EP1793190B1 - Heat exchanger fin, production method therefore and heat exchanger - Google Patents

Description

The invention relates to a heat transfer fin, which is arranged between tubes in which a medium flows, which is in heat exchange with another medium flowing through the heat transfer rib,
wherein the heat transfer rib can be produced from a thin sheet metal strip, from the plane of which exposed cuts are arranged which have leading and trailing edges which are deformed, in particular tapered. Further, the invention relates to a method of manufacturing heat transfer fins and a heat exchanger containing heat transfer fins thus produced. It is a well-known fact that inventors get ideas for inventive activities from nature, which they try to transfer to technical solutions. This also applies to fluidic or thermodynamic processes in particular - only the typical flow profile of the dolphins is mentioned.

Out WO 2004 / 065879A1 For example, there is known a generally advanced heat transfer fin having the leading features. There, in a heat transfer rib which is flowed through, for example, by cooling air, it has been proposed to deform the leading edges of the cuts lying in the direction of the incoming air, and also to thin the trailing edges of the cuts there, in order to achieve more favorable conditions. As is known, such heat transfer ribs are made of extremely thin metal sheets, of the order of 0.070 mm, so that the mentioned further dilution of the leading edges could theoretically be a viable option, but could in practice give a difficult implementation. In any case, the practical implementation was not shown in the mentioned document. It is possible that significantly thicker metal sheets are used there.

Much thicker metal sheets are also in the publication DE - OS - 2 123 722 used, namely those which are about 0.3 mm thick. There, it has been proposed to bead over exposed wings from the rib plane.

The inventors have set themselves the task of proposing a heat transfer fin improved in terms of heat exchange efficiency, a method for producing such fins and an improved heat exchanger containing such fins.

This object is achieved with respect to the heat transfer rib according to the invention with the features of claim 1.

Thereafter, the cuts between the leading edges and the trailing edges have a thickening that is thicker than the sheet metal strip from which the heat transfer rib is made. The leading edges are the forward edges in the flow direction of the medium flowing through the ribs, while the trailing edges are the edges further downstream in the flow direction. Each cut has a leading edge and a trailing edge. The edges are in tape thinning lines.

For example, when one of skill in the art speaks of reshaping the "cuts," he usually means the web-like strip that exists between each of two cuts.

In contrast to the described prior art, the inventors of the present proposal have consistently gone to the end of the process of transferring aerodynamic profiles from nature to technology. This approach does not see the applicant as an obvious measure, because it is in the sections of the heat transfer ribs almost miniaturized structure, where the problem is inter alia in the implementation or in the tool technology and cost-effective mass production of large numbers. The proposal has also contributed to the solution of the above-mentioned problem.

The inventors have found that even with such relatively small flow bodies as in the cuts, a heat transfer performance promoting flow can be created. The flow path of the near-wall flow was extended by the provision of a dilution also at the trailing edges. The separation of the flow from the wall was thereby suppressed. The turbulence of the medium, for example, the cooling air, after the flow through the heat exchanger rib was also suppressed, whereby the pressure loss in the cooling air has developed very moderately.

According to one aspect, it is provided that the heat transfer rib is wave-shaped, having wave crests and wave troughs which are connected by wave flanks, wherein the cuts are located in the wave flanks. These are so-called corrugated ribs.

However, according to another aspect, it is also advantageous if the heat transfer rib is approximately flat and has openings through which the tubes can be inserted. These are so-called flat ribs.

According to a further development aspect, it has been provided that the sections in cross section have a dolphin shape or a tuna shape or a penguin shape or a drop shape.

It has been found in CFD analyzes that in one embodiment, compared with the prior art, there is an approximately 3% increase in the heat transfer coefficient at about 10% lower pressure drop. Other embodiments have different values.

