Dry-out prevention low temperature pulsating heat pipe

Abstract

The present application relates to heat exchange equipment technical field, specifically disclose a kind of anti dry burning low temperature pulsating heat pipe, including liquid injection connector and at least two through the liquid injection connector realize mutual communication sub pulsating heat pipe;The sub pulsating heat pipe is formed by the meandering structure of capillary tube bending, the meandering structure includes several parallel pipe sections, and the adjacent two parallel pipe sections are communicated by a inflection segment;At least two parallel pipe sections in the same sub pulsating heat pipe are communicated by straight pipe connection.The anti dry burning low temperature pulsating heat pipe provided by the present application can effectively improve the heat transfer limit of existing pulsating heat pipe.

Description

Technical Field

[0001] This invention relates to the field of heat exchange equipment technology, and in particular to a low-temperature pulsating heat pipe that prevents dry burning. Background Technology

[0002] Pulsating heat pipes (PHP) are a new type of heat pipe that emerged in the 1990s, first proposed by Japan. To manufacture a pulsating heat pipe, a capillary tube with a small inner diameter (typically 0.5mm to 3mm) is repeatedly bent to form a serpentine structure. Then, a vacuum is created inside the tube, and finally, a fluid working medium is filled into the tube.

[0003] Because the diameter of the pulsating heat pipe is sufficiently small, under the influence of surface tension, the nearly saturated two-phase fluid working medium is randomly and alternately distributed in the form of gas plugs and liquid plugs within the capillary. When one end of the pulsating heat pipe (evaporation section) is heated, the fluid working medium absorbs heat, leading to bubble growth and an increase in vapor pressure. Simultaneously, bubbles condense at the other end of the pulsating heat pipe (condensation section), and the bubbles contract and burst, causing a pressure drop. The growth and bursting of bubbles create a pressure difference between the evaporation and condensation sections, thereby driving the working medium to pulsate or circulate unidirectionally within the pipe, transferring heat through the latent heat of the gas-liquid phase change and the sensible heat of the liquid plug flow.

[0004] Compared with traditional heat pipes, pulsating heat pipes have advantages such as good heat transfer performance, flexibility, adaptability, small size, low cost, and long heat transfer distance. They have great development and application prospects in superconducting magnet cooling, electronic heat dissipation, and energy harvesting.

[0005] The critical temperature of low-temperature superconducting magnets is very low, such as 9.6 K for NbTi and 18.1 K for Nb3Sn. When applying pulsating heat pipes to cool low-temperature superconducting magnets (such as NbTi or Nb3Sn), the only suitable working fluid at present is helium (He).

[0006] It is understood that currently only the University of Wisconsin-Madison in the United States, the French Atomic Energy Commission, and the Institute of Physics and Chemistry of the Chinese Academy of Sciences have developed liquid helium pulsating heat pipes worldwide. Experimental results from these institutions show that although liquid helium pulsating heat pipes have a very high effective thermal conductivity, their heat transfer limit (i.e., the upper limit of the heat transfer load) is too low (the heat transfer limit obtained by the University of Wisconsin-Madison is 0.86 W, the heat transfer limit obtained by the French Atomic Energy Commission is 0.145 W, and the heat transfer limit obtained by the Institute of Physics and Chemistry of the Chinese Academy of Sciences is 1.29 W). The main reason for this is that when the heat transfer load of the liquid helium pulsating heat pipe is too high, the gas-liquid circulation state inside the pipe is easily disrupted, eventually leading to dry burning (i.e., one end of the pipe is entirely gas, and the other end is entirely liquid, and the working fluid inside the pipe no longer pulsates or circulates).

[0007] Therefore, existing pulsating heat pipes need to be improved to address their low heat transfer limit.

[0008] The information disclosed in this background section is included only to enhance the understanding of the context of this disclosure, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0009] One objective of this invention is to provide a low-temperature pulsating heat pipe that prevents dry burning, which can effectively improve the heat transfer limit of existing pulsating heat pipes.

[0010] To achieve the above objectives, the present invention provides a low-temperature pulsating heat pipe with anti-dry burning, comprising a liquid injection connector and at least two sub-pulsating heat pipes that are interconnected through the liquid injection connector;

[0011] The sub-pulsating heat pipe has a serpentine structure, which includes several parallel pipe segments, and adjacent parallel pipe segments are connected by a bend.

[0012] At least two parallel pipe segments within the same sub-pulsating heat pipe are connected by a straight connecting pipe.

[0013] Optionally, the parallel pipe section includes, in sequence, a condensation section, an insulation section, and an evaporation section;

[0014] The condensing section, the insulating section, and the evaporating section of the parallel pipe segment are each connected to another parallel pipe segment through a straight connecting pipe, and at least one of the condensing section, the insulating section, and the evaporating section is connected to another parallel pipe segment.

[0015] Optionally, each of the sub-pulsating heat pipes is stacked vertically, and a set of heat-conducting fixing plates is provided between two adjacent sub-pulsating heat pipes.

[0016] Optionally, the thermally conductive fixing plate assembly includes a first thermally conductive fixing plate located at one end of the sub-pulsating heat pipe and a second thermally conductive fixing plate located at the other end of the sub-pulsating heat pipe.

[0017] Optionally, each of the sub-pulsating heat pipes is laid out side by side in a horizontal direction.

[0018] Optionally, the cross-sectional shape of the sub-pulsating heat pipe is circular, square, or triangular.

[0019] Optionally, it also includes a buffer tank connected to each of the sub-pulsating heat pipes via the injection connector.

