Heat exchange tube, heat exchanger and method for manufacturing heat exchange tube

Abstract

The application relates to a heat exchange pipe, a heat exchanger and a manufacturing method of the heat exchange pipe. The heat exchange pipe comprises a pipe body and a twisted belt inserted into the pipe body. The twisted belt extends along the axial direction of the pipe body and forms multiple pitch sections. The twisted belt has a first surface and a second surface opposite to each other. The first surface of each pitch section is provided with multiple first convexes and multiple first concaves arranged at intervals. The application can further reduce the heat transfer resistance of the heat exchange pipe and improve the heat exchange coefficient.

Description

Technical Field

[0001] This application relates to the field of heat exchange equipment technology, and in particular to a method for manufacturing a heat exchange tube, a heat exchanger, and a heat exchange tube. Background Technology

[0002] According to fluid mechanics theory, based on the Reynolds number (Re) of different fluids, flow is classified into two completely different states: laminar flow and turbulent flow. When the fluid viscosity is high or the fluid velocity is low, the Re number is low, and the flow state is laminar. Conversely, when the Re number is high, the flow is turbulent. Through calculation and experiments, it was found that in the laminar flow state of a circular pipe, during heat exchange with the outside, the temperature on the cross-section follows a parabolic distribution along the radial direction, with the highest temperature appearing on the pipe axis, and the thermal resistance distributed throughout the entire pipe cross-section. When the fluid inside the pipe is in a turbulent state, during heat exchange with the outside, the temperature distribution on the cross-section follows a power function distribution along the radial direction, that is, the temperature in the core region is approximately perpendicular to the flow direction along the radial direction, and its thermal resistance is very small; while near the wall, the temperature drops sharply, and the thermal resistance is mainly concentrated near the wall.

[0003] Based on the above analysis, different methods are needed to enhance heat transfer for laminar or turbulent flow. For example, in turbulent flow, rough elements or grooves need to be installed on the wall to disrupt the boundary layer and improve heat transfer efficiency; in laminar flow, the fluid throughout the pipe needs to be mixed to reduce the radial temperature difference and decrease thermal resistance, thereby improving heat transfer efficiency.

[0004] The technology disclosed in Chinese patent CN2137327Y involves placing a spiral coil inside a heat exchange tube, with the coil's outer diameter equal to the tube's inner diameter. Through the action of the spiral coil, the tangential component of the rotation within the tube and the pulsation of molecules in the flow cluster are increased, disrupting the laminar boundary layer at the tube wall, reducing heat transfer resistance, and improving the heat transfer coefficient. Under high Reynolds number conditions, this can enhance heat transfer by more than 100%; however, at low Reynolds numbers, the effect is not significant.

[0005] Chinese patent CN2466592Y proposes using corrugated tubes, spiral grooved tubes, or T-grooved tubes as heat transfer tubes for heat exchangers. By disrupting the boundary layer through the disturbance of the non-smooth wall surface, the heat transfer coefficient is improved, achieving an enhancement effect of 1.8–2.0 times compared to smooth tubes. Besides setting rough elements on the wall surface to disrupt the boundary layer and improve the heat transfer coefficient, other technologies also use inserts within the heat exchange tube to alter the flow field in the core region and the boundary layer, thereby increasing the heat transfer coefficient.

[0006] Chinese Patent CN 202734652 U discloses a twisted grid component for enhancing fluid heat transfer when inserted into a heat transfer tube. The component includes twisted grids and helical coils. Each twisted grid passes through the central axis of the heat transfer tube, and both ends of each grid are welded to the helical coil. Multiple grids are arranged in a helical pattern. The beneficial effect is that the helical arrangement of the grids causes the fluid inside the heat transfer tube to rotate continuously and be constantly divided and disturbed, promoting thorough mixing of the fluid at the center and in the boundary layer, and creating a scouring effect on the inner wall, thereby enhancing heat transfer efficiency.

[0007] The technology disclosed in Chinese patent CN101846469A involves setting twisted plates in a heat exchange tube, with multiple twisted plates arranged along the axial direction of the heat exchange tube. Because the twisted plates change the flow pattern, they intensify the turbulence, reduce the boundary layer thickness, and improve the heat transfer efficiency. However, under the action of this device, the flow resistance is relatively large, which affects the promotion of this technology.

