EP3087337B1 - Heat exchanger with a circumferential seal - Google Patents

Description

The present invention relates to a heat exchanger having a base, a seal and a cover according to the preamble of claim 1.

The connection of a cover to a base (tube sheet) of a heat exchanger requires a reliable seal between the two elements mentioned in order to reliably prevent the leakage of coolant and thus a possible failure of the heat exchanger or an assembly to be cooled by it. Such a base of such a heat exchanger is often provided as a tube sheet with corresponding passages through which, for example, flat tubes are drawn. Said cover can be designed, for example, as a coolant box and thus contain coolant. A reliable seal between the cover and the base is usually achieved by means of a seal which is inserted into a corresponding receiving groove in the base. The receiving groove actually consists of two parallel receiving grooves, which are arranged orthogonally to the passages in the base at the edge of the base and are also produced when the base is punched or reshaped. The seal runs between the two receiving grooves orthogonally to the same, usually also at the edge of the base in a specially designed groove.

In order to be able to make such circumferential receiving grooves or grooves between the passages in the tube sheet, a punching tool for a tray size or a comparatively complex family tool is required, especially if the tube sheets are to have different lengths.

From the EP 2 498 040 A2 A heat exchanger is now known which does not provide a circumferential groove in the edge region of the base for precise sealing of the base with the cover, into which a seal in the form of a circumferential sealing ring is to be inserted and onto which the cover is then placed or pressed. Rather, in the known heat exchanger, a base can now be used which can be manufactured by the meter and which is cut to size according to the heat exchangers to be manufactured. For this purpose, the circumferential sealing element or the circumferential seal is inserted into two opposing receiving grooves and additionally guided at the ends of these receiving grooves over a surface of the base between two passages.

From the FR 2 822 532 B1 another heat exchanger is known.

The present invention is concerned with the problem of addressing an alternative embodiment for a heat exchanger of the generic type, which in particular enables simplified manufacture.

This problem is solved according to the invention by the subject matter of independent claim 1. Advantageous embodiments are the subject of the dependent claims.

The present invention is based on the general idea of creating a heat exchanger whose bottom (tube bottom) is to be manufactured by the meter and can therefore be used in a comparatively flexible manner for heat exchangers of different sizes. The heat exchanger according to the invention comprises a base, a seal and a cover, the base, usually also called tube base, having two parallel spaced apart grooves extending in the longitudinal direction of the base, which are located on two opposite sides of the Arranged at the bottom and designed to receive side projections of the cover. Each of these grooves also has a groove base. The base has at least three passages, ie openings for flat tubes, which are arranged parallel to one another and spaced apart from the receiving grooves in a plane and extend perpendicular to and between the receiving grooves. An intermediate region is formed in one plane between two such passages, which is arranged at a height difference h parallel to the groove bases of the receiving grooves. Between each intermediate area and the groove bases, a ramp runs parallel to the longitudinal direction of the passages, the ramps being parallel to one another. The seal itself is designed as a circumferential sealing cord. According to the invention, the seal now runs in the receiving grooves and each with a sealing web over two ramps and an intermediate area in between, the ramps being inclined at an angle of 20 ° <α <65 ° with respect to the plane of the intermediate area, ie usually with respect to the horizontal, or have an S-shaped profile, a turning point W in the range of 10% to 80% of the height difference h being arranged starting from the groove bottom of the receiving groove. In addition, in both variants the ramps are rounded at the transition to the receiving groove or at the transition to the intermediate area with a corresponding radius R1, R2, in particular to minimize tensile and compressive stress peaks on the seal caused by sharp kinks in this seal. At the transition to the receiving groove, the ramp is rounded with a radius R1, whereas it is rounded at the transition to the intermediate area with a radius R2.

