Sleeve joint type double-layer pipeline telescopic sealing device

Abstract

The invention relates to the technical field of high-temperature fluid conveying of a molten salt reactor and an energy storage system, and discloses a sleeving type double-layer pipeline telescopic sealing device suitable for the high-temperature molten salt reactor and the energy storage system. The device comprises an outer pipe and an inner pipe assembly, wherein the inner pipe assembly is coaxially arranged in the outer pipe to form an annular heat insulation space; the inner pipe assembly comprises a first inner pipe and a second inner pipe which are connected in a sleeved mode, and a fit clearance is formed in the sleeved area. And the fit clearance is provided with a multi-stage structure to form a zigzag flow path, so that the high-temperature medium generates cooling, viscosity improvement and / or phase change by utilizing a temperature gradient, and dynamic sealing is realized. The technical problem that thermal expansion compensation and dynamic sealing of the high-temperature pipeline of the molten salt reactor are difficult to consider at the same time is solved, controllable leakage is achieved while large-amplitude axial thermal expansion compensation is allowed, sealing elements prone to being damaged are not needed, and the sealing device is high in reliability, long in service life and suitable for high-temperature fluid conveying scenes such as a high-temperature molten salt reactor nuclear energy system and an energy storage system.

Description

Technical Field

[0001] This application relates to the field of high-temperature fluid transportation technology for molten salt reactors and energy storage systems, and in particular to a thermal expansion compensation and sealing technology applicable to high-temperature pipeline systems in molten salt reactors and energy storage systems. Background Technology

[0002] In high-temperature nuclear energy systems, molten salt is used as a heat transfer medium. The heat from the molten salt in the reactor core is transferred to the power generation system through a piping system, enabling thermal energy utilization. In these systems, the operating temperature of the molten salt is typically between 600°C and 800°C, and the piping system needs to withstand the significant temperature difference between ambient and operating temperatures. In energy storage systems, novel thermal storage systems use molten salt as the heat storage medium. It absorbs solar energy during the day to heat to high temperatures and releases heat at night to generate electricity. The molten salt needs to be repeatedly transported between the storage tank and the heat exchanger. In these applications, the pipeline length often reaches several meters or even tens of meters, and the temperature difference can reach hundreds of degrees Celsius, leading to significant axial thermal expansion of the pipeline. In existing technologies, bellows compensators are commonly used to address the thermal expansion problem of the pipeline. Bellows compensators absorb the axial displacement of the pipeline through the elastic deformation of the bellows wall; their working principle is to release thermal stress by utilizing the repeated elastic deformation of the material. Traditional technologies also use stuffing box seals to solve the sealing problem at expansion joints, that is, filling the expansion joints of the pipeline with filler materials such as graphite or ceramic fibers, and forming a seal by compressing the filler. These technologies have achieved certain results in low- and medium-temperature, short-cycle applications. However, existing technologies have the following problems in high-temperature, long-cycle applications: Existing bellows compensators have inherent limitations in high-temperature applications. The working principle of bellows is the repeated elastic deformation of materials. Each thermal cycle will generate stress concentration at the crests and troughs of the corrugations. After thousands to tens of thousands of cycles, fatigue cracking is likely to occur. In particular, when the operating temperature exceeds 800℃, the high-temperature creep phenomenon of most metal materials is significant. Under continuous thermal stress, the bellows will undergo plastic deformation and creep damage, accelerating the fatigue failure process, and the service life is often no more than two years. The corrugated structure of the bellows compensator is prone to accumulating impurities and corrosion products. When conveying high-temperature media containing solid particles, the particles will deposit at the bottom of the corrugations and accelerate corrosion and wear. Stuffed box seals face multiple challenges at high temperatures. The packing material oxidizes, carbonizes, or burns at high temperatures, leading to rapid deterioration of sealing performance and a gradual increase in leakage. Friction exists between the packing and the axially sliding pipe surface, causing wear. Over long-term operation, the roughness of the sliding surface increases, further exacerbating the vicious cycle of leakage and wear. In some highly corrosive high-temperature media, such as molten salt environments, the packing material is also subject to chemical corrosion, resulting in a shorter service life and higher maintenance frequency. Existing technologies typically separate the compensation and sealing functions, with separate compensation and sealing devices, leading to complex system structures, large space requirements, and numerous potential failure points. More fundamentally, thermal expansion compensation requires a large degree of displacement freedom, while reliable sealing requires strict control over gaps and relative motion. These two aspects are inherently contradictory, making it difficult for traditional solutions to simultaneously achieve ideal results in terms of high temperature, large displacement, and tight sealing.Therefore, there is an urgent need for a new technical solution to address the above problems. This solution should be able to achieve reliable sealing while allowing for significant thermal expansion compensation, and should have advantages such as simple structure, no vulnerable parts, maintenance-free or low-maintenance operation, and long service life. Summary of the Invention

[0003] The purpose of this application is to provide a socket-type double-layer pipe expansion sealing device to solve the problems mentioned in the background art.

[0004] This application discloses a socket-type double-layer pipe expansion sealing device, comprising: an outer pipe; and an inner pipe assembly, coaxially disposed inside the outer pipe and forming an annular space between the inner and outer pipes; the inner pipe assembly includes a first inner pipe and a second inner pipe, which are axially connected by a socket to form a continuous internal channel for conveying a high-temperature medium; the first inner pipe and the second inner pipe form a fitting gap in the fitting area that allows relative axial sliding, the fitting gap forming a multi-stage structure to extend the leakage path, the multi-stage structure being configured to form a tortuous flow path, such that the high-temperature medium entering the fitting gap can utilize the temperature gradient formed by the annular space to generate cooling, viscosity increase and / or phase change to achieve dynamic sealing, thereby limiting the leakage of the high-temperature medium while allowing axial thermal expansion compensation between the first inner pipe and the second inner pipe.

[0005] In a preferred embodiment, the flow velocity within the annular space between the outer tube and the inner tube assembly is relatively slow, forming a heat-insulating space to reduce heat transfer from the inner tube assembly to the outer tube.

[0006] In a preferred embodiment, the multi-level structure provides a multi-level mating structure in the sleeve area, the multi-level mating structure including at least one of a stepped surface, an annular groove, an annular boss, a sawtooth groove, or a spiral groove.

[0007] In a preferred embodiment, the mating gaps of the multi-level structure form a multi-level labyrinthine sealing structure with a sealing level of 2 to 8.

[0008] In a preferred embodiment, adjacent sealing stages of the multi-stage labyrinth seal structure are spaced apart axially and staggered radially.

[0009] In a preferred embodiment, the radial clearance width of the mating gap is from 0.05 mm to 3.0 mm.

[0010] In a preferred embodiment, the axial clearance width of the fitting clearance is 0.1 mm to 1.0 mm.

[0011] In a preferred embodiment, the tortuous flow path achieves dynamic sealing through cooling, viscosity increase, and / or phase change of the high-temperature medium to obtain controlled microleakage.

[0012] In a preferred embodiment, both the outer tube and the inner tube assembly are made of nickel-based alloy, cobalt-based alloy, or high-temperature stainless steel.

[0013] In a preferred embodiment, the surface of the outer tube is provided with a high-temperature resistant inner lining; preferably, the high-temperature resistant inner lining is made of ceramic or ceramic matrix composite material, wherein the ceramic matrix composite material includes silicon carbide, alumina, zirconium oxide, aerogel or a combination thereof.

[0014] In a preferred embodiment, a guide support mechanism is further included, disposed in the sleeve area. The guide support mechanism includes a guide wear-resistant ring and / or a limiting structure. The guide wear-resistant ring is used to constrain the radial displacement of the inner tube assembly and prevent jamming, and the limiting structure is used to limit the maximum axial displacement of the inner tube assembly.

[0015] In a preferred embodiment, the relative axial displacement between the first inner tube and the second inner tube is 5 mm to 200 mm.

[0016] In a preferred embodiment, a leakage monitoring system is also included, which is configured to assess the integrity status of the outer tube as a pressure boundary by monitoring pressure and / or temperature changes outside the outer tube.

[0017] In a preferred embodiment, the device is suitable for conveying a high-temperature medium with a temperature range of 400°C to 1000°C; the high-temperature medium is at least one of molten metal, molten salt, molten silicate, or high-temperature slag.

[0018] In a preferred embodiment, the operating pressure of the continuous internal channel is from 0.1 MPa to 10 MPa.

[0019] In a preferred embodiment, the application of the above-described device in a high-temperature fluid transport system selected from a molten salt reactor nuclear energy system or an energy storage system is proposed.

[0020] In a preferred embodiment, the guide wear ring includes a spherical guide head disposed at the end of the first inner tube, the spherical guide head being configured to provide guidance and reduce insertion resistance when the first inner tube is inserted into the second inner tube.

[0021] In a preferred embodiment, the overlap length of the socket region along the axial direction The maximum axial thermal expansion of the device under the design temperature difference The following conditions must be met: in, For safety factor, and .

[0022] In a preferred embodiment, the safety factor The value range is from 1.2 to 2.0.

[0023] In a preferred embodiment, the axial overlap length of the socket region In addition to meeting the requirements for thermal expansion compensation, the integrity requirements of the sealing structure must also be met: in: This is the maximum axial thermal expansion of the device under the design temperature difference; The number of sealing stages in the multi-stage structure; This is the minimum effective length of a single-stage sealing section; For thermal expansion safety factor, and ; The structural integrity coefficient is, and .

