A new type of double-pipe heat exchanger

Abstract

The application relates to the technical field of heat exchange equipment, in particular to a novel double-pipe heat exchanger. The double-pipe heat exchanger comprises an inner pipe assembly and an outer pipe assembly. The inner pipe assembly is made of stainless steel, has an internally-threaded pipe and two end light pipe sections, forms a first medium channel, and the light pipe sections have a medium inlet and a medium outlet. The outer pipe assembly has an outer pipe and two pipe sleeves, the pipe sleeves are arranged on the outer sides of the two ends of the inner pipe, the outer pipe is connected with the pipe sleeves, the pipe sleeves have a first connecting pipe and a second connecting pipe, and the connecting pipes are connected with the inner pipe to form a second medium channel. The connecting pipes are the medium inlet and the medium outlet. The scheme can reduce the production cost and improve the sealing reliability.

Description

Technical Field

[0001] This application relates to the field of heat exchange equipment technology, and more specifically, to a novel shell-and-tube heat exchanger. Background Technology

[0002] Shell-and-tube heat exchangers, as core components of heat exchange systems, are widely used in industrial fields such as air conditioning, refrigeration, and heat pumps. Traditional designs generally use copper tubes as the inner tube material, relying on their high thermal conductivity and good plastic deformation capacity to achieve efficient heat transfer through the annular flow channel between the inner and outer tubes.

[0003] However, copper prices have been rising steadily in recent years, leading to a significant increase in heat exchanger production costs and putting companies under increasing economic pressure. To alleviate this cost burden, the industry has attempted to replace copper tubes with stainless steel, leveraging its price advantage to reduce raw material expenditures. However, stainless steel's inherent characteristics of high hardness and low ductility present multiple challenges in the processing, especially in the internal thread structure forming stage. Conventional cold rolling or roll forming processes struggle to create uniform and continuous thread features on the stainless steel tube surface, easily resulting in material cracking or thread deformation, severely impacting the strengthening effect of the heat exchange surface.

[0004] Furthermore, during the component assembly stage, when the stainless steel inner tube is combined with the carbon steel outer tube, the difference in the thermal expansion coefficients of the two materials leads to significant residual stress at the welding interface. Conventional fusion welding methods are insufficient to achieve reliable sealing, often resulting in defects such as porosity and incomplete fusion. This not only reduces the safety of equipment operation but may also cause media leakage and shorten the product's service life. These problems collectively restrict the large-scale application of stainless steel shell-and-tube heat exchangers and hinder the industry's balanced development between cost control and performance stability.

[0005] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0006] The purpose of this application is to provide a novel shell-and-tube heat exchanger that has the advantages of reducing production costs and improving sealing reliability.

[0007] This application provides a novel shell-and-tube heat exchanger, the technical solution of which is as follows:

[0008] Includes inner tube assembly and outer tube assembly;

[0009] The inner tube assembly is made of stainless steel and includes an internally threaded tube and smooth tube sections connected to its two ends. A first medium channel is formed inside the inner tube assembly, and the two ends of the smooth tube sections serve as the medium inlet and medium outlet of the first medium channel, respectively.

[0010] The outer tube assembly includes an outer tube and two sleeves. The two sleeves are respectively disposed on the outer sides of both ends of the inner tube assembly. The outer tube is connected between the two sleeves. The sleeves are respectively provided with a first connector and a second connector. The outer ends of the sleeves are connected to the outer wall of the inner tube assembly, thereby forming a second medium channel between the inner and outer tubes. The first connector and the second connector serve as the medium inlet and medium outlet of the second medium channel, respectively.

[0011] Furthermore, this application also proposes that the two ends of the internally threaded pipe are provided with a first sleeve portion, and the two ends of the smooth pipe section are provided with a second sleeve portion. The first sleeve portion and the second sleeve portion are fitted together and then welded and sealed to form an inner pipe assembly.

[0012] Furthermore, this application also proposes that the second sleeve portion extends into the first sleeve portion for welding and sealing, or the first sleeve portion extends into the second sleeve portion for welding and sealing.

[0013] Furthermore, this application also proposes that the end of the first sleeve portion of the internally threaded pipe is located inside the sleeve, the outer end of the sleeve is welded to the outer wall of the plain pipe section, and the weld between the internally threaded pipe and the plain pipe section is located inside the sleeve.

[0014] Furthermore, this application also proposes that the end of the first sleeve portion of the internally threaded pipe extends to the outside of the sleeve, the outer end of the sleeve is welded to the outer wall of the first sleeve portion of the internally threaded pipe, and the weld between the internally threaded pipe and the bare pipe section is located outside the sleeve.

[0015] Furthermore, this application also proposes that the internally threaded tube and the smooth tube section are integrally formed.

[0016] Furthermore, this application also proposes that it includes a welding ring, which is sleeved on the outside of the inner tube assembly, with its inner side connected to the outer wall of the inner tube assembly and its outer side connected to the outer end of the sleeve.

[0017] Furthermore, this application also proposes that it includes a welding ring, wherein the weld between the internally threaded pipe and the bare pipe section is located inside the welding ring and a sealed connection is achieved through the welding ring; the welding ring is sleeved on the outside of the inner pipe assembly, its inner side is welded to the outer wall of the inner pipe assembly, and its outer side is welded to the outer end of the sleeve.

[0018] Furthermore, this application also proposes that the outer tube assembly is made of carbon steel or stainless steel, and the welding ring is made of a material with a melting point not higher than that of the outer tube assembly material.

[0019] Furthermore, this application also proposes that the inner and outer surfaces of the internally threaded tube are provided with fins and / or teeth.

[0020] As can be seen from the above, the novel shell-and-tube heat exchanger provided in this application includes an inner tube assembly and an outer tube assembly. The inner tube assembly is made of stainless steel to form a first medium channel, and the outer tube assembly is connected by a tube sleeve to form a second medium channel. This solves the processing difficulties and welding sealing problems when stainless steel replaces copper tubes, and has the advantages of reducing production costs and improving sealing reliability. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the first embodiment of a novel shell-and-tube heat exchanger provided in this application.

[0022] Figure 2 This is a schematic diagram of a second embodiment of a novel shell-and-tube heat exchanger provided in this application.

