Continuous bent serpentine coil for closed cooling or condensing heat exchange elements and method of manufacture

Abstract

This invention relates to a continuously bent serpentine coil for closed-loop cooling or condensing heat exchange elements and its manufacturing method. The coil includes straight sections and elbow sections, which alternate sequentially to form a continuously continuous bent serpentine heat exchange loop. Each elbow section includes a transition zone with an adjacent straight section and a bending zone between the transition zones. The inner wall of the elbow section has a corrugated structure extending circumferentially along its axis and at least covering the transition zone. The manufacturing method includes the following steps: selecting raw materials of corresponding specifications; forming the raw materials into an integral straight tube or separate straight tubes for the straight and elbow sections; forming a corrugated structure at least in the transition zone; and bending the straight tube portion for the elbow section or the straight tube for the elbow section. The continuously bent serpentine coil of this invention can simultaneously achieve high-efficiency heat exchange, low-cost manufacturing, and long-term stable operation.

Description

Technical Field

[0001] This invention relates to heat exchange equipment, specifically to a continuously bent serpentine coil for closed-loop cooling or condensation heat exchange elements and its manufacturing method. The continuously bent serpentine coil is suitable for industrial closed-loop cooling or condensation systems with liquid or gaseous media and operating pressures ≥0.15MPa, achieving efficient heat exchange, low-cost manufacturing, and long-term stable operation. Background Technology

[0002] Continuous bend serpentine coils are core heat exchange elements in closed-loop cooling or condensing equipment. Their structural design and manufacturing methods directly affect the heat exchange efficiency, manufacturing cost, and service life of the equipment. Current continuous bend serpentine coils generally consist of multiple straight pipe sections and multiple elbow sections, alternating between them to form a continuous, interconnected bend serpentine heat exchange loop. The inner walls of the elbow sections are designed with straight walls. The straight pipe sections and elbow sections are either integrally formed or welded together.

[0003] The current structural design and manufacturing methods for continuously bent serpentine coils have the following problems.

[0004] First, current continuously bent serpentine coils struggle to simultaneously achieve both low cost and high heat exchange efficiency. On one hand, continuous bending is difficult for thin-walled tubes with a wall thickness ≤0.68mm, requiring auxiliary processes such as adding a mandrel or filling the tube with hard, fine particles and sealing both ends. This manufacturing method is cumbersome, difficult to control, and inefficient. Furthermore, the filling and removal of mandrels and hard, fine particles require additional manpower and resources, significantly increasing manufacturing costs and hindering standardized mass production. Therefore, continuous bending of thin-walled tubes is difficult and costly. On the other hand, without auxiliary processes, only thick-walled tubes with a wall thickness ≥0.68mm can be continuously bent. While this reduces processing difficulty, it results in higher raw material consumption for thicker tubes and decreased heat exchange efficiency due to increased wall thermal resistance.

[0005] Secondly, while thin-walled pipes with a wall thickness of ≤0.68mm offer lower thermal resistance and save on raw materials, they suffer from insufficient rigidity. Therefore, even with the aforementioned auxiliary processes, continuous bending can still lead to defects such as residual wall deformation and unstable mechanical properties, failing to meet long-term operational safety requirements. Consequently, the application of thin-walled pipes in continuously bent serpentine coils is limited by current structural design and manufacturing methods.

[0006] Third, current continuous bending serpentine coils have weak resistance to thermal expansion and contraction, resulting in a short service life. This is because, during the operation of closed-loop cooling or condensing equipment, the periodic changes in liquid and gaseous media and ambient temperature cause the coils to expand and contract. The straight-walled bends have poor elastic deformation buffering capacity, leading to stress concentration at the transition between the bends and straight sections during long-term operation. This can cause leaks, pipe wall cracks, and other malfunctions, shortening the coil's service life and increasing equipment maintenance costs and downtime losses.

[0007] Fourth, for integrally formed continuous bending serpentine coils, it is difficult to flexibly adapt to the production of continuous bending serpentine coils with different bending angles. On the other hand, for continuously bending serpentine coils welded together, the transition between the straight-walled elbow section and the straight pipe section is not smooth, which easily generates local eddies, reduces heat exchange efficiency, and makes it difficult to control the stability of welding quality. Therefore, the current manufacturing methods for continuously bending serpentine coils have poor adaptability.

