Loop heat pipe evaporation section structure and loop heat pipe system

Abstract

The application relates to a loop heat pipe evaporation section structure and a loop heat pipe system, wherein the loop heat pipe evaporation section structure comprises a capillary core, an outer surface of the capillary core is provided with a composite channel system for working medium flow, the composite channel system comprises a plurality of axial straight channels and spiral channels, a cross section shape of the spiral channels changes along an axial direction of the capillary core, so that the capillary core generates a non-uniform capillary pumping force distribution along the axial direction, and the capillary core is used for adaptively matching a heat flux density distribution of the evaporation section in the axial direction; a metal shell is sleeved on the outer side of the capillary core, and the capillary core is in interference fit with the metal shell; an interface layer is arranged between the capillary core and the metal shell, the interface layer is composed of a flexible material with a thermal expansion coefficient between that of the capillary core material and that of the metal shell material, is used for dynamically compensating expansion differences of the two when temperature changes, and maintains close contact of the interface; a saddle is sleeved on the outer side of the metal shell, and a prefabricated thermal interface material layer is arranged between the saddle and the metal shell.

Description

Technical Field

[0001] This application relates to the field of aerospace thermal control technology, and more specifically, to a loop heat pipe evaporation section structure and a loop heat pipe system. Background Technology

[0002] Loop heat pipes, due to their high heat transfer efficiency, flexible arrangement, and good environmental adaptability, have become a core component of spacecraft thermal control systems. However, with the increasing complexity of spacecraft missions, loop heat pipes face the following technical challenges: On high-speed rotating platforms (such as antenna equipment, with a rotation speed of 27-45 r / min), centrifugal acceleration leads to uneven distribution of the working fluid, affecting the stability of capillary wick liquid supply and heat transfer efficiency. Spacecraft undergo severe temperature cycling in orbit (such as from -65°C to 100°C). The difference in thermal expansion coefficients between different materials leads to micro-gaps at the assembly interface, increasing contact thermal resistance. The intense vibration environment during launch can easily cause the pipe support connections to loosen, affecting the stability of the heat transfer path; Traditional loop heat pipes are difficult to adapt to operating conditions with uneven axial heat flux density, leading to local overheating or reduced heat transfer capacity. Summary of the Invention

[0003] The purpose of this application is to provide a loop heat pipe evaporator section structure and a loop heat pipe system that can solve the technical problems mentioned in the background art.

[0004] To achieve the above objectives, in a first aspect, the present invention provides a loop heat pipe evaporation section structure, comprising: The capillary wick has a composite channel system on its outer surface for the flow of working fluid. The composite channel system includes multiple axially extending straight channels and at least one spiral channel. The cross-sectional shape of the spiral channel changes in a gradient along the axial direction of the capillary wick, so that the capillary wick generates a non-uniform capillary suction force distribution along its axial direction, which is used to adaptively match the heat flux density distribution along the axial direction of the evaporation section. A metal housing is fitted onto the outside of the capillary core, and the capillary core and the metal housing are interference-fitted. An interface layer is disposed between the capillary core and the metal shell. The interface layer is made of a flexible material with a thermal expansion coefficient between that of the capillary core material and the metal shell material. It is used to dynamically compensate for the expansion difference between the two when the temperature changes, and maintain close contact at the interface. A saddle, fitted onto the outside of the metal housing, and a prefabricated thermal interface material layer disposed between the saddle and the metal housing.

[0005] In an optional embodiment, the cross-section of the spiral groove is trapezoidal or rectangular; The ratio of the groove depth to the groove width of the spiral groove, and / or the pitch of the spiral groove, varies monotonically from the expected high heat flux density end of the capillary wick to the low heat flux density end.

[0006] In an optional embodiment, the interface layer comprises a flexible graphite composite material layer; The thickness of the interface layer is 0.01 mm to 0.1 mm, and the coefficient of thermal expansion of the interface layer within the operating temperature range satisfies: the coefficient of thermal expansion of the capillary wick < the coefficient of thermal expansion of the interface layer ≤ the coefficient of thermal expansion of the metal shell.

