A loop thermosiphon device

Abstract

This invention discloses a thermosiphon loop device. The evaporator consists of four parts: a liquid chamber, a vapor chamber, a microgroove structure, and a filter screen. The microgroove structure significantly increases the number of vaporization nuclei, enhancing boiling heat transfer. Above the microgroove structure, a hemispherical filter screen is designed to drastically reduce the amount of liquid carried into the vapor chamber, thereby enhancing gas-liquid separation within the evaporator. This gas-liquid separation allows the working fluid to have a higher dryness near the evaporation section outlet, significantly increasing the density difference and pressure driving force between the vapor and liquid phases inside the thermosiphon loop, and improving the heat transfer limit. Furthermore, a heat insulation device is installed in the condensate return pipe at the bottom of the evaporation section to suppress backflow caused by the growth and expansion of boiling bubbles, effectively reducing heat leakage at the bottom of the evaporation section. This invention achieves gas-liquid separation within the evaporator and reduces heat leakage at the bottom, thereby improving the heat transfer performance of the thermosiphon loop and making it suitable for high-power heat dissipation requirements.

Description

Technical Field

[0001] This invention relates to the field of loop thermosiphons, specifically a loop thermosiphon device that can achieve gas-liquid separation within the evaporator and reduce heat leakage from the evaporator to the bottom condensate return pipe. Background Technology

[0002] A heat pipe is a passive, high-efficiency heat transfer device that relies on the phase change of its internal working fluid to transfer heat. It boasts advantages such as simple structure, strong heat transfer capacity, and good temperature uniformity, making it widely and significantly used in heat dissipation and cooling. Gravity heat pipes, also known as two-phase closed-loop thermosiphons, are heat pipes without a wick. Their working principle is as follows: the working fluid in the evaporation section boils upon heating, and the resulting vapor is transferred through an adiabatic section to the condensation section where it is cooled. The condensate then flows back to the evaporator under gravity, completing the cycle. The main difference between gravity heat pipes and traditional heat pipes is that the condensate reflux relies on gravity rather than the capillary action generated by a wick, thus effectively avoiding capillary limits. However, since vapor and condensate are in the same pipe within a gravity heat pipe, the reverse vapor-liquid movement can easily cause vapor carryover, reducing condensate reflux and negatively impacting heat transfer.

[0003] Unlike gravity heat pipes, thermosiphons have a closed-loop structure, where the generated steam and condensate move in the same direction, and the condensate reflux is less affected by the shearing effect of the steam movement. Overall, thermosiphons are less affected by the carrying capacity limit, allowing the evaporator to withstand higher heat loads and providing better heat transfer performance.

[0004] However, traditional thermosiphon loops still generally suffer from several problems: During the upward movement of bubbles / gas plugs formed by the boiling of the working fluid in the evaporator along the steam riser, some liquid inevitably carries it upwards. At higher heating power, the evaporation section may experience premature "drying out" due to insufficient or untimely liquid replenishment, increasing the instability of the two-phase flow. Simultaneously, the liquid carried by the vapor phase weakens the condensation heat transfer effect in the condensation section due to the liquid film partially covering the surface, thus reducing the overall heat transfer performance and heat transfer limit of the thermosiphon loop. In the prior art, Chinese Patent Publication No. CN105561716A discloses a wire mesh gas-liquid separator for the inlet and outlet of a gas compressor, which uses a wire mesh on the inner wall above the main gas-liquid phase inlet to achieve gas-liquid separation. However, in practical applications, the wire mesh structure suffers from low durability and is prone to deformation under long-term scouring by the gas and liquid phases.

[0005] In addition, when the thermosiphon is running, the heat loss at the bottom of the evaporator cannot be ignored due to the large temperature difference between the evaporator and the condensate return pipe. At the same time, the backflow caused by the expansion of boiling bubbles in the evaporation section will also hinder the condensate return, thereby reducing the overall heat transfer performance of the heat pipe.

[0006] In view of the above problems, developing relevant technologies to achieve gas-liquid separation in the evaporation section and reduce / weaken the heat leakage at the bottom of the evaporation section can be regarded as an effective means and important measure to improve the heat transfer performance of the loop thermosiphon. Summary of the Invention

[0007] This invention proposes a loop thermosiphon device, the purpose of which is to reduce liquid phase carryover in the evaporation section of the loop thermosiphon and to mitigate heat leakage at the bottom of the evaporation section.