[0024] The technical solution of this application has achieved significant technical effects through the systematic integration and synergistic cooperation of the above-mentioned technical means.

[0025] Firstly, by employing a double-layered separation structure of outer tube 1 and inner tube assembly 2, with an annular space 3 formed between them, the pressure-bearing function and the thermal insulation function are decoupled. Outer tube 1 serves as the primary pressure boundary, bearing the system's operating pressure, while inner tube assembly 2 directly contacts the high-temperature medium and performs the transport function. The flow velocity within the annular space 3 is relatively slow, forming a thermal insulation space that significantly reduces heat transfer from inner tube assembly 2 to outer tube 1. This ensures that even when inner tube assembly 2 is at extremely high temperatures, the shell temperature of outer tube 1 can be controlled within the material's safe range, thereby preventing material degradation, creep deformation, or oxidation corrosion of the outer tube due to high temperatures and extending the service life of the device.

[0026] Secondly, the first inner tube and the second inner tube are connected axially in a sleeved manner, forming a fitting gap 4 within the sleeved area 23 that allows for relative axial sliding. This fundamentally solves the problem of axial displacement caused by thermal expansion in high-temperature pipeline systems. When the system temperature rises from ambient temperature to operating temperature, the first inner tube and the second inner tube can freely slide relative to each other axially within the sleeved area 23, completely releasing the stress generated by thermal expansion. This avoids problems such as pipe deformation, weld cracking, or connection failure caused by thermal stress accumulation in rigid connections. Compared to traditional bellows compensators, this sleeved structure does not have the stress concentration and fatigue sensitivity characteristics of thin-walled corrugations. Therefore, it has higher reliability and a longer service life under long-term high-temperature operation conditions, and can withstand tens of thousands or even hundreds of thousands of thermal cycles without fatigue failure.

[0027] Furthermore, the multi-stage structure formed by the fitting gap 4 to extend the leakage path is the core technical means for leakage control in this application. By setting a multi-stage fitting structure in the socket area 23, including at least one of stepped surfaces, annular grooves, annular bosses, sawtooth grooves, or spiral grooves, the original straight gap is transformed into a tortuous flow path. With each stage of the sealing structure, the fluid velocity decreases, the pressure drops, and energy is dissipated. The cumulative effect of multiple stages causes the total flow resistance to increase geometrically. The number of sealing stages in the multi-stage labyrinth seal structure is 2 to 8. The increase in the number of sealing stages significantly extends the leakage path and increases the flow resistance. The arrangement of adjacent sealing stages spaced axially and staggered radially further enhances the complexity of the flow path, preventing the fluid from passing directly along the shortest path. It forces the fluid to repeatedly change its flow direction between the radial and axial directions, thereby maximizing the extension of the leakage path and increasing the flow resistance. The radial gap width of the fitting clearance is precisely controlled within the range of 0.05mm to 3.0mm, preferably 0.1mm to 1.0mm. According to the principles of fluid mechanics, for slit flow in laminar state, the leakage volumetric flow rate is proportional to the cube of the gap width. Therefore, precise control of the gap width can geometrically reduce the leakage amount significantly.

[0028] More importantly, the multi-stage structure is configured to form a tortuous flow path, allowing the high-temperature medium entering the mating gap 4 to utilize the temperature gradient formed by the annular space 3 to achieve cooling, viscosity increase, and / or phase change, thus realizing dynamic sealing. As the high-temperature medium enters the mating gap 4, its temperature gradually decreases due to its distance from the heat source and proximity to the relatively low-temperature annular space 3. For liquid phases or high-viscosity fluids such as molten salts, molten metals, or molten slag, their dynamic viscosity is extremely sensitive to temperature; a decrease in temperature leads to a sharp increase in viscosity, further increasing flow resistance. For some media with high freezing points, phase change occurs when the temperature drops below the freezing point, with some of the medium solidifying in the gap to form solid deposits, acting as a "self-sealing plug." This dynamic sealing mechanism, achieved through the cooling and property changes of the high-temperature medium itself, requires no additional sealing elements or materials. Therefore, it eliminates the problems of aging, ablation, and melting of sealing materials at high temperatures, fundamentally improving the reliability and durability of the sealing system. This method achieves controlled, minimal leakage, meaning it doesn't aim for absolute zero leakage, but rather uses proper design to control the leakage within a very small, safe, and acceptable range.

[0029] Furthermore, the guide support mechanism, through the guide wear-resistant ring and the limiting structure, constrains the radial displacement of the inner tube assembly 2 and prevents jamming, while also limiting the maximum axial displacement of the inner tube assembly. The guide wear-resistant ring ensures that the fitting clearance 4 between the first and second inner tubes remains uniform in the circumferential direction, avoiding problems such as excessively large or small local clearances caused by radial offset, allowing each stage of the multi-stage labyrinth seal structure to perform its sealing function uniformly and effectively under the designed clearance conditions. The limiting structure prevents the first and second inner tubes from completely disengaging under extreme working conditions or in the event of misoperation, providing a final safety guarantee.

[0030] Specifically, when the guide wear-resistant ring is positioned at the end of the first inner tube in the form of a spherical guide head (ball head) 26, it provides excellent guidance during the assembly process of inserting the first inner tube into the second inner tube and during the axial sliding process during operation. The spherical design of the spherical guide head 26 has self-centering capability, automatically compensating for minor radial deviations caused by manufacturing errors, assembly errors, or uneven thermal expansion, ensuring that the first and second inner tubes always maintain good coaxiality. This coaxiality is crucial for the effectiveness of the multi-stage labyrinth seal structure, as any radial offset will lead to uneven distribution of the mating clearance 4 in the circumferential direction, thus affecting the sealing effect of each stage of the seal structure. The synergistic cooperation between the spherical guide head 26 and the multi-stage labyrinth seal structure ensures that the device maintains stable and reliable sealing performance throughout its service life. In addition, the low-friction characteristics of the spherical contact reduce energy loss during axial sliding and reduce the interference of frictional heat generation on the temperature field of the mating clearance 4, which is beneficial for maintaining a clear temperature gradient to support the dynamic self-sealing mechanism.

[0031] The leakage monitoring system assesses the overall sealing status of the device by monitoring pressure and / or temperature changes outside the outer pipe 1, transforming the device from a passive sealing structure into an intelligent system with self-diagnostic capabilities. In the double-layered pipe structure of this device, the annular space 3 between the inner pipe assembly 2 and the outer pipe 1 is also filled with a high-temperature medium (e.g., molten salt at approximately 700°C on the inner side and 650°C on the outer side). The mating gap 4 allows the medium to slowly leak from the inner pipe into the annular space 3, but the outer pipe 1, as the pressure boundary, provides the final sealing protection. The monitoring system is located outside the outer pipe 1. When the outer pipe 1 suffers serious damage such as rupture, the monitoring system can promptly detect the abnormality and issue an alarm. Based on the monitoring data, operators can promptly understand the integrity of the outer pipe pressure boundary and intervene in the early stages of abnormal situations, preventing small problems from escalating into serious accidents, significantly improving the safety and reliability of the system.

[0032] The outer and inner tube assemblies are made of nickel-based alloys, cobalt-based alloys, or high-temperature stainless steel. These materials maintain high strength, good oxidation resistance, and corrosion resistance at high temperatures, enabling them to withstand the long-term effects of high-temperature media. A high-temperature resistant inner lining, made of ceramic or ceramic-based composite materials, is installed on the surface of the outer tube. This lining directly withstands the erosion and chemical corrosion of the high-temperature media, further protecting the metal outer tube from direct damage and significantly extending the service life of the device.

[0033] The device described in this application is suitable for conveying high-temperature media with temperatures ranging from 400°C to 1000°C, including various high-temperature fluids such as molten metal, molten salt, molten silicate, or high-temperature slag. Its operating pressure can range from 0.1 MPa to 10 MPa, making it suitable for a wide range of applications. In high-temperature fluid transport systems such as molten salt reactor nuclear energy systems and energy storage systems, the device described in this application can reliably handle thermal expansion and sealing issues.

[0034] It is particularly important to emphasize that the various technical features of this application do not exist in isolation, but rather cooperate and work synergistically. The interlocking structure provides the basis for thermal expansion compensation, the multi-stage labyrinth seal structure creates flow resistance, the temperature gradient field triggers a dynamic self-sealing mechanism, the guide support mechanism ensures structural stability, and the leakage monitoring system enables intelligent diagnosis. The organic combination of these technical means enables the device to achieve reliable sealing under extreme high temperature and large temperature difference conditions. More importantly, there is a positive synergistic enhancement effect among these technical features: the multi-stage labyrinth structure extends the flow path, providing sufficient length for the establishment of the temperature gradient; the temperature gradient-triggered dynamic self-sealing further reduces leakage and alleviates the burden on the multi-stage structure; the guide support mechanism ensures gap uniformity, ensuring the effectiveness of the multi-stage structure and dynamic sealing. This systematic integration and synergistic cooperation of multiple technical means is the fundamental reason why this application can achieve ideal results simultaneously in terms of high temperature, large displacement, and tight sealing.

