Processing method of integral external finned tube with discrete and continuous characteristic fins

Abstract

The present application discloses a method for processing an integral external finned tube with discrete and continuous characteristic fins, comprising the following steps: S1, forming teeth on the base tube: forming a plurality of tooth-shaped structures on the outer wall of the base tube, with spaces between adjacent tooth-shaped structures; S2, processing fins: first aligning the main cutting edge of the finning tool with one side of the tooth-shaped structure, and then rotating the base tube; when the base tube rotates, the main cutting edge of the finning tool advances from one side of the tooth-shaped structure to the other side to cut the tooth-shaped structure and the tube wall of the base tube, the portion of the tooth-shaped structure cut by the main cutting edge forms a discrete fin, and the portion of the tube wall of the base tube cut by the main cutting edge forms a continuous fin at the root of the discrete fin. The external fin unit of the integral external finned tube formed by the processing has the function of destroying the boundary layer flow state of the cooling medium near the wall surface. The integral external finned tube has no contact thermal resistance, which greatly improves the heat exchange capacity of the integral external finned tube, and has a high processing speed and is not prone to fin breakage.

Description

Technical Field

[0001] The present application relates to the technical field of external finned tubes, and in particular to a method for processing an integral external finned tube having discrete and continuous characteristic fins. Background Art

[0002] Pipe heat exchangers are currently widely used in high-energy-consuming fields such as air conditioning, refrigeration, petroleum, and chemical industries. As an important heat transfer component, the heat transfer performance of finned tubes directly affects the energy consumption level of pipe heat exchangers. Researchers believe that the development of high-efficiency and energy-saving finned tube forming technology with complex surface thermal functional structures is an important way to reduce unit energy consumption. Depending on the position of the fins, finned tubes can be divided into external fin type and internal fin type. Since the outer surface of the finned tube is often in contact with low heat transfer coefficient media such as air, and the inner surface often uses high-efficiency heat transfer methods such as single-phase liquid cooling or phase change heat transfer, the relatively poor convective heat transfer capacity of the outer side of the finned tube has become an important reason that limits the overall performance of the heat exchanger.

[0003] Externally finned tubes are categorized into two types based on fin type: two-dimensional continuous and three-dimensional discrete. Two-dimensional continuous externally finned tubes are finned tubes with multiple fins spaced apart along the axial direction of the tube, and with the same fins arranged continuously along the circumference of the tube. Three-dimensional discrete externally finned tubes are finned tubes with multiple fins arranged discretely along both the axial and circumferential directions of the tube. When a finned tube is exposed to a high Reynolds number fluid, a thin flow layer with significant viscous forces forms on the surface of the finned tube. This thin layer region tends to produce a higher temperature gradient, so disrupting the boundary layer effect is an effective way to improve the heat transfer performance of finned tubes.

[0004] Finned tubes with two-dimensional continuous fins usually have a large heat transfer area, but the slow flow rate of the cooling medium around the fins and the difficulty in destroying the boundary layer limit the improvement of their heat transfer performance. The finned tubes with three-dimensional discrete structures have a relatively small specific surface area. Discrete fins are conducive to increasing the flow rate of the medium around the fins and improving the flow state of the medium. Fins of specific shapes can even generate vortices between the fins. The heat transfer performance of finned tubes with three-dimensional discrete structures is better than that of finned tubes with two-dimensional continuous fins.

[0005] In the prior art, methods for processing three-dimensional discrete finned tubes include the suiting process, planing, rolling-plowing / extrusion, plowing / extrusion, and extrusion-cutting methods for forming three-dimensional fins. However, the suiting process requires the processing of the outer fin unit and then fitting it onto the tube body. Although this process is simple, the outer fin unit has contact thermal resistance at the interface with the tube body, resulting in poor heat transfer performance compared to monolithic three-dimensional discrete finned tubes. The planing method requires the use of a specially shaped tool to directly plan out the desired fin shape on the tube surface in one go, which is time-consuming and inefficient. The rolling-plowing / extrusion, plowing / extrusion, and extrusion-cutting methods can only form fins with a height of 1.2-1.6 mm on the tube surface. When the processed fin height exceeds 1.6 mm, the fins are prone to breakage during processing. Generally speaking, the higher the fin height, the better the heat transfer performance of the finned tube. Therefore, the heat transfer performance of finned tubes produced by these processes is still limited.

