Radial heat pipe for low temperature superheater and economizer assemblies

Abstract

The utility model relates to the technical field of flue gas acid making and industrial waste heat recovery, specifically relates to a radial heat pipe for low temperature superheater and coal economizer assembly, including inner tube, outer tube and connecting disc, the connecting disc is equipped as two, and is fixed respectively and is equipped in two ends of inner tube, the outer tube is coaxially equipped in the outer of inner tube, and its both ends are sealed connection with two connecting disc respectively, the inner wall of outer tube, the outer wall of inner tube and two connecting disc form a closed annular cavity together, the annular cavity is filled with working medium, the outer peripheral wall of outer tube is equipped with fin. Therefore, can guarantee radial heat pipe high -efficient heat transfer, can fundamentally improve its connection mode, eliminate the leakage hidden danger of thermal stress and reduce the installation complexity.

Description

Technical Field

[0001] This utility model relates to the field of flue gas acid production and industrial waste heat recovery technology, specifically a radial heat pipe for use in low-temperature superheaters and economizer components. Background Technology

[0002] Flue gas-fired acid production systems contain a significant amount of low- and medium-temperature waste heat. Effectively recovering this waste heat is crucial for improving overall energy efficiency and reducing production costs. Low-temperature superheaters and economizers are key waste heat recovery devices at the end of the system, and their performance directly impacts steam output and system energy consumption. Heat pipe technology, due to its extremely high thermal conductivity, excellent isothermal characteristics, and the fact that it requires no external power drive, is widely used as the heat transfer element in these devices. Radial heat pipes with a double-tube structure are particularly common. The inner tube, acting as the evaporation section, is placed within the flue gas channel, while the outer tube, acting as the condensation section, is placed in water or steam as the working fluid. Efficient heat transfer is achieved through the phase change cycle of the internal working medium. This structural design also isolates the pressure-bearing body from the corrosive environment, ensuring high safety.

[0003] However, existing radial heat pipe double-tube structures have significant drawbacks in practical engineering applications. First, their integration with cryogenic superheaters and economizer components involves complex connection processes and high construction difficulty. This is because double-tube structures typically require separate handling of two sets of interfaces on the flue gas side and the working fluid side. Under conditions of limited internal space and dense tube arrays, the requirements for alignment accuracy and welding processes are extremely stringent, significantly increasing installation costs and time.

[0004] A more prominent problem is the high risk of leakage during operation. Fundamentally, the significant temperature difference between the evaporator and condenser sections of the heat pipe during operation causes uneven thermal expansion of the inner and outer casings. This expansion difference creates alternating thermal stress at the rigid connections (such as welds or flanges). After repeated start-stop cycles, this easily leads to thermal fatigue of the materials, eventually causing cracks at stress concentration points and sealing failure, resulting in leakage of the working medium and ultimately, complete heat pipe failure. Furthermore, factors such as acidic corrosion from flue gas and environmental vibration further exacerbate the possibility of leakage. Once a leak occurs, not only does the heat pipe itself lose its heat transfer function, but it also requires shutdown for maintenance, severely impacting the continuity and economic efficiency of production.

[0005] Therefore, it is necessary to optimize and improve the current heat pipe structure so as to ensure efficient heat transfer of radial heat pipes, fundamentally improve its connection method, eliminate the leakage risks caused by thermal stress, and reduce installation complexity. Utility Model Content

[0006] The purpose of this invention is to provide a radial heat pipe for low-temperature superheaters and economizer components, so as to fundamentally improve its connection method, eliminate the leakage risk caused by thermal stress, and reduce the installation complexity while ensuring the high efficiency of radial heat pipe heat transfer.

[0007] To achieve the above objectives, this utility model provides the following technical solution:

[0008] A radial heat pipe for use in low-temperature superheaters and economizer assemblies includes an inner tube, an outer tube, and two receiving plates, each fixedly sleeved at both ends of the inner tube. The outer tube is coaxially sleeved outside the inner tube, and its two ends are respectively sealed to the two receiving plates. The inner wall of the outer tube, the outer wall of the inner tube, and the two receiving plates together form a closed annular cavity. The annular cavity is filled with a working medium. Fins are provided on the outer peripheral wall of the outer tube.