[0008] We have tried to improve the process by optimizing auxiliary processes, thickening the pipe wall, and adding reinforcing ribs, but none of these methods have achieved the synergistic effect of "thin-walled pipes - high heat exchange efficiency - low manufacturing cost - long service life".

[0009] Therefore, it is desirable to provide a novel continuously bent serpentine coil for closed-loop cooling or condensation heat exchange elements and a method for manufacturing the same, which has the following advantages: thin-walled energy saving, high-efficiency heat exchange, low manufacturing cost, resistance to thermal expansion and contraction, long service life and mass production capability, thereby overcoming the aforementioned problems existing in current continuously bent serpentine coils. Summary of the Invention

[0010] Therefore, the object of the present invention is to provide a continuously bent serpentine coil for closed-loop cooling or condensation heat exchange elements and a method for manufacturing the same.

[0011] In one aspect, the present invention relates to a continuously bent serpentine coil for a closed-loop cooling or condensing heat exchange element, the continuously bent serpentine coil comprising straight pipe sections and elbow sections, the straight pipe sections and the elbow sections alternating sequentially to form a continuously continuous bent serpentine heat exchange loop. According to the invention, the elbow section includes a transition zone with an adjacent straight pipe section and a bending zone located between the transition zones. The inner wall of the elbow section is provided with a corrugated structure in the circumferential direction, the corrugated structure extending along the axial direction of the elbow section and at least covering the transition zone of the elbow section.

[0012] According to an embodiment, the corrugated structure is integrally formed on the inner wall of the tube during the tube forming process.

[0013] In this article, "corrugated structure" refers to a structure that is installed on the inner wall of the elbow section, so that radially inward protrusions and / or radially outward depressions are generated on the inner wall, thereby forming a corrugated structure extending along the axial direction of the elbow section.

[0014] According to the embodiment, the corrugated structure is uniformly distributed along the circumferential direction of the bend section, that is, the interval between each corrugation is the same, and the error is ≤0.01mm.

[0015] According to an embodiment, the corrugated structure covers the entire elbow section, that is, it covers the transition area and the bending area.

[0016] According to an embodiment, the corrugated structure defines the wave pitch and wave depth, wherein the wave depth is 0.1mm to 50mm and the wave pitch is 0.1mm to 100mm.

[0017] According to the embodiment, the nominal diameter of the continuous bending serpentine coil is DN14~DN50. Different corrugated designs are adopted for different nominal diameters. Specifically, for continuous bending serpentine coils with nominal diameters of DN14~DN25, a corrugation pitch of 0.1mm~5mm is used to avoid the flow channel being too narrow and causing fluid stagnation; while for continuous bending serpentine coils with nominal diameters of DN25~DN50, a corrugation pitch of 5mm~100mm is used to ensure smooth fluid flow under high flow conditions and achieve a balance between heat exchange efficiency and flow resistance.

[0018] According to the embodiment, the wall thickness and diameter of the straight pipe section are the same as those of the elbow section to ensure the overall adaptability of the serpentine circuit. The straight pipe section and the elbow section are also made of the same material.

[0019] According to the embodiment, the wall thickness of the coil is ≥0.3mm and ≤0.68mm, with a tolerance of ±0.02mm.

[0020] According to the embodiments, the material of the continuously bent serpentine coil can be stainless steel, carbon steel, copper or aluminum alloy, etc.

[0021] According to an embodiment, the straight tube section can be any one of a smooth tube, a corrugated tube, a spiral tube, an elliptical tube, or a flat tube.

[0022] According to the embodiment, the length of the transition zone is 5 to 50 times the diameter of the coil, so as to achieve a smooth mechanical transition and heat exchange continuity between the elbow section and the straight section, and to ensure the structural stability and operational reliability of the continuous bend.

[0023] According to an embodiment, the bending radius of the elbow section is 2 to 2.5 times the diameter of the coil, and / or the bending (turning) angle of the elbow section is 70°, 90°, 180° or 225°.

[0024] According to the embodiments, the elbow section and the straight pipe section are integrally formed during pipe forming or welded together on site. The integral forming method is suitable for mass standardized production scenarios, avoiding stress concentration at the weld seam, thereby improving structural integrity and pressure resistance. The on-site welding assembly method is suitable for customized or on-site installation scenarios, and the welding process can be selected according to the material. For example, argon arc welding is used for stainless steel, brazing is used for copper and aluminum alloys, and electric arc welding is used for carbon steel. In addition, after welding, the weld seam needs to be penetrant tested to ensure there are no defects such as porosity or lack of fusion, and the weld seam is ground to ensure a smooth transition between the inner walls of the straight pipe section and the elbow section, with a transition tolerance ≤0.05mm, to avoid localized eddies and ensure heat exchange efficiency and operational stability.

