A heat pipe visual measurement system and method

Abstract

The application relates to the technical field of nuclear energy, and particularly discloses a heat pipe visual measurement system and method, which comprises a test box and a visual test platform built in the test box and arranged in a sealed mode; a first containing groove is arranged on the test platform, a first heater is arranged in the first containing groove, and a second containing groove is arranged on the first heater; the heat pipe comprises a pipe shell, a dry channel core and a working medium arranged in the dry channel core; a measuring mechanism for observing the dry channel core of the heat pipe is further arranged in the test box, the measuring mechanism can observe the heat pipe through an observation window arranged on the pipe shell; and in combination with the composite structure sapphire vacuum observation window and the measuring mechanism, the real flow track and liquid film evaporation phase change dynamics of liquid alkali metal on the surface of the dry channel-suction core composite structure can be directly captured under the high-temperature inert safety environment of the test box, and the micro-intermediate visual measurement data blank is filled.

Description

Technical Field

[0001] This invention relates to the field of nuclear energy technology, and in particular to a heat pipe visualization measurement system and method. Background Technology

[0002] High-temperature alkali metal heat pipes, with their advantages of high heat transfer efficiency, simple structure, and passive operation, have become the core heat-conducting element of heat pipe-cooled reactors, providing power support for extreme environments such as deep space and deep sea exploration. They use liquid sodium, potassium, or other metals as working fluids, relying on capillary forces to drive the fluid circulation. However, their heat transfer capacity is limited by factors such as the capillary limit, making it difficult to meet the demands of high-power-density equipment. Therefore, breakthroughs in performance bottlenecks through research at the micro-mesoscopic level are urgently needed. In the field of heat pipe capillary limit research, existing results have significant limitations: while macroscopic experiments can obtain overall heat transfer performance data, they cannot reveal the core heat transfer mechanism of the "drain-wick" composite structure; micro-mesoscopic studies mostly rely on numerical simulations and individual wick experiments, lacking targeted analysis of actual composite structures. The root of this problem lies in the dual constraints of observational conditions: On the one hand, the core size is only about 100 μm, making it difficult for conventional equipment to capture microscopic details; on the other hand, sodium vapor has strong light-blocking properties, resulting in extremely poor light transmittance inside the heat pipe, thus blocking direct observation of the working fluid behavior. Therefore, existing studies cannot intuitively and realistically reflect the flow trajectory of liquid alkali metal on the surface of the core-drain and the liquid film evaporation phase change process, making it difficult to establish a quantitative correlation between "microscopic behavior and macroscopic performance," which restricts the optimization of heat pipe structure and the improvement of heat transfer performance. To address the challenge of visualizing heat pipes, existing technologies have yielded relevant solutions. For instance, Chinese patent CN212567966U discloses a visual experimental device for low-temperature pulsating heat pipes. This device utilizes an adiabatic system consisting of a vacuum hood and a radiation shield, along with a visualization optical window, light source, and acquisition device, to observe the two-phase flow process within a low-temperature pulsating heat pipe. While this device overcomes the visualization barrier in low-temperature environments, it has significant limitations. First, it is applicable only to low-temperature pulsating heat pipes using low-temperature gases such as H2 and Ne, which have vastly different physical properties from the sodium and potassium working fluids of high-temperature alkali metal heat pipes, making it unsuitable for high-temperature (typically >800℃) and highly corrosive environments. Second, the observation focuses on macroscopic flow pattern changes within the capillary, without designing an observation scheme for the micro-mesoscopic scale (μm level) of the "dry channel-wick" composite structure, thus failing to capture the dynamic evolution of microscopic parameters such as liquid film thickness and contact angle. Third, it does not address the issue of light shading by high-temperature alkali metal vapor, making it difficult to directly apply to the observation of the core region of high-temperature alkali metal heat pipes. Furthermore, the patent "CN118294323A, a system and method for measuring the capillary performance and permeability of a sodium alkali metal high-temperature heat pipe wick" published by Xi'an Jiaotong University proposes a system for measuring the capillary performance of a sodium alkali metal high-temperature heat pipe wick. While this system can perform individual performance tests on the wick, it severs the collaborative working relationship between the wick and the main channel, failing to reflect the actual flow and phase change behavior of the working fluid in the composite structure. In summary, existing visualization technologies are either limited by temperature range and working fluid, or lack the ability to observe at the micro-mesoscale, and still cannot meet the needs of studying the micro-mesoscale heat transfer characteristics of the main channel core heat pipe. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a heat pipe visualization measurement system and method to solve the technical problem that existing research on the micro-mesoscopic field of dry core heat pipes cannot truly reflect the key behaviors of liquid alkali metals.

[0004] This invention provides a heat pipe visualization measurement system, comprising: A heat pipe includes a casing and a core, and a working fluid disposed within the core; The test chamber, and the visual test platform built inside the test chamber and in a sealed configuration; The test platform is provided with a first receiving slot, a first heater is provided in the first receiving slot, and a second receiving slot is provided on the first heater; The test chamber is also equipped with a measuring mechanism for observing the core of the heat pipe. The measuring mechanism observes the heat pipe through an observation window opened on the pipe shell.

[0005] Preferably, one end of the heat pipe is fitted with an air gap water cooling jacket, and a chiller and an argon gas tank are connected through the air gap water cooling jacket; The air gap water cooling jacket is provided with a water inlet and a water outlet, as well as an air inlet and an air outlet; The chiller forms a circulating cooling channel through the connection of water pipes to the inlet and outlet; The argon gas cylinder is connected to the inlet and outlet via a gas pipe to form an argon gas protection channel; a liquid controller is installed on the water pipe between the chiller and the water inlet to control the quality and flow rate of the cooling water. An exhaust valve is provided at the end of the air pipe that is connected to the air outlet.

[0006] Preferably, the working fluid filled in the heat pipe is sodium alkali metal, and the dry channel core is a dry channel wire mesh wick. Furthermore, an observation window is provided at the end of the heat pipe on the side facing the main core. The observation window is formed by laser welding two cap-shaped sapphire crystals, which together form a sealed isolation chamber after installation. The isolation chamber contains a protective medium.

[0007] Preferably, a second heater is also provided outside the observation window; The second heater is configured as an MCH alumina ceramic heating tube, and the first heater is configured as a hot runner temperature control copper sleeve; The hot runner temperature control copper sleeve is provided with channels.

[0008] Preferably, the measuring mechanism is connected to an information acquisition board, which is connected to a host computer to acquire the measurement information of the measuring mechanism.

[0009] In another aspect, the present invention provides a method for visually measuring heat pipes, based on the aforementioned system, comprising the following steps: S1. Install the heat pipe on the visualization test platform inside the sealed test chamber, so that the heat pipe is in close contact with the first heater, and construct a high-temperature inert safety observation environment through argon protection and water cooling circulation; S2. Start the first heater and the second heater to heat the alkali metal working medium in the heat pipe to make it undergo phase change and cycle, forming a stable and observable liquid film on the surface of the core. S3. Through the composite sapphire vacuum observation window on the heat pipe shell, the measurement mechanism simultaneously collects image data of the dynamic evolution of the liquid film and temperature and power operating condition data. S4. Reconstruct a 3D model of the core and liquid film based on the collected image data, perform 2D and 3D data measurements on the 3D model of the liquid film, and extract the observation parameters; S5. Based on the observed parameters and corresponding calculation rules, solve for derived parameters such as capillary pressure drop, permeability, gas phase pressure drop, liquid phase pressure drop, and phase interface area; S6. Integrate observation parameters and derived parameters to analyze the flow trajectory and evaporation phase change evolution of the liquid film on the surface of the dry channel-absorbent core composite structure, and establish a quantitative correlation between microscopic behavior and macroscopic heat transfer performance.

[0010] Preferably, step S3 specifically includes: The working fluid is heated by a first heater and undergoes a phase change to form an observable liquid film until it reaches a stable state; The measuring mechanism is activated to simultaneously acquire image data and operating condition data. Adjust the operating conditions according to the preset measurement plan and repeatedly collect the image data and operating condition data; The image data and operating condition data are verified and categorized for storage.

[0011] The heat pipe visualization measurement system and method provided by this invention have the following beneficial effects: In this invention, relying on a composite sapphire vacuum observation window and measurement mechanism, the actual flow trajectory and liquid film evaporation phase change dynamics of liquid alkali metal on the surface of the "main channel-wick" composite structure can be directly captured in the high-temperature inert and safe environment of the test chamber, filling the gap in micro-mesoscopic measured data. At the same time, through the integrated analysis of observation parameters and derived parameters, a quantitative correlation between "microscopic behavior and macroscopic performance" can be established, accurately revealing the heat transfer mechanism driven by capillary force, clarifying the difference in liquid film evolution between the main channel edge and the base layer, and providing a direct theoretical basis for breaking through the capillary limit of heat pipes. In addition, the scheme can reproduce the actual working conditions of heat pipe cooled reactors, and its observation data and mechanism model can directly guide the optimization of the main channel core structure, significantly improving the heat transfer efficiency and power density of high-temperature alkali metal heat pipes, providing key technical support for the engineering application of heat pipe cooled reactors in deep space and deep sea exploration, while avoiding the cognitive biases of existing simulations or individual wick experiments, shortening the research and development cycle and reducing research and development costs. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments of the present invention will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, and these are all within the protection scope of the present invention.

