Metal heat exchanger tube

Abstract

The present invention relates to a metal heat exchanger tube (1) comprising integral fins (2) formed on the outer side of the tube, the fins having a fin bottom (3), fin side wings (4) and a fin top (5), the fin bottom (3) projecting radially from the tube wall (10) and forming 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 additional structures (7, 71, 72) locally reduce the cross-sectional area through which fluid can flow between the two fins (2) in the channel (6), and thus at least define the fluid flow in the channel (6) during operation. The first additional structures (7, 71) are defined by radially outwardly pointing protrusions (71) that begin from the channel base (61) and are each defined in the radial direction by a terminating surface (713) located between the channel base (61) and the fin bottom (5), thereby defining a radial extension of the protrusion (71). Radially outwardly positioned cavities (72) are arranged at the location of the protrusions (71) as second additional structures (7, 72) and are formed of the material of the fin sidewalls (4) and the radially outwardly positioned terminating surfaces (713) of the protrusions (71). Each cavity is arranged in the radial direction between the terminating surface (713) and the fin tip (5), such that cavities (72) of a radial extent surrounding the protrusions (71) are formed above the channel base (61) of the channel (6) and laterally abut against the fin sidewalls (4). The cavities (72) are open in the axial direction.

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] Furthermore, DE 10 2008 013 929 B3 discloses a structure designed as a local cavity at the bottom of the groove, which, as a result, enhances the nucleation boiling process to increase heat transfer during evaporation. The cavity location near the bottom of the main groove is advantageous for the evaporation process because the excess temperature is greatest at the bottom of the groove, thus providing the highest driving temperature difference for bubble formation.

[0008] 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.

[0009] 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

[0010] The purpose of this invention is to develop a heat exchanger tube with improved performance for evaporating liquid on the outside of the tube.

[0011] This 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 tips, wherein the fin base projects substantially 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 cavity in the form of a second additional structure is arranged radially outward at the location of the protrusion, the cavity being formed by the end surface radially arranged on the outer side of the protrusion and the material of the fin sidewalls. Each cavity is arranged radially between the end surface and the fin tip, such that the cavity is formed laterally on the fin sidewalls via the channel base of the channel, around the protruding radial extent. The cavity is open in the axial direction.

[0012] These metal heat exchanger tubes are specifically designed for evaporating liquids from pure substances or mixtures on the outside of the tubes.

[0013] This type of high-efficiency tube can be manufactured based on integrally rolled finned tubes using rolling discs. Integrally rolled finned tubes are understood to refer to finned tubes in which fins have already 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 is manufactured using a sharp-edged rolling disc and a toothed rolling disc, the sharp-edged rolling disc pre-forming the material from the protruding fin sidewalls, the toothed rolling disc being connected to the sharp-edged rolling disc by a process technique, and both forming the wall material at the channel base and forming the pre-formed material for forming cavities on the fin sidewalls. The structure according to the invention can also be manufactured, as is, solely using a toothed rolling disc, which forms both the wall material at the channel base and the material for forming cavities from the fin sidewalls.

[0014] 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.

[0015] 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.

[0016] In addition to forming bubbles within the segments, according to the solution of the invention, additional bubble nucleation sites are located in the region of the first additional structure in the form of radially outward-pointing protrusions. The bubble nucleation sites exist in the form of cavities radially outward-pointing on the protrusions. Bubble nuclei that facilitate bubble formation within the segments are preferably formed in the hollow spaces created by the cavities. The protrusions may extend axially between the corresponding fin bases 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. The protrusions spaced apart from and following each other within the channel, as well as the cavities in the form of radially outward-pointing additional structures, can each vary in height and shape.

[0017] In other words, the cavities placed on the preferably solid protrusions of the channel base structure are formed of the material of the fin sidewalls, and each cavity forms a continuous transition in the radial direction to the two side surfaces of the protrusion below it. The cavities are formed in a hollow manner, consisting of lateral surfaces and a covering surface, end surfaces arranged radially on the outer sides of the protrusions, and fin sidewall surfaces defining them on the rear side, the covering surface forming the end in the direction of the fin tip. In the cavities, the lateral surfaces and the covering surface form a boundary surface that extends generally in the direction of the longitudinal axis of the tube, and for example, extends approximately as far as the center of the channel in this axial direction. The end surfaces of the protrusions arranged radially on the outer sides can extend over the entire width of the channel. The cavities have openings to discharge bubble nuclei in the axial direction. Thus, bubble nuclei can contribute to the formation of bubbles in two adjacent segments in the peripheral direction. At the location of the bubble nucleus outlet points arranged on the protrusions, liquid fluid can also be exchanged between adjacent segments, and passage is prevented as is, provided that no bubble nucleus formed by gaseous fluid dominates there. In other words, as long as no bubble nucleus fills the connection point between adjacent segments, liquid fluid can pass from one segment into an adjacent segment. The protrusions with cavities placed on them thus form a barrier to the passage of fluid.

