Metal heat exchanger tube

Abstract

This invention relates to a metal heat exchanger tube (1) comprising integral fins (2) formed on the outer side of the tube, having a fin bottom (3), fin side wings (4), and fin top (5), wherein the fin bottom (3) protrudes radially from the tube wall (10) and forms a channel (6) between the fins (2), the channel having a channel base (61) and additional structures (7, 71, 72) arranged spaced apart from each other in the channel. The additional structures (7, 71, 72) divide the channel (6) between the fins (2) into segments (8). The first additional structures (7, 71) are protrusions (71) that start from the channel base (61) and point radially outward. Radially outwardly positioned material protrusions (72) are arranged at the locations of the protrusions (71) as second additional structures (7, 72). The heat exchanger tube of the present invention has improved performance for liquids evaporating on the outer side of the tube.

Description

Technical Field

[0001] This invention relates to metal heat exchanger tubes. Background Technology

[0002] Evaporation occurs in many sectors of refrigeration and air conditioning engineering, as well as process and power engineering. Tubular heat exchangers are frequently used, in which a liquid evaporates from a pure substance or mixture on the outside of the tubes, and in the process, brine or water is cooled on the inside of the tubes.

[0003] By intensifying heat transfer on both the outer and inner sides of the tubes, the size of the evaporator can be significantly reduced. This lowers the production cost of the device. Furthermore, it reduces the amount of refrigerant required, which is important given that the predominantly used chlorine-free, safe refrigerant can constitute a substantial portion of the total equipment cost. Moreover, modern high-power tubes are now approximately four times more efficient than smooth tubes of the same diameter.

[0004] The highest performance commercially available finned tubes for overflow evaporators have a finned structure on the outer side of the tube with a fin density of 55 to 60 fins / inch (US 5,669,441 A; US 5,697,430 A; DE 197 57 526C1). This corresponds to a fin spacing of approximately 0.45 mm to 0.40 mm.

[0005] Furthermore, it is known that an improved evaporation structure can be manufactured by introducing additional structural elements in the region at the bottom of the groove between the fins, wherein the fin spacing remains the same on the outside of the tube.

[0006] EP 1 223 400 B1 proposes creating undercut secondary grooves at the bottom of the grooves between fins, the secondary grooves extending continuously along the main grooves. The cross-section of the secondary grooves may remain constant or may vary at regular intervals.

[0007] Other examples of structures on the bottom of the groove can be found in EP 0 222 100 B1, US 7,254,964 B2, or US 5,186,252 A. A common feature of these structures is that the structural elements do not have an undercut shape on the bottom of the groove. These are indentations introduced into the bottom of the groove, or protrusions in the lower region of the channel. Higher protrusions are clearly excluded in the prior art, as there seems to be concern that fluid flow in the channel would be adversely blocked for heat exchange.

[0008] EP 3 111 153 B1 discloses another method with higher structures emerging from the bottom of the groove. These structures are protrusions in the segmented channel. By segmenting between two fins, the channel is repeatedly interrupted in the circumferential direction, thus at least reducing or completely preventing the migration of heat exchange fluids and bubbles in the channel. The exchange of liquid and vapor along the channel becomes less and less, or even no longer facilitated by the corresponding additional structures. Summary of the Invention

[0009] The purpose of this invention is to develop a heat exchanger tube with improved performance for evaporating liquid on the outside of the tube.

[0010] The invention includes a metal heat exchanger tube comprising an integral fin formed on the outer side of the tube, the integral fin having a fin base, fin sidewalls, and fin tip, wherein the fin base projects radially from the tube wall and forms a channel with a channel base between the fins, wherein additional structures spaced apart by the channel are arranged in the channel. The additional structures segment the channel between the fins. The additional structures locally reduce the flow cross-sectional area in the channel between two fins, and thereby at least restrict fluid flow in the channel during operation. A first additional structure is a radially outwardly pointing protrusion arising from the channel base and each being defined radially by an end surface located between the channel base and the fin tip, thus defining the radial extent of the protrusion. A material protrusion in the form of a second additional structure is arranged radially outwardly at the location of the protrusion, formed by material from the fin sidewalls. Each material protrusion is arranged radially between the end surface and the fin tip, such that the material protrusion is formed laterally on the fin sidewalls via the channel base of the channel, around the protruding radial extent. The material protrusions extend further in the axial and radial directions than in the circumferential direction.

[0011] These metal heat exchanger tubes are specifically designed for evaporating liquids from pure substances or mixtures on the outside of the tubes.