[0023] Figure 3 This is a schematic diagram of a third embodiment of a novel shell-and-tube heat exchanger provided in this application. Detailed Implementation

[0024] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. The components of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0025] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this application, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0026] Traditional shell-and-tube heat exchangers typically use copper tubes as the inner tube material, but copper is expensive. To reduce costs, stainless steel tubes have been considered, but their high hardness and poor machinability make it difficult to directly machine the internal thread structure that enhances heat exchange. Furthermore, welding dissimilar materials like stainless steel inner tubes to carbon steel outer tubes results in poor reliability, is prone to defects, and affects service life and safety.

[0027] like Figure 1-3As shown, this application proposes a novel shell-and-tube heat exchanger. The inner tube assembly is made of stainless steel and includes an internally threaded tube 2 and smooth tube sections 3 connected to its two ends. A first medium channel is formed inside the inner tube assembly. The outer tube assembly includes an outer tube 1 and two sleeves 4. The sleeves 4 are located on the outer sides of both ends of the inner tube assembly, and the outer tube 1 is connected between the sleeves 4. A first connecting pipe 5 and a second connecting pipe 6 are provided on the sleeves 4. The outer ends of the sleeves 4 are connected to the outer wall of the inner tube assembly, thereby forming a second medium channel between the inner and outer tubes. The first connecting pipe 5 and the second connecting pipe 6 serve as the medium inlet and outlet of the second medium channel.

[0028] For ease of understanding, the following explains some key terms in this embodiment:

[0029] The inner tube assembly refers to the piping structure inside the heat exchanger used to carry the flow of the first medium. It is made of stainless steel to achieve corrosion resistance and cost control.

[0030] The outer tube assembly refers to the piping structure outside the heat exchanger used to carry the flow of a second medium. It surrounds the inner tube assembly and together with the inner tube assembly forms the heat exchange space.

[0031] The internally threaded tube 2 is the main heat exchange part in the inner tube assembly. Its inner and outer surfaces may be provided with fins and / or teeth to enhance heat transfer efficiency.

[0032] Section 3 is the straight pipe part in the inner pipe assembly that connects the two ends of the internally threaded pipe 2. Its main function is to provide a connection interface and guide the medium in and out.

[0033] The first medium channel refers to the medium flow path formed inside the inner tube assembly, used for the entry, exit, and flow of the first type of medium.

[0034] The outer tube 1 is the main part of the outer tube assembly. It is usually a straight tube and is connected between the two tube sleeves 4 to form part of the second medium channel.

[0035] The sleeve 4 is a connecting component located on the outer side of both ends of the inner tube assembly. It connects the inner tube assembly to the outer tube 1 and provides the inlet and outlet of the second medium channel.

[0036] The first connector 5 and the second connector 6 are interfaces installed on the sleeve 4, used for the introduction and discharge of the second medium, respectively.

[0037] The second medium channel refers to the annular medium flow path formed between the inner tube assembly and the outer tube assembly, which is used for the entry, exit and flow of the second medium, and for heat exchange with the first medium channel.

[0038] This embodiment provides a novel shell-and-tube heat exchanger, whose structural design aims to optimize heat exchange performance and improve manufacturing efficiency.

[0039] Specifically, the heat exchanger includes an inner tube assembly and an outer tube assembly. The inner tube assembly carries one medium, while the outer tube assembly surrounds the inner tube assembly and carries another medium. The two media exchange heat through the tube walls.

[0040] The inner tube assembly is made of stainless steel. Stainless steel is corrosion-resistant and has a cost advantage over copper. The inner tube assembly can be manufactured using standard stainless steel tubing that has been cut and shaped.

[0041] The inner tube assembly further includes an internally threaded tube 2 and smooth tube sections 3 connected to its two ends. The internally threaded tube 2 is the core part of the heat exchange; its internal structure promotes medium turbulence and enhances heat transfer. The smooth tube sections 3 serve as connecting parts, facilitating connection to external piping systems. For example, the internally threaded tube 2 and the smooth tube sections 3 can be connected by direct butt welding to form a continuous inner tube assembly.

[0042] The inner tube assembly forms a first medium channel, with the two ends of the smooth tube segment 3 serving as the medium inlet and outlet of this first medium channel, respectively. The medium enters the inner tube assembly through one end of the smooth tube segment 3, flows through the internally threaded tube 2 for heat exchange, and then flows out from the other end of the smooth tube segment 3.

[0043] The outer tube assembly consists of an outer tube 1 and two tube sleeves 4. The outer tube 1 is the main body of the outer tube assembly and is usually a straight tube, the length of which is determined according to the design requirements of the heat exchanger. The tube sleeves 4 serve as connectors to connect the outer tube 1 to the inner tube assembly.

[0044] Two sleeves 4 are respectively set on the outer sides of both ends of the inner tube assembly. This arrangement allows the inner tube assembly to be completely covered by the outer tube assembly, forming an annular channel.

[0045] The outer tube 1 is connected between the two sleeves 4. The two ends of the outer tube 1 can be connected to the sleeves 4 by welding to form a sealed outer shell structure.

[0046] The sleeve 4 is equipped with a first connecting pipe 5 and a second connecting pipe 6. These connecting pipes are used to connect the external pipeline to the second medium channel, ensuring that the second medium can enter and exit.

[0047] The outer end of the sleeve 4 is connected to the outer wall of the inner tube assembly. For example, the outer end of the sleeve 4 can be directly welded to the outer wall of the smooth tube segment 3 of the inner tube assembly to form a sealed connection; or it can be connected by integral molding.

[0048] This creates a second medium channel between the inner and outer tubes. This channel is annular, and the medium exchanges heat with the inner tube assembly as it flows through it.

[0049] The first connector 5 and the second connector 6 serve as the medium inlet and outlet of the second medium channel, respectively. The second medium enters the second medium channel through the first connector 5, flows through the annular space between the inner and outer pipes, exchanges heat with the first medium in the inner pipe assembly, and then exits through the second connector 6.