[0006] Therefore, it is necessary to design a method for processing three-dimensional discrete integral external finned tubes which is simple and not prone to fin breakage during processing.

[0007] Application Contents

[0008] Therefore, the technical problem to be solved by the present application is to overcome the defects of low production efficiency or easy fin breakage or contact thermal resistance of the processed fins in the processing method of the prior art, thereby providing a processing method for an integral external fin tube with discrete and continuous characteristic fins.

[0009] To solve the above technical problems, the technical solutions of this application are as follows:

[0010] A method for processing an integral external finned tube having discrete and continuous characteristic fins comprises the following steps:

[0011] S1. Toothing the base tube: forming a plurality of tooth-shaped structures on the outer wall of the base tube, with spaces between adjacent tooth-shaped structures;

[0012] S2. Processing fins: first align the main cutting edge of the finning tool with one side of the toothed structure, and then rotate the base tube; when the base tube rotates, the main cutting edge of the finning tool advances from one side of the toothed structure to the other side to cut the toothed structure and the tube wall of the base tube, and the portion of the toothed structure cut by the main cutting edge forms a discrete fin, and the portion of the tube wall of the base tube cut by the main cutting edge forms a continuous fin at the root of the discrete fin.

[0013] Furthermore, when the main cutting edge advances from one side of the toothed structure to the other side to cut the toothed structure and the wall of the base tube, the rake surface of the finning tool folds the cut portion of the toothed structure and the cut portion of the base tube wall outward for the first time to form a fin prototype with discrete and continuous characteristics, and the secondary rake surface of the finning tool folds the fin prototype with discrete and continuous characteristics outward again to form a fin with discrete and continuous characteristics.

[0014] Furthermore, the rotation speed of the base pipe is 1-100 m / min.

[0015] Furthermore, the feed speed of the wing forming tool is 0.2-10 mm / r.

[0016] Furthermore, the cutting depth of the finning tool on the base pipe is 0.2-5 mm.

[0017] Furthermore, the base tube is made of a heat-conducting metal material or a heat-conducting polymer material.

[0018] Furthermore, the wing-forming tool includes a main cutting edge, a secondary cutting edge, a rake face, a secondary rake face and a flank face, the secondary rake face is a cambered surface, and the secondary rake face transition is arranged between the rake face and the secondary flank face.

[0019] Furthermore, the radius of the secondary rake face is 0.1-2.0 mm.

[0020] Furthermore, the angle between the main cutting edge and the feed direction is the main deflection angle, and the main deflection angle is 30°-60°; the angle between the front cutting edge and the base surface is the front angle, and the size of the front angle is 45°-75°; the angle between the main cutting edge and the base surface is the blade inclination angle, and the size of the blade inclination angle is -30° to -60°, and the base surface is parallel to the bottom surface of the wing-forming tool.

[0021] Furthermore, the angle between the secondary cutting edge and the feed direction is the secondary rake angle, and the magnitude of the secondary rake angle is 90°; the angle between the flank face and the base face is the rake angle, and the magnitude of the rake angle is 5°; the angle between the flank face and the secondary rake face is the secondary rake angle, and the magnitude of the secondary rake angle is 5°.

[0022] The technical solution of this application has the following advantages:

[0023] 1. The present application provides a method for processing an integral external fin tube with discrete and continuous characteristic fins. The external fin unit of the integral external fin tube formed by the processing includes continuous fins and discrete fins. By arranging continuous fins at the roots of the discrete fins, the discrete fins have the characteristics of high specific surface area and high fin ratio, and have strong single-fin heat exchange performance. The continuous fins have the function of destroying the flow state of the boundary layer of the cooling medium near the wall, which can further enhance the heat exchange performance of the pipeline; in addition, the external fin unit and the base tube are formed as one piece, and the external fin unit and the base tube are continuous and dense without contact thermal resistance; this integral external fin tube improves the heat exchange performance of the external fin tube from three aspects: increasing the specific surface area, destroying the flow state of the boundary layer of the cooling medium near the wall, and reducing the contact thermal resistance, thereby greatly improving the heat exchange capacity of the integral external fin tube. Moreover, this processing method of the integral external finned tube can simultaneously process and form discrete fins and continuous fins. Not only is the processing speed fast, but the residual stress of the fins with discrete and continuous characteristics formed by the processing is small, the fin breakage phenomenon is not likely to occur during processing, and the fin forming performance is good.

