Experimental device for natural convection of lead-bismuth alloy fluid

Abstract

The utility model relates to the technical field of lead-bismuth alloy convection, and discloses a lead-bismuth alloy fluid natural convection experimental device which comprises a shell, an electric heating assembly, a cooling assembly, a liquid storage tank, a temperature acquisition assembly and a coating heat preservation layer. A convection cavity is formed in the shell, a liquid injection switch valve is arranged at the bottom of the shell to achieve filling and discharging of fluid, the electric heating assembly is assembled on one side of the shell, the cooling assembly is arranged on the other side, away from the electric heating assembly, of the shell, the liquid storage tank is communicated with the liquid injection switch valve through a pipeline, and the temperature collecting assemblies are evenly distributed on the inner surface of the shell. The outer surfaces of the shell, the electric heating assembly and the cooling assembly are completely wrapped with the wrapping heat preservation layer, and outward loss of heat is reduced; according to the structure, the overall size of the device is effectively reduced, the complex matching design of a traditional loop type or large-scale experiment facility is eliminated, the cost of construction, operation and maintenance of the device and the investment of manpower and material resources are greatly reduced, and meanwhile the compact integrated design adapts to the laboratory-level small-scale research requirement.

Description

Technical Field

[0001] This utility model relates to the field of lead-bismuth alloy convection technology, specifically to an experimental device for natural convection of lead-bismuth alloy fluid. Background Technology

[0002] Lead-bismuth eutectic alloys, as the core liquid metal coolant of fourth-generation nuclear reactors, have become a key working fluid for studying the natural convection heat transfer mechanism of liquid metals with low Prandtl numbers due to their excellent physical properties such as high boiling point, high thermal conductivity, and low viscosity. Related natural convection experimental studies are also an important foundation for the thermal-hydraulic design and numerical model verification of nuclear reactors.

[0003] Currently, most existing lead-bismuth alloy natural convection experimental devices in the industry are loop-type or large-scale experimental facilities. For example, the invention patent with announcement number CN114878632B discloses "an experimental section and method for liquid lead-bismuth-molten salt convection heat transfer with vertical tube bundle structure". It adopts a shell-and-tube heat exchanger configuration and integrates multiple components such as lead-bismuth inlet / outlet tube boxes, heat exchange tube bundles, molten salt annular distributors, and experimental section cylinders. It forms a dual-fluid circulation loop of lead-bismuth on the tube side and molten salt on the shell side. It requires the installation of magnetic pumps, long-distance high-temperature and corrosion-resistant pipelines, and independent fluid distribution and flow equalization structures. The system has a high degree of integration and a complex overall structure. Not only is the initial investment cost high, but the subsequent operation, maintenance, and parameter control also require a lot of manpower and resources. The overall operating cost remains high and it is difficult to meet the needs of laboratory-scale, high-precision basic mechanism research.

[0004] Therefore, existing technologies still need to be improved and developed. Utility Model Content

[0005] In view of the shortcomings of the prior art, the purpose of this utility model is to provide an experimental device for natural convection of lead-bismuth alloy fluid, which aims to solve the problem that the existing experimental devices for natural convection of lead-bismuth alloy are difficult to adapt to laboratory research.

[0006] The technical solution adopted by this utility model to solve the technical problem is as follows:

[0007] An experimental apparatus for natural convection of a lead-bismuth alloy fluid, comprising:

[0008] The housing has an internal convection chamber for filling lead-bismuth alloy fluid; a liquid injection switch valve is provided at the bottom of the housing.

[0009] An electric heating component, disposed on one side of the housing, is used to heat the lead-bismuth alloy fluid;

[0010] A cooling assembly, located on the side of the housing away from the electric heating assembly, is used to cool the lead-bismuth alloy fluid;

[0011] The storage tank is connected to the liquid injection switch valve via a pipeline;

[0012] Temperature acquisition components are evenly distributed on the inner surface of the housing and are electrically connected to an external acquisition device via connecting wires.

[0013] An insulation layer is applied to the outer surfaces of the housing, the electric heating component, and the cooling component.

[0014] Furthermore, the interior of the housing is provided with a covering air cavity, which is located at the top of the convection cavity and is connected to the convection cavity.

[0015] Furthermore, it also includes:

[0016] An expansion valve is connected to the covered air chamber via a pipe;

[0017] An expansion tank is connected to the end of the expansion valve away from the housing via a pipe.

[0018] Furthermore, the electric heating assembly includes:

[0019] An electric heater is disposed on the outer surface of the housing;

[0020] A switching power supply is connected to the electric heater via a connecting wire.

[0021] Furthermore, the electric heater is an electric heating belt, an electric heating element, or an electric heating plate.