[0009] Alternatively, the inner tube is made of a high-temperature corrosion resistant metal material, and the outer tube and the connector are made of a metal material with good thermal conductivity.

[0010] Alternatively, the inner tube may be made of stainless steel or duplex stainless steel; the outer tube and the connecting plate may be made of low-carbon steel.

[0011] Alternatively, the connecting plate is fixedly connected to the inner tube by a first weld; the connecting plate is sealed to the outer tube by a second weld.

[0012] Alternatively, the first weld is a full penetration groove weld, and the second weld is a fillet weld.

[0013] Optionally, an annular groove is provided on the end face of the receiving plate that connects with the outer tube, and an elastic sealing ring is provided in the annular groove.

[0014] Optionally, a heat insulation gap is provided between the fins and the receiving plate.

[0015] Alternatively, the fins may be multiple and spirally wound around the outer tube.

[0016] Alternatively, the spacing between adjacent fins may be 6-10 mm.

[0017] Optionally, the inner tube has a diameter of D1 and the outer tube has a diameter of D2, satisfying that D2 ≥ 3D1.

[0018] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0019] Through the above technical solution, the finned structure on the outer periphery of the outer tube improves heat transfer performance by expanding the heat transfer area and enhancing fluid turbulence. Welding the fins to the outer tube reduces heat transfer loss while ensuring connection strength. Simultaneously, the closed structure of the annular cavity ensures the stability of the working medium's phase change environment. Utilizing the isothermal characteristics of the working fluid's phase change, it avoids temperature gradient losses associated with traditional metal heat conduction, making it particularly suitable for low-temperature superheaters and economizers in medium- and low-temperature waste heat recovery scenarios.

[0020] Two standardized connectors can be pre-welded and positioned to the tube sheet of the low-temperature superheater or economizer. During on-site installation, only the heat pipe body needs to be inserted into the connector and tightened for sealing, eliminating the need to separately address the alignment issues of the dual connectors on the flue gas side and the working fluid side. This modular structure shortens the heat pipe installation time, thereby reducing the requirements for construction space and precision. Simultaneously, the coaxial design ensures the concentricity of the inner and outer tubes through precision machining, avoiding installation interference in densely packed tube areas and reducing rework costs caused by construction errors.

[0021] By adjusting the type of working medium (such as acetone, ammonia, etc.) and fin parameters, this heat pipe can operate stably in a temperature range of -50℃ to 300℃, meeting the differentiated waste heat recovery needs of low-temperature superheaters and economizers. In corrosive environments such as sulfur-containing flue gas, the corrosion-resistant design of the outer tube and the isolation effect of the sealing structure can ensure that the outlet flue gas temperature is controlled above the dew point, effectively preventing acid dew corrosion. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the exemplary embodiments of this utility model, the drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this utility model and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0023] Figure 1 A schematic diagram of the structure of the radial heat pipe for a low-temperature superheater and economizer assembly provided by this utility model in one embodiment;

[0024] Figure 2 A schematic diagram of the cross-sectional structure of the radial heat pipe for low-temperature superheater and economizer assembly provided by this utility model in one embodiment.

[0025] The attached diagram shows the markings and corresponding component names: 1-inner tube, 2-outer tube, 3-connecting plate, 4-fins. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be noted that while the description of these embodiments is intended to aid in understanding the present invention, it does not constitute a limitation thereof. The specific structural and functional details disclosed herein are only for describing exemplary embodiments of the present invention. However, the present invention may be embodied in many alternative forms and should not be construed as being limited to the embodiments described herein.

[0027] According to specific embodiments of this disclosure, a radial heat pipe is provided for use in low-temperature superheaters and economizer assemblies. Wherein, Figure 1 and Figure 2 Specific embodiments thereof are shown.

