Narrow slit channel flow heat transfer experiment device and method under asymmetric heat conduction blocking condition

Abstract

The invention belongs to the technical field, and discloses a narrow slit channel flow heat transfer experiment device and method under the asymmetric heat conduction blocking condition, the device adopts a single heating plate to generate heat, the heat is conducted to coolants in narrow slit channels on the two sides through test element plates, and different heat insulation cavities are formed in the test element plates on the two sides. The method is used for simulating the asymmetric heat transfer weakening effect caused by local deformation of the fuel element. The local heat exchange capacity of one side of the heat insulation cavity is reduced, and due to the thermal coupling effect, the heat transfer and boiling process, including boiling strength, bubble behavior characteristics and critical boiling characteristics, of the narrow slit channel on the other side will be affected. Therefore, by constructing a coupling structure composed of the single heating plate and the double rectangular narrow slit channels, the flow heat transfer characteristics and the heat flow redistribution rule of the narrow slit channels on the two sides under the asymmetric heat conduction blocking condition are compared and researched under the same working condition and the same boundary condition.

Description

Technical Field

[0001] This invention belongs to the field of heat transfer experiment, specifically relating to an experimental apparatus and method for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions. Background Technology

[0002] Particle-reinforced fuel elements (PRFs) use ceramic particles made of fissile material as reinforcement, which are combined with a metal matrix to form a core. This core is then encased in a metal cladding to form the nuclear fuel element. PRFs offer advantages such as large specific surface area, short heat transfer paths, and structural stability under neutron irradiation. The rectangular narrow-slot channels formed by PRFs are widely used in high-flux research reactors. However, under high burnup and high temperature conditions, fissile gas atoms tend to accumulate inside the fuel element, creating localized high pressure and leading to crack initiation. As the fissile gas pressure increases, the cracks gradually expand and open, eventually forming localized protrusions on the fuel element surface. Below these protrusions are cavities filled with fissile gas with low thermal conductivity. These cavities significantly weaken the heat transfer from the core to the coolant. As a result, the localized heat conduction process inside the fuel element exhibits asymmetric characteristics: the narrow-slot channel on one side of the cavity protrusion receives less heat, while the cladding on the other side bears a higher heat flow, resulting in a passive heat flow bias between the originally approximately symmetrical channels. This heat flow bias caused by localized insulation alters the flow boiling behavior of the narrow slit channels on both sides, causing one side to enter critical boiling prematurely while the overall average heat flow is still within an acceptable range, thereby reducing the system's safety margin.

[0003] In existing technologies, most studies on the boiling criticality and heat flux density distribution of narrow-slit channels are based on single channels, which cannot reflect the influence of asymmetric thermal conduction resistance on the heat flux redistribution and flow boiling phenomena of adjacent narrow-slit channels. Therefore, there is an urgent need to construct an experimental platform capable of handling asymmetric thermal conduction resistance caused by local cavities and simultaneously comparing the heat flux redistribution behavior of two channels, in order to systematically reveal the influence mechanism of local insulation regions on the boiling characteristics of narrow-slit channels, especially the critical boiling behavior. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that existing single-channel studies cannot reflect the influence of heat flow redistribution and boiling characteristics in dual-channel systems under asymmetric thermal conduction resistance, and to provide an experimental device and method for heat transfer in narrow-slit channels under asymmetric thermal conduction resistance conditions.

[0005] To achieve the above objectives, the present invention employs the following technical solution: This invention proposes an experimental device for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions, comprising a heating plate and two pressure-bearing shells symmetrically arranged on both sides of the heating plate, wherein the heating plate is provided with a side insulating plate. Each pressure-bearing housing has a test element plate and a channel glass arranged sequentially in the direction away from the heating plate. The test element plate is in contact with the heating plate to receive and transfer heat. The two pressure-bearing housings have viewing windows on the side away from the heating plate. Both test element plates are machined with raised features to simulate local heat insulation areas. The raised features and the heating plate form a heat insulation cavity. The pressure-bearing shell, the test element plate, and the channel glass together form a rectangular narrow slit channel. The inlet end of the rectangular narrow slit channel is connected to a fluid inlet assembly, and the outlet end is connected to a fluid outlet assembly.