[0020] Optionally, the parallel pipe section includes two condensation sections and one evaporation section; or, the parallel pipe section includes two evaporation sections and one condensation section.

[0021] Optionally, the working fluid in the sub-pulsating heat pipe is a cryogenic working fluid.

[0022] The beneficial effect of this invention is that it provides a low-temperature pulsating heat pipe that prevents dry burning:

[0023] Straight-connect pipes can connect different parallel pipe sections. Therefore, when a large heat exchange load causes a certain parallel pipe section to dry-burn, the working fluid in another parallel pipe section connected to that parallel pipe section can quickly enter that parallel pipe section through the straight-connect pipe, and the working fluid in that parallel pipe section can also quickly enter another parallel pipe section through the straight-connect pipe. This quickly breaks the dry-burning state in that parallel pipe section, allowing the gas and liquid in that parallel pipe section to resume circulation and preventing dry-burning of a certain parallel pipe section in the sub-pulsating heat pipe.

[0024] Similarly, when the heat exchange load is extremely high, causing a certain sub-pulsating heat pipe to dry-burn, the working fluid in another sub-pulsating heat pipe connected to that sub-pulsating heat pipe can enter the sub-pulsating heat pipe through the liquid injection connector, and the working fluid in that sub-pulsating heat pipe can also enter the other sub-pulsating heat pipe through the liquid injection connector. This breaks the dry-burning state in the sub-pulsating heat pipe, allowing the gas and liquid in the sub-pulsating heat pipe to resume circulation and preventing the dry-burning of a certain sub-pulsating heat pipe.

[0025] In summary, the anti-dry-burning low-temperature pulsating heat pipe provided by this invention has effectively avoided the dry-burning situation of both the parallel pipe section and the sub-pulsating heat pipe. Therefore, it can effectively suppress the occurrence of dry-burning and ultimately improve the heat transfer limit. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the anti-dry-burning low-temperature pulsating heat pipe provided in Example 1;

[0028] Figure 2 A top view schematic diagram of the anti-dry-burning low-temperature pulsating heat pipe provided in Example 1;

[0029] Figure 3 This is a schematic diagram of the anti-dry-burning low-temperature pulsating heat pipe with a dual condensation section structure provided in Example 2;

[0030] Figure 4 A schematic diagram of the anti-dry-burning low-temperature pulsating heat pipe with a dual evaporation section structure provided in Example 3;

[0031] Figure 5 This is a schematic diagram of the multi-subject pulsating heat pipes arranged in a flat layout as provided in Example 4;

[0032] Figure 6 This is a schematic diagram of the sub-pulsating heat pipe provided in Example 5;

[0033] Figure 7 This is a schematic diagram of the liquid filling system provided in Example 7.

[0034] In the picture:

[0035] 1. Liquid injection connector;

[0036] 2. Sub-pulsating heat pipe; 201. Parallel pipe section; 202. Bend section; 203. Condensation section; 204. Insulation section; 205. Evaporation section; 206. First condensation section; 207. Second condensation section; 208. First insulation section; 209. Second insulation section; 210. First evaporation section; 211. Second evaporation section; 212. Straight connecting pipe;

[0037] 3. Thermally conductive fixing plate assembly; 301. First thermally conductive fixing plate; 302. Second thermally conductive fixing plate; 303. Third thermally conductive fixing plate; 304. Positioning groove;

[0038] 4. Buffer tank;

[0039] 5. Heat-conducting plate;

[0040] 6. High-purity helium cylinders;

[0041] 7. Molecular pump unit. Detailed Implementation

[0042] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0043] In the description of this invention, it should be understood that when a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be an intermediate component present simultaneously. When a component is considered to be "set" on another component, it can be directly set on the other component or there may be an intermediate component present simultaneously.

[0044] Furthermore, terms such as “long,” “short,” “inner,” and “outer” indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings. They are used only for the purpose of describing the present invention and are not intended to indicate or imply that the device or component referred to must have this specific orientation or operate in a specific orientational configuration. Therefore, they should not be construed as limitations of the present invention.

[0045] The present invention will now be described in detail with reference to the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the scope of protection of the present invention.

[0046] This invention provides a low-temperature pulsating heat pipe that prevents dry burning, suitable for applications such as cooling superconducting magnets, and can effectively improve the heat transfer limit of existing pulsating heat pipes.

[0047] The present invention provides a low-temperature pulsating heat pipe for preventing dry burning, comprising a liquid injection connector and at least two sub-pulsating heat pipes interconnected through the liquid injection connector. The sub-pulsating heat pipes have a serpentine structure, comprising several parallel pipe segments, with adjacent parallel pipe segments connected by a bend; at least two parallel pipe segments within the same sub-pulsating heat pipe are connected by a straight connecting pipe.

[0048] It is understandable that the direct connection pipe can connect different parallel pipe sections. Therefore, when a large heat exchange load causes a certain parallel pipe section to dry-burn, the working fluid in another parallel pipe section that is not dry-burn can quickly enter the dry-burn parallel pipe section through the direct connection pipe, and the working fluid in the dry-burn parallel pipe section can also quickly enter the other parallel pipe section that is not dry-burn through the direct connection pipe. This quickly breaks the dry-burn state in the dry-burn parallel pipe section, allowing the gas and liquid in the dry-burn parallel pipe section to resume circulation, thus preventing dry-burning of a certain parallel pipe section in the sub-pulsating heat pipe.