[0008] This invention is achieved through the following technical solution:

[0009] A loop thermosiphon device includes an evaporator and a condensate return line;

[0010] The evaporator includes a liquid chamber and a steam chamber connected in sequence. The inner wall between the liquid chamber and the steam chamber is designed as a micro-groove structure, and a filter screen is provided between the micro-groove structure and the steam chamber.

[0011] The condensate return pipeline is connected to the liquid chamber, and a heat insulation device is installed on the condensate return pipeline.

[0012] Furthermore, the cross-section of the microgroove structure is trapezoidal, and the grooves are distributed in parallel on the inner wall surface.

[0013] Furthermore, a high-speed liquid-filling spinning method and a multi-toothed core head are used to continuously plastically shape the inner wall of the copper or other metal base tube, forming a trapezoidal groove. The trapezoidal microgrooves divide the tube into several protrusions, which can significantly increase the contact area between the surface and the working fluid and increase the number of vaporization nuclei, thereby achieving a stronger heat transfer effect.

[0014] Furthermore, the evaporator structure integrates the liquid chamber, vapor chamber, microgroove structure, and filter screen into one unit.

[0015] Furthermore, the filter screen adopts a hemispherical design, with the convex surface of the hemispherical filter screen facing the steam chamber.

[0016] Furthermore, the filter screen is manufactured using a selective laser melting process.

[0017] Furthermore, the liquid chamber is equipped with a condensate return pipe, and the steam chamber is equipped with a steam outlet pipe. The condensate return pipe is connected to the heat insulation device through a sealed joint.

[0018] Furthermore, the heat insulation device is made of materials with low thermal conductivity, such as polytetrafluoroethylene.

[0019] Furthermore, a perforated structure is provided axially at the end of the heat insulation device near the liquid cavity.

[0020] Furthermore, the sealing joint consists of two rotatable nuts, two retaining cores, two O-rings, and one central bolt; the two ends of the central bolt are provided with retaining cores and O-rings, and the two ends of the central bolt are threadedly connected to the rotatable nuts.

[0021] Beneficial effects:

[0022] (1) Based on the structural requirements of the evaporation section of the loop thermosiphon and the characteristics of the internal flow heat transfer process, this invention designs the evaporator as an integral unit consisting of a liquid chamber, a vapor chamber, a microgroove structure, and a filter screen. Among them, the microgroove structure has the effect of increasing the number of vaporization nuclei on the inner wall of the evaporator and enhancing nucleation boiling heat transfer. At the same time, the microgroove structure and the filter screen can effectively separate the liquid chamber and the vapor chamber, which can achieve better vapor-liquid separation in the evaporation section while effectively reducing the instability of two-phase flow and significantly increasing the internal driving pressure, thereby improving the overall heat transfer performance of the loop thermosiphon.

[0023] (2) The present invention also provides a heat insulation device made of a low thermal conductivity material in the bottom condensate return pipe of the evaporator by means of a sealed joint, thereby reducing the heat leakage to the bottom condensate return pipe caused by the backflow effect caused by the expansion of boiling bubbles in the evaporator.

[0024] (3) The device of the present invention has a simple structure, low manufacturing cost, is easy to implement, and is convenient and reliable to operate, and is suitable for the heat dissipation requirements of high power devices. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0026] Figure 2 This is an enlarged schematic diagram of the evaporator as a whole;

[0027] Figure 3 This is a front sectional view of the microgroove structure on the inner wall of the evaporator;

[0028] Figure 4 This is a side sectional view of the microgroove structure on the inner wall of the evaporator;

[0029] Figure 5 This is a side cross-sectional view of the hemispherical filter screen inside the evaporator;

[0030] Figure 6 This is a top view of the hemispherical filter screen inside the evaporator;

[0031] Figure 7 This is a schematic diagram of the polytetrafluoroethylene tube insulation device at the bottom of the evaporator;

[0032] Figure 8 This is a schematic diagram of the sealing joint structure.

