CN111879539B

CN111879539B - Visualized low temperature pulsating heat pipe experimental device

Info

Publication number: CN111879539B
Application number: CN202010658873.7A
Authority: CN
Inventors: 吕秉坤; 徐冬; 李来风; 刘辉明
Original assignee: Technical Institute of Physics and Chemistry of CAS
Current assignee: Technical Institute of Physics and Chemistry of CAS
Priority date: 2020-07-09
Filing date: 2020-07-09
Publication date: 2025-02-18
Anticipated expiration: 2040-07-09
Also published as: CN111879539A

Abstract

The invention relates to the technical field of pulsating heat pipes, and provides a visual low-temperature pulsating heat pipe experimental device which comprises a visual low-temperature heat insulation system, a low-temperature pulsating heat pipe, a filling system, a vacuumizing system and a collecting system, wherein the visual low-temperature heat insulation system comprises a vacuum cover and a radiation-proof cover arranged in the vacuum cover, a visual optical window is arranged on the side wall of the vacuum cover, the low-temperature pulsating heat pipe is arranged in a cavity surrounded by the radiation-proof cover, the filling system is arranged outside the vacuum cover and is connected with the low-temperature pulsating heat pipe through a pipeline extending into the vacuum cover, the vacuumizing system is respectively connected with the vacuum cover and the low-temperature pulsating heat pipe, and the collecting system comprises a light source and a collecting device which are respectively arranged at two sides of the vacuum cover. The invention can observe and record the flow process of the two-phase flow of the low-temperature pulsating heat pipe, and can also carry out continuous measurement analysis and visual observation.

Description

Visual low-temperature pulsating heat pipe experimental device

Technical Field

The invention relates to the technical field of pulsating heat pipes, in particular to a visual low-temperature pulsating heat pipe experimental device.

Background

Pulsating heat pipes (Pulsating Heat Pipe or Oscillating Heat Pipe, PHP or OHP), also known as oscillating heat pipes, are a new type of heat pipe, which has been invented since the 90 s of the 20 th century, has received considerable attention from researchers due to its unique principle of operation and excellent heat transfer properties. The working process of the pulsating heat pipe involves the phenomena of evaporation and condensation of a liquid film, dynamic change of a contact angle between a working fluid and a pipe wall, growth and combination of bubbles, nucleate boiling and the like. Although pulsating heat pipes are simple in structure, the hydrodynamic and thermodynamic coupling involved in the heat and mass transfer process within the pipe makes their working mechanisms very complex. In order to better understand the operation mechanism and the heat transfer process of the pulsating heat pipe, a visual experiment is preferred.

The normal-temperature pulsating heat pipe is easy to realize visual research, and has developed for over twenty years, both in theory and in experiment and application, to a certain extent. The research of the low-temperature pulsating heat pipe is just started in recent years, and the experimental research of the low-temperature pulsating heat pipe at home and abroad mainly adopts gases of H ₂、Ne、N₂ and He, but the thermophysical property of the low-temperature working medium is greatly different from that of the normal-temperature working medium, especially in the aspects of viscosity, surface tension, gasification latent heat and the like, so that the flowing and heat exchanging processes of the low-temperature working medium are greatly different from that of the normal-temperature working medium, and the visualized experiment and theoretical result at normal temperature cannot be directly applied to the low-temperature pulsating heat pipe.

For the research of the low-temperature pulsating heat pipe, numerical simulation is generally utilized to research the flow state of the low-temperature working medium. The low Wen Wenou refrigeration heat transfer generally uses low-temperature liquid working medium, nitrogen boiling point 77K, hydrogen 20K, helium 4.2K and neon 27K, which are common working medium for low-temperature pulsating heat pipe heat transfer, and the low Wen Wenou is that the temperature is less than 120K, and the refrigeration in the interval from 120K to 300K is common Leng Wenou. Because the two-phase flow system in the low-temperature pulsating heat pipe is a complex system, the heat transfer and flow mechanisms are complex and various, the heat transfer and flow mechanisms are deeply and directly related to the flow patterns of two-phase flow, the heat transfer and the hydraulic characteristics under different flow patterns are greatly different, and the numerical simulation is difficult to accurately describe the heat exchange process. Without knowledge of these flow patterns and gas-liquid distributions, accurate heat transfer and flow correlation must not be obtained, and visualization is a necessary means of research.

The present invention has been made in view of the above.

Disclosure of Invention

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

According to the embodiment of the invention, the visual low-temperature pulsating heat pipe experimental device comprises:

the system comprises a visual low-temperature heat insulation system, a low-temperature pulsating heat pipe, a filling system, a vacuumizing system and an acquisition system;

The visual low-temperature heat insulation system comprises a vacuum cover and a radiation-proof cover arranged in the vacuum cover, and a visual optical window is arranged on the side wall of the vacuum cover;

The low-temperature pulsating heat pipe is arranged in a cavity enclosed by the radiation-proof cover;

the filling system is arranged outside the vacuum cover, is connected with the low-temperature pulsating heat pipe through a pipeline extending into the vacuum cover and is used for filling working medium into the low-temperature pulsating heat pipe;

The vacuumizing system is respectively connected with the vacuum cover and the low-temperature pulsating heat pipe and is used for realizing a high-vacuum environment in the vacuum cover and the low-temperature pulsating heat pipe;

the acquisition system comprises a light source and an acquisition device which are respectively arranged at two sides of the vacuum cover corresponding to the visual optical window.

According to one embodiment of the invention, a flange plate is arranged at the upper part of the vacuum cover, a refrigerator is arranged on the flange plate, a cold head of the refrigerator is connected with the low-temperature pulsating heat pipe through a heat conduction heat bridge, and the heat conduction heat bridge is connected with the radiation-proof cover.

Specifically, the refrigerator is connected with the low-temperature pulsating heat pipe and the radiation shield through the heat conduction heat bridge, and the cold energy of the refrigerator is conducted, so that the temperature of the low-temperature pulsating heat pipe and the radiation shield is kept in a low-temperature region.

The contact surfaces among the low-temperature pulsating heat pipe, the refrigerator, the radiation-proof cover and the heat conduction heat bridge are required to be polished smoothly, and indium sheets and the vacuum heat conduction glue Apiezon N are arranged for reducing contact thermal resistance and enhancing heat conduction effect.

In one embodiment, the vacuum cover is of a cylindrical structure made of stainless steel, the lower part is sealed by welding, the upper part is detachably connected with the flange, and sealing is realized between the vacuum cover and the flange by adopting a sealing ring and vacuum sealant.

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

In one embodiment, the refrigerator may be a pulse tube refrigerator, a Stirling refrigerator, a GM refrigerator, or other cryocooler, fixedly attached to the flange.

In one embodiment, the heat conduction heat bridge is made of red copper or aluminum materials, and threaded holes connected with a cold head of the refrigerator and the low-temperature pulsating heat pipe are formed in the heat conduction heat bridge.

According to one embodiment of the invention, the visual cryogenic insulation system further comprises lifting rods respectively connected with the radiation shield and the flange plate;

the radiation shield is symmetrically provided with through holes, and a channel formed by connecting the through holes forms a visual optical channel;

Wherein, when the lifting rod lifts the radiation shield into the vacuum shield, the visual optical channel corresponds to the visual optical window.