[0049] Similarly, when the heat exchange load is extremely high, causing a certain sub-pulsating heat pipe to dry-burn, the working fluid in another sub-pulsating heat pipe connected to that sub-pulsating heat pipe can enter the sub-pulsating heat pipe through the liquid injection connector, and the working fluid in that sub-pulsating heat pipe can also enter the other sub-pulsating heat pipe through the liquid injection connector. This breaks the dry-burning state in the sub-pulsating heat pipe, allowing the gas and liquid in the sub-pulsating heat pipe to resume circulation and preventing the dry-burning of a certain sub-pulsating heat pipe.

[0050] In summary, the anti-dry-burning low-temperature pulsating heat pipe provided by this invention has effectively avoided the dry-burning situation of both the parallel pipe section and the sub-pulsating heat pipe. Therefore, it can effectively suppress the occurrence of dry-burning and ultimately improve the heat transfer limit of the pulsating heat pipe.

[0051] The following description, in conjunction with the accompanying drawings, will introduce the anti-dry-burning low-temperature pulsating heat pipe of the present invention, as shown in Examples 1 to 4.

[0052] Example 1

[0053] See Figure 1 and Figure 2 The anti-dry-burning low-temperature pulsating heat pipe provided in this embodiment includes a liquid injection connector 1 and at least two sub-pulsating heat pipes 2 that are interconnected through the liquid injection connector 1. The sub-pulsating heat pipe 2 is formed by bending capillary tubes into a serpentine structure. The serpentine structure includes several parallel tube segments 201. Adjacent parallel tube segments 201 are connected by a bend 202. At least two parallel tube segments 201 within the same sub-pulsating heat pipe 2 are connected by a straight connecting pipe 212.

[0054] Specifically, the parallel pipe section 201 sequentially includes a condensing section 203, an insulating section 204, and an evaporating section 205. Each of the three sections—condensing section 203, insulating section 204, and evaporating section 205—can be connected to another parallel pipe section 201 via a straight connecting pipe 212, and at least one of these three sections is connected to another parallel pipe section 201. This can include several specific scenarios:

[0055] ① Two adjacent condensing sections 203 are connected by a straight connecting pipe 212, while two adjacent adiabatic sections 204 or two adjacent evaporating sections 205 are not connected by a straight connecting pipe 212.

[0056] Alternatively, two adjacent insulation sections 204 may be connected by a straight connecting pipe 212, while two adjacent condensing sections 203 or two adjacent evaporating sections 205 may not be connected by a straight connecting pipe 212.

[0057] Alternatively, two adjacent evaporation sections 205 may be connected by a straight pipe 212, while two adjacent condensation sections 203 or two adjacent insulation sections 204 may not be connected by a straight pipe 212.

[0058] ② Two adjacent condensing sections 203 and two adjacent adiabatic sections 204 are each connected by a straight connecting pipe 212, while two adjacent evaporating sections 205 are not connected by a straight connecting pipe 212.

[0059] Alternatively, two adjacent condensing sections 203 and two adjacent evaporating sections 205 are each connected by a straight connecting pipe 212, while two adjacent insulating sections 204 are not connected by a straight connecting pipe 212.

[0060] Alternatively, two adjacent insulation sections 204 and two adjacent evaporation sections 205 are each connected by a straight connecting pipe 212, while two adjacent condensation sections 203 are not connected by a straight connecting pipe 212.

[0061] ③ Two adjacent condensing sections 203, two adjacent adiabatic sections 204, and two adjacent evaporating sections 205 are each connected by a straight connecting pipe 212.

[0062] The straight pipes 212 connected at different locations can facilitate gas-liquid communication at different locations. Setting multiple straight pipes 212 can promote fluid exchange between adjacent parallel pipe sections 201 from multiple locations, shorten the gas-liquid exchange time between adjacent parallel pipe sections 201, and effectively suppress dry burning.

[0063] In this embodiment, the sub-pulsating heat pipe 2 is formed by bending a capillary tube of equal diameter. In some other embodiments, the sub-pulsating heat pipe 2 may also be formed by welding together several parallel pipe sections 201 and several bend sections 202.

[0064] In this embodiment, each of the sub-pulsating heat pipes 2 is stacked vertically, and a set of thermally conductive fixing plates 3 is provided between two adjacent sub-pulsating heat pipes 2. The thermally conductive fixing plate set 3 includes a first thermally conductive fixing plate 301 located at one end of the sub-pulsating heat pipe 2 (e.g., the condensation section 203) and a second thermally conductive fixing plate 302 located at the other end of the sub-pulsating heat pipe 2 (e.g., the evaporation section 205).

[0065] Furthermore, both the first heat-conducting fixing plate 301 and the second heat-conducting fixing plate 302 are provided with positioning grooves 304 for accommodating the corresponding sub-pulsating heat pipes 2. The positioning grooves 304 and the corresponding sub-pulsating heat pipes 2 are filled with solder, which can reduce the thermal resistance between the sub-pulsating heat pipes 2 and the heat-conducting fixing plate assembly 3, and also achieve a reliable fixed connection between the sub-pulsating heat pipes 2 and the heat-conducting fixing plate assembly 3.

[0066] In this embodiment, the heat-conducting fixing plate group 3 has four layers, and solder is also filled between two adjacent heat-conducting fixing plate groups 3 to play a role in fixing and heat transfer; furthermore, the fixing and heat transfer materials used can also be high-purity copper or high-purity aluminum, and the materials of the capillary used can be stainless steel capillary or high-purity copper capillary.

[0067] Taking a superconducting magnet as an example of the component to be cooled, when in use, the first heat-conducting fixing plate 301 is connected to the cold head of the refrigerator, and the second heat-conducting fixing plate 302 is connected to the superconducting magnet. The working fluid can then achieve gas-liquid two-phase pulsating flow or circulation within each sub-pulsating heat pipe 2, thereby continuously providing cooling to the superconducting magnet.

