DE102010033468B4 - heat exchanger - Google Patents

Abstract

Heat exchanger (1) with the following features: a) Ribs (7, 17) are arranged between mutually parallel, fluid-carrying tubes (2, 14); b) The ends of the tubes (2, 14) are connected to tube sheets (3, 4 ) fixed;c) The ribs (7, 17) are designed as rib strips which run in a zigzag shape and extend in the longitudinal direction (L) of the tubes (2, 14);d) The ribs (7, 17) have Rib crests (8) between which rib flanks (9) extend;e) The rib crests (8) of the ribs (7, 17) are supported alternately on the adjacent tubes (2, 14), the ribs (7, 17 ) rest against the tubes (2, 14) without a material connection; f) the tubes (2, 14) engage in open recesses (10, 16) in the rib crests (8) on the edge side of the rib crests (8); g) the rib flanks ( 9) are at an angle (W) deviating from 90° to the longitudinal axis (L) of the tubes (2, 14); h) the ribs (7, 17) are supported on the tube sheets (3, 4) or on the Tube sheets (3, 4) arranged and de n ribs (7, 17) facing spacer elements, the distance between the tube sheets (3, 4) is reduced, so that the ribs (7, 17) by a prestressing force acting in the longitudinal direction of a ribbed band and parallel to the tubes (2, 14). (F) are prestressed.

Description

The invention relates to a heat exchanger having the features of patent claim 1 and a method for producing a heat exchanger according to the features of patent claim 11.

Heat exchangers are state-of-the-art in a wide variety of designs. The heat exchange takes place between a liquid, which flows through the tubes, and a gas, which flows around the outside of the tubes. The fins greatly increase the heat exchanger surface and intensify the heat transfer. The fluid-carrying tubes usually pass through tube sheets, so that the liquid medium, starting from so-called water chambers, can flow into several tubes at the same time. The tube sheet serves as a partition. It is also possible to join two tubes together using bends, so that the bends are on one side of the tube sheet and the tubes are on the other side.

It is known to form finned tube packs in which several fluid-carrying tubes together pass through finned sheets stacked on top of one another. The ribs are fixed to the tubes, for example, by expanding the tubes so that they are pressed against the openings in the ribs.

Although this manufacturing process is well-established, it always involves a certain amount of manufacturing effort, since it must be ensured that the individual ribs lie tightly against the outside of the tubes for good heat transfer.

Of course, material connections, in particular soldered connections, are also possible between the ribs and the tubes. through the U.S. 5,042,574A it is known, for example, to join aluminum-clad flat tubes made of steel using aluminum-silicon solder with corrugated aluminum fin webs in a tempering furnace. This type of connection has the disadvantage that soldering can only be produced indirectly by using flat tubes clad with aluminum. In addition to the comparatively high cost of providing various materials, there is also the disadvantage that the flat tubes, which are closed circumferentially by at least one longitudinal weld seam, must not be clad with aluminum in the welding zone during tube production, since otherwise a perfect weld cannot be guaranteed.

When using different materials, due to the different temperature expansion coefficients of aluminum and steel, for example, due to the necessary high soldering temperatures and due to the subsequent cooling to ambient temperature, strong material stresses arise, so that the parts connected to one another can warp, and even the soldered connection can break.

A fundamental problem in the production of large heat exchangers with correspondingly large fin surfaces is that the heating for soldering must be as uniform and slow as possible so that the solder used to connect the fins to the tubes is not heated too quickly in the area of the heat source and overheats in the process , while it has not yet reached the necessary temperature, for example in an area far from the heat source. The production is therefore time-consuming.

the U.S. 2,119,761 A discloses a heat exchanger in which fins are arranged between mutually parallel tubes. The ribs are designed as rib strips which extend in a zigzag shape in the longitudinal direction of the tubes and are supported with their rib crests on adjacent tubes. The tubes engage in recesses arranged at the edges of the ridges of the ribs. The rib flanks are at an angle deviating from 90° to the longitudinal axis of the tubes. The fins and tubes are all immersed in a bath of molten solder or other suitable metal to join the components together.

the U.S. 4,778,004 A discloses a corrugated fin heat exchanger. The tubes of the heat exchanger are wrapped around the fins like a helix. Recesses for receiving the tubes are formed in adjacent fin crests. Due to the helical arrangement, the recesses are offset from one another.

