A heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element

Abstract

This application relates to the fields of reactor thermal-hydraulic and safety technology, specifically to a heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element. It includes a heated plate, an insulating base, a cover, a medium inlet, a medium outlet, and conductive components. The heated plate has a vacuum bubble-like section. The heated plate is connected to the insulating base, which contains an elastic sealing cavity filled with insulating powder. A temperature measuring hole is also provided on the insulating base. The cover has a flow groove and is connected to the insulating base. The medium inlet is connected to one end of a narrow slit channel; the medium outlet is connected to the other end of the narrow slit channel; two conductive components are respectively connected to both ends of the heated plate, and the vacuum bubble-like section is located between the two conductive components. This application can simulate the structural state, thermal boundary, and coolant flow channel geometry of a dispersed fuel element during bubbling, and can measure the flow heat transfer characteristics and vapor-liquid two-phase flow field near the vacuum bubble-like section.

Description

Technical Field

[0001] This application relates to the fields of reactor thermal-hydraulic and safety technology, specifically to a heat transfer simulation experimental device under the condition of foaming on the surface of a dispersed fuel element. Background Technology

[0002] Dispersed fuel elements exhibit bubbling during the heating process under high burnup conditions. Bubbling refers to the phenomenon where the fission gases generated by irradiation concentrate locally, causing plastic deformation of the fuel and resulting in bubbly protrusions on the element surface. Bubbling in dispersed fuel elements distorts the heat flow distribution and coolant channel geometry. These adverse conditions lead to completely different thermo-hydraulic characteristics within the channels compared to normal conditions, representing a key issue that needs to be addressed in the safety analysis of dispersed fuel elements.

[0003] Current research on the flow and heat transfer characteristics within narrow slit channels under bubbling conditions is limited, and most studies employ three-dimensional numerical simulations. The few similar experiments conducted are primarily for channel blockage conditions. Therefore, it is necessary to design an experimental setup for simulating the heat transfer characteristics of dispersed fuel element surfaces under bubbling conditions. This setup would facilitate the acquisition of flow and heat transfer characteristics near bubbling, including boiling two-phase heat transfer characteristics, providing technical support for the precise formulation of thermal-hydraulic design and safety criteria for dispersed fuel elements. Summary of the Invention

[0004] This application addresses the problems in the background art by providing a heat transfer simulation experimental device under the condition of foaming on the surface of a dispersed fuel element.

[0005] This application is achieved through the following technical solution:

[0006] An experimental apparatus for simulating heat transfer under conditions of surface bubbling in a dispersed fuel element includes:

[0007] A heat-conducting plate, wherein one surface of the heat-conducting plate has a vacuum bubble-like portion;

[0008] The heat-insulating base has a heating plate connected to the working surface of the heat-insulating base. The heat-insulating base has an elastic sealing cavity filled with heat-insulating powder. The heat-insulating base also has a temperature measuring hole corresponding to the position of the vacuum bubble section, so that the thermocouple can pierce the elastic sealing cavity through the temperature measuring hole and contact the heating plate.

[0009] The cover has a flow groove, and the cover is connected to the heat insulation base so that the heat insulation base seals the flow groove to form a narrow slit channel, and the heat receiving plate is located in the narrow slit channel;

[0010] A media inlet device, wherein the media inlet device is connected to one end of the narrow slit channel;

[0011] A media outlet component, which is connected to the other end of the narrow slit channel;

[0012] The conductive elements are respectively connected to the two ends of the heated plate, and the vacuum bubble section is located between the two conductive elements.

[0013] In some alternative embodiments, the cover is sealed to the heat-insulating base by a static sealing ring, wherein the static sealing ring is arranged around the flow groove.

[0014] In some alternative embodiments, a mounting platform is constructed on the working surface of the heat-insulating base, the heat-receiving plate is connected to the mounting platform, and one of the plate surfaces is flush with the working surface.

[0015] In some alternative embodiments, the heated plate is connected to the inner wall of the mounting platform by filling with sealant.

[0016] In some optional embodiments, the light transmittance of the cover is configured to be not less than 98%.

[0017] In some alternative embodiments, the cover is configured as optical quartz glass.

[0018] In some alternative embodiments, the thermally insulating base is configured as an insulator.

[0019] In some alternative embodiments, the heat-insulating base is configured as a resin body.

[0020] In some alternative embodiments, the conductive element is connected to the heated plate by silver soldering.

[0021] In some optional embodiments, the number of temperature measuring holes is configured to be multiple, and the distance between the multiple temperature measuring holes and the vacuum bubble portion is no more than 10 mm from the normal viewing angle of the heated plate surface.

[0022] In some alternative embodiments, at least one temperature sensing hole corresponds to the center position of the vacuum bubble portion.

[0023] In some optional embodiments, the heat-insulating base has a detachable positioning plate, the positioning plate including a lower baffle and an upper baffle embedded in the lower baffle, the upper baffle and the lower baffle forming an installation cavity suitable for accommodating the elastic sealing cavity, and the temperature measuring hole is located on the positioning plate; wherein, the positioning plate corresponds to the position of the vacuum bubble portion.