[0025] The concept of this invention is to enhance the mechanical properties of pipes by utilizing a corrugated structure, enabling thin-walled pipes with a wall thickness of 0.3mm to 0.68mm to achieve the structural strength level of thick-walled pipes with a wall thickness of ≥0.68mm. Therefore, thin-walled pipes can be stably and continuously bent without the need for mandrels or filling with hard, fine particles, and can stably withstand water / gas pressure tests of ≥1.6MPa (the test pressure is more than 10 times the working pressure to ensure sufficient safety redundancy), meeting the safety requirements for closed-loop cooling or condensation operation under liquid and gaseous media and working pressures ≥0.15MPa. Thus, this invention ensures operational safety, enables continuous bending of thin-walled pipes, and significantly reduces the amount of raw materials used in the pipe construction.

[0026] In another aspect, the present invention also provides a method for manufacturing a continuously bent serpentine coil for a closed cooling or condensing heat exchange element as described above, wherein the manufacturing method may employ an integral molding method or an on-site welding assembly method.

[0027] Whether using a one-piece molding method or an on-site welding and assembly method, the manufacturing process includes the following steps: Provide raw materials, that is: select the corresponding specifications of raw materials according to the material and nominal diameter (DN14~DN50) of the continuous bending serpentine coil to be manufactured; The raw material is formed into a tube, that is: the raw material is made into an integral straight tube or into separate straight tubes for straight sections and elbow sections by a tube forming machine. The integral straight tube includes straight tube sections for straight sections and elbow sections respectively. Both the straight tube section for elbow section and the straight tube for elbow section include transition areas at both ends and a bending area located in between. Forming a corrugated structure, namely: forming a corrugated structure on at least the transition area using a corrugating forming device; and The process of forming the bend section involves bending the straight pipe portion or the straight pipe used for the bend section using a pipe bending machine, particularly bending the area to be bent, without adding a mandrel or filling it with hard, fine particles, thereby forming a continuous bending serpentine coil unit or a separate bend section.

[0028] For the first step, the raw material thickness is designed to be 0.3mm~0.68mm, with the wall thickness tolerance controlled within ±0.02mm to ensure the forming accuracy and structural strength of the corrugated structure. For the third step, the corrugated forming device is located at the rear end of the pipe production line and is configured to ensure that the corrugated structure is evenly distributed along the circumferential direction with an error ≤0.01mm, to avoid uneven distribution that could lead to localized stress concentration or heat transfer dead zones. The corrugation depth of the corrugated structure is 0.1mm~50mm, and the corrugation pitch is 0.1mm~100mm. For the fourth step, according to the design requirements of the continuous bending serpentine loop, the material is bent into elbow sections with the required bending angles of 70°, 90°, 180°, or 225°.

[0029] According to an embodiment, for the integrated molding method, the manufacturing method further includes the following step after the bending step: integrally connecting multiple continuously bent serpentine coil units, for example by welding or other integral connection methods, to form a continuously bent serpentine coil. Then, a water / air pressure test of ≥1.6MPa is performed, held at pressure for 30 minutes, and the system is checked for leaks. Simultaneously, indicators such as heat transfer coefficient and the integrity of the corrugated structure are tested.

[0030] According to an embodiment, for the on-site welding assembly method, the manufacturing method further includes the following steps after the bending step: aligning the straight pipe for the straight pipe section with the bent elbow section so that the straight pipe section and the elbow section are positioned according to the direction of a continuous bending serpentine loop; and sealingly welding the transition area of ​​the elbow section with the straight pipe for the straight pipe section to form a continuously bent serpentine coil. For the welding step, the welding temperature and speed are controlled to avoid damaging the corrugated structure.

[0031] According to the embodiment, for the on-site welding assembly method, the manufacturing method further includes the following steps after the welding step: grinding the weld to ensure a smooth transition between the straight pipe section and the elbow section on the inner wall, with a transition tolerance ≤0.05mm. Before grinding, the weld is subjected to a penetrant test to ensure weld quality, and after grinding, a water / gas pressure test of ≥1.6MPa is performed, held for 30 minutes, to check for leaks, and simultaneously to test indicators such as heat transfer coefficient and the integrity of the corrugated structure.