[0033] In the diagram, 1 is the liquid chamber, 2 is the micro-groove structure, 3 is the filter screen, 4 is the steam chamber, 5 is the steam outlet pipe, 6 is the condensate return pipe, 7 is the sealing joint, 8 is the heat insulation device, 9 is the rotatable nut, 10 is the retaining core, 11 is the O-ring seal, and 12 is the center bolt. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0035] like Figure 1-8 As shown, this invention is a closed-loop thermosiphon device, including an evaporator and a condensate return pipe with a heat insulation device at the bottom of the evaporator. The steam outlet pipe at the upper end of the device can be connected to a steam riser pipe, and is connected to the bottom of the evaporator through the condenser and the condensate return pipe, forming a closed loop. The specific structure is as follows:

[0036] The evaporator mainly consists of four parts: a liquid chamber 1, a micro-groove structure 2, a filter screen 3, and a steam chamber 4. A condensate return pipe 6 is installed at the bottom of the liquid chamber 1, and a steam outlet pipe 5 is installed at the top of the steam chamber 4. The micro-groove structure 2 is located between the liquid chamber 1 and the steam chamber 4, such as... Figure 2 As shown, the micro-groove structure 2 is connected to the upper wall and the base of the spherical filter screen 3 by welding. The upper wall of the steam chamber 4 is connected to the steam outlet pipe 5 by welding. The lower wall of the liquid chamber 1 and the condensate return pipe 6 are also connected by welding.

[0037] like Figure 3 and 4 As shown, the cross-section of the channel structure 2 is trapezoidal, and the channels are arranged in a parallel array on the inner wall surface. A high-speed liquid-filled spinning method and a multi-toothed mandrel are used to continuously plastically shape the inner wall of the copper or other metal-based tube.

[0038] A filter screen 3 is installed on the upper part of the micro-groove structure 2, such as... Figure 5 and 6 As shown, filter screen 3 is hemispherical and convex upwards. The pore structure on filter screen 3 consists of round holes with staggered oblong holes. Filter screen 3 and its annular base are an integral structure. The annular base is attached and fixed to the evaporator wall and connected to the steam chamber 1 by welding.

[0039] The basic working principle of this device is as follows: The working fluid inside the micro-channel structure 2 undergoes a phase change under the heating effect of an external heat source, absorbing heat. The working fluid on the surface of the micro-channel boils, generating a large number of bubbles. These bubbles carry some liquid working fluid upwards through the spherical filter screen 3 for filtration and separation. The spherical filter screen 3 blocks most of the upward-moving liquid working fluid, thus ensuring that the working fluid reaching the steam chamber 4 is in a relatively dry state. The steam accumulated in the steam chamber 4 can be transferred to the condensation section through the steam outlet pipe 5 and then condensed. The condensate, under gravity, then flows back into the liquid chamber 1 of the evaporation section through the condensate return pipe 6, completing the cycle.

[0040] The condensate return line is also equipped with multiple sealing joints 7, heat insulation devices 8, and connecting pipes. The condensate return line 6 is connected to the heat insulation device 8 through the sealing joints 7.

[0041] like Figure 7 As shown, the heat insulation device 8 is made of polytetrafluoroethylene (PTFE), and is formed into the desired shape by machining or demolding of a PTFE cylinder. PTFE has a low thermal conductivity (0.256 W / (m·K)), which can significantly reduce heat loss from the evaporation section to the lower condensate return pipe via heat conduction. Simultaneously, the multiple small holes at the upper end of the PTFE cylindrical tube can also suppress heat loss caused by the backflow of fluid from the evaporation section to the condensate return pipe.

[0042] like Figure 8 As shown, the sealing joint 7 consists of two rotatable nuts 9, two retaining cores 10, two O-rings 11, and one center bolt 12. The rotatable nuts 9, retaining cores 10, and O-rings 11 are sequentially fitted onto the outside of the end of the condensate return pipe 6. The condensate return pipe is then connected to the center bolt 12 by hand-tightening the nuts 9. Next, the perforated end of the PTFE insulation device 8 is sequentially fitted onto the rotatable nuts 9, retaining cores 10, and O-rings 11. Simultaneously, the nuts 9 connect the PTFE tube to the center bolt 12, thus connecting the PTFE insulation device 8 and the condensate return pipe 6 as a single unit. To connect the PTFE insulation device 8 to the middle of the condensate return pipe 6, two sealing joints 7 are required. The connection method for the other end of the PTFE insulation device 8 is as described above. Compared to directly nesting inside the return pipe, directly connecting to the condensate return pipe 6 via the joints significantly reduces the downward heat conduction through the pipe wall.