[0068] Optionally, the cross-sectional shape of the capillary can be circular, square, or triangular, etc., and this embodiment does not limit this.

[0069] See Figure 2 In this embodiment, the anti-dry-burning low-temperature pulsating heat pipe also includes a buffer tank 4 connected to each of the sub-pulsating heat pipes 2 via the liquid injection connector 1. The buffer tank 4 is specifically designed for the low-temperature pulsating heat pipe. Its typical function is to fill it with working fluid, and after reaching a predetermined filling rate, close the valve to disconnect the pulsating heat pipe from the buffer tank.

[0070] In this embodiment, a buffer tank 4 needs to be connected during liquid filling. During operation, the buffer tank 4 is also connected to each sub-pulsating heat pipe 2. Its function is to automatically adjust the liquid filling rate of each sub-pulsating heat pipe 2, preventing excessively high or low pressure, and enabling the anti-dry-burning low-temperature pulsating heat pipe to adapt to different heat loads. When the heat load is high, the working fluid flows from each sub-pulsating heat pipe 2 to the buffer tank 4, preventing excessively high pressure in the evaporation section of each sub-pulsating heat pipe 2 from causing dry burning. When the heat load is low, the working fluid flows from the buffer tank 4 into each sub-pulsating heat pipe 2, preventing excessively low pressure in each sub-pulsating heat pipe 2 from causing it to stop operating.

[0071] It should be noted that the anti-dry-burning low-temperature pulsating heat pipe provided in this embodiment can improve the heat transfer limit for all types of pulsating heat pipes with different working fluids. When the working fluid in the sub-pulsating heat pipe 2 is a low-temperature working fluid such as helium, hydrogen, neon, nitrogen, oxygen, or methane, the heat transfer limit is relatively low in the prior art. Therefore, the anti-dry-burning low-temperature pulsating heat pipe provided in this invention has a particularly significant effect on improving the heat transfer limit. Furthermore, the ideal liquid filling rate of the anti-dry-burning low-temperature pulsating heat pipe provided in this embodiment is between 20% and 80%. When the liquid filling rate is less than 20%, the pulsating heat pipe is prone to dry-burning. When the liquid filling rate is greater than 80%, the pulsation phenomenon is weak, and the heat transfer effect is poor.

[0072] Specifically, experiments have shown that when helium is used as the working fluid, the upper limit of the heat transfer load of the anti-dry-burning low-temperature pulsating heat pipe provided by this invention can reach 25W, which far exceeds the heat transfer limit of 1.29W obtained by the Institute of Physics and Chemistry of the Chinese Academy of Sciences.

[0073] The anti-dry-burning low-temperature pulsating heat pipe provided in this embodiment has the following advantages:

[0074] ① Parallel pipe sections 201 within the same sub-pulsating heat pipe 2 are interconnected by a straight connecting pipe 212; different sub-pulsating heat pipes 2 are interconnected by a liquid injection connector 1; and each sub-pulsating heat pipe 2 is interconnected with a buffer tank 4 through a liquid injection connector 1. This achieves three levels of anti-dry burning measures, greatly suppressing the occurrence of dry burning and thus improving the heat transfer limit.

[0075] ②The sub-pulsating heat pipes 2 are stacked, which results in a compact structure, a small space occupation, and a high heat exchange rate per unit volume.

[0076] ③ It operates with a buffer tank, which can automatically adjust the liquid filling rate of the pulsating heat pipe according to the size of the heat load, adapt to different heat loads, and prevent the pulsating heat pipe from burning dry.

[0077] ④ The shape of the fixed heat-conducting plate between the evaporation section and the condensation section of the pulsating heat pipe is not fixed and can be designed according to specific application requirements. It is even possible to eliminate the fixed heat-conducting plate and directly embed the evaporation section and / or condensation section of the pulsating heat pipe into the device to be cooled and / or the cold head of the refrigerator.

[0078] Example 2

[0079] See Figure 3 The anti-dry-burning low-temperature pulsating heat pipe provided in this embodiment includes a liquid injection connector 1 and at least two sub-pulsating heat pipes 2 that are interconnected through the liquid injection connector 1. The sub-pulsating heat pipe 2 is formed by bending capillary tubes into a serpentine structure. The serpentine structure includes several parallel tube segments 201. Adjacent parallel tube segments 201 are connected by a bend 202. At least two parallel tube segments 201 within the same sub-pulsating heat pipe 2 are connected by a straight connecting pipe 212.

[0080] Specifically, the parallel pipe section 201 sequentially includes a first condensing section 206, a first insulating section 208, an evaporating section 205, a second insulating section 209, and a second condensing section 207. Each of the five parallel pipe sections 201—the first condensing section 206, the first insulating section 208, the evaporating section 205, the second insulating section 209, and the second condensing section 207—can be connected to another parallel pipe section 201 via a straight connecting pipe 212. Furthermore, at least one of these five sections can be connected to another parallel pipe section 201. Specific configurations may include those similar to those described in Embodiment 1, and will not be repeated here.

[0081] In this embodiment, each of the sub-pulsating heat pipes 2 is stacked vertically, and a set of thermally conductive fixing plates 3 is provided between two adjacent sub-pulsating heat pipes 2. The thermally conductive fixing plates 3 include a first thermally conductive fixing plate 301 located in the first condensation section 206, a third thermally conductive fixing plate 303 located in the evaporation section 205, and a second thermally conductive fixing plate 302 located in the second condensation section 207.