Specifically, the radiation-proof cover is hung in the vacuum cover through the hanging rod, so that the stress on the cold head of the refrigerator is further reduced, and the stress deformation is prevented, so that the operation of the refrigerator is influenced.

In one embodiment, the lifting rod of this embodiment is made of stainless steel material in order to increase the strength of the lifting rod.

In one embodiment, in order to reduce solid conduction heat leakage of the lifting rod, the lifting rod of the embodiment is of a thin-wall hollow structure, and air holes are formed in the pipe wall, so that gas in the pipe wall is pumped out in the vacuumizing process, and the problem of gas heat leakage is solved.

According to one embodiment of the invention, the surface of the visualization optical window is coated with a coating of infrared reflective material.

Specifically, by plating the surface of the visual optical window with a coating made of infrared reflective material, the radiant heat leakage of ambient light to the interior of the vacuum enclosure is reduced.

It should be noted that, heat insulation is realized in a low-temperature environment, convection, heat conduction and radiation are required to be reduced, heat leakage is reduced from 3 aspects, low temperature is realized by matching with a low-temperature refrigerator, high vacuum only reduces air convection, a radiation shield is required to reduce heat radiation, and the cross-sectional area of a lifting rod is required to be reduced to reduce heat conduction.

In one embodiment, the two visual optical windows are symmetrically arranged at two sides of the vacuum cover and are at the same level with the visual part of the low-temperature pulsating heat pipe to form an optical passage passing through the visual part of the low-temperature pulsating heat pipe, and in addition, the visual optical windows and the vacuum cover are sealed by adopting threads, flanges and sealing rings.

According to one embodiment of the present invention, the low temperature pulsating heat pipe includes:

the capillary tube is bent to form a condensing section, a heat insulation section and an evaporating section which are arranged along the axial direction of the vacuum cover from top to bottom;

the first heat transfer copper plate is fixed with the evaporation section through soldering tin;

the second heat transfer copper plate is fixed with the condensing section through soldering tin and is connected with the heat conduction heat bridge;

The heat insulation section is a glass capillary with a surface plated with an infrared reflecting material coating, and the evaporation section and the condensation section are metal capillaries;

Grooves for fixing the evaporation section and the condensation section are formed in the first heat transfer copper plate and the second heat transfer copper plate;

the insulating segment is disposed at least partially corresponding to the visualization optical window.

Specifically, the low-temperature pulsating heat pipe is made into at least 1 loop type tubular pulsating heat pipe by bending a capillary tube, and comprises an evaporation section, a heat insulation section and a condensation section, wherein the heat insulation section is a glass pipe, and the evaporation section and the condensation section are metal pipes.

Further, the low-temperature pulsating heat pipe is vertically arranged, the condensation section is positioned at the uppermost end, and the evaporation section is positioned at the bottommost end.

Further, the first heat transfer copper plate and the second heat transfer copper plate are similar in structure, grooves with the width slightly larger than the size of the low-temperature pulsating heat pipe are machined on the plate surface, then the first heat transfer copper plate and the second heat transfer copper plate are welded together with the evaporation section and the condensation section of the low-temperature pulsating heat pipe respectively, and soldering tin is filled in gaps between the low-temperature pulsating heat pipe and the grooves so as to reduce thermal resistance and ensure good thermal contact.

In order to avoid the capillary tube from being blocked during the pipe bending process, the internal channels of the pipe are blocked, and the minimum distance between two adjacent pipes needs to be ensured.

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

In one embodiment, the material of the heat insulation section of the low-temperature pulsating heat pipe is quartz glass or Pyrex glass, and the material of the evaporation section and the condensation section is copper pipe or stainless steel pipe. Two ends of the glass capillary tube are respectively connected with an evaporation section and a condensation section of the metal capillary tube, a boss is processed on the glass capillary tube in a knife edge flange and indium wire sealing mode, a sealing groove is processed on the knife edge flange for placing the indium wire, glass is used as a sealing surface, and bolts are used for pressing the flange from two sides of the boss so as to obtain a good sealing effect.

Further, a spring washer is arranged between the bolt and the knife edge flange. The influence of expansion and contraction generated by different thermal expansion coefficients at low temperature among the knife edge flange, the glass capillary tube, the copper tube and the fastening screw is relieved through the spring washer, and the sealing performance and the pressure resistance are further improved.

According to one embodiment of the invention, two capillary ports at one end of the condensing section are connected to two ports of a three-way connection, and the other port of the three-way connection is connected to the filling system.

Specifically, two ports are reserved after the capillary tube is bent and formed, the two ports are reserved on one side of a condensing section, a three-way joint is arranged, the two ports of the capillary tube are in butt joint with the two ports of the three-way joint, and the other port of the three-way joint is connected with a filling system to form a closed low-temperature pulsating heat pipe.

According to one embodiment of the invention, the filling system comprises a buffer tank, a gas tank and a filling pipe;

one end of the filling pipe is connected with the buffer tank and the gas tank respectively, and the other end of the filling pipe is connected with the three-way joint.

Specifically, the working medium filling of the low-temperature pulsating heat pipe is realized through the arrangement of the buffer tank, the gas tank and the filling pipe.

According to one embodiment of the invention, the vacuum pumping system comprises a first vacuum pump and a second vacuum pump;

The first vacuum pump is connected with the filling pipe and is used for realizing a high vacuum environment inside the low-temperature pulsating heat pipe;

the second vacuum pump is connected with the vacuum cover through a vacuum tube and is used for realizing a high vacuum environment inside the vacuum cover.

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

and a cover body structure with low light transmittance is arranged between the light source and the acquisition device and between the light source and the corresponding visual optical window, and is used for reducing radiation and heat dissipation in the vacuum cover.

Specifically, the light source and the acquisition device are arranged outside the vacuum cover and close to the visual optical window, and a back side polishing mode is adopted, namely, the light source and the acquisition device are symmetrically arranged on two sides of the vacuum cover. And a cover body structure is further arranged on paths from the light source and the acquisition device to the visual optical window respectively, so that radiation heat leakage of ambient light to the inside of the vacuum cover is reduced.

In one embodiment, the light source may be a high-power LED strobe cold light source, the trigger signal of which uses the synchronous output trigger signal of a camera, or a single Kong Xian gas lamp medical cold light source, the camera uses a CCD high-speed camera for shooting the working medium running state of the low-temperature pulsating heat pipe at a certain frequency.

In one embodiment, the cover structure may be a black shade cloth of low light transmittance.

In one embodiment, the acquisition system further comprises a temperature acquisition module, a pressure acquisition module, a data acquisition instrument, and a personal computer. The temperature acquisition module is used for acquiring the instantaneous temperature value of the low-temperature pulsating heat pipe, and the pressure acquisition module is used for acquiring the pressure value of the low-temperature pulsating heat pipe. The measured parameters such as the instantaneous temperature value, the pressure value and the like of the low-temperature pulsating heat pipe and the image shot by the camera are input into a personal computer through a data acquisition instrument for monitoring, storing and calculating so as to facilitate the later data analysis and use.

Further, the temperature acquisition module adopts a platinum resistance thermometer, is arranged on the copper plates of the evaporation section and the condensation section of the low-temperature pulsating heat pipe, and is coated with Apiezon N low-temperature vacuum heat-conducting glue to ensure good thermal contact of the two. When in installation, the lead wire is adhered to the surface of the temperature measuring copper plate to be used as a heat sink wire.