With regard to the band thinning lines, it is further provided that the leading and trailing edges of the cuts, prior to their removal from the plane of the sheet metal strip, are located approximately on ribbon thinning lines running parallel in the longitudinal direction of the strip. The tape thinning lines run through without interruptions in the tape longitudinal direction, so that they - in the case of corrugated fins - are also present in the troughs and wave crests. This measure provides appropriate turbulence in the inner vicinity of the wave crests and

Troughs, where otherwise often a harmful, d. H. results in a heat exchange performance reducing flow bypass. In the outer area of the wave crests and wave troughs, the corrugated fins are usually soldered to the pipes. In any case, the fine "corrugation" that is present there is not detrimental to the connection, for example the solder joint.

The cuts are arranged in sets of cuts, wherein inter-cuts of the cuts between the sets of cuts in the transverse direction of the band can be provided.

The sets of cuts can be subdivided into groups of cuts by means of parallel webs.

It is further intended that parallel to the tape longitudinal direction running

Connecting strips are provided which result from the distances between the arranged in the tape longitudinal direction cuts, or represent the interruptions of the mentioned sections.

For corrugated heat transfer fins (corrugated fins), it has been provided that the connection strips run within the corrugation flanks.

Alternatively, it was provided that the connecting strips are arranged in the wave crests or troughs.

• a) das Blechband wird in Längsrichtung des Bandes in parallel verlaufenden Linien verdünnt,
• a1) wodurch in Abständen angeordnete, und parallel in der erwähnten Längsrichtung verlaufende Bandverdünnungslinien ausgebildet werden;
• b) in den Bandverdünnungslinien werden intermittierende, das heißt, Unterbrechungen aufweisende Trennschnitte ausgeführt;
• b1) um mittels der Unterbrechungen quer zur Bandlängsrichtung laufende Verbindungsstreifen auszubilden;
• c) zwischen dem Beginn und dem Ende der Trennschnitte werden Umformungen ausgeführt, um die herausgestellten Schnitte zu bilden.
  Die Herausbildung der durchgehenden Bandverdünnungslinien gemäß den Schritten
• a) und a1) wird gegenwärtig für besonders bedeutsam angesehen.
  Bei wellenförmigen Wärmeübertragungsrippen (Wellrippen) ist weiterhin vorgesehen, dass im Anschluss an die erwähnten Schritte
• d) eine Bandwellung quer zur Längsrichtung des Bandes vorgenommen wird,
• d1) wobei entweder die Wellenberge bzw. Wellentäler jeweils im Bereich zwischen Anfang und Ende der Unterbrechungen bzw. in den Verbindungsstreifen zu liegen kommen.
• d2) oder wobei die Bandwellung so vorgenommen wird, dass die Unterbrechungen bzw. die Verbindungsstreifen jeweils im Bereich der Schnitte verlaufen.

Diese Schritte können mittels gezackter Walzen ausgeführt werden, was an sich bekannt ist.
Nach einem weiterbildenden Verfahrenanspruch wurde vorgesehen, dass die Wellenberge und die Wellentäler etwa halbrund ausgebildet werden.The method for producing heat transfer ribs which has sections exposed from the plane and is produced from a sheet metal strip which runs through profiled roller sets or embossing tools is characterized according to the invention by the following steps:

• a) the sheet metal strip is thinned in the longitudinal direction of the strip in parallel lines,
• a1) whereby belt thinning lines spaced and parallel to said longitudinal direction are formed;
• b) in the band thinning lines, intermittent, that is, interruption, cuts are made;
• b1) to form by means of the interruptions transversely to the tape longitudinal direction running connection strip;
• c) transformations are performed between the beginning and the end of the cuts to form the exposed cuts.
  The formation of the continuous band thinning lines according to the steps
• a) and a1) are currently considered to be particularly significant.
  In wavy heat transfer ribs (corrugated fins) is further provided that following the mentioned steps
• d) a tape corrugation is made transverse to the longitudinal direction of the tape,
• d1) whereby either the wave crests or wave troughs each come to lie in the region between the beginning and the end of the interruptions or in the connecting strip.
• d2) or wherein the tape corrugation is made so that the interruptions or the connecting strips each extend in the region of the cuts.

