Visualized low temperature pulsating heat pipe experimental device

Abstract

The present invention relates to the technical field of pulsating heat pipes, and provides a visualized low-temperature pulsating heat pipe experimental device, including: a visualized low-temperature insulation system, a low-temperature pulsating heat pipe, a filling system, a vacuum system and a collection system; the visualized low-temperature insulation system includes a vacuum cover and a radiation shield arranged in the vacuum cover, and the side wall of the vacuum cover is provided with a visualized optical window; the low-temperature pulsating heat pipe is arranged in a chamber surrounded by the radiation shield; the filling system is arranged outside the vacuum cover, and is connected to the low-temperature pulsating heat pipe through a pipeline extending into the vacuum cover; the vacuum system is connected to the vacuum cover and the low-temperature pulsating heat pipe respectively; the collection system includes corresponding visualized optical windows, and light sources and collection devices are respectively arranged on both sides of the vacuum cover. The present invention can observe and record the two-phase flow process of the low-temperature pulsating heat pipe, and can also perform continuous measurement analysis and visualized observation.

Description

Technical Field

[0001] The invention relates to the technical field of pulsating heat pipes, in particular to a visualized low-temperature pulsating heat pipe experimental device. Background Art

[0002] Pulsating Heat Pipe (PHP or OHP), also known as oscillating heat pipe, is a new type of heat pipe. Since its invention in the 1990s, it has attracted widespread attention from researchers due to its unique working principle and excellent heat transfer performance. The working process of pulsating heat pipe involves phenomena such as evaporation and condensation of liquid film, dynamic changes in the contact angle between the working fluid and the tube wall, growth and combination of bubbles, and nucleate boiling. Although the structure of pulsating heat pipe is simple, the coupling of fluid dynamics and thermodynamics involved in the heat and mass transfer process in the tube makes its working mechanism very complex. In order to better understand the operating mechanism and heat transfer process of pulsating heat pipe, visualization experiment is the first choice.

[0003] It is easy to realize visualization research on room temperature pulsating heat pipes. After more than 20 years of development, certain progress has been made in both theory and experiment and application. However, the research on low temperature pulsating heat pipes has just started in recent years. The experimental research on low temperature pulsating heat pipes at home and abroad mainly uses H2, Ne, N2, and He. However, the thermal properties of low temperature working fluids are very different from those of room temperature working fluids, especially in terms of viscosity, surface tension, and latent heat of vaporization. As a result, the flow and heat exchange process of low temperature working fluids are very different from those of room temperature working fluids, resulting in the inability to directly apply the visualization experiments and theoretical results of room temperature to low temperature pulsating heat pipes.

[0004] For the study of low-temperature pulsating heat pipes, numerical simulation is usually used to study the flow state of cryogenic working fluids. Low-temperature temperature zone refrigeration heat transfer generally uses low-temperature liquid working fluids. Nitrogen boiling point 77K, hydrogen 20K, helium 4.2K, neon 27K, is a commonly used working fluid for low-temperature pulsating heat pipe heat transfer. The low-temperature temperature zone refers to the temperature less than 120K. The refrigeration from 120K to 300K is a general cooling temperature zone. Since the two-phase flow system in the low-temperature pulsating heat pipe is a complex system, its heat transfer and flow mechanisms are complex and diverse, and are directly related to the flow pattern of the two-phase flow. The heat transfer and hydraulic characteristics under different flow patterns vary greatly, and it is difficult to accurately describe the heat exchange process through numerical simulation. Without mastering these flow pattern information and gas-liquid distribution, it is impossible to obtain accurate heat transfer and flow correlation equations. Visualization is a necessary means of research.

[0005] The present invention is proposed in view of the above. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a visual low-temperature pulsating heat pipe experimental device.

[0007] A visualized low-temperature pulsating heat pipe experimental device according to an embodiment of the present invention includes:

[0008] Visualize cryogenic insulation system, cryogenic pulsating heat pipe, charging system, vacuum system and acquisition system;

[0009] The visualized low-temperature insulation system comprises a vacuum cover and a radiation shield arranged in the vacuum cover, and a side wall of the vacuum cover is provided with a visualized optical window;

[0010] The low-temperature pulsating heat pipe is arranged in the chamber surrounded by the radiation protection cover;

[0011] The filling system is arranged outside the vacuum cover, connected to the low-temperature pulsating heat pipe through a pipeline extending into the vacuum cover, and is used to fill the low-temperature pulsating heat pipe with working fluid;

[0012] The vacuum system is connected to the vacuum cover and the low-temperature pulsating heat pipe respectively, and is used to achieve a high vacuum environment in the vacuum cover and the low-temperature pulsating heat pipe;

[0013] The collection system comprises a light source and a collection device which are respectively arranged on both sides of the vacuum cover corresponding to the visualization optical window.

[0014] According to one embodiment of the present invention, a flange is provided on the upper part of the vacuum cover, a refrigerator is provided on the flange, a cold head of the refrigerator is connected to the low-temperature pulsating heat pipe via a thermal bridge, and the thermal bridge is connected to the radiation protection cover.

[0015] Specifically, the refrigerator is connected to the low-temperature pulsating heat pipe and the radiation shield through a heat-conducting thermal bridge to transfer the cooling capacity of the refrigerator so that the temperature of the low-temperature pulsating heat pipe and the radiation shield is maintained in a low temperature zone.

[0016] It should be noted that the contact surfaces between the low-temperature pulsating heat pipe, refrigerator, radiation shield and thermal bridge need to be polished smooth, and indium sheets and Apiezon N vacuum thermal conductive adhesive should be provided to reduce contact thermal resistance and enhance thermal conductivity.

[0017] In one embodiment, the vacuum cover is a cylindrical structure made of stainless steel, the lower part is sealed by welding, the upper part is detachably connected to the flange, and the vacuum cover and the flange are sealed by a sealing ring and vacuum sealant.

[0018] In one embodiment, the radiation shield is a cylindrical structure made of copper or aluminum.

[0019] In one embodiment, the refrigerator can be a pulse tube refrigerator, a Stirling refrigerator, a GM refrigerator or other low temperature refrigerator, which is fixedly connected to the flange.

[0020] In one embodiment, the heat-conducting heat bridge is made of copper or aluminum and is provided with threaded holes for connecting with the cold head of the refrigerator and the low-temperature pulsating heat pipe.

[0021] According to one embodiment of the present invention, the visual low-temperature insulation system further comprises a hoisting rod, which is respectively connected to the radiation shield and the flange;

[0022] The radiation shield is symmetrically provided with through holes, and the channel formed by connecting the through holes forms a visualized optical channel;

[0023] Wherein, when the hoisting rod hoists the radiation protection cover into the vacuum cover, the visualization optical channel corresponds to the visualization optical window.

[0024] Specifically, the radiation shield is hoisted in the vacuum shield by a hoisting rod. This arrangement further reduces the stress on the cold head of the refrigerator, preventing stress deformation from affecting the operation of the refrigerator.

[0025] In one embodiment, in order to increase the strength of the hanging rod, the hanging rod of this embodiment is made of stainless steel.

[0026] In one embodiment, in order to reduce the solid conduction heat leakage of the lifting rod, the lifting rod of this embodiment is set as a thin-walled hollow structure, and air holes are opened on the tube wall. During the vacuuming process, the gas in the tube wall is extracted to eliminate the problem of gas heat leakage.

[0027] According to one embodiment of the present invention, the surface of the visualization optical window is coated with an infrared reflective material coating.

[0028] Specifically, by coating the surface of the visualization optical window with a coating made of infrared reflective material, the radiation heat leakage from ambient light to the inside of the vacuum enclosure is reduced.

[0029] It should be noted that to achieve insulation in a low-temperature environment, it is necessary to reduce convection, heat conduction, and radiation, and to reduce heat leakage from three aspects. In conjunction with a low-temperature refrigerator to achieve low temperature, high vacuum only reduces air convection, and a radiation shield is also needed to reduce heat radiation, and the cross-sectional area of ​​the lifting rod should be reduced to reduce heat conduction.