[0032] According to an embodiment, the step of forming a corrugated structure by means of a corrugating forming apparatus includes further forming a corrugated structure on the area to be bent.

[0033] According to an embodiment, in the bending step, the advancing speed of the straight pipe portion used for the bend section or the straight pipe used for the bend section is configured to match the linear velocity of the neutral layer to avoid deformation of the corrugated structure.

[0034] The advantages of this invention are that the continuously bent serpentine coil can be continuously bent even with thin-walled pipes with a wall thickness of 0.3mm to 0.68mm. The corrugated structure on the inner wall of the bend provides mechanical reinforcement, enabling continuous bending of thin-walled pipes with a wall thickness of 0.3mm to 0.68mm without the need for mandrels or hardened fine particles. This solves the current problem that continuous bending of thin-walled pipes below 0.68mm requires complex auxiliary processes and cannot be mass-produced. It also avoids the limitation that continuous bending without a mandrel requires thick-walled pipes of 0.68mm or more. Experimental verification shows that, compared to current structural designs, the corrugated structure on the inner wall of the bend according to this invention has advantages in strength, fluid dynamics, and thermodynamics.

[0035] Specifically, in terms of strength, due to the corrugated structure, the strength of a thin wall with a corrugated structure in the range of 0.3mm to 0.68mm is equivalent to the strength of a bend section with a straight wall design of more than 0.68mm. This allows it to stably withstand water / air pressure test pressures greater than 1.6MPa (test pressure is more than 10 times the working pressure). This ensures energy saving in thin-walled applications and safety under high-pressure conditions, while reducing raw material consumption by more than 56% and eliminating auxiliary process costs. As a result, it enables mass standardized production and significantly reduces manufacturing costs.

[0036] In terms of fluid mechanics, the corrugated structure can disturb the flow field of the medium (liquid, gas), destroy the flow boundary layer, and expand the effective heat exchange area. Combined with the characteristic that thin-walled pipes can reduce the thermal resistance of the pipe wall, the heat transfer coefficient of the coil of the present invention is increased by 15% to 20% compared with the current thick-walled straight-walled coil design, thereby improving the heat exchange efficiency of closed cooling or condensing equipment and meeting the industry's demand for high efficiency and energy saving.

[0037] In terms of thermodynamics, the corrugated structure possesses excellent elastic deformation buffering performance, effectively absorbing the thermal expansion and contraction stress generated by temperature changes, thereby enhancing resistance to thermal expansion and contraction and preventing stress concentration in the transition zone between elbows and straight pipe sections, thus reducing the risk of leaks, cracks, and other failures. Long-term operating condition verification shows that the service life of the coil according to the present invention is extended by more than 20% compared to current coil products of the same specifications with straight wall design, significantly reducing equipment maintenance costs.

[0038] Therefore, the continuous bending serpentine coil of the present invention can operate stably under different flow rates and different turning angles, with smooth heat exchange and sufficient safety redundancy.

[0039] Furthermore, the manufacturing method of this invention has a wide range of applications and is flexible and efficient. In particular, the coil and manufacturing method of this invention are suitable for pipe diameters of various specifications from DN14 to DN50, can match straight pipe sections of various structural forms, and the corner angle can be flexibly customized. Moreover, the integrated molding method and the on-site welding assembly method are suitable for mass standardized production and customized on-site installation scenarios, respectively, improving market adaptability and manufacturing efficiency. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of a continuously bent serpentine coil according to an embodiment of the present invention; Figure 2 This is a schematic diagram of an integral straight pipe used to form the continuous bending serpentine coil of the present invention; Figure 3 This is a flowchart of a manufacturing method for an integrated forming method of a continuously bent serpentine coil according to an embodiment of the present invention; Figure 4 This is a flowchart of the manufacturing method of the on-site welding assembly method of the continuously bent serpentine coil according to an embodiment of the present invention. Detailed Implementation

[0041] Figure 1 This is a schematic diagram of the continuously bent serpentine coil of the present invention; Figure 2 This is a schematic diagram of an integral straight pipe used to form the continuous bending serpentine coil of the present invention; Figure 3 This is a flowchart of a manufacturing method for an integrated forming process of continuously bent serpentine coils; Figure 4 This is a flowchart of the manufacturing method for on-site welding assembly of continuously bent serpentine coils.