[0013] Figure 1 This is a schematic diagram of the structure of a high-temperature alkali metal heat pipe visualization measurement system; Figure 2 This is another structural schematic diagram of the high-temperature alkali metal heat pipe visualization measurement system; Figure 3 This is a structural schematic diagram of the high-temperature alkali metal heat pipe visualization measurement system from another angle. Figure 4 yes Figure 3 A magnified view of a portion of point A in the middle; Figure 5 yes Figure 4 A schematic diagram of a partial structural cross-section at point B.

[0014] Figure label: 100 - Test chamber, 110 - Test platform, 111 - First receiving tank; 210 - First heater, 211 - Second receiving tank, 220 - Second heater; 310-Heat pipe, 311-Pipe shell, 312-Dry core, 313-Working fluid, 314-Dwelling hole, 315-Observation window, 320-Air gap water jacket, 321-Water inlet, 322-Water outlet, 323-Air inlet, 324-Air outlet, 325-Channel; 400 - Measuring mechanism; 510-Chiller, 511-Liquid Controller, 530-Gas Tank, 531-Gas Pipe, 532-Exhaust Valve; 610 - Host computer, 620 - Power supply, 630 - Information acquisition board. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In the description of the present invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, the element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Where there is no conflict, embodiments of the present invention and the various features thereof can be combined with each other, all of which are within the scope of protection of the present invention.

[0016] Example 1

[0017] In practical engineering applications, the heat transfer capacity of high-temperature alkali metal heat pipes is limited by heat transfer limits such as the capillary limit, making it difficult to achieve efficient operation. Current experimental studies on the capillary limit of heat pipe 310 are mostly focused on the macroscopic level. Due to limitations in experimental conditions, there is relatively little research on the heat transfer characteristics of heat pipe 310 in the micro-mesoscopic realm. Given the small size of the core 312 (only ~100 μm) and the poor light transmittance due to the strong light-blocking properties of sodium vapor, observation is difficult.

[0018] Therefore, existing research on the 312 heat pipe 310 in the micro-mesoscopic field is limited to heat pipe 310 simulation and wicking experiments, which cannot intuitively and realistically reflect the flow of liquid alkali metals on the surface of the wick and the evaporation behavior of the liquid film. The flow of alkali metals on the wick surface and the evaporation behavior of the liquid film significantly affect the heat transfer capacity of the heat pipe 310. Therefore, it is urgent to achieve visualized observation of the flow behavior and liquid film evaporation phase change on the wick surface at the microscale, thereby quantitatively characterizing the maximum heat transfer capacity of the 312 heat pipe 310 and providing key theoretical support for the optimized design and engineering application of high-performance high-temperature heat pipes 310.

[0019] Therefore, this embodiment provides a heat pipe visualization measurement system and method, please refer to [link / reference]. Figures 1-5 The measurement system includes: a test chamber 100 and a sealed visualization test platform 110 built inside the test chamber 100; the test platform 110 is provided with a first receiving groove 111, a first heater 210 is provided in the first receiving groove 111, and a second receiving groove 211 is provided on the first heater 210; the heat pipe 310 includes a shell 311 and a core 312, and a working fluid 313 disposed in the core 312; the test chamber 100 is also provided with a measuring mechanism 400 for observing the core 312 of the heat pipe 310, and the measuring mechanism 400 observes the heat pipe 310 through an observation window 315 opened on the shell 311.

[0020] In this embodiment, the measurement system uses the core working logic of constructing a safe observation environment, triggering the circulation of the working fluid 313 in the heat pipe 310, and realizing microscopic visualization monitoring to achieve the observation of the liquid film behavior of the main channel core 312 by relying on the collaboration of various structures.

[0021] During operation, before system startup, the basic environment setup and structural assembly are completed. The heat pipe 310 is installed as a whole on the first heater 210 of the test platform 110, so that the main body of the heat pipe 310 is adapted to the second receiving groove 211 of the first heater 210, ensuring that the first heater 210 can stably contact the heat pipe 310 and transfer heat. At the same time, the test chamber 100 is sealed to form a sealed environment inside, avoiding external air interference with the high-temperature working fluid 313. The observation end of the measuring mechanism 400 is aligned with the observation window 315 on the shell 311 of the heat pipe 310, and the lens focal length and position are adjusted to ensure that the observation field of view can cover the dry core 312 area inside the heat pipe 310.

[0022] In the experimental environment of this embodiment, the alkali metal working fluid 313 at high temperatures is chemically highly reactive and easily reacts violently with oxygen and water vapor in the air, such as combustion or explosion. The test chamber 100 can be filled with high-purity inert gas (such as nitrogen or argon) and maintained at a slight positive pressure to completely isolate it from the air, thus preventing the working fluid 313 from oxidizing or causing safety accidents. Furthermore, the experiment requires observation of the micron-level liquid film behavior inside the heat pipe 310. Any external dust or impurities entering may contaminate the heat pipe 310 or obstruct the observation window 315. The test chamber 100 needs a highly airtight structure to block the intrusion of external impurities and prevent leakage of internal inert gas, ensuring observation accuracy and environmental stability. The experiment in this embodiment also involves a high-temperature heater and a corrosive working fluid 313. The test chamber 100 is usually made of stainless steel or plexiglass and has heat insulation and corrosion resistance properties.

[0023] Subsequently, the heating system is activated to trigger the circulation of the working fluid 313 in the heat pipe 310; the first heater 210 is energized and heated, transferring heat to the shell 311 of the heat pipe 310. The heat is conducted through the shell 311 to the internal main core 312 and the working fluid 313 inside the main core 312; after absorbing heat, the working fluid 313 undergoes a phase change, vaporizing from liquid to gas. The gaseous working fluid 313 flows along the vapor channel inside the heat pipe 310 towards the lower temperature region. During the flow, some of the gaseous working fluid 313 re-condenses into liquid on the surface of the main core 312, forming a liquid film attached to the main core 312, thus completing the "vaporization-flow-condensation" cycle of the working fluid 313.

[0024] Finally, the measuring mechanism 400 is activated simultaneously to achieve visual observation. When the working fluid 313 of the heat pipe 310 enters a stable state, that is, when the vaporization and condensation rates of the working fluid 313 are balanced and the temperature is stable, the measuring mechanism 400, through the observation window 315 on the shell 311 of the heat pipe 310, penetrates the shell 311 and the possible vapor layer to directly capture the dynamic evolution process of the liquid film on the surface of the core 312, such as the flow, thickness change and evaporation area of ​​the liquid film, and records and stores the observed image data in real time, providing original visual data for subsequent liquid film parameter analysis and evolution law research. Throughout the entire operation, the sealed test chamber 100 continuously ensures the stability of the internal environment, avoids the reaction of the working fluid 313 with the air, and ensures that the measuring mechanism 400 can accurately observe under conditions without external interference.

[0025] Furthermore, in the visualization measurement of high-temperature alkali metal heat pipes, there are problems such as difficulty in condensation control, poor observation environment, and high safety risks. These problems may lead to uncontrolled temperature in the condensation section, and the working fluid 313 inside the heat pipe 310 may be disrupted from vaporization to liquefaction equilibrium. At best, this will cause a sudden increase in pressure and interruption of liquid film circulation due to vapor accumulation, making it impossible to form a stable observation object. At worst, it may cause the heat pipe 310 to burst, causing a safety accident. It may also lead to contamination of the air gap environment, with oxygen in the air reacting with sodium vapor to generate impurities. At the same time, the strong light-blocking property of sodium vapor will completely block the observation light path, making it impossible for the measurement mechanism 400 to capture the microscopic details of the liquid film in the core 312, rendering the visualization experiment meaningless.

[0026] Furthermore, one end of the heat pipe 310 is fitted with an air gap water cooling jacket 320, and a chiller 510 and an argon gas tank 530 are connected through the air gap water cooling jacket 320; the air gap water cooling jacket 320 is provided with a water inlet 321 and a water outlet 322, as well as an air inlet 323 and an air outlet 324; the chiller 510 forms a circulating cooling channel by connecting the water inlet 321 and the water outlet 322 through a water pipe; the argon gas tank 530 forms an argon gas protection channel by connecting the air inlet 323 and the air outlet 324 through a gas pipe 531; a liquid controller 511 is provided on the water pipe between the chiller 510 and the water inlet 321 to control the mass and flow rate of the coolant; an exhaust valve 532 is provided at the end of the gas pipe 531 connected to the air outlet 324.

[0027] In this embodiment, the temperature of the condensation section is precisely controlled by the circulating cooling channel to ensure the "vaporization-liquefaction" balance of the working fluid 313, maintain the steady-state circulation of the heat pipe 310, and provide stable operating conditions for liquid film observation. The argon gas protection channel fills the air gap, which not only isolates the air to prevent the sodium working fluid 313 from reacting, but also uses the low optical absorption characteristics of argon gas to reduce the obstruction of light by vapor, thereby improving the clarity of observation. At the same time, water cooling quickly dissipates heat to prevent the tube shell 311 from overheating, and the argon gas flow promptly discharges leaked vapor. Combined with pressure regulation, this ensures the safety of the high-temperature and high-activity working fluid 313 experiment. This is a key design for connecting the stable operation of the heat pipe 310 and microscopic visualization observation.

