A thermal switch heat pipe and a preparation method thereof

Abstract

The present application relates to a kind of hot switch heat pipe and its preparation method, and the hot switch heat pipe includes vacuum sealed pipe shell;Tubular wick is provided in the pipe shell, and the inner wall of pipe shell is connected to the outer wall of wick;The lumen of wick is provided with condensing section and evaporating section filled with liquid working medium;One-way conducting device is provided between condensing section and evaporating section;Condensing section, wick and evaporating section are sequentially connected to form liquid working medium passage;Evaporating section, one-way conducting device and condensing section are sequentially connected to form gaseous working medium passage;One-way conducting device is used to cut off gaseous working medium passage in low-power state of evaporating section, and open gaseous working medium passage in high-power state of evaporating section.The hot switch heat pipe has the characteristics of variable thermal resistance of heat conduction and one-way of heat conduction, can meet the use requirement of low thermal conductivity under low power and high thermal conductivity under high power, is suitable for industrial production, and has novel application value in certain specific application occasions such as semiconductor and electronic equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat pipe, in particular to a heat switch heat pipe and a preparation method thereof. BACKGROUND

[0002] The development trend of electronics is mainly high integration, high performance and miniaturization. According to Moore's law, the number of components that can be accommodated on an integrated circuit will double about every 18-24 months, and the performance will also double. In recent years, the development of Moore's law has gradually reached a bottleneck period, and one of the important problems is the heat dissipation limitation.

[0003] Phase change heat transfer technology uses the principle of vapor-liquid phase change. Under heat input, the working medium vaporizes quickly to take away heat, avoiding the failure of the chip due to high temperature. Heat pipe, as a typical phase change heat transfer element, is gradually favored by electronic devices due to its high thermal conductivity, fast response, high reliability and other advantages, and is increasingly widely used. In addition to being commonly used in computer cooling systems, in recent years, heat pipes have begun to shine in high-performance mobile phones. Some internal heat pipes, solidifiable heat-conducting gels, high-thermal-conductivity aluminum alloy frames and multi-layer composite graphite heat sinks are used to form a complete mobile phone heat dissipation system. Some use double heat pipe liquid cooling to dissipate heat. The key components of both are high-thermal-conductivity heat pipes, which effectively improve the heating problem of mobile phones under high power for a long time.

[0004] However, in some new application scenarios, in addition to the high thermal conductivity of the heat pipe, it also needs to meet the variable thermal resistance characteristics of heat conduction. Typical use scenarios are that low power requires low thermal conductivity to meet the use scenario, and high power requires high thermal conductivity to meet the use requirements. Traditional heat pipes cannot meet this new requirement and cannot fully exert their excellent heat dissipation effect. Therefore, how to design a new heat pipe with heat switch properties is a new technical challenge faced by the industry. SUMMARY

[0005] In view of the technical problems existing in the prior art, one of the purposes of the present application is to provide a heat switch heat pipe with variable thermal resistance characteristics of heat conduction and unidirectional heat conduction, which can meet the use requirements of low thermal conductivity at low power and high thermal conductivity at high power.

[0006] In view of the technical problems existing in the prior art, the second purpose of the present application is to provide a preparation method of a heat switch heat pipe.

[0007] In order to achieve the above purposes, the present application adopts the following technical solutions:

[0008] A heat switch heat pipe, comprising a vacuum-sealed pipe shell;

[0009] The tubular wick is arranged in the tube shell, and the inner wall of the tube shell is connected to the outer wall of the wick;

[0010] The condensing section and the evaporation section are arranged in the lumen of the wick.

[0011] The one-way conducting device is arranged between the condensing section and the evaporation section.

[0012] The condensing section, the wick and the evaporation section are sequentially connected to form a liquid working medium passage.

[0013] The evaporation section, the one-way conducting device and the condensing section are sequentially connected to form a gaseous working medium passage.

[0014] The one-way conducting device is used to block the gaseous working medium passage in the low-power state of the evaporation section and to conduct the gaseous working medium passage in the high-power state of the evaporation section.