[0028] See Figure 1 and Figure 2 As shown, the radial heat pipe for the low-temperature superheater and economizer assembly includes an inner tube 1, an outer tube 2, and two receiving plates 3, which are respectively fixedly sleeved on both ends of the inner tube 1. The outer tube 2 is coaxially sleeved on the outside of the inner tube 1, and its two ends are respectively sealed to the two receiving plates 3. The inner wall of the outer tube 2, the outer wall of the inner tube 1, and the two receiving plates 3 together form a closed annular cavity. The annular cavity is filled with a working medium. Fins 4 are provided on the outer peripheral wall of the outer tube 2.

[0029] This radial heat pipe achieves efficient recovery of waste heat from flue gas through the principle of phase change heat transfer. Its working process mainly consists of three continuous stages: heat absorption, heat transfer, and heat release. The inner tube 1, acting as the evaporation section, is directly placed in the flue gas channel. When high-temperature flue gas flows through the surface of the inner tube 1, heat is conducted through the tube wall to the closed annular cavity. The working medium (such as distilled water or a dedicated heat transfer medium) filled in the cavity rapidly absorbs heat and vaporizes under low pressure, forming saturated steam. Due to the coaxial design of the inner tube 1 and outer tube 2, the steam diffuses radially and uniformly to the inner wall of the outer tube 2 under the action of pressure difference. The outer tube 2, acting as the condensation section, has fins 4 on its outer peripheral wall that significantly expand the heat exchange area. When cooling water or the working medium to be heated flows through the surface of the fins 4, the steam releases a large amount of latent heat and condenses into a liquid working medium. The condensed liquid flows back to the evaporation section along the outer wall of the inner tube 1 under the action of gravity and capillary force, completing a closed loop and continuously transferring the waste heat from the flue gas to the target working medium.

[0030] Through the above technical solution, the fin structure 4 on the outer periphery of the outer tube 2 improves heat transfer performance through a dual structure of expanding the heat transfer area and enhancing fluid turbulence. The fins 4 are welded to the outer tube 2, reducing heat transfer loss while ensuring connection strength. Simultaneously, the closed structure of the annular cavity ensures the stability of the phase change environment of the working medium. Utilizing the isothermal characteristics of the working fluid's phase change, it avoids temperature gradient losses associated with traditional metal heat conduction, making it particularly suitable for medium- and low-temperature waste heat recovery scenarios in low-temperature superheaters and economizers.

[0031] Two connectors 3 serve as standardized interfaces, pre-positioned by welding to the tube sheet of the low-temperature superheater or economizer. During on-site installation, only the heat pipe body needs to be inserted into the interface and tightened for sealing, eliminating the need to separately address the alignment issues of the dual interfaces on the flue gas side and the working fluid side. This modular structure shortens the heat pipe installation time, thereby reducing the requirements for construction space and precision. Simultaneously, the coaxial design, through precision machining, ensures the concentricity of the inner tube 1 and the outer tube 2, avoiding installation interference in densely packed tube areas and reducing rework costs caused by construction errors.

[0032] By adjusting the working medium type (such as acetone, ammonia, etc.) and fin parameters 4, this heat pipe can operate stably in a temperature range of -50℃ to 300℃, meeting the differentiated waste heat recovery needs of low-temperature superheaters and economizers. In corrosive environments such as sulfur-containing flue gas, the corrosion-resistant design of the outer tube 2 and the isolation effect of the sealing structure can ensure that the outlet flue gas temperature is controlled above the dew point, effectively preventing acid dew corrosion.

[0033] It should be noted that the directional terms used, such as "inner" and "outer," refer to "inner" and "outer" relative to the outline of the component. "Inner" refers to the direction towards the inside of the component, and "outer" refers to the direction away from it. Furthermore, it should be noted that the terms used, such as "first" and "second," are used to distinguish one element from another and do not indicate sequence or importance. Moreover, in the following descriptions with accompanying drawings, the same reference numerals in different drawings represent the same element.

[0034] In this disclosure, the inner tube 1 is made of a high-temperature corrosion resistant metal material, and the outer tube 2 and the receiving plate 3 are made of a metal material with good thermal conductivity.