[0006] Preferably, sealing rings are provided between the inner wall of the pressure-bearing housing and the test element plate, and between the inner wall of the pressure-bearing housing and the channel glass.

[0007] Preferably, the sealing ring is made of fluororubber.

[0008] Preferably, the heating plate is an Inconel 625 alloy electric heating plate and is powered by a DC power supply.

[0009] Preferably, the surface of the heating plate is provided with an aluminum oxide insulating coating.

[0010] Preferably, the side insulating plate is made of alumina ceramic and is used to block the conductive path between the heating plate and the pressure-bearing housing and the test element plate.

[0011] Preferably, a window cover plate is provided on the outside of the window glass, and the window glass is pressed and fixed by the window cover plate by window bolts.

[0012] Preferably, an air gap is formed between the channel glass and the viewing window glass, and the air gap is filled with an inert gas.

[0013] Preferably, the channel glass is borosilicate glass or quartz glass.

[0014] The present invention proposes an experimental method for a narrow-slit channel flow heat transfer experimental device under asymmetric thermal conduction resistance conditions, comprising the following steps: A side insulating plate is installed on the heating plate to block the conductive path between the heating plate and the pressure-bearing housing and the test element plate; The working fluid is introduced into the rectangular narrow slit channel formed by the pressure shell, the test element plate and the channel glass through the fluid inlet component to form a stable flow; The heating plate is activated to increase the heating power, causing the overall temperature of the test element plates on both sides to rise slowly. Through the heat insulation cavity formed between the protruding feature and the heating plate, heat flow obstruction zones and heat flow redistribution phenomena of different degrees are formed in the rectangular narrow slit channel. As the power continues to increase, boiling occurs in the rectangular narrow slit channel. Once critical boiling is observed, the power supply to the heating plate is cut off, and the working fluid is discharged through the fluid outlet assembly.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention proposes an experimental device for flow heat transfer in a narrow slit channel under asymmetric thermally impeded conditions. Because the test section uses a single heating plate to simultaneously heat both test element plates, an increase in the thermal resistance of one test element plate not only alters its own heat flow distribution but also affects the overall temperature field of the heating plate and the heat distribution pattern transferred to the other plate. This may lead to the other rectangular narrow slit channel entering boiling earlier under the same inlet conditions, or changes in its boiling intensity, bubble distribution, and critical boiling behavior. Based on this thermal coupling relationship, this device can directly compare the flow boiling behavior of both sides under different local thermal insulation conditions within the same test section. Through symmetrical structural arrangement and adjustable local thermally impeded design, different thermal resistance conditions can be formed on both sides of the test section, thereby simulating the thermal insulation region generated by the local accumulation of fission gas at the interface between the cladding and the fuel core during actual operation. This type of insulation area leads to a decrease in local heat transfer capacity, causing the heat released by the fuel core to be redistributed between the two cladding shells. This ultimately manifests as a spatial shift in wall heat flux density and a heat flux bias phenomenon, revealing the mechanism by which heat transfer degradation on one side affects boiling initiation and heat flux bias on the other side.

[0016] Furthermore, the insulation cavity significantly increases the equivalent thermal resistance of the region, resulting in a reduction in the amount of heat received locally on that side and altering the local heat conduction path, forcing the heat flow to redistribute laterally or backward within the plate.

[0017] Furthermore, the sealing ring material is preferably fluororubber to ensure stable sealing performance under high temperature, high pressure and two-phase flow environments. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a structural diagram of the experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions according to the present invention.

[0020] Figure 2 This is a cross-sectional view of the test specimen along the central axis of the present invention.