[0024] In some alternative embodiments, the heat transfer simulation experimental apparatus under bubbling conditions on the surface of the dispersed fuel element further includes a pressure measuring pipe that communicates with the narrow slit channel.

[0025] In some optional embodiments, the media inlet and / or media outlet are configured with a temperature sensing connector.

[0026] In some optional embodiments, the heat transfer simulation experimental device under the condition of foaming on the surface of the dispersed fuel element further includes a first pressure block and a second pressure block arranged at intervals, the first pressure block being connected to the second pressure block, wherein the first pressure block abuts against the base and the second pressure block abuts against the cover.

[0027] In some alternative embodiments, the heating plate includes:

[0028] A foaming plate, wherein the foaming plate is formed with grooves by a casting process;

[0029] A heating plate, wherein the heating plate and the bubbling plate are arranged in parallel and spaced apart;

[0030] An insulating layer is located between the foaming plate and the heating plate. The insulating layer is connected to the heating plate and is connected to the foaming plate by vacuum diffusion welding to form a vacuum bubble-like part with the groove on the foaming plate.

[0031] Compared with the prior art, this application has the following advantages and beneficial effects:

[0032] 1. This application provides a heat transfer simulation experimental device under the bubbling condition of a dispersed fuel element surface. The vacuum bubble section on the heated plate can simulate the structural state of the dispersed fuel element under bubbling. A narrow slit channel is formed by connecting the cover and the insulating base. The medium flows in the narrow slit channel using the medium inlet and outlet components. The heated plate is heated using the conductive component. At the same time, the heated plate diffuses heat to the narrow slit channel on one side under the insulating effect of the insulating base. The same heating and heat transfer conditions as when the dispersed fuel element is bubbling are obtained. The same coolant thermal boundary as when the dispersed fuel element is bubbling is provided, thereby achieving accurate simulation of the heating boundary and flow channel geometric boundary of the dispersed fuel element. Finally, the temperature of the heated plate can be directly measured by setting the temperature measuring hole.

[0033] 2. The heat transfer simulation experimental device under the condition of foaming on the surface of the diffuse fuel element provided in this application has an external temperature measuring element, which does not need to be continuously in a high-temperature working environment, which is conducive to improving the accuracy of temperature measurement. After the measurement is completed, the elastic sealing cavity fills the hole formed by the puncture of the temperature measuring element by its own elasticity to compress the heat insulation powder inside, thereby avoiding heat loss from the heated plate and ensuring that the thermal boundary of the coolant in the narrow channel is basically consistent with the actual working condition. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the exemplary embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0035] Figure 1 A schematic diagram of the heat transfer simulation experimental device under surface bubbling conditions of a dispersed fuel element provided in this application embodiment;

[0036] Figure 2 for Figure 1 Schematic diagram of the cross-sectional structure at point AA;

[0037] Figure 3 This is a partial structural diagram of the connection between the positioning plate and the first pressure-bearing block provided in an embodiment of this application;

[0038] Figure 4 This is a schematic diagram of the cross-sectional structure of the positioning plate provided in an embodiment of this application;

[0039] Figure 5 This is a schematic diagram of the heat-receiving plate structure provided in an embodiment of this application.

[0040] The attached diagram shows the markings and corresponding component names:

[0041] 1-Media inlet component, 2-Media outlet component, 3-Second pressure-bearing block, 4-Cover body, 5-Heating plate, 51-Bubble plate, 52-Heating plate, 53-Insulation layer, 6-Insulating base, 7-Narrow slit channel, 8-Conductive component, 9-First pressure-bearing block, 10-Temperature measuring hole, 11-Positioning plate, 111-Upper baffle, 112-Lower baffle, 113-Elastic sealing cavity, 114-Insulating powder, 12-Temperature measuring pipe, 13-Pressure measuring pipe. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this application are only for explaining this application and are not intended to limit this application.

[0043] This application provides an experimental apparatus for simulating heat transfer under conditions of surface bubbling in a dispersed fuel element, which can be referred to in conjunction with this application. Figure 1 , Figure 2 and Figure 4 The heat transfer simulation experimental device under the surface bubbling condition of the diffuse fuel element includes a heating plate 5, an insulating base 6, a cover 4, a medium inlet 1, a medium outlet 2, and a conductive component 8.

[0044] The heating plate 5 can be configured as an electrically conductive material plate. When electrically conductive, the heating plate 5 generates heat by doing work through current to simulate the heat release of a diffused fuel element. For example, the heating plate 5 can be configured as a material such as copper, aluminum, iron, nickel-chromium alloy, silicon, germanium, silicon carbide, gallium arsenide, carbon fiber, graphite, carbon nanotubes, ceramic fiber, carbon-based composite plate, etc. One surface of the heating plate 5 has a vacuum bubble section, which is manifested as a hollow protrusion on one surface of the heating plate 5. The vacuum bubble section can be formed by casting or by connecting two components together. The hollow protrusion contains a vacuum cavity.

