Internally threaded heat exchange tube and manufacturing apparatus and method therefor

Abstract

This application relates to an internally threaded heat exchange tube and its manufacturing equipment and method. The internally threaded heat exchange tube includes: a tube body, and a helical rack disposed on the inner surface of the tube body and extending in a helical direction; the internally threaded heat exchange tube further includes a plurality of Z-shaped protrusions disposed on the top of the helical rack and spaced apart along the length direction of the helical rack, each Z-shaped protrusion including a first horizontal bar and a second horizontal bar spaced apart, and a diagonal bar connecting one end of the first horizontal bar and one end of the second horizontal bar, the first horizontal bar and the diagonal bar being disposed at a first angle, the second horizontal bar and the diagonal bar being disposed at a second angle, both the first angle and the second angle being acute angles.

Description

Technical Field

[0001] This application relates to a heat exchange tube, and more particularly to an internally threaded heat exchange tube and its manufacturing equipment and method. Background Technology

[0002] Dry evaporators are widely used in the air conditioning and refrigeration industry, as well as in the food, pharmaceutical, and chemical industries. In a dry evaporator, heat exchange tubes are typically arranged horizontally. Liquid refrigerant flows into the tubes from one end and, during its flow, continuously exchanges heat with the external hot fluid, undergoing a phase change and transforming from liquid to vapor. The vapor then flows out from the other end of the tube. According to heat transfer theory, this process—where liquid flows into the tube, is heated by the external fluid, and then vaporizes and flows out—is called flow boiling heat transfer. Through long-term research into the working mechanism of flow boiling, it is generally understood that the heat transfer mechanism of flow boiling involves two mechanisms: convective heat transfer and nucleated boiling heat transfer, which superimpose and act in a certain proportion.

[0003] To date, the main method for enhancing heat transfer in tube flow boiling is through machining various forms of spiral ribs (teeth) on the inner surface. Chinese patent application CN85103367A was the earliest to propose setting threads on the inner surface, with each spiral ridge having a triangular or trapezoidal cross-sectional shape, and the ratio of the cross-sectional area of ​​each threaded portion to the thread depth ranging from 0.15 to 0.40. Building upon this patent, Chinese patent CN2539948Y provides an internally threaded tube with regularly / irregularly spaced cut-ridge grooves along the spiral tooth ridges on the inner surface, forming discontinuous spiral teeth, commonly known as an intermittent-tooth internally threaded tube. Chinese patent CN201340220Y also proposes an internally threaded tube whose spiral teeth include main teeth and auxiliary teeth, with the auxiliary teeth distributed on the bottom wall between adjacent main teeth, their height less than half that of the main teeth, commonly known as a high-low tooth internally threaded tube. Furthermore, Chinese patent CN2548109Y discloses an internally threaded pipe with helical teeth on its inner surface, comprising main and auxiliary teeth. The main and auxiliary teeth have different thread directions, the center lines of the auxiliary teeth intersect with those of the main teeth, and the auxiliary teeth penetrate the bottom of the main teeth, forming an intersecting mesh-like pattern of teeth, commonly known as a cross-tooth internally threaded pipe. There are many other patent documents with similar helical teeth.

[0004] The helical teeth on the inner surface of the heat exchange tube and the grooves between adjacent helical teeth effectively enhance flow boiling. This improves heat transfer efficiency in both convective heat transfer and nucleated boiling. According to the boundary layer theory of fluid mechanics, a viscous sublayer, a transition zone, and a turbulent core region exist sequentially along the direction perpendicular to the wall. The maximum thermal resistance occurs in the viscous sublayer. Within the viscous sublayer, the transfer of matter and energy occurs only through molecular vibrations. The helical teeth on the surface promote collisions of fluid micro-clusters within the viscous sublayer, increasing the transport capacity of matter and energy and altering the temperature distribution within the viscous sublayer, thus improving the efficiency of convective heat transfer. However, there is still room for further improvement. Summary of the Invention

[0005] The technical problem solved by this application is to provide an internally threaded heat exchange tube and its manufacturing equipment and method, which can improve the heat exchange efficiency of the heat exchange tube.