[0035] In summary, this application integrates and coordinates various technologies, including a socket-type structure, multi-stage labyrinth seals, dynamic self-sealing, guide supports, and condition monitoring, to construct a high-temperature fluid transport sealing system. This system allows for significant thermal expansion compensation structurally, relies on media self-sealing rather than external sealing elements in its sealing mechanism, achieves predictable and controlled micro-leakage in leakage control, eliminates vulnerable and moving parts in terms of reliability, and reduces maintenance costs and extends service life in terms of economy. Compared to traditional bellows compensators, this application's device does not possess the stress concentration and fatigue-sensitive structural characteristics of thin-walled corrugations, thus exhibiting higher reliability and a longer service life under long-term high-temperature operation. Compared to traditional stuffing box seals, this application's device eliminates the need for packing material, avoiding problems such as packing oxidation, carbonization, or burn-out at high temperatures, as well as frictional wear between the packing and sliding surfaces. This achieves maintenance-free or low-maintenance operation, demonstrating significant technological advancement and broad application value in the field of high-temperature fluid transport.

[0036] The specification of this application contains numerous technical features distributed across various technical solutions. Listing all possible combinations of these technical features (i.e., technical solutions) would make the specification excessively lengthy. To avoid this problem, the various technical features disclosed in the above-described invention, the various technical features disclosed in the following embodiments and examples, and the various technical features disclosed in the accompanying drawings can be freely combined to form various new technical solutions (all of which are considered to have been described in this specification), unless such a combination of technical features is technically infeasible. For example, one example discloses feature A+B+C, and another example discloses feature A+B+D+E. Features C and D are equivalent technical means that serve the same function, and technically only one needs to be used; they cannot be used simultaneously. Feature E can technically be combined with feature C. Therefore, the solution A+B+C+D should not be considered as described because it is technically infeasible, while the solution A+B+C+E should be considered as described. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of a socket-type double-layer pipe expansion sealing device according to an embodiment of this application.

[0038] Figure 2 This is a schematic diagram of the structure of a socket-type double-layer pipe expansion sealing device according to another embodiment of this application.

[0039] Figure 3 This is a partially enlarged schematic diagram of the socket area according to an embodiment of this application.

[0040] in: 1: Outer tube; 2: Inner tube assembly; 23: Socket area; 26: Spherical guide head 3: Circular space; 4: Gap between fits. Detailed Implementation

[0041] In the following description, many technical details are presented to help the reader better understand this application. However, those skilled in the art will understand that the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.

[0042] Explanation of some concepts: Socket connection: This refers to a connection where the end of the first inner tube is inserted into the end of the second inner tube, with the two overlapping by a certain length in the axial direction to form a socket area. This allows for relative sliding in the axial direction while limiting media leakage through the fitting clearance. Unlike traditional welding, flange, or threaded connections, socket connections do not create rigid constraints and can freely adapt to axial displacement.

[0043] Fit clearance: refers to the minute radial gap between the outer surface of the first inner tube and the inner surface of the second inner tube. This gap allows the two inner tubes to slide relative to each other, and its width directly affects the amount of leakage. The radial clearance width of the fit clearance is typically in the millimeter or sub-millimeter range.

[0044] Multi-stage structure: This refers to multiple cascaded throttling and expanding structures within the mating clearance, including stepped surfaces, annular grooves, annular bosses, serrated grooves, or spiral grooves. These structures are arranged sequentially in the axial direction to form a multi-stage labyrinth seal. Each stage of the structure throttles the fluid, and the cumulative effect of multiple stages significantly increases the overall flow resistance.

[0045] A tortuous flow path refers to a complex flow path formed by multiple stages, where the fluid cannot flow in a straight line and must undergo multiple turns, expansions, and contractions. As the fluid passes through this path, its flow direction changes multiple times (radial-axial-radial), and its local velocity changes drastically, resulting in energy dissipation and pressure losses, thereby limiting leakage.

[0046] Dynamic sealing: Unlike static sealing which uses fixed sealing elements (such as sealing rings or packing), dynamic sealing refers to a sealing mechanism that utilizes the changes in the physical properties of the high-temperature medium during its flow within the mating gap (such as viscosity increase due to cooling or phase change solidification) to achieve a sealing effect. This sealing effect dynamically changes with operating conditions and has self-adjusting characteristics.

[0047] Controlled microleakage: This refers to a leakage control strategy that does not aim for absolute zero leakage, but rather uses proper design to control the leakage amount within a very small, safe, and acceptable range (typically on the order of milliliters per second or lower). This strategy allows for a small amount of leakage, but ensures that the leakage amount does not exceed the tolerance of the equipment and the environment.

[0048] The socket area refers to the region where the first inner tube and the second inner tube overlap axially. It is the core part of the socketed connection and the location where the multi-stage sealing structure is set. The axial length of this area is called the overlap length.

[0049] Annular space: refers to the annular space formed between the inner surface of the outer tube and the outer surface of the inner tube assembly. The flow rate of the medium in this space is slow, and its main function is to impede the transfer of heat from the inner tube assembly to the outer tube, thus forming a heat insulation layer.

[0050] Multi-stage labyrinth seal structure: This refers to a multi-stage seal structure arranged in series within the mating gap, resembling a complex labyrinthine path, where fluid must traverse multiple twists and turns to pass through. The number of seal stages typically ranges from 2 to 8; with each additional stage, the leakage path lengthens and flow resistance increases.

[0051] Temperature gradient field: This refers to the temperature distribution from the high-temperature zone to the low-temperature zone in the mating gap region due to the high temperature of the inner tube assembly, the low temperature of the outer tube, and the thermal insulation effect of the annular space. This temperature gradient field is a key condition for triggering changes in the physical properties of the medium and achieving dynamic self-sealing.

[0052] Thermal expansion safety factor: When calculating the overlap length of the socket area, a safety factor is multiplied by the theoretical thermal expansion amount to take into account the uncertainty of thermal expansion calculation and the fluctuation of material properties. It is used to ensure that the socket remains effective even under the maximum thermal expansion state.

[0053] Structural integrity factor: This refers to a factor introduced when calculating the total length of the required sealing structure to ensure that the multi-stage sealing structure remains intact (i.e., has sufficient number of stages and single-stage length) under any thermal expansion conditions. It is used to ensure that the sealing function will not fail due to thermal expansion.

[0054] The following is a brief summary of some of the innovative aspects of this application: In summary, the technical solution of this application has achieved a non-obvious technical breakthrough in the field of high-temperature fluid transportation. Its core innovation lies in the organic coupling of the socket-type connection structure (the first inner tube and the second inner tube are configured in the socket area 23 in a manner that allows relative axial sliding) with the multi-level labyrinth-type sealing structure in the fitting gap 4 (including multi-level fitting structures such as annular grooves and annular bosses) and the dynamic self-sealing mechanism based on the temperature gradient field. This creatively achieves the unity of thermal expansion compensation function and leakage control function in a single structural system, thereby fundamentally resolving the irreconcilable contradiction between the two technical requirements of "allowing large displacement degrees of freedom" and "strictly limiting gap leakage" in traditional technology.

[0055] Specifically, this application constructs a multi-stage structure for the fitting gap 4 within the socket region 23. This forces the high-temperature medium, when attempting to leak through this gap, to undergo multiple radial-axial-radial flow direction changes along a tortuous flow path composed of stepped surfaces, annular grooves, and annular bosses. Each stage of the sealing structure results in a sudden drop in flow velocity, pressure attenuation, and energy dissipation. Simultaneously, due to the thermal resistance layer formed by the annular space 3 between the outer tube 1 and the inner tube assembly 2, a temperature gradient field is established in the region where the fitting gap 4 is located, moving from the high-temperature continuous internal channel to the relatively low-temperature annular space 3. As the high-temperature medium flows along the tortuous path... As cooling progresses stepwise, the dynamic viscosity increases exponentially, leading to a sharp rise in flow resistance. For media with high freezing points, phase change may even occur, forming solid self-sealing plugs in the gaps. More importantly, this dynamic sealing mechanism based on the changes in the media's own physical properties and the flow resistance mechanism of multi-stage geometric throttling form a positive synergistic enhancement effect. The extended flow path of the multi-stage labyrinth structure provides the necessary time and space conditions for the establishment of temperature gradients and sufficient cooling of the media. The viscosity increase triggered by the temperature gradient further amplifies the flow resistance generated by the multi-stage structure. The two complement each other, limiting the leakage to a controlled, minute leakage level.

[0056] The non-obviousness of this technical concept is also reflected in the fact that although the socketed connection between the first and second inner tubes allows for a large relative axial sliding (5mm to 200mm), the multi-stage sealing structure in the fitting gap 4 does not fail due to this sliding. On the contrary, due to the configuration of the guide support mechanism, the radial width of the fitting gap 4 remains uniform throughout the circumferential direction, ensuring that each stage of the multi-stage labyrinth seal can function uniformly and effectively under the designed gap conditions. The "geometric resistance" of the multi-stage labyrinth seal and the "physical resistance" of the dynamic self-sealing form a dual sealing guarantee, and the synergistic cooperation between the two produces a comprehensive sealing effect far exceeding that of simple superposition. This application solves the technical contradiction between "thermal expansion compensation capability" and "sealing reliability" that has long plagued the industry in high-temperature pipeline systems in a device with a simple structure and no vulnerable parts through the nonlinear coupling and synergistic enhancement of this multi-dimensional and multi-mechanism technical feature. The formation of this technical concept requires a deep understanding and systematic grasp of fluid mechanics, heat transfer, materials mechanics, and the laws of physical property changes of high-temperature media, which cannot be easily obtained by those skilled in the art based on simple combinations or conventional improvements of existing technologies.