[0007] In an optional embodiment, the prefabricated thermal interface material layer includes a thermally conductive pad containing phase change microcapsules.

[0008] In an optional embodiment, the metal housing is provided with an external annular groove on the outside of the area where it is welded to the end cap for accommodating the flow of cooling medium. The central channel inside the capillary core has a flared inlet at its entrance, with a cone angle of 15° to 60°.

[0009] In an optional embodiment, in the composite channel system, the depth of the straight channel is greater than the depth of the spiral channel; The straight groove has a square cross-section with a side length of 0.8 mm to 1.2 mm; the spiral groove has a groove depth of 0.4 mm to 0.6 mm.

[0010] In a second aspect, the present invention provides a loop heat pipe system, including the loop heat pipe evaporator section structure described in any of the foregoing embodiments, as well as a condenser module, an intelligent temperature control module, and an anti-vibration structure module; The condenser module is connected to the loop heat pipe evaporation section structure and includes a condenser pipe, which is supported by a pipe support. The intelligent temperature control module includes a semiconductor cooling chip, a heating element, a high-precision temperature sensor, and a PID controller, all installed in the liquid reservoir. The pipe support and the spacecraft satellite heat dissipation panel mounting interface are integrally formed; An elastic clamp and a silicone rubber damping pad are provided between the pipe support and the condenser pipe. Vacuum brazing is used to connect the liquid reservoir and the condenser pipeline for connecting dissimilar materials.

[0011] In an optional embodiment, a thermally conductive phase change pad with adhesive backing is pre-placed between the pipe support and the condensation pipe. The gap for gap vacuum brazing is 0.15-0.25mm, and Al-Si brazing filler metal is used.

[0012] In an optional embodiment, the capillary wick is further provided with an eccentrically arranged auxiliary flow channel. The arrangement direction of the auxiliary flow channel is related to the expected rotation direction of the system, and is used to guide the liquid working fluid to gather towards the evaporation end in a centrifugal environment. The centrifugal acceleration compensation coefficient of the loop heat pipe system under high-speed centrifugal environment is 0.3-0.5g.

[0013] In an optional implementation, the PID controller in the intelligent temperature control module includes a temperature fluctuation suppression algorithm, which dynamically adjusts the operation of the semiconductor cooling chip and the heating chip by collecting data from the high-precision temperature sensor in real time.

[0014] The loop heat pipe evaporator section structure in this application can improve the heat transfer adaptability and interface stability of the evaporator section. At the same time, the loop heat pipe system solves the problems of reliability, temperature control accuracy and process consistency in the high dynamic environment of vibration and centrifugation by introducing an intelligent temperature control module, an anti-vibration structure system and process optimization.

[0015] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of the loop heat pipe evaporation section of this application; Figure 2 This is a schematic diagram of the capillary core structure of this application; Figure 3 This is a schematic diagram of the fit between the capillary core and the metal shell in this application; Figure 4 This is a schematic diagram of the composite channel system of this application; Figure 5 This is a schematic diagram of the mating structure between the saddle and the metal housing in this application; Figure 6 This is a schematic diagram of the saddle structure of this application; Figure 7 This is a schematic diagram of the loop heat pipe system of this application.

[0018] icon: 1-Capillary wick; 11-Flare-shaped opening; 2-Composite channel system; 21-Straight channel; 22-Helical channel; 3-Metal casing; 4-Saddle; 41-Prefabricated thermal interface material layer; 5-Condensate piping; 6-Liquid reservoir; 7-Condenser module. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] In the description of this application, it should be noted that the terms "inner" and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0021] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "setup" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0022] The loop heat pipe evaporator section structure and loop heat pipe system in this application mainly improve the structure of existing heat pipes and the composition of loop heat pipe systems, so that the loop heat pipe evaporator section structure has dynamic adaptive heat transfer capability, and at the same time can endow the loop heat pipe system with vibration and centrifugal resistance for high dynamic environments.