With the design of the base according to the invention it can be achieved that the seal is clamped in the assembled state without excessive surface pressure or deformation between the base and cover. The heat exchanger according to the invention is thus on the one hand the use of a continuous sheet formed as a bottom possible, and on the other hand at the same time ensures an optimal sealing effect, since the surface pressure or the deformation of the built-in seal does not exceed or fall below critical limit values. By choosing the angle α between 20 ° and 65 °, the sealing effect and the load on the seal can also be influenced. In the case of an angle of α <20 °, there would be disadvantages for the later forming process of the passage and disadvantages with regard to the lateral guidance of the seal along the receiving groove. At an angle of α> 65 °, the contact pressure exerted by the cover on the seal may be too low, so that the sealing effect may not be guaranteed. Even in the case of the variant with an S-shaped profile, improved contact between the seal and the floor and thus an improved sealing function can be achieved. Above or below the mentioned area, radii R1 and R2 would result which would either have a disadvantageous effect on the subsequent forming process of the passage or unfavorably on the width of the floor and thus also on the required installation space. If the turning point W is in the range of <10% of the height difference h, the result is an S-shaped ramp that either has a disadvantageous effect on the floor width and thus the installation space or has a disadvantageous effect on the seal with regard to the stress peaks. If the turning point W is in the range of> 80% of the height difference h, the result is an S-shaped ramp which has a disadvantageous effect on the subsequent forming process.

A ratio of the radius R1 or R2 to a radius R3 of the section of the sealing cord or seal in the receiving groove in the unpressed state is advantageously 0.3 <R1 / R3 <3.0 or 0.3 <R2 / R3 <3.0. Defining this range of the ratio between the radius of the curve of the ramp and the radius of the seal optimizes the sealing effect. Too low a ratio would in fact cause a leak due to insufficient surface pressure on the Cause the transition area between the receiving groove and the ramp, with too large a ratio causing too little contact pressure along the ramp and a disadvantage in terms of installation space due to a wider base.

A longitudinal end of a passage facing the receiving groove is expediently between 1 mm <a <15 mm, in particular between 2 mm <a <6 mm closer to the receiving groove than a transition from the ramp to the intermediate area. Through this area determined by means of tests and calculations, the maximum mechanical stress to be absorbed in the radius area of the respective passage can be reduced and thus the stress load on the floor can be reduced overall.

According to the invention, at least one of the ramps is designed as a groove which extends parallel to the longitudinal direction of the passages and in which the seal runs in sections, the ratio of the degree of groove filling through the seal in the groove and the at least one ramp to the degree of groove filling through the seal in the receiving groove in the pressed state of the seal is between 1.0 and 1.4. The degree of groove filling is defined as the ratio between the cross-section of the pressed seal and the free cross-sectional area. When designing the seal, a groove filling level between 70 and 85% is usually specified, on the one hand to ensure the sealing effect and on the other hand to create reserve volume for a possible swelling of the seal. The ratio specified above makes it possible to achieve that the seal can be optimally guided and fixed and, at the same time, a stronger compression can be achieved in the ramp area, which improves the sealing function. The compression should be greater in the area of the ramp than along the receiving groove in order to be able to ensure an optimal sealing effect.

The ramps expediently have a width b1 and the intermediate regions a width b2, the ratio b1 to b2 being between 0.3 and 1.0. In order to achieve optimal compression of the seal in the groove of the intermediate area and the receiving groove, the degree of groove filling should be between 70 and 100% at both points. However, since the contact pressure of the seal in the receiving groove and on the ramp varies, it is necessary to achieve the desired degree of groove filling between 70 and 100% by design. Theoretically, this can be done by varying the diameter of the seal along the ramp, in particular at the transition area, or by varying the free cross-sectional area along the ramp at the transition area. By varying the widths of the ramps or the intermediate areas, the desired degree of slot filling can be achieved in a particularly simple constructive manner. It is particularly advantageous if the cross section of the seal is> 40%, in particular between 50% and 70% of the cross section of the unpressed seal along the receiving groove.