[0028] During operation, the chiller 510 pumps coolant into the internal flow channel of the air-gap water-cooled jacket 320 through the inlet 321 via water pipes. The coolant absorbs heat in the air-gap region between the jacket and the heat pipe 310 shell 311, primarily from the condenser section of the heat pipe 310. The coolant then flows back to the chiller 510 from the outlet 322, forming a closed-loop circulation that continuously removes heat transferred from the heat pipe 310 to the condenser section. The liquid controller 511 adjusts the coolant flow rate and pressure in real time to ensure the cooling rate matches the heat output of the heat pipe 310.

[0029] The argon gas tank 530 fills the air gap space of the air gap water jacket 320 through the gas pipe 531 and the gas inlet 323, filling the gap between the heat pipe 310 shell 311 and the inner wall of the water jacket. Then the argon gas is discharged from the gas outlet 324 through the gas pipe 531. The exhaust valve 532 can adjust the exhaust rate to maintain the slight positive pressure flow of argon gas in the air gap to prevent outside air from seeping in.

[0030] The evaporation section of the heat pipe 310 is heated by the first heater 210. After the working fluid 313 is vaporized, it flows to the other end (the condensation section fitted with the air gap water cooling jacket 320). The gaseous working fluid 313 releases heat and liquefies in the condensation section. The liquefied liquid film flows back to the evaporation section by the capillary force of the main channel core 312, completing the cycle. The air gap water cooling jacket 320 ensures the stable operation of the condensation section through the dual functions of water cooling and argon gas isolation, while providing a clean environment for the observation window 315 area.

[0031] Specifically, the circulating cooling channel, through the collaboration of the chiller 510 and the liquid controller 511, can precisely regulate the temperature of the condensing section, such as stabilizing the condensing temperature of the sodium working fluid 313 at 200-300℃, ensuring the "vaporization-condensation" balance of the working fluid 313 in the heat pipe 310, avoiding steam accumulation and sudden pressure rise due to insufficient condensation, or excessive condensation causing the liquid film to be too thick and block the steam channel, thus providing a stable operating condition basis for dynamic observation of the liquid film.

[0032] Furthermore, its argon gas protection channel fills the gas gap with inert gas, which on the one hand isolates the air (to prevent the heat pipe 310 shell 311 from oxidizing and sodium vapor from reacting with oxygen), and on the other hand utilizes the low optical absorption characteristics of argon gas to reduce the scattering and obstruction of the observation light by the vapor in the gas gap. Together with the observation window 315, it forms a clean and observable optical path, ensuring that the measurement mechanism 400 can clearly capture the details of the liquid film on the surface of the core 312.

[0033] During operation, the air gap water cooling jacket 320 can quickly remove heat through the flow and circulation of coolant, preventing the condensation section temperature from being too high and causing the tube shell 311 to overheat. The continuous flow of argon gas can promptly discharge any trace amounts of sodium vapor that may leak (which poses no risk of explosion when mixed with argon gas). The exhaust valve 532 can regulate the system pressure and prevent abnormal pressure fluctuations in the air gap, thus improving the overall safety of experiments involving high-temperature and highly reactive working fluids 313. This part of the structure provides stable condensation conditions and a safe environment for the heat pipe 310, and also removes vapor interference obstacles for micro- and meso-scale observations. It is a key bridge connecting the operation of the heat pipe 310 with visualization measurements.

[0034] Furthermore, in terms of the design of the experimental section, a shell with a length of 280mm, an inner diameter of 19mm, and an outer diameter of 21mm was designed as the outer shell of the heat pipe 310.

[0035] The wick is a single-channel wire mesh wick filled with sodium alkali metal as the working fluid 313. This unique structural design helps to provide a more stable and efficient channel for the reflux of the working fluid 313, thereby effectively reducing a series of problems caused by poor reflux of the working fluid 313, such as performance degradation or failure of the heat pipe 310, thus making the experimental results more reliable and reproducible.

[0036] Meanwhile, at the end of heat pipe 310, 5cm from the endpoint, on the side facing the main channel, an 8mm observation window 315 and a placement hole 314 are laser-cut. Using laser cutting offers several advantages: it effectively reduces the impact of the experimental section's processing on the structural strength of heat pipe 310. This structural design allows the experimental section to well meet various experimental requirements, avoiding unnecessary complexity due to excessive length and significantly reducing experimental costs. Furthermore, this design reduces space requirements, enabling experimental operations to be performed within a glove box, thereby further increasing safety during the experiment and providing a solid guarantee for its successful execution.

[0037] Furthermore, the observation window 315 is formed by laser welding two cap-shaped sapphire crystals, which together form a sealed isolation chamber after installation, and the isolation chamber contains a protective medium.

[0038] The composite sapphire vacuum observation window 315 uses a precision laser welding process to seal and weld two cap-shaped sapphire vacuum observation windows 315 together to form a sealed chamber, which is then filled with a protective medium, namely the inert gas argon.

[0039] Specifically, the laser welding has minimal impact on the overall performance of the observation window 315, effectively maintaining the original strength and optical properties of the material, thus ensuring the functionality and lifespan of the observation window 315. The chemical inertness of argon gas creates an efficient barrier, ensuring the structure's airtightness and chemical stability, allowing it to maintain its performance and structural integrity for extended periods. It can also operate reliably in complex environments. Furthermore, the argon gas barrier reliably prevents sodium vapor from seeping out from any possible tiny gaps, ensuring the safety of the operating environment and the accuracy of observations. It avoids adverse effects such as corrosion of surrounding equipment and obstruction of the observation line caused by sodium vapor leakage. The stable and pure internal chamber environment created by argon gas ensures that observations through sapphire are not affected by changes in external air composition or impurities, maintaining a clear field of view at all times. This helps to more accurately observe the phase distribution and evolution process of sodium within the core 312 through the observation window 315.

[0040] Furthermore, due to the high operating temperature of the high-temperature sodium heat pipe 310, the increased sodium vapor concentration in the steam cavity causes a significant increase in light depth. Based on the light absorption principle of Lambert-Beer law, the increased light depth leads to an exponential decrease in the transmittance of the visible light band, thereby significantly reducing the light transmittance of the steam cavity to the point that it cannot be visualized.

[0041] The composite sapphire vacuum observation window 315 is positioned inside the heat pipe 310, close to the main core 312. This serves two purposes: firstly, it avoids the impact of sodium vapor condensation on the visible upper surface of the observation window 315 on visualization; secondly, the internal temperature of the heat pipe 310 is higher than the sodium vapor condensation temperature, preventing sodium vapor condensation on the visible lower surface; and finally, the composite sapphire vacuum observation window 315 can effectively reduce the impact of high-concentration sodium vapor on visualization, thereby enabling the observation of the liquid film distribution morphology and evolution characteristics within the capillary structure of the high-temperature alkali metal heat pipe main core 312.

[0042] After the addition of the sapphire vacuum observation window 315, the first heater 210 and the second heater 220 can no longer use the traditional electric heating wire heating method to heat the entire experimental section. Therefore, a hot runner temperature-controlled copper sleeve and MCH alumina ceramic heating tube 310 are used in conjunction with a precision temperature control system for partial heating.

[0043] First, an MCH alumina ceramic heating tube 310 is installed outside the observation window 315. Before the experimental section is heated, the temperature of the observation window 315 is maintained at 450℃ by precise temperature control, so as to prevent sodium vapor from condensing on the visible surface of the observation window 315 during the heating process of the experimental section. Secondly, a hot runner temperature control copper sleeve is used to heat the evaporation section. Since the hot runner temperature control copper sleeve has a 12mm wide and 180mm long groove 325, the entire experimental section evaporation section can be heated evenly while avoiding the observation window 315.

[0044] Specifically, the hot runner temperature control copper sleeve has a temperature resistance of 600℃, a maximum heating power of 700W, and a maximum heater temperature of 600℃. The heater temperature can be controlled by adjusting the power. The MCH alumina ceramic heating tube 310 has the characteristics of high temperature resistance (greater than 500℃), good insulation, and excellent heating performance. This temperature resistance is higher than the condensation temperature of sodium vapor, which can effectively prevent sodium vapor from condensing on the visible surface of the observation window 315, avoid the impact of sodium vapor condensation on the visible surface of the observation window 315 on the visual observation, and ensure that the observation field of view remains clear.

[0045] Furthermore, the measuring mechanism 400 is connected to an information acquisition board 630, which is connected to a host computer 610 to obtain the measurement information of the measuring mechanism 400.