[0012] This type of high-efficiency tube can be manufactured based on integrally rolled finned tubes using a rolling mill. Integrally rolled finned tubes are understood to refer to finned tubes in which fins have been formed from the wall material of a smooth tube. Typical integral fins formed on the outer side of the tube are, for example, spirally wound and have a fin base, fin sidewalls, and fin tips, wherein the fin base protrudes substantially radially from the tube wall. The number of fins is determined by counting the successive protrusions in the axial direction of the tube. The structure according to the invention can be manufactured using a sharp-edged rolling mill that forms both the wall material at the channel base and the material on the fin sidewalls in both the axial and radial directions.

[0013] Various methods are known here in which channels between adjacent fins are closed in such a way that the connection between the channel and the surrounding environment remains in the form of a pore or slit. In particular, such essentially closed channels are created by bending or folding the fins, by splitting and upsetting the fins, or by slotting and upsetting the fins.

[0014] This invention is based on the following consideration: to increase heat transfer during evaporation, the intermediate space of the fins is additionally segmented. This method generates localized superheating in the intermediate space, enhancing the nucleation and boiling process. Bubble formation then primarily occurs within the segments and begins at nucleation sites. At these nucleation sites, small gas or vapor bubbles initially form. When the grown bubble reaches a certain size, it detaches from the surface. During bubble detachment, the remaining cavity in the segment is again submerged in liquid, and the cycle restarts. The surface can be constructed such that when a bubble detaches, the small bubble remains behind it, which then serves as a nucleation site for the cycle of new bubble formation.

[0015] In addition to forming bubbles within the segments, according to the solution of the invention, additional material protrusions, in the form of a second additional structure, are located in the region of the first additional structure as radially outward-pointing protrusions. The material protrusions are arranged laterally on the fin sidewalls and extend substantially in both the axial and radial directions. From a manufacturing method using rollers, the material protrusions are formed from material on the fin sidewalls and are preferably positioned radially outward directly at the protrusions. In the structure formed by the material protrusions, the flow of liquid heat exchanger fluid directly into adjacent segments from the sides is assisted as before. Therefore, this fluid guidance facilitates the formation of bubbles within the segments. The protrusions may extend axially between the respective fin bottoms of adjacent fins, either over the entire channel substrate or only on a portion of the channel substrate. They constitute a barrier that travels radially outward from the channel substrate between the two fins and at least partially closes the channel in the circumferential direction.

[0016] In other words, the material protrusions according to the invention, placed on preferably solid protrusions of the channel base structure, are formed of finned wing material in a second additional structure, and each material protrusion forms a continuous transition substantially in the radial direction to the two side surfaces of the protrusion below it. Therefore, they constitute a fluid guiding structure that guides liquid fluid from the sides into the segments as is. The end surfaces of the protrusions arranged radially on the outer sides can extend over the entire width of the channel. At the locations of the material protrusions arranged on the protrusions, liquid fluid can also be exchanged between adjacent segments and can pass from one segment into an adjacent segment. The protrusions having the material protrusions placed thereon thus constitute a barrier to the passage of fluid.

[0017] In this case, the material protrusions in the axial direction may also have a smaller extent than the protrusions arranged below them. Due to the size, shape, and orientation of the material protrusions, the wetting behavior of the heat exchanger fluid is mainly due to the increased fluid flow. The profile of the material protrusions, which extend substantially in the axial and radial directions, can also be curved or irregular.

[0018] In this invention, by means of segmentation of this type of channel between two fins, the channel is interrupted for a period of time and again in the peripheral direction, thus at least reducing or completely preventing the migration of bubbles in the channel. The exchange of liquid and vapor along the channel is assisted to an increasingly smaller extent, or even not at all, by corresponding additional structures.

[0019] A particular advantage of this invention lies in the locally controlled exchange of liquid and vapor, with overflow of bubble nucleation sites occurring locally within the segments, and especially laterally due to material protrusions. In general, the targeted selection of channel segments allows for convenient optimization of the evaporator tube structure according to operating parameters, thus achieving increased heat transfer. Structural elements designed to enhance bubble formation in the grooved substrate are also particularly effective because the temperature at the fin bottom in the region of the grooved substrate is higher than that at the fin tips.

[0020] Furthermore, it is also advantageous to locally reduce the flow cross-sectional area in the channel between the two fins by at least 80% using additional structures. Overall, the evaporator tube structure can be further optimized to further increase heat transfer by increasing the separation of individual channel cross-sections in the channel segments, depending on the operating parameters.