[0015] Further, the diameter of the evaporation section is smaller than the diameter of the condensing section. The smaller diameter of the evaporation section meets the design of the reverse limiting structure, and the gaseous working medium is more likely to form a larger steam pressure in the evaporation section to start the one-way conducting device, thereby making the heat switch heat pipe more sensitive.

[0016] Further, the condensing section includes one or more condensing subsections, and the one-way conducting device is arranged between adjacent two condensing subsections. The resistance series function is realized by sequentially connecting the multiple condensing subsections, and multiple one-way conducting devices need to be started at the same time in the forward starting, which is suitable for high-power heat source scenes.

[0017] Further, the one-way conducting device includes at least one blocking piece and a spring, and the outer diameter of the blocking piece is greater than the diameter of the evaporation section and smaller than the diameter of the condensing section.

[0018] Further, the blocking piece is at least two, and the at least two blocking pieces are tightly connected to form a blocking piece group, one end of the blocking piece group abuts against the evaporation section, and the other end is connected to the spring.

[0019] Further, the blocking piece is a spherical ball, a cylinder or a circular truncated cone, and the material includes gold, silver, steel, iron, copper, lead, aluminum and other metals.

[0020] Further, the liquid working medium is water, acetone, ethanol or ammonia, and the volume of the liquid working medium accounts for 10-40% of the inner cavity of the tube shell.

[0021] Further, the vacuum degree in the tube shell is ≤10 Pa.

[0022] A preparation method of a heat switch heat pipe includes the following steps,

[0023] The tubular wick is arranged in the tube shell, and the inner wall of the tube shell is connected to the outer wall of the wick;

[0024] The one-way conducting device is arranged between the condensing section and the evaporating section in the lumen of the wick, and if there are multiple condensing sections, the steps of reducing the diameter and arranging the conducting device are repeated. The condensing section, the wick and the evaporating section are sequentially connected to form a liquid working medium passage, and the evaporating section, the one-way conducting device and the condensing section are sequentially connected to form a gaseous working medium passage. The step-shaped tube diameter distribution formed can meet the requirements of the reverse limiting structure and is beneficial to improving the one-way heat transfer of the heat pipe. The liquid working medium is filled into the evaporating section, and the tube shell is vacuumized and sealed.

[0025] Further, the implementation of placing the tubular wick in the tube shell includes the following steps,

[0026] The graphite rod is placed in the tube shell, and metal powder is filled between the tube shell and the graphite rod. The tube shell filled with powder is sintered together with the graphite rod, so that the metal powder forms a wick. After sintering, the graphite rod is extracted, so that a tubular wick is obtained in the tube shell.

[0027] The tubular wick is tightly sintered from metal powder and has capillary wicking performance. The metal powder is of the same material as the tube shell and has a mesh size of 100-1000 mesh. Using the sintering method can generate a tightly connected tubular wick on the inner wall of the tube shell, avoiding the problem of looseness and poor heat transfer caused by the direct insertion of the ready-made wick into the tube shell. At the same time, the same material of the metal powder and the tube shell can avoid cracking, gaps and other defects caused by different expansion coefficients.

[0028] Overall, the present application has the following advantages:

[0029] When the power of the evaporating section is low, the pressure of the gaseous working medium formed by the evaporation of the liquid working medium is low, which is not enough to start the one-way conducting device, and the heat switch heat pipe cannot be started smoothly, and the overall heat pipe presents low thermal conductivity characteristics. When the power of the evaporating section rises to a certain extent, the pressure of the gaseous working medium formed by the evaporation of the liquid working medium is high, which can start the one-way conducting device. The gaseous working medium reaches the condensing section through the one-way conducting device, and is condensed into liquid working medium in the condensing section. Then the liquid working medium is absorbed by the wick and flows back to the evaporating section, thereby forming a vapor-liquid cycle, and the heat pipe is started smoothly. The continuous vapor-liquid cycle can quickly take away the heat of the heat source, and the overall heat pipe presents high thermal conductivity characteristics. Therefore, the heat switch heat pipe of the present application has variable thermal resistance characteristics of heat conduction, which can meet the use requirements of low thermal conductivity at low power and high thermal conductivity at high power.