[0006] The technical solution of this application is:

[0007] In a first aspect, this application proposes an internally threaded heat exchange tube, comprising:

[0008] tube body, and

[0009] A helical rack is disposed on the inner surface of the tube body and extends in the helical direction;

[0010] The internally threaded heat exchange tube is characterized in that it further includes a plurality of Z-shaped protrusions disposed on the top of the helical rack and spaced apart along the length of the helical rack. Each Z-shaped protrusion includes a first horizontal bar and a second horizontal bar spaced apart, and a diagonal bar connecting one end of the first horizontal bar and one end of the second horizontal bar. The first horizontal bar and the diagonal bar are arranged at a first angle, and the second horizontal bar and the diagonal bar are arranged at a second angle. Both the first angle and the second angle are acute angles.

[0011] In some possible implementations, the first horizontal bar and the second horizontal bar are arranged in parallel, and the first horizontal bar and the second horizontal bar are spaced apart along the length direction of the helical rack, and both extend in a direction perpendicular to the length of the helical rack.

[0012] In some possible implementations, both the first acute angle and the second acute angle are 35°-45°.

[0013] In some possible implementations, the height of the Z-shaped protrusion from the helical rack is 0.1-0.4 mm, the length of the Z-shaped protrusion in the extending direction of the helical rack is 0.3-0.8 mm, the width of the Z-shaped protrusion perpendicular to the extending direction of the helical rack is 0.25-0.6 mm, and the distance between any two adjacent Z-shaped protrusions is 0.5-1.5 mm.

[0014] Any two adjacent Z-shaped protrusions are spaced apart to form a through groove that runs through the helical rack.

[0015] Secondly, this application provides a manufacturing apparatus for manufacturing internally threaded heat exchange tubes as described in the first aspect, said manufacturing apparatus comprising:

[0016] A positioning sleeve having a cylinder axis and a first inner hole extending through the positioning sleeve in the direction of extension of the cylinder axis, the positioning sleeve being used to be inserted into the tube body of an internally threaded heat exchange tube to be manufactured;

[0017] A first forming head is sleeved on the positioning sleeve and located inside the tube, and is configured to be able to rotate relative to the positioning sleeve about the tube axis but not to move along the tube axis. The first forming head is used to press the tube body on the outer periphery, thereby forming a helical rack on the inner surface of the tube body.

[0018] The second forming head is fastened to the first forming head and located inside the tube, and has a second inner hole that is coaxial with and through the cylinder axis. The outer peripheral surface of the second forming head has a plurality of Z-shaped recesses arranged around the cylinder axis. The second forming head is used to press the helical rack to the outer peripheral side, and forms Z-shaped protrusions on the helical rack due to the action of the Z-shaped recesses.

[0019] A push-pull rod is inserted into the first inner hole in such a way that it can reciprocate along the extension direction of the cylinder axis, and one end of the push-pull rod has a tapered head located in the second inner hole;

[0020] When the conical head moves toward the first inner hole under the action of the push-pull rod, the conical head presses against the wall of the second inner hole on the outer periphery, causing the second forming head to undergo circumferential expansion deformation, thereby causing the second forming head to press against the helical rack on the outer periphery; when the conical head moves away from the first inner hole under the action of the push-pull rod, the second forming head returns to its original shape.

[0021] In some possible implementations, the second forming head has a plurality of expansion and contraction slits arranged around the cylinder axis, the plurality of Z-shaped recesses being arranged in a spiral direction around the cylinder axis.

[0022] In some possible implementations, the second forming head has a spiral flange that protrudes outwards, and the plurality of Z-shaped recesses are formed on the outer peripheral surface of the flange.

[0023] In some possible implementations, the manufacturing equipment further includes:

[0024] A spinning die is used to extrude the tube body from the periphery of the first forming head toward the inner circumference.

[0025] A shaping mold is used to support the tube body on the periphery of the second forming head;

[0026] A tube driving device is used to drive the tube to move along the extension direction of the cylinder axis;

[0027] A push-pull rod drive device is used to drive the push-pull rod to reciprocate in the extension direction of the cylinder axis.