[0030] In one embodiment, two visualization optical windows are symmetrically arranged on both sides of the vacuum cover and are at the same horizontal height as the visualization part of the low-temperature pulsating heat pipe, forming an optical path passing through the visualization part of the low-temperature pulsating heat pipe. In addition, the visualization optical window and the vacuum cover are sealed by using threads, flanges and sealing rings.

[0031] According to one embodiment of the present invention, the low temperature pulsating heat pipe comprises:

[0032] The condensation section, the insulation section and the evaporation section are mainly formed by bending the capillary tube and arranged from top to bottom along the axial direction of the vacuum cover;

[0033] A first heat transfer copper plate, fixed to the evaporation section by soldering;

[0034] A second heat transfer copper plate is fixed to the condensation section by soldering and connected to the heat conduction bridge;

[0035] Wherein, the insulation section is a glass capillary tube with an infrared reflective material coating on the surface, and the evaporation section and the condensation section are metal capillaries;

[0036] The first heat transfer copper plate and the second heat transfer copper plate are provided with grooves for fixing the evaporation section and the condensation section;

[0037] The thermal insulation section is at least partially arranged to correspond to the visualization optical window.

[0038] Specifically, the low-temperature pulsating heat pipe is formed by bending a capillary tube into at least one loop-type tubular pulsating heat pipe, and the low-temperature pulsating heat pipe includes an evaporation section, an insulation section and a condensation section, wherein the insulation section is a glass tube, and the evaporation section and the condensation section are metal tubes.

[0039] Furthermore, the low-temperature pulsating heat pipe is placed vertically, with the condensation section located at the uppermost end and the evaporation section located at the lowermost end.

[0040] Furthermore, the first heat transfer copper plate and the second heat transfer copper plate have similar structures. Grooves with a width slightly larger than the size of the low-temperature pulsating heat pipe are processed on the plate surface. The first heat transfer copper plate and the second heat transfer copper plate are then welded together with the evaporation section and condensation section of the low-temperature pulsating heat pipe respectively. The gap between the low-temperature pulsating heat pipe and the groove is filled with solder to reduce thermal resistance and ensure good thermal contact.

[0041] It should be noted that in order to avoid the capillary tube from being blocked when bending the tube, which would cause the internal channel of the tube to be blocked, it is necessary to ensure the minimum distance between two adjacent tubes.

[0042] In one embodiment, the evaporation section and the condensation section of the low-temperature pulsating heat pipe are respectively provided with thin film heaters, and the input power can be changed by controlling the current and voltage, wherein the thin film heater of the evaporation section is used to heat the evaporation section of the low-temperature pulsating heat pipe, and the thin film heater of the condensation section is used to control the temperature of the condensation section of the low-temperature pulsating heat pipe.

[0043] In one embodiment, the insulation section of the low-temperature pulsating heat pipe is made of quartz glass or Pyrex glass, and the evaporation section and condensation section are made of copper tube or stainless steel tube. The two ends of the glass capillary are respectively connected to the evaporation section and condensation section of the metal capillary, and a knife-edge flange and indium wire sealing method are adopted. A boss is machined on the glass capillary, and a sealing groove is machined on the knife-edge flange to place the indium wire. The glass is used as the sealing surface, and the flange is tightened with bolts from both sides of the boss to obtain a better sealing effect.

[0044] Furthermore, a spring washer is arranged between the bolt and the knife edge flange to alleviate the expansion and contraction effects of the knife edge flange, the glass capillary, the copper tube and the fastening screw due to different thermal expansion coefficients at low temperatures, thereby further improving the sealing performance and pressure resistance.

[0045] According to one embodiment of the present invention, the two capillary ports at one end of the condensation section are connected to two ports of a three-way joint, and the other port of the three-way joint is connected to the filling system.

[0046] Specifically, two ports will be left after the capillary is bent and formed. The present invention leaves the two ports on one side of the condensation section and provides a three-way joint to connect the two ports of the capillary with the two ports of the three-way joint, and the other port of the three-way joint is connected to the filling system to form a closed low-temperature pulsating heat pipe.

[0047] According to one embodiment of the present invention, the filling system comprises: a buffer tank, a gas tank and a filling pipe;

[0048] One end of the filling pipe is connected to the buffer tank and the gas tank respectively, and the other end is connected to the three-way joint.

[0049] Specifically, the working fluid filling of the low-temperature pulsating heat pipe is achieved through the setting of a buffer tank, a gas tank and a filling pipe.

[0050] According to one embodiment of the present invention, the vacuum pumping system comprises: a first vacuum pump and a second vacuum pump;

[0051] The first vacuum pump is connected to the filling pipe and is used to achieve a high vacuum environment inside the low-temperature pulsating heat pipe;

[0052] The second vacuum pump is connected to the vacuum cover via a vacuum tube, so as to realize a high vacuum environment inside the vacuum cover.

[0053] According to one embodiment of the present invention, the light source is a cold light element, and the acquisition device is a camera;

[0054] Among them, a cover structure with low light transmittance is arranged between the light source, the collection device and the corresponding visualization optical window, so as to reduce the radiation heat dissipation inside the vacuum cover.

[0055] Specifically, the light source and the collection device are arranged outside the vacuum cover, close to the visualization optical window, and adopt the back-side lighting form, that is, the light source and the collection device are symmetrically arranged on both sides of the vacuum cover. A cover structure is also arranged on the path from the light source and the collection device to the visualization optical window, respectively, to reduce the radiation heat leakage of the ambient light to the inside of the vacuum cover.

[0056] In one embodiment, the light source can be a high-power LED strobe cold light source, whose trigger signal uses the synchronous output trigger signal of the camera, or a single-hole xenon lamp medical cold light source, and the camera uses a CCD high-speed camera to capture the working fluid operation status of the low-temperature pulsating heat pipe at a certain frequency.

[0057] In one embodiment, the cover structure can be a black shielding cloth with low light transmittance.

[0058] In one embodiment, the acquisition system further includes a temperature acquisition module, a pressure acquisition module, a data acquisition instrument and a personal computer. The temperature acquisition module is used to acquire the instantaneous temperature value of the low-temperature pulsating heat pipe, and the pressure acquisition module is used to acquire the pressure value of the low-temperature pulsating heat pipe. The measured parameters such as the instantaneous temperature value and pressure value of the low-temperature pulsating heat pipe, as well as the image captured by the camera, are input into the personal computer through the data acquisition instrument for monitoring, storage, and calculation, so as to facilitate the use of later data analysis.

[0059] Furthermore, the temperature acquisition module uses a platinum resistance thermometer, which is placed on the copper plates of the evaporation section and condensation section of the low-temperature pulsating heat pipe and coated with Apiezon N low-temperature vacuum thermal conductive adhesive to ensure good thermal contact between the two. During installation, the lead wire is glued to the surface of the temperature measuring copper plate as a heat sink line.

[0060] According to one embodiment of the present invention, it further comprises an angle adjustment device for adjusting the angle of the vacuum cover;

[0061] The angle adjustment device comprises:

[0062] A frame body, arranged outside the vacuum cover, and used for supporting the vacuum cover;

[0063] A rotating rod, connected to the frame and the vacuum cover respectively, and arranged as the rotation center of the vacuum cover;

[0064] The lifting lug is arranged on the outer side of the vacuum cover.

[0065] Specifically, by setting the angle adjustment device, the tilt angle of the visualized low-temperature pulsating heat pipe experimental device can be adjusted, and the visualized low-temperature pulsating heat pipe experimental device can be adjusted to a required angle.

[0066] In one embodiment, the angle adjustment device further includes an angle disk and a scale arranged on the angle disk. The tilt angle of the visualized low-temperature pulsating heat pipe experimental device can be intuitively judged through the positional relationship between the angle disk and the scale.

[0067] According to one embodiment of the present invention, more than 30 layers of high vacuum multilayer insulation material (MLI) are used to wrap the position where radiation heat leakage needs to be reduced, specifically including: the outer surface of the radiation shield, the second heat transfer copper plate of the low-temperature pulsating heat pipe condensation section and the outer surface of the first heat transfer copper plate of the evaporation section, the refrigerator cold head, and the heat conductive heat bridge.