[0035] The inner tube 1 is made of high-temperature corrosion-resistant metal materials (such as 310S stainless steel or Inconel 617 nickel-based alloy) to specifically withstand the harsh operating conditions on the flue gas side. In flue gas acid production systems, the flue gas temperature of the low-temperature superheater and economizer is typically 200-450℃, and contains... Despite the presence of corrosive components, 310S stainless steel, with its 24-26% chromium and 19-22% nickel content, can form a dense surface layer. The passivation layer effectively prevents acidic media from corroding the pipe wall; and Inconel 617 alloy can still form a protective layer after 500 hours of corrosion testing at 750℃. The oxide layer significantly slows down the rates of sulfide corrosion and oxidative corrosion. This material selection fundamentally solves the problems of tube wall thinning, perforation, and leakage caused by high-temperature corrosion of the inner tube 1 in traditional structures, extending the service life of the heat pipe, while ensuring that the evaporation section maintains structural integrity and the sealing performance of the annular cavity during long-term operation.

[0036] The outer tube 2 and the connecting plate 3 are made of metals with good thermal conductivity (such as medium carbon steel or oxygen-free copper), which maximizes heat transfer efficiency and can quickly conduct the latent heat released by the working fluid in the annular cavity to the surface of the outer tube 2. The efficient heat conduction of the outer tube 2 and the fins 4 reduces the thermal resistance of heat transfer from the condensation section to the working fluid. The connecting plate 3, as the connection base between the inner tube 1 and the outer tube 2, ensures continuous heat transfer between different components due to its high thermal conductivity, avoiding localized heat accumulation caused by differences in material thermal resistance in traditional structures. Furthermore, the excellent weldability of carbon steel makes the sealing connection between the connecting plate 3 and the outer tube 2 more reliable, reducing the risk of leakage due to welding defects during installation.

[0037] Specifically, the inner tube 1 is made of stainless steel or duplex stainless steel; the outer tube 2 and the connecting plate 3 are both made of low-carbon steel.

[0038] The inner tube 1 is made of stainless steel or duplex stainless steel, specifically designed to withstand the harsh corrosive environment of the flue gas side. Ordinary stainless steel is produced by forming a dense... Passivation layer blocks acidic flue gas (including The corrosion of components such as austenite and ferrite is a concern; duplex stainless steel (such as type 2205) has both austenitic and ferrite phases, which can effectively prevent stress corrosion cracking in acidic media above 60°C. At the same time, the inner tube wall thickness can be reduced to lower thermal resistance, while ensuring structural stability under flue gas pressure fluctuations.

[0039] The outer tube 2 and the receiving plate 3 are made of low carbon steel, which can quickly conduct the latent heat released by the working fluid in the annular cavity to the fins 4 of the outer tube 2. With the expansion of the heat exchange area of ​​the fins 4, the heat transfer coefficient of the condensation section is improved, ensuring that the receiving plate 3 and the outer tube 2 form a dense and sealed connection. After welding, no complicated heat treatment is required to meet the strength requirements, which greatly reduces the difficulty of the welding process and the risk of leakage.

[0040] In one embodiment provided in this disclosure, the receiving plate 3 is fixedly connected to the inner tube 1 by a first weld; the receiving plate 3 is sealed to the outer tube 2 by a second weld.

[0041] The first weld forms a rigid connection between the receiving plate 3 and the inner tube 1. Using specialized welding materials such as nickel-based welding rods effectively inhibits intergranular corrosion caused by carbon migration. The weld has high strength, which helps prevent radial displacement of the inner tube 1 under the impact of flue gas turbulence, maintaining the uniformity of the annular cavity and avoiding obstructed flow of the working fluid due to eccentricity. The second weld seals the connection between the outer tube 2 and the receiving plate 3. Utilizing the excellent weldability of low-carbon steel, a multi-layer welding process forms a dense weld metal, improving crack resistance.

[0042] The second weld seam adopts a butt joint structure with a shrinkage gap. During welding, the weld seam shrinks to ensure that the outer tube 2 fits snugly against the receiving plate 3, preventing weld beads from overflowing and forming leakage channels. At the same time, a packing platform is set on one side of the receiving plate 3 to assist in weld seam positioning, ensuring that the beam current is accurately applied to the joint during electron beam welding, reducing defects such as porosity and slag inclusions. This allows the annular cavity to remain sealed for a long time under vacuum, effectively preventing leakage of the working medium and intrusion of outside air, and ensuring heat transfer efficiency.

