Device for simulating local concentration of heat flow in rectangular narrow slit channel

Abstract

The invention relates to the technical field of reactor safety, and provides a device for simulating local concentration of heat flow in a rectangular narrow-slit channel, which comprises a core body, an insulating layer and a pressure-bearing shell are sequentially attached and wrapped outside the core body, the rectangular narrow-slit channel is arranged in the core body, two ends of the core body are respectively connected with a flow channel inlet and a flow channel outlet which are communicated with the rectangular narrow-slit channel, and the flow channel inlet and the flow channel outlet are communicated with the pressure-bearing shell. The flow channel inlet and the flow channel outlet are both connected with conductive copper bars used for being externally connected with a power source to enable the core body to emit heat, a groove used for forming local concentration of heat flow density is formed in the single-side wide outer plate face of the core body, and the local resistance of the core body is changed by controlling the size of the groove. The heat flow density of a specified proportion is controllably increased in a specific area of the surface of the rectangular narrow slit channel, a heat flow density local concentration area is formed, the heat flow local concentration condition of the prototype fuel element is simulated, the groove depth of the groove in the length direction is gradually reduced from the center to the two sides, and the heat flow density of the heating surface of the heat flow concentration area is uniform; and the prototype nuclear heat release characteristic can be simulated more accurately.

Description

Technical Field

[0001] The invention relates to the field of reactor safety technology, in particular to a device for simulating local concentration of heat flow in a rectangular narrow slit channel. Background Art

[0002] When preparing dispersed fuel elements, nuclear fission particles may aggregate locally, which increases local reactivity and causes the heat flux density in the local area to be higher than that in the surrounding area, forming a local concentration of heat flux. This local concentration may cause high-temperature hot spots and generate bubbles in the local area, changing the local flow pattern in the area, thereby triggering the boiling critical phenomenon in advance.

[0003] The current research mainly focuses on the boiling critical behavior characteristics under uniform heating and cosine distribution non-uniform heating conditions. However, in the case of local concentration of heat flux, the boiling critical phenomenon caused by the change of flow pattern is different. Local concentration of heat flux is crucial to the safety of dispersed fuel elements. Therefore, it is urgent to study the influence of local concentration of heat flux on the boiling critical behavior characteristics to provide technical support for the thermal hydraulic design and safety analysis of dispersed fuel elements. Summary of the invention

[0004] The purpose of the present invention is to provide a device for simulating local concentration of heat flux in a rectangular narrow slit channel, so as to solve the above-mentioned technical problems, improve the uniformity and control accuracy of the heat flux density of the heating surface in the heat flux concentration area, and more accurately simulate the heat release characteristics of the prototype core.

[0005] The embodiment of the present invention is achieved through the following technical scheme: a device for simulating local concentration of heat flux in a rectangular narrow slit channel, comprising a core body, an insulating layer and a pressure-bearing shell tightly wrapped around the outside of the core body in sequence, a rectangular narrow slit channel is arranged in the core body, two ends of the core body are respectively connected to a flow channel inlet and a flow channel outlet connected to the rectangular narrow slit channel, the flow channel inlet and the flow channel outlet are both connected to a conductive copper busbar for an external power supply to heat the core body, a groove for forming a local concentration of heat flux density is opened on a single wide outer plate surface of the core body, the groove depth along the length direction of the groove gradually decreases from the center to both sides, the length direction of the groove is arranged along the width direction of the core body, and the groove is opened at the center position of the width direction of the core body.

[0006] Furthermore, the groove is a semi-elliptical groove.

[0007] Furthermore, the core body is formed by overlapping and sealingly welding two parallel metal plates of equal thickness.

[0008] Preferably, the depth of the groove does not exceed 2 / 3 of the thickness of the metal plate, and the distance between the bottom of the groove and the rectangular narrow slit channel is not less than 1 mm.

[0009] Furthermore, a distance of more than 5 mm is left between the edge of the groove in the length direction and the edge of the core body in the width direction.

[0010] Furthermore, the narrow sides of the core body are cut obliquely.

[0011] Furthermore, the narrow edges on both sides of the rectangular narrow slot channel are chamfered.

[0012] Furthermore, a plurality of first temperature measuring holes penetrating the insulation layer for detecting the bottom temperature of the groove are evenly spaced on the pressure shell along the width direction of the core body, and the depths of the plurality of first temperature measuring holes are arranged to match the variation trend of the groove depth.

[0013] Furthermore, a plurality of groups of second temperature measuring holes penetrating the insulation layer for detecting the temperature of the outer wall of the core are provided on the pressure shell along the length direction of the core, and each group of second temperature measuring holes has a plurality of holes evenly arranged along the width direction of the core.