[0008] In summary, different enhancement measures are employed to improve the heat transfer coefficient for different flow states. In turbulent flow, thermal resistance is concentrated near the pipe wall. Adding rough elements to the pipe wall surface, such as continuous ribs or grooves, increases the turbulence near the wall as the fluid passes through these rough elements, thereby reducing the thermal resistance between the fluid and the wall. In laminar flow, thermal resistance is distributed across the entire cross-section, requiring a modification to the flow field across the entire cross-section. A twisted zone is ideal in this case, as the rotational motion of the fluid increases the mixing of secondary flows and segments the flow boundary layer, reducing the thermal resistance of the flow cross-section and the boundary layer thermal resistance near the pipe wall, thus enhancing heat transfer. However, the various measures mentioned in the aforementioned patent literature still have room for improvement. Summary of the Invention

[0009] This application proposes a method for manufacturing a heat exchange tube, a heat exchanger, and a heat exchange tube, in order to further reduce the heat transfer resistance of the heat exchange tube and improve its heat transfer coefficient.

[0010] In a first aspect, this application proposes a heat exchange tube, including a tube body and a twisted band inserted into the tube body, the twisted band extending twistedly along the axial direction of the tube body and forming multiple pitch segments;

[0011] The twisted band has a first surface and a second surface facing away from each other, and each pitch segment has a plurality of first convex bulges and a plurality of first pits arranged at intervals on the first surface.

[0012] In one possible implementation, each of the pitch segments has a plurality of second convex bulges and a plurality of second recesses arranged at intervals on the second surface.

[0013] In one possible implementation, the twisted band is made of metal, and the positions of the plurality of first convex buds correspond one-to-one with the positions of the plurality of second recesses, and the positions of the plurality of first recesses correspond one-to-one with the positions of the plurality of second convex buds.

[0014] The first convex bulge on the first surface is formed by stamping the second recess on the second surface;

[0015] The second convex bulge on the second surface is formed by stamping the first recess into the first surface.

[0016] In one possible implementation, all the first bulges on the twisted band are arranged into a plurality of first bulge groups that are spaced apart sequentially along the axial direction, each first bulge group including at least two first bulges, the at least two first bulges being located at the same cross-section of the tube body;

[0017] All the first pits on the twisted band are arranged into a plurality of first pit groups spaced apart sequentially along the axial direction, each first pit group including at least two first pits, the at least two first pits being located at the same cross-section of the tube body;

[0018] The first convex hull group and the first concave pit group are arranged alternately along the axial direction.

[0019] In one possible implementation, the twisted band has a first side and a second side facing away from each other, wherein both the first side and the second side are disposed abutting against the inner surface of the tube body;

[0020] The twisted band divides the internal space of the tube into a first channel and a second channel that are separated from each other. The inner surface of the first channel includes the first surface, and the inner surface of the second channel includes the second surface.

[0021] In one possible implementation, the tube is a circular tube, the width of the twisted band is equal to the inner diameter of the tube, and the inner wall of the tube is a smooth inner wall.

[0022] At any cross-sectional position of the tube, the first side and the second side are located at both ends of the diameter of the tube.

[0023] Secondly, this application proposes a heat exchanger including the heat exchange tubes as described in the first aspect.

[0024] Thirdly, this application proposes a method for manufacturing a heat exchange tube as described in the first aspect, comprising:

[0025] Provide the tube body;

[0026] Provide the twisted band;

[0027] The twisted band is inserted into the tube.

[0028] In one possible implementation, providing the twisted band includes:

[0029] A long strip of metal is provided, wherein the metal strip has a third surface and a fourth surface facing away from each other;

[0030] The third surface is stamped to form a plurality of third recesses on the third surface and a plurality of third protrusions on the fourth surface; the fourth surface is stamped to form a plurality of fourth recesses on the fourth surface and a plurality of fourth protrusions on the third surface.

[0031] The metal strip is twisted around its length axis to obtain the twisted strip.

[0032] In one possible implementation, the provision of the elongated metal strip includes:

[0033] Provide scrap metal pipes;

[0034] The waste metal tube is flattened radially to make the inner wall of the waste metal tube fit together, thus obtaining the metal strip.

