Temperature self-adaptive heat pipe wick, heat pipe and battery pack heat management system

Abstract

The invention discloses a temperature self-adaptive heat pipe wick, a heat pipe and a battery pack heat management system. The temperature self-adaptive heat pipe wick comprises a plurality of micro bulges for forming groove micro channels; each micro protrusion comprises a body, the first end of the body is used for being connected with a heat pipe, the two sides of the body are each provided with a deformation layer, the two deformation layers are oppositely arranged, the ends, away from the first end of the body, of the deformation layers incline outwards, and therefore the two deformation layers form a splayed shape. The deformation layers are made of negative expansion materials, and when the temperatures of the two sides of the micro protrusions are different, the deformation amounts of the deformation layers on the two sides are different. The heat pipe adopts the temperature self-adaptive heat pipe wick, the battery pack heat management system adopts the heat pipe, when the temperatures on the two sides of the micro-bulge are different, the inclination angles of the deformation layer are different, so that the concave angles of channels on the two sides of the micro-bulge are different, and the concave angle close to the high-temperature side is smaller than the concave angle far away from the high-temperature side, so that directional backflow of a liquid working medium to the high-temperature side is realized; belongs to the technical field of thermal management.

Description

Technical Field

[0001] This invention relates to the field of thermal management technology, specifically to a temperature-adaptive heat pipe wick, heat pipe, and battery pack thermal management system. Background Technology

[0002] As the power density of new energy storage power stations increases to over 300W / kg, the risk of thermal runaway grows exponentially. Heat pipe technology, with its exceptional thermal conductivity, has become a key technology for battery thermal management. However, the response hysteresis problem of existing heat pipe systems under dynamic operating conditions severely restricts their large-scale application.

[0003] Currently, traditional heat pipe dynamic flow guidance mechanisms have inherent technical defects. Mainstream heat pipes rely on gravity assistance, and their flow guidance direction is limited by the initial design. When the temperature gradient direction of the battery module reverses, the vapor flow direction adjustment delay is relatively long, leading to an increase in the amount of working fluid accumulated in the condensation section, which poses a significant risk of control failure.

[0004] In addition, wicks generally suffer from the problem of being unable to balance high permeability and high flow resistance. As the core component of a heat pipe, the wick relies on the microporous structure inside the porous medium to generate capillary force to drive the internal working fluid to circulate. The smaller the capillary radius, the greater the capillary force it can provide, but it will also cause greater flow resistance, which may result in slow reflux and dry working fluid in the evaporation section.

[0005] Current industry research focuses on static performance optimization, while existing cooling solutions require cascaded responses through temperature control systems, necessitating external intervention and incurring additional energy consumption, without addressing adaptive temperature dynamic response. Crassula muscosa's selective liquid transport mechanism enables directional liquid transport to a designated direction, offering a new approach to overcoming inertial forces, providing additional driving force, and unpowered tracking of high-temperature hotspots. However, current thermal diodes are limited to static unidirectional transport, and there is no practical application of this technology, leaving a gap in the industry. Summary of the Invention

[0006] To address the technical problems existing in the prior art, the purpose of this invention is to provide a temperature-adaptive heat pipe wick that can achieve uninterrupted control of the working fluid flow and adaptively track and prioritize cooling of high-temperature hot spots.

[0007] The second objective of this invention is to provide a heat pipe that enables the internal working fluid to adaptively optimize reflux cooling of high-temperature regions.

[0008] A third objective of this invention is to provide a battery pack thermal management system.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a temperature-adaptive heat pipe wick, comprising multiple micro-protrusions for forming grooved microchannels; each micro-protrusion comprises a main body, the first end of which is used to connect to a heat pipe, and both sides of the main body are provided with deformable layers, the two deformable layers are arranged opposite to each other, and the end of the deformable layer away from the first end of the main body is inclined outward, so that the two deformable layers form a figure-eight shape; the deformable layers are made of a negative thermal expansion material, and when the temperatures on both sides of the micro-protrusion are different, the deformation of the two deformable layers is different.

[0010] With this structure, when the temperature is uniform, the two deformable layers are symmetrical. Using a plane perpendicular to the axis of symmetry between the two deformable layers as the reference plane, a concave angle is formed between the deformable layers and the reference plane. When the temperatures on both sides of the micro-protrusion are different, the deformable layers expand asymmetrically, resulting in different tilt angles on both sides of the main body. This causes the concave angles of the channels on both sides of the micro-protrusion to differ, with the concave angle closer to the high-temperature side being smaller than that farther from the high-temperature side, thus achieving directional reflux of the liquid working fluid to the high-temperature side.