[0043] During operation, the first weld seam utilizes preheating and slow cooling processes to reduce welding stress and prevent cracking of duplex stainless steel due to hardening. The second weld seam leverages the low deformation of low-carbon steel, employing a continuous welding process to reduce the heat-affected zone. Post-weld, no complex heat treatment is required to meet strength requirements, reducing process costs. The inner tube 1 and connecting plate 3 are fixed first, then the outer tube 2 is sealed. Precise control of coaxiality using tooling ensures uniform wall thickness of the annular cavity, eliminating the risk of excessive local thermal resistance. Thus, based on the synergistic effect of the first and second weld seams, not only is the reliability of the connection between different metal materials guaranteed, but the refined sealing structure also eliminates leakage risks, ensuring the service life of the heat pipe under acidic flue gas and thermal cycling conditions.

[0044] Specifically, the first weld is a full penetration groove weld, and the second weld is a fillet weld.

[0045] The first weld uses a full penetration groove weld (groove angle 40°-45°, with a 2-3mm blunt edge), which enables fusion between the inner tube 1 (stainless steel or duplex stainless steel) and the connecting plate 3 (low carbon steel). This ensures the weld completely penetrates the base material thickness, guarantees joint strength, and effectively resists the radial force generated by flue gas turbulence. The second weld uses a fillet weld design, forming a sealing band around the joint between the outer tube 2 and the connecting plate 3 through continuous welding. This can, to some extent, eliminate stress concentration caused by arc defects.

[0046] In one embodiment provided in this disclosure, an annular groove is provided on the end face of the receiving plate 3 that is connected to the outer tube 2, and an elastic sealing ring is provided in the annular groove.

[0047] The second weld tightly connects the connector 3 to the outer pipe 2, achieving a seal for the elastic sealing ring. Under pre-tightening force, the elastic sealing ring undergoes radial deformation, filling the microscopic gaps on the joint end face. When flue gas pressure fluctuations or temperature changes cause minute gaps at the interface, the sealing ring can maintain a continuous sealing pressure based on its high elastic recovery force, avoiding the micro-leakage problem that easily occurs in traditional single-weld seals during thermal cycling. Simultaneously, the groove depth and width design of the annular groove ensures that the sealing ring compression is maintained within a certain range, avoiding material fatigue caused by over-compression and achieving dynamic sealing compensation through elastic potential energy storage.

[0048] Furthermore, the elastic sealing ring is made of acid- and temperature-resistant fluororubber (FKM) or hydrogenated nitrile rubber (HNBR), in the presence of... It can withstand temperature fluctuations from -20℃ to 200℃ in acidic flue gas environments.

[0049] The closed structure of the annular groove completely isolates the sealing ring from the flue gas, allowing it to contact only the clean working medium on both sides of the outer tube, thus avoiding seal failure caused by direct corrosion from the flue gas. Simultaneously, the synergistic effect of the sealing ring and the fillet weld maintains the vacuum level of the annular cavity above -0.1 MPa over a long period, which is beneficial for stable and efficient heat transfer of the working medium, making it particularly suitable for low-temperature superheaters and economizer components.

[0050] In one embodiment provided in this disclosure, a heat insulation gap is provided between the fin 4 and the receiving plate 3.

[0051] The thermal insulation gap cuts off the direct heat conduction from the fins 4 to the receiving plate 3 through physical spatial separation, so that the high temperature zone (heat exchange section of fins 4) and the low temperature sensitive zone (sealing section of receiving plate 3) form a clear thermal boundary. This can avoid the elastic degradation of the sealing ring caused by long-term high temperature aging. At the same time, the low temperature environment significantly slows down the oxidation rate of the weld connecting the receiving plate 3 and the outer tube 2, thereby extending the service life of the sealing structure.