[0057] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only for explaining this application and are not intended to limit the scope of protection of this application.

[0058] Through long-term in-depth research and extensive practical observation, the inventors of this application have discovered that the problem of thermal expansion compensation and sealing in existing high-temperature pipeline systems is far more complex than the surface phenomena, involving deep-seated technical contradictions at multiple levels, including materials mechanics, fluid mechanics, heat transfer, and structural design.

[0059] After in-depth analysis, the inventors discovered that the fundamental reason why bellows compensators are prone to fatigue failure at high temperatures lies in the inherent contradiction in their working mechanism. The bellows absorbs thermal expansion displacement through repeated elastic deformation of the material, meaning that each thermal cycle generates plastic strain accumulation in the stress concentration areas of the bellows structure. Through in-depth research into material fatigue theory, the inventors realized that under high-temperature conditions, the fatigue strength of metallic materials decreases significantly, while creep slows down stress relaxation. The combination of these two factors leads to a significant acceleration in the initiation and propagation of fatigue cracks. This makes it difficult to guarantee the service life of bellows compensators in long-term high-temperature applications. Frequent replacements not only increase maintenance costs and downtime losses but also pose serious safety risks in high-radiation environments such as nuclear power plants. The reason existing technologies cannot effectively solve this problem is that as long as the working principle of elastic deformation is used, stress concentration and fatigue accumulation cannot be avoided. Attempting to increase strength by increasing the bellows wall thickness reduces the compensator's flexibility, requiring a larger driving force to generate deformation, thus creating a new technical bottleneck.

[0060] Furthermore, through a systematic study of the failure mechanism of stuffing box seals, the inventors discovered that the core problem of this type of sealing method lies in the inherent incompatibility between the sealing material and high-temperature sliding conditions. The stuffing material needs to possess good sealing performance, requiring a certain degree of plasticity and conformity; however, it also needs to withstand high temperatures and sliding friction, requiring high heat resistance and wear resistance. The inventors deeply understand that these two requirements are often contradictory in terms of material properties. Soft materials with good sealing performance are prone to softening and burning at high temperatures, while high-temperature resistant hard materials struggle to provide a good sealing effect. As a result, the stuffing inevitably deteriorates rapidly under high-temperature sliding conditions, leading to decreased sealing performance and increased leakage. Through repeated experiments, the inventors observed that even with the most advanced high-temperature stuffing materials, the degradation of sealing performance is still very significant at temperatures above 700°C, and the maintenance cycle is unlikely to exceed several months.

[0061] The inventors also noted that the existing practice of separating the thermal expansion compensation function from the sealing function is actually a compromise solution to the technical contradiction between the two functions, but this separation design introduces new system-level problems. First, the separate placement of the compensation device and the sealing device complicates the system structure, increases the number of failure points, and reduces overall reliability. Second, the movement of the compensation device will cause impact and vibration to the sealing device, accelerating its wear. Third, the coordination between the two devices requires precise design and debugging, increasing the difficulty of engineering implementation. Through analysis and research on a large number of engineering cases, the inventors found that in high-temperature, long-cycle applications, the failure rate of this separate design system is actually higher than that of a single-function device.

[0062] More importantly, after in-depth reflection, the inventors creatively proposed a crucial technological insight: the technical contradiction between thermal expansion compensation and sealing is not irreconcilable; the key lies in changing the working mechanism of the seal. Traditional sealing technologies, whether elastic seals, packing seals, or mechanical seals, all rely on the tight contact between the sealing element and the sealing surface to prevent media leakage. This "contact seal" inevitably generates friction and wear when relative motion exists, and it is even more difficult to maintain at high temperatures. The inventors keenly realized that if they could break free from the dependence on sealing elements and instead utilize the changes in the physical properties of the medium itself to achieve sealing, this technical contradiction could be fundamentally resolved.

[0063] Based on this technological insight, the inventors further analyzed the property changes of high-temperature media during temperature reduction. For liquid phases or high-viscosity fluids such as molten salts and molten metals, their dynamic viscosity is extremely sensitive to temperature; a decrease in temperature leads to an exponential increase in viscosity. Through theoretical analysis and experimental verification, the inventors realized that if a temperature gradient field from high to low temperature can be created in the sealing area, the rapid increase in medium viscosity can be used to significantly increase flow resistance, thereby controlling leakage. For some media with high freezing points, temperature reduction can also trigger phase changes, and the solid deposits formed after some media solidify can act as "self-sealing plugs." This sealing mechanism based on the changes in the media's own properties does not require any external sealing elements, thus eliminating the problem of sealing element failure at high temperatures and the frictional wear caused by relative motion.

[0064] Through systematic analysis, the inventors further realized that to achieve the aforementioned dynamic self-sealing based on changes in media properties, two key conditions must be met: first, there must be a sufficiently long leakage path, allowing the medium ample time for heat exchange and temperature reduction as it flows through the path; second, there must be a significant temperature gradient, ensuring sufficiently drastic changes in the medium's properties. Regarding the first condition, the inventors creatively proposed a multi-stage labyrinthine sealing structure design. By incorporating multi-stage throttling structures within the mating gap, the straight-through gap is transformed into a tortuous flow path, significantly extending the leakage path and increasing flow resistance. Regarding the second condition, the inventors proposed a double-layer pipe structure design. The inner pipe directly contacts the high-temperature medium, while the outer pipe has a lower temperature. The annular space between the two forms a heat insulation layer, naturally creating a temperature gradient field in the mating gap region.

[0065] Based on the aforementioned in-depth research and technical insights, the inventors creatively proposed the core technical concept of a socket-type double-layer pipe expansion sealing device: It employs a socket-type connection to achieve thermal expansion compensation, extends the leakage path through a multi-level labyrinth structure, and utilizes the temperature gradient formed by the double-layer structure to trigger the dynamic self-sealing of the medium. This organically unifies the thermal expansion compensation function and the sealing function into a simple structure, resolving the technical contradiction between the two functions and eliminating vulnerable parts and moving sealing elements, thus achieving the technical goals of high reliability, long service life, and maintenance-free operation. The implementation process of this invention will be described in detail below through specific embodiments.

[0066] This application provides a socket-type double-layer pipe expansion sealing device, which is particularly suitable for high-temperature medium transportation scenarios in nuclear energy systems such as high-temperature molten salt reactors and energy storage systems. In these applications, the operating temperature of high-temperature media (such as molten salt) is typically in the range of 400℃ to 1000℃, and the pipeline system will experience significant axial thermal expansion during the process of heating from ambient temperature to operating temperature. Traditional rigid pipe connection methods cannot effectively cope with this large-scale thermal expansion, while traditional bellows compensators are prone to fatigue failure at high temperatures. This application, through an innovative socket-type structural design, organically combines thermal expansion compensation and sealing functions, allowing the pipeline to undergo significant axial thermal expansion under high-temperature conditions, while controlling the leakage of high-temperature media within a safe range through a multi-stage labyrinth sealing structure and dynamic self-sealing mechanism.

[0067] I. Overall Structural Design like Figure 1 and Figure 2 As shown, the socket-type double-layer pipe expansion sealing device of this application mainly includes an outer pipe 1 and an inner pipe assembly 2. The inner pipe assembly 2 is coaxially disposed inside the outer pipe 1, forming an annular space 3 between the two. The inner pipe assembly 2 consists of a first inner pipe and a second inner pipe, which are connected axially in a socket manner to form a continuous internal channel for conveying high-temperature media.

[0068] Figure 1 The overall structure of the device and the relative positions of its main components are shown, clearly displaying the outer tube 1, the inner tube assembly 2, and the annular space 3 between them. Figure 2 The axial sleeve connection between the first inner tube and the second inner tube is further demonstrated, showing that the two inner tubes are arranged in an overlapping configuration within the sleeve area 23.

[0069] outer tube and annular space The outer tube 1 serves as the outer pressure-bearing boundary of the device, bearing the system's operating pressure and providing mechanical support. In typical applications, the operating pressure of the continuous internal channels can range from 0.1 MPa to 10 MPa. The outer tube 1 and the inner tube assembly 2 are coaxially configured, forming an annular space 3 between them. This annular space 3 plays an important role in thermal management in this application.

[0070] Specifically, the flow velocity within the annular space 3 between the outer tube 1 and the inner tube assembly 2 is relatively slow, forming an insulating space to reduce heat transfer from the inner tube assembly 2 to the outer tube 1. The 'slow flow velocity' refers to the fact that, because the cross-sectional area of ​​the annular space 3 is much larger than that of the continuous internal channel, and there is no forced driving force within the annular space, the medium in the annular space 3 is mainly driven by natural convection and a slight pressure difference, resulting in a flow velocity typically below 0.1 m / s, far lower than the forced convection velocity in the continuous internal channel (typically 1-10 m / s). This low flow velocity creates a relatively static medium layer within the annular space 3, generating a significant thermal resistance effect. The mechanism behind this thermal insulation effect is that the slow flow velocity of the medium in the annular space 3 requires a long heat transfer path and significant thermal resistance for heat to be transferred from the inner tube assembly 2 to the outer tube 1, thus drastically reducing the heat flux density. This "double-layer separation" structural design decouples the pressure-bearing function from the thermal insulation function, which is one of the key innovations of this application. With this design, even if the inner tube assembly 2 is in direct contact with the high-temperature medium, the shell temperature of the outer tube 1 can be controlled within the safe range allowed by the material, thereby avoiding material performance degradation, creep deformation or oxidation corrosion of the outer tube 1 due to high temperature.