[0042] exist Figure 1 In this continuous bend serpentine coil, there is a straight pipe section 1 and an elbow section 2 with a corrugated structure. The straight pipe section and the elbow section alternate sequentially, forming a continuous, interconnected bend serpentine heat exchange loop. For example... Figure 1 As shown, the elbow section 2 includes a transition zone 3 with the adjacent straight pipe section 1 and a bent zone 4 located between the transition zones 3. The inner wall of the elbow section 2 is uniformly provided with a corrugated structure 6 along the circumferential direction. The corrugated structure extends along the axial direction of the elbow section 6 and covers the entire elbow section 2, i.e., covers the transition zone 3 and the bent zone 4. The corrugated structure 6 may be integrally formed on the inner wall of the elbow section 2.

[0043] like Figure 1As shown, the corrugated structure 6 consists of alternating radially inward protrusions and radially outward depressions on the inner wall of the elbow section 2, thereby forming a uniformly distributed corrugated structure extending along the axial direction of the elbow section 2. The intervals between each corrugation are the same, with an error ≤0.01mm. The corrugated structure 6 can also consist only of radially inward protrusions or only of radially outward depressions.

[0044] Figure 1 The continuously bent serpentine coil shown can be a single unit. In practice, multiple such units can be connected together to form the final continuously bent serpentine coil.

[0045] Figure 1 The manufacturing method of the continuously bent serpentine coil shown generally includes the following steps: Provide raw materials, that is: select the corresponding raw materials (such as stainless steel, carbon steel, etc.) according to the material and nominal diameter (DN14~DN50) of the continuous bending serpentine coil to be manufactured. The raw material is formed into a tube, that is: the raw material is made into an integral straight tube or into separate straight tubes for straight tube section 1 and elbow section 2 respectively by a tube forming machine. The integral straight tube includes straight tube sections for straight tube section 1 and elbow section 2 respectively. Both the straight tube section for elbow section 2 and the straight tube for elbow section 2 include transition areas at both ends and a bending area located in between. The corrugated structure 6 is formed, that is, the corrugated structure 6 is formed on the straight pipe portion of the elbow section 2 or on the straight pipe of the elbow section 2 by a corrugating forming device; and The elbow section 2 is formed by bending the straight pipe portion or the straight pipe used for the elbow section 2 using a pipe bending machine, especially bending the area to be bent, without adding a mandrel or filling it with hard fine particles, thereby forming a continuous bending serpentine coil unit or a separate elbow section 2.

[0046] Depending on the application scenario, the manufacturing method can employ either integrated molding or on-site welding and assembly. Figure 2 The diagram illustrates an integral straight pipe suitable for a one-piece molding method, comprising a straight pipe section 1 for forming a straight pipe segment 1 and a straight pipe section 5 for forming an elbow segment 2, wherein the elbow segment 2 is formed by bending the straight pipe section 5. The straight pipe section 5 includes transition areas at both ends and an unbent area to be bent for forming a bending area 4. A corrugated structure 6 has been formed on the straight pipe section 5.

[0047] The following reference Figure 3 and Figure 4 Describe the manufacturing methods for both approaches.

[0048] exist Figure 3In China, the manufacturing method of the integrated molding process generally includes the following steps: Step 1A: Select the corresponding raw material according to the material and nominal diameter of the target coil. The thickness of the raw material is designed to be 0.3mm~0.68mm, and the wall thickness tolerance is controlled within ±0.02mm. Step 2A: Start the tube production line to form the raw material into an integral straight tube; Step 3A: Integrate a corrugated forming device at the rear end of the pipe manufacturing production line. Based on the corrugation parameters (i.e., corrugation depth 0.1mm~50mm, corrugation pitch 0.1mm~100mm), process a corrugated structure on the inner wall of the transition zone and the bending zone of the straight pipe section used for the elbow section. During processing, ensure that the corrugated structure is uniformly distributed along the circumferential direction of the straight pipe section used for the elbow section, with an error ≤0.01mm, and that the corrugation parameters are suitable for the specifications of the integral straight pipe. Step 4A: The integral straight pipe with the corrugated structure is continuously bent using a pipe bending machine. According to the design requirements of the continuous bending serpentine loop, bends with required bending angles of 70°, 90°, and 180° are machined to form a continuous bending serpentine coil unit. The bending radius of the bends is controlled to be 2 to 2.5 times the pipe diameter, and the pipe's feed speed is matched with the linear velocity of the neutral layer during bending to avoid deformation of the corrugated structure. Step 5A: According to the design requirements of the continuous bending serpentine circuit, connect multiple continuous bending serpentine coil units together as a whole, for example by welding or other integrated connection methods, to form a continuous bending serpentine coil.