[0035] According to the heat exchange tube provided in this application, a tortuous band is inserted into the tube body, and each pitch segment of the tortuous band has bulges and pits on both sides. During operation, both the bulges and pits act as vortex generators, thereby generating vortices at their locations. Furthermore, the Karman vortex street generated by the bulges causes the velocity vector direction of the fluid entering the pits to deflect, and the rotational effect accelerates the fluid velocity entering the pits, thus inducing a larger rotational speed of the vortexes. The vortexes have a longer effect distance downstream, resulting in more thorough mixing of the fluid. Similarly, when the vortices generated by the pits sweep over the bulges, the resulting vortexes have a faster frequency and greater intensity, which is beneficial for disturbing the fluid. In addition, the tortuous band divides the tube channel into two intertwined spiral channels around the tube axis. When the fluid flows along the spiral channels, a radial secondary flow occurs, which can significantly increase the influence range of the aforementioned vortices and further reduce the thermal resistance of the channel cross-section. Thus, the bulges, pits, and spiral channels in the heat exchange tube work together to effectively reduce the thermal resistance of the channel cross-section and improve the heat exchange efficiency of the heat exchange tube.

[0036] According to the heat exchange tube manufacturing method provided in this application, a convex bulge can be obtained by punching a recess on one side of the metal strip. Then, the metal strip with the convex bulge and recess is twisted along its length to obtain the desired twisted strip. By selecting an appropriate metal strip width, the twisted strip can be automatically positioned in the middle of the tube when it is inserted into the circular tube. This process is simple and easy to implement. 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 structure of a heat exchange tube provided in an embodiment of this application when viewed along the axial direction.

[0039] Figure 2 yes Figure 1 A schematic diagram of the twisted band in the heat exchange tube;

[0040] Figure 3 yes Figure 2 Schematic diagram of sectional view along direction AA;

[0041] Figure 4 yes Figure 2 BB-direction sectional view;

[0042] Figure 5 yes Figure 2 CC-direction cross-sectional view;

[0043] Figure 6 yes Figure 2 Another structural schematic diagram of the twisted band shown.

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

[0045] F1 - Axis direction;

[0046] 1-tube body;

[0047] 2-Twisted band;

[0048] 201-First convex hull, 202-First concave pit, 203-Second convex hull, 204-Second concave pit, 200-Pitch segment;

[0049] 2a - First surface, 2b - Second surface, 2c - First side edge, 2d - Second side edge;

[0050] 3-First Channel;

[0051] 4-Second Channel. Detailed Implementation

[0052] 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.

[0053] 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.

[0054] Figures 1 to 6 An embodiment of this application illustrates a heat exchange tube, which includes a tube body 1 and a twisted band 2 inserted within the tube body 1. The twisted band 2 extends twistedly along the axial direction F1 of the tube body 1, forming a plurality of pitch segments 200. The twisted band 2 has a first surface 2a and a second surface 2b opposite to each other in its thickness direction. Each pitch segment 200 has a plurality of first protrusions 201 and a plurality of first recesses 202 arranged at intervals on its first surface 2a.

[0055] It should be noted that on the axial direction F1 of the tube body 1, one pitch segment 200 corresponds to a continuous length segment of the twisted belt 2 that is twisted by 180° (twisted by 180° at certain intervals). The twisted belt 2 has multiple pitch segments 200, which means that the twisted belt 2 is twisted by at least 360°.

[0056] In this embodiment, a tortuous band 2 with multiple pitch segments 200 is provided inside the pipe body 1, thereby creating two helical channels (i.e., the first channel 3 and the second channel 4 described below) around the pipe axis. During operation, when the fluid flows along these two helical channels, a radial secondary flow occurs, increasing the influence range of the vortex and helping to reduce the thermal resistance of the channel cross-section. Furthermore, the combination of pits and convex humps on the first surface 2a of each pitch segment 200 has a significant impact on the generation of vortices and downstream flow. Specifically:

[0057] The convex hull functions as a vortex generator. When fluid passes over the spherical convex hull, boundary layer separation occurs, generating a pair of symmetrical vortices rotating in opposite directions behind the convex hull. When the Reynolds number Re > 90, the vortices steadily and continuously alternately generate and detach, forming two rows of alternating, oppositely rotating vortices in the wake region, a phenomenon known in fluid dynamics as the Karman vortex street. The continuous shedding of vortices constantly entrains nearby fluid, increasing fluid mixing and resulting in a more uniform temperature field in the core region, thus reducing thermal resistance. Simultaneously, this alternating vortex flow causes a difference in instantaneous velocity between the fluids on either side of the spherical convex hull, leading to a difference in instantaneous pressure. This causes fluid vibration, which can influence the flow of the viscous sublayer of the boundary layer, improving heat transfer efficiency.