[0023] See Figures 1-6 The loop heat pipe evaporation section structure in this invention includes a capillary wick 1, a metal shell 3, an interface layer, and a saddle 4 as its main structure.

[0024] The capillary core 1 is sintered from nickel powder and is cylindrical in shape with an outer diameter of 16 mm and a length of 150 mm. A composite channel system 2 for the flow of working fluid is formed on its outer surface through precision machining.

[0025] The composite channel system 2 includes: eight straight grooves 21 extending along the axial direction of the capillary core 1, and one spiral groove 22 spirally surrounding the capillary core 1. The cross-sectional shape of the spiral groove 22 varies in gradient along the axial direction of the capillary core 1, and the groove depth of the straight grooves 21 is greater than the groove depth of the spiral groove 22.

[0026] Eight straight grooves 21 are evenly distributed along the circumference. The cross-section of the groove is square, and the side length of the square groove is 0.8-1.2mm. Preferably, the side length of the square groove is 1.0mm.

[0027] The ratio of the groove depth to the groove width of the spiral groove 22, and / or the pitch of the spiral groove 22, monotonically change from the expected high heat flux density end of the capillary wick 1 to the low heat flux density end. That is, the ratio of the groove depth to the groove width of the spiral groove 22, and / or the pitch of the spiral groove 22, gradually increase or decrease along the axial direction from the evaporation end to the condensation end, forming a non-uniform capillary force distribution to compensate for the working fluid agglomeration effect caused by centrifugal force.

[0028] Specifically, the cross-section of the spiral groove 22 is trapezoidal or rectangular, and the groove depth is 0.4mm to 0.6mm. Specifically, one spiral groove 22 spirally surrounds the capillary core 1 in the form of a single-start thread. The groove depth gradually changes from 0.55mm at the evaporation end to 0.45mm at the condensation end, while the groove width remains unchanged. The pitch of the spiral groove 22 gradually increases from 0.6mm at the evaporation end to 0.8mm at the condensation end.

[0029] The above configuration allows the capillary wick 1 to generate a non-uniform capillary suction force distribution along its axial direction, which is used to adaptively match the heat flux density distribution along the axial direction of the evaporation section.

[0030] Specifically, from the perspective of non-uniform capillary force distribution, the capillary suction force varies at different axial positions because the geometric parameters such as the groove depth and pitch of the spiral groove 22 gradually change along the axial direction. The capillary force is strongest at the evaporation end, which can effectively capture and distribute the working fluid; the capillary force weakens at the condensation end, which is conducive to the smooth discharge of steam.

[0031] From the perspective of adaptive heat flow matching, when the axial heat flow distribution in the evaporation section is uneven, such as when the heat load is high at one end, the aforementioned gradient-changing channels can automatically adjust the flow rate and evaporation intensity of the working fluid in that region through the difference in local capillary force, thereby achieving self-optimization of heat transfer and avoiding local drying or overheating.

[0032] The metal shell 3 is fitted onto the outside of the capillary core 1, and the capillary core 1 and the metal shell 3 are interference-fitted. Specifically, the metal shell 3 is a thin-walled round tube of 316L stainless steel, and its inner diameter is interference-fitted with the outer diameter of the capillary core 1, with an interference amount of 0.025mm.

[0033] An interface layer with a thickness of 0.01 mm to 0.1 mm is disposed between the outer surface of the capillary core 1 and the inner wall of the metal shell 3. This interface layer is selected as a flexible graphite composite material layer with a thickness of 0.05 mm. The flexible graphite composite material layer may include a porous flexible metal felt, an elastomer material layer filled with highly thermally conductive filler, or a composite material with a layered structure. The coefficient of thermal expansion of the flexible graphite composite material layer is approximately 12 × 10⁻⁶. -6 / K, which is between the thermal expansion coefficient of capillary wick 1 and the thermal expansion coefficient of metal shell 3, is used to dynamically compensate for the expansion difference between the two when the temperature changes, and maintain close contact at the interface.