[0046] Specifically, the core function of the host computer 610 and the acquisition board is to construct a data transmission and processing link for measurement, acquisition, and analysis, enabling real-time integration and in-depth analysis of liquid film observation data. Specifically, the liquid film image data captured by the measurement mechanism 400 and the physical quantity data collected by the operating condition sensors need to be summarized and format-converted by the information acquisition board 630 before being transmitted to the host computer 610. The host computer 610, as the data processing core, can display measurement data in real time, store original images and operating condition records, and, relying on its built-in software, complete 3D model reconstruction, parameter extraction, and derived parameter calculation, providing data support for subsequent analysis of the liquid film evolution law.

[0047] Before use, the image output terminal of the measuring mechanism 400 and the signal terminals of various sensors need to be connected to the corresponding interfaces of the information acquisition board 630. Then, the acquisition board is connected to the host computer 610 via a data cable, and the parameters (such as data sampling frequency and storage path) are configured in the software.

[0048] During the experiment, the system automatically starts synchronous acquisition. The acquisition board receives and converts data in real time, and the host computer 610 displays dynamic images and operating condition curves synchronously. Operators can monitor the integrity of the data through the host computer 610. After the experiment, the host computer 610 automatically saves all data and supports subsequent calls to analysis software for parameter extraction and pattern summarization, realizing fully automated processing from raw measurement to data application.

[0049] Example 2

[0050] In this embodiment, a test chamber 100 is provided. The test chamber 100 needs to meet four core working conditions: inert isolation, high airtightness, safety protection, and observation compatibility. That is, it can isolate air (to prevent oxidation of alkali metal working medium 313), maintain a clean and impurity-free internal environment (to avoid obstructing observation), withstand high temperature and corrosion (to adapt to the experimental conditions of heat pipe 310), and at the same time have a transparent observation area (to match the imaging requirements of measurement mechanism 400).

[0051] Specifically, optional equipment includes glove boxes, inert gas protection boxes, and vacuum drying ovens. While inert gas protection boxes can provide an inert environment, they lack operational flexibility and cannot adjust experimental components in real time. Vacuum drying ovens focus on a vacuum environment, making them unsuitable for scenarios requiring dynamic filling of protective gas, and their observation windows are limited, thus failing to fully meet experimental needs.

[0052] In this embodiment, a glove box is selected as the test chamber 100 of this scheme. The glove box can maintain a high-purity inert environment for a long time (nitrogen / argon can be replenished in real time, and the oxygen content is ≤1ppm), avoiding the reaction between sodium working fluid 313 and air; and it is equipped with sealed operating gloves, which can flexibly adjust the position of heat pipe 310, measuring mechanism 400 lens, etc. without damaging the inert environment, to meet the dynamic intervention needs during the experiment; and the sides of the glove box are generally made of transparent plexiglass, which can provide a large unobstructed observation field, suitable for the microscopic observation of the observation mechanism in this embodiment; it can also isolate the high temperature of heat pipe 310 and the working fluid 313 that may leak, ensuring experimental safety.

[0053] Specifically, before the experiment, the glove box is filled with high-purity inert gas (such as argon) through the air intake system, while the exhaust system is turned on to expel the air inside the box until the oxygen content and humidity drop to the experimental requirements. During the experiment, a slight positive pressure is maintained inside the box to prevent outside air from seeping in. The operator adjusts the position of the heat pipe 310, heater, and measuring mechanism 400 through sealed gloves to ensure that the observation field covers the core area 312. The measuring mechanism 400 captures dynamic images of the liquid film through the transparent wall of the glove box and the observation window 315 of the heat pipe 310. Any trace impurities or leaked working fluid 313 generated during the experiment can be discharged in a timely manner through the inert gas circulation system, ensuring the stability and safety of the experimental environment throughout the process.

[0054] Example 3

[0055] In this embodiment, a chiller 510 is provided, which can precisely adjust the cooling water temperature with a temperature difference fluctuation of ≤±2℃ to adapt to the temperature control requirements of the condensing section of the heat pipe 310, such as stabilizing the condensing temperature of the sodium working fluid 313 at 200-300℃; and the chiller 510 needs to support dynamic adjustment of the cooling water flow rate (0.5-5L / min), so that the flow rate can be increased or decreased when the heater power increases or decreases, in order to match the heat dissipation requirements of the heat pipe 310 under different power conditions.

[0056] The chiller 510 needs to quickly remove the heat released by the condenser section of the heat pipe 310 during operation to ensure that the temperature of the condenser section is stable within the target range and maintain the "vaporization-liquefaction" balance of the working fluid 313; avoid the sudden increase in steam pressure inside the pipe due to insufficient cooling, or the blockage of the steam passage by the liquid film due to excessive cooling, so as to provide a stable operating condition basis for liquid film observation.

[0057] Generally, water-cooled chillers (510) use an external water source and have high cooling efficiency, but they rely on external tap water or industrial water sources, have complex piping layouts, and the water quality is easily contaminated by the air gap water cooling jacket (320) flow channel, resulting in high maintenance costs. Semiconductor chillers (510) are small in size and have low noise, but their cooling capacity is limited (usually <500W), which cannot meet the heat dissipation requirements of high-temperature heat pipes (310) that may have a power of several kW. Constant temperature circulating water baths have high temperature control accuracy, but their flow rate adjustment range is narrow, and the water bath medium (such as water) is prone to level fluctuations due to high-temperature evaporation, resulting in insufficient stability.

[0058] Therefore, in this embodiment, an air-cooled chiller 510 is selected. The air-cooled chiller 510 has strong independent operation and does not require an external water source. It achieves heat exchange through a built-in fan and heat sink, and can be placed directly outside the glove box, simplifying the pipeline layout and adapting to the flexible layout requirements of the laboratory. Moreover, the cooling capacity of a single unit can reach 1-10kW, which can cover the heat dissipation requirements of the heat pipe 310 from low power (300W) to high power (5000W), and the flow rate adjustment range is wide (0.8-8L / min). The operating conditions can be accurately matched through the liquid controller 511.

[0059] In this embodiment, the air-cooled chiller 510 adopts a PID temperature control algorithm. When the power of the heat pipe 310 changes abruptly, it can adjust the cooling water temperature to the target value within 30 seconds to avoid the temperature fluctuation of the condensation section affecting the stability of the liquid film. The water circuit system of the air-cooled chiller 510 is closed, reducing the intrusion of impurities. Moreover, the air-cooled heat dissipation does not require regular replacement of the coolant, only the filter screen needs to be cleaned, making it suitable for long-term continuous experiments.

[0060] Before the experiment, the outlet 322 of the chiller 510 is connected to the inlet 321 of the air gap water jacket 320 via a water pipe, and the return outlet is connected to the outlet 322 of the water jacket to form a closed loop. The target water temperature and initial flow rate are preset on the control panel of the chiller 510 and linked with the host computer 610 through the liquid controller 511. During the experiment, when the power of the heat pipe 310 increases, the host computer 610 instructs the liquid controller 511 to increase the flow rate, and the chiller 510 automatically increases the cooling power to ensure the cooling water temperature is stable. After the experiment, the heating system is turned off first, and after the temperature of the heat pipe 310 drops to room temperature, the chiller 510 is turned off, and the residual cooling water in the pipeline is drained to avoid corrosion.

[0061] Example 4

[0062] This embodiment provides a measurement mechanism 400. The measurement mechanism 400 must meet the following conditions and achieve the following measurement effects: It needs to be able to clearly capture micron-level details (core 312 scale ~100μm, liquid film thickness may be as low as several μm), and must have a spatial resolution of ≥1μm; to adapt to the dynamic process of liquid film flow and evaporation, its acquisition frequency needs to be ≥0.5 frames / second (matching the liquid film evolution rate), and it must be able to continuously record stable data for at least 10 minutes; it also needs to withstand the inert gas environment inside the glove box, the lens needs to be resistant to high-temperature radiation (to avoid heat pipe 310 heat dissipation affecting imaging), and the optical path needs to penetrate the observation window 315 and the sodium vapor layer to reduce light attenuation. The required measurement effect is: to intuitively present the 2D and 3D morphology of the liquid film on the surface of the core 312, ensuring accurate extraction of microscopic parameters such as contact angle and curvature, with a contact angle error ≤±2° and a length / height error ±5%, providing the original basis for the calculation of derived parameters.

[0063] Generally, a combination of a high-speed camera and a microscope lens can be used. Although it can capture dynamic images, it lacks 3D modeling capabilities and cannot directly measure three-dimensional parameters such as liquid film height and volume. It needs to rely on post-processing algorithms for calculation, resulting in lower accuracy. Laser confocal microscopes have high resolution (up to 0.1 μm), but slow acquisition speed (usually <0.1 frames / second), making it difficult to track the dynamic evolution of the liquid film. Furthermore, the laser is easily affected by sodium vapor scattering. Interference microscopes can calculate the liquid film thickness through interference fringes, but they are sensitive to vibration (glove box operation may cause micro-vibrations) and require strict control of optical path stability, resulting in poor adaptability.