According to one embodiment of the invention, the vacuum cover further comprises an angle adjusting device for adjusting the angle of the vacuum cover;

the angle adjusting device includes:

The frame body is arranged outside the vacuum cover and used for supporting the vacuum cover;

The rotating rod is respectively connected with the frame body and the vacuum cover and is arranged as the rotating center of the vacuum cover;

and the lifting lug is arranged at the outer side of the vacuum cover.

Specifically, through the setting of angle adjusting device, can realize the adjustment to visual low temperature pulsation heat pipe experimental apparatus inclination, can adjust visual low temperature pulsation heat pipe experimental apparatus to required angle.

In one embodiment, the angle adjusting device further comprises an angle dial and a scale arranged on the angle dial, and the inclined angle of the low-temperature pulsating heat pipe experimental device can be visually judged through the position relationship between the angle dial and the scale.

According to one embodiment of the invention, more than 30 layers of high vacuum multi-layer heat insulating Materials (MLI) are used for wrapping the positions where radiation heat leakage needs to be reduced, and the positions comprise the outer surface of a radiation shield, the outer surface of a second heat transfer copper plate of a condensing section of a low-temperature pulsation heat pipe and a first heat transfer copper plate of an evaporating section, a refrigerator cold head and a heat conduction heat bridge.

The experimental device provided by the invention can observe and record the flow process of the two-phase flow of the low-temperature pulsating heat pipe through the corresponding visual optical window, and the working characteristics of the experimental device can also be continuously measured, analyzed and visually observed.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic layout diagram of each component in a visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention;

fig. 2 is a first schematic diagram of an assembly relationship of each component in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention;

Fig. 3 is a second schematic diagram of an assembly relationship of each component in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention;

fig. 4 is a third schematic diagram of an assembly relationship of each component in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention;

Fig. 5 is a schematic diagram of an assembly relationship of a low-temperature pulsating heat pipe, a heat conduction heat bridge and a three-way joint in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention;

Fig. 6 is an explosion schematic diagram of an assembly relationship among a low-temperature pulsating heat pipe, a heat conduction heat bridge and a three-way joint in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention;

FIG. 7 is a schematic diagram of the assembly relationship between a glass capillary tube and a metal capillary tube in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention;

fig. 8 is a fourth schematic diagram of an assembly relationship of each component in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention;

Fig. 9 is a fifth schematic diagram of an assembly relationship of each component in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention.

Reference numerals:

1, a vacuum cover, 101, a visual optical window, 102, a flange plate and 103, a hoisting rod;

2, a radiation shield 201, a through hole;

3, a low-temperature pulsating heat pipe; 301 an evaporation section, 302 an insulation section, 303 a condensation section, 304 a first heat transfer copper plate, 305 a second heat transfer copper plate and 306 a groove;

The device comprises a light source, a collecting device, a refrigerator, a heat conduction heat bridge, a tee joint, a buffer tank, a gas tank, a filling pipe, a first vacuum pump, a second vacuum pump, a vacuum pipe, a frame, a rotating rod, a lifting lug, an angle plate, a knife edge flange, a boss, a film heater, a glass fixing piece, a fixing frame, an adjusting plate and an adjusting rod, wherein the light source, the collecting device, the refrigerator, the heat conduction heat bridge, the tee joint, the buffer tank, the gas tank, the filling pipe, the first vacuum pump, the second vacuum pump, the vacuum pipe, the frame, the rotating rod, the lifting lug, the angle plate, the knife edge flange, the boss, the film heater, the glass fixing piece, the fixing frame, the adjusting plate and the adjusting rod.

It should be noted that these drawings and the written description are not intended to limit the scope of the inventive concept in any way, but to illustrate the inventive concept to those skilled in the art by referring to the specific embodiments.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the embodiments of the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

Fig. 1 is a schematic layout diagram of each component in a visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention. The visual low-temperature pulsating heat pipe 3 experimental device is mainly used for showing the relative position relation among all the components of the visual low-temperature pulsating heat pipe 3 experimental device. As can be seen from fig. 1, the inside of the vacuum hood 1 is provided with a radiation shield 2, the inside of the radiation shield 2 is provided with a low-temperature pulsating heat pipe 3, wherein the radiation shield 2 is hoisted on a flange plate 102 of the vacuum hood 1 by a hoisting rod 103, the flange plate 102 is also provided with a refrigerator 6, and the refrigerator 6 is connected with the low-temperature pulsating heat pipe 3 inside the radiation shield 2 through a heat conduction heat bridge 7.

Further, the vacuum cover 1 is also symmetrically provided with a visual optical window 101, the radiation-proof cover 2 is correspondingly provided with a through hole 201 corresponding to the visual optical window 101, and the light source 4 and the acquisition device 5 are respectively arranged at two sides of the vacuum cover 1 and correspondingly arranged with the visual optical window 101.

Further, the second vacuum pump 13 is connected with the inside of the vacuum housing 1 through the vacuum tube 14 to realize high vacuum inside the vacuum housing 1, and the first vacuum pump 12 is connected with the low-temperature pulsating heat pipe 3 through the filling tube 11 to realize high vacuum inside the low-temperature pulsating heat pipe 3.

The high vacuum means that the pressure is 1×10 ^-3 Pa or less, and this value is generally used as a standard in the low temperature range, and the gas heat conduction is very small and negligible below this value.

Further, as can be seen from fig. 1, one end of the filling pipe 11 is connected to the low temperature pulsating heat pipe 3, and the other end is connected to the first vacuum pump 12, the buffer tank 9 and the gas tank 10, respectively, where various valve bodies disposed on the filling pipe 11 are omitted, and the disposition and working principle of the valve bodies on the filling pipe 11 can refer to the conventional disposition in the art, so that redundant description will not be made here for saving the space.

It should be noted that, in fig. 1, a cover structure with low light transmittance is disposed between the light source 4 and the corresponding visualization optical window 101, and between the acquisition device 5 and the corresponding visualization optical window 101, and for convenience of observation, in fig. 1, this part of the cover structure with low light transmittance is omitted, and is used for reducing radiation heat leakage of the room temperature environment to the low temperature environment inside the vacuum cover 1 through the visualization optical window 101, and this part of the arrangement can be understood as setting a light shielding structure on paths from the light source 4 and the acquisition device 5 to the corresponding visualization optical window 101 respectively.

The invention also needs to be noted that the low-temperature pulsating heat pipe 3 with different pipe diameters, different liquid filling rates, different inclined angles, different heating amounts, different lengths of the heat insulation sections 302, different loop numbers and different working mediums can be replaced, and continuous measurement analysis and visual observation can be carried out on the two-phase flow flowing process of the different low-temperature pulsating heat pipes 3.

Fig. 2 is a first schematic diagram of an assembly relationship of each component in the visualized low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention. The visual low-temperature pulsating heat pipe 3 experimental device provided by the invention is mainly shown from the perspective of an axial side view. As can be seen from fig. 2, the vacuum cover 1 is provided with a frame 15 at the outside, and an angle scale 18 is provided on the frame 15 for visually reading the inclination angle of the vacuum cover 1. Two visual optical windows 101 and lifting lugs 17 are symmetrically arranged on the vacuum cover 1. The vacuum cover 1 is provided with a flange plate 102, and the flange plate 102 is provided with a refrigerator 6, a KF vacuum connector, an aviation plug and other corresponding auxiliary equipment.

