Heat transfer simulation experiment device under surface foaming condition of dispersion type fuel element

Abstract

The invention relates to the technical field of reactor thermal hydraulic power and safety, in particular to a heat transfer simulation experiment device under the surface foaming condition of a dispersion type fuel element. The device comprises a heated plate, a heat insulation base, a cover body, a medium leading-in piece, a medium leading-out piece and a conductive piece, the heated plate is provided with a vacuum bubble-shaped part; the heated plate is connected to the heat insulation base, an elastic sealing cavity is formed in the heat insulation base, the elastic sealing cavity is filled with heat insulation powder, and a temperature measuring hole is further formed in the heat insulation base; the cover body is provided with a circulation groove and connected with the heat insulation base. The medium leading-in piece is communicated with one end of the narrow slit channel; the medium leading-out piece is communicated with the other end of the narrow slit channel; the two conductive pieces are connected to the two ends of the heated plate respectively, and the vacuum bubble-shaped part is located between the two conductive pieces. According to the application, the structural state, thermal boundary and coolant flow channel geometric condition simulation of the dispersion type fuel element during bubbling can be realized, and the measurement of flow heat transfer characteristics, vapor-liquid two-phase flow field and the like near a vacuum bubble part can be carried out.

Description

Technical Field

[0001] The present application relates to the field of reactor thermal hydraulics and safety technology, and in particular to a heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element. Background Art

[0002] Dispersed fuel elements will blister as they heat up at high burnup. Blistering refers to the phenomenon that fission gases generated by irradiation are concentrated locally, causing plastic deformation of the fuel and the appearance of bubble-like protrusions on the surface of the element. The blistering of dispersed fuel elements causes distortion of both the heat flow distribution and the geometry of the coolant channels. This harsh condition causes the thermal and hydraulic characteristics in the channels to be completely different from those under normal conditions, which is a key issue that needs to be addressed in the safety analysis of dispersed fuel elements.

[0003] At present, there are few studies on the flow and heat transfer characteristics in narrow channels under bubbling conditions, and most of them use three-dimensional numerical simulation methods. A small number of similar experiments are for channel blockage conditions. Therefore, it is necessary to design an experimental device for simulating the heat transfer characteristics under bubbling conditions on the surface of dispersed fuel elements, so as to obtain the flow and heat transfer characteristics near the bubbles, including the boiling two-phase heat transfer characteristics, and provide technical support for the precise formulation of thermal hydraulic design and safety criteria of dispersed fuel elements. Summary of the invention

[0004] In view of the problems in the background technology, the present application provides a heat transfer simulation experimental device under the condition of bubbling on the surface of a dispersed fuel element.

[0005] This application is implemented through the following technical solutions:

[0006] A heat transfer simulation experimental device under the condition of bubbling on the surface of a dispersed fuel element, comprising:

[0007] A heated plate capable of electrical conduction, wherein one surface of the heated plate has a vacuum bubble-like portion;

[0008] An insulating base, the heated plate is connected to the working surface of the insulating base, an elastic sealing cavity is arranged in the insulating base, the elastic sealing cavity is filled with thermal insulation powder, and a temperature measuring hole corresponding to the position of the vacuum bubble portion is also opened on the insulating base, so that the thermocouple can pierce the elastic sealing cavity through the temperature measuring hole and contact the heated plate;

[0009] A cover body, wherein the cover body has a flow slot, the cover body is connected to the heat-insulating base so that the heat-insulating base seals the flow slot to form a narrow slit channel, and the heated plate is located in the narrow slit channel;

[0010] A medium introduction member, the medium introduction member being in communication with one end of the narrow slit channel;

[0011] A medium outlet member, the medium outlet member being in communication with the other end of the narrow slit channel;

[0012] Conductive members, two of which are connected to two ends of the heated plate respectively, and the vacuum bubble portion is located between the two conductive members.

[0013] In some optional embodiments, the cover body is sealed to the insulation base via a static sealing ring, wherein the static sealing ring is arranged around the flow groove.

[0014] In some optional embodiments, a mounting sink is constructed on the working surface of the thermal insulation base, the heated plate is connected to the mounting sink and one of the plate surfaces is flush with the working surface.

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

[0016] In some optional embodiments, the light transmittance of the cover body is configured to be no less than 98%.

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

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

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

[0020] In some optional embodiments, the conductive member is connected to the heated plate by silver brazing.

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

[0022] In some optional embodiments, at least one temperature measuring hole corresponds to a center position of the vacuum bubble.