[0064] In this embodiment, the measuring mechanism 400 adopts a 3D ultra-depth-of-field microscopic measuring system. This system can directly generate 3D models of the liquid film and the core 312 through multi-view image fusion and depth-of-field extension technology, obtaining parameters such as height and volume without algorithm calculation, with an accuracy improved to ±1μm. The acquisition frequency is adjustable (0.5-10 frames / second), which can capture the dynamic process of liquid film flow and obtain high-resolution static details in steady state, adapting to multi-stage observation needs. The lens is equipped with an anti-reflective coating and a high-temperature protective cover to reduce the influence of sodium vapor scattering and heat pipe 310 radiation, and has a large depth of field (usually >500μm), which can penetrate the observation window 315 and the vapor layer for clear imaging. It also supports direct docking with the information acquisition board 630 to realize synchronous storage of image data and operating condition data, which is convenient for subsequent parameter integration and analysis. Usage: Before the experiment, fix the system lens inside the glove box, align it with the observation window 315 of the heat pipe 310, and adjust the focus and field of view through the sealed gloves to ensure that the core area 312 is completely covered; preset the acquisition parameters on the software (such as 2 frames / second, continuous acquisition for 10 minutes) and synchronize the time axis with the host computer 610.

[0065] During the experiment, the system automatically acquired liquid film images at a preset frequency and transmitted them in real time to the information acquisition board 630. After conversion, the images were uploaded to the host computer 610 to generate a dynamic 3D preview. After the experiment, the system software extracted 2D and 3D parameters (including but not limited to 2D parameters such as liquid film area, length, width, and wire diameter, aperture, and area of ​​the mesh; and 3D parameters such as liquid film height, phase interface area, curvature, and contact angle) and exported the raw data for the calculation of derived parameters and the analysis of evolution laws.

[0066] Example 5

[0067] This embodiment provides a method for operating the measuring mechanism 400 of the high-temperature alkali metal heat pipe visualization measurement system described in Embodiments 1-4. The measuring mechanism 400 includes: Acquire image data and operational data of the dynamic evolution of the liquid film; Specifically, before the experiment, the hardware link needs to be set up. The image output end of the 3D ultra-depth microscopic measurement system (measuring mechanism 400), the temperature sensor of the evaporation / condensation section of the heat pipe 310, and the power meter of the first heater 210 are respectively connected to the corresponding interface of the information acquisition board 630. Then, communication is established between the acquisition board and the host computer 610. The time axis of each device is synchronized in the software with an error of ≤0.1 seconds to ensure that the data timestamps are consistent.

[0068] When the heat pipe 310 is heated to the target steady state by the first heater 210 (temperature fluctuation ≤ ±5℃, power fluctuation ≤ ±10W), the host computer 610 sends a synchronous acquisition command, and the measuring mechanism 400 starts shooting according to the preset parameters. The lens focuses on the core 312 area through the observation window 315 to capture dynamic images of liquid film flow, thickness change and phase interface evolution. At the same time, the temperature sensor collects one set of evaporation section / condensation section temperature data per second, and the power meter synchronously records the real-time power of the heater. The two types of operating condition data are converted by the acquisition board and then bound to the image data for storage.

[0069] During the data acquisition process, the host computer 610 displays the image stream and operating condition curves in real time. The operator monitors the data integrity through software, such as whether there are any image frame drops or whether the sensor signals are normal. If an anomaly occurs, such as fogging of the observation window 315 causing the image to become blurry, the operator adjusts the power of the second heater 220 (heating the observation window 315 to remove fog) through the glove box and marks the abnormal period. After the data returns to normal, the corresponding interval data is reacquired to ensure the validity of the original data.

[0070] After the data acquisition is completed, the system automatically stores the image data and operating condition data into the host computer 610 hard drive according to the operating condition number and parameter type. At the same time, it generates an acquisition log to provide a complete basis for subsequent data integration and analysis.

[0071] Generate a 3D model of the main channel core 312 and the liquid film based on the image data and through the system software; Specifically, generating a 3D model of the main channel core 312 and the liquid film is achieved through the multi-view image fusion, depth of field extension, and three-dimensional coordinate mapping processes of the three-dimensional reconstruction software supporting the 3D ultra-depth-of-field microscopy system.

[0072] The drawing software first preprocesses the collected sequence images, including noise removal, image alignment. Based on the screen texture features of the main channel core 312, it automatically corrects the image offset caused by minute vibrations, ensuring that the field of view benchmarks of all images are consistent, enhancing the contrast, highlighting the gray-scale difference between the liquid film and the main channel core 312, and making the edge of the liquid film clearer; then, aiming at the problem of local defocus of a single image caused by the height difference between the liquid film and the main channel core 312, the software extracts clear regions (such as the liquid film surface, the root of the screen) from images with different focal lengths through the depth-of-field synthesis algorithm, and fuses them to generate a 2D stitched image with a clear full field of view; meanwhile, it automatically identifies feature points and marks their pixel coordinates in the 2D image.

[0073] Furthermore, based on the optical parameters preset in the system, such as lens focal length, object distance, magnification, the software converts the pixel coordinates of the 2D feature points into three-dimensional space coordinates; through dense feature point fitting, it generates a three-dimensional grid model of the screen of the main channel core 312, restoring the wire diameter, aperture, and spatial distribution; meanwhile, according to the gray-scale gradient and height mapping relationship of the liquid film region, it reconstructs the 3D surface morphology of the liquid film; the software automatically removes abnormal points of false features such as those caused by steam interference in the model, and optimizes the continuity of the liquid film surface through a smoothing algorithm; finally, it generates a rotatable and locally magnifiable 3D model, supporting export in STL format or binding to dynamic models of working conditions data to visually display the morphological changes of the liquid film at different times; through this process, the two-dimensional image data is converted into a three-dimensional model containing spatial depth information, providing an intuitive and accurate digital carrier for subsequent extraction of key parameters such as the height and phase interface area of the 3D model.

[0074] Measure and extract the observation parameters of the 3D model based on the 3D model and through the system software; Specifically, when using the software's built-in measurement tools to extract observation parameters from the 3D model, first load the generated 3D models of the main channel core 312 and the liquid film into the software, then call the "feature recognition tool" to automatically mark key areas, such as the contact boundary between the liquid film and the main channel core 312, and the highest point of the liquid film. Then, select the appropriate tool according to the measurement requirements. If measuring the height of the 3D model, use the "height measurement tool," select any point in the liquid film area on the model, and the tool automatically calculates the difference between the Z-axis coordinate of that point and the Z-axis coordinate of the main channel core 312 surface, supporting multi-point measurements and generating an average value. If measuring the connection... For contact angle measurement, the "Angle Measurement Tool" is used. At the intersection of the liquid-solid interface and the gas-liquid interface, the tool automatically fits the tangent of the liquid film surface and the normal of the 312 core surface, and displays the contact angle value in real time. If measuring the phase interface area, the "Area Calculation Tool" is used. The gas-liquid interface area is selected, and the tool obtains the area value through the surface mesh integration algorithm. During all measurements, the tool automatically masks abnormal noise in the model. After the measurement is completed, a model screenshot with measurement marks and a parameter table are generated and directly exported to the storage directory of the corresponding working condition, ensuring seamless connection between parameter extraction and classified storage.

[0075] The derived parameters of each observation parameter are calculated based on the calculation rules corresponding to each observation parameter. Specifically, the calculation rules for each derived parameter are first clarified (e.g., calculating volume based on liquid film area and height, and calculating capillary pressure by combining contact angle and wire diameter). Then, the parameter calculation module of the system software is called to import the extracted 2D and 3D basic observation parameters of the liquid film (area, height, contact angle, etc.) and the wire mesh geometric parameters (wire diameter, pore size). The software automatically calculates according to preset rules to generate derived parameters such as liquid film volume, capillary pressure, and evaporation rate. After the calculation is completed, the derived parameters are bound and stored with the basic parameters to provide richer quantitative evidence for subsequent mechanism analysis.

[0076] The observed parameters and derived parameters are integrated and the evolution of the liquid film is analyzed. Specifically, the observed parameters and derived parameters are first integrated into a unified data table according to the working condition number, and the same timestamp and structural location information are linked through system software. Then, with the working condition variable as the horizontal axis, the curves of each parameter changing with time are plotted to compare and analyze the parameter differences at different capillary structure locations. For example, the stability of the "capillary-driven-evaporation balance" of the trunk road base is judged by the matching degree between the liquid film volume change and the evaporation rate. At the same time, key influencing factors are screened by combining dimensionless numbers, and finally the evolution law such as "power increase → capillary pressure increase → liquid film expansion rate accelerates, but evaporation loss dominates under high power → liquid film thickness tends to stabilize" is summarized, clarifying the core control mechanism of liquid film evolution at different structural locations.

[0077] Furthermore, the observation parameters include, but are not limited to, the area, length, and width of the 2D model of the liquid film, and the wire diameter, aperture, and area of ​​the mesh; and the height, interface area, curvature, and contact angle of the 3D model of the liquid film. Furthermore, acquiring image data and operating condition data of the dynamic evolution of the liquid film includes: The working fluid 313 is heated by the first heater 210 and undergoes a phase change to form an observable liquid film to a stable state; Specifically, the first heater 210 continuously heats the evaporation section of the heat pipe 310. The heat is conducted through the shell 311 to the alkali metal working fluid 313 in the main core 312. The working fluid 313 absorbs heat and vaporizes from a liquid state to a gaseous state and flows into the condensation section. The gaseous working fluid 313 releases heat in the condensation section and then re-liquefies, forming a liquid film attached to the surface of the main core 312. During the process, the power of the first heater 210 is adjusted (e.g., gradually increased to the target power) and the temperature is monitored (the temperature of the evaporation section and the condensation section is collected in real time). When the liquid film flow state (e.g., flow speed, thickness change) and the system temperature (fluctuation range ≤ ±5℃) remain stable for a preset time, such as 10 minutes, it is determined that the liquid film has reached an observable stable state.