In the GB 1 099 687 A describes a heat exchanger arrangement in which tubes and fins are also connected to one another by a dip melting process. The fin bands have a corrugated structure and contact elliptical tubes located in recesses in the fin crests.

From the DE 10 2007 020 722 A1 a laminated fin for a heat exchanger is known. The rib has a zigzag shape. The fins on the fin are intended to help maximize the strength and stiffness of the fin and minimize a length of material required to manufacture the heat exchanger fin.

the DE 10 2007 004 993 A1 relates to a manufacturing process for flat tubes from at least one strip of endless strip material. The strip material is corrugated in a zigzag manner with respect to an inner part. Exhibitions are arranged between the wave troughs and wave crests to create turbulators. The corrugated sections are brazed to the inner tube.

the U.S. 2,063,757 A relates to a heat exchanger in which zigzag fins are arranged on flat tubes. The fins and flat tubes are bonded together for a brazing process or via a dip fusing process.

Proceeding from this, the invention is based on the object of demonstrating a heat exchanger with a mechanical tube-fin connection which is easy to produce and which does not require a materially bonded connection between the tubes and the ribs, but which nevertheless enables very good heat transfer and at the same time the combination of different materials permitted and can also be produced quickly.

This problem is solved in a heat exchanger with the features of patent claim 1 . A manufacturing method is the subject matter of patent claim 11.

The dependent claims relate to expedient developments of the idea of the invention.

1. a) Zwischen parallel zueinander verlaufenden, Fluid führenden Rohren sind Rippen angeordnet;
2. b) Die Enden der Rohre sind an Rohrböden fixiert;
3. c) Die Rippen sind als Rippenbänder ausgestaltet, die Zick-Zack-förmig verlaufen und sich in Längsrichtung der Rohre erstrecken;
4. d) Die Rippen besitzen Rippenkämme, zwischen denen sich Rippenflanken erstrecken;
5. e) Die Rippen stützen sich mit ihren Rippenkämmen abwechselnd an den angrenzenden Rohren ab, wobei die Rippen ohne stoffschlüssige Verbindung an den Rohren anliegen;
6. f) Die Rohre greifen in randseitig der Rippenkämme offene Ausnehmungen in den Rippenkämmen;
7. g) Die Rippenflanken stehen in einem von 90° abweichenden Winkel zur Längsachse der Rohre;
8. h) Die Rippen stützen sich an den Rippenböden ab oder auf an den Rohrböden angeordneten und den Rippen zugewandten Distanzelementen, wobei der Abstand der Rohrböden reduziert ist, so dass die Rippen durch eine in Längsrichtung eines Rippenbandes und parallel zu den Rohren wirkende Vorspannungskraft vorgespannt montiert sind.

The heat exchanger according to the invention has the following features:

1. a) Ribs are arranged between mutually parallel fluid-carrying tubes;
2. b) The ends of the tubes are fixed to tube sheets;
3. c) The ribs are designed as rib bands which run in a zigzag shape and extend in the longitudinal direction of the tubes;
4. d) The ribs have rib crests between which rib flanks extend;
5. e) The ribs are supported with their rib crests alternately on the adjoining tubes, the ribs lying against the tubes without a material connection;
6. f) The tubes engage in open recesses in the rib crests on the edge side of the rib crests;
7. g) The rib flanks are at an angle deviating from 90° to the longitudinal axis of the tubes;
8. h) The ribs are supported on the rib bases or on spacer elements arranged on the tube bases and facing the ribs, the distance between the tube bases being reduced so that the ribs are mounted prestressed by a prestressing force acting in the longitudinal direction of a ribbed band and parallel to the tubes .