[0068] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: the experimental device provided by the present invention can observe and record the two-phase flow process of the low-temperature pulsating heat pipe through the corresponding visualization optical window, and its working characteristics can also be continuously measured, analyzed and visualized.

[0069] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0071] Figure 1 It is a schematic diagram of the arrangement of various components in the visualized low-temperature pulsating heat pipe experimental device provided by an embodiment of the present invention;

[0072] Figure 2 It is a first schematic diagram of the assembly relationship of various components in the visualized low-temperature pulsating heat pipe experimental device provided by an embodiment of the present invention;

[0073] Figure 3 It is a second schematic diagram of the assembly relationship of various components in the visualized low-temperature pulsating heat pipe experimental device provided by an embodiment of the present invention;

[0074] Figure 4 It is a third schematic diagram of the assembly relationship of various components in the visualized low-temperature pulsating heat pipe experimental device provided by an embodiment of the present invention;

[0075] Figure 5 It is a schematic diagram of the assembly relationship of a low-temperature pulsating heat pipe, a heat-conducting heat bridge and a three-way joint in a visualized low-temperature pulsating heat pipe experimental device provided by an embodiment of the present invention;

[0076] Figure 6 It is an exploded schematic diagram of the assembly relationship of a low-temperature pulsating heat pipe, a heat-conducting heat bridge and a three-way joint in a visualized low-temperature pulsating heat pipe experimental device provided by an embodiment of the present invention;

[0077] Figure 7 It is a schematic diagram of the assembly relationship between a glass capillary and a metal capillary in a visualized low-temperature pulsating heat pipe experimental device provided by an embodiment of the present invention;

[0078] Figure 8 It is a fourth schematic diagram of the assembly relationship of various components in the visualized low-temperature pulsating heat pipe experimental device provided by an embodiment of the present invention;

[0079] Fig. 9 This is the fifth schematic diagram of the assembly relationship of various components in the visualized low-temperature pulsating heat pipe experimental device provided by an embodiment of the present invention.

[0080] Reference numerals:

[0081] 1: vacuum cover; 101: visualization optical window; 102: flange; 103: lifting rod;

[0082] 2: radiation shield; 201: through hole;

[0083] 3: low temperature pulsating heat pipe; 301: evaporation section; 302: insulation section; 303: condensation section; 304: first heat transfer copper plate; 305: second heat transfer copper plate; 306: groove;

[0084] 4: light source; 5: collection device; 6: refrigerator; 7: thermal bridge; 8: three-way joint; 9: buffer tank; 10: gas tank; 11: filling pipe; 12: first vacuum pump; 13: second vacuum pump; 14: vacuum tube; 15: frame; 16: rotating rod; 17: lifting ear; 18: angle plate; 19: knife-edge flange; 20: boss; 21: film heater; 22: glass fixing part; 23: fixing frame; 24: adjustment plate; 25: adjustment rod.

[0085] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0086] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0087] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0088] Figure 1 This is a schematic diagram of the arrangement of the various components in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the present invention. It is mainly used to show the relative position relationship between the various components of the visual low-temperature pulsating heat pipe 3 experimental device of the present invention. Figure 1 It can be seen that a radiation shield 2 is arranged inside the vacuum cover 1, and a low-temperature pulsating heat pipe 3 is arranged inside the radiation shield 2, wherein the radiation shield 2 is hoisted on the flange 102 of the vacuum cover 1 by a hoisting rod 103, and a refrigerator 6 is also arranged on the flange 102, and the refrigerator 6 is connected to the low-temperature pulsating heat pipe 3 inside the radiation shield 2 through a heat-conducting thermal bridge 7.

[0089] Furthermore, a visualization optical window 101 is symmetrically arranged on the vacuum cover 1 , a through hole 201 is arranged on the radiation protection cover 2 corresponding to the visualization optical window 101 , and the light source 4 and the collection device 5 are respectively located on both sides of the vacuum cover 1 , corresponding to the visualization optical window 101 .

[0090] Furthermore, the second vacuum pump 13 is connected to the inside of the vacuum cover 1 through the vacuum tube 14 to achieve high vacuum inside the vacuum cover 1, and the first vacuum pump 12 is connected to the low-temperature pulsating heat pipe 3 through the filling tube 11 to achieve high vacuum inside the low-temperature pulsating heat pipe 3.

[0091] It should be noted that high vacuum refers to a pressure of 1×10 -3 Below Pa, this value is generally used as a standard in the low-temperature field. When it is lower than this value, the thermal conductivity of the gas is very small and can be ignored.

[0092] Further, from Figure 1 It can be seen that one end of the filling pipe 11 is connected to the low-temperature pulsating heat pipe 3, and the other end is respectively connected to the first vacuum pump 12, the buffer tank 9 and the gas tank 10. Various valve bodies arranged on the filling pipe 11 are omitted here. The arrangement and working principle of the valve body on the filling pipe 11 can refer to the conventional arrangement methods in the field. In order to save space, no excessive elaboration is made here.

[0093] It should be noted that in Figure 1 In the embodiment, a cover structure with low light transmittance is provided between the light source 4 and the corresponding visualization optical window 101, and between the collection device 5 and the corresponding visualization optical window 101. In order to facilitate observation, Figure 1 This part of the structure is omitted in the figure. The low-transmittance cover structure is used to reduce the radiation heat leakage from the room temperature environment to the low-temperature environment inside the vacuum cover 1 through the visualization optical window 101. This part of the setting can be understood as setting a shading structure on the path from the light source 4 and the collection device 5 to the corresponding visualization optical window 101.

[0094] It should also be noted that the present invention can replace low-temperature pulsating heat pipes 3 with different pipe diameters, different filling rates, different inclination angles, different heating amounts, different insulation section 302 lengths, different numbers of loops, and different working fluids, and continuously measure, analyze, and visualize the two-phase flow processes of different low-temperature pulsating heat pipes 3.

[0095] Figure 2 This is the first schematic diagram of the assembly relationship of the various components in the visualized low-temperature pulsating heat pipe experimental device provided by the embodiment of the present invention. It mainly shows the visualized low-temperature pulsating heat pipe 3 experimental device provided by the present invention from the perspective of the axial side view. Figure 2 As can be seen, a frame 15 is provided outside the vacuum cover 1, and an angle plate 18 is provided on the frame 15 to intuitively read the tilt angle of the vacuum cover 1. Two visual optical windows 101 and a lifting lug 17 are symmetrically provided on the vacuum cover 1. A flange 102 is provided on the vacuum cover 1, and a refrigerator 6 and other corresponding auxiliary equipment such as a KF vacuum joint and an aviation plug are provided on the flange 102.

[0096] Figure 3 This is the second schematic diagram of the assembly relationship of the various components in the visualized low-temperature pulsating heat pipe experimental device provided by the embodiment of the present invention. It mainly shows the visualized low-temperature pulsating heat pipe 3 experimental device provided by the present invention from the perspective of the axial side cross-sectional view. Figure 3 As can be seen, a suspended radiation shield 2 is provided inside the vacuum cover 1, and the radiation shield 2 is connected to the flange 102 via a hanging rod 103. The cold head of the refrigerator 6 is connected to the radiation shield 2 and the low-temperature pulsating heat pipe 3 in the radiation shield 2 via a heat-conducting heat bridge 7.

[0097] Furthermore, an angle disc 18 and a rotating rod 16 are provided outside the vacuum cover 1 , and the vacuum cover 1 can rotate around the rotating rod 16 . The angle disc 18 is used to observe the rotation angle of the vacuum cover 1 .

[0098] It should be noted that a bearing, a bearing seat and the like are also provided between the rotating rod 16 and the vacuum cover 1. In order to save space, they are not described in detail here. The specific configuration can refer to the conventional design in the art.

[0099] Further, from Figure 2 It can be seen that the height of the low-temperature pulsating heat pipe 3 corresponds to the visualization optical window 101 , wherein the low-temperature pulsating heat pipe 3 includes a transparent tube with one end being visualized, and this part is within the visualization range of the visualization optical window 101 .