[0045] The heating plate 5 is connected to the working surface of the heat-insulating base 6. The specific shape of the heat-insulating base 6 is not limited; it can be constructed as a cuboid, triangular prism, square prism, polygonal prism, sphere, or other irregular shape. The working surface of the heat-insulating base 6 can be a plane to facilitate the connection of other components. For example, in this embodiment, when the heating plate 5 heats up, its surface has a large heat diffusion area. The surface of the heating plate 5 can be in contact with the working surface of the heat-insulating base 6 to reduce heat dissipation and achieve unilateral heat diffusion of the heating plate 5. The vacuum bubble portion is located on the surface of the heating plate 5 away from the heat-insulating base 6. The working surface can be... The working surface can be obtained through machining, or it can be a plane inherent in the insulation base 6 itself. For example, when the insulation base 6 is constructed as a sphere, a working surface can be obtained on the insulation base 6 through machining methods such as turning, milling, and planing. For example, when the insulation base 6 is constructed as a cuboid, one side of the insulation base 6 can serve as the working surface. In actual experimental operations, the insulation base 6 usually needs to be fixed or clamped by other components, so the insulation base 6 can be constructed as a cuboid to facilitate necessary operations by the experimental personnel. In this case, the outline shape of the working surface is a rectangle. Of course, the specific shape of the working surface is not limited, that is, it can be used in other implementations. In the example, even if the insulating base 6 is constructed as a cuboid, a working surface with a triangular, pentagonal, hexagonal, star-shaped, or other irregular shape can be machined on one side of the insulating base 6. An elastic sealing cavity 113 is provided inside the insulating base 6. The elastic sealing cavity 113 can be made of rubber or silicone material and is filled with insulating powder 114. In practice, the insulating powder 114 can be configured as glass fiber powder. The insulating base 6 also has a temperature measuring hole 10 corresponding to the position of the vacuum bubble section. The thermocouple can pierce the elastic sealing cavity 113 through the temperature measuring hole 10. After contacting the heating plate 5, in actual implementation, a puncture hole with a diameter much smaller than that of the thermocouple can be opened on the elastic sealing cavity 113. Due to the material properties of the elastic sealing cavity 113 itself, after the thermocouple punctures the elastic sealing cavity 113, the hole wall of the puncture hole can be tightly attached to the thermocouple due to its own elastic deformation. At the same time, the heat insulation powder 114 in the elastic sealing cavity 113 becomes more compact under the pressure of the thermocouple, which means that the heat insulation powder 114 can also be tightly attached to the thermocouple. Of course, as the heat insulation powder 114 is compressed, the cavity wall of the elastic sealing cavity 113 will also undergo a certain elastic deformation due to the pressure of the heat insulation powder 114.After temperature measurement, the thermocouple is removed. The puncture hole in the elastic sealing cavity 113 returns to its original shape under the action of elastic deformation. The heat insulation powder 114 inside is compressed under the elastic action of the cavity wall of the elastic sealing cavity 113, causing the heat insulation powder 114 to flow into the hole formed by the thermocouple. This means that under the elastic action of the elastic sealing cavity 113, the heat insulation powder 114 can self-fill, thereby providing better heat insulation for the heated plate 5, preventing heat loss from the heated plate 5, and ensuring that the thermal boundary of the coolant in the narrow slit channel 7 is basically consistent with the actual working conditions. The extension direction of the temperature measuring hole 10 is not limited, such as a straight line, a broken line, a curve, or any two or three of the above. In order to reduce the length of the temperature measuring hole 10 in its extending direction, the extending direction of the temperature measuring hole 10 can be a straight line. The extending direction of the temperature measuring hole 10 can be perpendicular to the surface of the heating plate 5 or form an angle. In practice, it is preferable to set the extending direction of the temperature measuring hole 10 to be perpendicular to the surface of the heating plate 5, thereby ensuring that the length of the temperature measuring hole 10 in the extending direction is short enough to facilitate temperature measurement of the heating plate 5 through the temperature measuring hole 10. The cross-sectional shape of the temperature measuring hole 10 is not limited, and can be triangular, rectangular, square, circular, heart-shaped, star-shaped, or other irregular shapes. In practice, the temperature measuring hole 10 can be set as a circular straight hole.

[0046] The cover 4 has a flow groove, and the cover 4 is connected to the heat insulation base 6 so that the heat insulation base 6 seals the flow groove to form a narrow slit channel 7. The heat receiving plate 5 is located in the narrow slit channel 7. That is, for the cover 4 and the heat receiving plate 5, the heat receiving plate 5 can be placed in the flow groove. The specific form of the flow groove is not limited. It can be a closed groove on the cover 4, that is, a groove with only one opening, or an open groove, that is, the flow groove can penetrate the cover 4 to form two or three openings. In actual implementation, the flow groove can be set as a closed groove. In this way, after the cover 4 is connected to the heat insulation base 6, the heat insulation base 6 can easily seal the flow groove through the working surface to form the narrow slit channel 7. Of course, in other embodiments, if the flow groove is set as an open groove, after the cover 4 is connected to the heat insulation base 6, other openings can be sealed individually or other openings can be sealed together with other components. The specific shape of the flow channel is not limited, such as triangle, rectangle, square, circle or other irregular shapes. Since a narrow channel 7 for medium flow is formed between the flow channel and the heat insulation base 6, it is preferred to set the flow channel as a channel shape with a certain length, such as a rectangular channel, a square channel, or a prism-shaped channel. Preferably, the flow channel is set as a rectangular channel or a square channel, which means that the outline shape of the flow channel is a square or a rectangle from the perspective of the length direction of the flow channel. When the flow channel is set as a rectangular channel or a square channel, its extension direction can be a straight line or a curve. In actual implementation, the extension direction of the flow channel can be set as a straight line to ensure that the medium has a stable flow state in the narrow channel 7. In other embodiments, the extension direction of the flow channel can also be set as a curve or a combination of curve and straight line as needed. When the flow channel is set as a rectangular or square channel, the heating plate 5 can be set as a rectangular plate. That is to say, the thickness of the heating plate 5 is uniform except for the vacuum bubble part. At this time, the overall shape of the narrow channel 7 formed by the flow channel and the insulating base 6 is a cuboid. This is conducive to the centering of the heating plate 5 in the narrow channel 7, ensuring that the heat can be evenly diffused in the narrow channel 7, and ensuring that the medium is heated evenly in the flow direction.

