Adjustable high-temperature high-power alkali metal heat pipe experimental system and method

Abstract

The application belongs to the technical field of high-temperature heat pipe experiment, and particularly relates to an adjustable high-temperature high-power alkali metal heat pipe experiment system and method. The experiment system comprises an adjustable high-temperature gravity heat pipe body, a pipeline system, a data acquisition device, a cooling water supply system, a heating system and a control knob type adjusting assembly. The control knob type adjusting assembly is used for adjusting the axial position of the cooling jacket wrapped around the heat pipe. The adjustable high-temperature gravity heat pipe body comprises a heat pipe and a cooling jacket. The heat pipe is divided into a heating section, an adiabatic section and a condensing section. The data acquisition device comprises an axial fixed thermocouple combination, a circumferential fixed thermocouple combination and a top moving thermocouple device. By taking the three-section heat pipe as the experiment body, cooperating with the cooling jacket which can slide along the axis, the thermocouple combination which is fixedly arranged along the outer wall and the moving thermocouple which can extend into the heat pipe, the vapor-liquid temperature distribution at different axial positions can be dynamically obtained in the high-temperature heat pipe close to the actual engineering working condition.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature heat pipe experimental technology, specifically relating to an adjustable high-temperature high-power alkali metal heat pipe experimental system and method. Background Technology

[0002] Heat pipes, as highly efficient passive heat transfer elements, have broad application prospects in fields such as nuclear reactors, aerospace thermal control, and waste heat recovery. High-temperature heat pipes using alkali metal working fluids, in particular, can achieve high-power heat transfer under high-temperature conditions. However, existing research indicates that during the start-up phase or at specific heat flux densities, the boiling state of the working fluid inside alkali metal heat pipes may exhibit unstable and intermittent characteristics, manifested as drastic fluctuations in wall temperature. This intermittent boiling phenomenon not only weakens the stable heat transfer capacity of the heat pipe but can also lead to localized drying and heat pipe burnout in severe cases, posing a potential threat to the safe operation of systems that rely on it for heat transfer, such as heat pipe nuclear reactors.

[0003] To further investigate the occurrence mechanism and evolution of this phenomenon, it is necessary to construct an experimental system capable of realistically simulating the working environment of high-temperature alkali metal heat pipes. For example, the authorized invention patent CN114965564A, "A High-Temperature Pool-Type Alkali Metal Working Fluid Intermittent Boiling Measurement System and Method," provides a static pool-type boiling research scheme. Furthermore, CN1737483A, "Jacketed Axial Heat Pipe," proposes a technical approach of adjusting the heat exchange area of ​​the condensation section through the jacket, while CN121164359A, "Evaporation Section Simulator, Visualized Test Section, and Visualized Test System," focuses on the visual simulation research of the evaporation section. However, the aforementioned existing technologies all have certain limitations: the former is based on a pool-type structure and is not an actual heat pipe body, so it cannot reflect the capillary reflux and axial transport characteristics of the working fluid inside the heat pipe; the latter two cannot flexibly adjust the length of the heating section, nor do they integrate a device that can perform dynamic temperature measurement inside a sealed heat pipe, and they lack a comprehensive experimental research platform that can simultaneously achieve adjustable lengths of the condensing section and the heating section and can perform secondary filling of the working fluid under real high temperature and high linear power radiation heating conditions. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention provides an adjustable high-temperature, high-power alkali metal heat pipe experimental system and method, solving the problem of the lack of an experimental system in the prior art that can simultaneously adjust the lengths of the heating and condensing sections and perform online dynamic measurement of the vapor-liquid temperature distribution inside the pipe, based on a real high-temperature, high-power alkali metal heat pipe.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An adjustable high-temperature high-power alkali metal heat pipe experimental system and method are provided, including an adjustable high-temperature gravity heat pipe body, a piping system, a data acquisition device, a cooling water supply system, a heating system, and a control knob-type adjustment component; The adjustable high-temperature gravity heat pipe body includes a heat pipe and a cooling jacket. The heat pipe is divided into a heating section, an adiabatic section and a condensing section from bottom to top along the axial direction. The cooling jacket is set outside the condensing section of the heat pipe. The control knob type adjustment component is connected to the cooling jacket and is used to drive the cooling jacket to slide along the axial direction of the heat pipe to adjust the axial position of the cooling jacket wrapping the heat pipe. The piping system and cooling water supply system are both connected to the adjustable high-temperature gravity heat pipe body, and the heating system is located outside the heating section of the adjustable high-temperature gravity heat pipe body. The data acquisition device includes an axially fixed thermocouple assembly, a circumferentially fixed thermocouple assembly, and a top movable thermocouple device. The axially fixed thermocouple assemblies are axially spaced along the outer wall of the heat pipe, the circumferentially fixed thermocouple assemblies are circumferentially arranged along the bottom of the heating section of the heat pipe, and the top movable thermocouple device is located at the top of the heat pipe. It includes a movable thermocouple located inside the heat pipe and a drive assembly connected to the movable thermocouple.

[0006] The beneficial effects of adopting the above technical solution are as follows: This adjustable high-temperature, high-power alkali metal heat pipe experimental system uses a heat pipe with a three-section structure (heating section, adiabatic section, and condensation section) as the experimental body. Combined with an axially sliding cooling jacket, a thermocouple assembly fixed along the outer wall, and a movable thermocouple that can extend into the heat pipe, it can dynamically acquire the vapor-liquid temperature distribution at different axial positions inside the high-temperature heat pipe, closely resembling actual engineering conditions. This provides reliable experimental data support for the study of the intermittent boiling mechanism of alkali metal working fluids. Specifically, the heat pipe in the adjustable high-temperature gravity heat pipe body is divided axially from bottom to top into a heating section, an adiabatic section, and a condensation section. This allows the experimental system to accurately reflect the axial partitioning and heat transfer process of an actual gravity heat pipe under operating conditions, avoiding the result deviations caused by using static pool-type or simplified simulation bodies, and ensuring the comparability between intermittent boiling experimental data and engineering reality. A cooling jacket is positioned outside the condensation section of the heat pipe, and a control knob-type adjustment assembly is connected to the cooling jacket to drive it to slide along the heat pipe axis, adjusting the axial position of the cooling jacket surrounding the heat pipe. This allows researchers to flexibly change the effective cooling area of ​​the condensation section on the heat pipe without replacing the adjustable high-temperature gravity heat pipe body, thereby investigating the effects of different cooling positions on the heat transfer characteristics inside the heat pipe and the vapor-liquid interface distribution, expanding the research scope of the experimental system. The piping system is connected to the adjustable high-temperature gravity heat pipe body, enabling vacuuming, protective gas filling, and filling and secondary refilling of the alkali metal working fluid inside the heat pipe, ensuring the sealing and working fluid purity of the experimental system under high-temperature and high-vacuum operating conditions. The cooling water supply system is connected to the adjustable high-temperature gravity heat pipe body, providing circulating cooling water to the cooling jacket, which can promptly remove heat from the condensation section, maintaining stable low-temperature boundary conditions in the condensation section, thus establishing a stable axial temperature gradient inside the heat pipe. The heating system is located outside the heating section of the adjustable high-temperature gravity heat pipe, providing controllable heat power input to the heating section. This provides the necessary heat source for the boiling of the alkali metal working fluid, simulating the working state of a real high-temperature, high-power heat pipe. Together with other structures, it triggers and studies intermittent boiling under high heat flux density conditions. The axially fixed thermocouple assembly in the data acquisition device is spaced axially along the outer wall of the heat pipe, enabling real-time monitoring of the temperature distribution at different axial positions on the outer wall. This provides fundamental data for determining the heat transfer state inside the heat pipe (e.g., single-phase heating, intermittent boiling, or dry-out limit). The circumferentially fixed thermocouple assembly is circumferentially positioned along the bottom of the heating section, capturing circumferential temperature differences at the same height cross-section of the heating section. This is used to verify the uniformity of the heating system and avoid experimental errors caused by localized overheating or uneven heat flow.The top-mounted moving thermocouple device is located at the top of the heat pipe. It includes a moving thermocouple installed inside the heat pipe and a drive assembly connected to the moving thermocouple. The drive assembly moves the moving thermocouple along the axial direction of the heat pipe, enabling online dynamic measurement of the actual temperature of alkali metal liquid and vapor at different heights inside the pipe. When the moving thermocouple enters the gas phase region from the liquid phase region, the height of the vapor-liquid interface can be accurately located based on the temperature jump point, providing a direct measurement method for the evolution law of the vapor-liquid phase transition interface during intermittent boiling.

[0007] Furthermore, both ends of the heat pipe are equipped with wire mesh wicks, which have a multi-layered structure.