[0028] In some possible implementations, the push-pull rod drive device includes a motor connected to the push-pull rod via a crank connection mechanism;

[0029] The outer peripheral surface of the large end of the cone-shaped head is a spiral surface.

[0030] Thirdly, this application proposes a manufacturing method, comprising:

[0031] The internally threaded heat exchange tube as described in the first aspect is manufactured using the manufacturing equipment described in the second aspect.

[0032] This application has at least the following beneficial effects:

[0033] 1. The Z-shaped protrusions on the top of the spiral rack in this application create two conical cavities that serve as vaporization cores. These conical cavities make it easier for the heat exchange liquid inside the tube to boil and vaporize after being heated, thereby improving the heat transfer coefficient of the heat exchange tube.

[0034] 2. The heat exchange tube of this application can form a vaporization core in the area of ​​the bottom of the spiral groove and the top of the spiral rack. When the bubbles at the bottom of the spiral groove detach from the wall and rise upward, they will merge and aggregate with the bubbles at the top of the spiral rack to form larger bubbles, which increases the buoyancy of the bubbles and accelerates the movement speed of the bubbles. Even if the bubbles at the top of the spiral rack do not grow to the size of the detachment diameter, they are carried away from the wall during the merging process with the bubbles generated at the root of the rack, thus increasing the frequency of bubble generation, shortening the growth time, and thereby improving the boiling heat transfer coefficient.

[0035] 3. For convective heat transfer, this application provides numerous Z-shaped protrusions at intervals on the top of the helical rack, changing the smooth state of the rack surface and obtaining a rough surface. When the fluid passes over the helical rack, the rough surface of the helical rack increases the disturbance to the fluid boundary layer, causing more collisions of fluid micro-particles, strengthening the flow state of the laminar sublayer, and improving the convective heat transfer efficiency.

[0036] 4. The manufacturing equipment provided in the second aspect and the manufacturing method provided in the third aspect of this application can easily produce heat exchange tubes as described in the first aspect. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this application, and are not intended to limit this application.

[0038] Figure 1 This is a schematic diagram of the internally threaded heat exchange tube in an embodiment of this application.

[0039] Figure 2 This is a partial enlarged view of the internally threaded heat exchange tube in the embodiments of this application, wherein the inner surface of the tube is facing the reader.

[0040] Figure 3 This is a comparison diagram of the heat transfer coefficients of the internally threaded heat exchange tube and the conventional smooth tube and conventional internally threaded heat exchange tube in the embodiments of this application.

[0041] Figure 4 This is a photograph of a specific embodiment of the threaded heat exchanger tube according to this application.

[0042] Figure 5 This is a schematic diagram of the manufacturing equipment for the internally threaded heat exchanger tube in the embodiments of this application.

[0043] Figure 6 yes Figure 5 A schematic diagram of the structure of the second forming head.

[0044] Explanation of reference numerals in the attached figures:

[0045] L-Cylinder axis, 1-Tube body, 2-Helical rack, 3-Helical groove, 4-Z-shaped protrusion, 4a-First horizontal bar, 4b-Second horizontal bar, 4c-Diagonal bar, 5-Through groove, 6-Positioning sleeve, 6a-First inner hole, 7-First forming head, 8-Second forming head, 8a-Z-shaped recess, 8b-Expansion / contraction joint, 8c-Second inner hole, 8d-Flange, 9-Push-pull rod, 10-Conical head, 11-Spinning die, 12-Shaping die. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the described embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. It is understood that, without conflict, some technical means of the various embodiments described herein can be substituted for or combined with each other.

[0047] In the description of this application and the claims, the terms "first," "second," etc., are used only to distinguish the described objects and have no sequential or technical meaning. Therefore, objects specified with "first," "second," etc., may explicitly or implicitly include one or more of those objects. Furthermore, the words "one" or "a" do not indicate a quantity limitation, but rather indicate the presence of at least one, while "multiple" indicates not less than two.