[0021] Figure 3 This is a schematic diagram of the explosion of the test specimen of the present invention.

[0022] Figure 4This is a schematic diagram of the two-dimensional geometric model of the present invention. Figure 5 This is a schematic diagram of the two-dimensional mesh model of the present invention.

[0023] Figure 6 The temperature distribution cloud map of the present invention is shown in ((a) and (c) for the local temperature distribution with the presence of the insulation cavity, and (b) for the local temperature distribution without the insulation cavity).

[0024] Figure 7 This invention illustrates the temperature variation along the thickness direction at the centerline of the heat insulation cavity.

[0025] Figure 8 The heat flux density of the test element plate near the heating plate varies with axial position in this invention.

[0026] Figure 9 This invention illustrates the temperature variation along the center line of the heating plate with axial position.

[0027] Among them, 1-fluid inlet component, 2-fluid outlet component, 3-pressure bearing shell, 4-viewing window cover, 5-viewing window glass, 6-air gap, 7-channel glass, 8-rectangular narrow slit channel, 9-test element plate, 10-heat insulation cavity, 11-heating plate, 12-side insulation plate, 13-viewing window bolt, 14-pressure bearing shell bolt. Detailed Implementation

[0028] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0029] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0032] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] The present invention will now be described in further detail with reference to the accompanying drawings: This invention proposes an experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions, such as... Figures 1 to 3 As shown, the structure includes a fluid inlet assembly 1, a fluid outlet assembly 2, a pressure-bearing shell 3, a viewing window cover 4, a viewing window glass 5, an air gap 6, a channel glass 7, a rectangular narrow slit channel 8, a test element plate 9, a heat insulation cavity 10, a heating plate 11, a side insulation plate 12, viewing window bolts 13, and pressure-bearing shell bolts 14. The main body of the test section consists of two symmetrically arranged pressure-bearing shells 3. The heating plate 11 serves as the heat source for this test section, simulating the core of the fuel element. The heating plate 11 uses an Inconel 625 alloy electric heating plate and is powered by a DC power supply. The two sides of the test section are symmetrically arranged, forming a "double rectangular narrow slit channel" overall structure. This allows for the simultaneous creation of different heat flow obstruction conditions within the two side channels, enabling tests under different heat flow obstruction conditions to be conducted synchronously under consistent operating conditions.

[0034] The experimental setup is described in detail below. An experimental setup for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions includes a heating plate 11 and a pressure-bearing shell 3 symmetrically installed on both sides of the heating plate 11. A side insulating plate 12 is provided on the heating plate 11. The side insulating plate 12 is made of alumina ceramic and is used to block the conductive path between the heating plate 11 and the pressure-bearing shell 3 and the test element plate 9, thereby achieving insulation.

[0035] Each pressure-bearing housing 3 contains a test element plate 9 and a channel glass 7 arranged sequentially along the direction away from the heating plate 11. The test element plate 9 contacts the heating plate 11 to receive and transfer heat. The channel glass 7 is located on the side closer to the working fluid, preferentially bearing the effects of high temperature but with a smaller pressure difference. The channel glass 7 is made of high borosilicate glass or quartz glass to balance temperature resistance and light transmission. Sealing rings are provided between the inner wall of the pressure-bearing housing 3 and the test element plate 9, and between the inner wall of the pressure-bearing housing 3 and the channel glass 7. The sealing ring material is preferably fluororubber to ensure stable sealing performance under high temperature, high pressure, and two-phase flow environments. The pressure-bearing housing 3 is externally connected by pressure-bearing housing bolts 14, so that the internal heating plate 11 is securely clamped between the two test element plates 9. The heating plate 11 has an alumina insulating coating to achieve electrical insulation and improve the high temperature resistance of the heating surface.