[0030] When heated in reverse, steam cannot pass through the unidirectional conduction device, the vapor-liquid circulation necessary for the thermal switch heat pipe to start cannot be formed, and the condensation section cannot start smoothly. Therefore, this thermal switch heat pipe also exhibits unidirectional heat conduction. The preparation method is compatible with traditional heat pipe processes, suitable for industrial production, and has novel application value in certain specific applications such as semiconductors and electronic devices. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of one possible structure of the solid circular plug in this invention;

[0032] Figure 2 This is a schematic diagram of the tube shell end cap in Example 1;

[0033] Figure 3 This is a schematic diagram of the liquid-absorbing core sintering preparation process in Example 1;

[0034] Figure 4 This is a schematic diagram of the shrinking head of the heating section in Example 1;

[0035] Figure 5 This is a schematic diagram of the unidirectional conduction device arrangement in Example 1;

[0036] Figure 6 This is a schematic diagram of the liquid filling and vacuum sealing process in Example 1;

[0037] Figure 7 This is a schematic diagram of the thermal switch heat pipe in Example 1;

[0038] Figure 8 This is a schematic diagram of the thermal switch heat pipe in Example 2;

[0039] Figure 9 This is a schematic diagram of the thermal switch heat pipe in Example 3.

[0040] The components are: 1. tube shell, 2. liquid suction core, 3. unidirectional conduction device, 31. solid round plug, 32. spring, 4. liquid working fluid, and 5. graphite core rod. Detailed Implementation

[0041] The present invention will now be described in further detail.

[0042] Example 1

[0043] like Figure 7 As shown, a heat pipe with thermal switching includes a pipe housing 1, a liquid wick 2, a one-way conduction device 3, and a liquid working fluid 4. The pipe housing 1 is sealed and evacuated to create a vacuum. The one-way conduction device 3 is composed of a solid circular plug 31 (blocking element) and a spring 32. The liquid wick 2, the liquid working fluid 4, and the one-way conduction device 3 are all located inside the pipe housing 1.

[0044] In a preferred embodiment, the heat switch heat pipe is composed of two sections of pipe diameter, wherein the first section (the reduced head section) has a smaller pipe diameter and is configured as the evaporation section; the second section has a larger pipe diameter and is configured as the condensation section. The one-way valve device 3 is located in the second section. The diameter of the one-way valve device 3 is greater than the pipe diameter of the first section and smaller than the inner diameter of the second section. The one-way valve device 3 is configured to allow flow from the evaporation section to the condensation section and to block flow in the opposite direction.

[0045] In this preferred embodiment, the one-way valve device 3 is formed by a solid round plug 31 and a spring 32, with the solid round plug 31 being attached to the side of the first section with the smaller pipe diameter. The solid round plug 31 is preferably a steel ball. The outer diameter of the spring 32 of the one-way valve device 3 is smaller than the inner diameter of the second section, and the wire diameter of the spring 32 is 1 mm. The pipe shell 1 is a hollow pipe without structure, with a diameter of 6 mm and a wall thickness of 0.5 mm, and is made of copper. The wick 2 is attached to the inner wall of the pipe shell 1 and is sintered from copper powder particles with a mesh number of 100, and has capillary wicking properties. The liquid working medium 4 is preferably deionized water.

[0046] A method for preparing a heat switch heat pipe, specifically comprising the following steps:

[0047] S1. Welding the head of the hollow pipe. A copper pipe without structure with a diameter of 6 mm, a wall thickness of 0.5 mm, and a length of 18 cm is selected as the pipe shell 1, and is first subjected to ultrasonic cleaning and drying treatment. Then, the end of the pipe shell 1 is sealed by tungsten electrode argon arc welding, as shown in Figure 2 The welding process is protected by high-purity argon gas with a purity of 99.99%.