[0048] In the description of this application and the claims, the terms "connection," "installation," and "fixation," unless otherwise specified, should be interpreted broadly. For example, "connection" can mean a separate connection or an integral connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean a non-detachable connection or a detachable connection. Those skilled in the art can understand the specific meaning of the aforementioned terms in this application according to the specific circumstances.

[0049] In the description of this application and the claims, if terms such as "above," "below," or "horizontal" indicate orientation or positional relationships based on the orientation or positional relationships shown in the drawings, they are only for the purpose of clearly and simply describing this application, and do not indicate or imply that the elements referred to must have a specific orientation or be constructed and operated in a specific orientation. These directional terms are relative concepts used for relative description and clarification, and may change accordingly depending on the orientation of the components in the drawings. For example, if the device in the drawings is flipped, an element described as "below" other elements will be positioned "above" other elements.

[0050] Embodiments of this application will now be described with reference to the accompanying drawings.

[0051] Figure 1 and Figure 2A specific embodiment of the internally threaded heat exchange tube of this application is shown, comprising a tube body 1, the inner surface of which is provided with helical racks 2 extending in a helical direction. Multiple helical racks 2 are provided, arranged parallel to each other along the axial direction of the tube body 1, and helical grooves 3 are formed between adjacent helical racks 2 on the inner surface of the tube body 1, extending in a helical direction. This internally threaded heat exchange tube is particularly suitable for dry evaporators.

[0052] Nucleus boiling requires a large number of effective vaporization nuclei, and the more effective vaporization nuclei there are, the higher the boiling heat transfer efficiency. Visualization experiments revealed that the two bottom corner regions of the spiral groove 3 are ideal areas for the existence and growth of most vaporization nuclei. Therefore, the number of vaporization nuclei in the internally threaded heat exchanger tube far exceeds that of the smooth tube, and its boiling heat transfer coefficient is higher than that of the smooth tube. Generally, the overall heat transfer coefficient of the internally threaded heat exchanger tube can exceed that of the smooth tube by more than 1 times. However, it was also found that traditional internally threaded heat exchanger tubes are produced by arranging a mold inside the heat exchanger tube and extruding it outside. Therefore, the surface of the processed spiral rack 2 is smooth and solid, with few depressions and gaps, making it difficult for effective vaporization nuclei to grow. Vaporization nuclei are basically only present at the bottom corners of the spiral groove 3, and effective vaporization nuclei are not easily generated on the surface of the spiral rack 2.

[0053] The key improvement of this embodiment is that the internally threaded heat exchange tube further includes a plurality of Z-shaped protrusions 4 disposed on the top of the helical rack 2 and spaced apart along the length of the helical rack 2. The Z-shaped protrusions 4 include a first horizontal bar 4a and a second horizontal bar 4b spaced apart, and a diagonal bar 4c connecting one end of the first horizontal bar 4a and one end of the second horizontal bar 4b. The first horizontal bar 4a and the diagonal bar 4c are arranged at a first angle, and the second horizontal bar 4b and the diagonal bar 4c are arranged at a second angle. Both the first angle and the second angle are acute angles.