[0050] The novel shell-and-tube heat exchanger provided in this embodiment effectively reduces material costs by using stainless steel to manufacture the inner tube assembly. The inner tube assembly consists of an internally threaded tube 2 and a smooth tube section 3, simplifying the processing technology of stainless steel tubes and overcoming the difficulty of directly machining internal threads. Simultaneously, the outer tube assembly is connected to the outer wall of the inner tube assembly via a sleeve 4, avoiding direct welding of dissimilar materials, improving the reliability and sealing of the connection between the inner and outer tube assemblies, thereby extending the service life of the heat exchanger.

[0051] like Figure 1 and 2 As shown, the internally threaded pipe 2 has first sleeve portions at both ends, and the smooth pipe section 3 has second sleeve portions at both ends. The first sleeve portions and the second sleeve portions are fitted together and welded to form an inner pipe assembly. Specifically, the internally threaded pipe 2 has first sleeve portions at both ends. These first sleeve portions are structures formed by specific processing or addition to the pipe ends of the internally threaded pipe 2, and their function is to provide a structured interface for the connection between the internally threaded pipe 2 and the smooth pipe section 3. The first sleeve portions can be formed by reducing or expanding the diameter of the pipe ends of the internally threaded pipe 2 to give it a specific outer or inner diameter, so as to facilitate fitting with the corresponding part of the smooth pipe section 3. At the same time, the smooth pipe section 3 has second sleeve portions at both ends. These second sleeve portions are structures formed by specific processing or addition to the pipe ends of the smooth pipe section 3, and their function is to form a complementary connection interface with the first sleeve portions of the internally threaded pipe 2. The second sleeve portion can be formed by reducing or expanding the diameter of the end of the smooth tube section 3 to give it a specific outer or inner diameter, so as to facilitate its connection with the first sleeve portion of the internally threaded tube 2. For example, it can be designed with an inner diameter slightly larger than the outer diameter of the first sleeve portion of the internally threaded tube 2, so that the first sleeve portion extends into it; or it can be designed with an inner diameter slightly smaller than the outer diameter of the first sleeve portion of the internally threaded tube 2, so that it extends into the first sleeve portion. Similarly, the second sleeve portion can also be achieved by welding prefabricated sleeve rings or sleeve sections to both ends of the smooth tube section 3.

[0052] Based on this, the first sleeve portion and the second sleeve portion are interlocked and welded together for sealing. Interlocking refers to inserting or fitting one sleeve portion onto the outside of another, forming an overlapping connection area. This interlocking structure provides stable support and a larger welding contact area for subsequent welding, facilitating precise alignment and fixation. Welding sealing refers to fusing the materials of the two sleeve portions in the interlocking area through methods such as fusion welding, forming a continuous and dense weld seam, thereby ensuring the mechanical strength and fluid tightness of the connection. Welding processes can include argon arc welding, laser welding, resistance welding, etc., with the specific choice determined based on material properties, production efficiency, and cost. Through this interlocking welding method, a complete inner tube assembly is ultimately formed, ensuring the continuity and sealing of the first medium channel.

[0053] The above technical solution, employing a sleeve-joint connection between the internally threaded tube 2 and the smooth tube section 3 followed by welding and sealing, effectively solves the problems of low reliability and susceptibility to defects caused by direct welding due to the high hardness and poor machinability of stainless steel. The sleeve structure provides a larger welding contact area and better alignment, significantly reducing welding stress concentration and the occurrence of welding defects, thereby improving the quality and reliability of the weld. Simultaneously, the overlapping area formed by the sleeve, combined with the weld seal, provides a double or more reliable sealing path, effectively preventing media leakage and ensuring the integrity of the first media channel and the long-term stable operation of the heat exchanger. This connection method not only simplifies the assembly process and improves production efficiency but also enhances the overall mechanical strength and vibration resistance of the inner tube assembly, extends the service life of the new type of shell-and-tube heat exchanger, and reduces maintenance costs caused by connection problems.

[0054] In a specific design, the second sleeve portion extends into the first sleeve portion for welding and sealing, or the first sleeve portion extends into the second sleeve portion for welding and sealing. When the second sleeve portion extends into the first sleeve portion for welding and sealing, it means that the second sleeve portion on the optical tube segment 3 is inserted into the first sleeve portion on the internally threaded tube 2, and welding and sealing are performed in this fitting area. This structure allows the weld joint to be located inside the sleeve, effectively preventing external environmental erosion of the weld, thereby improving the weld's corrosion resistance and long-term sealing reliability. Specific welding methods may include, but are not limited to: using laser welding technology, achieving high-quality, low-heat-input internal welds by precisely controlling the energy and position of the laser beam; or using inert gas shielded welding (such as TIG welding), performing fine welding in a protective gas environment to ensure the weld's density and strength.

[0055] When the first sleeve portion extends into the second sleeve portion for welding and sealing, it means that the first sleeve portion on the internally threaded pipe 2 is inserted into the interior of the second sleeve portion on the smooth pipe section 3, and welding and sealing are performed in this fitting area. This structure places the weld joint on the outside, facilitating visual inspection and real-time monitoring of the welding process by welding operators, thereby making it easier to ensure weld quality. Specific welding methods may include, but are not limited to: using gas metal arc welding (such as MIG / MAG welding), which has high welding efficiency and good filling ability, and is suitable for external welding; or using plasma arc welding, which has high energy density, fast welding speed, and can form deep and narrow welds, improving production efficiency.

[0056] like Figure 1 In the specific embodiment shown, the first sleeve end of the internally threaded pipe 2 is located inside the sleeve 4, and the outer end of the sleeve 4 is welded to the outer wall of the smooth pipe section 3. The weld between the internally threaded pipe 2 and the smooth pipe section 3 is located inside the sleeve 4. Specifically, the first sleeve end of the internally threaded pipe 2 being located inside the sleeve 4 defines the relative positional relationship between the first sleeve end of the internally threaded pipe 2 and the sleeve 4 at the connection between the internally threaded pipe 2 and the smooth pipe section 3. Specifically, the first sleeve end of the internally threaded pipe 2 is covered and surrounded by the sleeve 4, ensuring that the critical area of ​​the internal connection of the inner pipe assembly is not directly exposed to the external environment. This positional arrangement can be achieved through precise dimensional design and assembly, for example, ensuring that the first sleeve end is fully inserted into the internal space of the sleeve 4 when the inner pipe assembly is inserted into the sleeve 4. Simultaneously, the outer end of the sleeve 4 is welded to the outer wall of the smooth pipe section 3, describing the connection method between the sleeve 4 and the smooth pipe section 3. The outer end of the sleeve 4 is firmly connected to the outer wall of the smooth pipe section 3 by welding, thereby forming a sealed structure. This type of welding connection can employ various mature welding processes, such as TIG welding, MIG welding, or laser welding, to ensure the strength and sealing of the connection. Through this welding, the sleeve 4 not only secures the inner tube assembly but also provides a reliable sealing barrier for the second medium channel.