[0100] Figure 4 This is the third schematic diagram of the assembly relationship of the various components in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the present invention. It is mainly used to show the positional relationship between the low-temperature pulsating heat pipe 3, the heat bridge 7, the filling pipe 11, the refrigerator 6, the rotating rod 16 and the angle plate 18. Figure 4 The above is omitted. Figure 4 It can be seen from the figure that the heat-conducting heat bridge 7 connects the cold head of the refrigerator 6 and the low-temperature pulsating heat pipe 3 respectively.

[0101] Furthermore, the filling pipe 11 penetrates from the outside of the flange 102 to the low-temperature pulsating heat pipe 3 to achieve connection with the low-temperature pulsating heat pipe 3.

[0102] Figure 5 This is a schematic diagram of the assembly relationship of the low-temperature pulsating heat pipe 3, the heat-conducting heat bridge 7 and the three-way joint 8 in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the present invention. It is mainly used to show the specific structure of the low-temperature pulsating heat pipe 3 and the connection relationship between the low-temperature pulsating heat pipe 3 and the heat-conducting heat bridge 7. Figure 5 As can be seen from the figure, the low-temperature pulsating heat pipe 3 includes an evaporation section 301, an insulation section 302, a condensation section 303, a first heat transfer copper plate 304, and a second heat transfer copper plate 305. The evaporation section 301 and the first heat transfer copper plate 304 are fixed by soldering and are vertically arranged at the bottom of the low-temperature pulsating heat pipe 3. The condensation section 303 and the second heat transfer copper plate 305 are fixed by soldering and are vertically arranged at the top of the low-temperature pulsating heat pipe 3. The insulation section 302 is arranged between the evaporation section 301 and the condensation section 303.

[0103] Furthermore, the connection between the evaporation section 301 and the insulation section 302 , and the connection between the condensation section 303 and the insulation section 302 , is achieved through a knife-edge flange 19 .

[0104] Furthermore, the low-temperature pulsating heat pipe 3 is at least one loop-type tubular pulsating heat pipe formed by bending a capillary tube, wherein the insulation section 302 is a glass tube, and the evaporation section 301 and the condensation section 303 are metal tubes.

[0105] Furthermore, since the low-temperature pulsating heat pipe 3 is formed by bending a capillary tube, there are naturally two free ports. In the present invention, the two free ports are arranged on one side of the condensing section 303 and connected through a three-way joint 8. The two ports of the three-way joint 8 are respectively connected to the two free ports of the low-temperature pulsating heat pipe 3, and the other port of the three-way joint 8 is connected to the filling pipe 11 to realize the filling of the working medium in the low-temperature pulsating heat pipe 3.

[0106] Figure 6 This is an exploded schematic diagram of the assembly relationship of the low-temperature pulsating heat pipe 3, the heat-conducting heat bridge 7 and the three-way joint 8 in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the present invention. It mainly displays the specific structure of the low-temperature pulsating heat pipe 3 and the connection relationship between the low-temperature pulsating heat pipe 3 and the heat-conducting heat bridge 7. Figure 6 It can be seen that the first heat transfer copper plate 304 and the second heat transfer copper plate 305 of the low-temperature pulsating heat pipe 3 are respectively provided with grooves 306, and the grooves 306 are used to fix the evaporation section 301 and the condensation section 303. In order to ensure good thermal contact and reduce thermal resistance, the gap between the low-temperature pulsating heat pipe 3 and the grooves 306 is filled with solder, and then the first heat transfer copper plate 304 and the second heat transfer copper plate 305 are respectively welded to the evaporation section 301 and the condensation section 303 of the low-temperature pulsating heat pipe 3.

[0107] It should be noted that Figure 6 The heat pipe also includes a glass fixing member 22 connected to the first heat transfer copper plate 304 and the second heat transfer copper plate 305 respectively. The glass fixing member 22 is made of G10 glass fiber reinforced plastic, which can withstand great pressure without being damaged and deformed, and has a low thermal conductivity. The insulation section 302 of the low-temperature pulsating heat pipe is made of glass material, which is easily broken by force. The glass fixing member 22 made of G10 glass fiber reinforced plastic is used to connect the first heat transfer copper plate 304 and the second heat transfer copper plate 305, thereby fixing the low-temperature pulsating heat pipe and preventing the glass from breaking.

[0108] Figure 7 It is a schematic diagram of the assembly relationship between the glass capillary and the metal capillary in the visualized low-temperature pulsating heat pipe experimental device provided in an embodiment of the present invention. Figure 7 The section is shown in FIG. 1 , and other parts are omitted here, but it should not be understood that it is unclear or inaccurately expressed here. The knife edge flange 19 here is Figures 3 to 6 There are expressions in Figure 7 Only one of the knife-edge flanges 19 is subjected to the cross-section processing, and the settings of the other knife-edge flanges 19 are also the same.

[0109] Further, from Figure 7 It can be seen that in the cross-sectional view of the knife-edge flange 19, the evaporation section 301 and the insulation section 302 are against each other, wherein the mating portion of the insulation section 302 and the evaporation section 301 is provided with a boss 20, a sealing groove is machined on the knife-edge flange 19 to place the indium wire, and the boss 20 and the knife-edge flange 19 are pressed tightly with bolts to achieve the sealing of the insulation section 302 and the evaporation section 301. The same is true for the connection relationship between the insulation section 302 and the condensation section 303.

[0110] Figure 8 and Fig. 9 The fourth and fifth schematic diagrams are the assembly relationships of the components in the visualized low-temperature pulsating heat pipe experimental device provided by the embodiment of the present invention. The visualized low-temperature pulsating heat pipe 3 experimental device provided by the present invention is mainly shown from the perspective of the axial side view. Figure 8 and Fig. 9 As can be seen, a frame 15 is provided outside the vacuum cover 1, and an angle plate 18 is provided on the frame 15 to intuitively read the tilt angle of the vacuum cover 1. Visual optical windows 101 and hanging ears 17 are symmetrically provided on the vacuum cover 1. A flange 102 is provided on the vacuum cover 1, and a refrigerator 6 and other corresponding auxiliary equipment such as a KF vacuum joint and an aviation plug are provided on the flange 102.

[0111] Specifically, in order to adapt to different observation ranges, a lifting device can be provided between the visualization optical window 101 and the radiation shield 2. The lifting device includes two symmetrically arranged adjustment plates 24, and a fixing frame 23 and an adjustment rod 25 connected to the adjustment plates 24. The adjustment rod 25 is used to adjust the height of the adjustment plates 24 in the vacuum shield 1, thereby adjusting the visualization range of the visualization optical window 101.

[0112] It should be noted that the fixing frame 23 includes an outer frame and an inner frame, and G10 glass fiber reinforced plastics arranged between the outer frame and the inner frame. The G10 glass fiber reinforced plastics are used to prevent heat insulation and reduce heat conduction.

[0113] Furthermore, the adjustment plate 24 is a copper plate, and the adjustment plate 24 is covered with a high vacuum multi-layer insulation material. A necessary observation hole is reserved according to the demand. The area of ​​the observation hole is smaller than the area of ​​the visualization optical window 101. The observation hole is moved up and down by the adjustment rod 25 to realize the observation and shooting of different positions of the insulation section 302 of the low-temperature pulsating heat pipe 3. At the same time, the heat radiation introduced by most of the windows is blocked by the copper plate, realizing visualization while minimizing radiation heat leakage. When the observation hole is not opened on the adjustment plate 24, it is equivalent to a conventional low-temperature pulsating heat pipe test bench, and the conventional thermal performance experiment of the low-temperature pulsating heat pipe can be carried out.

[0114] It should also be noted that the adjustment of the adjustment plate 24 by the adjustment rod 25 can be automatic or manual, and the connection between the adjustment rod 25 and the outer side of the flange 102 can be provided with a cylinder or a liquid cylinder or a manual adjustment device.