[0023] In some optional embodiments, the insulating base has a removable positioning plate, which includes a lower baffle and an upper baffle embedded in the lower baffle, and an installation cavity suitable for accommodating the elastic sealing cavity is formed between the upper baffle and the lower baffle, 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 optional embodiments, the heat transfer simulation experimental device under bubbling conditions on the surface of the dispersed fuel element further includes a pressure measuring tube, which is connected to the narrow slit channel.

[0025] In some optional embodiments, the medium inlet and / or medium outlet is equipped with a temperature measuring tube.

[0026] In some optional embodiments, the heat transfer simulation experiment device under bubbling conditions on the surface of the dispersed fuel element also includes a first pressure block and a second pressure block arranged at intervals, and the first pressure block is connected to the second pressure block, wherein the first pressure block abuts against the base, and the second pressure block abuts against the cover body.

[0027] In some optional embodiments, the heated plate comprises:

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

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

[0030] An insulating layer is located between the blister plate and the heating plate, the insulating layer is connected to the heating plate, and the insulating layer and the blister plate are connected by vacuum diffusion welding to enclose a vacuum bubble portion with the groove on the blister plate.

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

[0032] 1. The present application provides a heat transfer simulation experimental device under the condition of bubbling on the surface of a dispersed fuel element. The vacuum bubble portion on the heated plate can simulate the structural state of the dispersed fuel element under bubbling, and a narrow slit channel is formed by connecting the cover body and the insulating base. The medium is flowed in the narrow slit channel by using a medium inlet and a medium outlet, and the heated plate is heated by using a conductive member. At the same time, the heated plate realizes unilateral diffusion of heat to the narrow slit channel under the insulating effect of the insulating base, and can obtain the same heating conditions and heat transfer conditions as those when the dispersed fuel element is bubbling, and provide a coolant thermal boundary consistent with that when the dispersed fuel element is bubbling, thereby realizing accurate simulation of the heating boundary of the dispersed fuel element and the geometric boundary of the flow channel. Finally, the temperature of the heated plate can be conveniently measured directly by setting the temperature measuring hole.

[0033] 2. The present application provides a heat transfer simulation experiment device under bubbling conditions on the surface of a diffuse fuel element. The temperature measuring element is external, and the temperature measuring element 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 compresses the insulating powder inside it through its own elasticity to fill the holes formed by the puncture of the temperature measuring element, 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 conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present application and should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0035] Figure 1 A schematic diagram of the structure of a heat transfer simulation experimental device under the condition of bubbling on the surface of a dispersed fuel element provided in an embodiment of the present application;

[0036] Figure 2 for Figure 1 Schematic diagram of the cross-section structure at AA in the middle;

[0037] Figure 3 A schematic diagram of a partial structure of the connection between the positioning plate and the first pressure-bearing block provided in an embodiment of the present application;

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

[0039] Figure 5 This is a schematic diagram of the heated plate structure provided in an embodiment of the present application.

[0040] Marks and corresponding parts names in the attached drawings:

[0041] 1-medium inlet, 2-medium outlet, 3-second pressure-bearing block, 4-cover, 5-heating plate, 51-foaming plate, 52-heating plate, 53-insulating layer, 6-insulating base, 7-narrow slit channel, 8-conductive member, 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 DESCRIPTION

[0042] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with examples and drawings. The illustrative implementation scheme of the present application and its description are only used to explain the present application and are not intended to limit the present application.

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

[0044] The heat receiving plate 5 can be configured as an electrically conductive material plate. When the heat receiving plate 5 is electrically conductive, the heat receiving plate is heated by the work done by the current to simulate the heat release of the diffuse fuel element. For example, the heat receiving plate 5 can be configured as copper, aluminum, iron, nickel-chromium alloy, silicon, germanium, silicon carbide, gallium arsenide, carbon fiber, graphite, carbon nanotubes, ceramic fibers, carbon-based composite plates, etc. One of the plate surfaces of the heat receiving plate 5 has a vacuum bubble portion, which is manifested as a hollow protrusion on one of the plate surfaces of the heat receiving plate 5. The vacuum bubble portion can be formed by casting or by connecting two components to each other, and the hollow protrusion has a vacuum cavity.