[0024] 2. In the method for processing an integral external finned tube with discrete and continuous characteristic fins provided in the present application, the rotation speed of the base tube is 1-100 m / min, which can reduce the risk of fin breakage or the speed of tool wear.

[0025] 3. The processing method of the integral external finned tube with discrete and continuous characteristic fins provided in the present application has a feed rate of the fin forming tool of 0.2-10 mm / r, which can obtain a better fin pitch and fin thickness.

[0026] 4. The processing method of the integral external fin tube with discrete and continuous characteristic fins provided in this application has a fillet of the secondary rake surface of 0.1-2.0 mm, which can make the fins fold smoothly, reduce processing impact and improve the wing root strength.

[0027] 5. The present application provides a method for processing an integral external fin tube with discrete and continuous characteristic fins. The angle between the back cutting surface and the base surface is the back angle, and the size of the back angle is 5°, which can ensure the sharpness of the fin-forming tool. The angle between the back cutting surface and the secondary front cutting surface is the secondary back angle, and the size of the secondary back angle is 5°, which can reduce the friction between the fin and the back cutting surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] Figure 1 Schematic diagram of an unprocessed base pipe;

[0030] Figure 2 Schematic diagram of the base pipe after forming the tooth structure;

[0031] Figure 3 It is a schematic diagram of the processing part of the fin forming tool;

[0032] Figure 4 Schematic diagram of the finning tool acting on the base pipe;

[0033] Figure 5 Schematic diagram of the process of machining the base tube for the finning tool;

[0034] Figure 6 This is a schematic three-dimensional diagram of a finished product obtained by the processing method of the integral external finned tube with discrete and continuous characteristic fins of the present application.

[0035] Description of reference numerals:

[0036] 1. Base tube; 11. Tooth structure; 3. External fin unit; 2. Fin forming tool; 21. Main cutting edge; 23. Rake face; 24. Secondary cutting edge; 25. Secondary flank face; 31. Continuous fin; 32. Discrete fin; 33. Spacing. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solution of this application in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0038] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this application and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0039] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0040] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0041] Example

[0042] like Figures 1 to 6 As shown, this embodiment provides a method for processing an integral external finned tube with discrete and continuous characteristic fins, comprising the following steps:

[0043] S1. Base Tube Toothing: Several tooth-shaped structures 11 are machined onto the outer wall of the base tube 1, with spaces between adjacent tooth-shaped structures 11. In this embodiment, the base tube 1 has an inner diameter of 2-15 mm, a wall thickness of 1-5 mm, and an outer diameter of 3-20 mm. The base tube 1 can be made of a metal with good thermal conductivity, such as copper or iron, or a non-metallic material, such as a thermally conductive polymer. Furthermore, in this embodiment, the tooth-shaped structures 11 are formed on the surface of the base tube 1 using a plastic forming method, such as rolling or stamping. The cross-section of the tooth-shaped structures 11 can have a rectangular, trapezoidal, or triangular shape, among other configurations.

[0044] S2. Fin processing: First, align the main cutting edge 21 of the fin forming tool 2 with one side of the toothed structure 11, and then rotate the base tube 1; when the base tube 1 rotates, the main cutting edge 21 of the fin forming tool 2 advances from one side of the toothed structure 11 to the other side to cut the toothed structure 11 and the tube wall of the base tube 1. The portion of the toothed structure 11 cut by the main cutting edge 21 forms a discrete fin 32, and the portion of the tube wall of the base tube 1 cut by the main cutting edge 21 forms a continuous fin 31 at the root of the discrete fin 32. Specifically, as Figure 4 and Figure 5As shown, when the main cutting edge 21 advances from one side of the toothed structure 11 to the other side to cut the toothed structure 11 and the tube wall of the base tube 1, the front cutting surface 23 of the finning tool 2 folds the cut portion of the toothed structure 11 and the cut portion of the tube wall of the base tube 1 outward for the first time to form a fin prototype with discrete and continuous characteristics, and the secondary cutting edge 24 of the finning tool 2 folds the fin prototype with discrete and continuous characteristics outward again to form a fin with discrete characteristics and continuous characteristics. For the sake of convenience, the fin with discrete characteristics is called a discrete fin, and the fin with continuous characteristics is called a continuous fin. The discrete fin 32 and the continuous fin 31 surrounding the base tube 1 constitute the outer fin unit 3.