[0052] The insulation gap enables directional heat transfer through thermal resistance control, forcing the heat absorbed by fin 4 to be mainly transferred to the working fluid through the wall of outer tube 2, thereby improving the effective heat exchange area utilization rate of the condensation section, reducing heat loss of the working fluid in non-target areas, and ensuring waste heat recovery efficiency.

[0053] In one embodiment provided in this disclosure, the fins 4 are multiple and spirally wrapped around the outer tube 2, which can greatly increase the contact area between the flue gas or working fluid and the fins 4, forcibly destroy the fluid boundary layer, and improve the heat exchange efficiency.

[0054] Furthermore, the spacing between adjacent fins 4 is 6-10mm. This setting maximizes the heat transfer area per unit length while avoiding thermal boundary layer overlap. Simultaneously, this spacing ensures more uniform contact time between the fins 4 and the working fluid, preventing localized overheating and working fluid degradation, and ensuring long-term stability of phase change heat transfer efficiency.

[0055] In one embodiment provided in this disclosure, the inner tube 1 has a diameter of D1, and the outer tube 2 has a diameter of D2, satisfying that D2 ≥ 3D1. The inner tube 1 serves as the evaporation section, and its diameter D1 is adapted to the space constraints of the flue gas passage. The design of the outer tube 2 with a diameter D2 ≥ 3D1 can significantly expand the basic heat exchange area of ​​the condensation section. With the addition of the spiral fins 4, the total heat exchange area can be significantly increased, improving heat exchange efficiency and helping to stabilize the pressure within the annular cavity, avoiding a decrease in heat transfer efficiency due to steam accumulation.

[0056] In this disclosure, those skilled in the art can flexibly select any suitable working medium from the prior art according to actual needs.

[0057] The above specific embodiments further illustrate the purpose, technical solution and beneficial effects of this utility model. It should be understood that the above are only specific embodiments of this utility model and are not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A radial heat pipe for use in low-temperature superheaters and economizer assemblies, characterized in that, The device includes an inner tube, an outer tube, and two receiving plates, which are respectively fixedly sleeved on both ends of the inner tube. The outer tube is coaxially sleeved on the outside of the inner tube, and its two ends are respectively sealed to the two receiving plates. The inner wall of the outer tube, the outer wall of the inner tube, and the two receiving plates together form a closed annular cavity. The annular cavity is filled with a working medium. Fins are provided on the outer peripheral wall of the outer tube.

2. The radial heat pipe for a low-temperature superheater and economizer assembly according to claim 1, characterized in that, The inner tube is made of a high-temperature corrosion resistant metal material, and the outer tube and the connecting plate are made of a metal material with good thermal conductivity.

3. The radial heat pipe for a low-temperature superheater and economizer assembly according to claim 2, characterized in that, The inner tube is made of stainless steel or duplex stainless steel; the outer tube and the connecting plate are both made of low-carbon steel.

4. The radial heat pipe for a low-temperature superheater and economizer assembly according to claim 1, characterized in that, The receiving plate is fixedly connected to the inner tube by a first weld; the receiving plate is sealed to the outer tube by a second weld.

5. The radial heat pipe for a low-temperature superheater and economizer assembly according to claim 4, characterized in that, The first weld is a full penetration groove weld, and the second weld is a fillet weld.

6. The radial heat pipe for a low-temperature superheater and economizer assembly according to claim 1, characterized in that, An annular groove is provided on the end face of the receiving plate that connects to the outer tube, and an elastic sealing ring is provided in the annular groove.

7. The radial heat pipe for a low-temperature superheater and economizer assembly according to claim 1, characterized in that, A heat insulation gap is provided between the fins and the receiving plate.

8. The radial heat pipe for a low-temperature superheater and economizer assembly according to claim 1, characterized in that, The fins are multiple and spirally wrapped around the outer tube.

9. The radial heat pipe for a low-temperature superheater and economizer assembly according to claim 8, characterized in that, The spacing between adjacent fins is 6-10 mm.

10. The radial heat pipe for a low-temperature superheater and economizer assembly according to claim 1, characterized in that, The inner tube has a diameter of D1, and the outer tube has a diameter of D2, satisfying the condition: D2≥3D1.

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