[0045] The heated plate 5 is connected to the working surface of the insulating base 6. The specific shape of the insulating base 6 is not limited. It can be constructed as a rectangular parallelepiped, a triangular prism, a quadrangular prism, a polygonal prism, a sphere or other special shapes; the working surface on the insulating base 6 can be a plane to facilitate the connection with other components, such as in the embodiment of the present application. When the heated plate 5 is heated, its plate surface has a large heat diffusion area. The plate surface of the heated plate 5 can be fitted with the working surface of the insulating base 6 to reduce heat dissipation and realize the unilateral diffusion of the heat of the heated plate 5, wherein the vacuum bubble portion is located on the heated plate 5 away from the plate surface of the insulating base 6; the working surface can be The insulating base 6 may be obtained by machining, or it may be a plane of the insulating base 6 itself. For example, when the insulating base 6 is constructed as a sphere, a working surface may be obtained on the insulating base 6 by machining methods such as turning, milling, and planing. For example, when the insulating base 6 is constructed as a rectangular parallelepiped, one of the side surfaces of the insulating base 6 may be used as the working surface. In actual experimental operations, the insulating base 6 usually needs to be fixed or clamped by other components, etc. Therefore, the insulating base 6 may be constructed as a rectangular parallelepiped to facilitate the experimenter to perform necessary operations. At this time, the contour shape of the working surface is a rectangle. Of course, the specific shape of the working surface may not be limited, that is, in other embodiments In the example, even if the insulating base 6 is constructed as a rectangular parallelepiped, a working surface with a contour shape of a triangle, a pentagon, a hexagon, a star or other special shapes can be processed on one of the side surfaces of the insulating base 6; an elastic sealing cavity 113 is provided in the insulating base 6, and the elastic sealing cavity 113 can be made of rubber or silicone material. The elastic sealing cavity 113 is filled with insulating powder 114. In actual implementation, the insulating powder 114 can be configured as glass fiber powder. The insulating base 6 is also provided with a temperature measuring hole 10 corresponding to the position of the vacuum bubble portion, and the thermocouple can pierce the elastic sealing cavity 113 through the temperature measuring hole 10. After that, it contacts with the heated 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 thermal insulation powder 114 in the elastic sealing cavity 113 is more compact under the pressure of the thermocouple, which means that the thermal insulation powder 114 can also be tightly attached to the thermocouple. Of course, since the thermal insulation powder 114 is compressed, the cavity wall of the elastic sealing cavity 113 will also be compressed by the thermal insulation powder 114 to undergo a certain elastic deformation;After the temperature measurement is completed, the thermocouple is taken out, and the puncture hole of the elastic sealing cavity 113 returns to its original shape under the action of elastic deformation, and the internal thermal insulation powder 114 is compressed under the elastic action of the cavity wall of the elastic sealing cavity 113, prompting the thermal insulation powder 114 to flow into the hole formed by the thermocouple, which means that under the elastic action of the elastic sealing cavity 113, the thermal insulation powder 114 can be self-filled, thereby providing better thermal insulation for the heated plate 5, avoiding heat loss of 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 condition. The extension direction of the temperature measuring hole 10 can be unlimited, such as a straight line, a broken line, a curve, or any two / three of the above. In order to reduce the length of the temperature measuring hole 10 in its extension direction, the extension direction of the temperature measuring hole 10 can be a straight line, wherein the extension direction of the temperature measuring hole 10 can be perpendicular to the plate surface of the heated plate 5 or form an angle. In actual implementation, it is preferred to set the extension direction of the temperature measuring hole 10 to be perpendicular to the plate surface of the heated plate 5, so as to ensure that the length of the temperature measuring hole 10 in the extension direction is short enough, so that the temperature measurement of the heated plate 5 can be conveniently performed in the temperature measuring hole 10; the cross-sectional shape of the temperature measuring hole 10 can be unlimited, such as a triangle, rectangle, square, circle, heart, star or other special shapes. In actual implementation, the temperature measuring hole 10 can be set as a circular straight hole. ;