[0115] In general, the experimental device provided by the present invention can observe and record the two-phase flow process of the low-temperature pulsating heat pipe 3 through the corresponding visualization optical window 101, and its working characteristics can also be continuously measured, analyzed and visualized. It also solves the problem that the visualization window causes large radiation heat leakage, making it difficult to maintain a low-temperature environment. It also solves the structural strength and working fluid leakage problems caused by the large difference in thermal expansion coefficient between the visualization element and the metal connection material at low temperature, as well as the problem that the visualization pipe section of the low-temperature pulsating heat pipe 3 is not strong enough and easy to break.

[0116] Furthermore, the present invention adopts a vacuum multi-layer insulation method with a radiation protection cover 2, and only leaves necessary optical paths when arranging the radiation protection cover 2 and the multi-layer insulation material; an infrared reflective material coating is plated on the surface of the glass capillary of the visualization optical window 101 and the insulation section 302 of the low-temperature pulsating heat pipe 3; a low-transmittance cover structure is used between the light source 4 and the camera and the visualization optical window 101 respectively; and at the same time, a large-capacity refrigerator 6 is used to take away the radiation leakage heat introduced by the visualization optical window 101, and other measures are taken to solve the problem of large low-temperature visualization radiation heat leakage.

[0117] Furthermore, by using the experimental platform provided by the present invention, the working flow state of the low-temperature pulsating heat pipe 3 can be observed and recorded through the corresponding visualization optical window 101, and the operating state and operating parameters of the working fluid can be monitored simultaneously, realizing the visualization of the two-phase flow process of the low-temperature pulsating heat pipe 3. It can be used to study the thermo-hydrodynamic characteristics, gas-liquid phase change and flow pattern transformation of the working fluid of the low-temperature pulsating heat pipe 3, analyze the influence of bubble growth on the operation and oscillation characteristics of the system, and the influence of various parameters such as pipe diameter, filling rate, inclination angle, heating amount, length of the insulation section 302, number of loops, etc. on the fluid movement and heat transfer of the low-temperature pulsating heat pipe 3.

[0118] Furthermore, the present invention uses a low-temperature refrigerator 6 as a cold source, which can provide cooling for the low-temperature pulsating heat pipe 3 for studying low-temperature working fluids in a wider working temperature range. By adjusting the working fluid filling rate and / or adjusting the condenser temperature of the low-temperature pulsating heat pipe 3, the saturated pressure and temperature of the low-temperature pulsating heat pipe 3 during operation can be adjusted and changed, and research under different working conditions can be carried out.

[0119] In addition, compared with other low-temperature visualization methods such as endoscope and electrical capacitance tomography, the visualization method of the present invention has the advantages of simple structure, easy operation, intuitive imaging and high reliability.

[0120] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0121] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0122] In a specific embodiment, Figure 1 As shown, the present invention provides a visualized low-temperature pulsating heat pipe experimental device, comprising: a visualized low-temperature insulation system, a low-temperature pulsating heat pipe 3, a filling system, a vacuum system and a collection system; the visualized low-temperature insulation system comprises a vacuum cover 1, and a radiation protection cover 2 arranged in the vacuum cover 1, and a side wall of the vacuum cover 1 is provided with a visualized optical window 101; the low-temperature pulsating heat pipe 3 is arranged in a chamber surrounded by the radiation protection cover 2; the filling system is arranged outside the vacuum cover 1, and is connected to the low-temperature pulsating heat pipe 3 through a pipeline extending into the vacuum cover 1, and is used for filling the low-temperature pulsating heat pipe 3 with a working medium; the vacuum system is respectively connected to the vacuum cover 1 and the low-temperature pulsating heat pipe 3, and is used for realizing a high vacuum environment in the vacuum cover 1 and the low-temperature pulsating heat pipe 3; the collection system comprises a light source 4 and a collection device 5 respectively arranged on both sides of the vacuum cover 1 corresponding to the visualized optical window 101.

[0123] In one embodiment, two visualization optical windows 101 are arranged on both sides of the vacuum cover 1, facing the low-temperature pulsating heat pipe 3, at the same horizontal height, forming an optical path through the insulation section 302 of the low-temperature pulsating heat pipe 3. The visualization optical window 101 is sealed by a threaded flange and an O-ring. A stainless steel round tube with an external thread is connected to the vacuum cover 1 by welding. A concave platform and an O-ring groove are processed on the top of the stainless steel round tube for placing the O-ring and quartz glass. The quartz glass is locked and sealed by a threaded flange. At the same time, a 0.5 mm thick polytetrafluoroethylene annular sheet is installed between the quartz glass and the threaded flange to prevent the quartz glass from being damaged when the quartz glass is tightened and sealed, thereby affecting the sealing effect. The threaded connection makes the device detachable, which is convenient for replacing transparent glass and prolongs the service life of the device.

[0124] In a specific embodiment, Figures 1 to 4 As shown, the present invention provides a visualized low-temperature pulsating heat pipe experimental device, a flange 102 is arranged on the upper part of the vacuum cover 1, a refrigerator 6 is arranged on the flange 102, a cold head of the refrigerator 6 is connected to the low-temperature pulsating heat pipe 3 through a heat-conducting heat bridge 7, and the heat-conducting heat bridge 7 is connected to the radiation protection cover 2.

[0125] Specifically, the refrigerator 6, the low-temperature pulsating heat pipe 3 and the radiation shield 2 are connected through the heat-conducting heat bridge 7 to conduct the cooling capacity of the refrigerator to keep the temperature of the low-temperature pulsating heat pipe 3 and the radiation shield 2 in the low temperature zone.

[0126] It should be noted that the contact surfaces between the low-temperature pulsating heat pipe 3, the refrigerator 6, the radiation shield 2 and the thermal bridge 7 need to be polished smooth, and provided with indium sheets and coated with Apiezon N vacuum thermal conductive adhesive to reduce contact thermal resistance and enhance thermal conductivity.

[0127] In one embodiment, the vacuum cover 1 is a cylindrical structure made of stainless steel, the lower part is sealed by welding, the upper part is detachably connected to the flange 102, and the vacuum cover 1 and the flange 102 are sealed by a sealing ring and vacuum sealant.

[0128] In one embodiment, the radiation shield 2 is a cylindrical structure made of copper or aluminum.

[0129] In one embodiment, the refrigerator 6 may be a pulse tube refrigerator 6 , a Stirling refrigerator 6 , a GM refrigerator 6 or other low temperature refrigerators 6 , and is fixedly connected to the flange 102 .

[0130] In one embodiment, the heat-conducting heat bridge 7 is made of copper or aluminum, and is provided with threaded holes for connecting with the cold head of the refrigerator 6 and the low-temperature pulsating heat pipe 3 .

[0131] In one embodiment, Figures 1 to 4 As shown, the visualized low-temperature insulation system also includes: a hanging rod 103, which is respectively connected to the radiation shield 2 and the flange 102; a through hole 201, which is arranged on the radiation shield 2; wherein the hanging rod 103 hangs the radiation shield 2 into the through hole 201 and corresponds to the visualized optical window 101.

[0132] Specifically, the radiation shield 2 is hoisted in the vacuum shield 1 by the hoisting rod 103 . This arrangement further reduces the stress on the cold head of the refrigerator 6 , and prevents stress deformation from affecting the operation of the refrigerator 6 .

[0133] In one embodiment, in order to increase the strength of the hanging rod 103, the hanging rod 103 of this embodiment is made of stainless steel.

[0134] In one embodiment, in order to reduce the solid conduction heat leakage of the lifting rod 103, the lifting rod 103 of this embodiment is set as a thin-walled hollow structure, and air holes are opened on the tube wall. During the vacuuming process, the gas in the tube wall is extracted to eliminate the problem of gas heat leakage.

[0135] In one embodiment, Figures 1 to 4 As shown, the surface of the visualization optical window 101 is coated with an infrared reflective material coating.

[0136] Specifically, by coating the surface of the visualization optical window 101 with a coating made of infrared reflective material, the radiation heat leakage from the ambient light to the inside of the vacuum cover 1 is reduced.