[0008] The beneficial effects of adopting the above technical solution are as follows: By setting up multi-layered wire mesh wicks at both ends inside the heat pipe, a stable capillary reflux driving force can be provided for the liquid alkali metal working fluid, so that the liquid in the condensation section can continuously return to the heating section to maintain the working fluid circulation and heat transfer process inside the heat pipe. This truly reflects the working mechanism of the actual high-temperature alkali metal heat pipe, avoids the distortion of working fluid distribution or drying out caused by the lack of wicks, and ensures that the intermittent boiling experiment is carried out under capillary-assisted conditions close to engineering practice, thereby improving the reliability of experimental data.

[0009] Furthermore, the cooling jacket is provided with an embedding groove. The cooling jacket includes a granite jacket and a cooling water jacket arranged sequentially from the inside to the outside. The granite jacket is a heat transfer medium layer with a 4mm gap filled with granite powder with a particle size of 1 to 2mm. The cooling water jacket is provided with a first cooling water inlet and a first cooling water outlet on both sides, and both the first cooling water inlet and the first cooling water outlet are connected to the cooling water supply system. The control knob adjustment assembly includes a slider, which is slidably connected to a slide rail. Both ends of the slide rail are connected to the condensing section of the heat pipe. The bottom of the slider is connected to a cooling jacket, and the top of the slider is provided with a protrusion that is set in an embedded groove for pushing and pulling the cooling jacket so that it slides synchronously along the outer wall of the heat pipe.

[0010] The beneficial effects of adopting the above technical solution are as follows: the granite jacket, as a heat transfer medium, avoids direct rigid contact between the cooling water jacket and the outer wall of the heat pipe, reducing local thermal stress or temperature measurement interference, and provides stable cooling boundary conditions for the condensation section through cooling water circulation. The 4mm gap heat transfer medium layer filled with 1-2mm granite powder provides a uniform heat conduction path while avoiding the generation of local hot spots. The slider connects to the cooling jacket and drives the entire cooling jacket to move axially through the cooperation of the protrusion and the embedded groove, allowing for convenient adjustment of the wrapping position of the condensation section on the heat pipe. This alters the axial distribution of the cooling area on the heat pipe without changing the length of the cooling jacket itself, providing structural support for studying the influence of different cooling positions on the vapor-liquid distribution and intermittent boiling characteristics inside the heat pipe.

[0011] Furthermore, the pipeline system includes a main gas pipeline, a pressure transmitter, a main gas control valve, and a sodium working fluid filling device; the pressure transmitter is installed on the main gas pipeline, one end of the main gas pipeline is connected to the condensing section of the heat pipe through a first pipeline interface, and the other end of the main gas pipeline is connected to the main gas control valve and the sodium working fluid filling device through a three-way pipe respectively; the main gas control valve is connected to the gas device through the first pipeline. The sodium working fluid filling device includes a sodium storage tube with a feeding port at the top. One end of the sodium storage tube is connected to one end of a lower control valve, the other end of which is connected to a main gas pipeline. The other end of the sodium storage tube is connected to one end of an upper control valve, which is connected to a first pipeline via a second pipeline. A heating wire for heating is installed on the outer wall of the sodium storage tube. The gas circuit device includes an argon gas supply device, an argon gas control valve, and a vacuum pump. The output end of the argon gas supply device is connected to the third pipeline, which is equipped with an argon gas control valve. The third pipeline is connected to the fourth and fifth pipelines respectively. The fourth pipeline is connected to the vacuum pump and is equipped with a vacuum pump control valve. The fifth pipeline is connected to the main control valve of the gas circuit through the first pipeline and is equipped with a pressure gauge.

[0012] The beneficial effects of adopting the above technical solution are as follows: the pipeline system integrates functions such as vacuum pumping, argon gas replacement, pressure monitoring, and the feeding, melting, and pressure filling of alkali metal working fluid into the same closed loop. This allows operations such as airtightness testing, heat pipe vacuuming, sodium storage tube heating, and liquid metal injection to be completed sequentially without disassembling the pipeline, effectively preventing the alkali metal working fluid from contacting air. At the same time, the pressure transmitter and pressure gauge can monitor the internal pressure of the heat pipe and the gas path in real time, providing a high-vacuum, high-purity working fluid environment and precise and controllable pressure conditions for intermittent boiling experiments.

[0013] Furthermore, the drive assembly includes a clamping device connected to a movable thermocouple, one end of which is connected to a hand-cranked lead screw slide, the hand-cranked lead screw slide being mounted on a lead screw, and both ends of the lead screw being mounted on a vertical fixed platform. The top-mounted movable thermocouple device also includes a sealing assembly, which is located at the top of the heat pipe. The sealing assembly includes a sealing head, a sealing cap, and a sealing base. The sealing base is connected to the heat dissipation pipe, and the heat dissipation pipe is connected to the top of the heat pipe. A trapezoidal groove is provided between the sealing head and the sealing base, and an O-ring is provided in the trapezoidal groove. The sealing cap and the sealing base are locked together by a threaded connection, which compresses the O-ring to make it fit tightly against the movable thermocouple.

[0014] The beneficial effects of adopting the above technical solution are as follows: the cooperation between the drive component and the sealing component enables the moving thermocouple to move smoothly along the heat pipe axis under the drive of the hand-cranked screw slide, and the linearity and position repeatability of the moving path are ensured by the screw and the vertical fixed platform, thereby obtaining continuous vapor-liquid temperature data at different heights and accurately capturing the temperature jump point at the vapor-liquid interface; at the same time, the sealing component uses the O-ring seal in the trapezoidal groove and the threaded locking between the sealing cap and the sealing base to maintain a dynamic seal with the top of the heat pipe during the lifting and lowering of the moving thermocouple, preventing the leakage of high-temperature alkali metal vapor.

[0015] Furthermore, the cooling water supply system includes a water tank, a water pump, and a flow meter. The water tank is connected to the first cooling water inlet and the first cooling water outlet of the cooling jacket. The water pump is installed on the connecting pipeline between the water tank and the first cooling water inlet, and the flow meter is installed on the connecting pipeline between the water pump and the first cooling water inlet.

[0016] The beneficial effects of adopting the above technical solution are as follows: the cooling water supply system, through the coordinated use of a water tank, a water pump, and a flow meter, can provide a stable and adjustable circulating cooling water source for the cooling jacket, ensuring that the cooling capacity of the condensation section can be quantitatively controlled under different heating powers and cooling positions. Specifically, the water tank is directly connected to the first cooling water inlet and the first cooling water outlet of the cooling jacket, and the water pump is installed on the connecting pipeline between the two, driving the cooling water to flow from the water tank to the cooling jacket, ensuring that the heat of the condensation section is carried away in a timely manner; the flow meter is installed on the connecting pipeline between the water pump and the first cooling water inlet, allowing real-time monitoring of the cooling water flow rate, enabling experimental personnel to adjust the cooling water supply according to the operating conditions, thereby maintaining stable temperature boundary conditions in the condensation section.

[0017] Furthermore, the heating system includes a sleeve, a DC power supply, a controller, an isolation cover, and a nitrogen system. The sleeve is located outside the heating section of the heat pipe, and the controller is electrically connected to the DC power supply and has a full system data acquisition function. An isolation cover is installed outside the adjustable high-temperature gravity heat pipe body. The isolation cover has a second cooling water outlet, a second cooling water inlet, a positive heating power supply interface, a negative heating power supply interface, a second pipeline interface, and a heating system gas pipeline interface on both sides. The isolation cover is connected to the cooling water supply system through the second cooling water outlet and the second cooling water inlet. A DC power supply is connected to terminals through the positive and negative heating power supply interfaces, with the terminals located at the upper and lower ends of the sleeve. The isolation cover is connected to the main gas pipeline of the pipeline system through the second pipeline interface. The isolation cover is also connected to the nitrogen system through the heating system gas pipeline interface. The sleeve has extension sleeves on both sides, and radial through holes are provided on the inner wall of the sleeve. Insertable positioning pins are provided in the radial through holes. Multiple positioning blind holes that cooperate with the positioning pins are provided on the outer wall of the heating section of the heat pipe along the axial direction, which are used to adjust the effective heating length of the heating section.

[0018] The beneficial effects of adopting the above technical solution are as follows: The heating system uses a sleeve to radiate heat to the heating section of the heat pipe, avoiding interference from direct contact between the heating element and the pipe wall. Simultaneously, the isolation cover and nitrogen system create an inert protective atmosphere, preventing high-temperature oxidation and extending the equipment's lifespan. The controller has full-system data acquisition capabilities, enabling synchronous control of heating power and recording experimental data such as temperature and pressure. The extension cylinders on both sides of the sleeve, in conjunction with the pluggable positioning pins and the positioning blind holes on the outer wall of the heat pipe, allow researchers to flexibly adjust the effective heating length of the heating section as needed. This allows for systematic research on the effects of different heating lengths on intermittent boiling triggering conditions and heat transfer characteristics on the same heat pipe without replacing the equipment. The integrated cooling water interface, pipe interface, and power interface on the isolation cover ensure a reliable connection between the external system and the adjustable high-temperature gravity heat pipe body in a sealed state, further improving the overall stability and measurement accuracy of the experimental system.