[0078] The measuring mechanism 400 is activated to simultaneously acquire image data and operating condition data. Specifically, once the liquid film reaches a stable state, the host computer 610 issues a synchronous acquisition command, triggering the 3D ultra-depth-of-field microscopy system to start image acquisition according to preset parameters. The lens focuses on the core area 312 through the observation window 315, capturing the flow, phase change, and morphological changes of the liquid film in real time. At the same time, the temperature sensor and power meter synchronously acquire operating data at intervals of 1 second / group. All image data and operating data are aggregated by the information acquisition board 630, bound with the same timestamp, and uploaded to the host computer 610 for storage, realizing real-time linkage recording of dynamic images of the liquid film with operating parameters such as temperature and power.

[0079] Adjust the operating conditions according to the preset measurement plan and repeatedly collect the image data and operating condition data; Specifically, according to the preset operating condition gradient, such as heating power from 300W to 1500W, with each 200W increment, the power of the first heater 210 is adjusted via DC, and the cooling water flow rate of the air gap water cooling jacket 320 is simultaneously adjusted to match the current power. Once the temperature and liquid film state of the heat pipe 310 reach a new steady state, such as fluctuations ≤ ±5℃ and lasting for more than 10 minutes, the measuring mechanism 400 is repeatedly started to collect liquid film images and temperature and power data under the same operating condition according to the same standard. The data is then matched and classified according to the operating condition number and parameter type and stored until all preset gradient operating condition data are collected, thus achieving comparative recording of the dynamic evolution of the liquid film under different operating conditions.

[0080] The image data and operating condition data are verified and categorized for storage; Specifically, after data acquisition, the image data is verified for clarity using the 610 host computer software: checking for blurring or obstruction caused by steam interference or lens defocusing, and removing invalid images. Continuity verification of the operating data is also performed: checking for gaps or abnormal jumps in temperature and power data, marking suspicious data, and supplementing the data collection. After successful verification, the valid image data (in TIFF format) and operating data (in CSV format) are classified and stored on the 610 host computer hard drive according to the hierarchical structure of "operating condition number-timestamp-parameter type". At the same time, a verification log is generated to record data integrity, anomaly handling, and storage path, ensuring that the complete data for the corresponding operating condition can be quickly retrieved during subsequent analysis.

[0081] Furthermore, the calculation of derived parameters for each observation parameter based on the calculation rules corresponding to each observation parameter includes: The curvature radii of the two principal curvature directions of the liquid film interface can be calculated by measuring the curvature, and then the capillary pressure drop can be calculated by combining the curvature radii with the surface tension coefficient of the working fluid 313. Alternatively, the capillary pressure drop can be calculated by measuring the contact angle between the liquid film and the core 312, the wire diameter, and the mesh aperture, combined with the surface tension coefficient of the working fluid 313. Specifically, two orthogonal curve images were taken at the apex of the liquid film using a microscope. Data at several (x, y) points on the curve were measured experimentally. The measured data were then simulated using MATLAB to obtain... , Two polynomial curve equations. The radii of curvature in the two principal curvature directions are obtained using the radius of curvature formula from the curve equations.

[0082] in, , , In the formula, , The polynomial curve equation obtained from scatter data simulation; and Let be the radius of curvature of the interface in the two principal curvature directions (unit: m).

[0083] Furthermore, when the liquid film shape is a simple geometric shape (such as a multidimensional curved surface), the capillary pressure drop calculation formula is: ; In the formula For capillary force; The surface tension coefficient of the given working fluid is 313 (unit: N / m). , The radius of curvature of the interface in the two principal curvature directions (unit: m); , Obtained through experimental measurements.

[0084] Furthermore, when the liquid film has an irregular shape, the formula for calculating the capillary pressure drop is: ; In the formula For capillary force; The surface tension coefficient of the given working fluid 313 (unit: N / m) can be obtained experimentally. ; The contact angle between the liquid film and the wicking material; The diameter of the wire; Mesh aperture; , and Obtained through experimental measurements.

[0085] The permeability of the core 312 can be calculated by combining the measured wire diameter and mesh size with existing mesh count data. Specifically, permeability is a parameter that measures the ability of porous media (such as wire mesh cores, absorbent cores, etc.) to allow fluid to pass through, and its unit is 1000 kJ / m². Its value depends on the pore structure, fluid properties, and the interaction between the medium and the fluid.

[0086] The formula for penetration rate is: , , In the formula This is the mesh count of the wire mesh (taken as 3937 holes / m). The diameter of the wire (which can be measured experimentally); Porosity; The mesh size is the wire mesh opening (which can be measured experimentally).

[0087] The vapor phase pressure drop of the working fluid 313 was calculated by measuring the height of the liquid film 3D model, combined with the heating power, vapor phase density, vapor phase dynamic viscosity, evaporation section length, adiabatic section length, condensation section length, and heat pipe 310 inner diameter. By measuring the axial temperature distribution of the experimental section of heat pipe 310, the corresponding saturated vapor pressure can be found, thus obtaining the total resistance pressure drop. Then, the liquid phase pressure drop of working fluid 313 can be obtained from the total resistance pressure drop and the vapor phase pressure drop of working fluid 313. Specifically, in a saturated state within the steam chamber, the saturated vapor pressure corresponds one-to-one with the temperature. The saturated vapor pressure corresponding to the temperatures of the evaporation and condensation sections can be found in a chemical handbook; the difference between the two is the total pressure drop.

[0088] The formula for total resistance pressure drop is: ; In the formula Total pressure drop; This is the saturated vapor pressure of the evaporation section; This is the saturated vapor pressure of the condensation section.

[0089] When heat pipe 310 is operating stably, the formula for calculating the total vapor phase pressure drop using the laminar flow formula is as follows: ; In the formula The pressure drop of the working fluid 313 vapor phase; The density of the vapor phase; The dynamic viscosity of the vapor phase; This refers to the length of the evaporation section; This refers to the length of the insulation section; This refers to the length of the condensation section; The heat pipe has an inner diameter of 310 mm. The height of the liquid film 3D model; Effective heating power; Vaporization potential of working fluid 313 (unit: KJ / kg); For the middle is the mass flow rate of the working fluid inside the heat pipe (unit: kg / s), and 8 is the inherent coefficient of the Hagen-Poiseuille laminar pressure drop formula.

[0090] The difference between the total pressure drop and the total pressure drop of the vapor phase is the liquid phase pressure drop, and the formula is: ; In the formula This refers to the liquid phase resistance pressure drop; Total pressure drop; The pressure drop of the working fluid 313 vapor phase.

[0091] Furthermore, the change in height of the liquid film 3D model with power can be calculated from the changes in height and power of the liquid film 3D model during steady-state operation under two different operating conditions, as shown in the following formula: ; In the formula This represents the change in liquid film volume per unit power. The height of the liquid film 3D model of heat pipe 310 in steady state before power is applied; The height of the liquid film 3D model of heat pipe 310 in steady state after power is applied; This represents the difference before and after the power change.

[0092] The liquid film phase interface area of ​​the entire evaporation section can be calculated by measuring the liquid film phase interface area of ​​a single hole and the mesh area, combined with the existing data on the length of the evaporation section and the inner diameter of the heat pipe 310. Furthermore, when the liquid film completely wets the wire mesh, the calculation formula is as follows: ; In the formula The phase interface area; The heat pipe has an inner diameter of 310 mm. The height of the liquid film 3D model; The length of the evaporation section is given; all of the above parameters can be obtained experimentally.

[0093] When the liquid film does not completely wet the wire mesh, the calculation formula is as follows: , ; In the formula The phase interface area; The phase interface area of ​​the liquid film within a single pore; This represents the total number of mesh openings in the wire mesh. This refers to the length of the evaporation section; The area of ​​a single mesh opening; The inner diameter of the heat pipe is 310 mm; the above parameters can be obtained experimentally.

[0094] All measurement and calculation data serve the following purpose; Based on the visualized experimental data of alkali metal capillary dynamics characteristics within the main channel core 312, this study analyzes and compares the liquid film evolution characteristics of capillary structures (main channel edge, main channel base layer, and ordinary base layer) at different locations within the main channel core 312. The controlling forces and influence areas of micro-mesoscopic flow within capillary structures at different locations are determined using dimensionless numbers. The mechanical mechanisms underlying the differences in micro-liquid film evolution characteristics between the base layer and main channel capillary units are summarized. Based on these mechanism differences, a microfluidic dynamics model is constructed to describe the evolution of liquid film shape and area within micro-units under capillary structures with different geometric parameters and liquid filling volumes at specific locations. A micro-mesoscopic dynamics mechanism model for capillary flow heat transfer in the main channel core 312 is constructed, closing the resistance source term in the macroscopic momentum equation and the evaporation term in the energy equation of the main channel core 312.