[0071] Furthermore, the outer tube 1 can be made of nickel-based alloy, cobalt-based alloy, or high-temperature stainless steel to ensure sufficient strength and corrosion resistance in high-temperature environments. The choice of material needs to be determined based on specific operating conditions. For applications with operating temperatures below 600℃ and relatively weak corrosion, high-temperature stainless steel is preferred to reduce costs; for applications with operating temperatures between 700℃ and 900℃ that need to withstand molten salt corrosion, nickel-based alloy is preferred; for extreme high-temperature or highly corrosive applications, cobalt-based alloy or the addition of a ceramic inner lining can be considered.

[0072] As an optional improvement, a high-temperature resistant inner lining can be provided on the surface of the outer tube 1. This inner lining is preferably made of ceramic or a ceramic matrix composite. Exemplary ceramic matrix composites include silicon carbide, alumina, zirconium oxide, aerogel, or combinations thereof. The function of the high-temperature resistant inner lining is to directly withstand the potential erosion and chemical corrosion of the high-temperature medium, further protecting the metal outer tube 1 from direct damage, thereby significantly extending the service life of the device. The inner lining can typically be designed to be replaceable; when the inner lining is worn or damaged, it can be replaced individually without replacing the entire pipe, thus reducing maintenance costs.

[0073] Sleeve connection of inner tube assembly The inner tube assembly 2 includes a first inner tube and a second inner tube, which are connected axially by a sleeve connection. Specifically, the end of the first inner tube is inserted into the end of the second inner tube, or the end of the second inner tube is inserted into the end of the first inner tube, with the two overlapping by a certain length in the axial direction to form a sleeve region 23. Within this sleeve region 23, a fitting gap 4 is formed between the outer surface of the first inner tube and the inner surface of the second inner tube.

[0074] This socket-type connection method differs fundamentally from traditional rigid connections (such as welding or flange connections). In rigid connections, both ends of the pipe are completely fixed. When the temperature rises from ambient temperature to operating temperature, the stress generated by the thermal expansion of the pipe cannot be released, leading to a huge accumulation of thermal stress, which may cause pipe deformation, weld cracking, or connection failure. The socket-type connection, however, allows the first inner pipe and the second inner pipe to slide freely relative to each other axially within the socket area 23. The stress generated by thermal expansion is completely released, fundamentally solving the problem of thermal expansion compensation. In practical applications, the relative axial displacement between the first and second inner pipes can range from 5mm to 200mm to accommodate the thermal expansion requirements under different pipe lengths and temperature differences. This wide range of displacement compensation capabilities enables the device to be applied to long-distance pipelines and conditions with large temperature differences, expanding its application scope.

[0075] The inner tube assembly 2 is also made of nickel-based alloys, cobalt-based alloys, or high-temperature stainless steel. These materials maintain high strength, good oxidation resistance, and corrosion resistance at high temperatures, and can withstand the long-term effects of high-temperature media. The material selection is similar to that of the outer tube 1, and needs to be determined comprehensively based on factors such as operating temperature and media corrosivity. Exemplary nickel-based alloys include Inconel series alloys and Hastelloy series alloys; exemplary cobalt-based alloys include Haynes series alloys; exemplary high-temperature stainless steels include 316L and 310S. Through the nested connection of the first and second inner tubes, a continuous internal channel for conveying high-temperature media is formed. This channel can adapt to the conveying needs of various high-temperature media such as molten metal, molten salt, molten silicate, or high-temperature slag.

[0076] To further improve the durability and sliding performance of the device in high-temperature corrosive environments, at least a portion of the surface of the outer tube 1 or the inner tube assembly 2 may be provided with a coating made of diamond-like carbon or an inorganic material.

[0077] Diamond-like carbon (DLC) coating is an amorphous thin-film material composed of carbon, possessing high hardness, low coefficient of friction, excellent chemical inertness, and good wear resistance. In the application scenario of this application, DLC coating is particularly suitable for the sliding surface in the mating gap region 4, significantly reducing the frictional resistance between the first inner tube and the second inner tube during axial relative sliding, reducing surface wear, and extending the service life of the device. For applications with relatively low operating temperatures (e.g., 400°C to 500°C) or intermittent high temperatures, DLC coating provides excellent surface protection. For applications with even higher temperatures, doped and modified DLC coatings (e.g., silicon-doped or metal-doped DLC coatings) can be used to improve their thermal stability.

[0078] Inorganic coatings include, but are not limited to, nitride coatings, carbide coatings, oxide coatings, or boride coatings. Exemplary nitride coatings include titanium nitride (TiN), chromium nitride (CrN), aluminum nitride (AlN), silicon nitride (Si3N4), or composites thereof; exemplary carbide coatings include tungsten carbide (WC), titanium carbide (TiC), silicon carbide (SiC), or composites thereof; exemplary oxide coatings include alumina (Al2O3), zirconium oxide (ZrO2), chromium oxide (Cr2O3), or composites thereof; exemplary boride coatings include titanium boride (TiB2), etc. These inorganic coatings exhibit excellent high-temperature stability, corrosion resistance, and wear resistance, making them particularly suitable for applications operating at high temperatures (e.g., 600°C to 1000°C) and requiring exposure to corrosive media such as molten salts.

[0079] The coating can be applied to one or more of the following locations: the inner surface of the outer tube 1, the outer surface of the inner tube assembly 2, the sliding mating surface in the mating clearance 4 area, and the contact surface of the guide support mechanism. The thickness of the coating is typically in the range of 0.5 μm to 100 μm, preferably 1 μm to 50 μm, and can be adjusted according to specific application requirements and process conditions. The coating preparation process can employ methods such as physical vapor deposition (PVD), chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), thermal spraying, plasma spraying, or electroplating, selecting the appropriate process based on the characteristics of the coating material and the substrate material.

[0080] By applying the aforementioned coating to the surface of the outer tube 1 or the inner tube assembly 2, the following technical effects can be achieved: First, the high hardness and wear resistance of the coating can protect the base metal from wear, especially in the mating gap 4 area, where the relative sliding between the first inner tube and the second inner tube inevitably generates friction. The coating can significantly reduce the wear rate of the sliding surface and extend the service life of the device. Second, the chemical inertness and corrosion resistance of the coating can form a protective barrier on the surface of the base metal, blocking the direct erosion of the base metal by corrosive media such as molten salts, and improving the durability of the device in corrosive environments. Third, the low coefficient of friction of coatings such as diamond-like carbon can reduce the frictional resistance during axial sliding, making the thermal expansion compensation process smoother and reducing the interference of frictional heat generation on the temperature field of the mating gap 4, which is conducive to the stable performance of the dynamic self-sealing mechanism. Fourth, when the difference in the coefficient of thermal expansion between the coating and the base metal is small, the coating can maintain good adhesion during thermal cycling and is not prone to peeling or cracking, thereby continuously providing surface protection throughout the entire service life of the device.

[0081] II. Multi-stage structural design for fit clearance Based on the overall structure described above, the multi-stage structural design of the fitting gap 4 is a key technical means to achieve effective sealing. The first inner tube and the second inner tube form a fitting gap 4 in the sleeve region 23 that allows for relative axial sliding. This fitting gap 4 forms a multi-stage structure to extend the leakage path. This multi-stage structure is configured to form a tortuous flow path, allowing the high-temperature medium entering the fitting gap 4 to utilize the temperature gradient formed by the annular space 3 to achieve cooling, viscosity increase, and / or phase change, thereby achieving dynamic sealing. This limits the leakage of the high-temperature medium while allowing axial thermal expansion compensation between the first and second inner tubes.

[0082] Specific forms of multi-level mate structure See Figure 3 This figure is a partial enlarged schematic diagram of the socket area 23. Figure 3 The enlarged view on the left clearly shows the specific structure of the annular groove and the annular boss and their alternating arrangement. It can be seen that these structures are distributed sequentially in the axial direction to form a multi-level sealing structure. Figure 3 The enlarged view on the right shows the radial dimension of the mating clearance 4 and its positional relationship with the inner tube surface, clearly demonstrating the precise control of the clearance width.

[0083] The multi-level mating clearance 4 is provided in the sleeve area 23 with a multi-level mating structure, which may include at least one of the following: stepped surface, annular groove, annular boss, serrated groove, or spiral groove. These structures are arranged sequentially in the axial direction, transforming the original straight clearance into a tortuous flow path.

[0084] Specifically, a stepped surface refers to a radial abrupt change in the shape of a step on the surface of the first or second inner tube, forcing the fluid to undergo radial deflection as it passes through. An annular groove refers to an annular recessed structure machined on the surface of the inner tube, such as... Figure 3 As shown in the enlarged view on the left, the fluid undergoes expansion, retention, and re-contraction after entering the groove. An annular boss refers to an annular protrusion machined on the inner tube surface. In contrast to an annular groove, the fluid undergoes contraction, acceleration, and re-expansion when passing through the boss. A serrated groove is a groove with a serrated cross-section machined on the inner tube surface; the fluid must zigzag along the contour of the serrations as it passes through. A spiral groove is a spiral groove machined on the inner tube surface; the fluid not only advances axially but also undergoes a circumferential spiral motion, further extending the flow path.