[0019] Based on the above-mentioned adjustable high-temperature high-power alkali metal heat pipe experimental system, the present invention also provides an adjustable high-temperature high-power alkali metal heat pipe experimental method, comprising the following steps: S1. Preparations before the experiment: The adjustable high-temperature gravity heat pipe body is tested for air tightness and evacuated. Then, alkali metal working fluid is filled into the heat pipe through a sodium working fluid filling device. S2. Conduct intermittent boiling experiment: The heating system is started to heat the heating section. The axial position of the cooling jacket wrapping the heat pipe is adjusted by the control knob adjustment component. The axial temperature of the outer wall of the heat pipe, the circumferential temperature of the bottom of the heating section, and the axial vapor-liquid temperature distribution inside the heat pipe are collected by the data acquisition device. The occurrence of intermittent boiling is determined based on the collected temperature data, and the filling rate of the alkali metal working fluid is adjusted accordingly. S3. Post-experiment work: After the temperature measurement is completed, the heating system is turned off, protective gas is introduced into the experimental system and it is cooled, and then it is cleaned and the working fluid is refilled.

[0020] The beneficial effects of adopting the above technical solution are as follows: This adjustable high-temperature high-power alkali metal heat pipe experimental method, by sequentially performing pre-experiment preparation, intermittent boiling experiment, and post-experiment work, can apply controllable heat to the heating section while ensuring the airtightness and working fluid purity of the adjustable high-temperature gravity heat pipe body, and simultaneously adjust the cooling position of the condensing section. Furthermore, it utilizes a data acquisition device to obtain the axial and circumferential temperature distribution of the outer wall and interior, thereby determining the occurrence of intermittent boiling and adjusting the filling rate. After the experiment, protective gas cooling and cleaning followed by secondary filling create conditions for the next experiment under different operating conditions, enabling continuous research on multiple operating conditions on the same heat pipe body. Specifically, S1 involves airtightness testing and vacuuming of the adjustable high-temperature gravity heat pipe body, followed by filling the heat pipe with alkali metal working fluid through a sodium working fluid filling device. This ensures that the heat pipe is in a high-vacuum, high-purity state before the experiment begins, avoiding the oxidation of the alkali metal working fluid and interference with high-temperature heat transfer characteristics by residual air or moisture. Simultaneously, the controllable working fluid filling lays a reliable initial foundation for subsequent adjustments to the filling rate. S2 heats the heating section by activating the heating system and uses a control knob to adjust the axial position of the cooling jacket surrounding the heat pipe. Simultaneously, it relies on a data acquisition device to acquire the axial temperature of the outer wall of the heat pipe, the circumferential temperature at the bottom of the heating section, and the axial vapor-liquid temperature distribution inside the heat pipe in real time. Based on the temperature data, it can determine the occurrence of intermittent boiling and adjust the filling rate of the alkali metal working fluid accordingly. This achieves active adjustment of the cooling position and filling rate under actual heat pipe working conditions, enabling researchers to systematically study the influence of different cooling zones and different working fluid filling amounts on the intermittent boiling triggering conditions and heat transfer characteristics. The internal axial temperature distribution provided by the top moving thermocouple provides direct evidence for accurately identifying changes in the vapor-liquid interface. After temperature measurement, S3 shuts off the heating system and introduces protective gas into the experimental system for cooling. Simultaneously, it performs cleaning and refilling of the working fluid. The protective gas cooling prevents the alkali metal working fluid from oxidizing upon contact with air at high temperatures, ensuring the safety and service life of the experimental system. The cleaning and refilling operations allow the same heat pipe body to be quickly switched to the next operating condition without disassembling or replacing the heat pipe, thereby significantly improving the efficiency of continuous multi-condition experiments and the comparability of data.

[0021] Furthermore, in S1, the airtightness test includes: filling the heat pipe with argon gas to the test pressure and maintaining the pressure for observation; the vacuuming process includes: continuously evacuating the heat pipe until the vacuum level reaches 10. -3 Pa; The process of filling the working medium with alkali metal includes: putting solid sodium blocks into the sodium storage tube, evacuating the sodium storage tube three times and filling it with argon three times to remove impurity gases, evacuating it three times again after sealing and leak testing, heating it to melt the sodium and keeping the temperature stable, filling it with argon to press the liquid sodium into the heat pipe, and finally weighing it to calculate the mass of the working medium. In S2, before starting the heating system, the air inside the isolation chamber is first extracted using a vacuum pump and then filled with nitrogen to create an inert protective atmosphere. Then, the adjustable high-temperature gravity heat pipe body undergoes three vacuuming and three argon filling operations to achieve a vacuum level of 10 within the adjustable high-temperature gravity heat pipe body. -3 Pa, and then the heating section is heated by radiation heat exchange through the sleeve; the data acquisition system in the controller is run to record the heating start time and heating power; In S2, the temperature data collected includes: when the heat pipe experiences intermittent boiling, a driving component moves a moving thermocouple upwards to measure the vapor-liquid temperature distribution; and a pressure transmitter collects real-time pressure data of the condensation section within the heat pipe, and... The corrected values ​​yield the saturation pressure and saturation temperature inside the heat pipe, where, This is the saturation pressure inside the heat pipe, in Pa. This indicates the pressure in the condenser section of the heat pipe measured by the pressure transmitter, in Pa, which is used as a temperature reference to distinguish different heat transfer states; when the moving thermocouple moves from the liquid phase region to the gas phase region, the actual height of the vapor-liquid interface is determined based on the temperature jump point. In S3, after the temperature measurement is completed, the moving thermocouple is returned to its initial position. After the experiment is completed, the heating system is turned off, and argon gas is introduced into the experimental system to maintain positive pressure and allow it to cool naturally. After the experiment is completed, anhydrous ethanol is injected into the adjustable high-temperature gravity heat pipe body at the sodium storage tube position for cleaning. After the system cools down, the working medium is refilled through the sodium working medium filling device. During the second filling, the storage tank is heated first to liquefy the alkali metal, and then argon gas is used to press the liquid metal into the adjustable high-temperature gravity heat pipe body. Then, the excess argon gas is extracted to the required pressure using a vacuum pump.

[0022] Furthermore, S2 also includes: starting the experiment with a low filling rate according to the experimental design conditions, and increasing the filling rate by injecting liquid sodium through an argon gas supply device in subsequent experiments.

[0023] In summary, the adjustable high-temperature high-power alkali metal heat pipe experimental system and method provided by this invention have the following beneficial effects: (1) The adjustable high-temperature high-power alkali metal heat pipe experimental system uses an adjustable high-temperature gravity heat pipe body that is axially divided into a heating section, an adiabatic section and a condensation section as the experimental body. It is equipped with an axially fixed thermocouple assembly arranged at intervals along the outer wall of the heat pipe, a circumferentially fixed thermocouple assembly arranged circumferentially along the bottom of the heating section, and a top moving thermocouple device set at the top of the heat pipe. The top moving thermocouple device includes a moving thermocouple that extends into the heat pipe and a driving component connected to the moving thermocouple. The driving component drives the moving thermocouple to move axially. The actual height of the vapor-liquid interface is determined according to the temperature jump point when the moving thermocouple enters the gas phase region from the liquid phase region. This realizes multi-dimensional synchronous measurement of the axial temperature of the outer wall of the heat pipe, the circumferential temperature at the bottom of the heating section and the axial vapor-liquid temperature distribution inside the heat pipe. It provides direct experimental data support for studying the intermittent boiling evolution law of high-temperature alkali metal working fluid in a closed heat pipe.

[0024] (2) The adjustable high-temperature high-power alkali metal heat pipe experimental system controls the cooling jacket to slide along the heat pipe axis by cooperating with the embedded groove and slider protrusion on the cooling jacket through the control knob adjustment component. This changes the axial length of the cooling jacket covering the heat pipe, thereby flexibly adjusting the effective cooling area of ​​the condensation section. At the same time, the heating system is equipped with a sleeve, an extension sleeve, radial through holes and pluggable positioning pins on the inner wall of the sleeve, and multiple positioning blind holes machined along the axial direction on the outer wall of the heating section of the heat pipe, so as to realize the on-demand adjustment of the effective heating length of the heating section. Furthermore, the sleeve and the heating section of the heat pipe adopt a non-contact radiation heating method. With the sealed isolation cover and the inert gas protection provided by the nitrogen system connected to the isolation cover, the interference of the heating element on the wall temperature measurement is avoided, and the same adjustable high-temperature gravity heat pipe body can adapt to the multi-condition experimental requirements of different cooling positions, different heating lengths and different heat flux densities.