[0034] When the temperature rises, the expansion of the stainless steel shell 3 is greater than that of the capillary wick 1. At this time, the interface layer, due to its moderate coefficient of thermal expansion and flexibility, can actively expand to fill any micro-gaps that may occur; when the temperature drops, its elasticity can maintain a certain contact pressure, enabling dynamic dimensional compensation.

[0035] Meanwhile, flexible graphite has high thermal conductivity, with a thermal conductivity coefficient >300 W / (m·K), which ensures efficient heat conduction while compensating for size, thus achieving the technical goal of reducing interfacial thermal resistance.

[0036] The evaporator saddle 4 is mounted on the outside of the metal shell 3 and can be a 6061 aluminum alloy machined part. It is clamped to the outside of the metal shell 3 by a prefabricated thermal interface material layer 41.

[0037] The prefabricated thermal interface material layer 41 is a phase change thermally conductive pad with a thickness of 0.2 mm. Specifically, the prefabricated thermal interface material layer 41 includes a thermally conductive pad containing phase change microcapsules. It is solid at room temperature and softens at a phase change temperature of about 45°C, which can completely fill the assembly gap between the saddle 4 and the metal shell 3.

[0038] The loop heat pipe evaporation section structure in this application can achieve effective and sufficient interface filling through the prefabricated thermal interface material layer 41, minimizing the uncertainty of traditional manual application of thermal grease and eliminating assembly gap thermal resistance.

[0039] At both ends of the stainless steel metal shell 3, specifically on the outer side of the area where it is welded to the end cap, annular grooves 1 mm wide and 0.5 mm deep are machined. During welding, thin copper tubes are embedded in the grooves and cooling water is circulated through them to form localized microchannel cooling.

[0040] By confining the high temperature of welding to the weld area, heat is prevented from being conducted to the capillary core 1, which could cause it to sinter or deform, thus ensuring the integrity of the gradient channel structure.

[0041] The inlet end of the central channel inside the capillary core 1 is provided with a flared opening 11. The cone angle of the flared opening 11 is 15-60°, preferably 30°, which can facilitate the smooth flow of liquid working fluid into the central channel, reduce flow loss at the inlet, improve the system flow capacity, and reduce flow resistance.

[0042] Combination Figure 7 This application also provides a loop heat pipe system, including the above-mentioned loop heat pipe evaporator section structure, as well as a condenser module 7, an intelligent temperature control module, and an anti-vibration structure module, which mainly constitutes an anti-vibration and anti-centrifugal loop heat pipe system for high dynamic environments.

[0043] The intelligent temperature control module includes a semiconductor cooling chip, a heating chip, a high-precision temperature sensor, and a PID controller, all located in the liquid reservoir 6.

[0044] The vibration-resistant structural module is used to suppress the performance degradation of the loop heat pipe system under vibration and centrifugal environment, and is mainly reflected in the form of integrated pipe support, flexible pipe fixing and key brazing connection.

[0045] The integrated pipe support angle, the condenser module 7 is connected to the loop heat pipe evaporation section structure, including the condenser pipe 5, and the pipe support for supporting the condenser pipe 5.

[0046] The mounting interface between the pipe support of condenser pipe 5 and the heat dissipation panel of the spacecraft satellite is set as an integrally molded aluminum alloy part. Its contact surface is pre-attached with a phase change thermal conductive pad with adhesive backing, which can be directly glued and fixed, eliminating the need for screw connection.

[0047] For flexible pipe fixing angles, polyimide elastic clamps are used in conjunction with silicone rubber damping pads to bind and fix the pipes in long spans and at bends.

[0048] For the key brazing connection angle, the connection between the liquid reservoir 6 and the condenser pipeline adopts a vacuum brazing with a preset gap of 0.15-0.25mm, preferably 0.2mm, and Al-Si brazing filler metal is used for welding.