[0047] The medium inlet 1 is connected to one end of the narrow slit channel 7. When the flow channel is a closed channel, the medium inlet 1 can penetrate the insulating base 6 to connect with the narrow slit channel 7, and the medium inlet 1 is sealed to the insulating base 6. When the flow channel is an open channel, the medium inlet 1 can be directly sealed to the unsealed opening in the flow channel. The medium inlet 1 is typically used for injecting coolant.

[0048] The medium outlet 2 is connected to the other end of the narrow slit channel 7; when the flow channel is set as a closed channel, the medium outlet 2 can pass through the heat-insulating base 6 to connect with the narrow slit channel 7, and the medium outlet 2 is sealed to the heat-insulating base 6; when the flow channel is set as an open channel, the medium outlet 2 can be directly sealed to the unclosed opening in the flow channel.

[0049] Two conductive elements 8 are respectively connected to the two ends of the heating plate 5. The conductive elements 8 can be configured as copper busbars, aluminum busbars, stainless steel busbars, zinc alloy busbars, copper alloy busbars, plastic conductive busbars, etc. In actual implementation, the two conductive elements 8 can be the same or different. Preferably, the two conductive elements 8 can be configured as copper busbars. Copper busbars have excellent conductivity, can reduce heat loss, and have good mechanical strength, corrosion resistance, high flexibility and good welding performance. The vacuum bubble part is located between the two conductive elements 8. That is, when the heating plate 5 is set as a rectangular plate, the two conductive elements 8 can be connected to the two ends of the length direction of the heating plate 5, and the vacuum bubble part can be located in the middle position of the two conductive elements 8 in the length direction of the heating plate 5. Of course, in other embodiments, the vacuum bubble part can also be located at other positions between the two conductive elements 8.

[0050] The heat transfer simulation experimental device for surface bubbling of a dispersed fuel element provided in this application embodiment can simulate the structural state of a dispersed fuel element under bubbling conditions by using a vacuum bubble-shaped section on the heated plate 5. After connecting the two conductive parts 8 to the power supply and the medium inlet 1 and medium outlet 2 to the medium circulation system, the heated plate 5 can be electrically conductive to generate heat, thereby increasing the temperature. Due to the insulation effect of the insulating base 6, most of the heat from the heated plate 5 is dissipated to the narrow slit channel 7 on one side to heat the medium in the narrow slit channel 7, thereby simulating the working state of the fluid in the dispersed fuel element. The experimenter can measure the temperature field of the medium near the vacuum bubble-shaped section and directly measure the temperature of the heated plate 5 at the corresponding position of the vacuum bubble-shaped section through the temperature measuring hole 10. Combined with parameters such as the medium pressure and medium flow rate in the medium circulation system, the flow heat transfer characteristics near the vacuum bubble-shaped section can be obtained. These flow heat transfer characteristics can provide technical support for the precise formulation of thermal-hydraulic design and safety criteria for dispersed fuel elements.

[0051] The heat transfer simulation experimental device under the bubbling condition on the surface of the dispersed fuel element provided in this application realizes the external placement of the temperature measuring element (i.e., thermocouple). Compared with the existing concept of internal placement of the temperature measuring element, the temperature measuring element in this application does not need to be in a high-temperature working environment for a long time, which is conducive to ensuring the service life and measurement accuracy of the temperature measuring element. In addition, this application can easily use temperature measuring elements of different accuracies to measure the heated plate 5 to meet the diverse test requirements in the test process, and its applicability is relatively good. After the measurement is completed, the elastic sealing cavity 113 can return to its original shape under its own elastic action, and under the elastic action of the elastic sealing cavity 113, the heat insulation powder 114 inside completes self-filling at the same time, which can prevent heat loss from the heated plate 5 in non-measurement environment, ensure that the thermal boundary of the coolant in the narrow slit channel 7 is basically consistent with the actual working condition, and thus ensure the accuracy of the test results.

[0052] Compared with existing three-dimensional numerical simulation methods, the heat transfer simulation experimental device under the bubbling condition on the surface of the dispersed fuel element provided in this application embodiment can perform direct measurement, with relatively less computation, more convenient implementation, more intuitive and easier-to-obtain data, and the measurement results have considerable reliability.