[0058] The concave area also functions as a vortex generator, inducing vortex structures to inject momentum into the core region of the flow cross-section. Through the collision of fluid particles, it reduces the radial velocity and temperature gradients, thereby decreasing the cross-sectional thermal resistance. As the fluid flows from upstream through the concave area, the sudden indentation of the wall draws the fluid near the wall into the concave. After entering the concave, some of the fluid forms a recirculation zone on the leeward side of the concave; the other part continues to flow forward, re-attaching to the windward side of the concave and continuing to move along the solid surface. Due to the coiling effect, the fluid entering the concave induces the formation of a pair of vortices, which then leave the concave from both sides and move downstream, mixing with the main flow.

[0059] Furthermore, the Karman vortex street generated by the convex hull deflects the velocity vector of the fluid entering the depression and, due to its rotational effect, accelerates the fluid velocity, thus inducing a larger vortex rotation speed. This results in a greater downstream influence distance and more thorough mixing of the fluid. Similarly, when the vortex generated by the depression passes over the convex hull, the resulting vortex has a faster frequency and greater intensity, which is beneficial for disturbing the fluid.

[0060] More importantly, while the vortices generated on both sides of the convex hull and those emerging from the pits are generally longitudinal vortices flowing along the tube axis, when the continuously twisted tortuous band 2 is inserted, the channels inside the heat exchange tube become two spiral channels around the tube axis. During the flow of fluid along these spiral channels, a radial secondary flow occurs, which significantly increases the influence range of the aforementioned vortices and further reduces the thermal resistance of the channel cross-section. Furthermore, at each cross-section of the spiral channel corresponding to the first surface 2a inside the heat exchange tube, one side is a tortuous band with convex hulls and pits, and the other side is a smooth semi-circular tube wall. This structural asymmetry further enhances the aforementioned radial secondary flow. In addition, the convex hulls and pits on the first surface 2a also cause the heat exchange liquid in the first channel to be thrown towards the inner surface of the tube body 1, which helps to increase the liquid-receiving area of ​​the heat exchange tube wall of the tube body 1. For example, when the heat exchange tube is placed horizontally, under the influence of the bulge, the pit, and the twisted first surface 2a, the inner surface of the tube at the top of the tube can also receive a certain amount of fluid from inside the tube, which helps to improve the heat exchange efficiency between the fluid inside the tube and the fluid outside the tube.

[0061] Therefore, the above design can reduce the thermal resistance of the spiral channel corresponding to the first surface 2a, thereby improving the heat exchange efficiency of the spiral channel.

[0062] Similarly, please see again Figure 2 In order to improve the heat exchange efficiency of the other spiral channel corresponding to the second surface 2b, this embodiment provides a plurality of second convex bulges 203 and a plurality of second recesses 204 arranged at intervals on the second surface 2b of each pitch segment 200.

[0063] Please continue reading Figure 2 and combined Figures 3 to 5 In this embodiment, the positions of the plurality of first convex bulges 201 correspond one-to-one with the positions of the plurality of second recesses 204, and the positions of the plurality of first recesses 202 correspond one-to-one with the positions of the plurality of second convex bulges 203. Thus, there is exactly one second recess 204 on the other side of each first convex bulge 201, and exactly one second convex bulge 203 on the other side of each first recess 202. Therefore, if in practical applications there is a temperature difference between the fluids in the two spiral channels inside the pipe (uneven temperature distribution of the fluid inside the pipe will affect the overall heat exchange efficiency between the fluid inside and outside the pipe), then the one-to-one correspondence of the convex bulges and recesses between these two spiral channels allows the fluids in the two channels to exchange heat quickly, thereby reducing the aforementioned temperature difference and improving the overall heat exchange efficiency between the fluid inside and outside the pipe.

[0064] In this embodiment, the twisted band 2 is made of metal, and further, the twisted band 2 is made from a waste metal tube that has been flattened radially. The first convex bulge 201 on the first surface 2a is formed by stamping a second recess 204 on the second surface 2b. The second convex bulge 203 on the second surface 2b is formed by stamping a first recess 202 on the first surface 2a.