[0048] S2. Sintering the wick 2. The sintered graphite core rod 5 is inserted into the pipe shell 1 after the head reduction, and the powder filling treatment is performed. The metal powder is selected to be copper powder particles with a mesh number of 100. The powder-filled pipe is sintered together with the sintered graphite core rod 5 to form the wick 2 by using a reducing atmosphere sintering method, as shown in Figure 3 The atmosphere used is argon-hydrogen mixed gas with a hydrogen content of 5%. The sintering temperature is 900 degrees for 1 hour. After sintering, the graphite core rod 5 is removed, and the wick 2 is obtained.

[0049] S3. Head reduction. The side of the pipe shell 1 with the sintered wick 2 is subjected to spinning head reduction treatment, as shown in Figure 4 The spinning head reduction diameter is 1 / 2 of the original pipe shell outer diameter, and the spinning head reduction length is 60 mm.

[0050] S4. Arranging the one-way valve device 3. Under the action of gravity, first put in a steel ball solid round plug 31 with a diameter of 5 mm, and then put in a spring 32 with an outer diameter of 5 mm and a wire diameter of 1 mm, as shown in Figure 5 The steel ball and the spring 32 together form the one-way valve device 3.

[0051] S5. Filling and Vacuuming. Deionized water is selected as the liquid working medium 4, with a filling rate of 30%. The tube shell 1 is evacuated to a vacuum degree of 8 Pa using a vacuum-first, filling method.

[0052] S6. End Sealing. Finally, perform a knife seal at the other end of the pipe housing 1, such as... Figure 6 As shown. During the sealing process, the vacuum pump remained operational to ensure a high vacuum inside the tube housing 1. Finally, a helium detector was used to inspect the finished product, confirming complete sealing and thus concluding the preparation process.

[0053] After the above steps S1-S6, a thermal switch heat pipe is obtained, such as... Figure 7 As shown.

[0054] In this thermally switched heat pipe, when the constricted end is the heating end, under low power conditions, the pressure of the gaseous working fluid formed by the evaporation of the liquid working fluid 4 is low, insufficient to activate the one-way conduction device 3, and the thermally switched heat pipe cannot start smoothly. However, when the power of the heating end rises to a certain level, the pressure of the gaseous working fluid formed by the evaporation of the liquid working fluid 4 is high, which can activate the one-way conduction device 3. The gaseous working fluid passes through the one-way conduction device 3 and reaches the condensation section, where it condenses into liquid working fluid 4. Then, liquid working fluid 4 is absorbed by the wick 2 and flows back to the evaporation section, thus forming a vapor-liquid cycle, and the heat pipe can start smoothly. Therefore, the thermally switched heat pipe proposed in this embodiment achieves a functional heat pipe with low thermal conductivity at low power and high thermal conductivity at high power.

[0055] When the section without the constriction tube is the heating end, the unidirectional conduction device 3 prevents steam from passing through due to the limitation of the inner diameter at the constriction tube, thus blocking the vapor-liquid circulation necessary for the heat pipe to start. As a result, the condensation section cannot start smoothly. Therefore, this heat switch heat pipe also has unidirectional heat conduction.

[0056] Example 2

[0057] The difference from Example 1 is that:

[0058] In step S4, such as Figure 1 As shown, a solid iron cylinder 31 is used as the plug. The iron cylinder has a diameter of 5mm and a length of 5mm. Together with the spring 32, it forms a unidirectional conduction device 3. The three iron cylinders are arranged closely in sequence. Pushing the three iron cylinders requires a larger steam pressure, which is suitable for high-power heat source scenarios.

[0059] After the above steps S1-S6, a thermal switch heat pipe as described in this invention is obtained, such as... Figure 8 As shown.

[0060] Example 3

[0061] The difference from Example 1 is that:

[0062] In step S1, a groove copper tube with diameter of 12 mm, wall thickness of 1 mm and length of 24 cm is selected as the tube shell 1.