[0022] Furthermore, the cooling assembly includes:

[0023] A condenser coil is located on the side of the housing away from the electric heating assembly;

[0024] The heat exchanger is connected to the outlet of the condenser coil via a pipe;

[0025] A circulating pump is connected to the outlet of the heat exchanger via a pipeline; the outlet of the circulating pump is connected to the inlet of the condensing coil.

[0026] Furthermore, a flow meter is installed at the outlet of the heat exchanger.

[0027] Furthermore, the condenser coil is a single-layer condenser coil or a multi-layer condenser coil.

[0028] Furthermore, the temperature acquisition component includes:

[0029] The first thermocouple assembly is disposed on the inner wall of the housing near the electric heating assembly;

[0030] The second thermocouple assembly is disposed on the inner wall of the housing near the cooling assembly;

[0031] Multiple third thermocouple groups are arranged laterally at intervals on the inner wall of the housing, which is perpendicular to the mounting wall of the electric heating assembly.

[0032] Furthermore, the first thermocouple group, the second thermocouple group, and the third thermocouple group each include multiple vertically spaced thermocouple sensors.

[0033] Compared with the prior art, the beneficial effects of this utility model are:

[0034] In this invention, a lead-bismuth alloy fluid is filled into a single convection cavity within the shell. An electric heating component is installed on one side of the cavity, and a cooling component is installed on the other side. A storage tank is connected to an injection valve at the bottom of the cavity. A temperature acquisition component is placed on the inner surface of the cavity. The shell, electric heating component, and cooling component are all covered with an insulation layer. The entire process completes the natural convection experiment of the lead-bismuth alloy fluid within a single cavity. The above-mentioned single-fluid closed-cavity minimalist structure eliminates the need for complex dual-fluid circulation loops, heat exchange tube bundles, and fluid distribution and equalization structures. The closed injection of the lead-bismuth alloy single medium is achieved solely through the shell forming an independent convection cavity, combined with a storage tank and an injection valve. This eliminates the need for various supporting pipeline components, significantly reducing construction costs and assembly complexity, thereby reducing the overall size of the device. It also eliminates the complex supporting designs of traditional loop-type or large-scale experimental facilities, greatly reducing the cost and manpower and material resources required for device construction, operation, and maintenance. At the same time, the compact integrated design is suitable for laboratory-scale research needs. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the overall structure of this utility model.

[0036] Figure 2 This is a schematic diagram of the structure of the shell, electric heater and condenser coil of this utility model.

[0037] Figure 3 This is a schematic diagram of the electric heating component structure of this utility model.

[0038] Figure 4 This is a schematic diagram of the cooling component structure of this utility model.

[0039] The numbers in the diagram represent: 1. Shell; 11. Convection chamber; 12. Liquid injection switch valve; 13. Covering gas chamber; 2. Electric heating component; 21. Electric heater; 22. Switching power supply; 3. Cooling component; 31. Condensing coil; 32. Heat exchanger; 33. Circulating pump; 34. Flow meter; 4. Liquid storage tank; 5. Covering insulation layer; 6. Expansion valve; 7. Expansion box. Detailed Implementation

[0040] To make the objectives, technical solutions, and effects of this utility model clearer and more explicit, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this utility model and are not intended to limit this utility model.

[0041] In the description of this utility model, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.

[0042] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0043] In view of the shortcomings of the prior art, this embodiment provides an experimental apparatus for natural convection of lead-bismuth alloy fluid, which can be referred to as follows:

[0044] As attached Figure 1As shown, an experimental apparatus for natural convection of lead-bismuth alloy fluid includes a shell 1, an electric heating component 2, a cooling component 3, a storage tank 4, a temperature acquisition component, and a thermal insulation layer 5. The shell 1 has a convection cavity 11 inside for filling with lead-bismuth alloy fluid. A liquid injection valve 12 is located at the bottom of the shell 1 to allow for fluid injection and discharge. The electric heating component 2 is mounted on one side of the shell 1 to provide a heat source for the lead-bismuth alloy fluid. The cooling component 3 is located on the other side of the shell 1 away from the electric heating component 2 to cool the lead-bismuth alloy fluid. The storage tank 4 is connected to the liquid injection valve 12 via a pipe to replenish the convection cavity 11 with lead-bismuth alloy fluid. The temperature acquisition component is evenly distributed on the inner surface of the shell 1 and is electrically connected to an external acquisition device via a connecting wire to achieve accurate fluid temperature acquisition. The thermal insulation layer 5 completely covers the outer surfaces of the shell 1, the electric heating component 2, and the cooling component 3 to reduce heat loss.