These steps can be carried out by means of serrated rollers, which is known per se.
According to a further development method claim was made that the wave crests and the troughs are formed approximately semicircular.

According to an alternative method claim, it was provided that the wave crests and the wave troughs are formed flat, wherein the wave flanks are bent at about 90 ° from the wave troughs or crests and extend approximately parallel to each other.

A further development provides that step a) includes the formation of longitudinally continuous belt thinning lines.

The steps b) and c) can be carried out successively or simultaneously. In the simultaneous execution, the sections lying between two cuts are twisted simultaneously with their introduction in their longitudinal direction, whereby the exposed cuts arise.
According to another aspect of the manufacturing method, the roller sets or the embossing tools may be heated to assist the remodeling processes.
The heat exchanger according to the invention is characterized in that it has the heat transfer ribs produced according to the invention. It may be wavy or flat, that is, about flat heat transfer ribs.

• Die Fig. 1 zeigt einen Ausschnitt aus einer Wärmeübertragungsrippe, die als Wellrippe ausgebildet ist.
• Die Fig. 2 zeigt ein beispielhaftes Profil eines Schnittes der Wärmeübertragungsrippe.
• Die Fig. 3 zeigt das Profil eines Schnittes aus dem Stand der Technik.
• Die Fig. 4 und 5 zeigen unterschiedliche Gestaltungen der Schnittausführungen.
• Die Fig. 6, 7 und 8 zeigen schematisch das Herstellungsverfahren der Wärmeübertragungsrippe.
• Die Fig. 9 zeigt andere Querschnittsformen für Schnitte und dazugehörige CFD-Resultate.
• Die Fig. 10 zeigt ein anderes Ausführungsbeispiel am Beispiel einer Wellrippe.
• Die Fig. 11 zeigt einen Ausschnitt beispielsweise aus der Fig. 10.
• Die Fig. 12 zeigt einen Teil eines Wärmetauschers aus einem weiteren Ausführungsbeispiel.

The invention will be described below in embodiments with reference to the accompanying drawings. The following description contains other features and advantages that may later prove to be significant.

• The Fig. 1 shows a section of a heat transfer rib, which is designed as a corrugated fin.
• The Fig. 2 shows an exemplary profile of a section of the heat transfer fin.
• The Fig. 3 shows the profile of a section from the prior art.
• The Fig. 4 and 5 show different designs of sectional designs.
• The FIGS. 6, 7 and 8 show schematically the manufacturing process of the heat transfer rib.
• The Fig. 9 shows other cross-sectional shapes for cuts and associated CFD results.
• The Fig. 10 shows another embodiment of the example of a corrugated fin.
• The Fig. 11 shows a section, for example, from the Fig. 10 ,
• The Fig. 12 shows a part of a heat exchanger of a further embodiment.