[0049] Step 6A: Conduct a water / air pressure test of ≥1.6MPa, hold the pressure for 30 minutes, check for leaks, and at the same time check key indicators such as heat transfer coefficient and corrugated structure integrity.

[0050] Step 5A is optional. That is, the continuous bending serpentine coil unit formed in step 4A can be used as the finished continuous bending serpentine coil. In addition, if the welding connection method is used in step 5A, the weld seam needs to be ground after welding to ensure a smooth transition of the inner wall of the straight pipe section 1 and the elbow section 2 of the adjacent continuous bending serpentine coil units.

[0051] exist Figure 4 In China, the manufacturing method of on-site welding assembly generally includes the following steps: Step 1B: Select the corresponding raw material according to the material and nominal diameter of the target coil. The thickness of the raw material is designed to be 0.3mm~0.68mm, and the wall thickness tolerance is controlled within ±0.02mm. Step 2B: Start the pipe production line to form the raw materials into separate straight pipes for straight sections and elbow sections. Ensure that the nominal diameter, wall thickness, and material of the straight pipes used for straight sections and the straight pipes used for elbow sections are consistent.

[0052] Step 3B: Integrate a corrugated forming device at the rear end of the pipe manufacturing production line. Based on the corrugation parameters (i.e., corrugation depth of 0.1mm~50mm and corrugation pitch of 0.1mm~100mm), process a corrugated structure on the inner wall of the straight pipe used for the elbow section. During processing, ensure that the corrugated structure is uniformly distributed along the circumferential direction of the straight pipe used for the elbow section, with an error ≤0.01mm, and that the corrugation parameters are suitable for the specifications of the straight pipe. Step 4B: The straight pipe with the corrugated structure is bent using a pipe bending machine. Following the design requirements of a continuous serpentine bending loop, elbow sections with bending angles of 70° and 225° are machined. The bending radius of the elbow section is controlled to be 2 to 2.5 times the pipe diameter, and the pipe's feed speed is matched with the linear velocity of the neutral layer during bending to prevent deformation of the corrugated structure. Step 5B: Based on the on-site installation space and heat exchange circuit design requirements of the closed-loop cooling or condensing equipment, align and position the straight pipe section 1 and the elbow section 2 according to the direction of the continuous bending serpentine circuit. Step 6B: Select the appropriate welding process based on the pipe material, and perform a sealing weld between the transition zone 3 of the elbow section 2 and the straight pipe section 1. During welding, control the welding temperature and speed to avoid high-temperature damage to the corrugated structure; Step 7B: Use penetrant testing to inspect the weld quality and grind the weld to ensure a smooth transition between the inner walls of straight pipe section 1 and elbow section 2; Step 8B: Conduct a water / air pressure test of ≥1.6MPa, hold the pressure for 30 minutes, check for leaks, and at the same time check key indicators such as heat transfer coefficient and corrugated structure integrity.

[0053] The following examples illustrate the manufacturing methods for both approaches.

[0054] Example 1: Fabrication of a DN25 stainless steel continuously bent serpentine heat exchange coil using an integrated molding method

[0055] A continuously bent serpentine heat exchange coil with a nominal diameter of DN25 is manufactured from 304 austenitic stainless steel. The coil has a wall thickness of 0.4 mm and consists of a straight section 1 and an elbow section 2 with a corrugated structure. Elbow section 2 includes a transition zone 3 and a bending zone 4. The corrugations in the corrugated structure have a depth of 0.8 mm, a pitch of 3 mm, and are uniformly distributed circumferentially. The bending radius of the elbow section is twice its nominal diameter (i.e., 50 mm). This coil is suitable for high-flow-rate applications with a DN25 pipe diameter.

[0056] According to the coil Figure 3 The flowchart shown illustrates the manufacturing process, using 304 austenitic stainless steel strip as raw material, designed with a wall thickness of 0.4mm. During the bending process, the bending angles are 90° and 180°, without the addition of a mandrel or the filling with hard, fine particles.

[0057] The heat transfer performance of the coil was tested under closed-loop cooling or condensation conditions with liquid or gaseous media and an operating pressure ≥0.15MPa. The results show that the heat transfer coefficient is increased by 18% compared with the existing coils of the same specification with a thickness of ≥0.68mm and a straight wall design, while the raw material cost is reduced by 57%.

