EP1682842B1 - Flow channel for a heat exchanger, and heat exchanger comprising such flow channels - Google Patents

Description

The invention relates to a flow channel for a heat exchanger which can be flowed through by a medium in a flow direction. Furthermore, the invention relates to a heat exchanger with flow channels according to the preamble of claim 32.

Flow channels for heat exchangers are from a first medium, eg. B. flows through an exhaust gas or a liquid coolant and define this first medium against a second medium to which the heat of the first medium is to be transmitted, from. Such flow channels may be tubes with a round cross-section, rectangular tubes, flat tubes or pairs of discs, in which two plates or discs are connected at the edge. Most often, the media that are in heat exchange with each other, different, z. B. flows in the pipes a hot, laden with soot particles exhaust gas, and on the outside of the exhaust pipes are flowed around by a liquid coolant, which has different heat transfer conditions on the inside and outside of the tubes result. It has therefore, in particular for exhaust pipes proposed on the inside V-shaped and diffuser-like arranged turbulence generator to arrange, which provide a turbulence of the flow and an improvement of the heat transfer on the exhaust side while preventing soot deposition. Such solutions for exhaust gas heat exchanger are apparent from the following documents of the applicant: EP-A 677 715 . DE-A 195 40 683 . DE-A 196 54 367 and DE-A 196 54 368 , These known exhaust gas heat exchanger have rectangular tubes made of stainless steel, which are composed of two half-shells welded together, in which the turbulence generator, so-called winglets are molded or embossed and arranged one behind the other. The winglet pairs of the two half shells are either in the longitudinal direction of the tubes, ie offset in the flow direction against each other ( DE 196 54 367 . DE 196 54 368 ) or facing each other ( DE 195 40 683 ) arranged.

In the DE-A 101 27 084 The applicant has proposed a heat exchanger, in particular a coolant / air cooler with flat tubes and corrugated fins, in which the flat sides of the flat tubes have a structure consisting of structural elements. The structural elements are elongated, V-shaped arranged in rows transverse to the coolant flow direction and transverse to the longitudinal axis of the tubes and act as a vortex generator to increase the heat transfer on the coolant side. The vortex generators are embossed in both opposite pipe walls and protrude inwards into the coolant flow. The rows of vortex generators on one flat tube side are offset in the flow direction from the rows on the other flat tube side. Thus, it is also possible to measure the inwardly projecting height of the vortex generator greater than half the clear width of the flat tube cross-section.

By the EP-A 1 061 319 has been known a flat tube for a motor vehicle radiator, which has on its flat sides a structure consisting of individual elongated, arranged in rows structural elements. Here are in the flow direction rows with differently oriented Structural elements arranged so that the flow is deflected in the interior of the flat tube approximately zig-zag-shaped. In particular, however, the rows are arranged with structural elements on a flat tube side in the flow direction offset from the rows of the opposite flat tube side. A row of structural elements thus faces a smooth area of the flat tube inner wall. The flow within the coolant tube is thus alternately influenced by the structural elements of one and the other flat tube side, but not simultaneously. This is to be avoided, inter alia, a blockage of the pipes. With regard to the heat transfer capability, there are still potentials here.

It is an object of the present invention to improve a flow channel and a heat exchanger of the type mentioned in terms of its heat transfer capacity, in particular to increase turbulence and vortex formation, the pressure loss should increase to an even more reasonable level.

This object is solved by the features of patent claim 1. According to the invention, it is provided that the structural elements arranged in particular in rows lie substantially opposite one another and the other side of the flow channel, that is, in the direction of flow, are each arranged approximately at the same height. The opposing structural elements or rows can also be offset from each other in the flow direction, but only to the extent that there is still an overlap. At the same time, structural elements projecting from the one and the other heat exchanger surface and projecting into the flow channel enter the flow and cause a turbulence of the flow, which results in an improvement of the heat transfer on the inside of the flow channel. In addition, for example, in the case of an exhaust gas flow - possibly a soot deposition prevented. The pressure loss keeps within reasonable limits. The flow within the flow channel is thus disturbed simultaneously on both sides, ie both boundary layers are detached at the same time, which leads to a particularly strong turbulence. The opposing structural elements or rows of structural elements can also be on the outside of the flow channel - in the case of an exhaust gas cooler on the coolant side - are. Advantageous embodiments of the invention will become apparent from the dependent claims.

A row of structural elements is formed in the context of the present invention of one or more structural elements, which are arranged in the flow direction P substantially side by side.