[0095] Furthermore, the step of adjusting the operating conditions according to the preset measurement scheme and repeatedly collecting the image data and operating condition data includes: The working condition adjustment gradient and target steady-state temperature for each working condition are determined according to the experimental objectives, and a unified acquisition standard is set at the same time. Specifically, based on the experimental objective of analyzing the difference in liquid film evolution at various locations of the core under different heat loads, and combined with the phase change characteristics of the alkali metal working medium (sodium) and the safe operating range of the heat pipe, the operating condition adjustment gradient was determined. Since sodium only starts to produce vapor above 450℃ and its evaporation rate is extremely low below 500℃, it cannot effectively transfer heat (at this time, the condensation section is at room temperature, about 25-35℃, and has not entered the working state). Therefore, the initial value of the power of the first heater was set to 1000W, and it was increased in increments of 300W to 2000W. A total of 4 operating conditions were set (1000W, 1300W, 1600W, 2000W) to ensure that sodium can produce sufficient vapor under each operating condition to drive the heat pipe to achieve the "vaporization-liquefaction" cycle.

[0096] The target steady-state temperature was matched synchronously according to the power of each group. The 1000-1300W operating condition corresponds to an evaporation section temperature of 550-650℃ and a condensation section temperature of 450-550℃. At this stage, the sodium vapor content is moderate, and the liquid film has a stable morphology on the capillary surface, allowing for precise observation of its expansion and adhesion characteristics. The 1600-2000W operating condition corresponds to an evaporation section temperature of 680-750℃ and a condensation section temperature of 600-700℃. At this time, the sodium evaporation is sufficient, and the heat transfer efficiency is improved. This allows for the capture of dynamic characteristics such as thickness changes and phase interface fluctuations of the liquid film caused by intensified evaporation under high load. Through a gradient design covering low to high loads, an effective and working fluid-compatible experimental data basis is provided for subsequent comparison of the liquid film evolution differences at various locations of the main core (main core edge, main core base layer, and ordinary base layer).

[0097] The acquisition standard, under the corresponding experimental conditions, is 255 images per model, an acquisition spacing of 6 micrometers, and an acquisition frequency of 10 images per second.

[0098] From the perspective of the number and standards of images in 3D modeling, the standard for 3D depth-of-field modeling is 255 images per model. This clearly states that 255 images must be collected for a single 3D model reconstruction. This is because 3D super-depth-of-field modeling requires the superposition of images at different depths (heights) to achieve full-field clarity. 255 images is the optimal number to cover the height range of the liquid film and the core (e.g., from the bottom of the core to the top of the liquid film, with a height difference of tens of micrometers). Too few images will lead to some areas being out of focus and the model being incomplete, while too many images will result in redundant data and increased processing time. The requirement that the number of images collected for 3D modeling must meet the corresponding experimental conditions emphasizes that the standard of 255 images per model must be matched to different operating conditions. For example, under high-power conditions, the liquid film thickness is thinner and the height range is smaller, but it is still necessary to collect images according to the standard of 255 images to ensure the sampling density in the height direction and ensure that the accuracy of the 3D model is consistent under different operating conditions.

[0099] From the perspective of the physical spacing and frequency of acquisition, the acquisition spacing of 6 micrometers means that the focal planes of two adjacent images differ by 6 micrometers in the height direction. That is, for each image acquired, the lens moves 6 micrometers along the Z-axis before taking the next image. Through this layered acquisition with a fixed physical spacing, the liquid film and the core can be cut into 255 thin slices with a height accuracy of 6 micrometers. In subsequent 3D reconstruction, a continuous spatial shape can be accurately stitched together, avoiding local stretching or compression of the model due to uneven spacing. The acquisition frequency of 10 frames per second is a speed designed to adapt to the 6-micrometer physical spacing. At this frequency, it only takes 25.5 seconds to complete the acquisition of 255 images, which can minimize the acquisition time and reduce the misalignment of layered images caused by slight flow of the liquid film during the acquisition process, ensuring the spatial continuity of the 3D model. At the same time, high-frequency acquisition can also cope with the rapid changes of the liquid film that may occur in the working conditions, avoiding the omission of key morphological information.

[0100] In this embodiment, by setting the acquisition standard, the 3D model can be used to ensure the complete restoration of the liquid film and core space morphology through precise control of the number of images and physical spacing, avoiding model incompleteness due to insufficient data or morphological distortion caused by uneven spacing. At the same time, the efficiency and accuracy of data acquisition can be balanced by using a reasonable acquisition frequency. This reduces the acquisition time to minimize liquid film flow interference while ensuring dynamic response capability to changes in operating conditions. This provides high-quality three-dimensional visualization data support for the subsequent quantitative analysis of the working fluid flow and heat transfer characteristics in high-temperature alkali metal heat pipes.

[0101] Verify and confirm that there are no missing images or data for the current operating condition, and store the files according to the "operating condition number - parameter type" classification, while synchronously recording the steady-state duration and the status of the observation window 315; Specifically, to ensure complete data storage and traceability of the experimental process, a combination of multi-dimensional verification, structured storage, and key information recording will be implemented, as follows: After data acquisition, the system software first initiates a data verification process: For image data, it automatically counts whether the actual number of acquired frames matches the preset number of frames (255 images), and simultaneously checks the image clarity one by one (judged by a grayscale contrast threshold; images below the threshold are marked as blurry and invalid). If there are missing or blurry frames, an alarm is triggered and a prompt is made to reacquire the corresponding time period data. For operating condition data, it verifies whether the number of acquisition groups for temperature (evaporation section / condensation section) and power data is continuous with the time axis (e.g., 510 data groups are required for 8.5 minutes of acquisition), removes abnormal jump values ​​(data exceeding the normal fluctuation range of ±5℃ / ±10W), and completes the data through interpolation of adjacent data to ensure data integrity. After verification, the software automatically generates a structured storage directory according to "Operating Condition Number - Parameter Type". For example, the "Operating Condition 3 - Image Data" directory stores TIFF format liquid film dynamic images, and the "Operating Condition 3 - Operating Condition Data" directory stores temperature and power data in CSV format. Each file name includes a timestamp (such as "Operating Condition 3 - Image - 202405201645.tiff") to avoid file confusion.

[0102] At the same time, key information about the current operating conditions is recorded synchronously in the system log, such as steady-state duration (12 minutes, which must be greater than or equal to the preset 10 minutes) and observation window status (such as "no fogging, clear view" or "slight fogging, which has been restored by the second heater 220"), forming a complete record of the experimental process and providing a basis for subsequent data traceability and operating condition comparison.

[0103] The power of the first heater 210 is gradually adjusted to the next level by the DC power supply 620, and the coolant flow rate of the air gap water cooling jacket 320 is adjusted simultaneously to match the current working power. Specifically, to achieve a smooth transition and precise adaptation to operating conditions, the power gradient switching is accomplished by coordinating the adjustment of DC power output and coolant flow. The specific implementation method is as follows: First, on the DC power supply 620's operating interface, set the target output power according to the preset power gradient (e.g., increasing from 500W to 700W) and select the gradual adjustment mode (adjustment rate set to 50W / minute) to avoid sudden power changes causing drastic fluctuations in heat pipe temperature. After starting the adjustment, monitor the power output power change curve in real time to ensure that the actual power rises steadily to the target value at the set rate. At the same time, use the temperature sensor to synchronously track the temperature of the evaporation section and condensation section (if the temperature fluctuation exceeds ±8℃, pause the adjustment and maintain the current power until the temperature stabilizes before continuing).

[0104] While adjusting the power of the first heater 210, through the flow controller of the air-gap water-cooled jacket 320, according to the "power-flow" adaptation curve (in the preset curve, a power of 700 W corresponds to a coolant flow rate of 2 L / min), the coolant flow rate is gradually adjusted from the current 1.5 L / min to 2 L / min (the adjustment step is set to 0.1 L / min, and each step is separated by 30 seconds); during the adjustment process, the actual flow rate value is continuously fed back through the flow sensor. If the deviation from the target value exceeds ±0.05 L / min, the flow controller automatically corrects the output to ensure that the coolant flow rate precisely matches the current heater power, and timely takes away the increased heat due to the increased power in the condensation section of the heat pipe, laying a temperature foundation for the establishment of the steady state in the next working condition.

[0105] The measuring mechanism 400 is used to continuously monitor the temperature and power in real time for a preset duration to determine whether the heat pipe 310 enters a new steady state; Specifically, to accurately determine whether the heat pipe enters a new steady state, it will rely on the real-time monitoring function of the measuring mechanism and be implemented through the method of "parameter fluctuation monitoring + duration verification"; after the power of the first heater and the coolant flow rate of the air-gap water-cooled jacket are adjusted to the next gradient, the temperature sensor and the power meter in the measuring mechanism 400 are started, and data is collected in real time at a frequency of 1 second / group and uploaded to the host computer; the host computer software automatically generates the real-time change curves of temperature and power, and sets the steady state judgment threshold: if the temperature fluctuation amplitudes of the evaporation section and the condensation section are both ≤ 1 °C / h and the heater power fluctuation ≤ ±10 W / h within 5 consecutive minutes, it is initially determined that the system approaches stability; then continue to monitor and maintain this state until the continuous duration of the fluctuations meeting the above threshold reaches the preset 10 minutes, ensuring that the liquid film morphology and the working fluid phase change are both in a stable state. At the same time, observe the liquid film flow state through the 3D ultra-depth-of-field microscopic system. After both meet the standards, it is determined that the heat pipe 310 officially enters the steady state of the new working condition, and then the subsequent image and working condition data acquisition process can be started.

