claim 3, characterized in that, The bifurcation angle of the fractal tree rib structure (4) is 30° to 60°, and the fractal level is... N It is classified as level 2 to 4.

7. The synergistic phase change uniform temperature thermal buffer according to any one of claims 1-6, characterized in that, The heat pipe assembly (2) is provided with a liquid wick structure inside. The liquid wick structure is a sintered liquid wick, a grooved liquid wick, or a composite liquid wick, which is used to maintain the working fluid reflux capability under high overload or variable posture conditions, thereby improving the heat transfer stability of the heat pipe assembly.

8. The synergistic phase change uniform temperature thermal buffer according to claim 1, characterized in that, The surface of the fractal tree rib structure (4) is configured as a roughened surface, a microporous surface, or an additively manufactured native rough surface to improve the heterogeneous nucleation ability and interfacial heat transfer efficiency of the phase change material during solidification.

9. The synergistic phase change uniform temperature thermal buffer according to claim 1, characterized in that, The filling port is equipped with a detachable mechanical seal or a welded seal interface for sealing the heat storage space after the phase change material is injected.

10. The synergistic phase change uniform temperature thermal buffer according to claim 1, characterized in that, The fractal tree rib structure (4) has a large main vein cross section in the region near the condensation section of the heat pipe assembly (2) and forms multi-level refined branches in the region far from the condensation section of the heat pipe assembly (2) to construct a multi-scale heat flow distribution network that expands from the center to the periphery.

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