Advantageous embodiments of the invention provide various embodiments of the structural elements, which may be rectilinear or curved, ie with a constant or variable outflow angle to the flow direction. By changing the outflow angle from a relatively large angle of attack to the outflow angle, there is a "gentle" deflection of the flow and thus a somewhat reduced pressure loss. According to a further advantageous embodiment of the invention, the structural elements can be arranged offset within a row, that is, the structural elements are indeed arranged in a direction transverse to the flow direction series, but arranged staggered in the flow direction. This also gives the advantage of a lower pressure loss. In addition, opposite rows, so one or the other flat tube side, be offset in the flow direction against each other, but always an overlap between the two rows is maintained. Also by this displacement in the flow direction results in a lower pressure loss. If the opposing structures touch and are joined by welding or soldering, the strength can be increased.

Between or next to the structural elements or between or within the "structural rows" (rows with structural elements) (as viewed in the direction of flow P) also knobs and / or webs can be pronounced outwardly or inwardly to achieve a "support" and thus an increase in strength. The vortex generating structures can also take over this function in whole or in part.

According to an advantageous embodiment, the substantially opposing heat transfer surfaces and in particular the structural elements arranged thereon are curved. In particular, in tubes with a circular or oval cross section, the advantages of the invention are achieved.

According to an advantageous embodiment, the substantially opposing heat transfer surfaces heat engineering primary surfaces. According to a variant, however, the heat transfer surfaces are heat-technical secondary surfaces, which are formed in particular by preferably welded to the flow channel, welded or jammed ribs, webs or the like.

According to an advantageous embodiment, the height h of the structural elements is in the range of 2 mm to 10 mm, in particular in the range of 3 mm to 4 mm, preferably by 3.7 mm.

According to an advantageous embodiment, the flow channel is Rechtekkig and has a width b, which is in particular in the range of 5 mm to 120 mm, preferably in the range of 10 mm to 50 mm.

According to an advantageous embodiment, a hydraulic diameter of the flow channel is in the range of 3 mm to 26 mm, in particular in the range of 3 mm to 10 mm.

The object of the invention is also solved by the features of claim 32. According to the invention, the aforementioned flow channels are provided as flat, round, oval or rectangular tubes of a heat exchanger, advantageously a Abgaswärmeübertragers. The arrangement of the structural elements according to the invention, ie advantageously their impression in the pipe inner walls brings an increase in performance of the heat exchanger with it. Particularly advantageous are the arranged in rows structural elements for exhaust gas heat exchanger, because in this case a soot deposition is avoided in the interior of the flat tubes. The exhaust pipes are surrounded on their outside by a coolant, which is taken from the coolant circuit of the exhaust gases ejecting the engine. It is also possible that the structures are also stamped in plates or slices to produce heat exchangers from them.

Fig. 1

einen Strömungskanal gemäß Stand der Technik,

Fig. 2a, b, c

einen Querschnitt von Strömungskanälen,

Fig. 3

ein Flachrohr mit erfindungsgemäßer Struktur,

Fig. 4

eine Halbschale des Flachrohres gemäß Fig. 3,

Fig. 5a, b, c, d

verschiedene Strukturelemente,

Fig. 6a, c, h

erfindungsgemäße Strömungskanäle,

Fig. 6b, d, e, f, g

nicht erfindungsgemäße Strömungskanäle,

Fig. 7a, b

weitere Strukturen,

Fig. 8

eine weitere Struktur,

Fig. 9a, b, c, d

gespiegelte Strukturelemente,

Fig. 10a, b, c, d

parallel verschobene Strukturelemente,

Fig. 11 a, b, c, d

Reihen von Strukturelementen mit Abwandlungen und

Fig. 12a, b

weitere Strukturelemente.

Embodiments of the invention are illustrated in the drawings and will be described in more detail below. Show it

Fig. 1

a flow channel according to the prior art,

Fig. 2a, b, c

a cross section of flow channels,

Fig. 3

a flat tube with inventive structure,

Fig. 4

a half-shell of the flat tube according to Fig. 3 .

Fig. 5a, b, c, d

different structural elements,

Fig. 6a, c, h

flow channels according to the invention,

Fig. 6b, d, e, f, g

non-inventive flow channels,

Fig. 7a, b

further structures,

Fig. 8

another structure,

Fig. 9a, b, c, d

mirrored structural elements,

Fig. 10a, b, c, d

parallel shifted structural elements,

Fig. 11 a, b, c, d

Rows of structural elements with variations and

Fig. 12a, b

further structural elements.