[0049] The vibration-resistant structural module can suppress the performance degradation of the loop heat pipe system under vibration and centrifugal environment. Through the combination of integrated pipe support, elastic clamps and damping pads, and gap vacuum brazing, it can effectively suppress vibration transmission and avoid the risk of screw loosening.

[0050] Gap vacuum brazing ensures the reliability of dissimilar material connections under thermal cycling.

[0051] Screwless interfaces reduce assembly steps and improve overall assembly efficiency and consistency.

[0052] The capillary wick 1 is also equipped with an eccentrically arranged auxiliary flow channel. The arrangement direction of the auxiliary flow channel is related to the expected rotation direction of the system, which is used to guide the liquid working fluid to gather towards the evaporation end in a centrifugal environment.

[0053] Specifically, the auxiliary flow channel is positioned outward from the expected rotation direction of the system; for example, when rotating clockwise, the auxiliary flow channel is located on the right side. This auxiliary flow channel has a small cross-section and is connected in parallel with the main channel of the composite channel system 2.

[0054] The loop heat pipe system has a centrifugal acceleration compensation coefficient of 0.3-0.5g under high-speed centrifugal conditions, which can counteract the centrifugal effect.

[0055] When the system rotates at high speed, centrifugal force causes the working fluid to accumulate outwards. The eccentrically arranged auxiliary flow channel takes advantage of this outward accumulation trend to guide some of the liquid to the high heat flux region at the evaporation end, compensating for insufficient liquid supply at the evaporation end caused by centrifugal force and achieving self-balancing of the working fluid distribution.

[0056] In the intelligent temperature control module, the heating element includes a 20W thin-film heater attached to the outer wall of the liquid reservoir 6, and the semiconductor cooling element includes a TES1-241015 TEC attached to the outer wall of the liquid reservoir 6. The hot and cold ends are coupled to the liquid reservoir 6 through a heat pipe.

[0057] The high-precision temperature sensor includes an MF501 thermistor with an accuracy of ±0.1℃, and the PID controller adopts the TCM-M207 model, which incorporates a temperature fluctuation suppression algorithm. By acquiring data from the high-precision temperature sensor in real time, the operation of the semiconductor cooling chip and heating chip is dynamically adjusted.

[0058] The temperature fluctuation suppression algorithm makes predictive adjustments not only based on the current temperature difference, but also based on the temperature change trend.

[0059] Through closed-loop control of sensors, TEC / heater, and PID algorithm, combined with predictive algorithm, the temperature fluctuation of liquid receiver 6 is ≤0.1℃, thereby ensuring extremely stable evaporator temperature.

[0060] The loop heat pipe evaporation section structure and loop heat pipe system in this application fundamentally improve the heat transfer adaptability and interface stability of the evaporation section through the thermal coupling structure of the gradient channel of the capillary wick 1, the thermal expansion compensation interface layer, and the prefabricated thermal interface material layer 41.

[0061] Based on the optimized evaporation section, a complete loop heat pipe system was constructed. By introducing an intelligent temperature control module and an anti-vibration structure module, the reliability and temperature control accuracy of the system under high dynamic (vibration, centrifugal) environments were solved.

[0062] The gradient channels of capillary wick 1 provide adaptive heat transfer capability under varying operating conditions, while vibration resistance and temperature control ensure stable performance of adaptive heat transfer capability even in harsh environments, achieving a balance between heat transfer performance and dynamic adaptability.

[0063] The thermal expansion interface layer inside the evaporation section ensures long-term stable contact of the core interface, while the external vibration-resistant structure protects the entire system from damage by the external mechanical environment, achieving a balance between interface stability and system reliability.