[0085] In practical applications, one or more combinations of multi-stage mating structures can be selected based on specific working conditions and sealing requirements. For example, alternating arrangements of annular grooves and annular bosses can be used, such as... Figure 3 As shown, a multi-stage expansion-contraction flow path is formed; alternatively, a combination of stepped surfaces and sawtooth grooves can be used to achieve a dual throttling effect of radial deflection and axial tortuosity.

[0086] Multi-level labyrinth sealing structure The multi-stage structure with fitting gaps 4 forms a multi-stage labyrinth seal structure, with the number of sealing stages ranging from 2 to 8. Each additional sealing stage lengthens the leakage path and significantly increases flow resistance. The selection of the number of sealing stages requires comprehensive consideration of factors such as sealing performance requirements, manufacturing difficulty, and cost. For applications with high sealing requirements, a higher number of sealing stages (e.g., 6 to 8 stages) can be used; for applications with relatively low sealing requirements or cost sensitivity, a lower number of sealing stages (e.g., 2 to 4 stages) can be used.

[0087] Furthermore, in a multi-stage labyrinth seal structure, adjacent sealing stages are spaced axially and staggered radially. The advantages of this configuration are: the axial spacing provides sufficient space between sealing stages for fluid energy dissipation and temperature reduction; the radial staggered arrangement prevents fluid from passing directly along the shortest path, forcing the fluid to repeatedly change flow direction between the radial and axial directions, thereby maximizing the leakage path length and increasing flow resistance. Figure 3 As shown, when the fluid attempts to pass through the fitting gap 4, it must traverse this complex three-dimensional tortuous path, experiencing significant pressure drops and energy losses at each stage of the structure.

[0088] radial width of the mating clearance The radial width of the fitting gap 4 is one of the key parameters affecting leakage. According to fluid mechanics principles, for slit flow in laminar conditions, the leakage volumetric flow rate is proportional to the cube of the gap width. Therefore, precise control of the gap width is crucial for achieving leakage control objectives. Figure 3 As shown in the enlarged view on the right, the radial clearance width of the mating gap 4 can be set to a range of 0.05 mm to 3.0 mm. A smaller clearance width (such as 0.05 mm to 0.5 mm) can provide a better sealing effect, but requires higher manufacturing and assembly precision; a larger clearance width (such as 1.0 mm to 3.0 mm) is relatively easier to manufacture and assemble, but it is necessary to compensate for the decrease in sealing performance caused by the increased clearance by increasing the number of sealing stages or optimizing the multi-stage structure.

[0089] In a preferred embodiment, the axial width of the mating gap 4 can be controlled within the range of 0.1 mm to 1.0 mm. This range achieves a good balance between sealing performance and engineering feasibility. Within this gap range, combined with a multi-stage labyrinth seal structure and dynamic self-sealing effect, leakage can be controlled to a safe and acceptable level, while the manufacturing difficulty and cost are also within a reasonable range.

[0090] III. Dynamic Self-Sealing Mechanism The multi-stage structure not only provides geometric resistance, but more importantly, it creates the conditions for achieving dynamic self-sealing. A core innovation of this application lies in achieving dynamic self-sealing through a tortuous flow path. Specifically, the tortuous flow path achieves dynamic sealing through the cooling, viscosity increase, and / or phase change of the high-temperature medium to obtain controlled micro-leakage. The working principle of this dynamic self-sealing mechanism is as follows: When the high-temperature medium enters the fitting gap 4 from the continuous internal channel, its temperature gradually decreases as it moves away from the heat source and closer to the relatively low-temperature annular space 3. The tortuous flow path formed by the multi-stage fitting structure creates a temperature gradient field from the high-temperature region to the low-temperature region. Specifically, this temperature gradient field is a combined result of radial heat dissipation and axial temperature attenuation. Although the annular space 3 is configured as an insulating space to protect the outer tube 1, its ambient temperature is still significantly lower than that of the high-temperature medium in the continuous internal channel. Therefore, a suitable amount of heat flux is still allowed to pass through the radial direction of the first and second inner tubes, thereby establishing the necessary radial temperature difference. At the same time, the multi-stage labyrinth structure significantly extends the actual flow distance of the fluid, allowing the slightly leaking medium to gradually move away from the main heat source as it flows axially along the fitting gap 4, resulting in a significant axial temperature attenuation. This superposition of radial and axial gradients ensures that even with the insulating properties of the annular space, the end region of the fitting gap 4 can reach a low temperature sufficient to trigger a sharp increase in medium viscosity or a phase change. With each stage of the sealing structure, the fluid velocity decreases, the pressure drops, energy is dissipated, and the temperature decreases accordingly.

[0091] For liquid or high-viscosity fluids such as molten salts, molten metals, or molten slag, their dynamic viscosity is extremely sensitive to temperature. Generally, the viscosity of these fluids increases exponentially with decreasing temperature. As the temperature decreases, the intermolecular forces strengthen, and the flow resistance of the fluid increases significantly. This viscosity-increasing effect makes the flow of the fluid in the mating gap 4 more difficult, thereby further reducing leakage.

[0092] More importantly, for some media with high freezing points, a phase change occurs when the temperature drops below the freezing point, and part of the medium changes from liquid to solid. The solidified medium deposits in the fitting gap 4, forming a solid blockage that acts as a "self-sealing plug." This self-sealing plug effectively prevents further leakage of the high-temperature medium, achieving true dynamic self-sealing. It should be noted that the solid blockage formed by the phase change is usually a semi-solid, slurry-like soft deposit, or a loose crystalline layer with low structural strength that is easily sheared and broken, rather than a high-strength, dense, rigid solid. Because the axial driving force generated by the thermal expansion of the high-temperature pipeline under large temperature differences is extremely large, this driving force is much greater than the shear resistance required to destroy the solidified layer. Therefore, the presence of the solidified layer does not hinder the relative sliding of the first inner tube and the second inner tube in the fitting area, thereby eliminating the risk of the device "seizing up" or jamming due to the solidification of the medium. Furthermore, when thermal expansion causes axial sliding and leads to local shear failure of the original solidified layer, a small amount of newly flowing high-temperature medium in the gap will rapidly cool and solidify again using the temperature gradient, thereby re-establishing the sealing balance and enabling the device to exhibit excellent dynamic self-healing capability.

[0093] It should be noted that this dynamic sealing mechanism, achieved through the cooling and property changes of the medium itself, requires no additional sealing elements or materials. Therefore, it avoids the failure issues of sealing materials such as aging, ablation, and melting at high temperatures, fundamentally improving the reliability and durability of the sealing system. More importantly, this self-sealing effect has negative feedback regulation characteristics: when leakage increases, more high-temperature medium enters the gap, bringing more heat. However, as the flow path lengthens, the cooling effect gradually strengthens, the viscosity increase effect gradually becomes apparent, and the self-sealing effect automatically strengthens, causing the leakage to tend to decrease. Conversely, when leakage decreases, less heat enters the gap, the cooling effect is stronger, the self-sealing effect is better, and leakage is further suppressed. This self-regulating mechanism allows the system to automatically stabilize at a low-leakage dynamic equilibrium point, achieving the goal of controlled microleakage. "Controlled microleakage" refers to not pursuing absolute zero leakage, but rather controlling the leakage within a very small, safe, and acceptable range through reasonable design, typically on the order of milliliters per second or lower.

[0094] IV. Guiding Support Structure Optionally, in order to ensure that the relative axial sliding process between the first inner tube and the second inner tube in the sleeve area 23 is smooth and reliable, and to maintain the circumferential uniformity of the fitting gap 4, this application may further include a guide support mechanism (not shown in the figure), which is disposed in the sleeve area 23.

[0095] The guiding support mechanism includes a guide wear-resistant ring and / or a limiting structure. The guide wear-resistant ring is used to constrain the radial displacement of the inner tube assembly 2 and prevent jamming. Specifically, the guide wear-resistant ring is usually set on the outer surface of the first inner tube or the second inner tube, forming radial support with the corresponding inner surface of the inner tube. The guide wear-resistant ring is made of high-temperature resistant and wear-resistant materials, such as ceramic materials, graphite materials, or metal materials with a surface coated with solid lubricant. The function of the guide wear-resistant ring is to ensure that the fit clearance 4 between the first inner tube and the second inner tube remains uniform in the circumferential direction, avoiding problems such as excessively large local clearances (which would cause a surge in leakage) or excessively small local clearances (which may cause jamming) due to radial offset; at the same time, the guide wear-resistant ring can also reduce the frictional resistance during axial sliding, ensuring smooth axial displacement and preventing jamming or wear caused by excessive frictional resistance.

[0096] The limiting structure is used to restrict the maximum axial displacement of the inner tube assembly 2. The limiting structure typically takes the form of a mechanical stop, such as a stop or retaining ring at the end of the first or second inner tube. The function of the limiting structure is to prevent the first and second inner tubes from completely separating under extreme operating conditions or in case of misoperation, providing a final safety guarantee. The design of the limiting structure needs to consider the axial displacement of the device under maximum thermal expansion, ensuring that the limiting structure does not hinder axial sliding under normal operating conditions, and only plays a limiting role when the displacement exceeds the design range.

[0097] In some implementations, such as Figure 2 and Figure 3 As shown, the guide wear-resistant ring can be disposed at the end of the first inner tube in the form of a spherical guide head 26. The spherical guide head 26 has a spherical or arc transition shape, and its function is to provide guidance during the insertion of the first inner tube into the second inner tube, so that the two inner tubes can be smoothly aligned and maintain a coaxial configuration. The spherical design of the spherical guide head 26 can effectively reduce frictional resistance and collisions during the insertion process, and avoid local stress concentration or surface damage caused by misalignment. Under high temperature conditions, the spherical guide head 26 can also compensate for small radial displacement deviations caused by thermal expansion, and maintain the circumferential uniformity of the fit gap 4 between the first inner tube and the second inner tube through the self-adaptability of the spherical contact.