[0058] This coil can be mass-produced without the need for auxiliary processes.

[0059] Example 2: Fabrication of DN40 carbon steel continuously bent serpentine heat exchange coil using an integrated molding method

[0060] A continuously bent serpentine heat exchange coil with a nominal diameter of DN40 is manufactured from carbon steel. The coil has a wall thickness of 0.5 mm and consists of a straight section 1 and an elbow section 2 with a corrugated structure. Elbow section 2 includes a transition zone 3 and a bending zone 4. The corrugations in the corrugated structure have a depth of 1 mm, a pitch of 6 mm, and are uniformly distributed circumferentially. The bending radius of the elbow section is 2.5 times its nominal diameter (i.e., 100 mm). This coil is suitable for high-flow-rate applications with a DN40 pipe diameter.

[0061] According to the coil Figure 3 The flowchart shown illustrates the manufacturing process, using carbon steel strip as the raw material, designed with a wall thickness of 0.5mm. During the bending step, the bending angle is 225°, and no mandrel is added or the strip is filled with hard, fine particles.

[0062] The heat transfer performance of the coil was tested under closed-loop cooling or condensation conditions with liquid or gaseous media and an operating pressure ≥0.15MPa. The results show that the heat transfer coefficient is increased by 16% compared with the existing coils of the same specification with a thickness of ≥0.68mm and a straight wall design, while the raw material cost is reduced by 55%.

[0063] This coil can be mass-produced without auxiliary processes, making it suitable for industrial cooling or condensation scenarios in non-corrosive environments.

[0064] Example 3: Fabrication of DN14 copper continuously bent serpentine heat exchange coil by on-site welding assembly.

[0065] A continuously bent serpentine heat exchange coil with a nominal diameter of DN14 is manufactured from copper. The coil has a wall thickness of 0.3 mm and includes a straight section 1 and an elbow section 2 with a 70° bend and corrugated structure. The corrugations in the corrugated structure have a depth of 0.2 mm, a pitch of 0.5 mm, and are uniformly distributed circumferentially. This coil is suitable for narrow flow channels with a small diameter of DN14. Elbow section 2 has a transition zone 3 and a bend zone 4.

[0066] According to the coil Figure 4 The flowchart shown illustrates the manufacturing process, using copper strip as the raw material, designed with a wall thickness of 0.3mm. During the bending step, the bending angle is 70°, and no mandrel is added or the strip is filled with hard, fine particles.

[0067] The coil was tested under closed-loop cooling or condensation conditions with liquid or gaseous media and a working pressure ≥0.15MPa. The results showed that the coil exhibited no stress concentration during operation, had excellent thermal expansion and contraction buffering effect, and its service life was extended by 22% compared to existing products of the same specifications without corrugated structures.

[0068] While the foregoing description and accompanying drawings illustrate preferred embodiments of the invention, it should be understood that various additions, modifications, combinations, and / or substitutions may be made therein without departing from the spirit and scope of the disclosure as defined in the appended claims. In particular, those skilled in the art will appreciate that the disclosure may be embodied in other specific forms, structures, arrangements, proportions, and other elements, materials, and components without departing from the spirit or essential characteristics of the disclosure. Those skilled in the art will understand that the disclosure can be used with numerous modifications to structure, arrangement, proportion, materials, and components that are particularly suited to specific environments and operational requirements without departing from the principles of the disclosure. Furthermore, the features described herein may be used alone or in combination with other features. For example, a feature described in connection with one component may be used and / or interchanged with a feature described in another component. Therefore, the embodiments disclosed herein are to be considered illustrative rather than restrictive in all respects, and the scope of the disclosure is indicated by the appended claims and is not limited to the foregoing description.

[0069] Those skilled in the art will understand that various modifications and alterations can be made to this disclosure without departing from the broad scope of the appended claims. Some of these have been discussed above, and others will be apparent to those skilled in the art. The following examples provide non-limiting embodiments of various configurations of the apparatuses, components, systems, and methods disclosed herein.

Claims

1. A continuously bent serpentine coil for a closed-loop cooling or condensing heat exchange element, the continuously bent serpentine coil comprising a straight section (1) and an elbow section (2), the straight section (1) and the elbow section (2) alternating sequentially to form a continuously continuous bent serpentine heat exchange loop. Its features are, The elbow section (2) includes a transition zone (3) with the adjacent straight pipe section (1) and a bending zone (4) located between the transition zone (3). The inner wall of the elbow section is provided with a corrugated structure along the circumferential direction. The corrugated structure extends along the axial direction of the elbow section and at least covers the transition zone (3) of the elbow section (2).