[0021] In an advantageous embodiment of the invention, protrusions and material protrusions can locally reduce the flow cross-sectional area in the channel between the two fins by at least 30%. This locally and sufficiently defines the segment for fluid passage. Thus, the channel cross-section between the two segments is sufficiently separated, in terms of fluid, from the channel cross-section located adjacent to it.

[0022] Advantageously, protrusions and material protrusions can locally reduce the flow cross-sectional area in the channel between two fins by 40% to 70%. The channel cross-section located between the two segments forms a substantial barrier in terms of fluidity relative to the adjacent channel cross-section.

[0023] In a preferred embodiment of the invention, the channel can be radially closed outwards, in addition to a separate partial opening. Here, the fins can be substantially T-shaped or... The cross-section is shaped such that the channels between the fins are closed, except for pores that act as partial openings. Steam bubbles that appear during the evaporation process can escape through these openings. The fin tips can be deformed using methods that can be collected from existing technologies.

[0024] In this context, the fin tips can also be folded in the axial direction, or even formed to some extent in the direction toward the channel base. Therefore, the channel can also be gradually reduced in a desired amount from below and / or from the side and / or from above, from a combination of multiple complementary structural elements, or completely closed. The channel is always further divided into discrete segments between the fins.

[0025] By combining the segments according to the invention with channels that are closed except for pores or slits, a structure is obtained that exhibits very high liquid evaporation efficiency over a very wide range of operating conditions. In particular, the heat transfer coefficient of this structure achieves a consistently high level under conditions of varying heat flux density or driven temperature difference.

[0026] In an advantageous improvement of the invention, each segment may have at least one local opening. This minimum requirement also ensures that bubbles appearing in the channel segment during the evaporation process can escape to the outside. The size and shape of the local openings are designed such that even liquid media can pass through them and flow into the channel segment. Therefore, in order to maintain the evaporation process at the local openings, equal amounts of liquid and vapor must be conveyed through the openings in mutually opposite directions. Liquids that readily wet the tube material are typically used. Due to capillary effects, this type of liquid can permeate the channel through each opening in the outer tube surface, even against positive pressure.

[0027] Furthermore, the ratio of the number of local openings to the number of segments can be from 1:1 to 6:1. Preferably, the ratio can be from 1:1 to 3:1. The channels located between the fins are essentially closed by the material in the upper fin region, wherein cavities created in the channel segments connect to the surrounding space through openings. These openings can also be configured as pores, which can be formed of the same size or two or more size categories. Pores with two size categories may be particularly suitable when multiple local openings are formed in a ratio on the segments. For example, according to a regular repeating scheme, a large opening follows each small opening along the channel. This structure generates directional flow in the channel. Liquid is preferably drawn in through the small pores with the aid of capillary pressure and wets the channel walls, resulting in the formation of a thin film. Vapor accumulates in the center of the channel and escapes at the location with the lowest capillary pressure. Meanwhile, the large pores must be sized in such a way that vapor can escape quickly enough and the channel does not dry out in the process. The size and frequency of the vapor pores relative to the smaller liquid pores should be coordinated with each other.

[0028] In a preferred embodiment of the invention, the protrusion, taking the form of a first additional structure, can be formed at least from the material of the channel substrate between two integrally surrounding fins. In this way, an integrally bonded connection is maintained for good heat exchange from the tube wall to the corresponding structural element. Furthermore, the protrusion can also be additionally formed from the material of the fin sidewalls. The segmentation of the channel from the homogeneous material of the channel substrate is particularly advantageous for the evaporation process.

[0029] In a particularly preferred embodiment, the height of the protrusion of the first additional structural form can be between 0.15 mm and 1 mm. This dimensional design of the additional structure is particularly easy to coordinate with high-performance finned tubes, and is expressed by the fact that the structural dimensions of the external structure are preferably in the sub-millimeter to millimeter range.

[0030] In an advantageous manner, the protrusions can have an asymmetrical shape. The structural asymmetry here manifests in the cross-sectional plane perpendicular to the longitudinal tube axis. The asymmetrical shape can make an additional contribution to the evaporation process, especially if a relatively large surface area is formed. Asymmetry can be formed in the case of additional structures on the channel substrate and at the fin tips.