[0018] In this configuration, the lateral surface of the cavity may also be longer than the cover surface in the axial direction toward the adjacent fins. This results in an opening in the cavity that is positioned obliquely relative to the longitudinal axis of the tube, and facilitates the release of bubble nuclei into adjacent segments for bubble growth. The end profiles of the openings forming the cavity on both the lateral and cover surfaces may also be curved or irregular. Similarly, in these preferred embodiments, the cavity remains substantially open in the axial direction even in an oblique position.

[0019] 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.

[0020] A particular advantage of this invention lies in the locally controlled exchange of liquid and vapor, with overflow at bubble nucleation sites occurring locally within the segments. In general, the evaporator tube structure can be conveniently optimized according to operating parameters through targeted selection of channel segments, 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 grooved substrate region is higher than that at the fin tips.

[0021] Furthermore, it is also advantageous to locally reduce the flow cross-sectional area in the channel between the two fins using additional structures. Overall, the evaporator tube structure can be further optimized to further increase heat transfer by adding separation of individual channel cross-sections in the channel segments, depending on the operating parameters.

[0022] In an advantageous embodiment of the invention, the protrusions and cavities 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.

[0023] Advantageously, the protrusions and cavities can locally reduce the flow cross-sectional area in the channel between the 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] In an advantageous manner, two opposing cavities can be formed at the location of the protrusion, along the longitudinal axis of the tube. Therefore, in the case of two cavities, the openings for discharging the bubble nuclei are directly opposite each other in the axial direction. Consequently, in the circumferential direction, bubble nuclei in adjacent segments can contribute to bubble formation. The protrusion with the two cavities placed thereon thus constitutes a barrier for fluid passage. At this point, it can be demonstrated that the openings in these cavities, which are positioned obliquely relative to the longitudinal axis of the tube, are particularly advantageous and facilitate the release of bubble nuclei into adjacent segments for bubble growth. Attached Figure Description

[0034] The exemplary embodiments of the invention are explained in more detail with reference to the accompanying drawings, in which:

[0035] Figure 1 schematically shows a partial view of the cross-section of a heat exchanger tube with segments subdivided by additional structures.

[0036] Figure 2 schematically shows a perspective view of a portion of the external structure of a heat exchanger tube with folded fin tips.

[0037] Figure 3 schematically shows a detailed view of the cavity at the location of the protrusion, and

[0038] Figure 4 schematically shows a partial oblique view of the external structure of a heat exchanger tube with two opposing cavities at the protruding location.

[0039] In all the accompanying drawings, corresponding parts are given the same reference numerals. Detailed Implementation

[0040] Figure 1 schematically shows a partial cross-sectional view of a heat exchanger tube 1 according to the invention, which has 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 to the fin tip 5 of the fully formed finned tube.

[0041] 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 transversely to the course of the channel, at least partially or completely (not shown in the plan view) from the fin bottom 3 of the fin 2 in the direction of the adjacent fin bottom above it. A radially outwardly pointing cavity 72 is arranged at the location of the protrusions 71 in the form of a second additional structure 7, the cavity being formed by the material of the end surface 713 radially arranged on the outer side of the protrusions 71 and the fin sidewalls 4. Each cavity is arranged radially between the end surface 713 and the fin tip 5. Thus, the cavity 72 is formed laterally on the fin sidewall 4 via the channel base 61 of the channel 6 surrounding the radial extent of the protrusion 71. The cavity 72 is open in the axial direction. In this way, the main groove of the channel 6 gradually tapers at regular intervals, at least partially. The resulting segments 8 are specifically engaged with the cavity 72 to promote bubble nucleation. This at least reduces the exchange of liquid and vapor between individual segments 8.

[0042] In addition to forming protrusions 71 on the channel base 61 having radially external cavities 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 local openings that 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 cavity 72 in the form of an additional structure 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 supported by the cavity 72, serving as additional nucleation sites. The generated vapor emerges from the channel 6 at the local opening 9, through which the liquid fluid also flows. An easily wettable tube surface can also be an aid to fluid inflow.

[0043] 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.

[0044] Figure 2 schematically shows a partial oblique view of the external structure of a heat exchanger tube 1 with folded fin tips 51. 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 a cavity 72 radially located on the outer side, 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 along the channel 6. The transition region from the fin sidewalls 4 to the folded fin tips 51 can be seen in the figure through a small platform-like structure along the fin extent. By means of the additional structure 7, the cross-sectional area of ​​the flow passage in the channel 6 between the two fins 2 is reduced locally in a particularly effective manner, thereby restricting the fluid flow in the channel 6 during operation.