The heat transfer fins 1 are made of a metallic sheet metal strip 3 , for example, aluminum strip material is a preferred choice. The thickness of the sheet metal strip is in the range of 0.050 mm. The manufacturing process can be carried out by means of stamping tools, which are clamped in a forming machine, which works in the long-stroke, or by means of forming rollers. The production by means clamped in presses stamping tools was not shown in the figures. In the Fig. 6 Rolls 30 were used, with one upper roll and one lower roll forming a set of rolls. Only a single roller set 30 has been outlined, although several sets of rollers 30 join together. This roll set 30 or these roller sets 30 produce first on the surface of the strip 3 and parallel spaced ununterbroche in the strip longitudinal direction, that is continuous tape dilutions, referred to as a band thinning lines. 8 The distance of adjacent tape thinning lines 8 is in the range of 1.0 mm or less. The band thinning lines 8 profiled or corrugate the surface of the sheet metal strip 3 at the top and - in the illustrated embodiment - also on the bottom. The upper picture in the Fig. 6 shows the output sheet-metal strip 3 and arranged underneath figure shows the formed strip thinning lines 8. In the already curled, not shown in detail the preparation of the heat transfer fins 1 by means of operating in continuous metal forming (pressing) the sheet metal band 3 is intermittently fed, or drawn, wherein at each press a Piece of Bandverdünnungslinien 8 is pronounced, to which seamlessly at the next stroke another piece Bandverdünnungslinien 8 connects, etc. To form the Bandverdünnungslinien 8 can also Fig. 7 be used, which shows a principal and significantly enlarged section of the rollers 30 and the embossing and cutting tools. Subsequent to steps a) and a1) just described, step b) is undertaken, namely the introduction of the separating cuts, from which later the cuts 12 result. For this purpose, the lowest representation in the Fig. 6 referenced as well as on the Fig. 8 , In all band thinning lines 8 are not by means of one or more shown subsequent roller sets 30 or tool sets cut sections introduced. The separation cuts have all the same length, and they are in the strip transverse direction, exactly like the band thinning lines 8, spaced apart, since the cuts are arranged to lie in the band thinning lines. 8 Sets of separating cuts are introduced, which are interrupted in the strip longitudinal direction by connecting strips 9 extending in the transverse direction of the strip. In the lowest version of the Fig. 6 the reference number 9 can be found. In the embodiment shown there, the connecting strips 9 in a corrugated rib represent the wave crests 5 and the wave troughs 4 , between which the corrugation flanks 11 are arranged, in which the cuts 12 extend in turn. To the corrugated fins is still to say that only such corrugated fins have been shown, the flat wave crests 4 and troughs 5 have. (Flat Top Fin) The length of the cuts 12 should extend as far as possible directly to the wave crests 4 or wave troughs 5 , ie preferably over the entire height H of the corrugated fins. Other corrugated fins with approximately semicircular wave crests 4 and troughs 5 are also very well known to the skilled person, and they have therefore not been shown here. Preferred corrugated heights H can be in the range of 5, 0 - 12, 0 mm. The wavelengths - half of the wavelengths are referred to by the person skilled in the art as wave splitting - are likewise adjustable in a wide range, depending on the application in individual cases. Further, it has been thought to form the course of the waves with a certain inclination, so that the horizontally flowing example, cooling air undergoes a deflection downwards or upwards, depending on whether the shaft inclination points upwards or downwards.
In contrast to the above shows the Fig. 10 That the connecting strip 9 may be located in a finished corrugated fin formed in the wave flanks. 11 In this case, the connecting strips 9 pass transversely through the cuts 12 or through the wave flanks 11 . In such cases narrower connecting strip 9 may be provided, which take up as little space in the area of the cuts 12th The Indian Fig. 10 drawn line is intended to indicate a connecting strip 9. Such strips 9 are also located in all behind arranged wave flanks 11. They are not visible in this illustration. The sets of separating cuts thus also pass through the wave crests 4 and the wave troughs 5 in this case.