[0031] In a preferred embodiment of the invention, the protrusion may have a trapezoidal cross-section in a cross-sectional plane perpendicular to the longitudinal tube axis. The trapezoidal cross-section, combined with the integrally rolled finned tube structure, is a technically easily controlled structural element. Slight manufacturing asymmetries may occur in other parallel main sides of the trapezoid due to variations in the cross-section.

[0032] In an advantageous manner, opposing material protrusions can be formed at the location of the protrusion, in the direction of the longitudinal axis of the pipe. Thus, the protrusions and the opposing material protrusions together constitute a barrier for the passage of fluid. Attached Figure Description

[0033] The exemplary embodiments of the invention are explained in more detail with reference to the accompanying drawings, in which:

[0034] Figure 1 A partial view of the cross-section of a heat exchanger tube having segments subdivided by additional structures is schematically shown.

[0035] Figure 2 A perspective view schematically showing a portion of the external structure of a heat exchanger tube with folded fin tips.

[0036] Figure 3 A schematic view of the material protrusion at the location of the protrusion is shown in detail, and

[0037] Figure 4A detailed view schematically illustrates another embodiment of the material protrusion at the location of the protrusion, and,

[0038] Figure 5 The diagram schematically shows a perspective view of a portion of the external structure of a heat exchanger tube with opposing material protrusions at the protruding locations. Detailed Implementation

[0039] Figure 1 A partial cross-sectional view of a heat exchanger tube 1 according to the invention is schematically shown, having segments 8 subdivided by additional structures 7. The integrally rolled heat exchanger tube 1 has helically wrapped fins 2 on the outer side of the tube, with main grooves formed between the fins as channels 6. The fins 2 extend continuously without interruption along the helix on the outer side of the tube. The fin bottoms 3 protrude substantially radially from the tube wall 10. On the completed heat exchanger tube 1, the fin height H is measured from the lowest point of the channel base 61, from the fin bottoms 3 outside the fin sidewalls 4, to the fin tops 5 of the fully formed finned tube.

[0040] A heat exchanger tube 1 is proposed in which additional structures 7 in the form of radially outwardly pointing protrusions 71 are arranged in a region of a channel base 61, each protrusion being defined radially by an end surface 713 located between the channel base 61 and the fin tip 5. The protrusions 71 are referred to as first additional structures and are formed from the channel base 61 by the material of the tube wall 10. The protrusions 71 are arranged in the channel base 61 at preferably regular intervals and extend, at least partially or completely (not shown in the plan view), transverse to the course of the channel, from the fin bottom 3 of the fin 2 in the direction of the adjacent fin bottom above it. Radially outwardly pointing material protrusions 72 are arranged at the locations of the protrusions 71 in the form of second additional structures 7, the material protrusions being formed by the material of the fin sidewalls 4. Material protrusions 72 are each arranged radially between the end surface 713 and the fin tip 5, such that the material protrusions 72 are formed laterally on the fin sidewalls 4 via the channel base 61 of the channel 6, surrounding the radial extent of the protrusions 71. The material protrusions 72 extend further in the axial and radial directions than in the circumferential direction. In this way, the main groove of the channel 6 gradually tapers at regular intervals, at least partially. The resulting segments 8, together with the material protrusions 72, promote the formation of bubble nuclei, serving as a guiding structure for fluid flow in a specific manner. This at least reduces the direct exchange of liquid and vapor between individual segments 8.

[0041] In addition to the protrusions 71 formed on the channel base 61 with radially outwardly located material protrusions 72, the fin tips 5, which are the distal regions of the fins 2, are conveniently deformed in such a way that they partially close the channel 6 in the radial direction by axially folding the fin tips 51. The connection between the channel 6 and the environment is constructed in the form of pores 9, serving as partial openings to allow vapor bubbles to escape from the channel 6. The fin tips 5 are deformed by a rolling method, which can be adopted from the prior art. Thus, the main groove 6 forms an undercut groove. By combining the protrusions 71 with the material protrusions 72 in the form of additional structures 7, a segment 8 in the form of a hollow space is obtained, which is further distinguished by its very high liquid evaporation efficiency under a very wide range of operating conditions. The liquid evaporates within the segment 8 assisted by the material protrusions 72, serving as an additional fluid guiding structure. The generated vapor emerges from the channel 6 at the partial openings 9, through which the liquid fluid also flows. An easily wettable tube surface can also assist in the fluid inflow.