[0011] As a preferred embodiment, the first end of the main body is a base, the second end of the main body is provided with a top connecting layer, and the deformable layer is connected between the base and the top connecting layer; the main body also includes a support structure, the first end of the support structure passes through the base and is used to connect the heat pipe, and the second end of the support structure is connected to the middle area of ​​the top connecting layer.

[0012] As a preferred embodiment, the base, top connecting layer, and supporting structure are all made of materials with a thermal expansion coefficient of less than 2×10⁻⁶. -6 It is made of polymeric materials with a thermal conductivity of less than 0.25 W / (m·K) and a K / K ratio.

[0013] As a preferred embodiment, the micro-protrusions are arranged in multiple rows, with multiple micro-protrusions in each row arranged along the working fluid return direction parallel to the heat pipe, and two deformable layers in each micro-protrusion distributed back and forth along the working fluid return direction.

[0014] As a preferred option, it also includes a wire mesh, which is laid on the grooved microchannels.

[0015] As a preferred option, the negative thermal expansion material is zirconium tungstate or an anti-perovskite metal material, with a negative expansion coefficient of -(8~20)×10⁻⁶. -6 / K.

[0016] As a preferred option, the base, top connecting layer, and support structure are manufactured by laser induction, hot pressing, or electrical discharge machining.

[0017] As a preferred option, the micro-protruding surface is hydrophilically treated.

[0018] A heat pipe employing the aforementioned temperature-adaptive heat pipe wick, with micro-protrusions located on the inner wall of the heat pipe shell.

[0019] A battery pack thermal management system employs the aforementioned heat pipe, including a liquid cooling channel for heat dissipation. The heat pipe has multiple evaporation sections and multiple condensation sections, which are alternately arranged. The evaporation sections directly contact and wrap around the battery pack, while the condensation sections are in contact with the liquid cooling channel.

[0020] In summary, the present invention has the following advantages:

[0021] (1) The present invention achieves a selective directional transport structure by using the asymmetric concave angle of the microchannel formed by temperature difference, which can provide additional driving force for the recirculation of the working fluid, so that the existing liquid core structure can maintain high capillary force while overcoming some flow resistance, accelerating the circulation speed of the working fluid, improving heat dissipation efficiency, and greatly reducing the risk of the working fluid drying out in the evaporation section.

[0022] (2) This invention utilizes the thermal expansion material’s characteristic of shrinking when heated, and combines it with the support structure to form a lever amplification effect, constructing asymmetric menisci on both sides of the micro-protrusion, transforming the small volume change of the negative thermal expansion material into an angle change of the concave angle, which has the advantage of temperature self-adaptation to change the direction of liquid transport, without the need for external magnetic field or power supply, thus reducing energy consumption.

[0023] (3) The battery pack thermal management system of the present invention takes the highest temperature point as the center and the micro protrusions arranged at both ends have a smaller indentation angle near the high temperature end, making the evaporation section more flexible and realizing bidirectional circulation. It automatically tracks the highest temperature point for priority cooling, solves the problems of heat dissipation uniformity and local overheating, and improves the battery pack life. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the micro-protrusion structure in Example 1 when the temperature is uniform.

[0025] Figure 2 This is a schematic diagram of the structure of the micro-protrusion in Example 1 when the temperatures on both sides are different.

[0026] Figure 3 This is a schematic diagram of the overall structure of the heat pipe in Example 3.

[0027] Figure 4 This is a schematic diagram of the overall structure of the battery pack thermal management system in Example 4.

[0028] Figure 5 This is a schematic diagram of the overall structure of the heat pipe used for tracking the highest temperature point in Example 4.

[0029] 1 is a micro-protrusion, 2 is a concave angle, 3 is a deformation layer, 4 is a support structure, 5 is a working fluid, 6 is a top connecting layer, 7 is a base, 8 is the first high temperature point, 9 is a vapor channel, 10 is a condensation section, 11 is a liquid cooling channel, 12 is the second high temperature point, 13 is an evaporation section, 14 is a reference surface, and 15 is a battery module. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] like Figures 1-2 As shown, a temperature-adaptive heat pipe wick includes multiple micro-protrusions for forming grooved microchannels. Each micro-protrusion includes a main body, the first end of which is used to connect to the heat pipe. Both sides of the main body are provided with deformable layers, which are arranged opposite to each other. The end of the deformable layer away from the first end of the main body is inclined outward, so that the two deformable layers form a figure-eight shape. The deformable layers are made of a negative thermal expansion material. When the temperatures on both sides of the micro-protrusion are different, the deformation of the two deformable layers is different.