A special fin design is used in the heat exchanger concept according to the invention, which makes use of the thermal expansion of the fins and tubes in order to enable improved heat transfer between tube and fin. The heat exchanger design according to the invention is independent of the materials of the tube and the fin. It is also possible to combine very different materials with one another. A materially bonded connection is also conceivable, but not necessary in principle.

In the heat exchanger design according to the invention, zigzag-shaped ribbed bands are provided, with the individual sections being designed to a certain extent in the shape of a trapezium. A meander shape results. Recesses, into which the tubes engage, are arranged in each case in the tips or rib crests of the adjoining trapezoidal regions. The tubes are not intended to pass through the ribs, only that the tubes are located adjacent to the ribs. The ribs are only pressed against the tubes on the circumferential side.

An essential feature of the invention is that the rib flanks are at an angle deviating from 90° to the longitudinal axis of the tubes. Since the tubes as well as the fins expand when the heat exchanger is in operation, the contact pressure between the fins and the tubes should increase when the heat exchanger is in operation. The ribs are therefore mounted in such a way that the ribs can stretch, but cannot move indefinitely in the longitudinal direction of the tubes. This ensures that the contact pressure resulting from thermal expansion is actually transferred from the ribs to the tubes.

Another significant advantage is that, compared to previous production methods, there is no need to expand the pipes. The expansion of pipes does not necessarily lead to a reduction in wall thickness, but to a reduction in length. However, due to the existing tolerances in the wall thickness, the widening also means that the tubes are of different lengths after the widening and the ends of different lengths have to be adapted to the position of the tube sheet. It is therefore with a corresponding addition to the pipe length worked, which is not required in every case. Excess pipe lengths must be cut off, for example by drilling. Drilling produces a relatively large number of chips, which is undesirable in terms of production technology, but is the better alternative to sawing off, because sawing creates vibrations that can impair the connection between the tube sheet and the tube. It would therefore be best if the cutting or machining step could be eliminated entirely. This is possible with the solution according to the invention. All tubes are the same length and do not need to be shortened.

Another advantage is that the tube itself participates in the heat exchange compared to stacked finned tube heat exchangers of certain designs. This is to be understood in such a way that, in the prior art, when the ribs are stacked one on top of the other, the distance between the ribs is adjusted via the height of the collar-like projections, which are formed in the area of the tubes. In the assembled position, the tabs abut each other so that the entire surface of the heat exchanger tube is completely enveloped by the fins. This is different in the heat exchanger according to the invention: There are free surface areas of the tubes, which thus come into direct contact with the heat exchange medium and ensure direct heat transfer.

The heat exchanger according to the invention not only enables very cost-effective production, but also high flexibility in the choice of material, since there is no need for more expensive, materially bonded connection techniques. With all materials that come into question, a thermally induced expansion occurs, which inevitably always leads to the individual ribs being pressed firmly against the pipes due to expansion. It is irrelevant whether the pipe stretches more or whether the rib stretches more than the other component.

The fins are mounted preloaded by a biasing force acting longitudinally of the fins and parallel to the tubes. The preload can be applied by reducing the spacing of the tubesheets. It is assumed here that the ribbed bands are supported on the tube sheets. Of course, tube sheets of different thicknesses can also be used, or uniform tube sheets that are provided with spacer elements on their side facing the ribs, on which the ribs are supported. The contact pressure that occurs during operation is reliably achieved with a certain pre-tensioning force. In addition, improved heat transfer is achieved as a result of the prestressing right from the start of operation, i.e. at temperatures below the target operating point.

The heat transfer can also be improved in that the recesses have a collar, via which the recesses and thus also the ribs are supported on the tubes. The individual ribs are in contact with the adjacent tubes over a larger area via such collars. This improves the heat transfer. At the same time, the surface pressure between the tubes and the expanding ribs is reduced somewhat, which can be an advantage with thin ribs or thin-walled tubes. The collar can also compensate for certain manufacturing tolerances.