Fig. 3 is a second schematic diagram of an assembly relationship of each component in the visualized low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention. The visual low-temperature pulsating heat pipe 3 experimental device provided by the invention is mainly shown from the perspective of a side cross section of an axle. As can be seen from fig. 3, a suspended radiation shield 2 is arranged inside the vacuum shield 1, and the radiation shield 2 is connected with the flange 102 by means of a lifting rod 103. The cold head of the refrigerator 6 is connected with the radiation shield 2 and the low-temperature pulsation heat pipe 3 in the radiation shield 2 through a heat conduction heat bridge 7.

Further, an angle dial 18 and a rotating rod 16 are arranged outside the vacuum cover 1, the vacuum cover 1 can rotate around the rotating rod 16, and the angle dial 18 is used for observing the rotating angle of the vacuum cover 1.

It should be noted that, for saving the space, the structure such as the bearing, the bearing seat, etc. is further provided between the rotating rod 16 and the vacuum housing 1, and the detailed description is not made here, and the specific arrangement may refer to the conventional design in the art.

Further, as can be seen from fig. 2, the height of the cryopump heat pipe 3 corresponds to the visualization optical window 101, wherein the cryopump heat pipe 3 includes a transparent pipe with one end being visualized, which is in the visualization range of the visualization optical window 101.

Fig. 4 is a third schematic diagram of an assembly relationship of each component in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention. The device is mainly used for showing the position relationship among the low-temperature pulsating heat pipe 3, the heat conduction heat bridge 7, the filling pipe 11, the refrigerator 6, the rotating rod 16 and the angle scale 18, and other parts are omitted in fig. 4. As can be seen from fig. 4, the heat conducting thermal bridge 7 is connected to the cold head of the refrigerator 6 and the low temperature pulsating heat pipe 3, respectively.

Further, the filling pipe 11 extends from the outside of the flange 102 to the low-temperature pulsating heat pipe 3, so as to connect with the low-temperature pulsating heat pipe 3.

Fig. 5 is a schematic diagram of an assembly relationship of a low-temperature pulsating heat pipe 3, a heat conduction heat bridge 7 and a three-way joint 8 in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention. The heat pipe is mainly used for showing the specific structure of the low-temperature pulsating heat pipe 3 and the connection relation between the low-temperature pulsating heat pipe 3 and the heat conduction heat bridge 7. As can be seen from fig. 5, the low temperature pulsating heat pipe 3 comprises an evaporation section 301, an insulation section 302, a condensation section 303, a first copper heat transfer plate 304 and a second copper heat transfer plate 305. The evaporation section 301 and the first heat transfer copper plate 304 are fixed by soldering tin, and are arranged at the bottom of the low-temperature pulsating heat pipe 3 in the vertical direction. The condensation section 303 and the second heat transfer copper plate 305 are fixed by soldering tin, and are arranged at the top of the low-temperature pulsating heat pipe 3 in the vertical direction. The heat insulation section 302 is disposed between the evaporation section 301 and the condensation section 303.

Further, the connection between the evaporation section 301 and the insulation section 302, and between the condensation section 303 and the insulation section 302 is achieved by the knife edge flange 19.

Further, 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 heat insulation section 302 is a glass tube, and the evaporation section 301 and the condensation section 303 are metal tubes.

Further, since the low-temperature pulsating heat pipe 3 is formed by bending a capillary tube, two free ports naturally exist, and in the present invention, the two free ports are disposed at one side of the condensation section 303 and connected through the three-way joint 8. Two ports of the three-way joint 8 are respectively connected with two free ports of the low-temperature pulsating heat pipe 3, and the other port of the three-way joint 8 is connected with a filling pipe 11 to fill working medium in the low-temperature pulsating heat pipe 3.

Fig. 6 is an explosion schematic diagram of the assembly relationship among the low-temperature pulsating heat pipe 3, the heat conduction heat bridge 7 and the three-way joint 8 in the visualized low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention. The specific structure of the low-temperature pulsating heat pipe 3 is mainly shown in a split manner in the connection relation between the low-temperature pulsating heat pipe 3 and the heat conduction heat bridge 7. As can be seen from fig. 6, grooves 306 are respectively provided on the first heat transfer copper plate 304 and the second heat transfer copper plate 305 of the low-temperature pulsating heat pipe 3, and the grooves 306 are used for fixing 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 groove 306 is filled with solder, and then the first heat transfer copper plate 304 and the second heat transfer copper plate 305 are welded with the evaporation section 301 and the condensation section 303 of the low-temperature pulsating heat pipe 3, respectively.

It should be noted that fig. 6 further includes a glass fixing member 22 connected to the first heat transfer copper plate 304 and the second heat transfer copper plate 305, and the glass fixing member 22 is made of G10 glass fiber reinforced plastic, and can withstand a great pressure without being damaged and deformed, and has a low thermal conductivity. The heat insulation section 302 of the low-temperature pulsating heat pipe is made of glass materials, is fragile in stress, and is connected with the first heat transfer copper plate 304 and the second heat transfer copper plate 305 by adopting the glass fixing piece 22 made of G10 glass fiber reinforced plastic, so that the low-temperature pulsating heat pipe is fixed, and glass breakage is prevented.

Fig. 7 is a schematic diagram of an assembly relationship between a glass capillary tube and a metal capillary tube in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention. The cross-section of fig. 7 is shown, and other parts are omitted, but should not be understood as being unclear or inaccurate, the knife edge flanges 19 are all shown in fig. 3 to 6, fig. 7 is only a cross-section of one of the knife edge flanges 19, and the rest of the knife edge flanges 19 are all arranged in the same way.

Further, as can be seen from fig. 7, in the cross-sectional view of the knife edge flange 19, the evaporation section 301 abuts against the heat insulation section 302, wherein a boss 20 is arranged at the matching position of the heat insulation section 302 and the evaporation section 301, a sealing groove is processed on the knife edge flange 19 to place indium wires, and the boss 20 and the knife edge flange 19 are pressed by bolts, so that the heat insulation section 302 and the evaporation section 301 are sealed. The same is true of the connection between the adiabatic section 302 and the condenser section 303.

Fig. 8 and fig. 9 are fourth and fifth diagrams of assembly relations of each component in the visual low-temperature pulsating heat pipe experimental device provided by the embodiment of the invention. The visual low-temperature pulsating heat pipe 3 experimental device provided by the invention is mainly shown from the perspective of an axial side view. As can be seen from fig. 8 and 9, the outer part of the vacuum housing 1 is provided with a frame body 15, and the frame body 15 is provided with an angle disc 18 for intuitively reading the inclination angle of the vacuum housing 1. The vacuum cover 1 is symmetrically provided with a visual optical window 101 and a lifting lug 17. The vacuum cover 1 is provided with a flange plate 102, and the flange plate 102 is provided with a refrigerator 6, a KF vacuum connector, an aviation plug and other corresponding auxiliary equipment.

In particular, in order to be able to adapt to different viewing areas, a lifting device may be provided between the visualization optical window 101 and the radiation shield 2. The lifting device comprises two symmetrically arranged adjusting plates 24, a fixed frame 23 connected with the adjusting plates 24 and an adjusting rod 25, and the height of the adjusting plates 24 in the vacuum cover 1 is adjusted through the adjusting rod 25, so that the visual range of the visual optical window 101 is adjusted.