[0025] (3) The adjustable high-temperature high-power alkali metal heat pipe experimental system integrates a sodium working fluid filling device, including a sodium storage tube, a control valve at the lower end of the sodium storage tube, a control valve at the upper end of the sodium storage tube, and a feeding port, into the pipeline system. It works in conjunction with a gas circuit device, including a vacuum pump, an argon supply device, an argon control valve, and a vacuum pump control valve. This enables solid alkali metal to be melted and pressurized under vacuum and argon protection conditions and injected into the adjustable high-temperature gravity heat pipe body. After the experiment, the system can be cooled down and the working fluid can be refilled through the sodium working fluid filling device. In the process of refilling, the storage tank is heated first to liquefy the alkali metal, and then argon is used to pressurize the liquid alkali metal into the adjustable high-temperature gravity heat pipe body. Finally, the excess argon is extracted to the required pressure by the vacuum pump, thereby avoiding direct contact between the alkali metal working fluid and the air, and effectively supporting continuous repeated experiments with different filling rates and multiple working conditions.

[0026] (4) The adjustable high-temperature high-power alkali metal heat pipe experimental system is provided with a granite jacket and a cooling water jacket arranged sequentially from the inside to the outside in the cooling jacket. The granite jacket is a heat transfer medium layer filled with granite powder with a particle size of 1-2 mm. This avoids the local thermal stress and temperature measurement interference caused by the direct rigid contact between the cooling water jacket and the outer wall of the heat pipe. It also provides stable cooling boundary conditions for the condensation section through cooling water circulation. At the same time, the heating system uses a stainless steel sleeve to wrap the heating section of the heat pipe and realizes heat transfer by radiation heat exchange. With the help of DC power supply and controller, it can achieve a maximum line power heating of 20 kW / m and a maximum operating temperature of 1200℃ for the adjustable high-temperature gravity heat pipe body. The isolation cover is made of 310s stainless steel and can withstand a high temperature of 1500℃. A sealed isolation cover is set outside the adjustable high-temperature gravity heat pipe body and connected to the nitrogen system to form an inert gas protective atmosphere. This ensures that the heating element does not interfere with the wall temperature measurement while triggering intermittent boiling under real high heat flux density conditions.

[0027] (5) The adjustable high-temperature high-power alkali metal heat pipe experimental system is equipped with a sealing assembly consisting of a sealing head, a sealing cap, and a sealing base in the top moving thermocouple device. A trapezoidal groove is opened between the sealing head and the sealing base, and an O-ring is installed in the trapezoidal groove. The sealing cap and the sealing base are locked by threaded engagement, thereby squeezing the O-ring so that it fits tightly with the moving thermocouple. Even if the moving thermocouple moves up and down frequently along the heat pipe axis under the drive of the hand-cranked screw slide, it can still ensure reliable dynamic sealing inside the adjustable high-temperature gravity heat pipe body under high temperature and high vacuum conditions, effectively preventing alkali metal vapor leakage and external air ingress. Furthermore, the hand-cranked screw slide and the screw on the vertical fixed platform cooperate to ensure the linear motion accuracy and repeatability of the moving thermocouple, realizing continuous online measurement of vapor-liquid temperature distribution at different axial positions inside the pipe during heat pipe operation. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall structure of the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention. Figure 2 This is a schematic diagram of the adjustable high-temperature gravity heat pipe body in the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention. Figure 3 This is a schematic diagram of the cooling jacket structure in the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention. Figure 4 This is a schematic diagram of the control knob adjustment component in the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention. Figure 5 This is a schematic diagram of the piping system in the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention; Figure 6 This is a schematic diagram of the gas path device in the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention. Figure 7 This is a schematic diagram of the sodium working fluid filling device in the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention. Figure 8 This is a schematic diagram of the sealing component in the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention. Figure 9 This is a schematic diagram of the data acquisition device in the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention. Figure 10 This is a schematic diagram of the cooling water supply system in the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention. Figure 11 This is a schematic diagram of the overall structure of the heating system in the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention. Figure 12 This is a schematic diagram of the structure of the isolation cover in the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention; Figure 13 This is a schematic diagram of the extension tube in the adjustable high-temperature high-power alkali metal heat pipe experimental system of the present invention. The components include: 1. Adjustable high-temperature gravity heat pipe body; 101. Heat pipe; 102. Cooling jacket; 103. First cooling water inlet; 104. Cooling water jacket; 105. Granite jacket; 106. First cooling water outlet; 107. Wire mesh liquid suction core; 108. Embedded groove; 2. Piping system; 201. Gas circuit device; 202. Argon gas supply device; 203. Vacuum pump; 204. Argon gas control valve; 205. Vacuum pump control valve; 206. Pressure gauge. 207. Sodium working fluid filling device; 208. Lower control valve of sodium storage tube; 209. Sodium storage tube; 210. Upper control valve of sodium storage tube; 211. Main control valve of gas circuit; 212. Pressure transmitter; 213. Main gas pipeline; 214. First pipeline interface; 215. First pipeline; 216. Second pipeline; 217. Third pipeline; 218. Fourth pipeline; 219. Fifth pipeline; 3. Data acquisition device; 301. Top movable thermocouple device; 302. 303. Hand-cranked screw slide; 304. Clamping device; 305. Moving thermocouple; 306. Sealing head; 307. Sealing cap; 308. Sealing base; 309. O-ring; 310. Heat dissipation pipe; 311. Axially fixed thermocouple assembly; 312. Circumferentially fixed thermocouple assembly; 313. Screw; 314. Vertical fixed platform; 4. Cooling water supply system; 401. Water pump; 402. Flow meter; 403. Water tank; 5. Heating system; 501. 502. Sleeve; 503. DC power supply; 504. Controller; 505. Isolation cover; 506. Terminal block; 507. Extension tube; 508. Heating power supply positive interface; 509. Heating power supply negative interface; 510. Nitrogen system; 511. Heating system gas pipeline interface; 512. Second pipeline interface; 513. Second cooling water outlet; 514. Second cooling water inlet; 6. Control knob type adjustment component; 61. Slider; 62. Protrusion; 63. Slide rail. Detailed Implementation

[0029] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0030] Example 1 like Figures 1-13As shown, the adjustable high-temperature high-power alkali metal heat pipe experimental system provided by the present invention includes an adjustable high-temperature gravity heat pipe body 1, a piping system 2, a data acquisition device 3, a cooling water supply system 4, a heating system 5, and a control knob-type adjustment component 6. The entire system is vertically fixed on a steel frame platform to ensure that the adjustable high-temperature gravity heat pipe body 1 is in a vertical state, and the entire system can achieve a maximum line power heating of 20kW / m, and the maximum operating temperature of the heat pipe 101 can reach 1200℃.

[0031] like Figure 2 As shown, the adjustable high-temperature gravity heat pipe body 1 includes a heat pipe 101 and a cooling jacket 102. The heat pipe 101 is a 316 stainless steel round tube with a length of 600 mm, an inner diameter of 16 mm, an outer diameter of 22 mm, and a wall thickness of 3 mm. The heat pipe 101 is divided into a heating section, an insulation section, and a condensation section axially from bottom to top. Both ends of the heat pipe 101 are equipped with wire mesh wicks 107, which have a multi-layer structure of 4 layers of 200 mesh and 4 layers of 400 mesh, and are firmly welded to the inner wall of the heat pipe 101 by end spot welding. By dividing the heat pipe 101 into heating, insulation, and condensation sections axially from bottom to top, the geometric dimensions, material properties, and axial partitioning structural characteristics of the actual high-temperature alkali metal heat pipe 101 are reflected. Both ends of the heat pipe 101 are equipped with multi-layer wire mesh wicks 107, which are firmly welded to the inner wall of the heat pipe 101 by end spot welding. This provides a stable capillary reflux driving force for the liquid alkali metal working fluid, allowing the liquid in the condensation section to continuously return to the heating section, maintaining the working fluid circulation and heat transfer inside the heat pipe 101. This avoids drying out or heat transfer deterioration due to the lack of wicks, ensuring that the intermittent boiling experiment is carried out under capillary-assisted conditions close to actual engineering conditions, and improving the reliability of the experimental results.