[0036] The pressure-bearing shell 3, the test element plate 9, and the channel glass 7 form a rectangular narrow-slit channel 8. The channel cross-section has a relatively large aspect ratio between its long and short sides, and its narrow width forms a typical narrow-slit structure, which is beneficial for enhancing heat transfer, strengthening boiling phenomena, and observing two-phase flow. The inlet end of the rectangular narrow-slit channel 8 is connected to the fluid inlet assembly 1, and the outlet end is connected to the fluid outlet assembly 2. The two form a continuous flow channel for the working fluid. The fluid inlet assembly 1 is used to introduce the liquid working fluid and can control the flow rate and subcooling of the fluid entering the two side channels. The fluid outlet assembly 2 is used to discharge the working fluid and connect to measuring equipment such as pressure sensors. The test element plate 9 and the heating plate 11 are in surface contact, allowing the heating plate 11 to transfer heat to the test element plate 9, so that the heat is introduced into the rectangular narrow-slit channel 8 along the thickness direction of the test element plate 9, achieving indirect heating.

[0037] The test element plate 9, serving as a fuel cladding simulation component, has raised features on its surface simulating localized heat insulation areas. These features protrude towards the rectangular narrow slit channel 8, and their geometry can be designed as spheres, cuboids, ellipsoids, or other shapes. Their size, position, and distribution can be adjusted according to the experimental purpose. Functionally, this feature has a dual effect: firstly, it alters the flow channel geometry within the rectangular narrow slit channel 8, thus intervening in fluid flow; secondly, it forms a heat-insulating cavity 10 between the raised feature and the heating plate 11. The formation of the heat-insulating cavity 10 significantly increases the equivalent thermal resistance of the test element plate 9 in this region, significantly weakening the original primary heat transfer path in the thickness direction. Due to the increased localized thermal resistance, heat will no longer be directly transferred to the wall of the narrow slit channel 8 along the original path, but will instead be redistributed laterally or in the opposite direction, resulting in a localized redistribution of heat flux density and a spatial heat flux bias on the channel heating surface.

[0038] Both pressure-bearing housings 3 have viewing windows 5 on the side away from the heating plate 11. A viewing window cover 4 is provided on each viewing window 5, and the viewing window 5 is secured to the housing by the viewing window cover 4 and viewing window bolts 13, forming the outer pressure-bearing structure of the entire observation window assembly. An air gap 6 is formed between the channel glass 7 and the viewing window 5, and this gap 6 is filled with an inert gas. If argon gas at an appropriate pressure is filled in, its low thermal conductivity can significantly reduce the heat conduction of the high temperature of the working fluid to the viewing window, allowing the viewing window to only meet the pressure-bearing strength requirement.

[0039] This invention proposes an experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions, including its working principle and experimental method. The working fluid is introduced into the rectangular narrow slit channels 8 on both sides through the fluid inlet component 1, and the flow rate on both sides is adjusted to be consistent to ensure that the heat transfer experiment is carried out under the same stable flow state at the inlet.

[0040] Inert gas is slowly introduced into the air gap 6. The pressure difference between the two sides of the channel glass 7 is maintained within the design range by adjusting the pressure of the inert gas to prevent the channel glass from cracking due to excessive pressure difference.

[0041] After the flow stabilizes, the heating plate 11 is activated, and the heating power is gradually increased according to the preset power grading method, so that the overall temperature of the test element plates 9 on both sides rises slowly. This allows the power supply to be cut off in time when critical boiling occurs or the heating wall surface experiences a rapid temperature rise, thereby ensuring the safe operation of the test section.

[0042] Because the test element board has a heat insulation cavity 10 inside, the heat is redistributed in a local area, resulting in heat flow obstruction zones and heat flow redistribution phenomena of varying degrees in the rectangular narrow slit channel 8.

[0043] As the heating power increases, boiling begins to occur within the narrow slit channel. The two-phase flow behavior can be recorded through the observation window, and signs of critical boiling (such as rapid increase in wall temperature and expansion of the gas film) can be identified in a timely manner.