As the Fig. 8 shows further, at the same time, ie simultaneously with the introduction of the cuts, by means of a set of rollers 30 or a set of tools, the forming of the cuts done, ie it is made what is referred to here as cuts 12 . The cross section of each section 12 between the tapered front edge 12.1 and the tapered trailing edge 12.2 receives a thickening 10. The thickening 10 is dimensionally quite well above the thickness of the metal strip 3. This can be particularly clear from the Fig. 11 taken where a greatly enlarged representation of the cross sections of three adjacent sections 12 but also, in comparison, the thickness of the sheet metal strip 3 can be seen. (See, for example, the Fig. 2 or 9 ) From the mentioned Fig. 11 is another possibility recognizable, namely the leading edge of the rib 1 in addition to dilute.
It is also possible to initially introduce only the separating cuts and in a subsequent tool set - ie not simultaneously - to make the deformation of the cuts to form the cuts 12 .
The Fig. 4 shows a single set 120 of sections 12 exposed out of the plane E of the sheet metal strip Fig. 5 shows that it is possible to divide a set 120 of cuts 12 by means of a web 15 into, for example, two groups 100 of cuts 12 . The webs 15 improve the stability of the corrugated ribs or their corrugated flanks 11. As can be seen, the cuts 12 in the groups 100 have been arranged pointing in the opposite direction. The way in which the arrows showing the throughflow can be understood, is achieved in that the cuts 12 in the rear group or groups 100 are just as flown as the cuts 12 in the front group 100.
The Fig. 3 shows the disadvantages of the prior art, which include the fact that there is a significant turbulence of the flowing through the heat transfer fin medium, such as the cooling air, at the trailing edge 12.2 of the section 12 , for example, increases the pressure loss. According to the Applicant, this also does not change much if the methods described in the opening paragraph above change that WO 2004 / 065879A1 Proposed flattening of the leading and trailing edges 12.1, 12.2 of the cuts is provided. The Fig. 2 represents an embodiment of the invention, which is noticeably different from the prior art. It should also be noted that the dimensional design of the cuts 12 is very small, which can be arranged on a given area unit significantly more cuts 12 than in the prior art, which then leads to an equally significant increase The number of flow starts or the leading edges leads, so that the heat exchange efficiency - also because of the provided larger surface - is to improve significantly. The dimensionally small design of the cuts 12 is, inter alia, expressed by the fact that the distances between the adjacent tape thinning lines 8 are in the range of 1.0 mm or even less. (see Fig. 7 )
Finally, the shows Fig. 12 a partial view of a heat exchanger consisting of tubes 2 and fins 1 . In this case, approximately planar heat transfer fins 1 were provided which have openings 20 . The openings 20 are surrounded by a raised edge 21 . Through the openings 20 through the tubes 2 are inserted and soldered to the ribs 1 . As can be seen, in this embodiment, the ribs 1 are each provided with two groups of cuts 12 and an intermediate web 15 . Here, however, there is complete freedom of design. The ribs 12 have the features and effects described above. Only five tubes 2 and four superimposed ribs 1 were drawn, whereby the principle, however, can be seen clearly enough. The block arrows are to indicate the flow through the ribs 1 by means of, for example, the cooling air. The other arrows indicate the flow through the tubes 2 by means of, for example, the coolant of a motor vehicle.

In principle, it is possible and if necessary expressly provided to heat the forming tools 30, for example by means of a heater, in order to influence the forming properties of the inserted fin material 3 . The two flashes in the Fig. 8 40 are intended to indicate an electric heater. The heater can be located in the upper tool and / or in the lower tool

The Fig. 9 shows some investigated cross-sectional shapes of the cuts 12. All sections have cross-sectional shapes with a thickening 10 , which goes beyond the thickness of the parent sheet metal strip. The cross-sectional shape in the 3rd column, under No. b, shows on average compared with that in the Fig. 3 State of the art (State of the art in Fig. 9 ) an approximately 15% improvement in the heat transfer coefficient (Hcoef) , which leads to an improved ratio of heat transfer to pressure loss. The cross-sectional shape in the left Column (No. e) leads to a reduction of the pressure loss by 25% with almost the same heat transfer coefficient (Hcoef). Also the cross-sectional profile in the 4th column, under no. c, has a remarkable result. With a pressure loss reduction of about 10%, a better heat transfer coefficient is reported by about 3%.

Claims (19)