The fixing frame 23 includes an outer frame and an inner frame, and G10 glass fiber reinforced plastic interposed between the outer frame and the inner frame, and the G10 glass fiber reinforced plastic is used for preventing heat insulation and reducing heat conduction.

Further, the adjusting plate 24 is a copper plate, the adjusting plate 24 is coated by a high vacuum multi-layer heat insulating material, a necessary observation hole is reserved according to the requirement, the area of the observation hole is smaller than that of the visual optical window 101, the observation and shooting of different positions of the heat insulating section 302 of the low-temperature pulsating heat pipe 3 are realized by moving the observation hole up and down through the adjusting rod 25, meanwhile, most of heat radiation introduced by the window is blocked by the copper plate, and the radiation heat leakage is reduced to the greatest extent while the visualization is realized. When the observation hole is not formed on the adjusting plate 24, the test bed is equivalent to a conventional test bed of the low-temperature pulsating heat pipe, and a conventional thermal performance experiment of the low-temperature pulsating heat pipe can be performed.

It should be noted that, the adjusting of the adjusting rod 25 to the adjusting plate 24 may be automatic or manual, and an air cylinder or a hydraulic cylinder or a manual adjusting device may be disposed at the connection between the adjusting rod 25 and the outer side of the flange 102.

In general, the experimental device provided by the invention can observe and record the flow process of the two-phase flow of the low-temperature pulsating heat pipe 3 through the corresponding visual optical window 101, and the working characteristics of the experimental device can also be continuously measured, analyzed and visually observed. The problem that the low-temperature environment is difficult to maintain due to the fact that radiation heat leakage is large caused by a visual window is also solved. The problems of structural strength and working medium leakage caused by large difference of thermal expansion coefficients of the visual element and the metal connecting material at low temperature and the problem that the visual tube section of the low-temperature pulsating heat tube 3 is not enough in strength and is easy to break are also solved.

Furthermore, the invention adopts a vacuum multilayer heat insulation mode with the radiation shield 2, only a necessary optical passage is reserved when the radiation shield 2 and the multilayer heat insulation materials are arranged, the surfaces of the glass capillaries of the heat insulation sections 302 of the visual optical window 101 and the low-temperature pulsating heat pipe 3 are coated with infrared reflection material, the light source 4, the camera and the visual optical window 101 are respectively provided with a cover body structure with low light transmittance, and meanwhile, the large-cold-capacity refrigerator 6 takes away various measures such as radiation heat leakage introduced by the visual optical window 101, and the like, so that the problem of large low-temperature visual radiation heat leakage is solved.

Further, by using the experimental platform provided by the invention, the working flow state of the low-temperature pulsating heat pipe 3 can be observed and recorded through the corresponding visual optical window 101, the running state and the running parameters of a working medium can be monitored simultaneously, the visualization of the two-phase flow flowing process of the low-temperature pulsating heat pipe 3 is realized, the experimental platform can be used for researching the thermal-hydrodynamic characteristics, the gas-liquid phase transition and the flow pattern conversion of the working medium of the low-temperature pulsating heat pipe 3, and analyzing the influence of bubble growth on the system running and oscillation characteristics and the influence of various parameters such as pipe diameter, liquid filling rate, inclination angle, heating quantity, length of an insulation section 302, loop number and the like on the fluid movement and heat transfer of the low-temperature pulsating heat pipe 3.

Furthermore, the invention adopts the low-temperature refrigerator 6 as a cold source, and can provide cooling for the low-temperature pulsating heat pipe 3 for researching the low-temperature working medium in a wider working temperature zone. By adjusting the liquid filling rate of the working medium and/or adjusting the temperature of the condenser of the low-temperature pulsating heat pipe 3, the saturated pressure and the saturated temperature in the working process of the low-temperature pulsating heat pipe 3 can be adjusted and changed, and research under different working conditions can be carried out.

In addition, compared with other low-temperature visualization methods such as an endoscope method, a capacitance tomography method and the like, the visualization method has the advantages of simple structure, easiness in operation, visual imaging and high reliability.

In describing embodiments of the present invention, it should be noted that, unless explicitly stated or limited otherwise, the terms "connected," "connected," and "coupled" should be construed broadly, and may be, for example, fixedly connected, detachably connected, integrally connected, mechanically connected, electrically connected, directly connected, or indirectly connected via an intermediate medium. The specific meaning of the above terms in embodiments of the present invention will be understood in detail by those of ordinary skill in the art.

In embodiments of the invention, unless expressly specified and limited otherwise, a first feature "up" or "down" on a second feature may be that the first and second features are in direct contact, or that the first and second features are in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

In a specific embodiment, as shown in fig. 1, the invention provides a visual low-temperature pulsating heat pipe experimental device, which comprises a visual low-temperature heat insulation system, a low-temperature pulsating heat pipe 3, a filling system, a vacuumizing system and a collecting system, wherein the visual low-temperature heat insulation system comprises a vacuum cover 1 and a radiation-proof cover 2 arranged in the vacuum cover 1, a visual optical window 101 is arranged on the side wall of the vacuum cover 1, the low-temperature pulsating heat pipe 3 is arranged in a cavity surrounded by the radiation-proof cover 2, the filling system is arranged outside the vacuum cover 1 and is connected with 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, the vacuumizing system is respectively connected with 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, and the collecting system comprises a light source 4 and a collecting device 5 respectively arranged on two sides of the vacuum cover 1 and the collecting device 5 corresponding to the visual optical window 101.

In one embodiment, two visual optical windows 101 are disposed on both sides of the vacuum enclosure 1 opposite to the low-temperature pulsating heat pipe 3 at the same level, forming an optical path through the insulating 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. Stainless steel circular tube with external screw thread passes through welded connection with vacuum envelope 1, and stainless steel circular tube top processing has a spill platform and O circle groove for place O circle and quartz glass, locking seal with quartz glass through the screw flange, install an annular thin slice of 0.5mm thick polytetrafluoroethylene material simultaneously between quartz glass and screw flange, prevent to destroy quartz glass when fastening sealed quartz glass, influence sealed effect. The threaded connection enables the device to be detachable, transparent glass is convenient to replace, and the service life of the device is prolonged.

In a specific embodiment, as shown in fig. 1 to 4, the invention provides a visual low-temperature pulsating heat pipe experiment device, a flange plate 102 is arranged at the upper part of a vacuum cover 1, a refrigerator 6 is arranged on the flange plate 102, a cold head of the refrigerator 6 is connected with a low-temperature pulsating heat pipe 3 through a heat conduction heat bridge 7, and the heat conduction heat bridge 7 is connected with a radiation protection cover 2.

Specifically, the refrigerator 6 and the low-temperature pulsating heat pipe 3 are connected with the radiation shield 2 through the heat conduction heat bridge 7, and are used for conducting the cold energy of the refrigerator, so that the temperature of the low-temperature pulsating heat pipe 3 and the radiation shield 2 is kept in a low-temperature region.

It should be noted that, contact surfaces among the low-temperature pulsating heat pipe 3, the refrigerator 6, the radiation shield 2 and the heat conduction heat bridge 7 need to be polished smooth, and indium sheets and coating Apiezon N vacuum heat conduction glue are arranged for reducing contact thermal resistance and enhancing heat conduction effect.

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 with the flange 102, and sealing is realized between the vacuum cover 1 and the flange 102 by adopting a sealing ring and vacuum sealant.