[0043] In this embodiment, the evaporator structure, which integrates the liquid chamber, vapor chamber, microgroove structure, and filter screen, is connected by welding and the material is metal such as copper or stainless steel.

[0044] In this embodiment, both the steam outlet pipe 5 above the evaporator and the condensate return pipe 6 below the evaporator are circular. To reduce heat loss during transmission, metal materials with low thermal conductivity, such as stainless steel, can be used.

[0045] In this embodiment, the hemispherical filter structure is manufactured using selective laser melting (SLM). Considering the good corrosion resistance, strong impact resistance, and relatively high filtration accuracy of stainless steel, it is the preferred material for the structure. The hemispherical filter effectively prevents the upward movement of the liquid working fluid carried by the steam, thus achieving gas-liquid separation. Its annular base is fixed to the evaporator wall and connected by welding. Compared to conventional flat plate filters, the spherical filter can mitigate the impact of gas-liquid two-phase movement, increase the contact area with the working fluid, and thus improve the gas-liquid separation effect.

[0046] In this embodiment, the PTFE tube insulation device can be manufactured through machining, demolding, etc., and then connected to the condensate return pipe through a sealed joint. Compared with internal nesting, direct connection can significantly reduce the heat conduction downward through the pipe wall. At the same time, considering the condensate return resistance and reducing the direct heat loss caused by the backflow of fluid inside the evaporation section to the return pipe, a small hole structure is provided at the upper end of the PTFE tube.

[0047] The above embodiments are only used to illustrate the design concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made based on the principles and design ideas disclosed in the present invention are within the protection scope of the present invention.

Claims

1. A loop thermosyphon device suitable for high power heat dissipation, characterized in that, Including the evaporator and condensate return line; The evaporator includes a liquid chamber (1) and a steam chamber (4) connected in sequence. The inner wall between the liquid chamber (1) and the steam chamber (4) is designed as a micro-groove structure (2). A filter screen (3) is set between the micro-groove structure (2) and the steam chamber (4) to separate the liquid chamber (1) and the steam chamber (4). The condensate return pipeline is connected to the liquid chamber (1), and a heat insulation device (8) is provided on the condensate return pipeline. The microgroove structure (2) has a trapezoidal cross section and is distributed parallel to the inner wall surface; The filter screen (3) adopts a hemispherical design, with the convex surface of the hemispherical filter screen facing the steam chamber (4) to block the upward-moving liquid working fluid and ensure the dryness of the working fluid in the steam chamber (4); The liquid chamber (1) is provided with a condensate return pipe (6), and the steam chamber (4) is provided with a steam outlet pipe (5). The condensate return pipe (6) is connected to one end of the heat insulation device (8) through a sealing joint (7).

2. A loop thermosyphon device suitable for high power heat dissipation according to claim 1, characterized in that, The high-speed liquid-filling spinning method and multi-tooth core head are used to continuously plastically shape the inner wall of the metal base tube to form a trapezoidal groove. The trapezoidal micro-groove is used to separate several protrusions, which can significantly increase the contact area between the surface and the working fluid and increase the number of vaporization nuclei, thereby achieving the effect of enhanced heat transfer.

3. A loop thermosyphon device suitable for high power heat dissipation according to claim 1, characterized in that, An evaporator structure that integrates a liquid chamber (1), a vapor chamber (4), a microgroove structure (2), and a filter screen (3).

4. A loop thermosyphon device suitable for high power heat dissipation according to claim 1, characterized in that, The filter screen (3) is manufactured using selective laser melting technology.

5. A loop thermosyphon device suitable for high power heat dissipation according to claim 1, characterized in that, The heat insulation device (8) is made of a material with low thermal conductivity.

6. A loop thermosyphon device suitable for high power heat dissipation according to claim 5, characterized in that, A perforated structure is provided axially at the end of the heat insulation device (8) near the liquid cavity (1).

7. A loop thermosiphon device suitable for high-power heat dissipation according to claim 1, characterized in that, The sealing joint (7) consists of two rotatable nuts (9), two retaining cores (10), two O-rings (11), and one central bolt (12). The retaining cores (10) and the O-rings (11) are respectively set at both ends of the central bolt (12), and the two ends of the central bolt (12) are then threadedly connected to the rotatable nuts (9).

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