[0046] The cover body 4 has a circulation groove, and the cover body 4 is connected to the insulating base 6 so that the insulating base 6 seals the circulation groove to form a narrow slit channel 7, and the heated plate 5 is located in the narrow slit channel 7, that is, for the cover body 4 and the heated plate 5, the heated plate 5 can be placed in the circulation groove; the specific form of the circulation groove is not limited, it can be a closed groove body on the cover body 4, that is, there is only one groove, or it can be an open groove body, that is, the circulation groove can penetrate the cover body 4 to form two / three grooves; in actual implementation, the circulation groove can be set as a closed groove body, so that after the cover body 4 is connected to the insulating base 6, the insulating base 6 can easily seal the circulation groove through the working surface to form a narrow slit channel 7. Of course, in other embodiments, if the circulation groove is set as an open groove body, then after the cover body 4 is connected to the insulating base 6, other grooves can be sealed separately or other grooves can be sealed and connected with other components. The specific shape of the circulation groove may not be limited, such as a triangle, rectangle, square, circle or other special shapes; since a narrow slit channel 7 for medium circulation is formed between the circulation groove and the insulating base 6, it is preferred to set the circulation groove to a trough shape with a certain length, such as a rectangular trough body, a square trough body, or a prismatic trough body. Preferably, the circulation groove is set to a rectangular trough body or a square trough body, which means that in the longitudinal direction of the circulation groove, the contour shape of the circulation groove is a square or a rectangle, wherein, when the circulation groove is set to a rectangular trough body or a square trough body, its extension direction may be a straight line or a curve. In actual implementation, the extension direction of the circulation groove may be set to a straight line to ensure that the medium has a stable flow state in the narrow slit channel 7. In other embodiments, the extension direction of the circulation groove may also be set to a curve or a combination of a curve and a straight line as needed. When the circulation groove is set as a rectangular groove body or a square groove body, the heated plate 5 can be set as a rectangular plate body, that is, the thickness of the heated plate 5 is uniform except for the position of the vacuum bubble portion. At this time, the overall shape of the narrow slit channel 7 formed by the circulation groove and the insulating base 6 is a rectangular parallelepiped, which is conducive to the centering of the heated plate 5 in the narrow slit channel 7, ensuring that the heat can be evenly diffused in the narrow slit channel 7, and ensuring that the medium is evenly heated in the flow direction.

[0047] The medium introduction member 1 is connected to one end of the narrow slit channel 7; when the flow slot is set as a closed slot body, the medium introduction member 1 can pass through the insulation base 6 to communicate with the narrow slit channel 7, and the medium introduction member 1 is sealed and connected to the insulation base 6; when the flow slot is set as an open slot body, the medium introduction member 1 can be directly sealed and connected to the unclosed slot in the flow slot. The medium introduction member 1 is usually used for injecting coolant.

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

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

[0050] The embodiment of the present application provides a heat transfer simulation experimental device under bubbling conditions on the surface of a dispersed fuel element. The vacuum bubble portion on the heated plate 5 can simulate the structural state of the dispersed fuel element under bubbling conditions. After connecting the two conductive parts 8 to the power supply and connecting the medium inlet 1 and the medium outlet 2 to the medium circulation system, the heated plate 5 can be electrically conducted to generate heat, thereby achieving a temperature increase. Due to the insulating effect of the insulating base 6, most of the heat of 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 portion, and directly measure the temperature of the heated plate 5 at the corresponding position of the vacuum bubble portion through the temperature measuring hole 10, and obtain the flow heat transfer characteristics near the vacuum bubble portion by combining the parameters such as the medium pressure and the medium flow rate in the medium circulation system. The flow heat transfer characteristics can provide technical support for the precise formulation of thermal hydraulic design and safety criteria of dispersed fuel elements.

[0051] The heat transfer simulation experiment device under the condition of bubbling on the surface of the diffuse fuel element provided in the embodiment of the present application realizes the external placement of the temperature measuring element (i.e., thermocouple). Compared with the existing concept of placing the temperature measuring element inside, the temperature measuring element in the present 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; and the present application can conveniently use temperature measuring elements of different precisions to measure the heated plate 5 to meet various test requirements during the test, and has relatively good applicability; after the measurement is completed, the elastic sealing cavity 113 can restore its original state under the action of its own elasticity, and under the elastic action of the elastic sealing cavity 113, the internal insulation powder 114 completes self-filling at the same time, which can prevent the heat loss of the heated plate 5 in a 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 the existing three-dimensional numerical simulation method, the heat transfer simulation experimental device under the condition of bubbling on the surface of the dispersed fuel element provided in the embodiment of the present application can perform direct measurement, with relatively less calculation amount, relatively more convenient implementation, more intuitive and easier to obtain data, and the measurement results have considerable credibility.

[0053] There are various ways of sealing the connection between the cover body 4 and the insulating base 6, for example, adhesive sealing, welding sealing, magnetic sealing, and threaded sealing can be used. Considering the maintainability of the entire device, in some optional embodiments, the cover body 4 is sealed and connected to the insulating base 6 through 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 body 4. For example, if the thermal conductivity of the cover body 4 is low, a static sealing ring with average heat resistance, such as a rubber sealing ring, can be selected. When the thermal conductivity of the cover body 4 is high, a static sealing ring with high heat resistance, such as a graphite sealing ring, can be selected. In actual implementation, it is usually expected that the thermal conductivity of the cover body 4 is low. In order to avoid a large amount of heat loss in the narrow slit channel 7, that is, in the working state, the temperature of the cover body 4 will not be too high, and the static sealing ring can be configured as a low-cost static sealing ring such as a rubber sealing ring; wherein, the static sealing ring is arranged around the circulation groove, and the shape of the static sealing ring can be not limited, for example, the static sealing ring can be such as rectangular, circular, triangular, diamond, etc., and can be specifically designed according to the adaptability of the notch of the circulation groove to avoid a large slit space after the cover body 4 is connected to the insulating base 6; for example, when the circulation groove is a rectangular groove body, its notch is rectangular, and the static sealing ring can be configured as a rectangle. Of course, in other embodiments, according to needs, such as different installation conditions and different processing accuracy, the shape of the static sealing ring can also be other special shapes.