[0045] The shell 1 is a rigid, sealed structure that is resistant to high temperatures and corrosion. The volume of the convection cavity 11 is adapted to the needs of small-scale laboratory research, and the overall structure is compact and easy to operate. The electric heating component 2 is a temperature-controllable heating structure that can adjust the heating power according to experimental needs to achieve precise temperature control. The cooling component 3 is a high-efficiency heat exchange structure that can quickly remove heat from the fluid and form a stable temperature gradient. The liquid storage tank 4 is a sealed liquid storage structure with a volume that matches the convection cavity 11, which can realize the quantitative filling of lead-bismuth alloy fluid. The temperature acquisition component is a high-precision temperature measuring element with fast response speed, which can capture fluid temperature changes in real time. The insulation layer 5 is made of high-temperature resistant heat insulation material with excellent heat insulation performance, which can effectively reduce heat loss during the experiment and ensure the accuracy of the experiment.

[0046] Specifically, before the experiment, the liquid injection valve 12 at the bottom of the shell 1 is opened, and the lead-bismuth alloy fluid in the storage tank 4 is injected into the convection cavity 11 of the shell 1 through the pipe. After a certain volume is injected, the liquid injection valve 12 is closed to complete the filling of the experimental medium. Then, the electric heating component 2 is activated to heat the lead-bismuth alloy fluid on one side of the shell 1, while the cooling component 3 is activated to cool the fluid on the other side of the shell 1, so that the lead-bismuth alloy fluid in the convection cavity 11 forms a stable hot and cold temperature gradient, thereby triggering the natural convection phenomenon. The temperature acquisition component deployed on the inner surface of the shell 1 collects the fluid temperature data at different positions in the convection cavity 11 in real time, and transmits the data to the external acquisition device for recording and analysis through the connecting line. The insulation layer 5 is wrapped around the shell 1, the electric heating component 2 and the cooling component 3 to reduce the heat loss from the heating end and prevent the cooling end from absorbing external heat, ensuring the stability of the temperature gradient in the convection cavity 11 and ensuring the smooth progress of the natural convection experiment. After the experiment, the liquid injection valve 12 is opened to drain the lead-bismuth alloy fluid in the convection cavity 11 back into the storage tank 4, completing the experimental procedure.

[0047] Compared with existing technologies, traditional lead-bismuth alloy natural convection experimental devices are mostly loop-type or large-scale facilities with high system integration, complex supporting equipment, high construction and operation costs, and cumbersome operation, making them unsuitable for laboratory-scale, high-precision fundamental mechanism research. This solution, through a combination design of "compact shell 1 + single-sided heating and single-sided cooling + integrated temperature measurement and insulation," creates a small-scale experimental device, solving the core pain points of "large device size, high cost, complex operation, and unsuitability for small-scale laboratory research."

[0048] Through the above technical solution, this application adopts a minimalist single-fluid closed-cavity structure, eliminating the complex dual-fluid circulation loop, heat exchange tube bundle, and fluid distribution and equalization structure. It achieves closed-loop injection of lead-bismuth alloy as a single medium solely through the shell 1 forming an independent convection chamber 11, which, together with the storage tank 4 and the injection switch valve 12, eliminates the need for magnetic pumps, long-distance corrosion-resistant pipelines, and other supporting components, significantly reducing the customized processing costs and component assembly complexity during the construction phase. It enables precise laboratory-level experimental research on the natural convection of lead-bismuth alloy fluid. The compact overall structure adapts to the needs of small-scale laboratory research, significantly reducing the construction and footprint costs of the device, while simplifying the operation process and reducing the manpower and material resources required for operation and maintenance. Furthermore, the device only requires the control of the temperature boundary of the lead-bismuth alloy single medium, achieved through the separate electric heating and cooling components 3 on both sides of the shell 1, combined with a fully enclosed insulation layer. This device can accurately and stably control the boundary conditions of hot and cold walls, effectively reducing environmental heat dissipation interference. After liquid injection, it forms a closed convection system without external circulation interference, ensuring the purity of lead-bismuth alloy natural convection experiments. The temperature acquisition components uniformly distributed on the inner surface of shell 1 are also more in line with the temperature field measurement requirements of single-medium natural convection, improving measurement accuracy and the reproducibility and comparability of experimental data. In addition, the device does not require simultaneous control of the temperature, flow rate and pressure of two fluids during operation, making parameter adjustment and equipment maintenance less difficult, reducing manpower and material consumption, and significantly reducing subsequent operating costs. Moreover, the liquid injection and experimental operation procedures are simple. Its overall design is fully adapted to the laboratory-scale, high-precision research needs of the basic mechanism of natural convection of lead-bismuth alloy low Prandtl number liquid metals, solving the problems of poor device adaptability and inability to conduct accurate research on single-medium natural convection in the background technology.