[0063] In steps S3 and S4, the tube shell 1 is processed by two times of necking and arranging the one-way conducting device 3, i.e. two times of steps S3 and S4. In the first time of necking, the spinning necking diameter is 3 / 4 of the original tube shell outer diameter, and the spinning necking length is 16 cm. In the first time of arranging the one-way conducting device 3, under the action of gravity, a steel ball solid round plug 31 with diameter of 4 mm is first put in, and then a spring 32 with outer diameter of 4 mm and wire diameter of 1 mm is put in. In the second time of necking, the spinning necking diameter is 1 / 2 of the original tube shell outer diameter, and the spinning necking length is 8 cm. In the second time of arranging the one-way conducting device 3, a copper cylindrical solid round plug 31 with diameter of 7 mm is put in, and then a spring 32 with outer diameter of 7 mm and wire diameter of 1.5 mm is put in.

[0064] After the above steps S1-S6, a heat switch heat pipe according to the present application is obtained, as shown in Figure 9 The heat switch heat pipe of this embodiment has the feature of two-stage one-way conducting device 3, realizes the effect of resistance series connection, and is suitable for high-power heat source scenes.

[0065] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the present application shall be equivalent replacement methods, and all shall be included in the protection scope of the present application.

Claims

1. A thermal switch heat pipe, characterized by: The tube shell comprises a vacuum seal; The tube shell is provided with a tubular wick, and the inner wall of the tube shell is connected to the outer wall of the wick; The lumen of the wick is provided with a condensation section and an evaporation section filled with liquid working medium, and the evaporation section and the condensation section form a stepped tube diameter distribution; The condensation section, the wick and the evaporation section are sequentially connected to form a liquid working medium passage; The evaporation section, the one-way conducting device and the condensation section are sequentially connected to form a gaseous working medium passage; The one-way conducting device is used to block the gaseous working medium passage in the low-power state of the evaporation section and to open the gaseous working medium passage in the high-power state of the evaporation section; The one-way conducting device comprises a blocking piece and a spring, the outer diameter of the blocking piece is greater than the tube diameter of the evaporation section and smaller than the tube diameter of the condensation section, one end of the blocking piece abuts against the evaporation section, the other end of the blocking piece is connected to one end of the spring, and the other end of the spring abuts against the condensation section; The condensation section comprises at least two condensation subsections, the one-way conducting device is arranged between the two adjacent condensation subsections, and a stepped tube diameter distribution is formed between the two adjacent condensation subsections; The vacuum degree in the tube shell is less than or equal to 10 Pa.

2. A thermal switch heat pipe according to claim 1, wherein: The blocking piece is at least two, and the at least two blocking pieces are tightly connected to form a blocking piece group, one end of the blocking piece group abuts against the evaporation section, and the other end is connected to the spring.

3. A thermal switch heat pipe according to claim 1, wherein: The blocking piece is a sphere, a cylinder or a circular truncated cone, and the material comprises gold, silver, steel, iron, copper, lead or aluminum.

4. A thermal switch heat pipe according to claim 1, wherein: The liquid working medium is water, acetone, ethanol or ammonia, and the volume of the liquid working medium accounts for 10-40% of the inner cavity of the tube shell.

5. A method of making a thermal switch heat pipe according to any one of claims 1 to 4, characterized in that: The method comprises the following steps, The graphite rod is placed in the tube shell, and the metal powder is filled between the tube shell and the graphite rod; the tube shell filled with the metal powder is sintered together with the graphite rod, so that the metal powder forms the wick; after sintering, the graphite rod is extracted, and a tubular wick is obtained in the tube shell, and the inner wall of the tube shell is connected to the outer wall of the wick; The tube diameter of the evaporation section of the tube shell is reduced by external machining, so that the evaporation section and the condensation section form a stepped tube diameter distribution; the one-way conducting device is arranged between the condensation section and the evaporation section in the lumen of the wick, so that the condensation section, the wick and the evaporation section are sequentially connected to form a liquid working medium passage, and the evaporation section, the one-way conducting device and the condensation section are sequentially connected to form a gaseous working medium passage; The liquid working medium is injected into the evaporation section; The tube shell is vacuumized and sealed.

6. A method of making a heat switch heat pipe according to claim 5, wherein: The tubular wick is tightly sintered from metal powder, has a capillary wicking performance, and the metal powder is made of the same material as the tube shell and has a mesh number of 100-1000.

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