[0054] For pool boiling, also known as nucleus boiling, increasing the number and quality of effective vaporization nuclei is the main means to improve the boiling heat transfer coefficient. According to heat transfer theory, tiny cavities or cracks on the heat transfer surface are ideal locations for the generation and growth of vaporization nuclei. However, this is not absolute. For a cavity to become an activated vaporization nuclei, it must be able to store gas; otherwise, it is a dead cavity and cannot effectively form bubble nuclei. The most effective cavity geometry is a conical cavity, i.e., a cavity with an acute cone angle at the top and a large outlet. This is because at the tip of a conical cavity, the radius of curvature r of the gas-liquid interface can be arbitrarily small. Therefore, even a very small bubble pressure p can maintain a large liquid pressure at the gas-liquid interface, preventing liquid intrusion and permanently retaining a certain volume of vapor (gas), thus making it an activated cavity. In this embodiment, a Z-shaped protrusion 4 is provided on the top of the helical rack 2. The first horizontal bar 4a and the second horizontal bar 4b of the Z-shaped protrusion 4 are respectively set at acute angles with the diagonal bar, thereby constructing two conical cavities at the intersection of the diagonal bar 4c and the two horizontal bars—an acute-angled cavity between the first horizontal bar 4a and the diagonal bar 4c and an acute-angled cavity between the second horizontal bar 4b and the diagonal bar 4c, artificially constructing easily activated vaporization core cavities. These Z-shaped protrusions 4 are arranged on the top of the helical rack 2. During boiling, as bubbles are continuously generated and detach from the wall, the fluid near the wall is in an oscillating state, exhibiting a reciprocating purging phenomenon on the conical cavities. This conical cavity ensures that after the bubbles detach from the cavity, when the liquid rushes in, it does not completely squeeze out the residual gas (leaving a small amount of residual gas at the cone tip); when the liquid then exits, the gas at the cone tip is not completely carried away either. Therefore, the conical cavities will always remain in an activated state, increasing the number of effective vaporization cores. In contrast, conventional internally threaded tubes, due to the extrusion process used to manufacture the helical grooves 3 and the corresponding helical racks 2, have smooth and flat bottom surfaces with few gaps or voids. Therefore, vaporization nuclei can only appear at the corner area formed by the intersection of the bottom of the helical grooves 3 and the rack. However, this embodiment, like conventional internally threaded tubes, can also form a corner area at the root of the helical rack 2 and the bottom of the helical groove 3, thus obtaining vaporization nuclei. Furthermore, this embodiment also constructs multiple conical cavity structures with stronger vaporization capabilities by creating Z-shaped protrusions 4 on the top of the rack. Clearly, the number of activated cavities on the inner surface of the tube body 1 in this embodiment, including the bottom of the grooves and the top of the rack, is much greater than that in conventional internally threaded tubes and smooth tubes, resulting in a significant improvement in the boiling heat transfer coefficient.

[0055] More ingeniously, based on bubble dynamics, the bubble nuclei in the vaporization core cavity are continuously heated by the wall, gradually expanding in volume. When the bubble diameter grows to the critical detachment diameter, it detaches from the wall, completing the boiling process of a bubble. In this embodiment, the regions where vaporization cores can be formed include the bottom of the spiral groove 3 and the top of the spiral rack 2. Thus, when the bubbles at the bottom of the spiral groove 3 detach from the wall and rise upwards, they merge and aggregate with the bubbles at the top of the spiral rack 2 to form larger bubbles. Even if the bubbles at the rib top do not grow to the detachment diameter, they will be carried away from the wall quickly, thereby shortening the time required for the bubble boiling process in these areas and improving the boiling heat transfer coefficient.

[0056] In this embodiment, the first horizontal bar 4a and the second horizontal bar 4b of the Z-shaped protrusion 4 are arranged in parallel. Specifically, the first horizontal bar 4a and the second horizontal bar 4b are arranged at intervals along the length direction of the helical rack 2, and both extend in a direction substantially perpendicular to the length of the helical rack 2.

[0057] Through testing and verification, the first acute angle and the second acute angle mentioned above are preferably no more than 45°, and more preferably 35°-45°. The height of the Z-shaped protrusion 4 protruding from the helical rack 2 is preferably 0.1-0.4mm, the length of the Z-shaped protrusion 4 in the extending direction of the helical rack 2 is preferably 0.3-0.8mm, the width of the Z-shaped protrusion 4 in the direction perpendicular to the extending direction of the helical rack 2 is preferably 0.25-0.6mm, and the distance between any two adjacent Z-shaped protrusions 4 is preferably 0.5-1.5mm.

[0058] Please refer to Figure 2 The two adjacent Z-shaped protrusions 4 are spaced apart, so a through groove 5 is formed between the adjacent Z-shaped protrusions 4, which penetrates the helical rack 2.

[0059] The number of helical racks 2 on the inner surface of the tube body 1 should be 15-75, and the helix angle of each helical rack 2 should be 5°-45°.

[0060] The tube body 1 can be made of materials such as copper or aluminum. In this embodiment, the tube body 1 is made of copper, with a diameter of 9.52 mm and a wall thickness of 0.35 mm.