[0049] In this embodiment, as shown in the appendix Figure 1 and attached Figure 2 As shown, the interior of the housing 1 is provided with a covering air cavity 13, which is located at the top of the convection cavity 11 and is connected to the convection cavity 11 to form a cavity structure with gas-liquid stratification.

[0050] The covering air cavity 13 is a cavity at the top of the shell 1. Its volume is reasonably designed according to the size of the convection cavity 11. It is filled with an inert protective gas to prevent the lead-bismuth alloy fluid from oxidizing when it comes into contact with air. The covering air cavity 13 is seamlessly connected to the convection cavity 11 without any obvious separation structure, which ensures that the lead-bismuth alloy fluid can extend freely upward when it is heated and expands, while not affecting the natural convection flow field in the convection cavity 11.

[0051] Specifically, during the processing of the shell 1, the convection cavity 11 and the top covering gas cavity 13 are integrally formed. Before the experiment, the covering gas cavity 13 is filled with inert protective gases such as argon and nitrogen. Then, lead-bismuth alloy fluid is added to the convection cavity 11 through the liquid injection switch valve 12. The fluid level is lower than the bottom of the covering gas cavity 13, so that a certain amount of gas phase space is retained at the top of the convection cavity 11. When the electric heating component 2 heats the lead-bismuth alloy fluid, the fluid expands in volume due to heat, and the liquid level will rise slightly and enter the area of ​​the covering gas cavity 13. The covering gas cavity 13 is the thermal expansion area of ​​the fluid. The expansion provides a buffer space to prevent the fluid from generating excessive pressure due to expansion, which could damage the shell 1. At the same time, the inert protective gas in the covering gas chamber 13 floats on the surface of the lead-bismuth alloy fluid, forming a gas phase isolation layer that completely isolates the fluid from contact with the outside air, preventing the lead-bismuth alloy from oxidizing at high temperatures and avoiding the generation of oxide impurities that could affect the physical properties of the experimental medium, thus ensuring the accuracy of the experiment. The connection design between the covering gas chamber 13 and the convection chamber 11 will not obstruct the natural convection flow of the fluid in the convection chamber 11, ensuring the integrity of the flow field.

[0052] Through the above technical solutions, the covering gas cavity 13 of this application provides a buffer space for the thermal expansion of the lead-bismuth alloy fluid, effectively releasing the pressure generated by the high-temperature expansion of the fluid, preventing damage to the shell 1 due to excessive pressure, and improving the safety and service life of the device. The inert protective gas filled inside forms a gas phase isolation layer, completely isolating the lead-bismuth alloy fluid from contact with air, preventing the fluid from oxidizing and deteriorating at high temperatures, ensuring the purity and physical property stability of the experimental medium, and improving the accuracy of experimental data. The seamless connection design with the convection cavity 11 does not obstruct or interfere with the natural convection flow field of the fluid in the convection cavity 11, ensuring the integrity of the experimental flow field and providing real flow field data for the study of heat transfer mechanism. The gas-liquid stratified cavity structure design is simple and integrally formed with the shell 1, eliminating the need for additional sealing components and reducing the processing and assembly costs of the device. The volume of the covering gas cavity 13 can be flexibly designed according to experimental requirements and the size of the convection cavity 11, adapting to small-scale experimental devices of different specifications and improving the versatility of the structure. The inert protective gas can be recycled, reducing the cost of experimental consumables and conforming to the concept of green experimentation.

[0053] In this embodiment, as shown in the appendix Figure 1As shown, the experimental apparatus for natural convection of lead-bismuth alloy fluid also includes an expansion valve 6 and an expansion chamber 7. The expansion valve 6 is connected to the covered air chamber 13 through a pipe, and the expansion chamber 7 is connected to the end of the expansion valve 6 away from the shell 1 through a pipe, forming a thermal expansion compensation system for the lead-bismuth alloy fluid.

[0054] Among them, the expansion valve 6 is an adjustable pressure control valve with pressure sensing and on / off adjustment functions. It can automatically adjust the opening degree according to the pressure change in the covered air chamber 13 to achieve precise pressure control. The expansion box 7 is a sealed pressure-bearing cavity, which is pre-filled with inert protective gas. Its volume is much larger than that of the covered air chamber 13, providing sufficient buffer space for the thermal expansion of the lead-bismuth alloy fluid. The expansion valve 6 and the expansion box 7 are connected by high-temperature and corrosion-resistant metal pipes to ensure sealing performance and pressure bearing capacity.