[0032] like Figure 3As shown, the cooling jacket 102 is disposed outside the condensation section of the heat pipe 101. The cooling jacket 102 is a cylindrical structure with an inner diameter of 30 mm and an outer diameter of 45 mm, including a granite jacket 105 and a cooling water jacket 104 arranged sequentially from the inside to the outside. Specifically, the granite jacket 105 is a heat transfer medium layer with a 4 mm gap filled with granite powder with a particle size of 1-2 mm, located between the cooling water jacket 104 and the outer wall of the heat pipe 101. A first cooling water inlet 103 and a first cooling water outlet 106 are respectively provided on both sides of the cooling water jacket 104, both of which are connected to the cooling water supply system 4. The cooling jacket 102 is also provided with an embedded groove 108, and a control knob-type adjustment component 6 is disposed in the embedded groove 108. The granite jacket 105 avoids direct rigid contact between the cooling water jacket 104 and the outer wall of the heat pipe 101, reducing local thermal stress and interference with wall temperature measurement. It also utilizes the thermal conductivity of granite powder to uniformly transfer heat from the condensation section to the cooling water jacket 104. The first cooling water inlet 103 and the first cooling water outlet 106 on both sides of the cooling water jacket 104 are connected to the cooling water supply system 4, forming a stable circulating cooling loop that promptly removes heat and provides reliable low-temperature boundary conditions for the condensation section. The embedded groove 108 on the cooling jacket 102 is used to embed the control knob-type adjustment component 6, allowing the cooling jacket 102 to slide and adjust its position axially along the heat pipe 101. This alters the distribution of the cooling area on the heat pipe 101 without changing the length of the cooling jacket 102 itself, providing a structural basis for studying the influence of different cooling positions on the vapor-liquid distribution and intermittent boiling characteristics inside the heat pipe 101.

[0033] like Figure 3 and Figure 4 As shown, the control knob-type adjustment assembly 6 includes a slider 61, which is slidably connected to a slide rail 63. Both ends of the slide rail 63 are connected to the condensing section of the heat pipe 101. The bottom of the slider 61 is connected to a cooling jacket 102, and a protrusion 62 is provided on the top of the slider 61. The protrusion 62 is located within an embedding groove 108 and is used to push and pull the cooling jacket 102 to slide synchronously along the outer wall of the heat pipe 101. When the experimenter presses the slider 61, the slider 61 moves axially along the slide rail 63. Through the cooperation of the protrusion 62 and the embedding groove 108, the cooling jacket 102 is pushed and pulled, causing it to slide synchronously up and down along the outer wall of the heat pipe 101. This changes the axial length of the cooling jacket 102 surrounding the heat pipe 101, thus achieving on-demand adjustment of the condensing section length.

[0034] like Figure 5As shown, the piping system 2 includes a main gas pipeline 213, a pressure transmitter 212, a main gas control valve 211, and a sodium working fluid filling device 207. One end of the main gas pipeline 213 is connected to the condenser section of the heat pipe 101 via a first pipeline interface 214, and the other end is connected to the main gas control valve 211 and the sodium working fluid filling device 207 via a tee pipe. The main gas control valve 211 is connected to the gas device 201 via a first pipeline 215. Figure 5 and Figure 7 As shown, the sodium working fluid filling device 207 includes a sodium storage tube 209. A feeding port is located at the top of the sodium storage tube 209, and the feeding port has a threaded sealing cap structure. One end of the sodium storage tube 209 is connected to one end of a lower control valve 208, and the other end of the lower control valve 208 is connected to a main gas pipeline 213. The other end of the sodium storage tube 209 is connected to one end of an upper control valve 210, and the other end of the upper control valve 210 is connected to a first pipeline 215 via a second pipeline 216. A heating wire is uniformly wound around the outer wall of the sodium storage tube 209. The heating wire is a nickel-chromium alloy resistance wire with an insulating outer sheath, and this heating wire is connected to a DC power supply 502 for heating. The piping system 2 allows for the sequential completion of operations such as vacuum pump 203 evacuation, argon purging, real-time monitoring of internal pressure in heat pipe 101, and the feeding, heating, melting, and injection of liquid sodium into heat pipe 101 within the same closed system, avoiding the risk of leakage caused by repeated disassembly and assembly. The independently installed heating wire on the outer wall of the sodium storage tube 209 enables in-situ heating and melting of solid sodium. Combined with the time-sharing control of the upper control valve 210 and the lower control valve 208 of the sodium storage tube, and the argon pressure drive, it achieves directional flow and precise filling of molten sodium under closed conditions. This ensures that the alkali metal working medium does not come into contact with air during the entire filling process and provides a repeatable operating path for subsequent secondary fillings, thus providing a high-vacuum, high-purity working medium environment and reliable pressure data for intermittent boiling experiments.

[0035] like Figure 5 and Figure 6As shown, the gas path device 201 includes an argon gas supply device 202, an argon gas control valve 204, and a vacuum pump 203. The output end of the argon gas supply device 202 is connected to a third pipeline 217, on which the argon gas control valve 204 is installed. The third pipeline 217 is connected to a fourth pipeline 218 and a fifth pipeline 219. The fourth pipeline 218 is connected to the vacuum pump 203, on which a vacuum pump 203 control valve is installed. The fifth pipeline 219 is connected to the main gas path control valve 211 via a first pipeline 215, and a pressure gauge 206 is installed on the fifth pipeline 219. All the above pipelines are made of 304 stainless steel with a bore diameter of 7mm. Through the arrangement of the argon gas supply device 202, the argon gas control valve 204, the vacuum pump 203, and the related pipelines, the gas path device 201 provides the adjustable high-temperature gravity heat pipe body 1 with the dual functions of vacuuming and filling with protective gas. The output end of the argon supply device 202 is connected to the third pipeline 217, which is equipped with an argon control valve 204 to independently control the flow of argon. The third pipeline 217 is connected to the fourth pipeline 218 and the fifth pipeline 219 via a three-way pipe. The fourth pipeline 218 is connected to the vacuum pump 203 and is equipped with a vacuum pump 203 control valve. The fifth pipeline 219 is connected to the main gas control valve 211 and is equipped with a pressure gauge 206. This allows the experimenter to selectively start the vacuum pump 203 to evacuate the heat pipe 101 or turn on the argon supply device 202 to fill the system with argon as needed. At the same time, the pressure gauge 206 monitors the gas pressure in real time, realizing integrated control of vacuuming, gas replacement and pressure monitoring. This ensures that the heat pipe 101 can reach the required high vacuum and maintain an inert atmosphere, creating a reliable gas environment for the stable operation of high-temperature alkali metal working fluid and intermittent boiling experiments.

[0036] like Figure 1 , Figure 2 and Figure 10As shown, the cooling water supply system 4 includes a water tank 403, a water pump 401, and a flow meter 402. The water tank 403 is connected to the first cooling water inlet 103 and the first cooling water outlet 106 of the cooling jacket 102. The water pump 401 is installed on the connecting pipe between the water tank 403 and the first cooling water inlet 103, and the flow meter 402 is installed on the connecting pipe between the water pump 401 and the first cooling water inlet 103. Through the coordinated use of the water tank 403, the water pump 401, and the flow meter 402, the cooling water supply system 4 can provide a stable and adjustable circulating cooling water source for the cooling jacket 102, ensuring that the cooling capacity of the condensing section can be quantitatively controlled under different heating powers and cooling positions. The water tank 403 is directly connected to the first cooling water inlet 103 and the first cooling water outlet 106 of the cooling jacket 102. The water pump 401 is installed on the connecting pipe between the two, which can drive the cooling water from the water tank 403 to the cooling jacket 102 to ensure that the heat of the condensation section is carried away in time. The flow meter 402 is installed on the connecting pipe between the water pump 401 and the first cooling water inlet 103, which can monitor the flow rate of the cooling water in real time, so that the experimenters can adjust the supply of cooling water according to the working conditions, thereby maintaining a stable temperature boundary condition in the condensation section.

[0037] like Figure 1 , Figure 8 and Figure 9 As shown, the data acquisition device 3 includes an axially fixed thermocouple assembly 310, a circumferentially fixed thermocouple assembly 311, and a top-moving thermocouple device 301. Both the axially fixed thermocouple assembly 310 and the circumferentially fixed thermocouple assembly 311 use N-type armored thermocouples with a diameter of 1 mm. The axially fixed thermocouple assembly 310 is evenly arranged every 40 mm along the outer wall of the heat pipe 101 to measure the axial temperature distribution on the outer wall of the heat pipe 101. The circumferentially fixed thermocouple assembly 311 has four thermocouples arranged circumferentially at a distance of 20 mm from the bottom of the heating section to measure the circumferential temperature distribution at the bottom of the heating section, thereby determining whether the heating is uniform. In addition, the installation method of the axial fixed thermocouple assembly 310 and the circumferential fixed thermocouple assembly 311 is as follows: a groove with a depth of 1mm is opened on the outer wall surface of the heat pipe 101, the thermocouple is embedded in the groove, the outer layer is covered with stainless steel sheet, and the stainless steel sheet is fixed to the adjustable high temperature gravity heat pipe body 1 by spot welding with a spot welding machine to achieve fixation.