[0014] Furthermore, both the flow channel inlet and the flow channel outlet are connected with a temperature measuring pipe for detecting the temperature of the fluid.

[0015] The present invention has at least the following advantages and beneficial effects: the core is heated by directly energizing the conductive copper busbar, a groove is opened on the wide outer plate surface on one side of the core, and the local resistance of the core is changed by controlling the size of the groove, so that the heat flux density in a specific area on the surface of the rectangular narrow slit channel in the core can be controllably increased by a specified proportion, forming a local concentrated area of ​​heat flux density, simulating the local concentration of heat flux in the prototype fuel element, and at the same time, the groove depth along the length direction of the groove gradually decreases from the center to both sides, so that the heat flux density of the heating surface in the heat flux concentrated area is uniform, which can more accurately simulate the heat release characteristics of the prototype nuclear. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0017] Figure 1 A schematic diagram of the structure of a device for simulating local concentration of heat flow in a rectangular narrow slit channel provided by the present invention;

[0018] Figure 2 A cross-sectional view of a groove in a device for simulating local concentration of heat flow in a rectangular narrow channel provided by the present invention;

[0019] Figure 3 A schematic diagram of the structure of a core in a device for simulating local concentration of heat flow in a rectangular narrow slit channel provided by the present invention;

[0020] Figure 4 A cross-sectional view of a core in a device for simulating local concentration of heat flow in a rectangular narrow slit channel provided by the present invention;

[0021] Icon: 1-core, 100-metal plate, 10-rectangular narrow slit channel, 11-groove, 2-flow channel inlet, 3-flow channel outlet, 4-conductive copper busbar, 5-insulating layer, 6-pressure shell, 7-temperature measuring pipe, 81-first temperature measuring hole, 82-second temperature measuring hole. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0023] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example

[0025] like Figure 1-4As shown, in this embodiment, a device for simulating local concentration of heat flux in a rectangular narrow slit channel is mainly disclosed, which can be applied to heat transfer experiments under local concentration of heat flux in a rectangular narrow slit channel 10 and other experiments with non-uniform wall temperature heating requirements, including a core body 1, an insulating layer 5 and a pressure shell 6 are tightly wrapped around the outside of the core body 1 in sequence, a rectangular narrow slit channel 10 is arranged in the core body 1, and a flow channel inlet 2 and a flow channel outlet 3 connected to the rectangular narrow slit channel 10 are respectively connected at both ends of the core body 1, and a conductive copper bus 4 for connecting an external power supply to heat the core body 1 is connected to the flow channel inlet 2 and the flow channel outlet 3, and a groove 11 for forming a local concentration of heat flux density is opened on a single wide outer plate surface of the core body 1, and the groove The groove depth 11 along its length direction gradually decreases from the center to both sides, the length direction of the groove 11 is arranged along the width direction of the core 1, and the groove 11 is opened at the center position of the width direction of the core 1; it should be noted that the core 1 is in the shape of an elongated strip, the width direction of the core 1 is the wide side, and the thickness direction of the core 1 is the narrow side, and a rectangular narrow slit channel 10 arranged along the length direction of the core 1 is opened inside it, and the rectangular narrow slit channel 10 is located at the center position of the core 1, and the movement path of the fluid is the flow channel inlet 2, the rectangular narrow slit channel 10 and the flow channel outlet 3 in sequence, and the flow channel inlet 2 and the flow channel outlet 3 are respectively connected to the end of the core 1 by sealing welding; the simulation device adopts direct power heating , a conductive copper busbar 4 is fully connected to the connection ends of the flow channel inlet 2, the flow channel outlet 3 and the core body 1 by silver brazing, and the positive and negative electrodes of the external power supply are respectively connected. Through the conduction of the flow channel inlet 2 and the flow channel outlet 3, the core body 1 between the two conductive copper busbars 4 becomes an effective heating section; a groove 11 is directly milled on the single-side wide outer plate surface of the core body 1 by precision machining, and the size of the groove 11 is effectively controlled, thereby changing the local resistance of the core body 1, and realizing a controllable increase in a specified proportion of heat flux density in a specific area on the surface of the core body 1, forming a local concentrated area of ​​heat flux density. Specifically, the groove 11 can be set at any position in the length direction of the core body 1, and by changing the depth of the groove 11 degree, which can effectively change the heat flux concentration (i.e., the ratio of the heat flux density in the local concentrated area of ​​heat flux density to the average heat flux density of the core 1); the heat flux concentration area can be changed by changing the projection area of ​​the groove 11, so as to simulate the local concentration of heat flux density of the fuel element, and effectively reduce the complexity and cost of the simulation test; the groove depth of the groove 11 along its length direction gradually decreases from the center to both sides, which can limit the volume heat release concentration area to the central area of ​​the flow channel, so that the volume heat release on both sides of the length direction of the groove 11 gradually decreases, the volume heat release concentration area coincides with the heat flux concentration area, and the heat flux density of the heating surface of the heat flux concentration area is uniform, which can more accurately simulate the heat release characteristics of the prototype nuclear.