[0033] In use, multiple micro-protrusions are arranged inside the heat pipe, and adjacent micro-protrusions form microchannels with capillary action, allowing the liquid working fluid to flow within these microchannels through capillary action. For example... Figure 1 As shown, when the temperature is uniform, the two deformed layers are symmetrical to each other. Taking a plane perpendicular to the axis of symmetry between the two deformed layers as the reference plane, the angle between the deformed layer and the reference plane is the concave angle. For example... Figure 2 As shown, when the temperatures on both sides of the micro-protrusion are different, the tilt angle of the deformation layer is different, which makes the concavity angle of the channel on both sides of the micro-protrusion different. The concavity angle closer to the high temperature side is smaller than that farther from the high temperature side. Since the liquid can flow in a direction to the side with the smaller concavity angle, it causes the liquid working fluid to concentrate and flow to the high temperature side.

[0034] In some embodiments, the first end of the main body is a base, the second end of the main body is provided with a top connecting layer, and the deformable layer is connected between the base and the top connecting layer; the main body also includes a support structure, the first end of the support structure passes through the base and is used to connect the heat pipe, and the second end of the support structure is connected to the middle region of the top connecting layer.

[0035] The main body can be an internally hollow structure, and the deformable layer can be embedded in the two sides of the main body to form sidewalls, or form a covering coating on the outer surface of the two sides of the main body.

[0036] Since the base, top connecting layer and support structure do not deform with temperature changes, and the support structure supports and connects to the middle area of ​​the top connecting layer, forming a lever centered on the connection between the two, the impact resistance of the micro-protrusion is improved, and it can prevent tilting or deformation under stress after long-term flow of working fluid.

[0037] When there is a temperature gradient on both sides, the deformable layer expands asymmetrically. The height at the center of the lever remains unchanged. The end with smaller negative expansion is pushed up, causing the concave angle on that side to widen. The end with larger negative expansion is pressed down, causing the concave angle on that side to narrow. At this time, the two deformable layers bend, and the two slightly protruding sides form a crescent-shaped concave area. The concave angle refers to the angle between the plane between the two ends of the deformable layer and the reference plane.

[0038] In some embodiments, the base, top connecting layer, and support structure are all made of materials with a thermal expansion coefficient of less than 2 × 10⁻⁶. -6 It is made of a polymer material with a thermal conductivity of less than 0.25 W / (m·K). This material must not deform due to temperature changes within the range of 20℃ to 70℃, and suitable materials such as silicone, polytetrafluoroethylene, or Mylar sheet can be selected.

[0039] In some embodiments, the microprotrusions are arranged in multiple rows, with multiple microprotrusions in each row arranged parallel to the working fluid reflux direction of the heat pipe, and two deformable layers in each microprotrusion distributed back and forth along the working fluid reflux direction. The spacing between the microprotrusions can refer to existing grooved wicking cores, so that adjacent microprotrusions form grooved microchannels with capillary action.

[0040] In some embodiments, the deformable layer uses an existing material with a large negative thermal expansion coefficient, such as ZrW2O8, which has a thermal expansion coefficient of -9 × 10⁻⁶. -6 / K.

[0041] In some embodiments, the base, top connecting layer, and support structure are manufactured by laser induction, thermoforming, or electrical discharge machining.

[0042] In some embodiments, the micro-protruding surface is hydrophilically treated.

[0043] The aforementioned method for preparing an adaptive wick can be fabricated on a heat pipe using existing processing techniques. Specifically, the method involves the following steps: First, ultrasonic welding is used to weld the polymer material onto the heat pipe shell material; then, common fabrication methods such as laser induction, thermoforming, or electrical discharge machining are used to process a groove-like structure on the polymer material to form a main body with multiple micro-protrusions; finally, a negative thermal expansion material is locally coated using laser-assisted spraying to create a deformable layer.

[0044] Example 2

[0045] In conjunction with Embodiment 1, the micro-protrusions also include a wire mesh, which is laid on the grooved microchannels. Thus, the internal pores of the wire mesh, the spaces between the wire mesh and the micro-protrusions, and the spaces between adjacent micro-protrusions collectively constitute a wire mesh-groove-like composite microchannel. The wire mesh has uniform porosity, thereby providing the necessary capillary backflow force for the working fluid, while the micro-protrusions, in the presence of a temperature gradient, form an asymmetric heterogeneous meniscus, providing a directional flow channel for the working fluid. This wire mesh-groove-like composite wicking structure can simultaneously reduce the flow resistance of the liquid working fluid while providing a large capillary driving force through the wire mesh structure.