[0053] There are various sealing connection methods between the cover 4 and the heat insulation base 6, such as adhesive sealing, welding sealing, magnetic sealing, and threaded sealing. Considering the overall maintainability of the device, in some optional embodiments, the cover 4 is sealed to the heat insulation base 6 by a static sealing ring. The static sealing ring can be configured as a rubber sealing ring, a metal sealing ring, a polytetrafluoroethylene sealing ring, a graphite sealing ring, etc. In actual implementation, a suitable static sealing ring can be selected according to the thermal conductivity of the cover 4. For example, if the thermal conductivity of the cover 4 is low, a static sealing ring with general heat resistance, such as a rubber sealing ring, can be selected. If the thermal conductivity of the cover 4 is high, a static sealing ring with higher heat resistance, such as a graphite sealing ring, can be selected. In actual implementation, it is generally desirable for the thermal conductivity of the cover 4 to be low. To prevent excessive heat loss from the narrow slit channel 7, ensuring that the temperature of the cover 4 does not become too high during operation, the static sealing ring can be configured as a low-cost static sealing ring such as a rubber sealing ring. The static sealing ring is arranged around the flow groove, and its shape is not limited. For example, it can be rectangular, circular, triangular, or rhomboid, etc. The design can be adapted to the opening of the flow groove to avoid creating a large narrow slit space after the cover 4 is connected to the heat-insulating base 6. For example, when the flow groove is rectangular, its opening is rectangular, and the static sealing ring can be configured as rectangular. Of course, in other embodiments, depending on the needs, such as different installation conditions or different processing precision, the shape of the static sealing ring can also be other irregular shapes.

[0054] After the heated plate 5 is connected to the insulating base 6, it is desirable for the heated plate 5 to have a single heat dissipation area to facilitate control of its heat dissipation direction. For example, one surface of the heated plate 5 can be positioned within the narrow slit channel 7, while the other surfaces are relatively isolated from the narrow slit channel 7. This allows the heat from the heated plate 5 to be primarily dissipated from one surface into the narrow slit channel 7. Therefore, in some optional embodiments, a mounting platform is constructed on the working surface of the insulating base 6, and the heated plate 5 is connected to the mounting platform with one surface flush with the working surface. This ensures that the other surfaces of the heated plate 5 are in contact with the insulating base 6, reducing the heat dissipation area of ​​the heated plate 5 within the narrow slit channel 7. In other words, the surface where the vacuum bubble exists serves as the heat dissipation surface, thus ensuring a consistent heat dissipation direction for the heated plate 5. This facilitates the analysis of the heat dissipation characteristics of the heated plate 5, helps predict the heat distribution within the narrow slit channel 7, and provides a theoretical basis for experimental results.

[0055] The connection between the heating plate 5 and the insulating base 6 is not limited, as long as the heating plate 5 can fit surface-to-surface with the insulating base 6 to achieve good insulation. However, due to the influence of processing precision, there may be a certain gap between the surface-to-surface fit of the heating plate 5 and the insulating base 6. If the gap is a slit communicating with the narrow channel 7, it may affect the temperature of the local medium in the narrow channel 7. This will be detrimental to the detailed study of the heat transfer characteristics of the local medium in the narrow channel 7. Therefore, in some optional embodiments, the heating plate 5 and the inner wall of the mounting platform are connected by filling with sealant. The sealant can be a heat-resistant sealant to prevent deformation due to excessive temperature, which would affect the sealing effect between the heating plate 5 and the sealant. It can be configured as silicone sealant, polyurethane sealant, fluororubber sealant, polytetrafluoroethylene sealant, high-temperature silicon compound sealant, etc.

[0056] The cover 4 can be made of either transparent or opaque material, both of which enable the measurement of parameters such as the temperature of the medium within the narrow slit channel 7. Of course, if the cover 4 has a certain degree of transparency, it can achieve visual measurement of the velocity field and two-phase flow within the medium of the narrow slit channel 7. Therefore, in some optional embodiments, the light transmittance of the cover 4 is configured to be not less than 98%. Preferably, the cover 4 can be configured as optical quartz glass. Optical quartz glass has good light transmittance and low thermal conductivity, which can reduce heat loss from the medium in the narrow slit channel 7.

[0057] During the electrical conduction of the heated plate 5, it is desirable for the current to have good effective power, meaning that the current primarily performs work on the heated plate 5. Therefore, in some optional embodiments, the insulating base 6 is configured as an insulator, thereby greatly reducing power loss and ensuring electrical safety during the experiment. Preferably, the insulating base 6 can be configured as a resin body. In other embodiments, the material used for the insulating base 6 can also be configured as ceramic material, fiber-reinforced ceramic matrix material, graphene material, etc., as needed. When the insulating base 6 is configured as an insulator, a ceramic tube can be inserted into the temperature measuring hole 10 on the insulating base 6 to achieve the insulation function.