[0026] Furthermore, in the specific implementation, Figure 2-4As shown, the groove 11 provided in the embodiment of the present invention is a semi-elliptical groove. By changing the groove depth of the semi-elliptical groove, the heat flux concentration can be effectively changed; by changing the groove width and length of the semi-elliptical groove, the heat flux concentration area can be changed.

[0027] Furthermore, in the specific implementation, Figure 3 , 4 As shown, the core 1 provided in the embodiment of the present invention is formed by overlapping and sealing two parallel metal plates 100 of equal thickness; specifically, the wide side surfaces of the two metal plates 100 are butted against each other, and the narrow side surfaces are welded closed, and a rectangular narrow slit flow channel is formed in the middle, which can increase the thickness of the metal plate 100 to improve the variable range of adjusting resistance by changing the thickness; preferably, the depth of the groove 11 does not exceed 2 / 3 of the thickness of the metal plate 100, and the depth of the groove 11 changes so that the heat flux concentration presents an approximately linear change, and the distance between the bottom of the groove 11 and the rectangular narrow slit channel 10 is not less than 1 mm to ensure the integrity of the boundary of the rectangular narrow slit channel 10 during use.

[0028] Furthermore, in the specific implementation, Figure 3 , 4 As shown, a spacing of more than 5 mm is left between the length direction edge of the above-mentioned groove 11 provided in the embodiment of the present invention and the wide side edge of the core 1; it should be noted that after the groove 11 is opened on the core 1, the local narrow side heat flux density may increase, and a spacing of more than 5 mm is left between the length direction edge of the groove 11 and the wide side edge of the core 1, so that the local narrow side heat flux density of the groove 11 section of the core 1 does not exceed 1.15 times the overall average value of the narrow side of the core 1 to meet application requirements.

[0029] Furthermore, in the specific implementation, Figure 3 , 4 As shown, the narrow sides of the core 1 provided in the embodiment of the present invention are cut obliquely; it should be noted that, since the heat release area of ​​the prototype fuel core corresponds to the wide side of the rectangular narrow slit channel 10, in order to avoid excessive heating of the three sides near the narrow side under direct current heating, resulting in a significantly larger heating amount at this location than the prototype, the metal at the narrow side is cut to reduce the calorific value of the narrow side, ensuring that the heat flux density of the narrow side does not exceed half of the heat flux density of the wide side; in addition, the narrow sides of the rectangular narrow slit channel 10 on both sides are chamfered; specifically, the right-angled edges where the narrow side and the wide side of the boundary of the rectangular narrow slit channel 10 intersect are chamfered to weaken the bubble-forming characteristics at this location.

[0030] Furthermore, in the specific implementation, Figure 1 , 2As shown, on the pressure-bearing shell 6 provided in the embodiment of the present invention, a plurality of first temperature measuring holes 81 penetrating the insulating layer 5 for detecting the bottom temperature of the groove 11 are evenly spaced along the width direction of the core 1, and the depths of the plurality of first temperature measuring holes 81 are arranged to match the depth variation trend of the groove 11; on the pressure-bearing shell 6, a plurality of groups of second temperature measuring holes 82 penetrating the insulating layer 5 for detecting the outer wall temperature of the core 1 are opened along the length direction of the core 1, and each group of second temperature measuring holes 82 is evenly arranged along the width direction of the core 1; the flow channel inlet 2 and the flow channel outlet 3 are both connected to a temperature measuring pipe 7 for detecting the temperature of the fluid; it should be noted that, in the groove 11 section of the core 1, a first temperature measuring hole 81 is opened on one side of the groove 11, and a second temperature measuring hole 82 is opened on the back side of the groove 11 corresponding to the first temperature measuring hole 81; and on the core 1 In the non-groove 11 section, the second temperature measuring holes 82 can be opened on the wide side outer plate surfaces on both sides of the core 1 in a positive and negative correspondence; it is worth noting that at least one group of second temperature measuring holes 82 is opened in a positive and negative correspondence at the position of the core 1 close to the flow channel outlet 3; by setting the temperature measuring pipe 7, the first temperature measuring hole 81 and the second temperature measuring hole 82, and arranging thermocouples in the temperature measuring pipe 7, the first temperature measuring hole 81 and the second temperature measuring hole 82, the wall temperature and critical phenomenon of the core 1 are monitored, and the experimental data such as the wall temperature and fluid temperature field of the rectangular narrow slit channel 10 under the simulation condition of local heat flux concentration on the heating surface of the fuel element are measured, the full-cycle data of the wall temperature before the boiling critical triggering under the condition of local heat flux concentration and the flow heat transfer characteristics in the narrow slit channel are obtained, and the influence of local heat flux concentration on the boiling critical is understood.