1. Heat-exchanging fin (1) that is arranged between tubes (2) in which flows a medium that is in heat-exchanging contact with another medium that flows through the heat-exchanging fin (1), with it being possible for the heat-exchanging fin (1) to be produced from a thin sheet-metal strip (3), out of the plane of which are arranged turned-out slices (12) that have front and rear edges (12.1, 12.2) that are shaped, preferably tapered, characterized in that the slices (12) have, between the front and rear edges (12.1, 12.2) in cross section, a thickened portion (10) that is thicker than the thickness of the sheet-metal strip (3), with the front and rear edges (12.1, 12.2) of the slices (12), before the latter are turned out, being situated approximately on strip thinning lines (8) that run parallel in the strip longitudinal direction.
2. Heat-exchanging fin according to Claim 1,
   characterized in that the heat-exchanging fin (1) is shaped in the manner of a wave with wave peaks (4) and wave troughs (5) that are connected by wave flanks (11), with the slices (12) being situated in the wave flanks (11).
3. Heat-exchanging fin according to Claim 1,
   characterized in that the heat-exchanging fin (1) is approximately planar and has openings (20) through which the tubes (2) can be inserted.
4. Heat-exchanging fin according to one of Claims 1-3, characterized in that the slices (12) have, in cross section, the shape of a dolphin or of a tuna fish or of a penguin or of a droplet.
5. Heat-exchanging fin according to Claim 1, 2 or 4,
   characterized in that the strip thinning lines (8) also extend over the wave peaks (4) and wave troughs (5), as a result of which a surface profiling is also formed in the wave peaks (4) and the wave troughs (5).
6. Heat-exchanging fin according to one of the preceding claims, characterized in that the slices (12) are arranged in sets of slices (12), with interruptions, which run in the strip transverse direction, of the slices (12) being provided between the sets of slices (12), which interruptions form connecting strips (9).
7. Heat-exchanging fin according to Claim 6,
   characterized in that the sets of slices (12) are divided into groups of slices (12) by means of parallel-running webs (15).
8. Heat-exchanging fin according to one of the preceding claims, characterized in that parallel-running connecting strips (9) that run transversely with respect to the strip longitudinal direction are provided, which connecting strips (9) are formed by the spacings between the slices that are arranged in the strip longitudinal direction, or which connecting strips (9) constitute the interruptions of said slices (12).
9. Heat-exchanging fin according to Claim 1, 2 or 8,
   characterized in that the connecting strips (9) run within the wave flanks (11).
10. Heat-exchanging fin according to Claim 1, 2 or 8,
    characterized in that the connecting strips (9) are arranged in the wave peaks (4) or wave troughs (5).
11. Method for producing heat-exchanging fins (1) from a sheet-metal strip (3) that runs through profiled roller sets (30) or through embossing and cutting tools, with slices (12) that are turned out of the plane of the sheet-metal strip being formed,
    characterized by the following steps:

    a) the sheet-metal strip (3) is thinned in the longitudinal direction of the strip in parallel-running lines (8),

    a1) thereby forming band thinning lines (8) that are arranged at intervals and that run parallel in said longitudinal direction;

    b) intermittent separating cuts are formed in the strip thinning lines (8);

    b1) with connecting strips (9) that run in the strip transverse direction being formed between the separating cuts;

    c) and with the slices (12) being created by turning out the separating cuts.
12. Method according to Claim 11, characterized in that step c) comprises deforming the slices (12) between the start and the end of the separating cuts.
13. Method according to Claim 11 or 12, characterized in that step c) is carried out in such a way that, in cross section between the front and rear edges (12.1, 12.2) of the slices (12), a thickened portion (10) is formed that is thicker than the thickness of the sheet-metal strip (3).
14. Method according to one of Claims 11 - 13,
    characterized in that, following said steps,

    d) a corrugation of the strip is carried out transversely with respect to the longitudinal direction of the strip,

    d1) with either the wave peaks (4) or wave troughs (5) coming to rest in each case in the region of the connecting strips (9),

    d2) or with the corrugation of the strip being carried out such that the connecting strips (9) run in each case in the region of the slices (12) or the wave flanks (11).
15. Method according to Claim 14, characterized in that the wave peaks (4) and the wave troughs (5) are of approximately semi-circular design.
16. Method according to Claim 14, characterized in that the wave peaks (4) and the wave troughs (5) are of flat design, with the wave flanks (11) being bent away from the wave troughs or wave peaks by approximately 90° and running approximately parallel to one another.
17. Method according to Claim 11, characterized in that step a) includes forming strip thinning lines (8) that run continuously in the longitudinal direction of the sheet-metal strip (3).
18. Method according to one of the preceding claims,
    characterized in that the production tools are heated.
19. Heat exchanger composed of tubes and heat-exchanging fins, characterized in that the heat-exchanging fins (1) are designed according to Claim 1 or have been produced according to method Claim 11.

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