[0054] After the heated plate 5 is connected to the insulating base 6, we prefer that the heated plate 5 has a single heat dissipation area to facilitate the control of the heat dissipation direction of the heated plate 5, for example, one of the plate surfaces of the heated plate 5 is in the narrow slit channel 7, while the other surfaces are relatively isolated from the narrow slit channel 7, so that the heat of the heated plate 5 can be basically dissipated from one of the plate surfaces of the heated plate 5 to the narrow slit channel 7. Therefore, in some optional embodiments, a mounting sink is constructed on the working surface of the insulating base 6, and the heated plate 5 is connected to the mounting sink and one of the plate surfaces is flush with the working surface. As a result, the other surfaces of the heated plate 5 are in contact with the insulating base 6, and the heat dissipation area of ​​the heated plate 5 in the narrow slit channel 7 is reduced, that is, the plate surface of the vacuum bubble portion is used as the heat dissipation surface, so that the heat dissipation direction of the heated plate 5 is certain, which is conducive to the analysis of the heat dissipation characteristics of the heated plate 5, and is conducive to predicting the heat distribution in the narrow slit channel 7, and can provide a certain theoretical basis for the experimental results.

[0055] The connection between the heated plate 5 and the insulating base 6 may not be limited, as long as it is ensured that the heated plate 5 can be fitted with the insulating base 6 surface to achieve a good insulation effect. However, due to the influence of processing accuracy, there may be a certain gap between the heated plate 5 and the insulating base 6 surface to surface. If the gap is a slit connected to the narrow slit channel 7, it may have a certain impact on the temperature of the local medium in the narrow slit channel 7, which will be detrimental to the detailed study of the heat transfer characteristics of the local medium in the narrow slit channel 7. Therefore, in some optional embodiments, the heated plate 5 is connected to the inner wall of the mounting sink by filling with sealant. The sealant can be a relatively heat-resistant sealant to prevent deformation due to excessive temperature and affect the sealing effect between the heated plate 5 and the sealant. It can be configured as silicone sealant, polyurethane sealant, fluororubber sealant, polytetrafluoroethylene sealant, high-temperature silicate sealant, etc.

[0056] The cover 4 can be configured as a transparent or opaque material, and both can realize the measurement of parameters such as the temperature of the medium in the narrow slit channel 7. Of course, if the cover 4 has a certain degree of transparency, it can realize the visual measurement of the velocity field and two-phase flow of the medium in 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. On the basis of having good light transmittance performance, optical quartz glass also has low thermal conductivity, which can reduce the heat loss of the medium in the narrow slit channel 7.

[0057] In the process of the heated plate 5 being electrically turned on, we hope that the current has better effective power, that is, the current basically only does work on the heated plate 5, so in some optional embodiments, the insulating base 6 is configured as an insulator, so as to greatly reduce power loss and ensure the safety of electricity use during the test. 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 a ceramic material, a fiber-reinforced ceramic-based material, a 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 an insulation function.

[0058] The conductive member 8 is usually connected to other devices with conductive requirements by welding. The heated plate 5 in the embodiment of the present application has a relatively high temperature in the working state, so the welding between the conductive member 8 and the heated plate 5 should have a certain heat resistance. Therefore, in some optional embodiments, the conductive member 8 is connected to the heated plate 5 by silver brazing. The thermal expansion coefficient of silver is smaller than that of copper, which means that when the temperature changes, the thermal stress generated by the silver brazing connection point is relatively small, which helps to reduce the risk of loose connection, and silver has good corrosion resistance, especially in high temperature environment, which helps to extend the service life of the welding part and ensure the conductive performance of the conductive member 8 and the heated plate 5.

[0059] In order to conveniently obtain the temperature field characteristics of the vacuum bubble and its surroundings, in some optional embodiments, the number of temperature measuring holes 10 is configured to be multiple, and in the normal viewing angle of the surface of the heated plate 5, the spacing between the multiple temperature measuring holes 10 and the vacuum bubble is not greater than 10 mm; it includes the temperature measuring holes 10 corresponding to the edge of the vacuum bubble, and in the medium flow direction, the bubble is 10 mm away from the vacuum bubble, and at least one temperature measuring hole 10 corresponds to the center position of the vacuum bubble.