[0045] As the base tube 1 is continuously fed, a plurality of outer fin units 3 consisting of continuous fins 31 and discrete fins 32 are processed along the length direction of the base tube 1. In this way, each outer fin unit 3 includes a continuous fin 31 continuously and integrally formed on the outer periphery of the base tube 1 along the circumference of the base tube 1, and a plurality of discrete fins 32 formed on the outer periphery of the continuous fin 31. There is a gap 33 between two adjacent discrete fins 32, so that the two adjacent discrete fins 32 are independent and not connected.

[0046] The present embodiment provides a method for processing an integral external fin tube with discrete and continuous characteristic fins, wherein the processed external fin unit 3 includes a continuous fin 31 and a discrete fin 32. By arranging the continuous fin 31 at the root of the discrete fin 32, the discrete fin 32 has the characteristics of high specific surface area and high fin ratio, and has strong single-fin heat exchange performance; the continuous fin 31 has the function of destroying the flow state of the boundary layer of the cooling medium near the wall, which can further enhance the heat exchange performance of the pipeline; in addition, the external fin unit 3 and the base tube 1 are integrally formed, and the external fin unit 3 and the base tube 1 are continuous and dense without contact thermal resistance; this integral external fin tube improves the heat exchange performance of the external fin tube from three aspects: increasing the specific surface area, destroying the flow state of the boundary layer of the cooling medium near the wall, and reducing the contact thermal resistance, thereby greatly improving the heat exchange capacity of the integral external fin tube. Moreover, this processing method of the integral external fin tube can simultaneously process and form discrete fins 32 and continuous fins 31. Not only is the processing speed fast, but the residual stress of the processed external fin unit 3 is small, and it is not easy to break the fins during processing. The external fin unit 3 has good forming performance.

[0047] Of course, in the process of processing fins, the processing parameters and the design parameters of the fin forming tool 2 are also very important, which are introduced below:

[0048] As for processing parameters, the rotation speed of the base tube 1 is 1-100m / min to reduce the risk of fin breakage or the wear rate of the finning tool 2. The feed rate of the finning tool 2 is 0.2-10mm / r to obtain a better fin pitch (the fin pitch refers to the distance between two adjacent outer fin units 3) and fin thickness (the fin thickness refers to the thickness of the discrete fin 32 or the continuous fin 31 in the axial direction of the base tube 1). The cutting depth of the finning tool 2 on the base tube 1 is 0.2-5mm. The cutting depth is equal to the sum of the thickness of the discrete fin 32 in the radial direction of the base tube 1 and the thickness of the continuous fin 31 in the radial direction of the base tube 1. When the size of the discrete fin 32 is determined, increasing the cutting depth can increase the height of the continuous fin 31, and reducing the cutting depth will reduce the height of the continuous fin 31.

[0049] like Figure 3 and Figure 4 As shown, the winging tool 2 is made of materials including, but not limited to, cemented carbide and high-speed steel. The winging tool 2 includes a primary cutting edge 21, a rake face 23, a secondary cutting edge 24, and a secondary flank face 25. The secondary cutting edge 24 is a constant-diameter arc surface with a specific curvature, and this arc surface is referred to as the secondary cutting edge fillet. The curvature radius of the arc surface is equal to the value of the secondary cutting edge fillet. The secondary cutting edge fillet is 0.1-2.0 mm, which allows the fin to be smoothly folded, reducing machining impact and increasing wing root strength. The secondary cutting edge 24 is transitionally disposed between the rake face 23 and the secondary flank face 25. The angle between the primary cutting edge 21 and the feed direction is the principal deflection angle, which is 30°-60°. The angle between the front cutting edge 23 and the base surface (the base surface is parallel to the bottom surface of the wing forming tool 2) is the front angle. The front angle, as the angle between the front cutting edge 23 and the base surface, determines the flipping rate of the fin. In this embodiment, the size of the front angle is 45°-75°. In this embodiment, the size of the main deflection angle is 30°-60°, and the size of the front angle is 45°-75°. In this way, the risk of the wing root being broken or the significant circumferential translation of the fin can be reduced. The angle between the main cutting edge 21 and the base surface is the blade inclination angle, and the size of the blade inclination angle is -30° to -60°. The angle between the secondary cutting edge 24 and the feed direction is the secondary deflection angle, and the size of the secondary deflection angle is 90°. The angle between the secondary back cutting edge 25 and the base surface is the back angle, and the size of the back angle is 5°, which ensures the sharpness of the wing forming tool 2. The included angle between the secondary flank surface 25 and the secondary cutting edge 24 is the secondary flank angle, and the magnitude of the secondary flank angle is 5°, which reduces the friction between the fin and the secondary flank surface 25 .