[0058] The conductive component 8 is typically connected to other devices requiring conductivity by welding. In this embodiment, the heating plate 5 operates at a relatively high temperature; therefore, the weld between the conductive component 8 and the heating plate 5 must possess certain heat resistance. Consequently, in some optional embodiments, the conductive component 8 is connected to the heating plate 5 via silver brazing. Silver has a lower coefficient of thermal expansion than copper, meaning that the thermal stress generated at the silver brazing connection point is relatively small during temperature changes, helping to reduce the risk of loosening. Furthermore, silver has excellent corrosion resistance, especially at high temperatures, which helps extend the service life of the welded area and ensures the conductivity of the conductive component 8 and the heating plate 5.

[0059] In order to facilitate obtaining the temperature field characteristics of the vacuum bubble section and its surroundings, in some optional embodiments, the number of temperature measuring holes 10 is configured to be multiple. From the normal view of the heated plate 5, the distance between the multiple temperature measuring holes 10 and the vacuum bubble section is no more than 10 mm. This includes temperature measuring holes 10 corresponding to the edge of the vacuum bubble section, and at least one temperature measuring hole 10 corresponding to the center position of the bubble section at a distance of 10 mm from the vacuum bubble section in the medium flow direction.

[0060] For different heating plates 5, the position and size of the vacuum bubble-like portions vary. In some optional embodiments, the insulation base 6 has a detachable positioning plate 11. The positioning plate 11 can be configured as a polytetrafluoroethylene (PTFE) plate. Specifically, the positioning plate 11 may include a lower baffle 112 and an upper baffle 111. The upper baffle 111 is embedded in the lower baffle 112. The lower baffle 112 is generally a multi-diameter shaft, with a mating groove in its small-diameter section. The upper baffle 111 is similar in shape to a circular cover, and its shape is adapted to fit the mating groove so that it can be embedded within it. The open end of the upper baffle 111 is located inside the mating groove, while the closed end is located outside. The space within the upper baffle 111 serves as an installation cavity. This installation cavity is adapted to the shape of the elastic sealing cavity 113 so that the outer wall of the elastic sealing cavity 113 can fit against the cavity wall of the installation cavity. The positioning plate 11 has... The presence of temperature measuring holes 10 indicates that some of the multiple temperature measuring holes 10 are distributed on the positioning plate 11. Specifically, coaxial holes are formed on the upper baffle 111 and the lower baffle 112, with each pair of coaxial holes on the upper baffle 111 and the lower baffle 112 serving as temperature measuring holes 10. The distribution of temperature measuring holes 10 on different positioning plates 11 varies. Depending on the position and size of the vacuum bubble, the size and position of the temperature measuring holes 10 on the positioning plate 11 are different. This means that by replacing different positioning plates 11 according to the position and size of the vacuum bubble, it is convenient for the thermocouple to measure the heated plate 5. The positioning plate 11 corresponds to the position of the vacuum bubble. In actual implementation, the specific shape of the positioning plate 11 is not limited. It can be constructed as a cylinder to accommodate the detection range around the vacuum bubble. In other embodiments, the positioning plate 11 can also be constructed as a prism, a hemisphere, or other irregular shapes. The positioning plate 11 can also be removed, at which point the bubbling position on the heated plate 5 is exposed, making it easier to measure the wall temperature field using an infrared thermometer.

[0061] See also Figure 3 It is understandable that the projected area of ​​the positioning plate 11 in the normal direction of the heated plate 5 may be much larger than that of the vacuum bubble part. At this time, temperature measuring holes 10 can also be provided on the positioning plate 11 at the corresponding positions around the vacuum bubble part. These temperature measuring holes 10 correspond one-to-one with the temperature measuring holes 10 on the heat insulation base 6 and are arranged coaxially.

[0062] In some optional embodiments, the heat transfer simulation experimental device under the bubbling condition of the diffuse fuel element surface further includes a pressure measuring pipe 13, which is connected to the narrow slit channel 7. In actual implementation, the pressure measuring pipe 13 passes through the insulating base 6 and connects to the narrow slit channel 7. The number of pressure measuring pipes 13 can be configured as two. In the direction of medium flow, the two pressure measuring pipes 13 are located on both sides of the vacuum bubbling section. Preferably, the two pressure measuring pipes 13 are arranged close to the medium inlet 1 and the medium outlet 2, respectively. By setting the pressure measuring pipes 13, the medium pressure in the narrow slit channel 7 can be measured, and the pressure change characteristics of the medium on both sides of the vacuum bubbling section can be obtained, which is beneficial for carrying out research on the influence of the vacuum bubbling section on the medium pressure under heat generation conditions.

[0063] In some optional embodiments, the medium inlet 1 and / or the medium outlet 2 are equipped with temperature measuring pipes 12. In actual implementation, temperature measuring pipes 12 can be configured on both the medium inlet 1 and the medium outlet 2. The temperature measuring pipes 12 facilitate the measurement / monitoring of the medium temperature before it enters the narrow slit channel 7 and after it flows out of the narrow slit channel 7, which can bring convenience to the measurement process and make it easier to obtain the dynamic change characteristics of the medium temperature under long-term operation.