[0038] like Figure 8 and Figure 9As shown, a top-mounted movable thermocouple device 301 is disposed at the top of the heat pipe 101, including a movable thermocouple 304 and a drive assembly. The movable thermocouple 304 is 800 mm long and is inserted into the heat pipe 101. The drive assembly includes a clamping device 303 and a hand-cranked screw slide 302. The movable thermocouple 304 is fixed by the clamping device 303, which is connected to the hand-cranked screw slide 302. The hand-cranked screw slide 302 is mounted on a screw 312, with both ends of the screw 312 mounted on a vertical fixed platform 313. By manually driving the screw slide 302, the movable thermocouple 304 can be moved up and down along the axial direction of the heat pipe 101, thereby measuring the internal vapor-liquid temperature at different heights. When the movable thermocouple 304 enters the vapor phase region from the liquid phase region, the temperature will change significantly, which can be used to determine the actual height of the vapor-liquid interface.

[0039] like Figure 8 As shown, the top movable thermocouple device 301 also includes a sealing assembly, which is disposed on the top of the heat pipe 101. The sealing assembly includes a sealing head 305, a sealing cap 306, and a sealing base 307. The sealing base 307 is connected to the heat dissipation pipe 309, and the heat dissipation pipe 309 is connected to the top end of the heat pipe 101. A trapezoidal groove is provided between the sealing head 305 and the sealing base 307, and an O-ring seal 308 is provided in the trapezoidal groove. The sealing cap 306 and the sealing base 307 are locked together by a threaded engagement, and the O-ring seal 308 is squeezed to make it fit tightly against the movable thermocouple 304. The sealing assembly can maintain a reliable dynamic seal during the axial movement of the moving thermocouple 304 along the heat pipe 101, effectively preventing the leakage of high-temperature alkali metal vapor or protective gas inside the heat pipe 101 to the outside, while preventing external air from entering the heat pipe 101, thus ensuring the sealing integrity of the heat pipe 101 under high temperature and high vacuum working conditions; the trapezoidal groove allows the O-ring 308 to be uniformly compressed when the thread is tightened, resulting in a tighter fit, and even if the moving thermocouple 304 is frequently raised and lowered, it is not easy for the seal to fail.

[0040] like Figure 11 , Figure 12 and Figure 13As shown, the heating system 5 includes a sleeve 501, a DC power supply 502, a controller 503, an isolation cover 504, and a nitrogen system 509. The sleeve 501 is located outside the heating section of the heat pipe 101. Terminals 505 are welded to the upper and lower ends of the sleeve 501, and extension sleeves 506 are threaded to both sides of the sleeve 501. A radial through-hole (not shown) is provided on the inner wall of the sleeve 501, and a pluggable positioning pin (not shown) is provided within the radial through-hole. Multiple blind positioning holes (not shown) that mate with the positioning pin are machined axially on the outer wall of the heating section of the heat pipe 101. The effective heating length of the heating section can be changed by inserting and removing the positioning pin and adjusting the relative positions of the heat pipe 101, sleeve 501, and extension sleeve 506. The controller 503 is electrically connected to the DC power supply 502, and the controller 503 also performs power control of the DC power supply 502 and data acquisition for the entire system. Meanwhile, the isolation cover 504 is made of 310s stainless steel and can withstand a high temperature of 1500℃, sealingly enclosing the entire adjustable high-temperature gravity heat pipe body 1. The isolation cover 504 has a second cooling water outlet 512, a second cooling water inlet 513, a heating power supply positive terminal interface 507, a heating power supply negative terminal interface 508, a second pipeline interface 511, and a heating system gas pipeline interface 5 on both sides. The isolation cover 504 is connected to the cooling water supply system 4 through the second cooling water outlet 512 and the second cooling water inlet 513. The isolation cover 504 has a second pipeline interface 511 through which the main gas pipeline 213 passes, and it is connected to the nitrogen system 509 through the heating system gas pipeline interface 510. All connections between the isolation cover 504 and each interface are sealed with polytetrafluoroethylene (PTFE). A DC power supply 502 is electrically connected to the terminals 505 at the upper and lower ends of the sleeve 501 via the positive and negative terminals 507 and 508, respectively, to power and heat the sleeve 501. There is no direct contact between the sleeve 501 and the heating section of the heat pipe 101; heat is transferred via radiation. Both the heating and insulation sections are covered with insulating cotton. A nitrogen system 509 fills the isolation cover 504 with nitrogen to create an inert protective atmosphere, preventing oxidation of the sleeve 501 and the heat pipe 101 at high temperatures.

[0041] Example 2 Based on the above-described adjustable high-temperature, high-power alkali metal heat pipe experimental system, this embodiment provides an adjustable high-temperature, high-power alkali metal heat pipe experimental method, specifically including the following steps: S1. Preparations before the experiment: First, perform the airtightness detection: Completely remove the air inside the system by adopting the method of three-time vacuum pumping and three-time argon filling. The specific operation is as follows: Open the argon control valve 204, slowly fill argon into the heat pipe 101 until the pressure reaches the preset detection pressure. After closing the argon control valve 204, apply the leak detection liquid to all welds, joints, and valve seals, and observe whether there are continuous bubbles generated. If there are no bubbles, stop filling, close the argon control valve 204, only keep the pressure transmitter 212 connected to the heat pipe 101, record the pressure value and ambient temperature at this time, and keep the pressure for 24 hours to observe whether the pressure drops. If the pressure does not drop significantly, the airtightness is qualified.

[0042] Then, perform vacuum pumping: Open the vacuum pump control valve 205, start the vacuum pump 203 to continuously pump air from the heat pipe 101 until the vacuum degree shown by the pressure transmitter 212 reaches 10 -3 Pa and is stable. Close the main air path control valve 211, the lower control valve 208 of the sodium storage pipe, the upper control valve 210 of the sodium storage pipe, the vacuum pump control valve 205, and the argon control valve 204. Observe the change of pressure with time through the pressure transmitter 212. If the pressure rises very slowly, it indicates good airtightness.

[0043] Next, perform sodium working medium filling: Open the main air path control valve 211, the lower control valve 208 of the sodium storage pipe, the upper control valve 210 of the sodium storage pipe, and the vacuum pump control valve 205, close the argon control valve 204, start the vacuum pump 203 to pump vacuum. When the vacuum degree in the whole system reaches 10 -3 Pa, close the lower control valve 208 of the sodium storage pipe and the vacuum pump control valve 205, and stop pumping air.

[0044] Perform continuous three-time vacuum pumping and argon filling operations on the sodium storage pipe 209 to remove the impurity gases inside the sodium storage pipe 209: For the first time, open the vacuum pump control valve 205 and the upper control valve 210 of the sodium storage pipe, start the vacuum pump 203 to pump vacuum to 10 -3 Pa, then close the vacuum pump control valve 205 and the upper control valve 210 of the sodium storage pipe; then open the argon control valve 204 and the upper control valve 210 of the sodium storage pipe, and fill argon to normal pressure, then close the argon control valve 204 and the upper control valve 210 of the sodium storage pipe. Repeat the above operation twice. After the three operations are completed, close the main air path control valve 2i1, the lower control valve 208 of the sodium storage pipe, the upper control valve 210 of the sodium storage pipe, the vacuum pump control valve 20i5, and the argon control valve 204.

[0045] Remove the solid sodium block from the sealed container and place it into the argon-filled sodium storage tube 209. Seal and tighten the threaded sealing cap at the upper feed port of the sodium storage tube 209. Open the argon control valve 204 and the upper control valve 210 of the sodium storage tube, and introduce a small amount of argon to create positive pressure inside the sodium storage tube 209. Close the argon control valve 204 and the upper control valve 210 of the sodium storage tube, and perform a leak check using leak detection fluid. After confirming there is no leak, open the vacuum pump control valve 205, the upper control valve 210 of the sodium storage tube, and the main gas control valve 211. Close the argon control valve 204 and the lower control valve 208 of the sodium storage tube. Start the vacuum pump 203 to perform three vacuuming operations on the sodium storage tube 209 (each time evacuating to 10). -3 After vacuuming for three cycles, close vacuum pump control valve 205, open argon control valve 204 to purge argon to atmospheric pressure, and then close argon control valve 204 again. After three evacuations, close vacuum pump control valve 205, sodium storage tube upper control valve 210, and gas path main control valve 211. Start DC power supply 502 to heat sodium storage tube 209 and connecting pipes. Run NI data acquisition system in controller 503 to monitor pipe temperature, maintaining the temperature of part of sodium storage tube 209 at around 200℃ for at least 30 minutes, and record the heating start time and temperature at key locations. At this time, move thermocouple 304 to the bottom position.