[0065] In accordance with the above description, in order to better cooperate with the convex bulge and the concave bulge and enhance the disturbance effect on the fluid inside the pipe, in this embodiment, the first convex bulge 201 and the first concave bulge 202 are arranged alternately along the axial direction F1, and the second convex bulge 203 and the second concave bulge 204 are also arranged alternately along the axial direction F1.

[0066] Specifically, all the first convex hulls 201 on the twisted band 2 are arranged into multiple groups of first convex hulls spaced apart sequentially along the axial direction F1, and each group of first convex hulls includes at least two first convex hulls 201. Figure 2 (There are two in the middle), the at least two first convex bulges 201 are located at the same cross-section of the tube body 1. All the first pits 202 on the twisted band 2 are arranged into a plurality of first pit groups spaced apart sequentially along the axial direction F1, each first pit group 202 including at least two first pits 202 ( Figure 2 (There are two in the middle), the at least two first recesses 202 are located at the same cross-section of the tube body 1. The first convex bulge group and the first recess group are arranged alternately along the axial direction F1.

[0067] In this embodiment, the width of the twisted band 2 is approximately equal to the inner diameter of the tube 1. Specifically, the twisted band 2 has a first side 2c and a second side 2d that are opposite to each other in its width direction. The first side 2c connects to one side of the first surface 2a and the second surface 2b, and the second side 2d connects to the other side of the first surface 2a and the second surface 2b. Both the first side 2c and the second side 2d are disposed abutting against the inner surface of the tube 1. Based on this, the twisted band 2 divides the internal space of the tube 1 into a first channel 3 and a second channel 4 that are separated from each other. The inner surface of the first channel 3 includes the first surface 2a (i.e., the first surface 2a is a part of the inner surface of the first channel 3), and the inner surface of the second channel 4 includes the second surface 2b. Since the first surface 2a and the second surface 2b are spiral surfaces, both the first channel 3 and the second channel 4 can be referred to as spiral channels. Therefore, it can prevent fluid from flowing between the two spiral channels in the tube body 1, which would weaken the radial secondary flow, thus ensuring the structural and functional independence of each spiral channel, so that the fluid in each spiral channel can well exhibit the flow pattern mentioned above.

[0068] Please see Figure 1 and combined Figure 2 as well as Figures 3 to 5At any cross-sectional position of the tube body 1, the first side 2c and the second side 2d are located at both ends of the diameter of the tube body 1, respectively. This ensures that the flow area of ​​the two spiral channels is equal and uniform throughout.

[0069] In some embodiments, in order to secure the position of the twisted band 2 inside the tube body 1, the end of the twisted band 2 can be welded and fixed to the tube body 1.

[0070] The dimensional parameters of the tube body 1 and the twisted band 2 can be flexibly selected as needed. For example, in one embodiment, the inner diameter of the tube body 1 and the width of the twisted band 2 are both 19 mm, the thickness of the twisted band 2 is 1.0 mm, the pitch of the twisted band 2 (i.e., the length of a single pitch segment 200) is 38 mm, i.e., the twist rate Y = 2, the diameter of the first recess 202 and the second recess 204 are both 1.9 mm, the depth is 3.8 mm, the height of the first convex 201 and the second convex 203 are both 4.8 mm, the radial distance between two adjacent convex ...

[0071] Furthermore, this embodiment also proposes a method for manufacturing the above-mentioned heat exchange tube, which includes the following steps:

[0072] S101, provides pipe body 1;

[0073] S102, provides 2 twisted bands;

[0074] S103, insert the twisted belt 2 into the tube body 1.

[0075] In some implementations, step S102 may specifically include the following sub-steps:

[0076] S102a provides an elongated metal strip, wherein the metal strip has a third surface and a fourth surface facing away from each other.

[0077] In some embodiments, the elongated metal strip can be obtained by cutting a thin metal sheet. In other embodiments, a rolling mill can be used to completely flatten the waste metal tube radially so that the inner wall of the waste metal tube fits together, thereby obtaining an elongated double-layer structure (two layers tightly attached) metal strip. The waste metal tube can be a discarded heat exchange tube or a common iron flue pipe, etc. The metal strip has two opposing surfaces, namely the third and fourth surfaces mentioned above, wherein the third surface corresponds to the first surface 2a of the twisted strip 2 in the final heat exchange tube, and the fourth surface corresponds to the second surface 2b of the twisted strip 2 in the final heat exchange tube.