[0064] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0065] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A loop heat pipe evaporator section structure, characterized in that, include: The capillary wick has a composite channel system on its outer surface for the flow of working fluid. The composite channel system includes multiple axially extending straight channels and at least one spiral channel. The cross-sectional shape of the spiral channel changes in a gradient along the axial direction of the capillary wick, so that the capillary wick generates a non-uniform capillary suction force distribution along its axial direction, which is used to adaptively match the heat flux density distribution along the axial direction of the evaporation section. A metal housing is fitted onto the outside of the capillary core, and the capillary core and the metal housing are interference-fitted. An interface layer is disposed between the capillary core and the metal shell. The interface layer is made of a flexible material with a thermal expansion coefficient between that of the capillary core material and the metal shell material. It is used to dynamically compensate for the expansion difference between the two when the temperature changes, and maintain close contact at the interface. A saddle, fitted onto the outside of the metal housing, and a prefabricated thermal interface material layer disposed between the saddle and the metal housing.

2. The loop heat pipe evaporator section structure according to claim 1, characterized in that, The cross-section of the spiral groove is trapezoidal or rectangular; The ratio of the groove depth to the groove width of the spiral groove, and / or the pitch of the spiral groove, varies monotonically from the expected high heat flux density end of the capillary wick to the low heat flux density end.

3. The loop heat pipe evaporator section structure according to claim 1, characterized in that, The interface layer includes a flexible graphite composite material layer; The thickness of the interface layer is 0.01 mm to 0.1 mm, and the thermal expansion coefficient of the interface layer within the operating temperature range satisfies: thermal expansion coefficient of the capillary wick < thermal expansion coefficient of the interface layer ≤ thermal expansion coefficient of the metal shell.

4. The loop heat pipe evaporator section structure according to claim 1, characterized in that, The prefabricated thermal interface material layer includes a thermally conductive pad containing phase change microcapsules.

5. The loop heat pipe evaporator section structure according to claim 1, characterized in that, The metal shell has an external annular groove on the outside of the area where it is welded to the end cap for accommodating the flow of cooling medium. The central channel inside the capillary core has a flared inlet at its entrance, with a cone angle of 15° to 60°.

6. The loop heat pipe evaporator section structure according to claim 1, characterized in that, In the composite channel system, the depth of the straight channel is greater than the depth of the spiral channel; The straight groove has a square cross-section with a side length of 0.8 mm to 1.2 mm; the spiral groove has a groove depth of 0.4 mm to 0.6 mm.

7. A loop heat pipe system, characterized in that, The system includes the loop heat pipe evaporator section structure as described in any one of claims 1-6, as well as a condenser module, an intelligent temperature control module, and a vibration-resistant structure module; The condenser module is connected to the loop heat pipe evaporation section structure and includes a condenser pipe, which is supported by a pipe support. The intelligent temperature control module includes a semiconductor cooling chip, a heating element, a high-precision temperature sensor, and a PID controller, all installed in the liquid reservoir. The pipe support and the spacecraft satellite heat dissipation panel mounting interface are integrally formed; An elastic clamp and a silicone rubber damping pad are provided between the pipe support and the condenser pipe. Vacuum brazing is used to connect the liquid reservoir and the condenser pipeline for connecting dissimilar materials.

8. The loop heat pipe system according to claim 7, characterized in that, A thermally conductive phase change pad with adhesive backing is pre-placed between the pipe support and the condensation pipe. The gap for gap vacuum brazing is 0.15-0.25mm, and Al-Si brazing filler metal is used.

9. The loop heat pipe system according to claim 7, characterized in that, The capillary core is also provided with an eccentrically arranged auxiliary flow channel. The arrangement direction of the auxiliary flow channel is related to the expected rotation direction of the system, and is used to guide the liquid working fluid to gather towards the evaporation end in a centrifugal environment. The centrifugal acceleration compensation coefficient of the loop heat pipe system under high-speed centrifugal environment is 0.3-0.5g.

10. The loop heat pipe system according to claim 7, characterized in that, The PID controller in the intelligent temperature control module includes a temperature fluctuation suppression algorithm, which dynamically adjusts the operation of the semiconductor refrigeration chip and the heating chip by collecting data from the high-precision temperature sensor in real time.

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