[0044] Due to the different distribution of insulation cavities on the left and right sides, different boiling intensities, cavitation aggregation locations, and critical boiling points will occur, which can be compared and analyzed.

[0045] When a critical boiling point is observed or a set data point is reached: immediately cut off the power supply to the heating plate 11 to prevent overheating and damage to the test section; maintain the working fluid flow cooling system to allow the temperature of the test section to gradually decrease; after the overall temperature returns to room temperature, stop the supply of working fluid and release the inert gas pressure in the air gap 6.

[0046] By replacing the test element plate 9 with different designs of the thermal insulation cavity 10, or adjusting its installation position, the above test steps can be repeated to obtain experimental results comparing the double narrow slit channels under different thermal conduction weakening conditions.

[0047] The present invention proposes an experimental device for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions. Its function and principle are as follows: This invention, through a symmetrical structural arrangement and adjustable local thermal resistance design, enables the test section to form different thermal resistance conditions on both sides, thereby simulating the heat-insulating region generated by the local accumulation of fission gas at the interface between the cladding and the fuel core during actual operation. This type of heat-insulating region leads to a decrease in local heat transfer capacity, causing the heat released from the fuel core to redistribute between the two cladding sides, ultimately manifesting as a spatial shift in wall heat flux density and a heat flux offset phenomenon. The structural design of this invention can effectively reproduce the above physical behavior, thus enabling comparative research on the heat flux redistribution mechanism of fuel under local failure conditions.

[0048] The present invention proposes an experimental method for a narrow-slit channel flow heat transfer experimental device under asymmetric thermal conduction resistance conditions, comprising the following steps: A side insulating plate 12 is provided on the heating plate 11 to block the conductive path between the heating plate 11 and the pressure-bearing housing 3 and the test element plate 9; The working fluid is introduced into the rectangular narrow slit channel 8 formed by the pressure shell 3, the test element plate 9 and the channel glass 7 through the fluid inlet component 1 to form a stable flow; The heating plate 11 is activated to increase the heating power, so that the overall temperature of the test element plates 9 on both sides rises slowly. Through the heat insulation cavity 10 formed between the protruding feature and the heating plate 11, heat flow obstruction areas and heat flow redistribution phenomena of different degrees are formed in the rectangular narrow slit channel 8. As the power continues to increase, boiling occurs in the rectangular narrow slit channel 8. When critical boiling is observed, the power supply to the heating plate 11 is cut off, and the working fluid is discharged through the fluid outlet assembly 2.

[0049] The following description uses examples: Numerical simulation of thermally hindered boiling in a double rectangular narrow slit channel based on Fluent 1. Numerical Calculation Methods This embodiment uses the commercial computational fluid dynamics software Fluent to perform a numerical simulation of the double rectangular narrow slit channel test device under the condition of local heat flow obstruction in the aforementioned embodiment. This simulation can easily extract the transient fluid flow and heat transfer behavior under the effect of local heat flow obstruction, including the detailed spatial and temporal distribution of temperature. This helps to analyze the influence mechanism of local heat flow obstruction on the flow and heat transfer characteristics of two adjacent rectangular narrow slit channels.

[0050] 2. Geometric Model and Mesh Generation This embodiment selects, as follows: Figure 3 A two-dimensional computational model of the double rectangular narrow slit channel and the test element plate is established at the cross-section of the test section's central axis, as shown below. Figure 4 As shown. The computational domain includes a fluid domain and a solid domain, encompassing two rectangular narrow slit channels 8, a heat-insulating cavity 10, a heating plate 11, and two test element plates 9 on both sides. The geometric parameters are consistent with those of the test specimen, such as... Figure 4 As shown, the geometric parameters are as follows: Channel length: L F = 332 mm; Heating plate length: L H = 300 mm; Channel gap width: δ F = 2.3 mm; Heating plate thickness: δ H = 3.6 mm; Test element plate thickness: δ C = 3.6 mm.