[0055] Specifically, before the experiment, the same inert protective gas is filled into the covering gas chamber 13 and the expansion chamber 7, and the initial pressure is adjusted by the expansion valve 6 to keep the system in a stable pressure state. When the electric heating component 2 heats up, causing the lead-bismuth alloy fluid to expand, the liquid level in the convection chamber 11 rises and enters the covering gas chamber 13, and the pressure in the covering gas chamber 13 increases accordingly. When the pressure reaches the preset value of the expansion valve 6, the expansion valve 6 opens automatically, and the inert gas in the covering gas chamber 13 enters the expansion chamber 7 through the pipe, causing the pressure in the covering gas chamber 13 to drop rapidly and providing sufficient space for fluid expansion. After the experiment, the lead-bismuth alloy fluid cools and contracts, the liquid level drops, the pressure in the covering gas chamber 13 decreases, the expansion valve 6 opens automatically, and the inert gas in the expansion chamber 7 flows back to the covering gas chamber 13 to replenish the gas phase space and maintain the system pressure stability. Throughout the process, the expansion valve 6 automatically adjusts according to the pressure changes to achieve real-time control of the pressure in the covering gas chamber 13 without manual intervention.

[0056] Through the above technical solutions, the expansion chamber 7 of this application provides a large-capacity buffer space for fluid thermal expansion, forming a double buffer with the covering gas chamber 13, completely solving the pressure problem of fluid expansion in small-scale devices, and significantly improving the pressure resistance and safety of the device; the automatic pressure regulation function of the expansion valve 6 enables real-time and precise control of the pressure of the covering gas chamber 13 without manual intervention, simplifying the experimental operation process and improving experimental efficiency; the entire system is filled with inert protective gas, forming a closed gas phase circulation, continuously isolating the lead-bismuth alloy fluid from contact with air, further preventing fluid oxidation and ensuring the purity of the experimental medium; the preset pressure of the expansion valve 6 can be flexibly adjusted according to the experimental conditions, adapting to the experimental requirements of different heating temperatures and different fluid filling volumes, improving the adaptability and flexibility of the device; the closed gas phase circulation system allows the inert protective gas to be reused, reducing the cost of experimental consumables, while avoiding the environmental impact caused by gas leakage.

[0057] Furthermore, the covering air chamber 13 can be a flexible and high-temperature resistant sealed airbag, which is filled with gas. One end of the sealed airbag is connected to the expansion valve 6 through the shell 1 via a pipe. The sealed airbag is made of a high-temperature resistant flexible material. When the lead-bismuth alloy fluid expands at high temperature, it can squeeze the sealed airbag, so that the gas in the sealed airbag enters the expansion box 7 through the pipe and the expansion valve 6.

[0058] In this embodiment, as shown in the appendix Figure 3 As shown, the electric heating assembly 2 includes an electric heater 21 and a switching power supply 22. The electric heater 21 is disposed on the outer surface of the housing 1, and the switching power supply 22 is connected to the electric heater 21 through a connecting wire to form a temperature-controllable heating system.

[0059] Among them, the electric heater 21 is a close-fitting heating structure that is in close contact with the outer surface of the shell 1. It has a large contact area with the shell 1 and high heat exchange efficiency, which can quickly transfer heat to the lead-bismuth alloy fluid inside the shell 1; the switching power supply 22 is an adjustable power regulated power supply with voltage and current regulation and on / off control functions, which can accurately regulate the heating power of the electric heater 21 and achieve precise control of the heating temperature; the connecting wire is a high-temperature resistant insulated wire to ensure the safety of the power supply process.

[0060] Specifically, during assembly, the electric heater 21 is tightly fitted and fixed to the outer surface of the designated side of the housing 1 to ensure seamless contact and reduce heat loss during heating. The switching power supply 22 is electrically connected to the electric heater 21 through a high-temperature resistant insulated wire. Before the experiment, the output power of the switching power supply 22 is adjusted according to the experimental requirements to set the heating temperature of the electric heater 21. During the experiment, the switching power supply 22 is turned on to supply power to the electric heater 21. The electric heater 21 converts electrical energy into heat energy, which is transferred to the lead-bismuth alloy fluid in the convection cavity 11 through heat conduction on the wall of the housing 1, thereby heating the fluid. During the experiment, the heating power can be adjusted in real time through the switching power supply 22 to change the heating temperature, thereby controlling the temperature gradient in the convection cavity 11 to meet the parameter requirements of different experimental conditions. After the experiment, the switching power supply 22 is turned off, the electric heater 21 stops heating, and the heating process is completed.