It is considered particularly advantageous if the rib flanks have reinforcements which increase the buckling resistance between the rib crests. The concept of the heat exchanger according to the invention is based on the mutual expansion of the tubes and ribs creating a form-fitting connection between the tubes and ribs. The pressing force should not be reduced by buckling the rib flanks. The rib flanks must therefore have a specified minimum buckling resistance. Within the scope of the invention, this minimum buckling resistance is preferably not achieved by accumulation of material, ie by thicker-walled rib flanks or local reinforcements on the rib flanks, but by stiffening, which is in particular formed as embossing. Such embossing serves to move material outwards from the center plane of the rib flanks and thereby increase the flexural rigidity. The shape of the stiffeners plays an important role here, since the buckling resistance between two rib crests must be increased. In a preferred embodiment, it is therefore provided that at least one reinforcement extends between a recess in a first ridge of ribs in the direction of the adjacent recess in the opposite ridge of ribs. The stiffeners therefore run to a certain extent diagonally on the ribbed bands. Viewed in the longitudinal direction of the tubes, ie viewed from the direction of the tube sheet, the reinforcements thus extend radially from one tube to the adjacent tube. An additional stiffening in the region of a rib crest is not required, since the rib crest itself is bent once, preferably twice, and is therefore sufficiently rigid.

The exact contouring and position of the reinforcements depends on the geometry of the heat exchanger tubes. It is therefore also conceivable that the reinforcements are perpendicular to the ribs run comb, which can be particularly advantageous in cross-section elliptical tubes.

In principle, it is considered advantageous if the reinforcements extend in the form of embossings into the individual collars that are formed on the recesses. As a result, the wall of the stiffening transitions directly into the collar, as it were, provided that the stiffening in the form of embossing and the collar are oriented in the same direction.

A compact design of the heat exchanger is given in particular when the tubes are arranged in a plurality of rows which are offset relative to one another. This results in the recesses being offset from one another in the longitudinal direction of adjacent rib crests. The offset of the recesses thus also determines the exact position of the reinforcements, in the form of web-like embossing.

1. a) Bereitstellen von Rohren und Rippen, wobei die Rippen zu Zick-Zack-förmigen Rippenbändern gebogen und mit randseitigen Ausnehmungen versehen sind;
2. b) Anordnen der Rohre zwischen den Rippen, wobei die Rippen ohne stoffschlüssige Verbindung an den Rohren anliegen;
3. c) Aufbringen einer Vorspannkraft auf die Rippen, um die Rippenkämme gegen die Rohre zu pressen, indem der Abstand zwischen Rohrböden reduziert wird, an welchen die Rohre angeordnet werden;
4. d) Fixieren des Rohrbodens in der Position, in welcher die Vorspannkraft auf die Rippen aufgebracht wurde, wobei die Rohre mit dem Rohrboden stoffschlüssig durch Schweißen, Löten, Kleben oder durch Aufweiten verbunden werden.

A method for producing a heat exchanger according to one of the preceding claims is the subject of patent claim 11. The method comprises the following steps:

1. a) providing tubes and ribs, the ribs being bent to form zigzag-shaped rib strips and provided with edge-side recesses;
2. b) arranging the tubes between the ribs, the ribs resting against the tubes without a material connection;
3. c) applying a biasing force to the fins to press the fin crests against the tubes by reducing the distance between tubesheets on which the tubes are placed;
4. d) Fixing the tube sheet in the position in which the prestressing force was applied to the ribs, the tubes being connected to the tube sheet by welding, soldering, gluing or by expanding in a materially bonded manner.