[0051] 3. Mathematical Model The Fluent computational model used in this embodiment is shown in Table 1.

[0052] Table 1 Selection of Calculation Model

[0053] 4. Materials, Mesh Generation, and Boundary Conditions In the fluid region, the rectangular narrow slit channels 8 on both sides are set as water at atmospheric pressure; the heat insulation cavity 10 is set as air at atmospheric pressure (which better meets the feasible experimental conditions); in the solid region, the heating plate 11 is made of Inconel alloy material; the test element plates 9 on both sides are made of copper material, whose physical properties change with temperature.

[0054] Grid division as follows Figure 5As shown, the inlet flow velocity is set to 0.1611 m / s, the temperature to 338 K, and the outlet absolute pressure to 0.1 MPa. There is no slippage on the insulating outer wall. The heat source is constant, and the power is uniformly distributed across the entire heating plate, with a power density of 4.868e8 W / m³. 3 .

[0055] 5. Discussion of Results The above two-dimensional model was simulated, and the results of temperature distribution, gas-liquid phase volume distribution, and heat flux density distribution were obtained. The results are analyzed as follows: Figure 6 The temperature distribution across the entire computational domain is shown, with a local comparison of the temperature distribution in the uninsulated cavity, as follows: Figure 6 (b) shows the temperature distribution on one side where there is an insulating cavity, such as... Figure 6 (a) and Figure 6 In (c), the results show that the presence of the heat insulation cavity 10 leads to a significant temperature drop on the test element plate 9 on the same side.

[0056] To more intuitively compare the changes in temperature distribution caused by the presence of the insulation cavity 10, we will... Figure 6 The temperature at the centerline of the insulation cavity at point (a) is plotted as a curve, as shown below. Figure 7 As shown, the results indicate that the presence of the insulation cavity 10 leads to a 20°C temperature difference between the two channel walls, which may cause premature boiling within the channel. When the gas phase volume fraction is >0.8, it indicates that critical boiling is occurring. Critical boiling causes a sharp drop in the heat transfer coefficient, resulting in a sharp rise in the heating element temperature and causing the element to burn out.

[0057] Figure 8 The figure shows the change in heat flux density on the side of the test element plate 9 closest to the heating plate with axial position. As can be seen from the figure, the presence of the insulation cavity 10 causes the heat flux density on this side to be almost zero, while the heat flux density on the other side increases significantly. This also explains the distribution of the temperature field.

[0058] For heating plate 11, extract the temperature at the center line position, such as Figure 9 As shown, the heat insulation cavity 10 on both sides of the test element plate (9) has a significant impact on the local temperature of the heating plate, causing the local temperature to rise.

[0059] In this embodiment, after implementing the above steps, the result cloud map of the embodiment can be obtained. The temperature cloud map and distribution calculated in this embodiment are as follows: Figures 6 to 9 As shown, the presence of the insulating cavity 10 demonstrates that it may lead to premature boiling within the channel and the occurrence of critical boiling.

[0060] The experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions proposed in this invention has the following advantages: (1) A double-sided thermal coupling experimental structure consisting of a double rectangular narrow slit channel and a single heating plate By using a single heating plate to simultaneously heat narrow channels on both sides, the local heat transfer reduction of the test element plate on one side will couple to affect the other side through the heating plate. This allows the device to simulate the cross-channel heat flow redistribution phenomenon of fuel under local insulation and reveal the influence mechanism of heat transfer degradation on one side on boiling initiation and heat flow bias on the other side.

[0061] (2) Replaceable modular test element board, supporting the construction of various local insulation conditions. The test element plate adopts a modular design, which can be processed into localized thermal insulation features with different geometries, dimensions, and spatial distributions, and can be easily replaced after each test. By constructing a variety of representative typical operating conditions, this structure enables the test device to conduct systematic studies on the heat flow redistribution, boiling evolution, and critical heat flow variation of fuel under complex thermal conduction conditions at a relatively low cost.