[0046] In the manufacturing of the aforementioned composite absorbent core, a common metal mesh is produced using a spiral braiding method, and the mesh is then fixed to the micro-protruding surface using an electrodeposition bonding process or a hot pressing process. Since the smooth surface of the metal mesh can affect capillary force, hydrophilic modification is performed using methods such as electrodeposition or alkali-assisted oxidation. The relevant manufacturing processes can be found in the following literature: Guo Bin. Study on hot pressing and mechanism of microgroove liquid wick structure of ultrathin flexible polymer heat sink [D]. Shenzhen University, 2023. DOI:10.27321 / d.cnki.gszdu.2023.001764; Tang Heng. Research on manufacturing and heat transfer performance of ultrathin heat pipe with wire mesh liquid wick [D]. South China University of Technology, 2018; Tang Yong, Sun Yalong, Tang Heng, et al. Research status and development trend of flexible heat pipe [J]. Journal of Mechanical Engineering, 2022, 58(10):265-279; LIEW LA, LIN CY, LEWIS R, et al. Flexible thermal ground planes fabricated with printed circuit board technology [J]. Journal of Electronic Packaging, 2017, 139:0110031-01100310; LIEW LA, LIN CY, LEWIS R, et al. al.Flexible thermal ground planes fabricated with printed circuitboard technology[J].Journal of Electronic Packaging,2017,139:0110031-01100310..

[0047] Example 3

[0048] like Figure 3 As shown, a heat pipe employs a temperature-adaptive heat pipe wick as described in Embodiment 1 or Embodiment 2, with micro-protrusions located on the inner wall of the heat pipe shell.

[0049] The working fluid inside the heat pipe is deionized water or ethylene glycol solution. The evaporation section and condensation section of the heat pipe are set alternately. The working fluid absorbs heat and evaporates in the evaporation section, while flowing bidirectionally to the two condensation sections. After releasing heat and condensing, it flows back to the middle evaporation section by the capillary force of the wick.

[0050] When in use, when the high temperature point of the heat pipe is on one side, the distance between the micro-protrusion and the high temperature point is different on both sides, resulting in a temperature difference on both sides. Consequently, the difference in the concave angle caused by the different deformation amounts will inevitably exist, thus realizing the directional transport function.

[0051] Example 4

[0052] like Figure 4 As shown, a battery pack thermal management system adopts a heat pipe according to Embodiment 4, including a liquid cooling channel for heat dissipation. The heat pipe is provided with multiple evaporation sections and multiple condensation sections, which are arranged alternately. The evaporation sections directly contact and wrap around the battery pack, and the condensation sections are attached to the liquid cooling channel.

[0053] Liquid cooling channels are located on both sides of the battery pack, and heat pipes surround the battery pack in a square wave shape.

[0054] like Figure 5 As shown, the above-mentioned battery pack thermal management system is used for the thermal management of battery packs in energy storage power stations, and its working mode is as follows:

[0055] After the battery pack of an energy storage power station has been running for a period of time, the batteries in the central area of ​​the battery pack generate more heat due to their higher internal resistance or higher current density. The individual cells in the middle have inconsistent SOC and the actual battery arrangement takes into account the compact structure to reduce the footprint, resulting in poor heat dissipation, local overheating, and the generation of uneven first high temperature points, which increases the temperature difference within the battery pack module. The heat pipe wick has a first high-temperature point as its axis. In the direction extending towards both ends of the heat pipe, the temperature-sensitive material at the end of the micro-protrusion closer to the first high-temperature point deforms more due to negative thermal expansion, while the end farther from the first high-temperature point deforms less. Under the action of the intermediate support material, the concave angle at the end closer to the first high-temperature point is smaller than that at the end farther from the first high-temperature point. This causes the liquid working fluid to preferentially flow back to the first high-temperature point, absorb heat and evaporate into steam. The steam then flows bidirectionally through the steam channel to the two condensation sections on both sides, where it exchanges heat with the heat exchange fluid in the liquid cooling channel. The working fluid condenses into liquid and flows back to the first high-temperature point again through the wick structure, achieving preferential cooling and reducing the possibility of the working fluid drying out in the evaporation section. This continues until the temperature difference in the area decreases and the difference in the concave angles on both sides of the micro-protrusion becomes smaller, restoring normal working fluid transport.