In a further advantageous embodiment of the solution according to the invention, the seal has at least one prestressing web for reducing tensile stresses on the seal, the at least one prestressing web being arranged parallel to a sealing web. In this case, the sealing web of the seal runs over two ramps as well as an intermediate region outside the prestressing web running parallel to it. Prestressing webs can generally be components of the seal and ensure that it is under prestress along the receiving grooves, whereby tensile stress on the seal in the area of the transition between the passages can be reduced. This makes it possible to ensure the desired position of the seal both along the receiving groove and between the passages.

The cover is expediently designed as a box, which has longitudinal side projections on the outside of the box on two opposite sides, the side projections extending in the receiving grooves and having a protrusion protruding longitudinally beyond the seal.

The cover is advantageously designed as a box which has a box base, a projection for positioning the box on the floor being arranged on a longitudinal side on the outer area of the box base.

A projection for positioning the box on the floor can be arranged on the outer area of the side projection. The side protrusion is, for example, the box foot. Due to the position of the seal between the passages in the area of a narrow side, it is advantageous for pressing the seal if the connection between the base and the cover or box extends along the receiving groove at least to the point where the seal is sufficient the receiving groove turns over the ramp into the intermediate area. It is particularly advantageous here if the side projection has a protrusion along the receiving groove, which results in an H-shaped design. The H-shape is brought about by the two protrusions of the side projection on both sides in combination with the web of the side projection between the passages. The overhangs of the side protrusion can either end flush with the receiving groove or protrude beyond it.

According to the invention, the heat exchanger has a side part that is inserted through a passage in the bottom, with a side part overhang s for closing the bottom with the cover, the averaged distance between the side part and an adjacent, outer flat tube having the value q and where the ratio s through q is between 0.3 and 0.7. This ensures that an optimal sealing effect in the area of the sealing web, ie the intermediate area, can be ensured with minimal installation space. Theoretically, the ratio s to q can also assume a value greater than 0.7, in particular if partial or complete blocking of the outer tube is desired in the case of heat exchangers subject to high thermal loads. In this case, the cover geometry is to be designed in such a way that the outer wall of the cover completely prevents or at least reduces a flow through the outer tube or several of the outer tubes. Likewise, the cover geometry can also be selected in such a way that one or more guide elements restrict or completely prevent the flow against the outermost tube or tubes (flat tubes).

According to a further advantageous embodiment, all passages have the same contour and the same area. This enables a simple production of the floor with an endless sheet.

Furthermore, it can be advantageous if at least the two outer passages arranged at the lateral ends of the base have a surface area that differs from the otherwise identical surface area of the other passages by a factor of 0.8 to 1.3. This means that side parts with different wall thicknesses can be used, which increases the strength of the component.

Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures on the basis of the drawings.

It goes without saying that the features mentioned above and those yet to be explained below are not only used in the respectively specified combination, but can also be used in other combinations or on their own without departing from the scope of the present invention.

Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, with the same reference symbols referring to the same or similar or functionally identical components.

They show, each schematically,

Fig. 1

a sectional view through a heat exchanger with a cover, a base and a seal according to the prior art,

Fig. 2

a view from above of a floor according to the invention,

Fig. 3

a sectional view in the section plane AA through the floor according to FIG Fig. 2 in the area of a receiving groove, a ramp and an intermediate area,

Fig. 4

a diagram to illustrate the contact pressure FD of the seal as a function of the angle α of the ramp,

Fig. 5

a representation as in Fig. 3 , but with an S-shaped ramp,

Fig. 6

a diagram to illustrate a possible leakage L as a function of a radius R1 or R2 at the transition of the ramp to the receiving groove or to the intermediate area relative to the radius R3 of the seal,

Fig. 7

a view from above of the floor according to the invention to illustrate a distance a between a longitudinal end of a passage and the transition of the ramp to the intermediate area,

Fig. 8

a diagram to illustrate the dependence of the pipe stress σ _R on the distance a,

Fig. 9

a view from above of the floor according to the invention to illustrate the width b1 of the ramp and the width b2 of the intermediate area,

Fig. 10

a view from above and a sectional view of the seal belonging to the floor according to the invention to illustrate the course of the seal with sealing web and prestressing webs,

Fig. 11

a sectional view through the heat exchanger according to the invention to illustrate the protrusion s of a side wall and the distances between the individual flat tubes or an outer flat tube to the side wall,

Fig. 12

a diagram to illustrate the strength of the flanged connection created by the bent overhang s as a function of a ratio s / q,

Fig. 13

a sectional view through the heat exchanger according to the invention with a lateral overhang for fixing the cover on the floor.