[0060] For different heated plates 5, the positions and sizes of the vacuum bubble portions thereon are different. In view of this situation, in some optional embodiments, the insulating base 6 has a detachable positioning plate 11, and the positioning plate 11 can be configured as a polytetrafluoroethylene plate. The positioning plate 11 can specifically include a lower baffle 112 and an upper baffle 111, and the upper baffle 111 is embedded in the lower baffle 112. The overall shape of the lower baffle 112 is roughly a multi-diameter shaft body, and a matching groove is provided in the small diameter section of the lower baffle 112. The overall shape of the upper baffle 111 is similar to a circular cover body, and the upper baffle 111 is adapted to the shape of the matching groove so that the upper baffle 111 can be embedded in the matching groove, wherein the open end of the upper baffle 111 is located in the matching groove, and the closed end is located outside the matching groove, and the space in the upper baffle 111 serves as an installation cavity, and the 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 the cavity wall of the installation cavity, and the positioning plate 11 has There are temperature measuring holes 10, which means that some of the temperature measuring holes 10 among the multiple temperature measuring holes 10 are distributed on the positioning plate 11. Specifically, coaxial holes are respectively opened on the upper baffle 111 and the lower baffle 112, and every two coaxial holes on the upper baffle 111 and the lower baffle 112 serve as temperature measuring holes 10. The distribution forms of the temperature measuring holes 10 on different positioning plates 11 are different. According to the difference in 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, which means that according to the position and size of the vacuum bubble, different positioning plates 11 can be replaced to facilitate the thermocouple to measure the heated plate 5; wherein the positioning plate 11 corresponds to the position of the vacuum bubble; in actual implementation, the specific shape of the positioning plate 11 may not be limited, and it may be constructed as a cylinder to adapt to the detection range around the vacuum bubble. In other embodiments, the positioning plate 11 may also be constructed as a prism, a hemispherical or other special-shaped shapes. The positioning plate 11 can also be removed, and the bubble position on the heated plate 5 is exposed, which is convenient for measuring the wall temperature field by an infrared thermometer.

[0061] See also Figure 3 It can be understood that the projection area of ​​the positioning plate 11 in the normal direction of the heated plate 5 may be much larger than the vacuum bubble portion. At this time, temperature measuring holes 10 can also be set on the positioning plate 11 at positions corresponding to the surroundings of the vacuum bubble portion. These temperature measuring holes 10 correspond one-to-one to the temperature measuring holes 10 on the insulating base 6 and are coaxially arranged.

[0062] In some optional embodiments, the heat transfer simulation experimental device under the condition of bubbling on the surface of the dispersed fuel element 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 insulation base 6 and is connected to the narrow slit channel 7. The number of the pressure measuring pipes 13 can be configured as two. In the flow direction of the medium, the two pressure measuring pipes 13 are respectively located on both sides of the vacuum bubble. Preferably, the two pressure measuring pipes 13 are respectively arranged close to the medium inlet 1 and the medium outlet 2. Through the arrangement of the pressure measuring pipe 13, the medium pressure in the narrow slit channel 7 can be measured, and the change characteristics of the medium pressure on both sides of the vacuum bubble can be obtained, which is conducive to the study of the influence of the vacuum bubble on the medium pressure under the heat generation state.

[0063] In some optional embodiments, the medium inlet 1 and / or the medium outlet 2 are provided with a temperature measuring pipe 12. In actual implementation, the temperature measuring pipe 12 can be provided on both the medium inlet 1 and the medium outlet 2. The temperature measuring pipe 12 can be conveniently provided to measure / monitor the medium temperature before the medium enters the narrow slit channel 7 and after the medium flows out of the narrow slit channel 7, which can bring convenience to the measurement process and facilitate the acquisition of the dynamic change characteristics of the medium temperature under long-term operation.

[0064] In some optional embodiments, the heat transfer simulation experimental device under bubbling conditions on the surface of the dispersed fuel element also includes a first pressure block 9 and a second pressure block 3 arranged at intervals, and the first pressure block 9 is connected to the second pressure block 3, wherein the first pressure block 9 abuts against the base, and the second pressure block 3 abuts against the cover body 4.