[0046] After all the sodium in the sodium storage tube 209 has melted, open the upper control valve 210 and the lower control valve 208 of the sodium storage tube, and open the argon control valve 204 to slowly fill with argon gas. Use the argon gas pressure to force the liquid sodium in the sodium storage tube 209 into the heat pipe 101. Observe the pressure transmitter 212. When the pressure reaches the predetermined value, close the lower control valve 208, the upper control valve 210, and the argon control valve 204. Finally, close all the opened valves. After the sodium storage tube 209 cools to room temperature, remove the sodium storage tube 209 and weigh it again to calculate the mass of the working fluid entering the adjustable high-temperature gravity heat pipe body 1.

[0047] S2. Conduct intermittent boiling experiment: First, use vacuum pump 203 to evacuate the existing air from the isolation chamber 504, then fill it with nitrogen to create an inert protective atmosphere. Repeat the evacuation and nitrogen filling process three times to ensure that the isolation chamber 504 is filled with a nitrogen atmosphere.

[0048] Then, a three-stage evacuation and three-stage filling operation is performed on the adjustable high-temperature gravity heat pipe body 1: the main gas control valve 211, the lower sodium storage tube control valve 208, and the upper sodium storage tube control valve 210 are closed; the vacuum pump control valve 205 and the argon control valve 204 are opened; the vacuum pump 203 is started; and the heat pipe 101 is evacuated through the fourth pipe 218, the fifth pipe 219, and the first pipe 215 until the pressure transmitter 212 shows a vacuum level of 10. -3Pa, close vacuum pump control valve 205. Open argon control valve 204 to fill heat pipe 101 with argon gas until atmospheric pressure, then close it. Repeat the above vacuuming and argon filling operation three times, finally maintaining a high vacuum state inside heat pipe 101.

[0049] Turn on the DC power supply 502 and connect the sleeve 501 for heating. Run the NI data acquisition system to record the heating start time, heating power, and the position of the moving thermocouple 304. When the temperature reaches the predetermined operating condition and intermittent boiling occurs, use the hand-cranked screw slide 302 to drive the moving thermocouple 304 to move upwards step by step, measuring the vapor-liquid temperature distribution. When the moving thermocouple 304 enters the vapor phase from the liquid phase region, the temperature will jump significantly, thereby determining the actual height of the vapor-liquid interface.

[0050] During the experiment, pressure transmitter 212 collected real-time pressure data of the condensation section inside heat pipe 101. Since there was a deviation between the measured pressure and the actual saturation pressure inside heat pipe 101, it was corrected using a formula. In the formula, This is the saturation pressure inside heat pipe 101, in Pa. This represents the pressure in the condensation section of heat pipe 101 measured by the pressure transmitter, in Pa, and the corresponding saturation temperature is calculated. This saturation temperature is selected as a reference. When heat pipe 101 reaches this saturation temperature reference at a certain moment, the wall temperature at each measuring point at that moment is extracted. By comparing the temperature differences of the four thermocouples arranged circumferentially at the bottom of the heating section, it is determined whether the heating system 5 heats uniformly, avoiding local overheating or drying. Based on the temperature distribution pattern of each measuring point along the axial direction, different heat transfer states such as single-phase heating, intermittent boiling, and drying limit are distinguished.

[0051] Based on the experimental design conditions, the experiment started with a low filling rate. In subsequent experiments, liquid sodium was continuously injected through the argon gas supply device 202 to increase the filling rate, and the experiment continued with a high filling rate. If it is necessary to clean the adjustable high-temperature gravity heat pipe body 1 during the experiment, anhydrous ethanol can be replaced at the sodium storage tube 209 and injected into the adjustable high-temperature gravity heat pipe body 1 to fully dissolve the residual sodium for the next experiment.

[0052] S3. Post-experiment work: After the measurement is completed at the specified operating temperature, the movable thermocouple 304 is returned to its initial position. After the system cools down, the alkali metal working fluid filling system is reinstalled, and the above steps are repeated for a second filling of the working fluid to prepare for the next experiment. During the second filling, the storage tank is first heated to liquefy the alkali metal. Then, the argon supply device 202 is used to pressurize the liquid alkali metal from the storage tank into the adjustable high-temperature gravity heat pipe body 1. Next, the vacuum pump 203 is used to extract excess argon gas from the adjustable high-temperature gravity heat pipe body 1 to the required pressure, thus avoiding direct contact between the alkali metal working fluid and air. If any abnormality is found during the above steps, the experiment under that condition should be stopped and restarted after the abnormality is eliminated. After the experiment is completed, the relevant measuring instruments and sensors are turned off, the heating system 5 is shut off, and argon gas is introduced into the experimental section to maintain positive pressure and prevent the liquid sodium from oxidizing. The section is then allowed to cool naturally.

[0053] In summary, the adjustable high-temperature high-power alkali metal heat pipe experimental system and method provided by this invention uses a three-section adjustable high-temperature gravity heat pipe body 1 as the experimental body. The lengths of the condensation section and the heating section are flexibly adjusted by the axially sliding cooling jacket 102 and the sleeve 501 with positioning pins, respectively. The temperature distribution of vapor and liquid inside the pipe is measured online by the movable thermocouple 304 and the vapor-liquid interface is accurately located. At the same time, the sodium working fluid filling device 207 and the gas path system are integrated to realize the closed filling and secondary injection of alkali metal. With the granite jacket 105, non-contact radiant heating and nitrogen protective atmosphere, the intermittent boiling phenomenon can be truly triggered under the conditions of 20kW / m line power and 1200℃ high temperature. It provides a reliable multi-dimensional temperature data and an experimental platform with adjustable operating conditions for studying the intermittent boiling evolution law of alkali metal heat pipe 101.

Claims

1. An adjustable high-temperature, high-power alkali metal heat pipe experimental system, characterized in that: It includes an adjustable high-temperature gravity heat pipe body (1), a piping system (2), a data acquisition device (3), a cooling water supply system (4), a heating system (5), and a control knob adjustment component (6). The adjustable high-temperature gravity heat pipe body (1) includes a heat pipe (101) and a cooling jacket (102). The heat pipe (101) is divided into a heating section, an adiabatic section and a condensing section along the axial direction from bottom to top. The cooling jacket (102) is disposed outside the condensing section of the heat pipe (101). The control knob type adjustment component (6) is connected to the cooling jacket (102) and is used to drive the cooling jacket (102) to slide along the axial direction of the heat pipe (101) to adjust the axial position of the cooling jacket (102) surrounding the heat pipe (101). The pipeline system (2) and the cooling water supply system (4) are both connected to the adjustable high-temperature gravity heat pipe body (1), and the heating system (5) is located outside the heating section of the adjustable high-temperature gravity heat pipe body (1). The data acquisition device (3) includes an axially fixed thermocouple assembly (310), a circumferentially fixed thermocouple assembly (311), and a top movable thermocouple device (301). The axially fixed thermocouple assembly (310) is axially spaced along the outer wall of the heat pipe (101). The circumferentially fixed thermocouple assembly (311) is circumferentially arranged along the bottom of the heating section of the heat pipe (101). The top movable thermocouple device (301) is located at the top of the heat pipe (101) and includes a movable thermocouple (304) disposed inside the heat pipe (101) and a drive assembly connected to the movable thermocouple (304).

2. The adjustable high-temperature high-power alkali metal heat pipe experimental system according to claim 1, characterized in that: Both ends of the heat pipe (101) are provided with a wire mesh liquid absorber (107), and the wire mesh liquid absorber (107) has a multi-layer structure.

3. The adjustable high-temperature high-power alkali metal heat pipe experimental system according to claim 1, characterized in that: The cooling jacket (102) is provided with an embedded groove (108). The cooling jacket (102) includes a granite jacket (105) and a cooling water jacket (104) arranged sequentially from the inside to the outside. The cooling water jacket (104) is provided with a first cooling water inlet (103) and a first cooling water outlet (106) on both sides. The first cooling water inlet (103) and the first cooling water outlet (106) are both connected to the cooling water supply system (4). The control knob adjustment assembly (6) includes a slider (61), which is slidably connected to a slide rail (63). Both ends of the slide rail (63) are connected to the condensation section of the heat pipe (101). The bottom of the slider (61) is connected to the cooling jacket (102). The top of the slider (61) is provided with a protrusion (62), which is located in the embedding groove (108) and is used to push and pull the cooling jacket (102) so that it slides synchronously along the outer wall of the heat pipe (101).