[0061] Through the above technical solutions, the externally attached design of the electric heater 21 of this application is seamlessly integrated with the shell 1, increasing the contact area and improving the heat transfer efficiency. It can quickly provide heat to the lead-bismuth alloy fluid, shorten the experimental preparation time, and improve experimental efficiency. The externally attached structure facilitates the disassembly and maintenance of the electric heater 21. If the heater malfunctions, it can be directly replaced without disassembling the shell 1, reducing maintenance costs. The switching power supply 22 can achieve precise adjustment of the heating power, thereby controlling the heating temperature in real time. It can flexibly adjust the temperature gradient in the convection cavity 11 according to experimental needs, meeting the experimental parameter requirements of different heat transfer mechanism studies. The heating component is located on the outside of the shell 1, without occupying the internal space of the convection cavity 11, and does not interfere with the natural convection flow field of the fluid, ensuring the integrity of the experimental flow field and improving the authenticity of the experimental data.

[0062] In this embodiment, the electric heater 21 is an electric heating belt, an electric heating plate, or an electric heating plate, and the appropriate heating method can be flexibly selected according to experimental requirements.

[0063] Among them, the electric heating strip is a flexible strip heating structure that can be bent and fit the outer surface of the shell 1 with different curved surfaces, and is suitable for irregularly shaped shells 1 with a high degree of fit; the electric heating sheet is a thin sheet heating structure with small thickness and light weight, uniform contact area with the shell 1, and high heat conduction efficiency, and is suitable for flat shells 1; the electric heating plate is a thick plate heating structure with high power, high heating temperature, and good thermal stability, and is suitable for experimental conditions that require high-temperature heating; all three types of electric heaters 21 are made of high-temperature resistant and corrosion-resistant materials, which are suitable for the use requirements of high-temperature experiments on lead-bismuth alloys, and all can be matched with the switching power supply 22 to realize power adjustment.

[0064] In this embodiment, as shown in the appendix Figure 4 As shown, the cooling assembly 3 includes a condenser coil 31, a heat exchanger 32, and a circulating pump 33. The condenser coil 31 is located on the side of the housing 1 away from the electric heating assembly 2. The heat exchanger 32 is connected to the outlet of the condenser coil 31 through a pipe. The outlet of the heat exchanger 32 is connected to the inlet of the circulating pump 33 through a pipe, and the outlet of the circulating pump 33 is connected to the inlet of the condenser coil 31, forming a closed-loop cooling system.

[0065] The condenser coil 31 is a spiral or serpentine tubular structure that fits tightly against the outer surface of the shell 1. Cooling medium flows through the coil, forming a highly efficient heat exchange with the shell 1, which can quickly remove the heat from the lead-bismuth alloy fluid. The circulating pump 33 is a high-temperature resistant, high-lift power pump that provides power for the circulation of the cooling medium. The circulation flow rate can be adjusted to control the cooling efficiency. The heat exchanger 32 is a partitioned heat exchange structure that can quickly transfer the heat carried by the cooling medium to the external cooling water source, achieving rapid cooling of the cooling medium. All components are connected by high-temperature resistant, well-sealed pipes to form a closed circulation channel, ensuring no leakage of the cooling medium and allowing for recycling.

[0066] Specifically, during assembly, the condenser coil 31 is tightly fitted and fixed to the outer surface of the shell 1 on the side away from the electric heating component 2, ensuring seamless contact with the shell 1. The condenser coil 31, heat exchanger 32, and circulating pump 33 are connected in sequence through pipes to form a closed-loop circulation circuit. Cooling water, heat transfer oil, and other cooling media are injected into the circuit. During the experiment, the circulating pump 33 is started. Under the power of the circulating pump 33, the cooling media exchanges heat with the shell 1, absorbing the heat transferred by the lead-bismuth alloy fluid, and its temperature rises. The heated cooling media flows out from the outlet of the condenser coil 31, enters the heat exchanger 32 through pipes, exchanges heat with the external cooling water source in the heat exchanger 32, releases heat, and its temperature drops. It is then transported back to the condenser coil 31 by the circulating pump 33. The cooled cooling media flows back into the condenser coil 31, completing one cooling cycle. This cycle continues, achieving continuous cooling of the lead-bismuth alloy fluid on one side of the shell 1 and forming a stable temperature gradient with the heating side.

[0067] Through the above technical solutions, the closed-loop structure of this application enables the cooling medium to be recycled, significantly reducing the consumption of cooling medium and lowering the cost of experimental consumables, while avoiding environmental pollution and equipment damage caused by cooling medium leakage; the condenser coil 31 is tightly attached to the outer surface of the shell 1 to form a highly efficient heat exchange, which can quickly remove the heat of the lead-bismuth alloy fluid, improve cooling efficiency, and shorten the formation time of the temperature gradient; the circulating pump 33 can adjust the circulation flow rate of the cooling medium to achieve precise control of cooling efficiency, and can be matched with the heating power of the electric heating component 2 to flexibly adjust the temperature gradient in the convection cavity 11 to meet the parameter requirements of different experimental conditions; the heat exchanger 32 achieves rapid cooling of the cooling medium, ensures the temperature stability of the cooling medium entering the condenser coil 31, ensures the continuity of the cooling effect, and further improves the stability of the temperature gradient in the convection cavity 11.