[0061] We conducted comparative experiments on the boiling heat transfer coefficients of the heat exchange tubes, ordinary smooth tubes, and conventional internally threaded tubes in this embodiment. Experimental conditions: the low-temperature refrigerant was R22, the inlet dryness fraction was 0.16–0.18, the outlet superheat was 3–5°C, the evaporation temperature was 5.8–6.0°C, and all tubes had the same diameter, wall thickness, material, and other parameters. Figure 3 As shown in the figure, the experimental results show that the boiling heat transfer coefficient of the heat exchange tube in this embodiment is 56-107% higher than that of the smooth tube and 25-37% higher than that of the conventional internally threaded tube.

[0062] Please see again. Figure 5 and Figure 6 This application embodiment also provides a manufacturing device that can be used to manufacture the internally threaded heat exchange tube with the above-mentioned structure. The device includes a positioning sleeve 6, a first forming head 7, a second forming head 8, a push-pull rod 9, a spinning die 11, a shaping die 12, and a tube body 1 driving device and a push-pull rod 9 driving device (not shown in the figure).

[0063] The positioning sleeve 6 has a cylinder axis L and a first inner hole 6a extending through the positioning sleeve 6 in the extension direction of the cylinder axis L. The positioning sleeve 6 is used to be inserted into the tube body 1 of the internally threaded heat exchange tube to be manufactured.

[0064] The first forming head 7 is sleeved on the positioning sleeve 6 and (in application) located inside the tube body 1. The first forming head 7 is configured to rotate relative to the positioning sleeve 6 about the cylinder axis L, but cannot move back and forth along the cylinder axis L. The first forming head 7 is used to press the tube body 1 outward to the outer periphery, thereby forming a helical rack 2 on the inner surface of the tube body 1. The structure of the first forming head 7 is well known and will not be described in detail here.

[0065] The second forming head 8 is securely connected to one end of the positioning sleeve 6 and (in application) located inside the tube body 1, having a second inner hole 8c coaxial with and penetrating the tube axis L. The outer peripheral surface of the second forming head 8 has a plurality of Z-shaped recesses 8a arranged around the tube axis L. The second forming head 8 is used to press the helical rack 2 outward, and due to the action of the Z-shaped recesses 8a, Z-shaped protrusions 4 are formed on the helical rack 2.

[0066] The push-pull rod 9 is inserted into the first inner hole 6a in a manner that allows it to reciprocate along the extension direction of the cylinder axis L, and one end of the push-pull rod 9 has a tapered head 10 located in the second inner hole 8c. Specifically, the tapered head 10 is fixed to the push-pull rod 9 by a lock nut. The wall surface of the right half of the second inner hole 8c can be a tapered curved surface that matches the tapered head 10.

[0067] When the conical head 10 moves toward the first inner hole 6a under the action of the push-pull rod 9, the conical head 10 presses the conical hole wall of the second inner hole 8c outwards, causing the second forming head 8 to undergo circumferential expansion deformation due to this pressure. This causes the second forming head 8 to press the helical rack 2 of the tube 1 outwards within the tube 1, thereby forming a Z-shaped protrusion 4 on the helical rack 2 using the Z-shaped recess 8a. When the conical head 10 moves away from the first inner hole 6a under the action of the push-pull rod 9, the conical head 10 disengages from the conical wall of the second inner hole 8c, and the second forming head 8 quickly returns to its original shape.

[0068] The second forming head 8 has multiple expansion and contraction slits 8b arranged around the cylinder axis L. The expansion and contraction slits 8b can improve the deformation capability of the second forming head 8, making it easier for the second forming head 8 to expand circumferentially under the extrusion of the aforementioned conical head 10.

[0069] The spinning die 11 is used to press the tube 1 inward from the periphery of the first forming head 7, so that the inner surface of the tube 1 can tightly abut against the outer peripheral surface of the first forming head 7. The shaping die 12 is used to support the tube 1 from the periphery of the second forming head 8, so that the inner surface of the tube 1 can tightly abut against the outer peripheral surface of the second forming head 8. The tube 1 driving device is used along the extension direction of the cylinder axis L (specifically... Figure 5 (From center to right) Pull tube 1. The push-pull rod 9 drive device is used to drive the push-pull rod 9 to move back and forth along the extension direction of the cylinder axis L.