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

In one embodiment, the refrigerator 6 may be a pulse tube refrigerator 6, a Stirling refrigerator 6, a GM refrigerator 6, or other cryorefrigerator 6, fixedly coupled to the flange 102.

In one embodiment, the heat conduction heat bridge 7 is made of red copper or aluminum material, and is provided with a threaded hole connected with the cold head of the refrigerator 6 and the low-temperature pulsating heat pipe 3.

In one embodiment, as shown in fig. 1 to 4, the visual cryogenic insulation system further comprises a lifting rod 103 connected to the radiation shield 2 and the flange 102, respectively, a through hole 201 provided on the radiation shield 2, wherein the lifting rod 103 lifts the radiation shield 2 into the through hole 201 and corresponds to the visual optical window 101.

Specifically, the radiation shield 2 is hoisted in the vacuum cover 1 through the hoisting rod 103, so that the stress on the cold head of the refrigerator 6 is further reduced, and the stress deformation is prevented, so that the operation of the refrigerator 6 is influenced.

In one embodiment, to increase the strength of the lifting bar 103, the lifting bar 103 of the present embodiment is made of a stainless steel material.

In one embodiment, in order to reduce solid conduction heat leakage of the lifting rod 103, the lifting rod 103 of this embodiment is provided with a thin-walled hollow structure, and air holes are formed in the pipe wall, so that gas in the pipe wall is pumped out in the process of vacuumizing, and the problem of gas heat leakage is eliminated.

In one embodiment, as shown in fig. 1-4, the surface of the visualization optical window 101 is coated with a coating of infrared reflective material.

Specifically, by plating the surface of the visualization optical window 101 with a coating made of an infrared reflective material, radiation heat leakage of ambient light to the inside of the vacuum enclosure 1 is reduced.

In this embodiment, a high vacuum multi-layer heat insulation mode is adopted to realize heat insulation in a low temperature environment, convection, heat conduction and radiation are required to be reduced, heat leakage is reduced from 3 aspects, a low temperature is realized by matching with a cryocooler, the high vacuum only reduces air convection, the radiation shield 2 and the multi-layer heat insulation composite material are required to reduce heat radiation, and the cross section area of the lifting rod 103 is reduced to reduce heat conduction.

In one embodiment, two visual optical windows 101 are symmetrically arranged at two sides of the vacuum cover 1 and are at the same level with the visual part of the low-temperature pulsating heat pipe 3, so that an optical passage passing through the visual part of the low-temperature pulsating heat pipe 3 is formed, and in addition, the visual optical windows 101 and the vacuum cover 1 are sealed by adopting threads, flanges and sealing rings.

In a specific embodiment, as shown in fig. 1 to 7, the invention provides a visual low-temperature pulsating heat pipe experimental device, wherein a low-temperature pulsating heat pipe 3 mainly comprises a condensation section 303, an insulation section 302 and an evaporation section 301 which are formed by bending capillaries along the axial direction of a vacuum cover 1 and are arranged from top to bottom, a first heat transfer copper plate 304 is used for fixing the evaporation section 301, a second heat transfer copper plate 305 is used for fixing the condensation section 303 and is connected with a heat conduction heat bridge 7, the insulation section 302 is a glass capillary with an infrared reflection material coating on the surface, the evaporation section 301 and the condensation section 303 are metal capillaries, grooves 306 for fixing the evaporation section 301 and the condensation section 303 are arranged on the first heat transfer copper plate 304 and the second heat transfer copper plate 305, and the insulation section 302 is at least partially arranged corresponding to a visual optical window 101.

Specifically, the low-temperature pulsating heat pipe 3 is made into at least 1 loop type tubular pulsating heat pipe by bending capillary tubes, the low-temperature pulsating heat pipe 3 comprises 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.

Further, the low-temperature pulsating heat pipe 3 is vertically arranged, the condensation section 303 is positioned at the uppermost end, and the evaporation section 301 is positioned at the bottommost end.

Further, the first heat transfer copper plate 304 and the second heat transfer copper plate 305 are similar in structure, and grooves 306 with widths slightly larger than the size of the low-temperature pulsating heat pipe 3 are machined on the plate surface, and then the first heat transfer copper plate 304 and the second heat transfer copper plate 305 are welded with the evaporation section 301 and the condensation section 303 of the low-temperature pulsating heat pipe 3 respectively, and gaps between the low-temperature pulsating heat pipe 3 and the grooves 306 are filled with soldering tin to reduce thermal resistance and ensure good thermal contact.

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 the voltage, wherein the thin film heater 21 of the evaporation section 301 is used for heating 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 for controlling the temperature of the condensation section 303 of the low-temperature pulsating heat pipe 3.

In one embodiment, as shown in fig. 7, the material of the heat insulation section 302 of the low-temperature pulsating heat pipe 3 is quartz glass or Pyrex glass, and the material of the evaporation section 301 and the condensation section 303 is copper pipe. Two ends of the glass capillary tube are respectively connected with an evaporation section 301 and a condensation section 303 of the metal capillary tube, a boss 20 is processed on the glass capillary tube in a knife edge flange 19 and indium wire sealing mode, a sealing groove is processed on the knife edge flange 19 for placing indium wires, glass is used as a sealing surface, and bolts are used for pressing the flange from two sides of the boss 20, so that a good sealing effect is obtained.

The inner diameters of the glass capillary and the metal capillary are required to satisfy the following formula:

wherein sigma is the surface tension of the working medium;

ρ _L is the density of the liquid working medium at the saturation temperature;

ρ _V is the density of the gaseous working medium at saturation temperature;

g is gravitational acceleration.

The working medium is nitrogen, and the value of the inner diameter is 0.5-2 mm.

The glass capillary tube is then used as high-pressure resistant high-precision glass tube, and the pressure resistance of the glass capillary tube and the metal capillary tube is 0.5MPa.

Further, a spring washer is provided between the bolt and the knife edge flange 19. The influence of expansion and contraction generated by different thermal expansion coefficients at low temperature among the knife edge flange 19, the glass capillary tube, the copper tube and the fastening screw is relieved through the spring washer, so that the sealing performance and the pressure resistance are further improved.

The knife edge flange 19 is matched with indium wire for sealing, so that the problem of difficult sealing at low temperature of a low-temperature visualization system is solved. The influence of expansion and contraction generated by different thermal expansion coefficients at low temperature among the knife edge flange 19, the glass capillary tube, the copper tube and the fastening screw is relieved through the spring washer, so that the sealing performance and the pressure resistance are further improved.

It should be further noted that, the G10 composite material is fixedly connected between the evaporation section 301 and the condensation section 303 of the low-temperature pulsating heat pipe 3, so as to improve the overall strength, prevent the quartz glass tube of the heat insulation section 302 from being broken, and reinforce the low-temperature pulsating heat pipe 3 by adopting the G10 composite material, thereby solving the problem that the strength of the visual glass element is not fragile enough.

In one embodiment, as shown in fig. 5 and 6, two capillary ports at one end of the condensing section 303 are connected to two ports of the three-way junction 8, and the other port of the three-way junction 8 is connected to the filling system.

Specifically, two ports are reserved after the capillary tube is bent and formed, the two ports are reserved on one side of the condensing section 303, the three-way joint 8 is arranged, the two ports of the capillary tube are in butt joint with the two ports of the three-way joint 8, and the other port of the three-way joint 8 is connected with the filling system to form the closed low-temperature pulsating heat pipe 3.