[0031] In addition, in the specific implementation, the above-mentioned insulating layer 5 provided in the embodiment of the present invention is made of mica material, which has high mechanical strength, can withstand the pressure transmitted from the flow channel, and has excellent insulation and high temperature resistance. It should be noted that since the wall thickness of the core body 1 at the groove 11 is thinned, a boss that cooperates with the groove 11 is processed on the insulating block to play a filling and supporting role to prevent the core body 1 from being deformed under pressure and affecting the size of the rectangular narrow slit channel 10. The pressure-bearing shell 6 is composed of two shells that are interlocked and fastened with bolts. The shell can be made of stainless steel to ensure that the structure of the pressure-bearing shell 6 is tight.

[0032] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A device for simulating local concentration of heat flow in a rectangular narrow channel, characterized in that: The invention comprises a core body (1), the outer surface of which is tightly wrapped with an insulating layer (5) and a pressure-bearing shell (6), a rectangular narrow slit channel (10) is provided inside the core body (1), two ends of the core body (1) are respectively connected to a flow channel inlet (2) and a flow channel outlet (3) which are in communication with the rectangular narrow slit channel (10), the flow channel inlet (2) and the flow channel outlet (3) are both connected to a conductive copper bus (4) for connecting an external power source to heat the core body (1), a groove (11) for forming a local concentration of heat flux density is provided on a single wide outer plate surface of the core body (1), the groove depth of the groove (11) along its length direction gradually decreases from the center to both sides, the length direction of the groove (11) is arranged along the width direction of the core body (1), and the groove (11) is provided at the center position of the width direction of the core body (1).

2. A device for simulating local concentration of heat flow in a rectangular narrow channel according to claim 1, characterized in that: The groove (11) is a semi-elliptical groove.

3. The device for simulating local concentration of heat flow in a rectangular narrow channel according to claim 1, characterized in that: The core (1) is formed by overlapping and sealing two parallel metal plates (100) of equal thickness.

4. A device for simulating local concentration of heat flow in a rectangular narrow channel as claimed in claim 3, characterized in that: The depth of the groove (11) does not exceed 2 / 3 of the thickness of the metal plate (100), and the distance between the bottom of the groove (11) and the rectangular narrow slit channel (10) is not less than 1 mm.

5. The device for simulating local concentration of heat flow in a rectangular narrow channel according to claim 1, characterized in that: A distance of more than 5 mm is left between the edge of the groove (11) in the length direction and the edge of the wide side of the core (1).

6. The device for simulating local concentration of heat flow in a rectangular narrow channel according to claim 1, characterized in that: The narrow sides of the core (1) are processed by inclined cutting.

7. The device for simulating local concentration of heat flow in a rectangular narrow channel according to claim 1, characterized in that: The narrow sides of the rectangular narrow slit channel (10) are chamfered.

8. The device for simulating local concentration of heat flow in a rectangular narrow channel according to claim 1, characterized in that: A plurality of first temperature measuring holes (81) penetrating the insulating layer (5) for detecting the bottom temperature of the groove (11) are evenly spaced apart on the pressure-bearing shell (6) along the width direction of the core body (1), and are used to detect the bottom temperature of the groove (11). The hole depths of the plurality of first temperature measuring holes (81) match the depth variation trend of the groove (11).

9. The device for simulating local concentration of heat flow in a rectangular narrow channel according to claim 1, characterized in that: The pressure-bearing shell (6) is provided with a plurality of groups of second temperature measuring holes (82) penetrating the insulating layer (5) along the length direction of the core (1) for detecting the temperature of the outer wall of the core (1), and each group of the second temperature measuring holes (82) is evenly arranged in a plurality along the width direction of the core (1).

10. The device for simulating local concentration of heat flow in a rectangular narrow channel according to claim 1, characterized in that: The flow channel inlet (2) and the flow channel outlet (3) are both connected to a temperature measuring connection pipe (7) for detecting the temperature of the fluid.

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