[0070] Next, see Figure 5 and combined Figure 6 The following describes a method for manufacturing the heat exchange tube in more detail, which includes:

[0071] The heat exchanger tube body 1 to be manufactured is fitted onto the positioning sleeve 6, the first forming head 7, and the second forming head 8. Using a spinning die 11, the tube body 1 is rotated and pressed inwards from the periphery of the first forming head 7, thus pressing the inner surface of the tube body 1 tightly against the forming teeth on the outer circumferential surface of the first forming head 7. Simultaneously, the tube body 1 is pulled to the right by a tube body 1 driving device. Thus, as the tube body 1 moves to the right, it also rotates synchronously with the first forming head 7, extruding spiral grooves 3 and corresponding spiral racks 2 on the inner surface of the tube body 1. During the aforementioned actions, when the formed spiral rack 2 moves to the right to the position of the second forming head 8, the push-pull rod 9 driving device pulls the push-pull rod 9 to the left, causing the conical head 10 to press outwards against the second inner hole 8c of the second forming head 8. The second forming head 8 undergoes circumferential expansion deformation to press the spiral rack 2 outwards, forming a Z-shaped protrusion 4. When the second forming head 8 expands and compresses the helical rack 2, the tube body 1 driving device can briefly stop pulling the tube body 1 to the right. After forming the Z-shaped protrusion 4, the push-pull rod 9 driving device pushes the push-pull rod 9 to the right, and the conical head 10 stops compressing the second inner hole 8c. The second forming head 8 returns to its original shape due to its own elasticity. Subsequently, the tube body 1 continues to be pulled to the right, thereby forming new helical racks 2 inside the tube body 1. When the new helical rack 2 moves to the right to the position of the second forming head 8, the push-pull rod 9 driving device pulls the push-pull rod 9 to the left again, thereby forming the Z-shaped protrusion 4. This cycle continues until enough helical racks 2 with Z-shaped protrusions 4 are obtained inside the tube body 1.

[0072] In other embodiments, the tube 1 may also maintain a constant rightward movement without stopping its rightward movement when the second forming head 8 expands circumferentially. In this case, the rightward movement speed of the tube 1 should be slow enough.

[0073] To better correspond the arrangement of the Z-shaped recesses 8a on the second forming head 8 to the shape of the helical rack 2, the multiple Z-shaped recesses 8a on the second forming head 8 can be arranged in a helical direction around the cylinder axis L. Figure 6 For the sake of simplification, the schematic diagram does not explicitly show the spiral arrangement. When the Z-shaped recesses 8a on the second forming head 8 are arranged in a spiral direction, in order to ensure that each Z-shaped recess 8a undergoes a uniform outward expansion deformation during the aforementioned manufacturing process, the large end face of the conical head 10 ( Figure 5 The right end face of the cone head 10 is set to a spiral shape, and based on this, the outer peripheral surface of the large end of the cone head 10 is a spiral surface, and each part of the spiral surface is at the same distance from the central axis of the cone head 10.

[0074] Please see again. Figure 6 In order to prevent poor tube structure caused by other parts (non-Z-shaped recesses) of the second forming head 8 pressing against the inner wall of the tube body 1, especially the helical rack 2, during expansion and deformation, the second forming head 8 has a spiral flange protruding outwards, and the aforementioned multiple Z-shaped recesses 8a are all formed on the outer peripheral surface of the flange 8d.

[0075] In this embodiment, since the second forming head 8 is fastened to the first forming head 7, the second forming head 8 will rotate synchronously with the first forming head 7 and the tube 1 during the manufacturing process (but will not move to the right with the tube 1). Therefore, the second forming head 8, especially the various Z-shaped recesses 8a on it, will always remain relatively stationary with the tube 1 in the circumferential direction (only moving relative to each other in the axial direction). In this way, the expansion time of the second forming head 8 can be determined according to the pitch of the helical rack 2 and the rightward movement speed of the tube 1 (for example, the second forming head 8 expands once for every pitch movement of the tube 1). This ensures that the various Z-shaped recesses 8a on the second forming head 8 can be aligned with the helical rack 2 on the inner surface of the tube 1 and then squeezed each time.