[0057] Furthermore, the weld between the internally threaded pipe 2 and the smooth pipe section 3 is located inside the sleeve 4. This technical feature clearly defines the final location of the weld connecting the internally threaded pipe 2 and the smooth pipe section 3. This weld is completely contained within the internal space of the sleeve 4 and is not directly exposed. This means that the length and positioning of the sleeve 4 are carefully designed to completely cover the welding area between the internally threaded pipe 2 and the smooth pipe section 3. This internal positioning effectively prevents the weld from being corroded by the external environment, mechanically damaged, or directly eroded by a secondary medium. This protection is particularly important when the inner pipe assembly is made of stainless steel while the outer pipe assembly is made of dissimilar materials such as carbon steel.

[0058] Through the above technical solution, this application effectively solves the problem that when the inner tube assembly is made of stainless steel and the outer tube assembly is made of carbon steel, the exposed weld seam may lead to welding defects caused by dissimilar materials, affecting sealing reliability and the service life of the heat exchanger. Specifically, the end of the first sleeve of the internally threaded tube 2 is positioned inside the sleeve 4, ensuring that the weld seam between the internally threaded tube 2 and the smooth tube section 3 is completely located inside the sleeve 4, so that the critical connection weld seam of the inner tube assembly is effectively shielded and protected by the sleeve 4. At the same time, the outer end of the sleeve 4 is welded to the outer wall of the smooth tube section 3, forming an external sealing layer, further isolating the internal weld seam from the external environment. This structural design avoids the direct exposure of dissimilar material weld seams to an environment that may cause corrosion or stress concentration, significantly reducing the risk of welding defects and improving the reliability and durability of the weld seam. Through the wrapping effect of the sleeve 4, not only is the mechanical strength of the connection enhanced, but also a longer service life and higher operational safety are provided for the heat exchanger.

[0059] In such Figure 2 In another embodiment shown, the end of the first sleeve portion of the internally threaded pipe 2 extends outside the sleeve 4. The outer end of the sleeve 4 is welded to the outer wall of the first sleeve portion of the internally threaded pipe 2. The weld between the internally threaded pipe 2 and the smooth pipe section 3 is located outside the sleeve 4. Specifically, "the end of the first sleeve portion of the internally threaded pipe 2 extends outside the sleeve 4" refers to the end structure of the internally threaded pipe 2 for fitting with the smooth pipe section 3, which is designed so that the end can extend beyond the boundary of the sleeve 4 after assembly. One implementation is to precisely calculate and control the length of the internally threaded pipe 2 before fitting it with the smooth pipe section 3, ensuring that the end of its first sleeve portion is exposed outside the sleeve 4 when fitting with the smooth pipe section 3 and mating with the sleeve 4. Another implementation is to adjust the structural dimensions of the sleeve 4 or its installation position on the inner pipe assembly so that the end of the first sleeve portion of the internally threaded pipe 2 can fully extend outside the sleeve 4.

[0060] "Welding the outer end of the sleeve 4 to the outer wall of the first sleeve portion of the internally threaded pipe 2" refers to the connection of the edge portion of the sleeve 4 near the internally threaded pipe 2 to the smooth outer surface of the internally threaded pipe 2 used for fitting, achieved by welding. Various welding processes can be employed. For example, fusion welding techniques such as TIG welding (tungsten inert gas welding) or MIG welding (metal inert gas welding) can be used to form a continuous and dense circumferential weld between the outer end of the sleeve 4 and the outer wall of the first sleeve portion of the internally threaded pipe 2, ensuring the mechanical strength and sealing performance of the connection. Alternatively, high-energy beam welding methods such as laser welding or resistance welding can be considered to achieve finer welding control and a smaller heat-affected zone, further improving the reliability of the connection.

[0061] "The weld between the internally threaded pipe 2 and the smooth pipe section 3 is located outside the sleeve 4" means that after the first sleeve portion of the internally threaded pipe 2 and the second sleeve portion of the smooth pipe section 3 are fitted together, the welded area formed to achieve a sealed connection between the two is spatially defined as being outside the sleeve 4. In actual operation, by precisely controlling the fitting depth of the internally threaded pipe 2 and the smooth pipe section 3, and combining this with the optimization of the welding process, it can be ensured that the weld is completely formed in the external area of ​​the sleeve 4, avoiding the weld being obscured by the sleeve 4. Alternatively, when designing the dimensions of the inner tube assembly, sufficient length margin can be reserved so that after the first sleeve portion of the internally threaded pipe 2 and the second sleeve portion of the smooth pipe section 3 are fitted together, the welded area can completely exceed the coverage area of ​​the sleeve 4, thereby facilitating subsequent welding operations and quality inspection.

[0062] Through the above technical solution, the end of the first sleeve portion of the internally threaded pipe 2 extends to the outside of the sleeve 4, and the outer end of the sleeve 4 is welded to the outer wall of the first sleeve portion of the internally threaded pipe 2. Simultaneously, it ensures that the weld between the internally threaded pipe 2 and the smooth pipe section 3 is located outside the sleeve 4. This application effectively solves the problems of limited welding operation space, difficult inspection, and unstable welding quality. This design completely exposes the critical weld between the internally threaded pipe 2 and the smooth pipe section 3 to the external environment, providing a spacious and unobstructed working area for welding operations. This facilitates precise operation using standard welding tools, significantly reducing the risk of welding defects caused by operational inconvenience. Furthermore, the location of the weld outside the sleeve 4 makes post-weld quality inspection intuitive and efficient. Visual inspection, non-destructive testing (such as radiographic testing and ultrasonic testing), and leak testing can all be performed conveniently and quickly, enabling timely detection and repair of potential welding defects and ensuring the reliability and sealing of the inner pipe assembly connection. This external welding solution not only simplifies the manufacturing process and improves production efficiency, but more importantly, it fundamentally enhances the overall safety and service life of the new shell-and-tube heat exchanger, avoiding leakage risks and maintenance costs caused by internal weld quality issues.