[0137] It should be noted that the present embodiment adopts a high vacuum multi-layer insulation method to achieve insulation in a low-temperature environment. It is necessary to reduce convection, heat conduction, and radiation, and reduce heat leakage from three aspects. In conjunction with a low-temperature refrigerator to achieve low temperature, high vacuum only reduces air convection, and a radiation shield 2 and multi-layer insulation composite materials are also required to reduce heat radiation, and the cross-sectional area of ​​the lifting rod 103 is reduced to reduce heat conduction.

[0138] In one embodiment, two visualization optical windows 101 are symmetrically arranged on both sides of the vacuum cover 1 and are at the same horizontal height as the visualization part of the low-temperature pulsating heat pipe 3, forming an optical path passing through the visualization part of the low-temperature pulsating heat pipe 3. In addition, the visualization optical window 101 and the vacuum cover 1 are sealed by using threads, flanges and sealing rings.

[0139] In a specific embodiment, Figures 1 to 7 As shown, the present invention provides a visualized low-temperature pulsating heat pipe experimental device, the low-temperature pulsating heat pipe 3 comprises: a condensation section 303, an insulation section 302 and an evaporation section 301 which are mainly formed by bending a capillary and arranged from top to bottom along the axial direction of the vacuum cover 1; a first heat transfer copper plate 304, used to fix the evaporation section 301; a second heat transfer copper plate 305, used to fix the condensation section 303, and connected to the heat-conducting heat bridge 7; wherein the insulation section 302 is a glass capillary with an infrared reflective material coating on the surface, and the evaporation section 301 and the condensation section 303 are metal capillaries; a groove 306 for fixing the evaporation section 301 and the condensation section 303 is provided on the first heat transfer copper plate 304 and the second heat transfer copper plate 305; the insulation section 302 is at least partially arranged corresponding to the visualized optical window 101.

[0140] Specifically, the low-temperature pulsating heat pipe 3 is formed by bending a capillary tube into at least one loop-type tubular pulsating heat pipe, and the low-temperature pulsating heat pipe 3 includes an evaporation section 301, an insulation section 302 and a condensation section 303, wherein the insulation section 302 is a glass tube, and the evaporation section 301 and the condensation section 303 are metal tubes.

[0141] Furthermore, the low-temperature pulsating heat pipe 3 is placed vertically, with the condensation section 303 located at the uppermost end and the evaporation section 301 located at the lowermost end.

[0142] Furthermore, the first heat transfer copper plate 304 and the second heat transfer copper plate 305 have similar structures, and both are processed on the plate surface to form a groove 306 with a width slightly larger than the size of the low-temperature pulsating heat pipe 3, and then the first heat transfer copper plate 304 and the second heat transfer copper plate 305 are respectively welded to the evaporation section 301 and the condensation section 303 of the low-temperature pulsating heat pipe 3, and the gap between the low-temperature pulsating heat pipe 3 and the groove 306 is filled with solder to reduce thermal resistance and ensure good thermal contact.

[0143] It should be noted that in order to avoid the capillary tube from being blocked when bending the tube, which would cause the internal channel of the tube to be blocked, it is necessary to ensure the minimum distance between two adjacent tubes.

[0144] In one embodiment, the evaporation section 301 and the condensation section 303 of the low-temperature pulsating heat pipe 3 are respectively provided with a thin film heater 21, and the input power can be changed by controlling the current and voltage, wherein the thin film heater 21 of the evaporation section 301 is used to heat the evaporation section 301 of the low-temperature pulsating heat pipe 3, and the thin film heater 21 of the condensation section 303 is used to control the temperature of the condensation section 303 of the low-temperature pulsating heat pipe 3.

[0145] In one embodiment, Figure 7 As shown, the insulation section 302 of the low-temperature pulsating heat pipe 3 is made of quartz glass or Pyrex glass, and the evaporation section 301 and the condensation section 303 are made of copper tubes. The two ends of the glass capillary are respectively connected to the evaporation section 301 and the condensation section 303 of the metal capillary, and the knife-edge flange 19 and the indium wire are used for sealing. The boss 20 is processed on the glass capillary, and the sealing groove is processed on the knife-edge flange 19 to place the indium wire. The glass is used as the sealing surface, and the flange is tightened from both sides of the boss 20 with bolts to obtain a better sealing effect.

[0146] It should be noted that the inner diameters of the glass capillary and the metal capillary must satisfy the following formula:

[0147]

[0148] Among them, σ is the surface tension of the working fluid;

[0149] ρ L is the density of the liquid working medium at saturation temperature;

[0150] ρ V is the density of the gaseous working fluid at saturation temperature;

[0151] g is the acceleration due to gravity.

[0152] In this example, the working fluid is nitrogen, and the inner diameter is between 0.5 and 2 mm.

[0153] The glass capillary is made of high-precision glass tube that can withstand high pressure. The pressure resistance of the glass capillary and the metal capillary is 0.5MPa.

[0154] Furthermore, a spring washer is arranged between the bolt and the knife edge flange 19. The spring washer can alleviate the expansion and contraction effects of the knife edge flange 19, the glass capillary, the copper tube and the fastening screws due to different thermal expansion coefficients at low temperatures, thereby further improving the sealing performance and pressure resistance.

[0155] It should be noted that the knife-edge flange 19 is used in combination with the indium wire seal to solve the problem of sealing difficulty of the low-temperature visualization system at low temperatures. The spring washer is used to alleviate the influence of expansion and contraction caused by different thermal expansion coefficients at low temperatures between the knife-edge flange 19, the glass capillary, the copper tube and the fastening screws, thereby further improving the sealing performance and pressure resistance.

[0156] It should also be noted that a G10 composite material is provided between the evaporation section 301 and the condensation section 303 of the low-temperature pulsating heat pipe 3 to fix the connection, so as to improve the overall strength and prevent the quartz glass tube of the insulation section 302 from breaking. The use of G10 composite material to reinforce the low-temperature pulsating heat pipe 3 solves the problem of insufficient strength and fragility of the visualization glass element.

[0157] In one embodiment, Figure 5 and Figure 6 As shown, the two capillary ports at one end of the condensation section 303 are connected to the two ports of the three-way connector 8, and the other port of the three-way connector 8 is connected to the filling system.

[0158] Specifically, two ports will be left after the capillary is bent and formed. The present invention leaves the two ports on one side of the condensation section 303, and provides a three-way joint 8, so that the two ports of the capillary are connected to the two ports of the three-way joint 8, and the other port of the three-way joint 8 is connected to the filling system to form a closed low-temperature pulsating heat pipe 3.

[0159] In a specific embodiment, Figures 1 to 4 As shown, the present invention provides a visualized low-temperature pulsating heat pipe experimental device, and the filling system includes: a buffer tank 9, a gas tank 10 and a filling pipe 11; one end of the filling pipe 11 is connected to the buffer tank 9 and the gas tank 10 respectively, and the other end is connected to the three-way joint 8.

[0160] Specifically, by providing the buffer tank 9 , the gas tank 10 and the filling pipe 11 , the filling of the working medium into the low-temperature pulsating heat pipe 3 is achieved.

[0161] In one embodiment, Figure 1As shown, the vacuum system includes: a first vacuum pump 12 and a second vacuum pump 13; the first vacuum pump 12 is connected to the filling pipe 11, and is used to achieve a high vacuum environment inside the low-temperature pulsating heat pipe 3; the second vacuum pump 13 is connected to the vacuum cover 1 through a vacuum pipe 14, and is used to achieve a high vacuum environment inside the vacuum cover 1.

[0162] Specifically, by providing the first vacuum pump 12 and the second vacuum pump 13 , a high vacuum environment is achieved in the low-temperature pulsating heat pipe 3 and the vacuum cover 1 .

[0163] In one embodiment, Figure 1 As shown, the light source 4 is a cold light element, and the acquisition device 5 is a camera; wherein, a cover structure with low light transmittance is arranged between the light source 4 and the acquisition device 5 and the corresponding visualization optical window 101, so as to reduce the radiation heat dissipation inside the vacuum cover 1.