[0082] In use, the anti-dry-burning low-temperature pulsating heat pipe is placed horizontally. The first thermally conductive fixing plate 301 is placed at one refrigerator unit, the third thermally conductive fixing plate 303 is placed at the superconducting magnet and the component to be cooled, and the second thermally conductive fixing plate 302 is placed at another refrigerator unit. The working fluid can then achieve gas-liquid equilibrium circulation within each sub-pulsating heat pipe 2, thereby continuously cooling the component to be cooled. This structural design is advantageous for using two refrigerator units to cool the component, and is suitable for applications where the heat load of the component to be cooled is large.

[0083] The anti-dry-burning low-temperature pulsating heat pipe provided in this embodiment has the following advantages:

[0084] The parallel tube section 201 includes an evaporation section 205 and two condensation sections, which can use two refrigerators to cool a component to be cooled, making it suitable for applications where the heat load of the component to be cooled is large.

[0085] Example 3

[0086] See Figure 4 The anti-dry-burning low-temperature pulsating heat pipe provided in this embodiment includes a liquid injection connector 1 and at least two sub-pulsating heat pipes 2 that are interconnected through the liquid injection connector 1. The sub-pulsating heat pipe 2 is formed by bending capillary tubes into a serpentine structure. The serpentine structure includes several parallel tube segments 201. Adjacent parallel tube segments 201 are connected by a bend 202. At least two parallel tube segments 201 within the same sub-pulsating heat pipe 2 are connected by a straight connecting pipe 212.

[0087] Specifically, the parallel pipe section 201 provided in this embodiment sequentially includes a first evaporation section 210, a first insulation section 208, a condensation section 203, a second insulation section 209, and a second evaporation section 211. Each of the five components of the parallel pipe section 201—the first evaporation section 210, the first insulation section 208, the condensation section 203, the second insulation section 209, and the second evaporation section 211—can be connected to another parallel pipe section 201 via a straight connecting pipe 212. Furthermore, at least one of the five components—the first evaporation section 210, the first insulation section 208, the condensation section 203, the second insulation section 209, and the second evaporation section 211—can be connected to another parallel pipe section 201. Specific configurations may include those similar to those described in Embodiment 1, and will not be repeated here.

[0088] In this embodiment, each of the sub-pulsating heat pipes 2 is stacked vertically, and a set of thermally conductive fixing plates 3 is provided between two adjacent sub-pulsating heat pipes 2. The thermally conductive fixing plates 3 include a first thermally conductive fixing plate 301 located in the first evaporation section 210, a third thermally conductive fixing plate 303 located in the condensation section 203, and a second thermally conductive fixing plate 302 located in the second evaporation section 211.

[0089] In use, the anti-dry-burning low-temperature pulsating heat pipe is placed horizontally. Then, the first heat-conducting fixing plate 301 is placed at one component to be cooled, the third heat-conducting fixing plate 303 is placed at the refrigerator, and the second heat-conducting fixing plate 302 is placed at another component to be cooled. The working fluid can then achieve gas-liquid equilibrium circulation within each sub-pulsating heat pipe 2, thereby continuously cooling the two components. This structural design is advantageous for using one refrigerator to cool two components and is suitable for applications with high refrigerator cooling capacity.

[0090] The anti-dry-burning low-temperature pulsating heat pipe provided in this embodiment has the following advantages:

[0091] The parallel tube section 201 includes two evaporation sections and one condensation section 203, which can use one refrigerator to cool two components to be cooled, and is suitable for applications with large refrigeration capacity of the refrigerator.

[0092] Example 4

[0093] See Figure 5 The anti-dry-burning low-temperature pulsating heat pipe provided in this embodiment includes a liquid injection connector 1 and at least two sub-pulsating heat pipes 2 that are interconnected through the liquid injection connector 1. The sub-pulsating heat pipe 2 is formed by bending capillary tubes into a serpentine structure. The serpentine structure includes several parallel tube segments 201. Adjacent parallel tube segments 201 are connected by a bend 202. At least two parallel tube segments 201 within the same sub-pulsating heat pipe 2 are connected by a straight connecting pipe 212.

[0094] Specifically, the parallel pipe section 201 provided in this embodiment sequentially includes a condensing section 203, an insulating section 204, and an evaporating section 205. Each of the three sections—condensing section 203, insulating section 204, and evaporating section 205—can be connected to another parallel pipe section 201 via a straight connecting pipe 212, and at least one of the three sections—condensing section 203, insulating section 204, and evaporating section 205—is connected to another parallel pipe section 201. Specific scenarios may include those described in Embodiment 1, which will not be repeated here.

[0095] In this embodiment, the sub-pulsating heat pipes 2 are arranged side by side in a horizontal direction. Optionally, each sub-pulsating heat pipe 2 is mounted and fixed on a heat-conducting plate 5 that is sufficient to cover the entire sub-pulsating heat pipe 2.

[0096] When using:

[0097] On the one hand, each heat-conducting plate 5 can be placed at one end corresponding to the condensation section 203 to a refrigerator, and all the ends of each heat-conducting plate 5 corresponding to the evaporation section 205 can be placed at the lower superconducting magnet waiting to be cooled components. The working fluid can then achieve gas-liquid equilibrium circulation within each sub-pulsating heat pipe 2, thereby continuously cooling the components to be cooled. This structural design is advantageous for using multiple refrigerators to cool the components to be cooled, and is suitable for application scenarios where the heat capacity of the components to be cooled is large or where a large amount of heat is generated when the magnet loses its quench.