[0106] Collect image data and working condition data in accordance with the previous working condition standards until all preset working condition data is collected; Specifically, after confirming that the heat pipe enters the steady state of the new working condition, strictly follow the standard of "255 images / modeling, 6-micron acquisition spacing, 10 images / second acquisition frequency" under the matching test working condition to start the data acquisition standard; first, send an instruction from the host computer to the 3D ultra-depth-of-field microscopic system, and the lens moves in layers along the Z axis at a fixed spacing of 6 microns. Each time it moves, 1 liquid film image is collected at a frequency of 10 images / second until 255 images are collected; the single modeling acquisition takes 25.5 seconds, reducing the impact of the dynamic change of the liquid film on the coherence of the 3D modeling; at the same time, the temperature sensor and the power meter collect the working condition data at a frequency of 1 second / group, ensuring that each layer image can match the temperature and power parameters of the corresponding time period, and achieving the precise correspondence of "liquid film 3D morphology - real-time working condition" through data association.

[0107] After data acquisition, the image integrity was first verified to ensure that all 255 layered images were complete and unblurred, and maintained continuity with the operating condition data. Files were then stored according to the classification rule of "Operating Condition Number - 3D Modeling Image / Operating Condition Data," simultaneously recording the steady-state duration and observation window status of the current operating condition. The process of "adjusting heater power to the next gradient → adapting coolant flow rate → confirming the new steady state → acquiring data according to standards" was then repeated until all images and operating condition data for the four preset operating conditions (1000W, 1300W, 1600W, and 2000W) were acquired. This ensured that the data acquisition benchmark for all operating conditions was consistent, providing standardized raw data for subsequent 3D modeling and liquid film evolution analysis.

[0108] Specifically, the core of this invention addresses the technological gap in the study of alkali metal capillary dynamics within the heat pipe core. It constructs a complete experimental system encompassing "operating condition control, data acquisition, model reconstruction, parameter analysis, and mechanism modeling." The aim is to reveal the liquid film evolution patterns at different locations—such as the edge of the heat pipe, the base layer, and the ordinary base layer—under varying heat loads through visualization and quantitative analysis. This system clarifies the differences in the control forces and mechanical mechanisms of micro-mesoscopic flow, ultimately providing experimental support for key terms in the macroscopic momentum and energy equations of the closed heat pipe core. It solves the problems of "invisible liquid film dynamics, difficulty in quantifying parameters, and difficulty in deriving mechanisms" in traditional research, providing theoretical and experimental basis for optimizing the structure and improving the heat transfer performance of the heat pipe core.

[0109] This invention achieves visualization and quantification of the evolution of alkali metal liquid film within the core through standardized operating condition gradient design, synchronized data acquisition, three-dimensional model reconstruction, and systematic parameter analysis. It obtains dynamic change data of key parameters such as liquid film area, height, and contact angle at different structural locations, filling the experimental data gap in the study of microscopic liquid film characteristics.

[0110] Example 6

[0111] Another embodiment of the present invention also provides a method for visually measuring heat pipes, based on the aforementioned system, characterized in that the steps include: S1. Install the heat pipe on the visualization test platform inside the sealed test chamber, so that the heat pipe is in close contact with the first heater, and construct a high-temperature inert safety observation environment through argon protection and water cooling circulation; S2. Start the first heater 210 and the second heater 220 to heat the alkali metal working medium in the heat pipe to make it undergo phase change and cycle, forming a stable and observable liquid film on the surface of the core. S3. Through the composite sapphire vacuum observation window on the heat pipe shell, the measurement mechanism simultaneously collects image data of the dynamic evolution of the liquid film and temperature and power operating condition data. S4. Reconstruct a 3D model of the core and liquid film based on the acquired image data, and perform 2D and 3D data measurements on the 3D model of the liquid film. Extract observation parameters, which include, but are not limited to, 2D parameters such as liquid film area, length, width, and wire diameter, aperture, and area of ​​the mesh; and 3D parameters such as the height of the 3D model, phase interface area, curvature, and contact angle. S5. Based on the observed parameters and corresponding calculation rules, solve for derived parameters such as capillary pressure drop, permeability, gas phase pressure drop, liquid phase pressure drop, and phase interface area; S6. Integrate observation parameters and derived parameters to analyze the flow trajectory and evaporation phase change evolution of the liquid film on the surface of the dry channel-absorbent core composite structure, and establish a quantitative correlation between microscopic behavior and macroscopic heat transfer performance.

[0112] Furthermore, step S3 specifically includes: The working fluid is heated by a first heater and undergoes a phase change to form an observable liquid film until it reaches a stable state; The measuring mechanism is activated to simultaneously acquire image data and operating condition data. Adjust the operating conditions according to the preset measurement plan and repeatedly collect the image data and operating condition data; The image data and operating condition data are verified and categorized for storage.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A heat pipe visualization measurement system, characterized in that, include: A heat pipe includes a casing and a core, and a working fluid disposed within the core; The test chamber, and the visual test platform built inside the test chamber and in a sealed configuration; The test platform is provided with a first receiving slot, a first heater is provided in the first receiving slot, and a second receiving slot is provided on the first heater; The test chamber is also equipped with a measuring mechanism for observing the core of the heat pipe. The measuring mechanism observes the heat pipe through an observation window opened on the pipe shell.

2. The heat pipe visualization measurement system according to claim 1, characterized in that, One end of the heat pipe is fitted with an air gap water cooling jacket, and a chiller and an argon gas tank are connected through the air gap water cooling jacket. The air gap water cooling jacket is provided with a water inlet and a water outlet, as well as an air inlet and an air outlet; The chiller forms a circulating cooling channel through the connection of water pipes to the inlet and outlet; The argon gas cylinder is connected to the inlet and outlet via a gas pipe to form an argon gas protection channel; a liquid controller is installed on the water pipe between the chiller and the water inlet to control the quality and flow rate of the cooling water. An exhaust valve is provided at the end of the air pipe that is connected to the air outlet.

3. The heat pipe visualization measurement system according to claim 2, characterized in that, The heat pipe is filled with an alkali metal working fluid, and the dry channel core is a dry channel wire mesh liquid wick. Furthermore, an observation window is provided at the end of the heat pipe on the side facing the main core. The observation window is formed by laser welding two cap-shaped sapphire crystals, which together form a sealed isolation chamber after installation. The isolation chamber contains a protective medium.

4. The heat pipe visualization measurement system according to claim 3, characterized in that, A second heater is also fitted outside the observation window; The second heater is configured as an MCH alumina ceramic heating tube, and the first heater is configured as a hot runner temperature control copper sleeve; The hot runner temperature control copper sleeve is provided with channels.

5. The heat pipe visualization measurement system according to claim 4, characterized in that, The measuring mechanism is connected to an information acquisition board, which is connected to a host computer to obtain the measurement information of the measuring mechanism.

6. A method for visually measuring heat pipes, implemented based on the system described in claim 5, characterized in that the steps include... include: S1. Install the heat pipe on the visualization test platform inside the sealed test chamber, so that the heat pipe is in close contact with the first heater, and construct a high-temperature inert safety observation environment through argon protection and water cooling circulation; S2. Start the first heater and the second heater to heat the alkali metal working medium in the heat pipe to make it undergo phase change and cycle, forming a stable and observable liquid film on the surface of the core. S3. Through the observation window on the heat pipe shell, use the measuring mechanism to simultaneously collect image data of the dynamic evolution of the liquid film and temperature and power operating condition data; S4. Reconstruct a 3D model of the core and liquid film based on the collected image data, perform 2D and 3D data measurements on the 3D model of the liquid film, and extract the observation parameters; S5. Based on the observed parameters and corresponding calculation rules, solve for the capillary pressure drop, permeability, gas phase pressure drop, liquid phase pressure drop, and phase interface area derived parameters; S6. Integrate observation parameters and derived parameters to analyze the flow trajectory and evaporation phase change evolution of the liquid film on the surface of the dry channel-absorbent core composite structure, and establish a quantitative correlation between microscopic behavior and macroscopic heat transfer performance.

7. The heat pipe visualization measurement method according to claim 6, characterized in that, Step S3 specifically includes: The working fluid is heated by a first heater and undergoes a phase change to form an observable liquid film until it reaches a stable state; The measuring mechanism is activated to simultaneously acquire image data and operating condition data. Adjust the operating conditions according to the preset measurement plan and repeatedly collect the image data and operating condition data; The image data and operating condition data are verified and categorized for storage.

Images