According to the Figures 1 and 11 a heat exchanger 1 has a base 2, a seal 3 and a cover 4. According to the Figure 1 a heat exchanger 1 according to the prior art is shown, whereas according to FIG Figure 11 an inventive heat exchanger 1 is shown. If one now looks at the base 2, it can be seen that it has two parallel spaced apart grooves 5, 5 'extending in the longitudinal direction of the base 2, which are arranged on two opposite sides of the base 2 and for receiving side projections 6, the is the box foot 15, the lid 4 are formed. Each of the receiving grooves 5, 5 'has a groove base 7, 7'. In addition, the base 2 has at least three passages 8, which are arranged parallel to one another and spaced apart from the receiving grooves 5, 5 'in a plane and extend perpendicular to and between the receiving grooves 5, 5' (see in particular also the Figures 2 , 7th , 9 and 11 ). Flat tubes 9 are passed tightly through the passages 8, a side part 19 being inserted through each of the two outer passages. In the plane between two passages 8, an intermediate area 10 is formed, which is arranged parallel to the groove bases 7, 7 'of the receiving grooves 5, 5' by a height difference h (cf. Figures 3 and 5 ). In addition, a ramp 11 runs between each intermediate area 10 and the groove bottoms 7, 7 ′ parallel to the longitudinal direction of the passages 8, the ramps 11 of adjacent intermediate areas 10 being spaced parallel to one another. The seal 3 is designed as a circumferential sealing cord.

According to the invention, the seal 3 now runs in the receiving grooves 5, 5 'and each with a sealing web 12 (cf. Figure 10 ) over two ramps 11 and the intermediate area 10 in between, the ramps 11 are inclined according to the invention by an angle α between 20 and 65 ° with respect to the intermediate region 10 and usually also with respect to the horizontal (cf. Fig. 3 ), or have an S-shaped course (cf. Fig. 5 ), with a turning point W in the range of 10% to 80% of the height difference h starting from the groove bottom 7,7 'of the receiving groove 5,5'. In Fig. 3 the bottom 2 is cut out to illustrate the radius R2, but of course has no opening in this area. Each of the ramps 11 is rounded at the transition to the receiving groove 5, 5 'with a radius R1 and at the transition between area 10 with a radius R2. The radii R1 and R2 can of course be of different sizes, larger radii helping to reduce the stress peaks acting on the seal 3. Due to an angle α of less than 20 °, on the one hand disadvantages for the later forming process of the passage 8 and on the other hand the lateral guidance of the seal 3 along the receiving groove 5, 5 'can be reduced. At an angle of α greater than 65 °, the contact pressure F _D , which acts from the cover 4 on the seal 3, would be too low, which is clearly shown in FIG Figure 4 is shown. In the angular range of 20 ° <α <65 ° found through experiments, an optimal contact pressure F _D can be achieved, by means of which the desired sealing effect can be ensured. In the mentioned height range of the turning point W between 10 and 80% of the height difference h there would be radii R1 and R2 which are particularly favorable for the installation of the seal 3 on the floor 2. Below or above this mentioned area, radii R1 and R2 have emerged which would have an unfavorable effect on the width of the base 2 and thus on the required installation space. In addition, it is particularly advantageous that the base 2 according to the invention can now be produced as an endless sheet and thus extremely flexible heat exchangers 1 of the most varied of sizes can be produced.