2. The continuously bent serpentine coil according to claim 1, characterized in that, The corrugated structure is uniformly distributed along the circumferential direction of the elbow section (2), with an error ≤0.01mm.

3. The continuously bent serpentine coil according to claim 1, characterized in that, The corrugated structure covers the entire elbow section (2).

4. The continuously bent serpentine coil according to any one of claims 1-3, characterized in that, The corrugated structure (2) defines the wave pitch and wave depth, wherein the wave depth is 0.1mm~50mm and the wave pitch is 0.1mm~100mm.

5. The continuously bent serpentine coil according to claim 4, characterized in that, The nominal diameter of the continuously bent serpentine coil is DN14~DN50.

6. The continuously bent serpentine coil according to claim 5, characterized in that, For continuous bent serpentine coils with nominal diameters of DN14 to DN25, the wave pitch is 0.1 mm to 5 mm; for continuous bent serpentine coils with nominal diameters of DN25 to DN50, the wave pitch is 5 mm to 100 mm.

7. The continuously bent serpentine coil according to any one of claims 1-3, characterized in that, The wall thickness and diameter of the straight pipe section (1) are the same as those of the elbow section (2).

8. The continuously bent serpentine coil according to claim 7, characterized in that, The wall thickness is ≥0.3mm and ≤0.68mm, with a tolerance of ±0.02mm.

9. The continuously bent serpentine coil according to any one of claims 1-3, characterized in that, The straight tube section (1) is any one of a smooth tube, a corrugated tube, a spiral tube, an elliptical tube, or a flat tube.

10. The continuously bent serpentine coil according to any one of claims 1-3, characterized in that, The length of the transition zone (3) is 5 to 50 times the diameter of the continuous bent serpentine coil.

11. The continuously bent serpentine coil according to any one of claims 1-3, characterized in that, The bending radius of the elbow section is 2 to 2.5 times the diameter of the continuously bent serpentine coil, and / or the bending angle of the elbow section is 70°, 90°, 180° or 225°.

12. The continuously bent serpentine coil according to any one of claims 1-3, characterized in that, The elbow section and the straight pipe section are integrally formed or welded together.

13. A method for manufacturing a continuously bent serpentine coil according to any one of claims 1-12, Its features are, The manufacturing method includes the following steps: Select the appropriate raw material based on the material and nominal diameter of the continuous bending serpentine coil to be manufactured; The raw material is formed into an integral straight pipe or into separate straight pipes for straight pipe sections and elbow sections using a pipe forming machine. The integral straight pipe includes straight pipe sections for straight pipe sections and elbow sections respectively. Both the straight pipe sections for elbow sections and the straight pipe sections for elbow sections include transition areas at both ends and a bending area located in between. A corrugated structure is formed in at least the transition zone using a corrugating forming device; and A pipe bending machine bends straight pipe sections for elbow sections or straight pipes for elbow sections without adding a mandrel or filling with hard fine particles, thereby forming a continuous bending serpentine coil unit or a separate elbow section.

14. The manufacturing method according to claim 13, wherein, The manufacturing method further includes the following steps after the bending step: Multiple continuous bending serpentine coil units are connected together to form a continuous bending serpentine coil.

15. The manufacturing method according to claim 13, wherein, The manufacturing method further includes the following steps after the bending step: Align the straight pipe used for the straight pipe section (1) with the bent elbow section (2) with each other; The transition zone (3) of the elbow section (2) is sealed and welded to the straight pipe for the straight pipe section (1) to form a continuous bent serpentine coil.

16. The manufacturing method according to claim 15, wherein, The manufacturing method further includes the following steps after the welding step: grinding the weld seam to make the straight pipe section and the elbow section smoothly transition at the inner wall, with a transition tolerance of ≤0.05mm.

17. The manufacturing method according to any one of claims 13-16, wherein, The step of forming a corrugated structure using a corrugated forming device includes further forming a corrugated structure on the area to be bent.

18. The manufacturing method according to any one of claims 13-16, wherein, During the bending step, the advancing speed of the straight pipe section used for the bend or the straight pipe used for the bend is configured to match the linear velocity of the neutral layer.

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