[0065] In the embodiment of the present application, by setting the first pressure-bearing block 9 and the second pressure-bearing block 3, the cover body 4 and the insulating base 6 can be pressed together, so as to ensure the stability of the sealing performance between the cover body 4 and the insulating base 6. The first pressure-bearing block 9 and the second pressure-bearing block 3 can be constructed as a rectangular parallelepiped, the first pressure-bearing block 9 can form a cover on the insulating base 6, the second pressure-bearing block 3 can form a cover on the cover body 4, and the first pressure-bearing block 9 and the second pressure-bearing block 3 can be fastened and connected by bolts. Among them, the temperature measuring pipe 12, the conductive part 8, the pressure measuring pipe 13, the medium inlet 1, the medium outlet 2 and the positioning plate 11 can all pass through the first pressure-bearing block 9 and the insulating base 6 in sequence to communicate with the narrow slit channel 7 or connect with the heated plate 5; when the cover body 4 has a light transmittance of not less than 98%, an observation window can be opened on the second pressure-bearing block 3, and in the normal direction of the plate surface of the heated plate 5, the vacuum bubble portion is located within the range covered by the observation window.

[0066] Among them, 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, so that there is no need to set a connecting structure corresponding to the positioning plate 11 on the insulating 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 portion. The insulating base 6 does not participate in connecting the positioning plates, and the risk of structural damage to the insulating base 6 is greatly reduced, thereby ensuring that it has long-term stable thermal insulation and / or insulation performance.

[0067] In some optional embodiments, see Figure 5 The heated plate includes a blister plate 51, a heating plate 52 and an insulating layer 53; the blister plate 51 is formed with a groove through a casting process; the heating plate 52 and the blister plate 51 are arranged in parallel and spaced apart; the insulating layer 53 is located between the blister plate 51 and the heating plate 52, the insulating layer 53 is connected to the heating plate 52, and the insulating layer 53 is connected to the blister plate 51 through vacuum diffusion welding to enclose a vacuum bubble portion with the groove on the blister plate 51.

[0068] When the heated plate provided in the present application is used in an experimental device for simulating the heat transfer characteristics under the condition of bubbling on the surface of a diffuse fuel element, since the heating plate 52 relies on power to generate heat to simulate the heating of the diffuse fuel element, through the setting of the insulating layer 53, the current only passes through the heating plate 52 and does not pass through the bubbling plate 51, thereby truly simulating the distribution of heat sources in the prototype fuel element. It can avoid the situation where the self-heating of the bubbling plate 51 affects the temperature field near the vacuum bubble portion, that is, reduces the influencing factors of the temperature field near the vacuum bubble portion, facilitates subsequent theoretical analysis, and ensures the accuracy and credibility of the experimental results; and the insulating layer 53 is connected to the bubbling plate 51 by vacuum diffusion welding, and the connecting part has the characteristic of high temperature resistance, which is suitable for the bubbling temperature environment on the surface of the diffuse fuel element.

[0069] In actual implementation, the bubble plate 51 is configured as an Inconel625 plate, so that the thermal conductivity of the bubble plate 51 can be close to the parameters of the zirconium alloy cladding in the dispersed fuel element, and the thickness of the bubble plate 51 is configured to be no more than 1 / 10 of the thickness of the heating plate 52; the portion of the heating plate 52 used for conduction is configured as an S32168 plate to ensure good intergranular corrosion resistance and high temperature strength, wherein the heating plate 52 as a whole can be configured as an S32168 plate; the insulating layer 53 can be formed by coating an aluminum nitride ceramic layer on the surface of the heating plate 52 using a PVD process, and the insulating layer 53 can be formed by coating an aluminum nitride ceramic layer on the surface of the heating plate 52 using a PVD process. The thickness of the insulating layer 53 is 30 to 50 μm so as to not exceed 1 / 10 of the thickness of the blister plate 51, thereby achieving effective insulation under the operating conditions of a maximum voltage of 50 V in the experiment; the resistivity of the blister plate is much higher than that of the heating plate. In this way, if cracks appear in the insulating layer 53 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 affects the temperature field of the vacuum bubble portion within an acceptable range, so that the experimental device has 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 condition of bubbling on the surface of the dispersed fuel element provided in the embodiment of the present application can simulate the gap thermal resistance of the bubbling area of ​​the dispersed fuel element, the cooling boundary shape of the narrow channel 7 and its heat transfer conditions; it is conducive to the measurement of experimental data such as the wall temperature near the vacuum bubble part, the fluid temperature field and velocity field in the narrow channel 7, and the visualization measurement of the boiling two-phase flow type in the narrow channel 7, so as to obtain the flow heat transfer characteristics near the vacuum bubble part, and then provide a reference basis for the actual study of the heat transfer characteristics of the dispersed fuel element under the bubble state.