In an advantageous further development of the solution according to the invention, a ratio of the height difference h to the diameter D of a section is Seal 3 in the receiving groove 5, 5 'in the unpressed state 0.7 <h / D <2.5, preferably 1.0 <h / D <2.0. With the ratio h to D selected in this area, a strength advantage can be achieved through the resulting soil geometry.

It is also advantageous if a ratio of the radius R1 or R2 to a radius R3 of the section of the seal 3 in the receiving groove 5, 5 'in the pressed state 0.3 <R1 / R3 <3.0 or 0.3 <R2 / R3 is <3.0. A lower ratio could possibly cause a leak due to insufficient surface pressure in the transition area between the receiving groove 5, 5 ′ and the ramp 11. If the ratio is too large, there is insufficient contact pressure along the ramp 11 or a disadvantage in terms of installation space, since a wider base 2 is required. According to the Figure 6 the leakage (leakage L) is shown as a function of the mentioned radius ratio, whereby it can be clearly seen that with a radius ratio R1 / R3 or R2 / R3 between 0.3 and 3.0 the leakage, ie the leakage, is lowest. In order to be able to keep the mechanical stresses σ _{R of} the flat tube 9 as low as possible, a longitudinal end of a passage 8 facing the receiving groove 5, 5 'lies between 1mm <a <15mm, in particular between 2mm <a <6mm closer to the receiving groove 5, 5 'as a transition of the ramp 11 to the intermediate area 10. The meaning of the distance a is according to FIG Figure 7 shown, with the diagram according to Figure 8 Dependence of the pipe stress σ _R on the distance a is given. It can be clearly seen that the pipe stress σ _R can be minimized with a value a between 2 and 6mm.

According to the invention, at least one of the ramps 11 is also designed as a groove 13 which extends parallel to the longitudinal direction of the passages 8 and in which the Seal 3 runs in sections, the ratio of the degree of groove filling through the seal 3 in the groove 13 to the degree of groove filling through the seal 3 in the receiving groove 5, 5 'in the compressed state of the seal 3 should be between 1.0 and 1.4. If the ratio is in the range mentioned, the seal 3 can on the one hand be optimally guided and fixed and on the other hand an optimal sealing function can be achieved through a stronger compression in the ramp area 11 or in the transition area of the ramp 11 to the receiving groove 5, 5 'or to the intermediate area 10 will.

If you look at the Figure 9 It can be seen that the ramps 11 have a width b1 and the intermediate regions 10 have a width b2, the ratio of the width b1 to b2 being between 0.3 and 1.0. In addition, the cross section of the seal 3 in the area of the ramp 11 should be> 40% of the cross section of the seal 3 in the area of the receiving groove 5, 5 ', preferably between 50% and 70%. In this way, an optimized degree of slot filling can be achieved using simple structural means.

If you look at the Figure 10 It can be seen that the seal 3 has at least one further prestressing web 14 in addition to the actual sealing web 12, which runs parallel to the sealing web 12 and which causes a reduction in tensile stress on the seal 3. This makes it possible to ensure the desired optimal position required for tightness both along the receiving groove 5, 5 ′ and between the passages 8.

If you look at the Figure 13 It is shown therein that the cover 4 has longitudinal side projections 6 or box feet 15 on two opposite sides, with only one of the two sides being shown in the case shown and with the side projections 6 extending into the receiving grooves 5, 5 ' and have a lengthwise overhang 16 protruding beyond the respective receiving groove 5, 5 '. The supernatant 16 should over the Area where the seal 3 bends, protrude. It can also protrude beyond the receiving groove 5, 5 ', but can also terminate flush with it. Due to the position of the seal 3 between the passages 8 in the area of a narrow side, it is advantageous for the tight compression of the seal 3 if the connection between the base 2 and the cover 4 along the receiving groove 5, 5 'at least up to the point is sufficient where the seal 3 is passed between the passages 8, particularly advantageous if the box foot 15 protrudes along the receiving groove 5, 5 'beyond the seal 3, wherein it can flush the respective receiving groove 5, 5' or the protrusion described above 16 owns. Here too, the protrusion 16 should protrude beyond the area at which the seal 3 bends. This results in an H-shaped side protrusion design. Figure 13 shows such a connection between the cover 4 and the base 2, the course of the seal 3 and the position of an outer closure 17, which extends beyond the course of the seal 3 between the passages 8 through the protrusion 16 also shown on the box foot 15. In this way, in particular, an improved sealing function is possible through greater contact pressure.