In a specific embodiment, as shown in fig. 1 to 4, the invention provides a visual low-temperature pulsating heat pipe experimental device, and a filling system comprises a buffer tank 9, a gas tank 10 and a filling pipe 11, wherein one end of the filling pipe 11 is respectively connected with the buffer tank 9 and the gas tank 10, and the other end is connected with a three-way joint 8.

Specifically, the buffer tank 9, the gas tank 10 and the filling pipe 11 are arranged, so that the working medium of the low-temperature pulsating heat pipe 3 is filled.

In one embodiment, as shown in fig. 1, the vacuumizing system comprises a first vacuum pump 12 and a second vacuum pump 13, wherein the first vacuum pump 12 is connected with a filling pipe 11 for realizing a high vacuum environment inside the low-temperature pulsating heat pipe 3, and the second vacuum pump 13 is connected with the vacuum cover 1 through a vacuum pipe 14 for realizing the high vacuum environment inside the vacuum cover 1.

Specifically, by providing the first vacuum pump 12 and the second vacuum pump 13, a high vacuum environment within the low-temperature pulsating heat pipe 3 and the vacuum enclosure 1 is realized.

In one embodiment, as shown in fig. 1, the light source 4 is a cold light element, and the collecting device 5 is a camera, wherein a cover structure with low light transmittance is arranged between the light source 4 and the collecting device 5 and between the light source and the corresponding visual optical window 101, so as to reduce radiation and heat dissipation inside the vacuum cover 1.

Specifically, the light source 4 and the collection device 5 are disposed outside the vacuum housing 1, proximate to the visualization optical window 101, and in a back side lighting form, that is, the light source 4 and the collection device 5 are symmetrically disposed at both sides of the vacuum housing 1. A cover structure is further arranged on the paths from the light source 4 and the acquisition device 5 to the visual optical window 101 respectively, so as to reduce radiation heat leakage of ambient light to the interior of the vacuum cover 1.

In one embodiment, the light source 4 may be a high-power LED strobe cold light source 4, the trigger signal of which adopts a synchronous output trigger signal of a camera, or a single-hole xenon lamp medical cold light source 4, and the camera is used for shooting the working medium running state of the low-temperature pulsating heat pipe 3 at a certain frequency.

In one embodiment, the acquisition system further comprises a temperature acquisition module, a pressure acquisition module, a data acquisition instrument, and a personal computer. The temperature acquisition module is used for acquiring the instantaneous temperature value of the low-temperature pulsating heat pipe 3, and the pressure acquisition module is used for acquiring the pressure values of the low-temperature pulsating heat pipe 3 and the buffer tank 9. The measured parameters such as the instantaneous temperature value, the pressure value and the like of the low-temperature pulsating heat pipe 3 and the image shot by the camera are input into a personal computer through a data acquisition instrument for monitoring, storing and calculating so as to facilitate the later data analysis and use.

The pressure acquisition module comprises pressure sensors respectively connected with the buffer tank 9 and the filling pipe 11 and used for calculating the filling rate and monitoring the working medium pressure of the measuring point.

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

wherein V ₁ is the volume inside the buffer tank 9;

v _PHP is the total volume of the interior of the pulsating heat pipe;

P ₁ is the internal pressure of the buffer tank 9 before the temperature reduction process begins;

P _1* is the internal pressure of the buffer tank 9 after the cooling process is completed;

ρ _L and ρ _V are the densities of the liquid working medium and the gaseous working medium, respectively, at the saturation temperature;

t ₁ is room temperature;

R is an ideal gas constant.

Further, the temperature acquisition module adopts a platinum resistance thermometer, is arranged on the copper plates of the evaporation section 301 and the condensation section 303 of the low-temperature pulsating heat pipe 3, and is coated with Apiezon N low-temperature vacuum heat-conducting glue to ensure good thermal contact of the two. When in installation, the lead wire is adhered to the surface of the temperature measuring copper plate to be used as a heat sink wire.

In a specific embodiment, as shown in fig. 2 to 4, the invention provides a visual low-temperature pulsating heat pipe experimental device, in order to study the influence of an inclination angle on a pulsating heat pipe, the placement angle of the pulsating heat pipe needs to be changed in the experiment, and a set of angle device capable of changing the inclination angle is designed. The angle adjusting device comprises a frame body 15, a rotating rod 16 and a lifting lug 17, wherein the frame body 15 is arranged outside the vacuum cover 1 and used for supporting the vacuum cover 1, the rotating rod 16 is respectively connected with the frame body 15 and the vacuum cover 1 and is arranged as the rotating center of the vacuum cover 1, and the lifting lug 17 is arranged outside the vacuum cover 1.

Specifically, by setting the angle adjusting device, the inclination angle of the visual low-temperature pulsating heat pipe 3 experimental device can be adjusted, and the visual low-temperature pulsating heat pipe 3 experimental device can be adjusted to a required angle.

In one embodiment, the angle adjusting device further comprises an angle scale 18 and a scale arranged on the angle scale 18, and the angle of inclination of the experimental device of the low-temperature pulsating heat pipe 3 can be visually judged through the position relationship between the angle scale 18 and the scale.

In one application scenario, more than 30 layers of high vacuum multi-layer heat insulating Material (MLI) are used for wrapping the positions where radiation heat leakage needs to be reduced, and the positions specifically comprise the outer surface of the radiation shield 2, the second heat transfer copper plate 305 of the condensing section 303 of the low-temperature pulsating heat pipe 3, the outer surface of the first heat transfer copper plate 304 of the evaporating section 301, the cold head of the refrigerator 6 and the heat conduction heat bridge 7.

In the application scene, the low-temperature heat-insulating multilayer composite material produced by Fushida special materials of Hangzhou is selected, the product uses a polyester film with double-sided aluminizing as a reflecting screen, and the spacing material is a chemical fiber film. In order to reduce the influence of the air release of the high vacuum multilayer heat insulating Material (MLI) on the vacuum degree in the experimental process, the air release device is required to be subjected to drying pretreatment before use so as to remove impurities such as moisture, grease and the like in the multilayer material. The holes on the multi-layer material are punched for air extraction, the number of the holes cannot be excessive, otherwise, the effective radiation area can be reduced, and the heat insulation performance is affected.

Further, openings are formed in the radiation-proof cover 2 and the multi-layer aluminized polyester film corresponding to the visual optical window 101, so that light rays of the light source 4 are ensured to be smoothly emitted to the low-temperature pulsating heat pipe 3, and a high-speed camera can smoothly shoot the gas-liquid flowing process in the low-temperature pulsating heat pipe 3.

In one embodiment, as shown in fig. 8 and fig. 9, in the visual low-temperature pulsating heat pipe experimental device provided in this embodiment, a frame body 15 is disposed outside the vacuum cover 1, and an angle scale 18 is disposed on the frame body 15, so as to intuitively read the inclination angle of the vacuum cover 1. The vacuum cover 1 is symmetrically provided with a visual optical window 101 and a lifting lug 17. The vacuum cover 1 is provided with a flange plate 102, and the flange plate 102 is provided with a refrigerator 6, a KF vacuum connector, an aviation plug and other corresponding auxiliary equipment.