[0068] In this embodiment, as shown in the appendix Figure 4 As shown, a flow meter 34 is installed at the outlet of the heat exchanger 32. The flow meter 34 is connected to the inlet of the circulating pump 33 to achieve accurate detection and display of the circulating flow rate of the cooling medium.

[0069] In this embodiment, the condenser coil 31 is a single-layer or multi-layer coil structure, which can be flexibly selected according to the cooling requirements of the experiment to achieve graded control of cooling efficiency.

[0070] Among them, the single-layer condenser coil 31 is a single spiral or serpentine tubular structure that fits onto the outer surface of the shell 1. It has a simple structure, low cooling medium circulation resistance, and is suitable for experimental conditions with low cooling requirements and small temperature gradients. The multi-layer condenser coil 31 consists of multiple spiral or serpentine tubular structures stacked and fitted onto the outer surface of the shell 1. It has a large contact area with the shell 1, high heat exchange efficiency, and a long heat exchange path for the cooling medium. It is suitable for experimental conditions with high cooling requirements and large temperature gradients. The pipe diameter and pipe spacing of both the single-layer and multi-layer condenser coils 31 are designed according to the dimensions of the shell 1 and the physical properties of the cooling medium. They are all made of high-temperature resistant and corrosion-resistant metal tubing, with good sealing performance and no leakage.

[0071] Specifically, when studying the natural convection heat transfer mechanism of lead-bismuth alloy fluid under low temperature gradients and with low cooling requirements, a single-layer condenser coil 31 is selected. Its smaller heat transfer area and lower cooling efficiency can be combined with low-power heating to form a gentle temperature gradient, meeting the experimental requirements. At the same time, the single-layer coil has low circulation resistance, which can reduce the power consumption of the circulation pump 33 and save experimental energy. When studying the natural convection heat transfer mechanism of lead-bismuth alloy fluid under high temperature gradients and with higher cooling requirements, a multi-layer condenser coil 31 is selected. Its larger contact area and longer heat transfer path can achieve efficient heat transfer and quickly remove heat from the fluid. Combined with high-power heating, it forms a steep temperature gradient, meeting the experimental requirements of high-temperature gradients. The installation interface of single-layer and multi-layer condenser coils 31 is unified, allowing for quick replacement according to experimental needs without changing other pipes and components of the cooling system, making operation convenient.

[0072] In this embodiment, the temperature acquisition component includes a first thermocouple group, a second thermocouple group, and multiple third thermocouple groups. The first thermocouple group is disposed on the inner wall of the housing 1 near the electric heating component 2, the second thermocouple group is disposed on the inner wall of the housing 1 near the cooling component 3, and the multiple third thermocouple groups are laterally spaced on the inner wall of the housing 1 perpendicular to the mounting wall of the electric heating component 2, forming a temperature acquisition network covering the entire area. The first thermocouple group, the second thermocouple group, and the multiple third thermocouple groups are all electrically connected to external acquisition devices.

[0073] The first thermocouple group is a temperature measuring group composed of high-temperature thermocouple sensors, which accurately collects temperature data of the inner wall of the convection cavity 11 on the heating side, reflecting the temperature change of the lead-bismuth alloy fluid on the heating side; the second thermocouple group has the same specifications as the first thermocouple group, and accurately collects temperature data of the inner wall of the convection cavity 11 on the cooling side, reflecting the temperature change of the fluid on the cooling side; the third thermocouple group consists of multiple sets of evenly distributed thermocouple sensors, which are laterally spaced on the vertical inner wall of the shell 1, and collect temperature data at different lateral positions of the convection cavity 11, reflecting the lateral temperature distribution of the fluid's natural convection; all thermocouple groups are high-precision, fast-response temperature measuring elements, which are seamlessly attached to the inner surface of the shell 1, with high temperature measurement accuracy and the ability to capture temperature changes in real time.