[0098] Alternatively, one end of each heat-conducting plate 5 corresponding to the evaporation section 205 can be placed at a component to be cooled, while the ends of all heat-conducting plates 5 corresponding to the condensation section 203 can be placed at a higher position on the refrigerator. The working fluid can then achieve a gas-liquid equilibrium circulation within each sub-pulsating heat pipe 2, thereby continuously cooling multiple components. This structural design is advantageous for using a single refrigerator to cool multiple components, making it suitable for applications with very high cooling capacity.

[0099] Of course, the third scenario involves multiple refrigerators corresponding to multiple components to be cooled, in order to match the heat transfer. This means placing one end of each heat-conducting plate 5 corresponding to the condensation section 203 at a refrigerator and one end of each heat-conducting plate 5 corresponding to the evaporation section 205 at a component to be cooled. The working fluid can then achieve a gas-liquid balance circulation within each sub-pulsating heat pipe 2, thereby continuously cooling multiple components. This structural design is advantageous for using multiple refrigerators to cool multiple components.

[0100] The anti-dry-burning low-temperature pulsating heat pipe provided in this embodiment has the following advantages:

[0101] The sub-pulsating heat pipes 2 are laid flat, which allows multiple refrigerators to cool one device, one refrigerator to cool multiple devices, or multiple refrigerators to cool multiple components. This is suitable for application scenarios where the cooling load of a single device being cooled and the cooling power of a single refrigerator differ greatly.

[0102] Example 5

[0103] See Figure 6 The difference between the anti-dry-burning low-temperature pulsating heat pipe provided in this embodiment and the anti-dry-burning low-temperature pulsating heat pipe in Embodiment 4 is as follows:

[0104] The adiabatic section of the sub-pulsating heat pipe 2 provided in this embodiment is curved.

[0105] It should be noted that low-temperature pulsating heat pipes are mainly used in high-efficiency heat transfer in cryogenic systems, such as cooling superconducting magnets. Compared to metals like copper, they have advantages such as high thermal conductivity, long heat transfer distance, small temperature difference, light weight, and flexible arrangement. Compared to traditional pulsating heat pipes, they have a simpler structure, are easier to manufacture, and can operate under microgravity. Therefore, they are also very advantageous in weight- and volume-sensitive applications such as aerospace, for example, in the cryogenic heat transfer of space telescopes. Therefore, the adiabatic section of a pulsating heat pipe can be bent arbitrarily, such as... Figure 6 As shown.

[0106] Similarly, the evaporation and condensation sections of a pulsating heat pipe can be configured into any shape as needed. For example, the evaporation section can be embedded within a superconducting magnet, eliminating the need for a heat-conducting fixing plate. Alternatively, the condensation section can be embedded into the refrigerator's cold head, also eliminating the need for a heat-conducting fixing plate.

[0107] The direction of the pulsating heat pipe arrangement is also arbitrary, and it does not need to be set vertically or horizontally.

[0108] In addition, its heat transfer distance can be very long, that is, the length of the insulation section can be extended to several meters or even tens of meters.

[0109] This embodiment applies to the sub-pulsating heat pipe in all the embodiments described above.

[0110] Example 6

[0111] This embodiment provides a method for determining the inner diameter of a sub-pulsating heat pipe, applicable to the sub-pulsating heat pipes in all the above embodiments.

[0112] It is important to note that the inner diameter of a pulsating heat pipe is a key parameter in its manufacturing. The inner diameter is the most important geometric dimension of a pulsating heat pipe, essentially revealing its fundamental definition. In metal fin cooling, heat is transferred through atomic vibrations, phonon conduction, and electron conduction. In traditional capillary heat pipes, the gas phase is transported through the pressure difference between the hot and cold ends, while the liquid phase refluxes due to capillary action. In gravity heat pipes, the liquid phase refluxes only with the aid of gravity. Single-phase natural convection circulation is driven by buoyancy, while forced liquid convection cooling requires an external mechanical pump. Pulsating heat pipes rely on the oscillation or pulsating motion of liquid plugs and bubbles within the pipe to complete the working fluid circulation. Whether liquid plugs and bubbles can form depends on the relative strength of gravity and surface tension, which can be described by the Bond number (denoted by Bo).

[0113]

[0114] in:

[0115] D is the inner diameter of the pulsating heat pipe, in meters (m).

[0116] σ is the surface tension, with units of N / m;

[0117] g is the acceleration due to gravity, and its unit is m / s². 2 ;

[0118] ρ v and ρ l These are the gaseous density and liquid density of the working fluid in its saturated state, respectively, in kg / m³. 3 .

[0119] Research shows that when the Bond number Bo ≤ 2, the effect of surface tension on the working fluid is stronger than that of gravity, thus enabling the formation of a gas-liquid plug within the capillary. Since the flow within the tube is primarily driven by surface tension, the inner diameter of the capillary is given by the following equation:

[0120]

[0121] Among them, D crit This represents the critical diameter; the meanings of other symbols are as described above.

[0122] Experimental work shows that the inner diameter of a room-temperature pulsating heat pipe ranges from 1 mm to 7.2 mm. The inner diameter of a low-temperature pulsating heat pipe ranges from 0.5 mm to 2.3 mm. The critical diameter under microgravity conditions is greater than that under gravity conditions.

[0123] Example 7

[0124] This embodiment provides a liquid filling system and liquid filling method, applicable to the anti-dry-burning low-temperature pulsating heat pipes in all the above embodiments.

[0125] The pulsating heat pipe with a buffer tank is designed for low-temperature pulsating heat pipes (for applications with temperatures below -150°C).