4. The adjustable high-temperature high-power alkali metal heat pipe experimental system according to claim 1, characterized in that: The pipeline system (2) includes a main gas pipeline (213), a pressure transmitter (212), a main gas control valve (211), and a sodium working fluid filling device (207); the pressure transmitter (212) is installed on the main gas pipeline (213), one end of the main gas pipeline (213) is connected to the condensing section of the heat pipe (101) through a first pipeline interface (214), and the other end of the main gas pipeline (213) is connected to the main gas control valve (211) and the sodium working fluid filling device (207) through a three-way pipe respectively, and the main gas control valve (211) is connected to the gas device (201) through a first pipeline (215); The sodium working fluid filling device (207) includes a sodium storage tube (209), the top of which is provided with a feeding port. One end of the sodium storage tube (209) is connected to one end of the lower control valve (208) of the sodium storage tube, and the other end of the lower control valve (208) of the sodium storage tube is connected to the main gas pipeline (213). The other end of the sodium storage tube (209) is connected to one end of the upper control valve (210) of the sodium storage tube, and the other end of the upper control valve (210) of the sodium storage tube is connected to the first pipeline (215) through a second pipeline (216). The outer wall of the sodium storage tube (209) is provided with a heating wire for heating. The gas circuit device (201) includes an argon gas supply device (202), an argon gas control valve (204), and a vacuum pump (203). The output end of the argon gas supply device (202) is connected to a third pipeline (217). An argon gas control valve (204) is installed on the third pipeline (217). The third pipeline (217) is connected to a fourth pipeline (218) and a fifth pipeline (219). The fourth pipeline (218) is connected to the vacuum pump (203). A vacuum pump control valve (205) is installed on the fourth pipeline (218). The fifth pipeline (219) is connected to the main gas circuit control valve (211) through a first pipeline (215). A pressure gauge (206) is installed on the fifth pipeline (219).

5. The adjustable high-temperature high-power alkali metal heat pipe experimental system according to claim 1, characterized in that: The drive assembly includes a clamping device (303) connected to the movable thermocouple (304), one end of which is connected to a hand-cranked lead screw slide (302), which is mounted on a lead screw (312), and both ends of the lead screw (312) are mounted on a vertical fixed platform (313). The top movable thermocouple device (301) also includes a sealing assembly, which is disposed on the top of the heat pipe (101). The sealing assembly includes a sealing head (305), a sealing cap (306), and a sealing base (307). The sealing base (307) is connected to the heat dissipation pipe (309), and the heat dissipation pipe (309) is connected to the top end of the heat pipe (101). A trapezoidal groove is provided between the sealing head (305) and the sealing base (307), and an O-ring (308) is provided in the trapezoidal groove. The sealing cap (306) and the sealing base (307) are locked together by a threaded connection, and the O-ring (308) is squeezed to make it fit tightly against the movable thermocouple (304).

6. The adjustable high-temperature high-power alkali metal heat pipe experimental system according to claim 1, characterized in that: The cooling water supply system (4) includes a water tank (403), a water pump (401), and a flow meter (402). The water tank (403) is connected to the first cooling water inlet (103) and the first cooling water outlet (106) of the cooling jacket (102). The water pump (401) is installed on the connecting pipe between the water tank (403) and the first cooling water inlet (103). The flow meter (402) is installed on the connecting pipe between the water pump (401) and the first cooling water inlet (103).

7. The adjustable high-temperature high-power alkali metal heat pipe experimental system according to claim 1, characterized in that: The heating system (5) includes a sleeve (501), a DC power supply (502), a controller (503), an isolation cover (504), and a nitrogen system (509). The sleeve (501) is located outside the heating section of the heat pipe (101). The controller (503) is electrically connected to the DC power supply (502) and has a full system data acquisition function. The isolation cover (504) is disposed outside the adjustable high-temperature gravity heat pipe body (1). The isolation cover (504) is provided with a second cooling water outlet (512), a second cooling water inlet (513), a heating power supply positive terminal interface (507), a heating power supply negative terminal interface (508), a second pipeline interface (511), and a heating system gas pipeline interface (510) on both sides respectively. The isolation cover (504) is connected to the cooling water supply system through the second cooling water outlet (512) and the second cooling water inlet (513). (4) Connection; The DC power supply (502) is connected to the terminal block (505) through the positive terminal block (507) and the negative terminal block (508) of the heating power supply. The terminal block (505) is located at the upper and lower ends of the sleeve (501); The isolation cover (504) is connected to the main gas pipeline (213) of the pipeline system (2) through the second pipeline interface (511); The isolation cover (504) is connected to the nitrogen system (509) through the heating system gas pipeline interface (510); The sleeve (501) is provided with extension tubes (506) on both sides. The inner wall of the sleeve (501) is provided with radial through holes. A pluggable positioning pin is provided in the radial through holes. The outer wall of the heating section of the heat pipe (101) is provided with multiple positioning blind holes along the axial direction to cooperate with the positioning pins, which are used to adjust the effective heating length of the heating section.

8. An adjustable high-temperature, high-power alkali metal heat pipe experimental method, employing the adjustable high-temperature, high-power alkali metal heat pipe experimental system according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Preparations before the experiment: The adjustable high-temperature gravity heat pipe body (1) is tested for air tightness and evacuated. Then, alkali metal working medium is filled into the heat pipe (101) through sodium working medium filling device (207). S2. Conduct intermittent boiling experiment: The heating system (5) is started to heat the heating section. The axial position of the cooling jacket (102) surrounding the heat pipe (101) is adjusted by the control knob adjustment component (6). The axial temperature of the outer wall of the heat pipe (101), the circumferential temperature of the bottom of the heating section and the axial vapor-liquid temperature distribution inside the heat pipe (101) are collected by the data acquisition device (3). The occurrence of intermittent boiling is determined based on the collected temperature data, and the filling rate of the alkali metal working fluid is adjusted. S3. Post-experiment work: After the temperature measurement is completed, the heating system (5) is turned off, protective gas is introduced into the experimental system and cooled, and cleaning and secondary filling of the working fluid are carried out.

9. The experimental method for adjustable high-temperature high-power alkali metal heat pipe according to claim 8, characterized in that: In step S1, the airtightness test includes: filling the heat pipe (101) with argon gas to the test pressure and maintaining the pressure for observation; the vacuuming includes: continuously evacuating the heat pipe (101) until the vacuum degree reaches 10. -3 Pa; The filling of the alkali metal working medium includes: putting solid sodium blocks into the sodium storage tube (209), evacuating the sodium storage tube (209) three times and filling it with argon three times to remove impurity gases, evacuating it three times again after sealing and leak testing, heating it to melt the sodium and keeping the temperature stable, filling it with argon to press the liquid sodium into the heat pipe (101), and finally weighing it to calculate the mass of the working medium; In step S2, before starting the heating system (5), the air inside the isolation cover (504) is first extracted by a vacuum pump (203) and nitrogen is introduced to form an inert protective atmosphere. Then, the adjustable high-temperature gravity heat pipe body (1) is subjected to three vacuuming and three argon filling operations to make the vacuum degree inside the adjustable high-temperature gravity heat pipe body (1) reach 10. -3 Pa, and then the heating section is heated by radiation heat exchange through the sleeve (501); the data acquisition system in the controller (503) is run to record the heating start time and heating power; In S2, the temperature data collected includes: when the heat pipe (101) undergoes intermittent boiling, the moving thermocouple (304) is gradually moved upward by the driving component to measure the vapor-liquid temperature distribution; the pressure data of the condensing section inside the heat pipe (101) is collected in real time by the pressure transmitter (212), and then... The saturation pressure and saturation temperature inside the heat pipe (101) are obtained after correction, where, The saturation pressure inside the heat pipe (101) is expressed in Pa. The pressure in the condensing section of the heat pipe (101) measured by the pressure transmitter is expressed in Pa. This pressure is used as a temperature reference to distinguish different heat transfer states. When the moving thermocouple (304) moves from the liquid phase region to the gas phase region, the actual height of the vapor-liquid interface is determined according to the temperature jump point. In S3, after the temperature measurement is completed, the moving thermocouple (304) is returned to its initial position; after the experiment is completed, the heating system (5) is turned off, and argon gas is introduced into the experimental system to maintain positive pressure and cool naturally; after the experiment is completed, anhydrous ethanol is replaced in the sodium storage tube (209) and injected into the adjustable high-temperature gravity heat pipe body (1) for cleaning; after the system cools down, the working medium is refilled through the sodium working medium filling device (207). During the second filling, the storage tank is heated first to liquefy the alkali metal, and then argon gas is used to press the liquid metal into the adjustable high-temperature gravity heat pipe body (1). Then, the excess argon gas is extracted to the required pressure by the vacuum pump (203).

10. The experimental method for adjustable high-temperature high-power alkali metal heat pipe according to claim 9, characterized in that: The S2 further includes: starting the experiment with a low filling rate according to the experimental design conditions, and increasing the filling rate by injecting liquid sodium through the argon gas supply device (202) in subsequent experiments.

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