[0062] The dual-rectangular narrow-slit channel and single heating plate form a double-sided thermally coupled experimental structure, enabling the study of the impact of localized heat transfer attenuation on one side on the boiling characteristics and heat flux distribution of the other side. Replaceable modular experimental element boards support the construction of various localized insulation conditions. By distributing different geometries, sizes, and insulation cavities, low-cost, multi-condition, and repeatable systematic studies can be achieved.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions, characterized in that, It includes a heating plate (11) and two pressure-bearing shells (3) symmetrically arranged on both sides of the heating plate (11), and the heating plate (11) is provided with a side insulating plate (12). Each pressure-bearing housing (3) has a test element plate (9) and a channel glass (7) arranged sequentially in the direction away from the heating plate (11). The test element plate (9) is in contact with the heating plate (11) to receive and transfer heat. The two pressure-bearing housings (3) have viewing windows (5) on the side away from the heating plate (11). Both test element plates (9) are processed with protrusions for simulating local heat insulation areas. The protrusions and the heating plate (11) form a heat insulation cavity (10). The pressure-bearing shell (3), the test element plate (9) and the channel glass (7) together form a rectangular narrow slit channel (8). The inlet end of the rectangular narrow slit channel (8) is connected to the fluid inlet assembly (1), and the outlet end is connected to the fluid outlet assembly (2).

2. The experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions according to claim 1, characterized in that, A sealing ring is provided between the inner wall of the pressure-bearing housing (3) and the test element plate (9), and between the inner wall of the pressure-bearing housing (3) and the channel glass (7).

3. The experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions according to claim 2, characterized in that, The sealing ring is made of fluororubber.

4. The experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions according to claim 1, characterized in that, The heating plate (11) is an Inconel 625 alloy electric heating plate and is powered by a DC power supply.

5. The experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions according to claim 1, characterized in that, The surface of the heating plate (11) is provided with an aluminum oxide insulating coating.

6. The experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions according to claim 1, characterized in that, The side insulating plate (12) is made of alumina ceramic and is used to block the conductive path between the heating plate (11) and the pressure-bearing housing (3) and the test element plate (9).

7. The experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions according to claim 1, characterized in that, The window glass (5) is provided with a window cover plate (4) on the outside, and the window glass (5) is pressed and fixed by the window cover plate (4) by window bolts (13).

8. The experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions according to claim 1, characterized in that, An air gap (6) is formed between the channel glass (7) and the viewing window glass (5), and the air gap (6) is filled with an inert gas.

9. The experimental apparatus for heat transfer in a narrow slit channel under asymmetric thermal conduction resistance conditions according to claim 1, characterized in that, The channel glass (7) is borosilicate glass or quartz glass.

10. An experimental method for a narrow-slit channel flow heat transfer experimental apparatus under asymmetric thermal conduction resistance conditions, characterized in that, The apparatus according to any one of claims 1 to 9 comprises the following steps: A side insulating plate (12) is provided on the heating plate (11) to block the conductive path between the heating plate (11) and the pressure-bearing shell (3) and the test element plate (9); The working fluid is introduced into the rectangular narrow slit channel (8) formed by the pressure shell (3), the test element plate (9) and the channel glass (7) through the fluid inlet component (1) to form a stable flow; The heating plate (11) is activated to increase the heating power, so that the overall temperature of the test element plates (9) on both sides rises slowly. Through the heat insulation cavity (10) formed between the protrusion feature and the heating plate (11), different degrees of heat flow obstruction area and heat flow redistribution phenomenon are formed in the rectangular narrow slit channel (8). As the power continues to increase, boiling occurs in the rectangular narrow slit channel (8). When critical boiling is observed, the power supply to the heating plate (11) is cut off, and the working fluid is discharged through the fluid outlet assembly (2).

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