[0063] exist Figure 3 In another embodiment shown, the internally threaded tube 2 and the smooth tube section 3 are integrally formed.

[0064] The integral molding structure refers to the process where the internally threaded tube 2 and the smooth tube segment 3 are formed into a single, continuous integral component during manufacturing, without the need for welding, brazing, or other mechanical connections. This structure ensures the continuity and integrity of the inner tube assembly. Specifically, the integral molding structure can be achieved in several ways, including but not limited to the following: one method is to form an internal thread structure in a specific area of ​​a complete tube through cold drawing, extrusion, or spinning, while maintaining the smooth tube segment 3 at both ends; another method is to use internal forming technology, such as hydraulic bulging or roll forming, to form the required internal thread inside a pre-prepared straight tube, while keeping the smooth tube segment 3 at both ends. Through these technical solutions, since there is no longer a weld joint between the internally threaded tube 2 and the smooth tube segment 3, problems such as poor sealing and weld defects that may be caused by welding operations are completely eliminated, significantly improving the sealing reliability and structural integrity of the inner tube assembly. This integral molding structure avoids the challenges of welding stainless steel materials, especially considering that stainless steel is prone to thermal deformation and intergranular corrosion during welding, thus ensuring the stability and safety of the heat exchanger during long-term operation. Meanwhile, the one-piece molding process simplifies the manufacturing process of the inner tube assembly, reduces assembly steps and the need for welding quality inspection, effectively lowering production complexity and manufacturing costs. Furthermore, the one-piece molding structure results in more uniform material properties for the inner tube assembly, avoiding performance differences caused by variations in material microstructure in the weld area, further improving the overall performance and service life of the heat exchanger.

[0065] In the above Figure 1-3 Based on the proposed solution, a welding ring 7 may also be included. The welding ring 7 is fitted onto the outside of the inner tube assembly, with its inner side connected to the outer wall of the inner tube assembly and its outer side connected to the outer end of the sleeve 4. The welding ring 7 is a ring-shaped or cylindrical component, primarily serving as an intermediary connector between the inner tube assembly and the sleeve 4 to address reliability issues that may arise when directly connecting dissimilar materials. Specifically, the welding ring 7 can be made of a material with good welding compatibility with the inner tube assembly material (such as stainless steel), for example, a specific grade of stainless steel. Alternatively, considering the connection with the sleeve 4, the welding ring 7 can also be made of a material with good welding compatibility with the sleeve 4 material (such as carbon steel), for example, a specific grade of carbon steel. Furthermore, the welding ring 7 can also be a transitional material with good connection performance with both stainless steel and carbon steel, such as a nickel-based alloy, or a brazing material with a melting point not higher than that of the sleeve 4 material, to adapt to different connection process requirements.

[0066] The welding ring 7 is coaxially wrapped around the outer surface of the inner tube assembly. This fitting method allows the welding ring 7 to provide structural support and positioning for the inner tube assembly, while reserving an annular space between the inner tube assembly and the sleeve 4 to form the second medium channel. In practice, the inner diameter of the welding ring 7 can be designed to form an appropriate clearance fit or interference fit with the outer diameter of the inner tube assembly to facilitate assembly and subsequent connection operations. For example, the welding ring 7 can be expanded by heating before fitting, or an interference fit can be achieved by cold pressing.

[0067] A robust physical connection is established between the inner surface of the weld ring 7 and the outer surface of the inner tube assembly. This connection aims to ensure a tight seal between the inner tube assembly and the weld ring 7, preventing leakage of the medium from this connection and effectively transferring the structural loads generated during heat exchanger operation. This connection can be achieved by: using fusion welding processes, such as TIG welding, resistance welding, or laser welding, to fuse the inner side of the weld ring 7 to the outer wall of the inner tube assembly, forming a dense weld; or by using brazing, filling the space between the weld ring 7 and the inner tube assembly with a low-melting-point filler metal, heating it to melt and wet the mating surfaces, and then cooling to form a strong metallurgical bond and seal.

[0068] A robust physical connection is established between the outer surface of the welding ring 7 and the outer end of the sleeve 4. This connection is a crucial step in achieving the overall assembly of the inner tube assembly with the sleeve 4 of the outer tube assembly via the welding ring 7, while ensuring the integrity and sealing of the second medium channel. This connection can be achieved by: using fusion welding processes, such as TIG welding, resistance welding, or laser welding, to fuse the outer side of the welding ring 7 to the outer end of the sleeve 4, forming a dense weld; or by using brazing, filling the space between the welding ring 7 and the sleeve 4 with a low-melting-point filler metal, melting it upon heating to wet the mating surface, and then cooling to form a strong metallurgical bond and seal. In particular, when the sleeve 4 is made of carbon steel and the welding ring 7 is made of a material with a melting point no higher than that of carbon steel, brazing is a preferred connection method, effectively avoiding the difficulties of direct welding of dissimilar materials.

[0069] By introducing the welding ring 7 as an intermediate connector between the inner tube assembly and the sleeve 4, the above technical solution effectively solves the problem of poor reliability and easy welding defects when the inner tube assembly is made of stainless steel and the outer tube assembly (especially the sleeve 4) is made of carbon steel. The welding ring 7 allows for the selection of the most suitable connection process and material combination between the inner tube assembly and the welding ring 7, and between the welding ring 7 and the sleeve 4, thus avoiding direct fusion welding between stainless steel and carbon steel. For example, a welding method compatible with stainless steel can be used to connect the welding ring 7 to the inner tube assembly, and then a welding or brazing method compatible with carbon steel can be used to connect the welding ring 7 to the sleeve 4. This step-by-step, compatible connection method significantly improves the reliability and sealing of the connection, reduces the risk of welding defects, and thus ensures the stability and safety of the heat exchanger during long-term operation, extending the service life of the equipment. At the same time, this solution also provides a feasible technical path for the combined application of stainless steel inner tubes and carbon steel outer tubes, helping to reduce overall manufacturing costs.