The method according to the invention has considerable advantages both compared to the production of heat exchangers with expanded tubes and compared to heat exchangers in which the tubes and ribs are materially connected, due to the very high rationalization potential. In practice, the fins and tubes are first to be stacked alternately on top of each other. The package of fins and tubes must then be aligned so that the tubes fit snugly in or against the tube sheet. The pack is placed between side walls and compressed by sliding at least one tube sheet relative to the other tube sheet. In this position, in which a prestressing force is applied to the ribs, the tube sheet is fixed. The tubes can be integrally connected to the tube sheet by welding, soldering, gluing or by expanding. Depending on the application, the tube sheet can be absolutely tight or, in the case of leaks that can be tolerated to a limited extent, also be fastened very simply. Decisive for the present invention is not the type of attachment and the exact position of the tube ends, which can only bear on the front side of the tube sheet or alternatively partially or completely penetrate it, but the function of the tube sheet as an abutment for the ribs. It is also possible within the scope of the invention to provide separate abutments on which the ribs are supported, while the tube sheets primarily have a sealing function. Functionally, such abutments belong to the tube sheet.

In order for the outer ribs of a heat exchanger to lie tightly against the tubes, it must be ensured that the housing is sufficiently stable or exerts sufficient force on the edge ribs so that the entire system does not bulge outwards. Additional tie rods may therefore be provided to transversely constrain the package of tubes and fins against lateral expansion and to maintain the prestressing force between the fins and the tubes.

• 1 eine perspektivische Darstellung eines ersten Ausführungsbeispiels eines Wärmetauschers;
• 2 eine Ansicht von oben auf den Wärmetauscher der 1 ;
• 3 eine Ansicht in Richtung der Rohre des Wärmetauschers der 1 ;
• 4 eine Ansicht auf die Rohre und Rippen des Wärmetauschers der 1 ohne umgebendes Gehäuse und ohne Rohrböden;
• 5 eine Seitenansicht auf die Rohre und Rippen des Wärmetauschers der 1 ohne Seitenteile und Rohrböden;
• 6 eine Querschnittdarstellung durch die Rohre und Rippen des Wärmetauschers der 1 ;
• 7 eine perspektivische Darstellung der Rohre und Rippen des Wärmetauschers der 1 ;
• 8 bis 10 in der Draufsicht, Seitenansicht und Stirnansicht ein einzelnes Rippenblech des Wärmetauschers der 1;
• 11 das Rippenblech der 8 bis 10 in perspektivischer Darstellung;
• 12 eine perspektivische Darstellung einer zweiten Ausführungsform von Rohren und Rippen eines Wärmetauschers;
• 13 eine Seitenansicht auf das Paket aus Rohren und Rippen gemäß 12;
• 14 eine gegenüber der 13 um 90° versetzte Ansicht auf das Rippenrohrpaket der 12 (Ansicht von oben);
• 15 das Rippenrohr der Rippenrohrpakete der 12 in der Stirnansicht;
• 16 ein einzelnes Rippenblech des Wärmetauschers der 12 in perspektivischer Ansicht und
• 17 bis 19 eine Draufsicht, Seitenansicht und Stirnansicht des Rippenblechs der 16.

The invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawings. It shows:

• 1 a perspective view of a first embodiment of a heat exchanger;
• 2 a top view of the heat exchanger 1 ;
• 3 a view towards the tubes of the heat exchanger of FIG 1 ;
• 4 a view of the tubes and fins of the heat exchanger of FIG 1 without surrounding housing and without tube sheets;
• 5 a side view of the tubes and fins of the heat exchanger of FIG 1 without side panels and tube sheets;
• 6 a cross-sectional view through the tubes and fins of the heat exchanger of FIG 1 ;
• 7 a perspective view of the tubes and fins of the heat exchanger of FIG 1 ;
• 8th until 10 in the top view, side view and end view a single ribbed plate of the heat exchanger 1 ;
• 11 the rib sheet of 8th until 10 in perspective view;
• 12 a perspective view of a second embodiment of tubes and fins of a heat exchanger;
• 13 a side view of the package of tubes and fins according to FIG 12 ;
• 14 one opposite the 13 View of the finned tube package offset by 90° 12 (View from above);
• 15 the finned tube of the finned tube bundles 12 in front view;
• 16 a single fin plate of the heat exchanger 12 in perspective view and
• 17 until 19 a plan view, side view and end view of the rib plate of FIG 16 .