[0076] The aforementioned push-pull rod 9 driving device can be a motor. The motor is connected to the push-pull rod 9 through a crank connecting mechanism. The crank connecting mechanism can convert the unidirectional rotational motion of the motor into the reciprocating linear movement of the push-pull rod 9.

[0077] The above are merely exemplary embodiments of this application and are not intended to limit the scope of protection of this application, which is determined by the appended claims.

Claims

1. A manufacturing apparatus for an internally threaded heat exchanger tube, the internally threaded heat exchanger tube comprising: tube body, and A helical rack is disposed on the inner surface of the tube body and extends in the helical direction; The internally threaded heat exchange tube is characterized in that it further includes a plurality of Z-shaped protrusions disposed on the top of the helical rack and spaced apart along the length of the helical rack. Each Z-shaped protrusion includes a first horizontal bar and a second horizontal bar spaced apart, and a diagonal bar connecting one end of the first horizontal bar and one end of the second horizontal bar. The first horizontal bar and the diagonal bar are arranged at a first angle, and the second horizontal bar and the diagonal bar are arranged at a second angle. Both the first angle and the second angle are acute angles of 35°-45°. The manufacturing equipment includes: A positioning sleeve having a cylinder axis and a first inner hole extending through the positioning sleeve in the direction of extension of the cylinder axis, the positioning sleeve being used to be inserted into the tube body of an internally threaded heat exchange tube to be manufactured; A first forming head is sleeved on the positioning sleeve and located inside the tube, and is configured to be able to rotate relative to the positioning sleeve about the tube axis but not to move along the tube axis. The first forming head is used to press the tube body outward to the outer periphery, thereby forming a helical rack on the inner surface of the tube body. The second forming head is fastened to the first forming head and located inside the tube, and has a second inner hole that is coaxial with and through the cylinder axis. The outer peripheral surface of the second forming head has a plurality of Z-shaped recesses arranged around the cylinder axis. The second forming head is used to press the helical rack to the outer peripheral side, and forms Z-shaped protrusions on the helical rack due to the action of the Z-shaped recesses. A push-pull rod is inserted into the first inner hole in such a way that it can reciprocate along the extension direction of the cylinder axis, and one end of the push-pull rod has a tapered head located in the second inner hole; A spinning die is used to extrude the tube body from the periphery of the first forming head toward the inner circumference. A shaping mold is used to support the tube body on the periphery of the second forming head; The second forming head has a plurality of expansion and contraction slits arranged around the cylinder axis, and the plurality of Z-shaped recesses are arranged in a spiral direction around the cylinder axis; When the conical head moves toward the first inner hole under the action of the push-pull rod, the conical head presses against the wall of the second inner hole on the outer periphery, causing the second forming head to undergo circumferential expansion deformation, thereby causing the second forming head to press against the helical rack on the outer periphery; when the conical head moves away from the first inner hole under the action of the push-pull rod, the second forming head returns to its original shape.

2. The manufacturing equipment according to claim 1, characterized in that, The second forming head has a spiral flange that protrudes outwards, and the plurality of Z-shaped recesses are formed on the outer peripheral surface of the flange.

3. The manufacturing equipment according to claim 1, characterized in that, The manufacturing equipment also includes: A tube driving device is used to drive the tube to move along the extension direction of the cylinder axis; A push-pull rod drive device is used to drive the push-pull rod to reciprocate in the extension direction of the cylinder axis.

4. The manufacturing equipment according to claim 3, characterized in that, The push-pull rod drive device includes a motor, which is connected to the push-pull rod via a crank connection mechanism; The outer peripheral surface of the large end of the cone-shaped head is a spiral surface.

5. A method for manufacturing an internally threaded heat exchanger tube, characterized in that, include: The internally threaded heat exchange tube is manufactured using the manufacturing equipment as described in any one of claims 1 to 4.

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