[0078] S102b, stamping the third surface to form multiple third pits on the third surface and multiple third convex humps on the fourth surface; stamping the fourth surface to form multiple fourth pits on the fourth surface and multiple fourth convex humps on the fourth surface, the fourth pits corresponding to the second pits 204 and the fourth convex humps corresponding to the first convex humps 201.

[0079] Multiple third recesses can be stamped on the third surface and multiple fourth recesses on the fourth surface of the metal strip using a stamping device. Incidentally, multiple third and fourth protrusions are also formed on the fourth surface of the metal strip. The third protrusions correspond to the second protrusion 203 of the twisted band 2 in the final heat exchanger tube, the third recesses correspond to the first recess 202 of the twisted band 2 in the final heat exchanger tube, the fourth protrusions correspond to the first protrusion 201 of the twisted band 2 in the final heat exchanger tube, and the fourth recesses correspond to the second recess 204 of the twisted band 2 in the final heat exchanger tube.

[0080] S102c, the metal strip is twisted around its length axis to obtain twisted strip 2.

[0081] In this embodiment, a recess is punched into one side of a metal strip, thereby creating a bulge on the other side. The metal strip with the bulge and recess is then twisted along its length to obtain the desired twisted strip 2. The resulting recess and bulge both play a positive role in the final heat exchange tube. The process is simple and easy to implement.

Claims

1. A heat exchange tube, comprising a tube body, characterized in that, It also includes a twisted band inserted into the tube body, the twisted band extending twistedly along the axial direction of the tube body and forming multiple pitch segments; The twisted band has a first surface and a second surface facing away from each other. Each pitch segment has a plurality of first convex bulges and a plurality of first pits arranged at intervals on the first surface. The twisted band divides the internal space of the tube into a spiral first channel and a second channel that are spaced apart from each other and intertwined around the tube axis. The inner surface of the first channel includes the first surface, and the inner surface of the second channel includes the second surface. All the first convex buds on the twisted band are arranged into a plurality of first convex bud groups that are spaced apart sequentially along the axis, and each first convex bud group includes at least two first convex buds, the at least two first convex buds being located at the same cross-section of the tube body; All the first pits on the twisted band are arranged into a plurality of first pit groups spaced apart sequentially along the axial direction, each first pit group including at least two first pits, the at least two first pits being located at the same cross-section of the tube body; The first convex hull group and the first concave pit group are arranged alternately along the axial direction.

2. The heat exchange tube according to claim 1, characterized in that, Each of the pitch segments has a plurality of second convex bulges and a plurality of second recesses arranged at intervals on its second surface.

3. The heat exchange tube according to claim 2, characterized in that, The twisted band is made of metal, and the positions of the plurality of first convex buds correspond one-to-one with the positions of the plurality of second recesses, and the positions of the plurality of first recesses correspond one-to-one with the positions of the plurality of second convex buds; The first convex bulge on the first surface is formed by stamping the second recess on the second surface; The second convex bulge on the second surface is formed by stamping the first recess into the first surface.

4. The heat exchange tube according to any one of claims 1 to 3, characterized in that, The twisted band has a first side and a second side facing away from each other, wherein both the first side and the second side are disposed against the inner surface of the tube.

5. The heat exchange tube according to claim 4, characterized in that, The tube is circular, the width of the twisted band is equal to the inner diameter of the tube, and the inner wall of the tube is smooth. At any cross-sectional position of the tube, the first side and the second side are located at both ends of the diameter of the tube.

6. A heat exchanger, characterized in that, Includes the heat exchange tube as described in any one of claims 1 to 5.

7. A method for manufacturing a heat exchange tube as described in any one of claims 1 to 5, characterized in that, include: Provide the tube body; Provide the twisted band; The twisted band is inserted into the tube.

8. The manufacturing method according to claim 7, characterized in that, Providing the twisted band includes: A long strip of metal is provided, wherein the metal strip has a third surface and a fourth surface facing away from each other; The third surface is stamped to form a plurality of third recesses on the third surface and a plurality of third protrusions on the fourth surface; the fourth surface is stamped to form a plurality of fourth recesses on the fourth surface and a plurality of fourth protrusions on the third surface. The metal strip is twisted around its length axis to obtain the twisted strip.

9. The manufacturing method according to claim 8, characterized in that, The provided elongated metal strip includes: Provide scrap metal pipes; The waste metal tube is flattened radially to make the inner wall of the waste metal tube fit together, thus obtaining the metal strip.

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