[0126] The working fluid in a low-temperature pulsating heat pipe is gaseous at room temperature. If helium is directly injected into the pulsating heat pipe at room temperature to liquefy it and achieve the specified liquid filling rate, the filling pressure would be too high to achieve this. Therefore, experimental setups for the heat transfer characteristics of low-temperature pulsating heat pipes are equipped with a dedicated liquid filling system.

[0127] The filling system provided in this embodiment is as follows: Figure 7As shown, the system consists of a buffer tank 4, a high-purity helium cylinder 6, a molecular pump unit 7, three shut-off valves (valve V1, valve V2, and valve V3), two pressure sensors (pressure sensor P1 and pressure sensor P2), and stainless steel piping. The cryogenic working fluid used is high-purity helium (99.999%). Before the cryogenic pulsating heat pipes begin operation, the molecular pump unit 7 is used to purge and purify the residual air in the piping of each sub-pulsating heat pipe 2 and the filling system. The filling system is equipped with two pressure sensors: pressure sensor P1 detects pressure fluctuations in the condensation section of the pulsating heat pipe, and pressure sensor P2 is located on the buffer tank to monitor the tank pressure and calculate the filling rate.

[0128] The specific operating steps for filling a low-temperature pulsating heat pipe are as follows:

[0129] (1) Collect and record temperature and pressure data.

[0130] (2) High-purity helium gas and a set of molecular pumps were used to purge and purify the connecting pipes of the pulsating heat pipe, buffer tank, and liquid filling system to prevent residual air or other impurities in the pipes from affecting the experiment. The specific procedure was as follows: First, valves V1 and V2 were opened, valve V3 was closed, and the molecular pumps were used to evacuate the pulsating heat pipe and liquid filling system to a high vacuum (<1×10⁻⁶). -3 Pa); then close valve V2 and open valves V1 and V3 to fill the pulsating heat pipe and buffer tank with 99.999% high-purity helium from the helium cylinder; repeat the same process more than 5 times to thoroughly remove impurities from the pulsating heat pipe and the filling system, and then evacuate to a high vacuum.

[0131] (3) After the purification process is completed, open valve V3, close valves V1 and V2, open the helium cylinder, fill the buffer tank with high-purity helium, and then close all valves. Record the initial pressure P0 of the buffer tank at this time.

[0132] (4) Open valve V1 and close valves V2 and V3. High-purity helium will enter the pulsating heat pipe from the buffer tank.

[0133] (5) Use another set of molecular pumps to evacuate the vacuum chamber until the vacuum level in the vacuum chamber is lower than 1×10⁻⁶. -3 After Pa, the GM chiller is started to cool the pulsating heat pipe.

[0134] (6) As the temperature of the condensing section of the pulsating heat pipe decreases, the pressure also decreases. When it reaches the liquid helium temperature range, liquid helium begins to form, and the pressure drops rapidly. Under the influence of gravity, the liquid helium moves from the condensing section to the evaporating section, accelerating the cooling of the evaporating section to the liquid helium temperature. When the pressure in the buffer tank drops to the pressure P1 corresponding to the target filling rate, valve V1 is closed, isolating the pulsating heat pipe from the filling system. At this point, the inside of the pulsating heat pipe is in an initial state of alternating gas plugs and liquid plugs, and the filling process ends.

[0135] The filling ratio is used to represent the mass of liquid helium filled into a cryogenic pulsating heat pipe. For comparison with existing research data, the filling ratio of a liquid helium pulsating heat pipe is defined as the ratio of the liquid helium volume at 4.215 K to the volume of the pulsating heat pipe. When calculating the filling ratio, the helium in the pulsating heat pipe and the liquid-filled system is considered an ideal gas. According to the law of conservation of mass and the ideal gas law, the mass of helium filled, m... t It can be calculated using the following formula:

[0136]

[0137] in:

[0138] P0 and P1 are the initial and final pressures of the buffer tank at the start and end of the filling process, respectively, in Pa; V FT and V BT These are the volumes of the filling pipe (from valve V1 to the pulsating heat pipe) and the buffer tank, respectively, in cubic meters (m³). 3 ;T FT and T BT These are the average temperatures of the filling pipe and the buffer tank, respectively, in K; R g R is the gas constant of helium. g =2077 J / (kg·K); m t The mass of the working fluid charged into the pulsating heat pipe is expressed in kg.

[0139] The mass of liquid helium filled into the pulsating heat pipe is the sum of the masses of saturated helium gas and saturated liquid helium. Since the densities of saturated helium gas and saturated liquid helium, as well as the mass of helium filled into the pulsating heat pipe, are known, the volume of saturated liquid helium can be calculated using the following formula:

[0140] m t =ρ l V l +ρ v (V PHP -V l (Equation 2);

[0141] Among them, V PHP and V l These represent the volume of the pulsating heat pipe and the volume of liquid helium inside, respectively, in cubic meters (m³). 3 ;ρ v and ρ l Densities of saturated helium gas and saturated liquid helium at 4.215 K, respectively, in kg / m³. 3 .

[0142] Therefore, the filling rate is:

[0143]

[0144] By combining Equations 1 through 3, the filling rate of the pulsating heat pipe can be determined based on the initial and final pressures of the buffer tank. This formula for calculating the filling rate takes into account the influence of the filling pipe volume, while the volume of the remaining pipes in the filling system is considered as part of the buffer tank volume.

[0145] It should be noted that this filling method is also applicable to other cryogenic working fluids.