[0056] After the energy storage power station's battery pack has been operating for a period of time, due to the actual conditions such as the battery pack arrangement, a second high temperature point appears, increasing the temperature difference within the battery pack modules. The heat pipe wick, with the second high temperature point as its axis, exhibits greater negative thermal expansion deformation at the end of the micro-protrusion closer to the second high temperature point, and less deformation at the end farther from the second high temperature point. Under the action of the intermediate support material, the concave angle at the end closer to the second high temperature point is smaller than that at the end farther from the second high temperature point. This promotes the preferential return of the liquid working fluid to the second high temperature point, where it absorbs heat and evaporates into vapor. The vapor flows bidirectionally through the vapor channel to the condensation sections on both sides, exchanging heat with the heat exchange fluid in the liquid cooling channel. The working fluid condenses into liquid and then flows back to the second high temperature point through the wick structure, achieving preferential cooling and reducing the possibility of the working fluid drying out in the evaporation section. This continues until the temperature difference in the affected area decreases to less than 1°C, the difference in the concave angles on both sides of the micro-protrusion becomes smaller, and normal working fluid transport is restored.

[0057] The structure of this invention not only utilizes a liquid-directed transport structure to prioritize the flow of the working fluid to the highest temperature area for cooling, reducing the possibility of liquid drying in the evaporation section, but also uses thermal expansion materials to adaptively change the temperature and control the flow direction of the working fluid without external force, thereby reducing energy consumption, achieving more efficient heat dissipation, avoiding local overheating, and improving heat dissipation uniformity.

[0058] The above embodiments are preferred embodiments of the invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A temperature-adaptive heat pipe wick, characterized by: The micro-protrusions comprise a plurality of micro-protrusions for forming the trench micro-channel; The micro-protrusion comprises a main body, a first end of the main body is used for connecting a heat pipe, both sides of the main body are provided with deformation layers, the two deformation layers are oppositely arranged, and an end of the deformation layer away from the first end of the main body is inclined outward, so that the two deformation layers form an eight-shaped structure; The deformation layer is made of a negative thermal expansion material, and when the temperatures of the two sides of the micro-protrusion are different, the deformation amounts of the two deformation layers are different.

2. A temperature-adaptive heat pipe wick according to claim 1, characterized in that: The first end of the main body is a base, the second end of the main body is provided with a top connecting layer, and the deformation layer is connected between the base and the top connecting layer; the main body further comprises a support structure, a first end of the support structure penetrates through the base and is used for connecting the heat pipe, and a second end of the support structure is connected with a middle region of the top connecting layer.

3. A temperature-adaptive heat pipe wick according to claim 2, wherein: The base, the top connecting layer and the support structure are all made of a high polymer material with a thermal expansion coefficient less than 2x10 -6 / K and a thermal conductivity less than 0.25 W / (m.K).

4. A temperature-adaptive heat pipe wick according to claim 1, wherein: The micro-protrusions are arranged in multiple rows, and the multiple micro-protrusions in each row are arranged along a working medium backflow direction parallel to the heat pipe; the two deformation layers in each micro-protrusion are distributed in front of and behind the working medium backflow direction.

5. A temperature-adaptive heat pipe wick according to claim 1, wherein: The micro-protrusion further comprises a wire mesh, and the wire mesh is laid on the trench micro-channel.

6. A temperature-adaptive heat pipe wick according to claim 1, wherein: The negative thermal expansion material is zirconium tungstate or an inverse perovskite metal material, which has a negative thermal expansion coefficient of - (8-20) x 10 -6 / K.

7. A temperature-adaptive heat pipe wick according to claim 3, wherein: The base, the top connecting layer and the support structure are made by means of laser induction, hot pressing or electric spark machining.

8. A temperature-adaptive heat pipe wick according to claim 1, wherein: The surface of the micro-protrusion is subjected to hydrophilic treatment.

9. A heat pipe characterized by: The temperature self-adaptive heat pipe wick is used for the heat pipe, and the micro-protrusion is located on the inner wall of the heat pipe shell.

10. A battery pack thermal management system employing the heat pipe of claim 9, characterized by: The heat pipe comprises a liquid cooling channel for heat dissipation, and the heat pipe is provided with a plurality of evaporation sections and a plurality of condensation sections, the evaporation sections and the condensation sections are alternately arranged, the evaporation sections directly contact and are wound on the battery pack, and the condensation sections are attached to the liquid cooling channel.

Images