[0071] The above specific embodiments illustrate the implementation methods of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. Although the description of the present application will be introduced in conjunction with some embodiments, this does not mean that the features of this application are limited to the implementation methods. On the contrary, the purpose of introducing the application in conjunction with the implementation methods is to cover other options or modifications that may be extended based on the claims of the present application. In order to provide an in-depth understanding of the present application, the above description contains many specific details. The present application can also be implemented without using these details. In addition, in order to avoid confusion or blurring the focus of the present application, some specific details will be omitted in the description. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0072] It should be noted that in this specification, similar numbers and letters represent similar items in the above drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In the description of this application, it should be noted that the orientation or position relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be a connection between the two elements. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0073] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A heat transfer simulation experimental device under the condition of bubbling on the surface of a dispersed fuel element, characterized in that: include: A heated plate (5) capable of electrical conduction, wherein one plate surface of the heated plate (5) has a vacuum bubble portion; An insulating base (6), the heated plate (5) being connected to a working surface of the insulating base (6), an elastic sealing cavity (113) being arranged in the insulating base (6), the elastic sealing cavity (113) being filled with thermal insulation powder (114), and a temperature measuring hole (10) corresponding to the position of the vacuum bubble portion being provided on the insulating base (6), so that a thermocouple can pierce the elastic sealing cavity (113) through the temperature measuring hole (10) and contact the heated plate (5); A cover body (4), the cover body (4) having a flow slot, the cover body (4) being connected to the heat-insulating base (6) so that the heat-insulating base (6) seals the flow slot to form a narrow slit channel (7), and the heated plate (5) is located in the narrow slit channel (7); A medium introduction member (1), the medium introduction member (1) being in communication with one end of the narrow slit channel (7); A medium outlet (2), the medium outlet (2) being in communication with the other end of the narrow slit channel (7); Conductive members (8), two of the conductive members (8) are respectively connected to two ends of the heated plate (5), and the vacuum bubble portion is located between the two conductive members (8).

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

3. The heat transfer simulation experimental device under the condition of bubbling on the surface of the dispersed fuel element according to claim 1 or 2, characterized in that: A mounting sink is constructed on the working surface of the heat-insulating base (6), the heated plate (5) is connected to the mounting sink and one of the plate surfaces is flush with the working surface.

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

5. The heat transfer simulation experimental device under the condition of bubbling on the surface of the dispersed fuel element according to claim 1 is characterized in that: The light transmittance of the cover body (4) is configured to be no less than 98%.

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

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

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

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

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

11. The heat transfer simulation experimental device under the condition of bubbling on the surface of the dispersed fuel element according to claim 10, characterized in that: At least one temperature measuring hole (10) corresponds to the central position of the vacuum bubble portion.

12. The heat transfer simulation experimental device under the condition of bubbling on the surface of the dispersed fuel element according to claim 1, characterized in that: The insulating base (6) has a detachable positioning plate (11), wherein the positioning plate (11) includes a lower baffle (112) and an upper baffle (111) embedded in the lower baffle (112), and an installation cavity suitable for accommodating the elastic sealing cavity (113) is formed between the upper baffle (111) and the lower baffle (112), and the temperature measuring hole (10) is located on the positioning plate (11); wherein the positioning plate (11) corresponds to the position of the vacuum bubble portion.

13. The heat transfer simulation experimental device under the condition of bubbling on the surface of the dispersed fuel element according to claim 1 is characterized in that: It also comprises a pressure measuring pipe (13), wherein the pressure measuring pipe (13) is in communication with the narrow slit channel (7).

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

15. The heat transfer simulation experimental device under the condition of bubbling on the surface of the dispersed fuel element according to claim 1 or 12, characterized in that: It also comprises a first pressure-bearing block (9) and a second pressure-bearing block (3) arranged at intervals, wherein the first pressure-bearing block (9) is connected to the second pressure-bearing block (3), wherein the first pressure-bearing block (9) abuts against the base, and the second pressure-bearing block (3) abuts against the cover body (4).

16. The heat transfer simulation experimental device under the condition of bubbling on the surface of the dispersed fuel element according to claim 1, characterized in that: The heated plate (5) comprises: A blister plate (51), wherein the blister plate (51) is formed with a groove through a casting process; A heating plate (52), the heating plate (52) and the bubbling plate (51) are arranged in parallel and at intervals; An insulating layer (53), the insulating layer (53) is located between the blister plate (51) and the heating plate (52), the insulating layer (53) is connected to the heating plate (52), and the insulating layer (53) is connected to the blister plate (51) by vacuum diffusion welding so as to enclose a vacuum bubble portion with the groove on the blister plate (51).

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