[0098] When the spherical guide head 26 works in conjunction with the multi-stage labyrinth seal structure, it produces beneficial technical effects. On the one hand, by ensuring the circumferential uniformity of the mating gap 4, the spherical guide head 26 enables each stage of the multi-stage labyrinth seal structure to perform its sealing function uniformly and effectively under the designed gap conditions, avoiding the risk of a surge in leakage due to excessively large local gaps or the risk of jamming due to excessively small local gaps. On the other hand, the low-friction characteristics of the spherical guide head 26 reduce the frictional resistance during axial sliding, ensuring that the first inner tube and the second inner tube can smoothly perform relative axial displacement to release thermal stress, while not affecting the temperature gradient field in the mating gap 4 region due to frictional heat generation, thereby ensuring the effective performance of the dynamic self-sealing mechanism.

[0099] The spherical guide head 26 can be integrally machined from the same material as the first inner tube, or it can be made from a more wear-resistant material (such as ceramic material or surface-strengthened alloy material) and then installed at the end of the first inner tube. In terms of manufacturing process, the spherical surface of the spherical guide head 26 needs to be precisely machined to ensure surface roughness and shape accuracy, thereby achieving good guiding effect and low friction performance.

[0100] Through the configuration of the guide support mechanism, each stage of the multi-stage labyrinth seal structure can perform a uniform and effective sealing function under the designed gap conditions, thereby ensuring the stable and reliable sealing performance of the entire device.

[0101] V. Leakage Monitoring System Optionally, in order to achieve real-time monitoring of the sealing status of the device and early warning of faults, this application may also include a leakage monitoring system configured to assess the integrity status of the outer tube 1 as a pressure boundary by monitoring pressure and / or temperature changes outside the outer tube 1.

[0102] Leakage monitoring systems typically include pressure sensors, temperature sensors, data acquisition devices, and alarm devices. In the double-walled structure of this device, the annular space 3 between the inner tube assembly 2 and the outer tube 1 is also filled with a high-temperature medium (e.g., molten salt at approximately 700°C on the inner side and 650°C on the outer side). The fitting gap 4 allows the medium to slowly leak from the inner tube into the annular space 3, but the outer tube 1 acts as a pressure boundary, providing final sealing protection. The monitoring system is located outside the outer tube 1. When the outer tube 1 suffers severe damage such as rupture, the monitoring system can promptly detect the abnormality and issue an alarm.

[0103] The data acquisition device continuously collects sensor signals and compares them with preset thresholds. These preset thresholds are determined based on baseline pressure and temperature during normal operation, combined with a safety margin. Once the pressure or temperature exceeds the safety threshold, the alarm device immediately sounds an alarm, alerting the operator to take appropriate action.

[0104] Through a leak monitoring system, the device transforms from a passive sealing structure into an intelligent system with self-diagnostic capabilities. Based on monitoring data, operators can promptly understand the integrity of the external pipe pressure boundary and intervene in the early stages of abnormal situations, preventing minor problems from escalating into serious accidents. Furthermore, the long-term accumulated monitoring data can be used to analyze the device's operating status and wear trends, providing a basis for predictive maintenance and significantly improving the system's safety and reliability.

[0105] VI. Work Process and Technical Results When the device is put into operation, the high-temperature medium is transported through a continuous internal channel. During the system heating process, the inner tube assembly 2 undergoes significant axial thermal expansion. Since the first inner tube and the second inner tube are connected by a sleeve, they can slide freely relative to each other axially within the sleeve area 23, and the stress generated by thermal expansion is completely released, preventing the generation of harmful thermal stress in the pipeline.

[0106] During stable operation, a small amount of high-temperature medium may leak through the fitting gap 4. However, due to the multi-stage labyrinthine seal structure formed by the fitting gap 4, the leaking medium must traverse a tortuous flow path. In this process, the medium undergoes multiple turns, expansions, contractions, and throttling, resulting in reduced flow velocity, pressure drops, and energy dissipation. Simultaneously, due to its distance from the heat source and proximity to the relatively low-temperature annular space 3, the medium temperature gradually decreases, and its viscosity significantly increases. For some media with high freezing points, partial solidification may occur, forming a self-sealing plug. Through the combined effects of geometric resistance, physical property resistance, and phase change resistance, the leakage is strictly limited to a controlled, minute leakage level.

[0107] Especially under high-pressure conditions where the continuous internal channel operates at high pressure (e.g., close to 10 MPa), the sealing performance of the device mainly relies on the mechanical strength of the high-viscosity medium layer or the solid self-sealing plug formed in the mating gap 4 to resist the huge internal and external pressure difference. Under this condition, the multi-stage labyrinth seal structure plays a key "step-by-step pressure reduction" role. It effectively limits the flow rate in the initial leakage stage before the medium has completely solidified, preventing the high-pressure medium from generating high-speed jets, thus providing the necessary residence time for the medium to cool down and undergo phase change blockage. Once the solid self-sealing plug is formed, the mechanical interlocking force formed between it and the multi-stage mating structure (especially the serrated or grooved structure) is sufficient to withstand the high pressure difference, thereby ensuring a reliable high-pressure seal.

[0108] The guiding support mechanism ensures the circumferential uniformity of the fit clearance 4 between the first and second inner tubes, enabling each stage of the multi-stage sealing structure to function evenly and effectively. The leakage monitoring system monitors the sealing status in real time, promptly detecting abnormalities and issuing alarms.

[0109] It is important to note that the various technical features of this application are not isolated but rather work together synergistically. The interlocking structure provides the basis for thermal expansion compensation, the multi-stage labyrinth seal structure creates flow resistance, the temperature gradient field triggers a dynamic self-sealing mechanism, the guide support mechanism ensures structural stability, and the leakage monitoring system enables intelligent diagnosis. The organic combination of these technologies enables the device to achieve reliable sealing under extreme high temperatures and large temperature differences. More importantly, these technical features exhibit a positive synergistic enhancement effect: the multi-stage labyrinth structure extends the flow path, providing sufficient length for the establishment of the temperature gradient; the temperature gradient-triggered dynamic self-sealing further reduces leakage, alleviating the burden on the multi-stage structure; and the guide support mechanism ensures gap uniformity, guaranteeing the effectiveness of the multi-stage structure and dynamic sealing. This systematic integration and synergistic cooperation of multiple technologies is the fundamental reason why this application can simultaneously achieve ideal results in terms of high temperature, large displacement, and tight sealing.

[0110] In summary, this application integrates and coordinates various technical means such as socket structure, multi-stage labyrinth seal, dynamic self-sealing, guide support, and condition monitoring to construct a high-temperature fluid transport sealing system that allows for significant thermal expansion compensation in structure, relies on media self-sealing rather than external sealing elements in sealing mechanism, achieves predictable and controlled micro-leakage in leakage control, eliminates vulnerable parts and moving parts in reliability, and reduces maintenance costs and extends service life in terms of economy.

[0111] Compared to traditional bellows compensators, the device in this application does not possess the stress concentration and fatigue-sensitive structural features of thin-walled bellows, thus exhibiting higher reliability and a longer service life under long-term high-temperature operation. The average service life of traditional bellows compensators at high temperatures is often no more than two years, while the device in this application, by eliminating fatigue-sensitive structures, can extend its service life several times over. Compared to traditional stuffing box seals, the device in this application does not require stuffing material, avoiding the problems of stuffing oxidation, carbonization, or burn-out at high temperatures, and also avoiding frictional wear between the stuffing and sliding surfaces, thereby achieving a maintenance-free or low-maintenance operation mode.

[0112] VII. Application Scenarios The socket-type double-layer pipe expansion sealing device of this application has broad application potential and can be applied to high-temperature fluid transportation systems such as molten salt reactor nuclear energy systems and energy storage systems.

[0113] In high-temperature nuclear energy systems, molten salt serves as a heat transfer medium, transferring heat from the reactor core to the power generation system via a piping system to achieve thermal energy utilization. The device described in this application reliably addresses thermal expansion and sealing issues during molten salt transport, ensuring the safe and stable operation of the nuclear energy system. Especially in advanced nuclear energy systems like high-temperature molten salt reactors, where the operating temperature of the molten salt is typically between 600°C and 800°C, and the piping system needs to withstand frequent start-ups, shutdowns, and temperature cycles, the high reliability and long lifespan of the device described in this application can significantly reduce system maintenance costs and downtime risks.

[0114] In energy storage systems, novel thermal storage systems utilize molten salt as the heat storage medium. During the day, it absorbs solar energy to heat to high temperatures, and at night, it releases heat to generate electricity. The molten salt needs to be repeatedly transported between the storage tank and the heat exchanger. The device described in this application can adapt to the frequent thermal cycling conditions in energy storage systems, providing long-term reliable sealing performance. In solar thermal power plants, the thermal storage system undergoes heating-insulation-heat release cycles daily, accumulating to hundreds of thermal cycles per year. The device in this application, with its design free of vulnerable parts, can withstand such high-frequency thermal cycling without failure.