1 shows a heat exchanger 1. The heat exchanger 1 is very compact in this embodiment. It is noted that in practice the tubes shown can be many times longer. The heat exchanger 1 can also be built much larger overall. The exemplary embodiment shown serves only to explain the idea of the invention and is by no means to scale. In addition, in the following description of the figures, terms such as top, bottom, left, right, front, rear, etc. refer exclusively to the exemplary representation and position of the depicted heat exchanger 1 and its components selected in the respective figures. The terms are not to be understood as restrictive, that is, these references can change in different working positions or through a mirror-symmetrical design of the like. The heat exchanger 1 shown has a plurality of fluid-carrying tubes 2. All tubes 2 run parallel to one another. The tubes 2 are straight. They extend between tube sheets 3, 4 that are opposite one another and run parallel to one another through a material connection (welding, soldering) or through a form-fitting connection such as rolling.

In addition to the tube sheets 3, 4, side walls 5, 6 are provided as further housing components, which are located between the tube sheets 3, 4 and delimit a rectangular interior. It goes without saying that the shape of the interior is largely determined by the arrangement of the tubes and the shape of the tube sheet (circle, rectangle).

In this interior space, which is penetrated by the tubes 2 arranged in mutually parallel and offset rows, there are also ribs 7. There are a total of nine rows of ribs 7, which enclose eight rows of tubes offset in relation to one another. The ribs 7 are designed as individual rib bands which run in a zigzag shape and each extend between two adjacent rows of tubes. This is particularly good based on the 2 and 3 to recognize. In 3 eight rows or columns of tubes 2 can be seen due to the selected representation. Columns with three and four tubes 2 always alternate in each case. Between these columns are the in 2 ribs 7 shown in the form of ribbed bands. It can be seen that the ribs 7 only partially enclose the tubes 2 . The ribs 7 have rib crests 8 for this purpose. The rib flanks 9 extending between the rib crests 8 are at an angle W deviating from 90° to the longitudinal axis L of the tubes 2 ( 6 ). In this embodiment, the angle W is 108°. The angle W can be reduced by applying a prestressing force F to the ribs 7 . In 2 the direction of this prestressing force F is drawn in. It is assumed that the side walls 5, 6 are long enough for a defined prestressing force F to be exerted on the ribs 7. In the relaxed state, the angles W between the rib flanks 9 can therefore be larger than shown in the drawings.

From the representation of 4 it becomes clear that the individual ribs 7 in this perspective have a rectangular basic contour to a certain extent, which also applies to the visible rib flanks 9 . The rib flanks 9 are provided with recesses 10 only at the edges, ie in the region of their rib crests 8 , which recesses are adapted to the outer contour of the tubes 2 . Because of the tubes 2 shown here, which are circular in cross section, the recesses 10 are arc-shaped. They extend approximately over an angular range of 135°, so that in this exemplary embodiment 270° or 3/4 of the circumference of a tube 2 is surrounded by recesses 10 of the ribs 7 . Thus remain between the successive ribs 7 narrower column 11, the width of the column 11 as shown in FIG 4 corresponds to approximately half the width B of the ribs 7 in the viewing direction shown.

All the ribs 7 are configured uniformly. Due to the mutually offset arrangement of the tubes 2, the recesses 10 in the rib crests 8 are also arranged offset from one another. In this exemplary embodiment, each rib 7 therefore has four recesses 10 in one rib crest 8 and four recesses 10 in the opposite rib comb 8 three recesses 10. The recesses 10 can also be seen in the edge rib 7, as in particular from the perspective of FIG 5 you can see.