[0146] The recommended filling rate for pulsating heat pipes is between 20% and 80%. If the filling rate is too low, the pipe is prone to burning out, while if the filling rate is too high, the flow resistance is too great, making it difficult to start up and operate.

[0147] In addition to controlling the filling rate before the low-temperature pulsating heat pipe starts operating, the buffer tank also automatically adjusts the filling rate and pressure during operation to prevent it from burning dry. Simply open valve V1 to connect the buffer tank to the low-temperature pulsating heat pipe for operation.

[0148] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0149] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A liquid filling method for a low-temperature pulsating heat pipe designed to prevent dry burning, applicable to low-temperature pulsating heat pipes designed to prevent dry burning, characterized in that, The anti-dry-burning low-temperature pulsating heat pipe includes a liquid injection connector (1) and at least two sub-pulsating heat pipes (2) that are interconnected through the liquid injection connector (1). The sub-pulsating heat pipe (2) has a serpentine structure, which includes several parallel pipe segments (201), and two adjacent parallel pipe segments (201) are connected by a bend (202). At least two parallel pipe segments (201) within the same sub-pulsating heat pipe (2) are connected by a straight connecting pipe (212); The parallel pipe section (201) includes, in sequence, a condensation section (203), an insulation section (204), and an evaporation section (205). The condensing section (203), the insulating section (204), and the evaporating section (205) of the parallel pipe section (201) can each be connected to another parallel pipe section (201) through a straight connecting pipe (212), and at least one of the condensing section (203), the insulating section (204), and the evaporating section (205) is connected to another parallel pipe section (201); Each of the sub-pulsating heat pipes (2) is stacked vertically, and a set of heat-conducting fixing plates (3) is provided between two adjacent sub-pulsating heat pipes (2). The heat-conducting fixing plate assembly (3) includes a first heat-conducting fixing plate (301) located at one end of the sub-pulsating heat pipe (2) and a second heat-conducting fixing plate (302) located at the other end of the sub-pulsating heat pipe (2). The parallel pipe section (201) includes two condensing sections (203) and one evaporating section (205); or, the parallel pipe section (201) includes two evaporating sections (205) and one condensing section (203). The anti-dry-burning low-temperature pulsating heat pipe is filled with liquid through a liquid filling system. The filling system consists of a buffer tank (4), a high-purity helium cylinder (6), a molecular pump unit (7), three shut-off valves, two pressure sensors, and stainless steel pipes; the cryogenic working fluid used is 99.999% high-purity helium; the three shut-off valves include valve V1, valve V2, and valve V3, and the two pressure sensors include pressure sensor P1 and pressure sensor P2. Before the low-temperature pulsating heat pipe is put into operation, the residual air in the pipes of each sub-pulsating heat pipe (2) and the liquid filling system is purged and cleaned using a molecular pump unit (7). The liquid filling system is equipped with two pressure sensors. Pressure sensor P1 is used to detect the pressure fluctuation of the condensing section of the pulsating heat pipe, and pressure sensor P2 is set on the buffer tank to monitor the pressure of the buffer tank and calculate the liquid filling rate. The liquid filling methods for preventing dry burning of low-temperature pulsating heat pipes include: (1) Collect and record temperature and pressure data; (2) High-purity helium and a set of molecular pump units were used to purge and purify the connecting pipes of the pulsating heat pipe, buffer tank and liquid filling system to prevent residual air or other impurities in the pipes from affecting the experiment; the specific process was as follows: first open valves V1 and V2, close valve V3, and use the molecular pump unit to evacuate the pulsating heat pipe and liquid filling system to a high vacuum, where a high vacuum means a gas pressure value <1×10 -3 Pa; then close valve V2 and open valves V1 and V3 to fill the pulsating heat pipe and buffer tank with 99.999% high-purity helium from the helium cylinder; repeat the same process more than 5 times to thoroughly remove impurities from the pulsating heat pipe and the liquid filling system, and then evacuate to a high vacuum. (3) After the purification process is completed, open valve V3, close valves V1 and V2, open the helium cylinder, fill the buffer tank with high-purity helium, and then close all valves. Record the initial pressure P0 of the buffer tank at this time. (4) Open valve V1 and close valves V2 and V3. High-purity helium gas will enter the pulsating heat pipe from the buffer tank. (5) Use another set of molecular pump units to evacuate the vacuum chamber until the vacuum level in the vacuum chamber is lower than 1×10 -3 After Pa, the GM chiller is started to cool the pulsating heat pipe; (6) As the temperature of the condensing section of the pulsating heat pipe decreases, the pressure also decreases. When it drops to the liquid helium temperature range, liquid helium begins to be generated, and the pressure drops rapidly. Under the action of gravity, the liquid helium moves from the condensing section to the evaporating section, accelerating the cooling of the evaporating section to the liquid helium temperature. When the pressure of the buffer tank drops to the pressure P1 corresponding to the target filling rate, valve V1 is closed, and the pulsating heat pipe is isolated from the filling system. At this time, the pulsating heat pipe is in the initial state of alternating gas plugs and liquid plugs, and the filling process ends. The filling rate is: ； V PHP and V l These represent the volume of the pulsating heat pipe and the volume of liquid helium inside, respectively, in cubic meters (m³). 3 .

2. The liquid filling method for the anti-dry-burning low-temperature pulsating heat pipe according to claim 1, characterized in that, Each of the sub-pulsating heat pipes (2) is laid out in parallel along the horizontal direction.

3. The liquid filling method for the anti-dry-burning low-temperature pulsating heat pipe according to claim 1, characterized in that, The cross-sectional shape of the sub-pulsating heat pipe (2) is circular, square or triangular.

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