[0042] The solution according to the invention relates to a structured tube in which the heat transfer coefficient is increased on the outer side of the tube. To prevent the main portion of the heat flux resistance from shifting inward, the heat transfer coefficient can be further enhanced on the inner side through suitable internal structuring 11. The heat exchanger tube 1 for a tubular heat exchanger typically has at least one structured region and a smooth end member, and possibly a smooth intermediate member. The smooth end member and / or the intermediate member defines the structured region. To facilitate easy installation of the heat exchanger tube 1 in a tubular heat exchanger, the outer diameter of the structured region should not be greater than the outer diameter of the smooth end and the intermediate member.

[0043] Figure 2 A perspective view of a portion of the external structure of a heat exchanger tube 1 with folded fin tips 51 is schematically shown. For better illustration, only the structural elements of the external structure most important for understanding are shown. In addition to a protrusion 71 formed at the channel base 61, which has radially outwardly positioned material protrusions 72, the fin tips 5 are further deformed into the distal region of the fins 2 in such a way that they partially close the channel 6 radially through the axially folded fin tips 51. The connection between the channel 6 and the surrounding environment is constructed in the form of a partial opening 9 for vapor bubbles to escape from the channel 6 and for liquid fluid to flow into the channel 6. In this way, the main groove 6 further constitutes an undercut groove. The axially folded fin tips 51 are formed by the fins 2 and thus extend axially over the channel 6. Through the additional structure 7, the flow cross-sectional area in the channel 6 between the two fins 2 is particularly effectively and locally reduced, thereby restricting fluid flow in the channel 6 during operation.

[0044] Figure 3A detailed view of the material protrusion 72 at the location of the protrusion 71 is schematically shown. Material protrusion 72, radially positioned onto the preferably solid protrusion 71, is produced from the material of the fin sidewall 4 by a toothed roller, forming both the wall material on the channel base 61 and the material on the fin sidewall 4. Although the protrusion 71 and the material protrusion 72 are thus formed by different regions of the tube wall, the material protrusion 72 can substantially form a transition that continues radially to the two side surfaces 711 of the protrusion 71 located below them. In this case, the protrusion 71 travels only on a portion of the channel base 61 and terminates at the front surface 712 in the axial tube direction. The material protrusion 72 is formed as a diaphragm and extends generally radially and in the direction of the tube's longitudinal axis A, and, for example, in the axial direction, extends approximately as far as the channel center. In this respect, the end surface 713 of the protrusion 71 can also extend further in the direction of the tube's longitudinal axis A, or even across the entire channel width between the opposing fins. Starting in this region, the fluid flow can be controlled more precisely, and it can help form bubbles in two adjacent segments 8 in the circumferential direction. Therefore, the protrusion 71 with the material protrusion 72 placed thereon also constitutes a barrier for the passage of fluid.

[0045] Similarly, as from Figure 3 It is evident that the axial extent of the material protrusion 72 is slightly shorter than that of the protrusion 71 located below it. In this way, an opening is created relative to the longitudinal axis A of the tube for the liquid heat exchanger fluid, which is more easily guided from the side into the adjacent segment 8 to aid in bubble formation.

[0046] Figure 4 A detailed view of another embodiment of the material protrusion 72 at the location of protrusion 71 is schematically shown. The material protrusion 72, radially positioned onto the protrusion 71 of the channel substrate, is made of the material of the fin sidewall 4 via a toothed roller, forming both the wall material on the channel substrate 61 and the material on the fin sidewall 4. The profile of the material protrusion, extending substantially in both the axial and radial directions, is also curved or irregular. In this embodiment, the material protrusion 72 has a range of variation in the axial direction. In other words, a continuous transition into the fin sidewall 4 is achieved, as seen outwardly in the radial direction. Overall, the surface of the material protrusion 72 is also slightly inherently curved. These shapes are variations of the otherwise flat surface, which are particularly advantageous in terms of the surface properties and wetting behavior of the liquid heat exchanger fluid. This structure guides the liquid heat exchanger fluid laterally into adjacent sections 8 in a particularly preferred manner to aid in bubble formation.

[0047] Figure 5A schematic perspective view of a portion of the external structure of a heat exchanger tube 1 is shown, which has two opposing material protrusions 72 at the location of protrusion 71. For better illustration, only the structural elements of the external structure most important for understanding are shown. In addition to the protrusion 71 formed on the channel base 61, which has material protrusions 72 radially located on the outer side, the fin tips 5, which in turn serve as the distal regions of the fins 2, are deformed in such a way that they partially close the channel 6 in the radial direction by means of the axially folded fin tips 51. The connection between the channel 6 and the surrounding environment is configured as a local opening 9 for the escape of vapor bubbles from the channel 6 and for the inflow of liquid fluid into the channel 6. With the protrusions 71 and material protrusions 72 in the form of an additional structure 7, the flow cross-sectional area in the channel 6 between the two fins 2 is particularly effectively and locally reduced, thereby restricting the fluid flow in the channel 6 during operation.