[0164] Specifically, the light source 4 and the collection device 5 are arranged outside the vacuum cover 1, close to the visualization optical window 101, and adopt the back-side lighting form, that is, the light source 4 and the collection device 5 are symmetrically arranged on both sides of the vacuum cover 1. A cover structure is also arranged on the path from the light source 4 and the collection device 5 to the visualization optical window 101, respectively, to reduce the radiation heat leakage of the ambient light to the inside of the vacuum cover 1.

[0165] In one embodiment, the light source 4 can adopt a high-power LED strobe cold light source 4, whose trigger signal adopts the synchronous output trigger signal of the camera, or adopt a single-hole xenon lamp medical cold light source 4, and the camera is used to shoot the working fluid operation status of the low-temperature pulsating heat pipe 3 at a certain frequency.

[0166] In one embodiment, the cover structure can be a black shielding cloth with low light transmittance.

[0167] In one embodiment, the acquisition system further includes a temperature acquisition module, a pressure acquisition module, a data acquisition instrument and a personal computer. The temperature acquisition module is used to acquire the instantaneous temperature value of the low-temperature pulsating heat pipe 3, and the pressure acquisition module is used to acquire the pressure value of the low-temperature pulsating heat pipe 3 and the buffer tank 9. The measured parameters such as the instantaneous temperature value and pressure value of the low-temperature pulsating heat pipe 3, and the image captured by the camera are input into the personal computer through the data acquisition instrument for monitoring, storage, and calculation, so as to facilitate the use of later data analysis.

[0168] It should be noted that the pressure acquisition module includes pressure sensors connected to the buffer tank 9 and the filling pipe 11 respectively, and is used to calculate the filling rate and monitor the working fluid pressure of the measuring point.

[0169] Specifically, the filling rate of the low-temperature pulsating heat pipe 3 is calculated according to the following formula:

[0170]

[0171] Wherein, V1 is the volume inside the buffer tank 9;

[0172] V PHP is the total volume inside the pulsating heat pipe;

[0173] P1 is the internal pressure of the buffer tank 9 before the cooling process begins;

[0174] P 1* The internal pressure of the buffer tank 9 after the cooling process is completed;

[0175] ρ L and ρ V are the densities of the liquid and gaseous working fluids at saturation temperatures respectively;

[0176] T1 is room temperature;

[0177] R is the ideal gas constant.

[0178] Furthermore, the temperature acquisition module uses a platinum resistance thermometer, which is placed on the copper plates of the evaporation section 301 and the condensation section 303 of the low-temperature pulsating heat pipe 3 and coated with Apiezon N low-temperature vacuum thermal conductive adhesive to ensure good thermal contact between the two. During installation, the lead wire is glued to the surface of the temperature measuring copper plate as a heat sink wire.

[0179] In a specific embodiment, Figures 2 to 4 As shown, the present invention provides a visualized low-temperature pulsating heat pipe experimental device. In order to study the influence of the tilt angle on the pulsating heat pipe, it is necessary to change the placement angle of the pulsating heat pipe in the experiment. For this purpose, a set of angle devices that can change the tilt angle is designed. The angle adjustment device includes: a frame 15, which is arranged outside the vacuum cover 1 and is used to support the vacuum cover 1; a rotating rod 16, which is respectively connected to the frame 15 and the vacuum cover 1 and is arranged as the rotation center of the vacuum cover 1; and a lifting ear 17, which is arranged outside the vacuum cover 1.

[0180] Specifically, by setting the angle adjustment device, the tilt angle of the visualized low-temperature pulsating heat pipe 3 experimental device can be adjusted, and the visualized low-temperature pulsating heat pipe 3 experimental device can be adjusted to a desired angle.

[0181] In one embodiment, the angle adjustment device further includes an angle disk 18 and a scale arranged on the angle disk 18. The tilt angle of the visualized low-temperature pulsating heat pipe 3 experimental device can be intuitively judged through the positional relationship between the angle disk 18 and the scale.

[0182] In one application scenario, more than 30 layers of high vacuum multilayer insulation material (MLI) are used to wrap the locations where radiation heat leakage needs to be reduced, specifically including: the outer surface of the radiation shield 2, the second heat transfer copper plate 305 of the condensation section 303 of the low-temperature pulsating heat pipe 3 and the outer surface of the first heat transfer copper plate 304 of the evaporation section 301, the cold head of the refrigerator 6, and the heat conductive heat bridge 7.

[0183] In this application scenario, the low-temperature insulation multilayer composite material produced by Hangzhou Fujita Special Materials Co., Ltd. is used. The product uses a double-sided aluminum-plated polyester film as a reflective screen, and the spacing material is a chemical fiber film. In order to reduce the impact of the high vacuum multilayer insulation material (MLI) on the vacuum degree during the experiment, it is necessary to perform drying pretreatment before use to remove moisture, grease and other debris in the multilayer material. Holes are punched on the multilayer material to facilitate air extraction, and the number of holes should not be too large, otherwise it will reduce the effective radiation area and affect the insulation performance.

[0184] Furthermore, openings are provided on the radiation shield 2 and the multi-layer aluminum-plated polyester film corresponding to the visualization optical window 101 area to ensure that the light from the light source 4 is smoothly projected to the low-temperature pulsating heat pipe 3 and enable the high-speed camera to smoothly record the gas-liquid flow process inside the low-temperature pulsating heat pipe 3.

[0185] In one embodiment, Figure 8 and Fig. 9 As shown, a visual low-temperature pulsating heat pipe experimental device provided in this embodiment has a frame 15 disposed outside the vacuum cover 1, and an angle plate 18 is disposed on the frame 15 to intuitively read the tilt angle of the vacuum cover 1. Visual optical windows 101 and hanging ears 17 are symmetrically disposed on the vacuum cover 1. A flange 102 is disposed on the vacuum cover 1, and a refrigerator 6 and other corresponding auxiliary equipment such as a KF vacuum joint and an aviation plug are disposed on the flange 102.

[0186] Specifically, in order to adapt to different observation ranges, a lifting device can be provided between the visualization optical window 101 and the radiation shield 2. The lifting device includes two symmetrically arranged adjustment plates 24, and a fixing frame 23 and an adjustment rod 25 connected to the adjustment plates 24. The adjustment rod 25 is used to adjust the height of the adjustment plates 24 in the vacuum shield 1, thereby adjusting the visualization range of the visualization optical window 101.

[0187] It should be noted that the fixing frame 23 includes an outer frame and an inner frame, and G10 glass fiber reinforced plastics arranged between the outer frame and the inner frame. The G10 glass fiber reinforced plastics are used to prevent heat insulation and reduce heat conduction.

[0188] Furthermore, the adjustment plate 24 is a copper plate, and the adjustment plate 24 is covered with a high vacuum multi-layer insulation material. A necessary observation hole is reserved according to the demand. The area of ​​the observation hole is smaller than the area of ​​the visualization optical window 101. The observation hole is moved up and down by the adjustment rod 25 to realize the observation and shooting of different positions of the insulation section 302 of the low-temperature pulsating heat pipe 3. At the same time, the heat radiation introduced by most of the windows is blocked by the copper plate, realizing visualization while minimizing radiation heat leakage. When the observation hole is not opened on the adjustment plate 24, it is equivalent to a conventional low-temperature pulsating heat pipe test bench, and the conventional thermal performance experiment of the low-temperature pulsating heat pipe can be carried out.

[0189] It should also be noted that the adjustment of the adjustment plate 24 by the adjustment rod 25 can be automatic or manual, and the connection between the adjustment rod 25 and the outer side of the flange 102 can be provided with a cylinder or a liquid cylinder or a manual adjustment device.

[0190] In an application scenario, this application field provides an experimental process of a visualized low-temperature pulsating heat pipe experimental device of the present invention, which is as follows:

[0191] S1. Preparation process: The components of the visualization device are Figure 1 Before the experiment, the device was connected and assembled. A helium mass spectrometer leak detector was used to perform vacuum leak detection on the device, including the vacuum cover 1, the low-temperature pulsating heat pipe 3, the filling pipe 11 and the buffer tank 9. After ensuring that the vacuum degree at room temperature meets the experimental requirements, the first vacuum pump 12 was turned on to evacuate the vacuum cover 1 to 1×10 -4 Pa.