[0064] In some optional embodiments, the heat transfer simulation experimental device under the condition of foaming on the surface of the diffuse fuel element further includes a first pressure block 9 and a second pressure block 3 arranged at intervals, wherein the first pressure block 9 and the second pressure block 3 are connected, wherein the first pressure block 9 abuts against the base and the second pressure block 3 abuts against the cover 4.

[0065] In this embodiment, the first pressure block 9 and the second pressure block 3 can press the cover 4 and the heat insulation base 6 together, thereby ensuring the stability of the sealing performance between the cover 4 and the heat insulation base 6. Both the first pressure block 9 and the second pressure block 3 can be constructed as cuboids. The first pressure block 9 can cover the heat insulation base 6, and the second pressure block 3 can cover the cover 4. The first pressure block 9 and the second pressure block 3 can be fastened together with bolts. The temperature measuring pipe 12, the conductive component 8, the pressure measuring pipe 13, the medium inlet component 1, the medium outlet component 2, and the positioning plate 11 can all sequentially pass through the first pressure block 9 and the heat insulation base 6 to communicate with the narrow slit channel 7 or connect with the heat-receiving plate 5. When the cover 4 has a light transmittance of not less than 98%, an observation window can be opened on the second pressure block 3. In the normal direction of the surface of the heat-receiving plate 5, the vacuum bubble portion is located within the area encompassed by the observation window.

[0066] Among them, such as Figure 3As shown, when the first pressure block 9 and the second pressure block 3 are set, the positioning plate 11 can be connected to the first pressure block 9 by bolts. Therefore, it is not necessary to set a connection structure corresponding to the positioning plate 11 on the heat insulation base 6. When installing the positioning plate 11, it is only necessary to perform relative positioning of the temperature measuring hole 10 and the vacuum bubble part. The heat insulation base 6 does not participate in connecting the positioning plate, and the risk of structural damage to the heat insulation base 6 is greatly reduced, thereby ensuring that it has long-term stable heat insulation performance and / or insulation performance.

[0067] In some alternative embodiments, see [reference]. Figure 5 The heating plate includes a bubbling plate 51, a heating plate 52, and an insulating layer 53. The bubbling plate 51 has grooves formed by a casting process. The heating plate 52 is arranged in parallel with the bubbling plate 51 at intervals. The insulating layer 53 is located between the bubbling plate 51 and the heating plate 52. The insulating layer 53 is connected to the heating plate 52. The insulating layer 53 is connected to the bubbling plate 51 by vacuum diffusion welding to form a vacuum bubble-like part with the grooves on the bubbling plate 51.

[0068] When the heating plate provided in this application is used in an experimental apparatus for simulating the heat transfer characteristics under bubbling conditions on the surface of a dispersed fuel element, since the heating plate 52 relies on electricity to generate heat to simulate the heating of the dispersed fuel element, the current only passes through the heating plate 52 and not through the bubbling plate 51 through the setting of the insulating layer 53, thus truly simulating the heat source distribution in the prototype fuel element. This avoids the situation where the self-heating of the bubbling plate 51 affects the temperature field near the vacuum bubbling part, that is, it reduces the influencing factors of the temperature field near the vacuum bubbling part, which is beneficial to subsequent theoretical analysis and ensures the accuracy and reliability of the experimental results. Furthermore, the insulating layer 53 is connected to the bubbling plate 51 by vacuum diffusion welding, and the connection part has high temperature resistance, which is suitable for the bubbling temperature environment on the surface of a dispersed fuel element.

[0069] In actual implementation, the bubbling plate 51 is configured as an Inconel 625 plate, so that the thermal conductivity of the bubbling plate 51 is similar to that of the zirconium alloy cladding in the dispersed fuel element, and the thickness of the bubbling plate 51 is configured to be no more than 1 / 10 of the thickness of the heating plate 52; the conductive portion of the heating plate 52 is configured as an S32168 plate to ensure good resistance to intergranular corrosion and high-temperature strength, wherein the entire heating plate 52 can be configured as an S32168 plate; the insulating layer 53 can be formed by applying an aluminum nitride ceramic coating to the surface of the heating plate 52 using a PVD process. The thickness of the insulating layer 53 is 30-50 μm to ensure that it does not exceed 1 / 10 of the thickness of the blister plate 51, thereby achieving effective insulation under the operating condition of a maximum voltage of 50V in the experiment. The resistivity of the blister plate is much higher than that of the heating plate. With this setting, if the insulating layer 53 cracks during the diffusion welding process or during use, the heat generated by the blister plate 51 will not exceed 5% of the total heat generated by electrical conduction. The heat generated by the blister plate 51 has an acceptable impact on the temperature field of the vacuum bubble section, giving the experimental device a certain ability to resist abnormalities, thereby ensuring the success rate of the experiment.

[0070] In summary, the heat transfer simulation experimental device under the bubbling condition on the surface of the dispersed fuel element provided in this application embodiment can simulate the interstitial thermal resistance of the bubbling region of the dispersed fuel element, the cooling boundary shape of the narrow slit channel 7, and its heat transfer conditions. It is beneficial for measuring experimental data such as the wall temperature near the vacuum bubble section, the fluid temperature field and velocity field in the narrow slit channel 7, and the visualization measurement of the boiling two-phase flow pattern in the narrow slit channel 7, thereby obtaining the flow heat transfer characteristics near the vacuum bubble section, and thus providing a reference for the study of the heat transfer characteristics of the actual dispersed fuel element under the bubble state.