A special feature of the ribs 7 shown are stiffeners 12, which are shown in the 4 run diagonally and always point from one tube 2 to the next tube 2, which touches the crest of the ribs 8 on the opposite side. This results in a diamond-like pattern.

The stiffeners 12 increase the buckling resistance between two rib crests 8. They are web-like embossments that run parallel to the radially shortest connection between adjacent tubes 2. Specifically, two web-shaped embossings are provided in this exemplary embodiment. Each of the embossings opens into the diagonally opposite recess 10 in the other rib crest 8. The stiffeners 12 have this orientation because this is the shortest connection between two adjacent tubes 2 and here due to the thermal length change with the highest contact pressure that occurs between the tube 2 and the rib 7 acts, is to be expected.

The representation of 5 is a view of the rib crests 8. It can be seen that the rib crests 8 are not pointed but designed in the manner of a plateau. This gives them a rectangular shape. The rib crests 8 are many times narrower than the adjacent rib flanks 9. The rib crests 8 also include the recesses 10 in the rib crests 8, the recesses 10 being provided with collars 13. The collars 13 are each turned inwards, as shown in FIG 6 can be seen. This means that the collars 13 on a rib crest 8 do not point outwards, but to a certain extent inwards, so that the opening provided by the recess 10 in the rib crest 8 is reduced. From the perspective of 5 it can be seen that the opening thereby has the shape of a flat oval.

All ribs 7 are mirrored. This means that a tube 2, such as that in 7 is marked, when it is surrounded on one side by a recess 10 in the rib 7 on the right in the plane of the drawing, at the same height or in its same length section also on the opposite side by a recess 10 in the other rib 7 is surrounded. As a result, no bending forces are introduced into the tubes 2. The circumferential support always takes place in the same length section of a tube 2. This also ensures that thermally induced changes in length lead directly to an increased contact pressure and not to a deformation of the ribs 7 or the tubes 2.

The fact that the stiffeners 12 in the form of web-like embossing do not end in front of, ie at a distance from, the collar 13 also contributes to the design of the thin-walled ribs 7 that is as rigid as possible, but pass through the collar 13 or open into it. This is particularly good in 11 to recognize. There you can see the web-like beads or embossments, which extend in the same direction as the collars 13, into which they open. As a result, the collar 13 has openings, so to speak. In this exemplary embodiment, there are four openings that are arranged more or less equidistantly due to the selected spacing of the stiffeners 12 . While the stiffeners 12 ensure power transmission in the transverse direction or diagonally to the rib flanks 9, in 11 also clearly recognize that the rib crests 8 also have sufficient flexural rigidity due to their bevels relative to the rib flanks 9, so that forces in the longitudinal direction of the rib crest 8 can also be transmitted well.

The embodiment of 12 until 19 differs from that of 1 until 11 by two features: Firstly, the tubes 14 are not circular in cross-section, but elliptical, and secondly, the reinforcements 15 run perpendicular to the rib crests 8. Accordingly, the recesses 16 ( 15 ) also adapted to the elliptical shape of the tubes 14. The remaining reference numbers for this form of tubes 14 and fins 17 have been given with reference to FIG 1 until 11 adopted because they designate identical components. However, the difference between the stiffeners 12 is significant 1 until 11 and those stiffeners 15 at the 12 until 19 is shown. Due to the differently oriented reinforcements 15, there is also a different course of force within the ribs 17. The individual tubes 14 are as in the first embodiment ( 1 until 11 ) offset from each other. The reinforcements 15 are in turn web-like expressions which point in the same direction as the collars 13 . All stiffeners 15 are arranged equidistantly, with two of the stiffeners 15 opening into the ends of a recess 16 . The bracing 15 in between is located at the deepest point or apex of the recess 16 and ends in the opposite rib crest 8. The central bracing 15 is intended to initiate the thermal expansion in the rib crest 8, so that the rib 17 is stretched in this area . This stretching causes the adjacent recess 16 in this crest of ribs 8 to fit snugly against the associated tube 14 .