[0070] In another implementation scheme (see reference) Figure 3 However, the internally threaded pipe 2 and the smooth pipe section 3 are welded together, not integrated. It also includes a welding ring 7. The weld between the internally threaded pipe 2 and the smooth pipe section 3 is located inside the welding ring 7 and is sealed through the welding ring 7. The welding ring 7 is sleeved on the outside of the inner pipe assembly. Its inner side is welded to the outer wall of the inner pipe assembly, and its outer side is welded to the outer end of the sleeve 4.

[0071] Specifically, the welding ring 7 is a ring-shaped structural component whose main function is to serve as an intermediate part for connection and sealing. When joining dissimilar materials, the welding ring 7 acts as a transition material, avoiding direct welding between the inner and outer tube assemblies, thereby reducing welding difficulty and improving weld quality. Furthermore, it provides additional protection and sealing for the weld seams inside the inner tube assembly. The welding ring 7 can be made of a material similar to the inner tube assembly material (stainless steel), such as austenitic stainless steel, or a material similar to the sleeve 4 material (e.g., carbon steel), such as low-alloy steel. More preferably, the welding ring 7 can be a transition material that welds well between stainless steel and carbon steel, such as a nickel-based alloy or a special stainless steel grade with good weldability. Its shape is typically annular, with an inner diameter slightly larger than the outer diameter of the inner tube assembly for easy fitting.

[0072] The weld between the internally threaded pipe 2 and the smooth pipe section 3 is located inside the welding ring 7. By placing the connecting weld inside the inner pipe assembly (i.e., the weld between the internally threaded pipe 2 and the smooth pipe section 3) inside the welding ring 7, physical protection can be provided for the weld, and the sealing effect of the welding ring 7 can be used to form a double seal, further enhancing the overall sealing reliability of the inner pipe assembly. During the design, ensure that the axial length of the welding ring 7 is sufficient to cover the connection area between the internally threaded pipe 2 and the smooth pipe section 3, so that the weld is completely enclosed by the welding ring 7. This can be achieved by precisely controlling the installation position and size of the welding ring 7. The sealing connection achieved through the welding ring 7 ensures that the media in the first and second media channels will not leak to each other or to the external environment. The sealing connection relies on the welding of the welding ring 7 to the outer wall of the inner pipe assembly and the welding of the welding ring 7 to the outer end of the sleeve 4. These welding operations should use continuous, defect-free welds, such as through full penetration welding or lap welding, and can be supplemented with non-destructive testing (such as penetrant testing and radiographic testing) to verify the integrity and sealing of the weld.

[0073] The welding ring 7 is fitted onto the outside of the inner tube assembly, providing initial positioning and structural support for the connection between the welding ring 7 and the inner tube assembly. An appropriate clearance fit exists between the inner diameter of the welding ring 7 and the outer diameter of the inner tube assembly to facilitate fitting. During fitting, tooling fixtures can be used for precise centering and positioning to ensure that the welding ring 7 accurately covers the target area. The inner side of the welding ring 7 is welded to the outer wall of the inner tube assembly, firmly fixing the welding ring 7 to the inner tube assembly, forming the first structural connection and seal between the inner tube assembly and the welding ring 7. A circumferential fillet weld or a butt weld is typically used. Welding processes such as TIG welding, MIG welding, or laser welding can be selected to ensure the density and strength of the weld. Before welding, the welding area must be cleaned to remove oil, oxide layers, and other impurities. The outer side of the welding ring 7 is welded to the outer end of the sleeve 4, connecting the welding ring 7 to the sleeve 4 of the outer tube assembly. This completes the overall connection and sealing between the inner and outer tube assemblies, while also isolating direct welding of dissimilar materials. A circumferential weld, such as a fillet weld or butt weld, is used. Considering that the sleeve 4 may be made of carbon steel, while the welding ring 7 may be stainless steel or a transition material, appropriate welding materials and welding parameters need to be selected to ensure the reliability of dissimilar material welding. For example, nickel-based welding materials or austenitic stainless steel welding materials can be used to reduce hot cracking and the formation of brittle phases.

[0074] By introducing the welding ring 7 as a connection intermediary between the inner and outer tube assemblies through the above technical solution, direct dissimilar material welding between the stainless steel inner tube assembly and the outer tube assembly (especially the sleeve 4), which may be made of carbon steel, is effectively avoided. This significantly reduces the welding difficulty and defect risk caused by material differences, and improves the reliability of the connection and the welding quality. Simultaneously, the welding ring 7 encloses the weld between the internally threaded tube 2 and the smooth tube section 3, forming an additional protective layer and sealing barrier. This design not only protects the weld inside the inner tube assembly from external environmental influences, but also constructs a double-sealing structure through the two welding processes of the welding ring 7 with the inner tube assembly and the sleeve 4, greatly enhancing the sealing performance of the entire heat exchanger and effectively preventing media leakage. This solution, by optimizing the connection structure, improves the structural stability and service life of the shell-and-tube heat exchanger under dissimilar material combinations, making it possible to use lower-cost stainless steel as the inner tube material, while ensuring the safe and reliable operation of the heat exchanger.

[0075] In a specific implementation, the outer tube assembly is made of carbon steel or stainless steel, and the welding ring 7 is made of a material with a melting point not higher than that of the outer tube assembly material. Specifically, the outer tube assembly is made of carbon steel or stainless steel. Carbon steel, as an iron-carbon alloy, has advantages such as low cost, high strength, and ease of processing, and is often used to manufacture structural components with low corrosion resistance requirements, such as Q235 and Q345 grades of carbon steel. Stainless steel, on the other hand, is an alloy steel containing at least 10.5% chromium, possessing excellent corrosion resistance, high temperature resistance, and good mechanical properties, making it suitable for applications with high corrosion resistance requirements, such as 304 and 316L grades of stainless steel. The selection of carbon steel or stainless steel as the material for the outer tube assembly aims to balance cost and performance to meet the needs of different application scenarios.