It can also be provided that a projection 20 for positioning the cover 4 on the base 2 is arranged on the box base 15. Such a projection 20 is used to optimally position the cover 4 relative to the bottom 2 in the longitudinal direction and also enables the tolerances of the tolerance chain to be halved in the longitudinal direction.

The receiving groove 5, 5 'can also have a wall 18 which is at least partially bent over to connect the cover 4 to the base 2 in such a way that it engages behind part of the box foot 15 of the cover 4. The wall 18 of the receiving groove 5, 5 'can have several regions and / or battlements that repeat themselves in their geometric shape are arranged symmetrically to the passages 8 of the bottom 2 and which can be bent or bent around the box foot 15 of the cover 4 (cf. Figure 1 ). In addition, the heat exchanger 1 has a side part 19 with a side part overhang s for connecting the base 2 to the cover 4, the mean distance between the side part 19 and an adjacent, outer flat tube 9 being the value q and the ratio s / q between Should be 0.3 and 0.7 (compare Figures 11 and 12 ). According to the Figure 11 a combination with a side part overhang s is shown, the ratio s / q in this case being 0.7. With a ratio s / q = 0.3, a smaller contact surface on the side projection 6 or box foot 15 is achieved. The side part overhang s should therefore be chosen so that on the one hand the contact pressure required for the tight connection between the base 2 and the cover 4 can be achieved, but the cover 4 does not impede a flow in the outermost flat tube 9. Figure 12 shows the strength of the seal and thus also indirectly the tightness as a function of the ratio s / q.

All passages 8 of the base 2 can have the same contour and the same surface area for pipes 9 and side parts 19, which simplifies production. It is also possible that the outer passages 8, depending on the wall thickness of the side part 19, have a smaller or larger surface area than the other passages 8.

Furthermore, the shape of the transition areas, in particular between the two outer passages 8, can differ from that of the other transition areas. For example, the ramp 11 can only be embossed between the outer three passages 8. The shape of the transition areas can also differ in such a way that a repeating pattern results.

With the heat exchanger 1 according to the invention and in particular with a floor 2 according to the invention, such a floor 2 can be produced as an endless sheet and can thus be used extremely flexibly with heat exchangers 1 of different sizes. At the same time, an optimal sealing effect can be achieved.

Claims (13)

1. Heat exchanger (1) having a bottom (2), a seal (3) and a lid (4),

   - wherein the bottom (2) has two receiving grooves (5, 5') spaced parallel, extending in longitudinal direction of the bottom (2), which are arranged on two opposite sides of the bottom (2) and are designed to receive lateral protrusions (6) of the lid (4),

   - wherein each receiving groove (5, 5') has a groove base (7, 7'),

   - wherein the bottom (2) has at least three passages (8) which are arranged in one plane spaced parallel from one another as well as spaced from the receiving grooves (5, 5') and extend perpendicularly to and between the receiving grooves (5, 5'),

   - wherein in the plane between two passages (8) is formed an interim region (10) which is arranged parallel spaced from the groove bases (7, 7') of the receiving grooves (5, 5') by a height difference h,

   - wherein between each interim region (10) and the groove bases (7, 7') extends parallel to the longitudinal direction of the passages (8) in each case one ramp (11) and the ramps (11) are spaced parallel to one another,

   - wherein the seal (3) has a peripheral sealing cord,

   wherein

   - the seal (3) extends in the receiving grooves (5, 5') and with in each case one sealing web (12) across two ramps (11) and an interim region (10) situated between them,

   - each ramp (11) is rounded at the transition to the receiving groove (5, 5') with a radius R1 and at the transition to the interim region (10) with a radius R2,