[0045] Figure 3 schematically shows a detailed view of the cavity 72 at the location of the protrusion 71. The cavity 72 is radially positioned onto the preferably solid protrusion 71 by means of a toothed roller, which forms both the wall material on the channel base 61 and the material on the fin sidewall 4. Although the protrusion 71 and the cavity 72 are thus formed by different regions of the tube wall, the cavity 72 can essentially form a transition that continues radially to the two side surfaces 711 of the protrusion 71 located below it. 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 cavity 72 is formed in a hollow manner, consisting of a lateral surface 721 and a covering surface 722, an end surface 713 arranged radially on the outer side of the protrusion 71, and a portion of the fin sidewall surface that defines it on the rear side (hidden by the lateral surface 721 in Figure 3). Lateral surfaces 721, covering surfaces 722, and end surfaces 713 of protrusions 71 are the boundary surfaces of cavity 72, extending generally in the direction of the longitudinal axis A of the tube and forming, for example, approximately as far as the center of the channel in the axial direction. In this respect, end surfaces 713 of protrusions 71 may extend further in the direction of the longitudinal axis A of the tube, or even extend over the entire channel width between the opposing fins. Cavity 72 has openings 723 to discharge bubble nuclei substantially in the axial direction of the tube. Thus, bubble nuclei in two adjacent segments 8 in the circumferential direction can contribute to bubble formation. Therefore, protrusions 71 having cavities 72 thereon constitute a barrier for fluid passage.

[0046] As is also evident from Figure 3, the lateral surface 721 of the cavity 72 is longer than the covering surface 722 in the axial direction toward the adjacent fins. In this way, an opening 723 is created in the cavity 72, which is positioned obliquely relative to the longitudinal axis A of the tube, and it is easier to release bubble nuclei into the adjacent segments 8 for bubble growth. However, when the opening 723 is positioned slightly obliquely, the cavity 72 is thus also substantially open in the axial direction A.

[0047] Figure 4 schematically shows a perspective view of a portion of the external structure of a heat exchanger tube 1, which has two opposing cavities 72 at the location of the protrusion 71 and folded fin tips 51. 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 cavities 72 radially located on the outer side, the fin tips 5, 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 using the axially folded fin tips 51. The connection between the channel 6 and the surrounding environment is configured as a partial 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 protrusion 71 and cavities 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 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 channel width between adjacent fins 2. Two opposing cavities 72 are formed radially outward at the locations of the protrusions 71. Therefore, in the case of two cavities 72, the openings for discharging bubble nuclei are directly opposite each other in the axial direction A. Consequently, bubble nuclei in two adjacent segments in the circumferential direction can contribute to bubble formation. The protrusion 71 with the two cavities 72 placed thereon thus constitutes a barrier for fluid passage. In this configuration, the openings in the cavities 72, which are also positioned slightly inclined relative to the longitudinal axis A of the tube, prove particularly advantageous and facilitate the release of bubble nuclei into adjacent segments for bubble growth.

[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. Cavity in the second additional structural form;

[0064] 721 Lateral surface of the cavity;

[0065] The covering surface of the 722 cavity;

[0066] 723 Openings in a cavity;

[0067] 8 segments;

[0068] 9. Local openings, pores;

[0069] 10. Pipe wall;

[0070] 11. Internal structure;

[0071] Longitudinal axis of pipe A;

[0072] H is the fin height.

Claims

1. A metal heat exchanger tube (1) comprising integral fins formed on the outer side of the tube and having a fin bottom (3), fin side wings (4), and 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 each protrusion 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). Its features are, - In this configuration, a cavity (72) in the form of a second additional structure is arranged radially outward at the location of the protrusion (71), and the cavity is formed by the material of the fin sidewalls (4) and the end surface (713) radially arranged on the outer side of the protrusion (71). - Wherein, each cavity is arranged radially between the end surface (713) and the fin tip (5), such that the cavity (72) is formed laterally on the fin sidewall (4) around the radial extent of the protrusion (71) via the channel base (61) of the channel (6), and - Wherein, the cavity (72) is open in the axial direction.

2. The heat exchanger tube (1) according to claim 1, characterized in that, The protrusion (71) and cavity (72) locally reduce the flow cross-sectional area in the channel (6) between the two fins (2) by at least 30%.

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

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

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

6. 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).

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

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

9. 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.

10. The heat exchanger tube (1) according to claim 1, characterized in that, In the direction of the longitudinal axis (A) of the tube, two opposing cavities (72) are formed at the position of the protrusion (71).

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