[0076] Meanwhile, the welding ring 7 is made of a material with a melting point no higher than that of the outer tube assembly material. This welding ring 7 is typically annular and serves as a connection and seal during the welding process. The choice of its material is crucial. For example, when the outer tube assembly is made of carbon steel, the welding ring 7 can be made of brazing materials with lower melting points, such as copper-based alloys, silver-based alloys, or nickel-based alloys; when the outer tube assembly is made of stainless steel, the welding ring 7 can be made of nickel-based alloys, copper-based alloys, or specific grades of low-melting-point stainless steel welding wire with melting points no higher than those of stainless steel. By selecting a welding ring 7 with a melting point no higher than that of the outer tube assembly material, the welding ring 7 can be melted and flowed at a lower welding temperature, thereby forming a reliable connection without damaging or significantly affecting the performance of the outer tube assembly material.

[0077] Through the above technical solution, this application effectively solves the reliability problem of welding dissimilar materials by optimizing the material properties of the welding ring 7. Since the melting point of the welding ring 7 is not higher than that of the outer tube assembly material, during the welding process, the welding ring 7 can preferentially melt and fill the connection gap, forming a dense weld, thereby ensuring a sealed connection between the inner tube assembly and the sleeve 4. This design avoids welding defects caused by excessive differences in melting points between the outer tube assembly material and the welding ring 7, such as incomplete fusion, porosity, and cracks, significantly improving welding quality and connection reliability. Furthermore, the lower welding temperature also reduces the negative impact on the heat-affected zone of the material, helping to maintain the structural integrity and mechanical properties of the outer tube assembly, thereby extending the service life of the new shell-and-tube heat exchanger and improving its operational safety.

[0078] In some embodiments of this application described above, fins and / or teeth are provided on the inner and outer surfaces of the internally threaded tube 2.

[0079] Specifically, "fins" refer to thin, sheet-like structures extending from the inner and outer surfaces of the internally threaded tube 2. Their main function is to significantly increase the heat exchange surface area, thereby providing a larger contact interface for heat exchange between the medium and the tube wall. The formation of fins can be, but is not limited to, integral extrusion or roll forming during the tube forming process; or by welding, brazing, or mechanically connecting prefabricated fin structures to the tube wall surface. For example, spiral fins can be formed on the inner surface of the internally threaded tube 2 to guide the fluid's spiral flow and increase the heat exchange area; straight or annular fins can be formed on the outer surface to enhance heat exchange with the medium in the outer tube assembly.

[0080] "Gearing" refers to the protrusions or depressions of a certain height and shape formed on the inner and outer surfaces of the internally threaded pipe 2. Its main function is to increase the roughness of the fluid flowing through the pipe wall, thereby effectively disturbing the fluid boundary layer, promoting fluid turbulence, and thus enhancing the convective heat transfer effect. The formation of gears can include, but is not limited to, forming periodic or non-periodic tooth-shaped, wavy, or dot-shaped structures on the pipe wall surface through mechanical processing methods such as rolling, stamping, and scribing. For example, continuous or discontinuous spiral gears can be formed on the inner surface of the internally threaded pipe 2 to further enhance fluid turbulence; annular or dot-shaped gears can be formed on the outer surface to disrupt the boundary layer and improve heat transfer efficiency.

[0081] The expression "and / or" means that fins, teeth, or both can be set separately, allowing for flexible selection and combination based on specific heat exchange requirements and fluid characteristics.

[0082] By employing the aforementioned technical solution, and by incorporating fins and / or teeth on the inner and outer surfaces of the internally threaded tube 2, this application effectively addresses the problem of insufficient heat exchange efficiency caused by the relatively low thermal conductivity of stainless steel. Specifically, the fins significantly increase the heat exchange surface area, providing a wider channel for heat transfer between the medium and the tube wall, thereby promoting effective heat exchange. Simultaneously, the teeth increase the surface roughness of the tube wall, effectively disturbing the fluid boundary layer, enhancing fluid turbulence, and thus improving the convective heat transfer coefficient. These two enhanced heat exchange structures can be used individually or in combination, working together to compensate for the inherent defect of poor thermal conductivity in stainless steel, enabling high-efficiency heat exchange performance even when using lower-cost stainless steel. This design not only ensures that the heat exchanger maintains a cost advantage while operating efficiently, but also, by enhancing the heat exchange capacity of the inner tube assembly in the stainless steel shell-and-tube heat exchanger, allows the entire heat exchanger to achieve the expected heat exchange effect within a compact structure, enhancing the product's market competitiveness.

[0083] The following example will provide a more detailed explanation of the above technical solution:

[0084] In a specific application scenario, to reduce material costs and address the high cost of traditional copper tube heat exchangers, the manufacturer decided to use stainless steel to manufacture the inner tube assembly of the heat exchanger. This inner tube assembly is made of stainless steel, and its core component is the internally threaded tube 2. The internal thread structure effectively enhances heat exchange. Both ends of the internally threaded tube 2 are connected to smooth tube sections 3. A first medium channel is formed inside the inner tube assembly to carry the refrigerant in the heat pump system. The two ends of the smooth tube section 3 serve as the medium inlet and outlet of this first medium channel, respectively, facilitating the entry and exit of the refrigerant.

[0085] In the manufacturing process of the inner tube assembly, to ensure the reliability of the connection between the internally threaded tube 2 and the smooth tube section 3, one of the following two methods can be adopted:

[0086] One approach is to use a single-piece molding structure for the internally threaded tube 2 and the smooth tube section 3. This structure eliminates the connecting weld seam, further improving the integrity and reliability of the inner tube assembly.

[0087] Another approach involves having a first sleeve portion at both ends of the internally threaded pipe 2 and a second sleeve portion at both ends of the smooth pipe section 3. During assembly, the second sleeve portion extends into the first sleeve portion, or the first sleeve portion extends into the second sleeve portion, and then a sealed connection is achieved through welding, thus forming a complete inner pipe assembly. This sleeve welding method ensures the sealing of the internal media channel of the inner pipe assembly, avoiding the risk of media leakage. For example, in actual production, the weld between the internally threaded pipe 2 and the smooth pipe section 3 can be located inside the sleeve 4, thus protecting the weld and improving the durability of the connection; alternatively, the weld can extend to the outside of the sleeve 4 to facilitate welding operations and quality inspection.

[0088] The third method is: the internally threaded pipe 2 and the smooth pipe section 3 are welded together using a welding ring 7.