[0071] The specific embodiments described above illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Although the description of this application is presented in conjunction with some embodiments, this does not mean that the features of this application are limited to this embodiment. On the contrary, the purpose of describing the application in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of this application. To provide a thorough understanding of this application, many specific details are included in the above description. This application may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this application, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0072] It should be noted that in this specification, similar reference numerals and letters in the above figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, and are only for the convenience of describing this application 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 on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this application, it should be noted that unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" 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 communication between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0073] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element, characterized in that, include: A heat-receiving plate (5) capable of electrical conduction, wherein one surface of the heat-receiving plate (5) has a vacuum bubble-like portion; The heat-insulating base (6) is connected to the working surface of the heat-insulating base (6). The heat-insulating base (6) is provided with an elastic sealing cavity (113). The elastic sealing cavity (113) is filled with heat-insulating powder (114). The heat-insulating base (6) is also provided with a temperature measuring hole (10) corresponding to the position of the vacuum bubble part, so that the thermocouple can pierce the elastic sealing cavity (113) through the temperature measuring hole (10) and contact the heat-insulating plate (5). Cover (4), the cover (4) has a flow groove, the cover (4) is connected to the heat insulation base (6) so that the heat insulation base (6) seals the flow groove to form a narrow slit channel (7), and the heat receiving plate (5) is located in the narrow slit channel (7); Medium inlet (1), the medium inlet (1) is connected to one end of the narrow slit channel (7); Medium outlet (2), the medium outlet (2) is connected to the other end of the narrow slit channel (7); The conductive element (8) is connected to both ends of the heating plate (5) respectively, and the vacuum bubble part is located between the two conductive elements (8); The heat-insulating base (6) has a detachable positioning plate (11), which includes a lower baffle (112) and an upper baffle (111) embedded in the lower baffle (112). An installation cavity suitable for accommodating the elastic sealing cavity (113) is formed between the upper baffle (111) and the lower baffle (112). The temperature measuring hole (10) is located on the positioning plate (11). The positioning plate (11) corresponds to the position of the vacuum bubble part. The heat-receiving plate (5) includes: Bubble plate (51), the bubble plate (51) having grooves formed by a casting process; Heating plate (52), the heating plate (52) and the bubbling plate (51) are arranged in parallel and spaced apart; An insulating layer (53) is located between the bubbling plate (51) and the heating plate (52). The insulating layer (53) is connected to the heating plate (52). The insulating layer (53) and the bubbling plate (51) are connected by vacuum diffusion welding to form a vacuum bubble with the groove on the bubbling plate (51).

2. The heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element according to claim 1, characterized in that, The cover (4) is sealed to the heat insulation base (6) by a static sealing ring, wherein the static sealing ring is arranged around the flow groove.

3. The heat transfer simulation experimental apparatus under bubbling conditions on the surface of a dispersed fuel element according to claim 1 or 2, characterized in that, The working surface of the heat-insulating base (6) is provided with an installation platform, and the heating plate (5) is connected to the installation platform and one of the plate surfaces is flush with the working surface.

4. The heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element according to claim 3, characterized in that, The heated plate (5) is connected to the inner wall of the mounting platform by filling with sealant.

5. The heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element according to claim 1, characterized in that, The light transmittance of the cover (4) is configured to be not less than 98%.

6. The heat transfer simulation experimental apparatus under bubbling conditions on the surface of a dispersed fuel element according to claim 5, characterized in that, The cover (4) is configured as optical quartz glass.

7. The heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element according to claim 1, characterized in that, The heat-insulating base (6) is configured as an insulator.

8. The heat transfer simulation experimental apparatus under bubbling conditions on the surface of a dispersed fuel element according to claim 7, characterized in that, The heat-insulating base (6) is configured as a resin body.

9. The heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element according to claim 1, characterized in that, The conductive element (8) is connected to the heated plate (5) by silver brazing.

10. The heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element according to claim 1, characterized in that, The number of temperature measuring holes (10) is configured to be multiple, and the distance between the multiple temperature measuring holes (10) and the vacuum bubble part is no more than 10 mm from the normal viewing angle of the surface of the heated plate (5).

11. The heat transfer simulation experimental apparatus under bubbling conditions on the surface of a dispersed fuel element according to claim 10, characterized in that, At least one temperature measuring hole (10) corresponds to the center position of the vacuum bubble section.

12. The heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element according to claim 1, characterized in that, It also includes a pressure testing connector (13), which is connected to the narrow slit channel (7).

13. The heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element according to claim 1, characterized in that, The medium inlet (1) and / or medium outlet (2) are equipped with a temperature measuring tube (12).

14. The heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element according to claim 1, characterized in that, It also includes a first pressure block (9) and a second pressure block (3) arranged at intervals. The first pressure block (9) is connected to the second pressure block (3). The first pressure block (9) abuts against the base, and the second pressure block (3) abuts against the cover (4).

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