[0050] In summary, the processing method of the integral external finned tube with continuous and discrete characteristics provided in this embodiment has the characteristics of high specific surface area, high cooling medium flow rate, and the ability to destroy the near-wall thermal boundary layer. The residual stress of the fins after processing is small and the fins are not easily broken during processing.

[0051] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of this application.

Claims

1. A method for processing an integral external finned tube with discrete and continuous characteristic fins, characterized in that: The following steps are involved: S1. Toothing the base tube: forming a plurality of tooth-shaped structures (11) on the outer wall of the base tube (1), with spaces between adjacent tooth-shaped structures (11); S2, processing fins: first aligning the main cutting edge (21) of the fin forming tool (2) with one side of the toothed structure (11), and then rotating the base tube (1); when the base tube (1) rotates, the main cutting edge (21) of the fin forming tool (2) advances from one side of the toothed structure (11) to the other side to cut the toothed structure (11) and the tube wall of the base tube (1), the portion of the toothed structure (11) cut by the main cutting edge (21) forms a discrete fin (32), and the portion of the tube wall of the base tube (1) cut by the main cutting edge (21) forms a continuous fin (31) at the root of the discrete fin (32); When the main cutting edge (21) advances from one side of the toothed structure (11) to the other side to cut the toothed structure (11) and the wall of the base tube (1), the front cutting edge (23) of the fin forming tool (2) initially folds outward the cut portion of the toothed structure (11) and the cut portion of the wall of the base tube (1) to form a fin prototype with discrete and continuous characteristics, and the secondary cutting edge (24) of the fin forming tool (2) folds outward the fin prototype with discrete and continuous characteristics again to form a fin with discrete and continuous characteristics; wherein the secondary cutting edge (24) is an arc surface of equal diameter; The angle between the main cutting edge (21) and the feed direction is the main deflection angle, and the magnitude of the main deflection angle is 30°-60°; the angle between the front cutting surface (23) and the base surface is the rake angle, and the magnitude of the rake angle is 45°-75°; the angle between the main cutting edge (21) and the base surface is the blade inclination angle, and the magnitude of the blade inclination angle is -30° to -60°, and the base surface is parallel to the bottom surface of the wing-forming tool (2).

2. The method for processing an integral external finned tube with discrete and continuous characteristic fins according to claim 1, characterized in that: The rotation speed of the base tube (1) is 1-100 m / min.

3. The method for processing an integral external finned tube with discrete and continuous characteristic fins according to claim 1, characterized in that: The feed speed of the wing forming tool (2) is 0.2-10 mm / r.

4. The method for processing an integral external finned tube with discrete and continuous characteristic fins according to claim 1, characterized in that: The cutting depth of the finning tool (2) on the base pipe (1) is 0.2-5 mm.

5. The method for processing an integral external finned tube with discrete and continuous characteristic fins according to claim 1, characterized in that: The base tube (1) is made of a heat-conducting metal material or a heat-conducting polymer material.

6. The method for processing an integral external finned tube with discrete and continuous characteristic fins according to any one of claims 1 to 5, characterized in that: The wing forming tool (2) comprises a main cutting edge (21), a front cutting surface (23), a secondary cutting edge (24) and a secondary flank surface (25); the secondary cutting edge (24) is transitionally arranged between the front cutting surface (23) and the secondary flank surface (25).

7. The method for processing an integral external finned tube with discrete and continuous characteristic fins according to claim 6, characterized in that: The radius of the secondary cutting edge (24) is 0.1-2.0 mm.

8. The method for processing an integral external finned tube with discrete and continuous characteristic fins according to claim 7, characterized in that: The included angle between the secondary cutting edge (24) and the feed direction is a secondary deflection angle, and the magnitude of the secondary deflection angle is 90°; the included angle between the secondary flank face (25) and the base face is a back angle, and the magnitude of the back angle is 5°; the included angle between the secondary flank face (25) and the secondary cutting edge (24) is a secondary back angle, and the magnitude of the secondary back angle is 5°.

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