   - the ramps (11) are inclined at between 20° < α < 65° with respect to the interim region (10), or have an S-shaped course, wherein a turning point W is arranged in the range from 10% to 80% of the height difference h starting from the groove-base (7, 7') of the receiving groove (5, 5),

   characterised in
   that at least one of the ramps (11) is formed as a groove (13) which extends parallel to the longitudinal direction of the passages (8) and in which the seal (3) extends in sections, wherein the ratio of the groove filling degree on the part of the seal (3) in the groove (13) of the at least one ramp (11) to the groove filling degree on the part of the seal (3) in the receiving groove (5, 5') in the compressed state of the seal (3) is between 1.0 and 1.4.
2. Heat exchanger according to claim 1,
   characterised in that
   a ratio of the height difference h to the diameter D of a portion of the seal (3) in the receiving groove (5, 5') is in an uncompressed state 0.7 < h/D < 2.5, preferably 1.0 < h/D < 2.0.
3. Heat exchanger according to claim 1 or 2,
   characterised in that
   a ratio of the radius R1 or R2 to a radius R3 of the portion of the seal (3) in the receiving groove (5, 5') in a compressed state is 0.3 < R1/R3 < 3.0 or 0.3 < R2/R3 < 3.0
4. Heat exchanger according to any of the preceding claims,
   characterised in that
   a longitudinal end, facing the receiving groove (5, 5') of a passage (8) lies between 1 mm < a < 15 mm, in particular, between 2 mm < a < 6 mm closer to the receiving groove (5, 5') than a transition of the ramp (11) to the interim region (10).
5. Heat exchanger according to any of the preceding claims,
   characterised in that
   the ramps (11) have a breadth b1 and the interim regions (10) have a breadth b2, wherein the ratio is 0.3 < b1/b2 < 1.0.
6. Heat exchanger according to any of the preceding claims,
   characterised in that
   the seal (3) has at least one prestressing web (14) for reducing tensile stresses on the seal (3), wherein the at least one prestressing web (4) is arranged parallel to a sealing web (12).
7. Heat exchanger according to any of the preceding claims,
   characterised in that
   the lid (4) is in the form of a box which has lateral protrusions (6) extending on the longitudinal sides on the outer region of the box on two sides opposite one another, wherein the lateral protrusions (6) extend into the receiving grooves (5, 5') and have an overhang (16) extending longitudinally over the seal (3).
8. Heat exchanger according to any of the preceding claims,
   characterised in that
   the lid (4) is formed as a box which has a box foot (15), wherein on a longitudinal side on the outer region of the box foot (15) is arranged a protrusion (20) for positioning the box on the bottom (2).
9. Heat exchanger according to any of the preceding claims,
   characterised in that
   the receiving groove (5, 5') has a wall (18) which is bent such that it grips below at least a part of the lateral protrusion (6) of the lid (4).
10. Heat exchanger according to claim 9,
    characterised in that
    the wall (18) of the receiving groove (5, 5') has several regions and/or crenellations which repeat in their geometric shape, which are arranged symmetrically to the passages (8) of the bottom (2) and is can be bent or are bent around the lateral protrusion (6) of the lid (4).
11. Heat exchanger according to any of the preceding claims,
    characterised in that
    the heat exchanger (1) has a lateral part (19) which is inserted through a passage of the bottom, with a lateral part overhang s for connecting the bottom (2) with the lid (4), wherein the average distance between the lateral part (19) and an adjacent outer flat pipe (9) has the value q and wherein the ratio is 0.3 < s/q < 0.7.
12. Heat exchanger according to any of the preceding claims,
    characterised in that
    all passages (8) have the same contour and the same surface area.
13. Heat exchanger according to any of claims 1 to 11,
    characterised in that
    at least the two outer passages (8) arranged at the lateral ends of the bottom have a surface area which differs from the otherwise equal surface area of the remaining passages (8) by the factor 0.8 to 1.3.

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