Reference List

1

heat exchanger

2

Pipe

3

tube sheet

4

tube sheet

5

Side wall

6

Side wall

7

rib

8th

rib comb

9

rib flank

10

recess

11

gap

12

bracing

13

collar

14

Pipe

15

bracing

16

recess

17

rib

B

Broad

f

preload force

L

longitudinal direction

W

angle

Claims (11)

Heat exchanger (1) with the following features: a) Ribs (7, 17) are arranged between mutually parallel, fluid-carrying tubes (2, 14); b) The ends of the tubes (2, 14) are fixed to tube sheets (3, 4); c) the ribs (7, 17) are designed as rib strips which run in a zigzag shape and extend in the longitudinal direction (L) of the tubes (2, 14); d) the ribs (7, 17) have rib crests (8) between which rib flanks (9) extend; e) The ribs (7, 17) rest alternately with their rib crests (8) on the adjacent tubes (2, 14), the ribs (7, 17) bearing against the tubes (2, 14) without a material connection; f) the tubes (2, 14) engage in open recesses (10, 16) in the rib crests (8) on the edge side of the rib crests (8); g) The rib flanks (9) are at an angle (W) deviating from 90° to the longitudinal axis (L) of the tubes (2, 14); h) The ribs (7, 17) are supported on the tube sheets (3, 4) or on spacer elements which are arranged on the tube sheets (3, 4) and face the ribs (7, 17), the distance between the tube sheets (3, 4) is reduced so that the ribs (7, 17) are mounted prestressed by a prestressing force (F) acting in the longitudinal direction of a ribbed band and parallel to the tubes (2, 14). Heat exchanger (1) after claim 1 , characterized in that the recesses (10, 16) have a collar (13) via which the recesses (10, 16) are supported on the tubes (2, 14). Heat exchanger (1) after claim 1 or 2 , characterized in that the rib flanks (9) have reinforcements (12, 15) which increase the buckling resistance between two rib crests (8). Heat exchanger (1) after claim 3 , characterized in that the reinforcement (12) is designed as an embossing. Heat exchanger (1) after claim 3 or 4 , characterized in that the at least one reinforcement (12) extends between a recess (10) in one rib crest (8) in the direction of the adjacent recess (10) in the opposite rib crest (8). Heat exchanger (1) according to one of Claims 1 until 5 , characterized in that the reinforcements (15) extend perpendicularly to the rib crests (8). Heat exchanger (1) according to one of Claims 4 until 6 , characterized in that the reinforcements (12, 15) extend into the collar (13) in the form of embossing. Heat exchanger (1) according to one of Claims 1 until 7 , characterized in that the reinforcements (12, 15) are formed by a bar-shaped embossing or by a plurality of bar-shaped embossings running parallel to one another. Heat exchanger (1) according to one of Claims 1 until 8th , characterized in that the tubes (14) are elliptical in cross-section. Heat exchanger (1) according to one of Claims 1 until 9 , characterized in that the recesses (10, 16) in the longitudinal direction (L) of adjacent rib crests (8) are arranged offset to one another. Method for producing a heat exchanger (1) according to one of the preceding claims, having the following steps: a) providing tubes (2, 14) and ribs (7, 17), wherein the ribs (7, 17) are bent to form zigzag-shaped rib bands and are provided with recesses (10, 16) at the edges; b) arranging the tubes (2, 14) between the ribs (7, 17), the ribs (7, 17) bearing against the tubes (2, 14) without a material connection; c) applying a prestressing force to the fins (7, 17) to press the fin crests (8) against the tubes (2, 14) by reducing the distance between the tube sheets (3, 4) on which the tubes ( 2, 14) are placed; d) fixing the tube sheet (3, 4) in the position in which the prestressing force was applied to the ribs (7, 17), the tubes (2, 14) being integrally bonded to the tube sheet (3, 4) by welding, soldering , gluing or by expanding.

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