[0048] In this configuration, the protrusion 71 extends along the longitudinal axis A of the tube over the entire width of the channel between adjacent fins 2. Opposite material protrusions 72 are formed radially outward at the location of the protrusion 71. The protrusion 71, with the material protrusions 72 placed thereon, thus constitutes a barrier for fluid passage.

[0049] List of reference numerals

[0050] 1. Heat exchanger tube;

[0051] 2. Fins;

[0052] 3. The bottom of the fin;

[0053] 4. Fin side wings;

[0054] 5. Fin tip, distal region of the fin;

[0055] 51. Axially folded fin tips;

[0056] 6 channels, main groove;

[0057] 61-channel substrate;

[0058] 7. Additional structures;

[0059] 71. A protrusion of the first additional structural form on the channel substrate;

[0060] 711 Protruding lateral surface;

[0061] 712 The protruding front surface;

[0062] 713 Protruding end surface;

[0063] 72. Material protrusion;

[0064] 8 segments;

[0065] 9. Local openings, pores;

[0066] 10. Pipe wall;

[0067] 11. Internal structure;

[0068] Longitudinal axis of tube A;

[0069] H is the fin height.

Claims

1. A metal heat exchanger tube (1) for evaporating a liquid fluid on the outer surface of a tube, the heat exchanger tube comprising integral fins (2) formed on the outer side of the tube and having a fin bottom (3), fin side wings (4) and a fin top (5), wherein, The bottom of the fin (3) protrudes radially from the tube wall (10) and forms a channel (6) with a channel base (61) between the fins (2), wherein additional structures (7) spaced apart by the channel are arranged in the channel. - The additional structure divides the channel (6) between the fins (2) into segments (8), and - The additional structure locally reduces the flow cross-sectional area in the channel (6) between the two fins (2), thus restricting fluid flow in the channel (6) at least during operation, and - The first additional structure is a radially outwardly pointing protrusion (71) that emerges from the channel base (61) and is defined in the radial direction by an end surface (713) located between the channel base (61) and the fin tip (5), thereby defining the radial extent of the protrusion (71). - Material protrusions (72) in the form of a second additional structure are arranged radially outward at the location of protrusions (71), and the material protrusions are formed by the material of the fin side wings (4). - Material protrusions (72) are each arranged radially between the end surface (713) and the tip of the fin (5) and in contact with the end surface (713) of the protrusion (71), such that the material protrusions (72) are formed laterally on the fin sidewalls (4) around the radial extent of the protrusions (71) via the channel base (61) of the channel (6), and - Wherein, the material protrusion (72) extends further in the axial and radial directions than in the circumferential direction. - Wherein, the protrusions (71) and material protrusions (72) locally reduce the flow cross-sectional area in the channel (6) between the two fins (2) by at least 30%, thereby controlling the exchange of fluid between adjacent segments (8).

2. The heat exchanger tube (1) according to claim 1, characterized in that, The protrusions (71) and material protrusions (72) locally reduce the flow cross-sectional area in the channel (6) between the two fins (2) by 40% to 70%.

3. The heat exchanger tube (1) according to claim 1 or 2, characterized in that, In addition to a separate local opening (9), the channel is radially closed outward (6).

4. The heat exchanger tube (1) according to claim 1, characterized in that, Each segment (8) has at least one local opening (9).

5. The heat exchanger tube (1) according to claim 1, characterized in that, The protrusion (71) is formed of at least the material of the channel base (61) between the two integrally circumferential fins (2).

6. The heat exchanger tube (1) according to claim 5, characterized in that, The protrusion (71) has a height between 0.15 mm and 1 mm.

7. The heat exchanger tube (1) according to claim 1, characterized in that, The protrusion (71) has an asymmetrical shape.

8. The heat exchanger tube (1) according to claim 1, characterized in that, The protrusion (71) has a trapezoidal cross section in a cross-sectional plane extending perpendicular to the longitudinal axis (A) of the tube.

9. The heat exchanger tube (1) according to claim 1, characterized in that, In the direction of the longitudinal axis (A) of the tube, opposite material protrusions (72) are formed at the position of the protrusion (71).

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