In an application scene, the application field provides an experimental process of the visual low-temperature pulsating heat pipe experimental device, which comprises the following steps:

S1, preparing the visual device, namely connecting and assembling all components of the visual device according to the figure 1, and carrying out vacuum leak detection on the visual device before an experiment by using a helium mass spectrometer leak detector, wherein the visual device comprises a vacuum cover 1, a low-temperature pulsating heat pipe 3, a filling pipe 11 and a buffer tank 9. After ensuring that the room temperature vacuum meets the experimental requirements, the first vacuum pump 12 is started to vacuumize the vacuum cover 1 to 1X 10 ^-4 Pa.

S2, in the purging and purifying process, valves of the buffer tank 9 and the first vacuum pump 12 are opened, valves of the gas tank 10 are closed, the second vacuum pump 13 is opened to vacuumize the low-temperature pulsating heat pipe 3, the buffer tank 9 and the filling pipe 11, and then the valves of the buffer tank 9 and the gas tank 10 are opened, and the valves of the first vacuum pump 12 are closed. After the valve of the gas tank 10 is opened, 99.999% of 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. The above procedure was repeated 5 times to complete the purge purification process.

S3, in the filling process, according to a calculation formula of the filling rate, the required initial filling pressure is estimated, and then valves of the valve buffer tank 9 and the gas tank 10 are opened to close valves of the first vacuum pump 12. The valve of the gas tank 10 is opened, the valve of the gas tank 10 is closed when the pressure sensor shows that the predetermined pressure is reached, the refrigerator 6 is started to cool, and in the process, the valve of the valve buffer tank 9 is closed when the pressure sensor shows that the predetermined pressure is reached, so that both the buffer tank 9 and the gas tank 10 are closed. After the temperature of the low-temperature pulsating heat pipe 3 is stabilized after the cooling process is finished, the liquid filling rate is accurately calculated.

S4, in the experimental process, an angle adjusting device is used for placing the pulsating heat pipe at a specified inclination angle, and a low-temperature pulsating heat pipe 3 performance related experiment is carried out. Dynamic temperature and pressure data of the measuring points are acquired through a control and data acquisition system, and the running condition of the gas-liquid plug of the visual pipe section is shot at a certain frequency through a high-speed camera.

S5, data analysis, namely carrying out experimental result calculation and data analysis according to the data acquired by the control and data acquisition system and the gas-liquid plug running condition, the gas-liquid phase change and the flow pattern transformation shot by the high-speed camera after the experiment is finished.

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

1. by adjusting the liquid filling rate of the working medium and/or the temperature of the condenser of the low-temperature pulsating heat pipe 3, the saturated pressure and the saturated temperature in the working process of the low-temperature pulsating heat pipe 3 can be adjusted and changed, and research under different working conditions can be carried out. And (5) observing the initial distribution condition of gas and liquid in the low-temperature pulsating heat pipe 3 under different liquid filling rates and the working condition after starting.

2. The heating power of the evaporation section 301 is increased step by step, and the influence of the heating power on the heat transfer performance and the thermal-hydrodynamic characteristics, the gas-liquid phase change and the flow pattern conversion of the low-temperature pulsating heat pipe 3 is researched according to the data acquired by the control and data acquisition system and the gas-liquid plug running condition shot by the high-speed camera.

3. By inputting instantaneous heating power, the quench working condition of the superconducting magnet is simulated, and the transient thermal characteristics of the low-temperature pulsating heat pipe 3 are researched.

4. The influence of gravity on the heat transfer performance of the low-temperature pulsating heat pipe 3 and the flow of working media is studied by adjusting the angle of the low-temperature pulsating heat pipe 3.

5. And (3) comparing the pipe diameters of the low-temperature pulsating heat pipes 3, the lengths of the heat insulation sections 302 or the number of loops, and the low-temperature pulsating heat pipes 3 with different geometric parameters to optimize the design of the pulsating heat pipes.

6. In the visual experiment, various gas-liquid phase change forms, flow pattern changes, flow directions and pulsation frequencies which occur in the low-temperature pulsation heat pipe 3 are closely focused, and the flow characteristics and the thermo-hydrodynamic characteristics of the working medium are analyzed.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the embodiments of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

The above embodiments are only for illustrating the present invention, and are not limiting of the present invention. While the invention has been described in detail with reference to the embodiments, those skilled in the art will appreciate that various combinations, modifications, or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and it is intended to be covered by the scope of the claims of the present invention.

Claims

1. Visual low temperature pulsation heat pipe experimental apparatus, characterized by comprising:

The visual low-temperature heat insulation system comprises a vacuum cover and a radiation-proof cover arranged in the vacuum cover, wherein a visual optical window is arranged on the side wall of the vacuum cover, the low-temperature pulsating heat pipe is arranged in a cavity surrounded by the radiation-proof cover, the filling system is arranged outside the vacuum cover and is connected with the low-temperature pulsating heat pipe through a pipeline extending into the vacuum cover and used for filling working media into the low-temperature pulsating heat pipe, the vacuumizing system is respectively connected with the vacuum cover and the low-temperature pulsating heat pipe, and the collecting system comprises a light source and a collecting device which are respectively arranged at two sides of the vacuum cover and correspond to the visual optical window;

The upper part of the vacuum cover is provided with a flange plate, the flange plate is provided with a refrigerator, a cold head of the refrigerator is connected with the low-temperature pulsating heat pipe through a heat conduction heat bridge, and the heat conduction heat bridge is connected with the radiation-proof cover;

The low-temperature pulsating heat pipe comprises a condensing section, a heat insulation section and an evaporating section, wherein the condensing section, the heat insulation section and the evaporating section are arranged from top to bottom along the axial direction of the vacuum cover; the first heat transfer copper plate is fixed with the evaporation section through soldering tin; the heat-conducting device comprises a condensing section, a first heat-conducting copper plate, a second heat-conducting copper plate, a heat-conducting heat bridge, a heat-insulating section, a visual optical window and a visual optical window, wherein the condensing section is fixed with the heat-conducting heat bridge through soldering tin;

the two capillary ports at one end of the condensing section are connected with two ports of a three-way joint, and the other port of the three-way joint is connected with the filling system;

The filling system comprises a buffer tank, a gas tank and a filling pipe, wherein one end of the filling pipe is respectively connected with the buffer tank and the gas tank, and the other end of the filling pipe is connected with the three-way joint;

the vacuumizing system comprises a first vacuum pump and a second vacuum pump, wherein the first vacuum pump is connected with the filling pipe and used for realizing a high-vacuum environment inside the low-temperature pulsating heat pipe;

the visual low-temperature heat insulation system further comprises a hoisting rod which is respectively connected with the radiation-proof cover and the flange plate;

2. The visual low-temperature pulsating heat pipe experimental device according to claim 1, wherein the light source is a cold light element, and the acquisition device is a camera;

And a cover body structure with low light transmittance is arranged between the light source and the acquisition device and between the light source and the corresponding visual optical window, and is used for reducing radiation heat leakage of the room temperature environment to the low-temperature environment inside the vacuum cover through the visual optical window.

3. The visual low-temperature pulsating heat pipe experiment device according to claim 1, further comprising an angle adjusting device for adjusting the angle of the vacuum cover;

the angle adjusting device includes:

and the lifting lug is arranged at the outer side of the vacuum cover.

4. The visual low-temperature pulsating heat pipe experiment device according to claim 1, wherein at least 30 layers of high-vacuum multi-layer heat insulation material are wrapped on 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 heat bridge.