[0074] Specifically, during assembly, the first thermocouple set is vertically and uniformly arranged along the inner wall of the heating side of the shell 1, the second thermocouple set is vertically and uniformly arranged along the inner wall of the cooling side of the shell 1, and multiple third thermocouple sets are horizontally and uniformly arranged at the same intervals along the inner walls of the shell 1 on both sides perpendicular to the heating wall, forming a full-area temperature acquisition network covering the heating side, cooling side, and horizontal intermediate area of ​​the convection cavity 11. During the experiment, the first thermocouple set collects the fluid temperature at different heights on the heating side in real time, and the second thermocouple set collects the fluid temperature at different heights on the cooling side in real time, which can quickly obtain the temperature gradient and vertical temperature distribution on the hot and cold sides of the convection cavity 11. The multiple third thermocouple sets collect the fluid temperature at different horizontal positions and heights of the convection cavity 11 in real time, which can clearly capture the horizontal temperature changes and flow field characteristics of the lead-bismuth alloy fluid during natural convection. The temperature data collected by all thermocouple sets are transmitted to external acquisition equipment through connecting lines to achieve synchronous recording and analysis, providing comprehensive and detailed temperature data for the study of natural convection heat transfer mechanism.

[0075] In this embodiment, the first thermocouple group, the second thermocouple group, and the third thermocouple group all include multiple vertically spaced thermocouple sensors to achieve accurate temperature acquisition at different vertical heights of the convection cavity 11.

[0076] Among them, the thermocouple sensor is a miniature high-precision temperature measuring element. It is small in size, does not occupy the internal space of the convection cavity 11, and does not interfere with the natural convection flow field of the lead-bismuth alloy fluid. The thermocouple sensors in each group are evenly arranged with equal vertical spacing. The spacing is reasonably designed according to the height of the convection cavity 11 to ensure the uniformity and comprehensiveness of vertical temperature acquisition. The temperature measurement accuracy and response speed of all thermocouple sensors are consistent to ensure the comparability of temperature data at different positions and heights.

[0077] Other embodiments of the present invention will readily occur to those skilled in the art upon consideration of the specification and practice of the solutions disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

Claims

1. An experimental apparatus for natural convection of a lead-bismuth alloy fluid, characterized in that, include: The housing has an internal convection chamber for filling lead-bismuth alloy fluid; a liquid injection switch valve is provided at the bottom of the housing. An electric heating component, disposed on one side of the housing, is used to heat the lead-bismuth alloy fluid; A cooling assembly, located on the side of the housing away from the electric heating assembly, is used to cool the lead-bismuth alloy fluid; The storage tank is connected to the liquid injection switch valve via a pipeline; Temperature acquisition components are evenly distributed on the inner surface of the housing and are electrically connected to an external acquisition device via connecting wires. An insulation layer is applied to the outer surfaces of the housing, the electric heating component, and the cooling component.

2. The experimental apparatus for natural convection of lead-bismuth alloy fluid according to claim 1, characterized in that, The housing has a covering air chamber inside, which is located at the top of the convection chamber and is connected to the convection chamber.

3. The experimental apparatus for natural convection of lead-bismuth alloy fluid according to claim 2, characterized in that, It also includes: An expansion valve is connected to the covered air chamber via a pipe; An expansion tank is connected to the end of the expansion valve away from the housing via a pipe.

4. The experimental apparatus for natural convection of lead-bismuth alloy fluid according to claim 1, characterized in that, The electric heating assembly includes: An electric heater is disposed on the outer surface of the housing; A switching power supply is connected to the electric heater via a connecting wire.

5. The experimental apparatus for natural convection of lead-bismuth alloy fluid according to claim 4, characterized in that, The electric heater is an electric heating belt, an electric heating element, or an electric heating plate.

6. The experimental apparatus for natural convection of lead-bismuth alloy fluid according to claim 1, characterized in that, The cooling assembly includes: A condenser coil is located on the side of the housing away from the electric heating assembly; The heat exchanger is connected to the outlet of the condenser coil via a pipe; A circulating pump is connected to the outlet of the heat exchanger via a pipeline; the outlet of the circulating pump is connected to the inlet of the condensing coil.

7. The experimental apparatus for natural convection of lead-bismuth alloy fluid according to claim 6, characterized in that, A flow meter is installed at the outlet of the heat exchanger.

8. The experimental apparatus for natural convection of lead-bismuth alloy fluid according to claim 6, characterized in that, The condenser coil can be a single-layer condenser coil or a multi-layer condenser coil.

9. The experimental apparatus for natural convection of lead-bismuth alloy fluid according to claim 1, characterized in that, The temperature acquisition component includes: The first thermocouple assembly is disposed on the inner wall of the housing near the electric heating assembly; The second thermocouple assembly is disposed on the inner wall of the housing near the cooling assembly; Multiple third thermocouple groups are arranged laterally at intervals on the inner wall of the housing, which is perpendicular to the mounting wall of the electric heating assembly.

10. The experimental apparatus for natural convection of lead-bismuth alloy fluid according to claim 9, characterized in that, The first thermocouple group, the second thermocouple group, and the third thermocouple group each include multiple thermocouple sensors arranged vertically at intervals.

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