[0192] S2. Purging and purification process: open the valves of the buffer tank 9 and the first vacuum pump 12, close the valve of the gas tank 10, and start the second vacuum pump 13 to evacuate the low-temperature pulsating heat pipe 3, the buffer tank 9 and the filling pipe 11; then open the valves of the buffer tank 9 and the gas tank 10, and close the valve of the first vacuum pump 12. After the valve of the gas tank 10 is opened, 99.999% high-purity nitrogen is filled into the low-temperature pulsating heat pipe 3, the filling pipe 11 and the buffer tank 9 to about 200 kPa. Repeat the above process 5 times to complete the purging and purification process.

[0193] S3. Filling process: According to the calculation formula of the filling rate, the required initial filling pressure is estimated, and then the valves of the valve buffer tank 9 and the gas tank 10 are opened and the valve of the first vacuum pump 12 is closed. The valve of the gas tank 10 is opened to fill nitrogen until the pressure sensor shows that the predetermined pressure has been reached, and then the valve of the gas tank 10 is closed, and the refrigerator 6 is started to cool down. In this process, when the pressure sensor shows that the predetermined pressure has been reached, the valve of the valve buffer tank 9 is closed, so that both the buffer tank 9 and the gas tank 10 are closed. After the cooling process is completed and the temperature of the low-temperature pulsating heat pipe 3 is stabilized, the filling rate is accurately calculated again.

[0194] S4. Experimental process: adjust the angle device, place the pulsating heat pipe at the specified tilt angle, and conduct the performance-related experiment of the low-temperature pulsating heat pipe 3. The dynamic temperature and pressure data of the measuring point are collected through the control and data acquisition system, and the operation of the gas-liquid plug of the visualized pipe section is photographed at a certain frequency by a high-speed camera.

[0195] S5. Data analysis: After the experiment, the experimental results are calculated and analyzed based on the data collected by the control and data acquisition system combined with the operation of the gas-liquid plug, gas-liquid phase change and flow pattern transition captured by the high-speed camera.

[0196] In step S4, the experimental scheme of the low temperature pulsating heat pipe 3 may be:

[0197] 1. By adjusting the working fluid filling rate and / or adjusting the condenser temperature of the low-temperature pulsating heat pipe 3, the saturated pressure and temperature of the low-temperature pulsating heat pipe 3 during operation can be adjusted and changed, and research under different working conditions can be carried out. Observe the initial distribution of gas and liquid in the low-temperature pulsating heat pipe 3 at different filling rates and the working conditions after startup.

[0198] 2. The heating power of the evaporation section 301 is increased step by step. According to the data collected by the control and data acquisition system and the operation of the gas-liquid plug captured by the high-speed camera, the influence of the heating power on the heat transfer performance and thermo-hydrodynamic characteristics, gas-liquid phase change and flow pattern conversion of the low-temperature pulsating heat pipe 3 is studied.

[0199] 3. By inputting instantaneous heating power, the quenching condition of the superconducting magnet is simulated and the transient thermal characteristics of the low-temperature pulsating heat pipe 3 are studied.

[0200] 4. By adjusting the angle of the low-temperature pulsating heat pipe 3, the influence of gravity on the heat transfer performance and working fluid flow of the low-temperature pulsating heat pipe 3 is studied.

[0201] 5. Compare low-temperature pulsating heat pipes 3 with different pipe diameters, insulation section 302 lengths or loop numbers, and low-temperature pulsating heat pipes 3 with different geometric parameters to optimize the design of the pulsating heat pipes.

[0202] 6. In the visualization experiment, pay close attention to the various gas-liquid phase change forms, flow pattern changes, flow direction and pulsation frequency occurring in the low-temperature pulsating heat pipe 3, and analyze the working fluid flow characteristics and thermo-hydrodynamic characteristics.

[0203] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0204] The above embodiments are only used to illustrate the present invention, but not to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that various combinations, modifications or equivalent substitutions of the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and should be included in the scope of the claims of the present invention.

Claims

1. A visual low-temperature pulsating heat pipe experimental device, characterized in that: include: Visualize cryogenic insulation system, cryogenic pulsating heat pipe, charging system, vacuum system and acquisition system; The visualized low-temperature insulation system comprises a vacuum cover and a radiation protection cover arranged in the vacuum cover, and a visualized optical window is arranged on the side wall of the vacuum cover; the low-temperature pulsating heat pipe is arranged in a chamber surrounded by the radiation protection cover; the filling system is arranged outside the vacuum cover, and is connected to the low-temperature pulsating heat pipe through a pipeline extending into the vacuum cover, and is used to fill the low-temperature pulsating heat pipe with working fluid; the vacuum pumping system is respectively connected to the vacuum cover and the low-temperature pulsating heat pipe; the collection system comprises a light source and a collection device respectively arranged on both sides of the vacuum cover corresponding to the visualized optical window; A flange is provided on the upper part of the vacuum cover, a refrigerator is provided on the flange, a cold head of the refrigerator is connected to the low-temperature pulsating heat pipe via a heat-conducting heat bridge, and the heat-conducting heat bridge is connected to the radiation shield; The low-temperature pulsating heat pipe comprises: a condensation section, an insulation section and an evaporation section which are mainly formed by bending a capillary tube and arranged from top to bottom along the axial direction of the vacuum cover; a first heat transfer copper plate, which is fixed to the evaporation section by soldering; a second heat transfer copper plate, which is fixed to the condensation section by soldering and connected to the heat-conducting heat bridge; wherein the insulation section is a glass capillary tube with an infrared reflective material coating on the surface, and the evaporation section and the condensation section are metal capillaries; the first heat transfer copper plate and the second heat transfer copper plate are provided with grooves for fixing the evaporation section and the condensation section; the insulation section is at least partially arranged to correspond to the visualization optical window; The two capillary ports at one end of the condensation section are connected to two ports of a three-way joint, and the other port of the three-way joint is connected to the filling system; The filling system comprises: a buffer tank, a gas tank and a filling pipe; one end of the filling pipe is connected to the buffer tank and the gas tank respectively, and the other end is connected to the three-way joint; The vacuum pumping system comprises: a first vacuum pump and a second vacuum pump; the first vacuum pump is connected to the filling pipe to achieve a high vacuum environment inside the low-temperature pulsating heat pipe; the second vacuum pump is connected to the vacuum cover through a vacuum pipe to achieve a high vacuum environment inside the vacuum cover; The visual low-temperature insulation system also includes a hanging rod, which is respectively connected to the radiation shield and the flange; The radiation shield is symmetrically provided with through holes, and the channel formed by connecting the through holes forms a visualized optical channel; Wherein, when the hoisting rod hoists the radiation protection cover into the vacuum cover, the visualization optical channel corresponds to the visualization optical window.

2. A visualized low-temperature pulsating heat pipe experimental device according to claim 1, characterized in that: The light source is a cold light element, and the acquisition device is a camera; Among them, a cover structure with low light transmittance is arranged between the light source, the collection device and the corresponding visualization optical window, so as to reduce the radiation heat leakage from the room temperature environment to the low temperature environment inside the vacuum cover through the visualization optical window.

3. A visualized low-temperature pulsating heat pipe experimental device according to claim 1, characterized in that: Also includes an angle adjustment device for adjusting the angle of the vacuum cover; The angle adjustment device comprises: A frame body, arranged outside the vacuum cover, and used for supporting the vacuum cover; A rotating rod, connected to the frame and the vacuum cover respectively, and arranged as the rotation center of the vacuum cover; The lifting lug is arranged on the outer side of the vacuum cover.

4. A visualized low-temperature pulsating heat pipe experimental device according to claim 1, characterized in that: At least 30 layers of high vacuum multi-layer insulation material are wrapped around the outer surfaces of the radiation shield, the first heat transfer copper plate, the second heat transfer copper plate, the refrigerator cold head and the heat conduction bridge.

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