[0089] The structural design of the outer pipe assembly also fully considers connection reliability and media flow. The outer pipe assembly includes an outer pipe 1 and two pipe sleeves 4. These two pipe sleeves 4 are respectively located on the outer sides of both ends of the inner pipe assembly, with the outer pipe 1 connected between the two pipe sleeves 4. A first connecting pipe 5 and a second connecting pipe 6 are respectively provided on the pipe sleeves 4. The outer ends of the pipe sleeves 4 are connected to the outer wall of the inner pipe assembly, thereby forming a second media channel between the inner and outer pipes for carrying the water media in the heat pump system. The first connecting pipe 5 and the second connecting pipe 6 serve as the media inlet and media outlet of this second media channel, respectively.

[0090] To further improve the sealing performance between the inner tube assembly and the sleeve 4, especially when the outer tube assembly is made of carbon steel and the inner tube assembly is made of stainless steel, a welding ring 7 can be introduced. The welding ring 7 is fitted onto the outside of the inner tube assembly, with its inner side connected to the outer wall of the inner tube assembly and its outer side connected to the outer end of the sleeve 4. When the weld between the internally threaded tube 2 and the smooth tube section 3 is located inside the welding ring 7, the welding ring 7 can achieve a sealed connection through welding, protecting and reinforcing the weld. In scenarios involving dissimilar material connections, such as when the outer tube assembly is made of carbon steel and the welding ring 7 is made of a material with a melting point no higher than that of carbon steel, this helps to form a more reliable connection during welding, avoiding welding defects that may occur when directly welding stainless steel and carbon steel, thus solving the reliability problem of dissimilar material welding mentioned in the background art.

[0091] In actual operation, the refrigerant flows through the first medium channel of the inner tube assembly. The threaded structure of the internally threaded tube 2 increases the heat exchange area and promotes fluid turbulence, significantly improving heat exchange efficiency. Simultaneously, water flows through the second medium channel of the outer tube assembly, exchanging heat with the inner tube assembly. This structural design, through the use of stainless steel inner tube assemblies, effectively reduces material costs; the design of the internally threaded tube 2 ensures heat exchange efficiency; and the application of sleeve welding and welding rings 7 ensures the sealing and reliability of the connection between the inner and outer tube assemblies and within the inner tube assembly, overcoming the technical challenges of traditional shell-and-tube heat exchangers in terms of cost, processing, and connection reliability. Compared with existing technologies that directly use copper tubes or difficult-to-process stainless steel internally threaded tubes, this heat exchanger optimizes manufacturing costs and improves connection reliability while ensuring heat exchange performance, providing Manufacturer A with a competitive product.

[0092] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of 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 scope of protection of this application.

Claims

1. A novel shell-and-tube heat exchanger, characterized in that, Includes inner tube assembly and outer tube assembly; The inner tube assembly is made of stainless steel and includes an internally threaded tube (2) and a smooth tube section (3) connected to its two ends respectively. A first medium channel is formed inside the inner tube assembly, and the two ends of the smooth tube section (3) serve as the medium inlet and medium outlet of the first medium channel respectively. The outer tube assembly includes an outer tube (1) and two sleeves (4). The two sleeves (4) are respectively disposed on the outer sides of both ends of the inner tube assembly. The outer tube (1) is connected between the two sleeves (4). The sleeves (4) are respectively provided with a first connector (5) and a second connector (6). The outer end of the sleeve (4) is connected to the outer wall of the inner tube assembly, thereby forming a second medium channel between the inner and outer tubes. The first connector (5) and the second connector (6) serve as the medium inlet and medium outlet of the second medium channel, respectively.

2. The novel shell-and-tube heat exchanger as described in claim 1, characterized in that, The two ends of the internally threaded pipe (2) are provided with a first sleeve portion, and the two ends of the smooth pipe section (3) are provided with a second sleeve portion. The first sleeve portion and the second sleeve portion are fitted together and then welded and sealed to form an inner pipe assembly.

3. The novel shell-and-tube heat exchanger as described in claim 2, characterized in that, The second sleeve portion extends into the first sleeve portion for welding and sealing, or the first sleeve portion extends into the second sleeve portion for welding and sealing.

4. The novel shell-and-tube heat exchanger as described in claim 3, characterized in that, The first sleeve end of the internally threaded pipe (2) is located inside the sleeve (4), the outer end of the sleeve (4) is welded to the outer wall of the smooth pipe section (3), and the weld between the internally threaded pipe (2) and the smooth pipe section (3) is located inside the sleeve (4).

5. The novel shell-and-tube heat exchanger as described in claim 3, characterized in that, The end of the first sleeve portion of the internally threaded pipe (2) extends to the outside of the sleeve (4). The outer end of the sleeve (4) is welded to the outer wall of the first sleeve portion of the internally threaded pipe (2). The weld between the internally threaded pipe (2) and the bare pipe section (3) is located outside the sleeve (4).

6. The novel shell-and-tube heat exchanger as described in claim 1, characterized in that, The internally threaded tube (2) and the smooth tube section (3) are integrally formed.

7. The novel shell-and-tube heat exchanger as described in any one of claims 1 to 6, characterized in that, It also includes a welding ring (7), which is sleeved on the outside of the inner tube assembly, with its inner side connected to the outer wall of the inner tube assembly and its outer side connected to the outer end of the sleeve (4).

8. The novel shell-and-tube heat exchanger as described in claim 1, characterized in that, It also includes a welding ring (7), the weld between the internally threaded pipe (2) and the bare pipe section (3) is located inside the welding ring (7), and a sealed connection is achieved through the welding ring (7); the welding ring (7) is sleeved on the outside of the inner pipe assembly, its inner side is welded to the outer wall of the inner pipe assembly, and its outer side is welded to the outer end of the sleeve (4).

9. The novel shell-and-tube heat exchanger as described in claim 7, characterized in that, The outer tube assembly is made of carbon steel or stainless steel, and the welding ring (7) is made of a material with a melting point not higher than that of the outer tube assembly material.

10. The novel shell-and-tube heat exchanger as described in claim 1, characterized in that, The inner and outer surfaces of the internally threaded tube (2) are provided with fins and / or teeth.

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