[0115] Application Examples For example, in a molten salt reactor nuclear energy system, molten fluoride salt with an operating temperature of approximately 700°C needs to be transported. The pipeline is relatively long, and there is a significant temperature difference between the ambient temperature and the operating temperature. The socket-type double-layer pipeline expansion and sealing device of this application is used, with the following specific configuration: Both the outer tube 1 and the inner tube assembly 2 are made of nickel-based alloys to ensure reliability in high-temperature and corrosive environments. The radial clearance 4 is set within a small range to provide a good seal. The multi-stage labyrinth seal structure employs several stages of sealing, each stage including a combination of annular grooves and annular bosses, forming an effective tortuous flow path. The axial overlap length of the fitting area 23 is rationally determined based on thermal expansion and safety factor requirements to ensure effective fitting even under maximum thermal expansion. A guide support mechanism is configured to ensure smooth axial sliding and uniform clearance, while a leakage monitoring system is installed to monitor the sealing status in real time.

[0116] The device performed well in actual operation, successfully coping with significant thermal expansion, keeping leakage within a safe range, and its service life significantly exceeded that of traditional bellows compensators, providing a reliable guarantee for the safe and stable operation of nuclear energy systems.

[0117] VIII. Optimal Design Criteria In a preferred embodiment, to more accurately control the design parameters of the device and ensure its reliability under various operating conditions, the following quantitative design principles can be adopted. It should be noted that these design principles are intended to provide more precise design guidance, making the device design more scientific and systematic, but are not essential technical features of this application.

[0118] The overlap length L of the socket area 23 along the axial direction needs to meet a certain relationship to ensure that the first inner tube and the second inner tube remain effectively connected under the maximum thermal expansion state, while ensuring the integrity of the sealing structure.

[0119] Thermal expansion compensation requirements First, the overlap length L is related to the maximum axial thermal expansion of the device under the design temperature difference. The following basic relationships should be satisfied between them: (Formula 1) Where L is the overlap length of the socket region 23 along the axial direction. Let K be the maximum axial thermal expansion of the device under the design temperature difference, and K be the safety factor. .

[0120] In Formula 1, It can be calculated in the following ways: ,in is the coefficient of linear expansion of the material. The effective length of the pipe, The safety factor K is introduced to account for factors such as the uncertainty in thermal expansion calculations, fluctuations in material properties, and non-uniformity of temperature distribution. In practical applications, the safety factor K can be set from 1.2 to 2.0. Smaller safety factors (such as 1.2 to 1.5) are suitable for applications where thermal expansion calculations are accurate, material properties are stable, and temperature control is precise; larger safety factors (such as 1.5 to 2.0) are suitable for applications with greater uncertainty or extremely high safety requirements, such as nuclear energy systems or other critical applications.

[0121] Formula 1 ensures that the first inner tube and the second inner tube remain effectively connected and will not completely detach under maximum thermal expansion conditions. However, merely meeting the thermal expansion compensation requirements is insufficient; the integrity of the multi-stage sealing structure must also be ensured.

[0122] 2. Requirements for the integrity of the sealing structure Furthermore, in addition to satisfying thermal expansion compensation, the axial overlap length L of the sleeve region 23 also needs to ensure the integrity of the sealing structure. Therefore, a more comprehensive design principle can be adopted: (Formula 2) in: This represents the maximum axial thermal expansion of the device under the design temperature difference. n is the number of sealing stages in a multi-stage structure, i.e., the number of sealing stages connected in series; It is the minimum effective length of a single-stage sealing section, that is, the minimum length occupied by each stage of the labyrinth seal structure in the axial direction. For thermal expansion safety factor, and Its function is similar to that of K in Formula 1; The structural integrity coefficient is, and This coefficient is used to ensure the integrity of the sealing structure during thermal expansion.

[0123] The physical meaning of Formula 2 is that the overlap length L must include at least two parts. The first part... To meet thermal expansion compensation requirements and ensure sufficient sleeve length even under maximum thermal expansion conditions; Part Two This design ensures sufficient sealing stages and effective length per stage to meet the requirements of sealing structure integrity, under any thermal expansion conditions. This dual constraint guarantees both thermal expansion compensation and sealing functionality, preventing interference between the two functional requirements.

[0124] Minimum effective length of a single-stage sealing section It depends on the specific form of the multi-stage mating structure. For annular grooves or annular boss structures, This typically includes the axial width of the groove or boss and the spacing between adjacent structures; for sawtooth or spiral groove structures, Typically, it is the axial length of a complete serration or a single pitch. In practical design, a reasonable [measurement] can be determined based on factors such as the specific multi-stage fit structure, the number of sealing levels, and sealing performance requirements. value.

[0125] Application of design principles By employing the aforementioned quantitative design criteria, the axial overlap length L of the sleeve region 23 can be systematically determined, ensuring that the device provides reliable sealing performance while fulfilling its thermal expansion compensation function. This formula-based design method provides clear design guidance for the engineering application of the device, improving the scientific rigor and reliability of the design.

[0126] For example, suppose in a certain application scenario, the maximum axial thermal expansion is calculated based on the pipe length, operating temperature difference, and material properties. For a given value, a 4-stage sealing structure (n = 4) is designed, with the minimum effective length of each sealing stage being... Determined based on specific geometric design. The thermal expansion safety factor is taken. The structural integrity coefficient is 1.5. The value is 1.1. Therefore, the minimum required overlap length L can be calculated using Formula 2. In actual design, the overlap length L should not be less than the calculated value, and an appropriate design margin should be allowed.

[0127] It should be noted that Formulas 1 and 2 above provide design guidelines. In practical applications, designers can adjust the parameters and coefficients in the formulas appropriately based on specific operating conditions, material properties, safety requirements, and other factors to obtain the optimal design solution. For example, for operating conditions with particularly large temperature differences, the parameters can be appropriately increased. The value of ; for space-constrained situations, the value can be reduced by optimizing the geometry of the sealing structure. This reduces the total overlap length while maintaining performance. This design flexibility allows the device of this application to adapt to a variety of different application requirements.

[0128] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0129] It should be noted that in this patent application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this patent application, if it refers to performing an action according to an element, it means performing the action at least according to that element, including two cases: performing the action only according to that element, and performing the action according to that element and other elements. Expressions such as "multiple," "repeatedly," and "various" include two, two times, two kinds, and more than two, more than two times, and more than two kinds.

[0130] All documents mentioned in this application are considered to be incorporated in their entirety into the disclosure of this application so that they can serve as a basis for modifications if necessary. Furthermore, it should be understood that after reading the foregoing disclosure of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the scope of protection claimed in this application.

Claims

1. A socket-type double-layer pipe expansion sealing device, characterized in that, include: An outer tube; an inner tube assembly, coaxially disposed inside the outer tube and forming an annular space between them; the inner tube assembly includes a first inner tube and a second inner tube, which are axially connected by a sleeve to form a continuous internal channel for conveying a high-temperature medium; the first inner tube and the second inner tube form a fitting gap in the sleeve area that allows relative axial sliding, the fitting gap forming a multi-stage structure to extend the leakage path, the multi-stage structure being configured to form a tortuous flow path, so that the high-temperature medium entering the fitting gap can utilize the temperature gradient formed by the annular space to generate cooling, viscosity increase and / or phase change to achieve dynamic sealing, thereby limiting the leakage of the high-temperature medium while allowing axial thermal expansion compensation between the first inner tube and the second inner tube.

2. The apparatus according to claim 1, characterized in that, The flow velocity in the annular space between the outer tube and the inner tube assembly is relatively slow, forming a heat insulation space to reduce heat transfer from the inner tube assembly to the outer tube.

3. The apparatus according to claim 1, characterized in that, The multi-level structure provides a multi-level mating structure in the sleeve area, and the multi-level mating structure includes at least one of a stepped surface, an annular groove, an annular boss, a sawtooth groove, or a spiral groove.

4. The apparatus according to claim 1, characterized in that, The tortuous flow path achieves dynamic sealing through cooling, viscosity increase, and / or phase change of the high-temperature medium to obtain controlled micro-leakage.

5. The apparatus according to claim 1, characterized in that, Both the outer tube and the inner tube assembly are made of nickel-based alloy, cobalt-based alloy, or high-temperature stainless steel; wherein at least a portion of the surface of the outer tube or the inner tube assembly is provided with a coating, the coating being made of diamond-like carbon or an inorganic material.

6. The apparatus according to claim 1, characterized in that, It also includes a guide support mechanism disposed in the sleeve area. The guide support mechanism includes a guide wear-resistant ring and / or a limiting structure. The guide wear-resistant ring is used to constrain the radial displacement of the inner tube assembly and prevent jamming. The limiting structure is used to limit the maximum axial displacement of the inner tube assembly.

7. The apparatus according to claim 1, characterized in that, The relative axial displacement between the first inner tube and the second inner tube is 5 mm to 200 mm.

8. The apparatus according to claim 1, characterized in that, The device is suitable for conveying high-temperature media with a temperature range of 400°C to 1000°C; the high-temperature media is at least one of molten metal, molten salt, molten silicate, or high-temperature slag.

9. The application of the device according to claim 1 in a high-temperature fluid transport system, wherein the high-temperature fluid transport system is selected from a molten salt reactor nuclear energy system or an energy storage system.

10. The apparatus according to claim 6, characterized in that, The guide wear-resistant ring includes a spherical guide head disposed at the end of the first inner tube, the spherical guide head being configured to provide guidance and reduce insertion resistance when the first inner tube is inserted into the second inner tube.

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