Fig. 1 shows a simplified representation of a flow channel 1, which is designed as a rectangular tube, a rectangular inlet cross section 2, two opposite flat sides F1, F2 and two opposite narrow sides S1, S2 has. The channel 1 is from a flow medium, for. B. flows through an exhaust gas in the direction of the arrow P. On the lower flat side F2 arranged V-shaped vortex generators 3a, 3b, 4a, 4b, which cause by generating vortices an increased turbulence of the flow and at the same time - with an exhaust gas flow - prevent soot deposition. This representation corresponds to the aforementioned prior art. Thereafter, the paired V-shaped exhibited, in the flow direction diffuser-like expanding vortex generators 3a, 3b and 4a, 4b are also referred to as winglets.

Fig. 2a shows the cross section of a formed as a flat tube flow channel 1, in which both on the upper flat side F1 and on the flat side F2 winglet pairs 5a, 5b and 6a, 6b are arranged. The channel cross-section has a channel height H and a channel width b. The winglets 5a, 5b, 6a, 6b have a height h projecting into the channel cross-section. This arrangement of winglets corresponds to the aforementioned prior art. The designations F1, F2 also apply to the following inventive embodiments.

Fig. 2b shows the cross section of a round tube designed as flow channel 1 ', in which both on the upper flat side F1 and on the lower flat side F2 structural elements 13' and 13 are arranged. The channel cross section has a channel height H.

Fig. 2c shows the cross section of a formed as a flat tube flow channel 1, in which the heat transfer surfaces F1, F2 thermally represent secondary surfaces, as they do not directly transfer heat from one to the other medium. The heat transfer surfaces have structural elements 13, 13 '.

Fig. 3 shows a flow channel according to the invention, which is designed as a flat tube 7, which is partially shown in a plan view. The flat tube 7 has a longitudinal axis 7a, a width b and two rows 8, 9 of V-shaped arranged structural elements or winglets 10, 11, which are embossed both in the top F1 and in the bottom F2 of the flat tube 7, and with the same pattern, so that the top winglet row covers the underlying row. There are eight winglets in a row, evenly distributed over the entire width b, but six or seven winglets may be the same width. For narrow tubes, discs or plates, the number of winglets may also be below six, at wider tubes or discs / plates even above eight. The two rows 8, 9 have a distance s to each other, which is measured from center to center and is about 2 times to 6 times the length of the winglets. Between the individual rows, therefore, there is a smooth area in each case, into which, for example, support structures are embossed. The rows of winglets extend over the entire length of the flat tube 7, in each case with the distance s, on both sides of the flat tube 7.

Fig. 4 shows a bottom half shell 7b of the flat tube 7 in a view in the direction of the longitudinal axis 7a of the flat tube 7. The half shell 7b, has a bottom F2 and two lateral legs 7c, 7d, wherein on the bottom or the bottom F2 winglets 11 'arranged , ie are imprinted in the pipe wall. The upper half shell is not shown; it is mirror-inverted and is longitudinally welded to the lower half-shell 7b on the lateral legs 7c, 7d. The winglets 11 'have a height h, with which they protrude into the clear cross-sectional area of the flat tube 7. The tube can also be made from a sheet that is formed and welded on one side.

In a preferred embodiment, the width b of the flat tube is 40 mm or 20 mm, the overall height of the flat tube about 4.5 mm and the height h of the winglets about 1.3 mm. With a clear channel height of 4.0 mm, a clear cross-sectional height of 1.4 mm for a core flow remains as a result of the winglets projecting from both sides into the channel cross-section, each with a height of 1.3 mm. The distance s of the rows is about 20 mm.

The flat tube 7 is preferably used for per se known exhaust gas heat exchanger (not shown), ie it is traversed on the inside of exhaust gas of an internal combustion engine of a motor vehicle and on its outside by coolant of a coolant circuit of the internal combustion engine cooled. In this case, the outside of the flat tubes 7 - as known from the prior art - be smooth and be kept for example by embossed knobs at a distance with adjacent tubes. However, it is also possible to provide on the outside of the flat tubes 7 fins to improve the heat transfer on the coolant side.

The Figures 5a, 5b, 5c and 5d show individual structural elements which are provided for a structure according to the invention on the flow channels.

Fig. 5a shows an elongated structural element 13 with a longitudinal axis 13a, which forms with a reference line q an angle α, the outflow angle. The flow direction for all representations 5a to 5d is the same in each case and represented by an arrow P. The reference line q is perpendicular to the flow direction P. The structural element 13 has a length L and a width B. The latter can be constant or variable, ie increasing in the direction P.

Fig. 5b shows an elongated, but angled structural element 14 with two mutually inclined longitudinal axes 14a, 14b, which enclose with the reference line q each have an angle α and β. β is referred to here as the angle of attack and α as the outflow angle. The flow according to the arrow P is thus deflected in two stages, ie initially only slightly and then stronger. This results in a lower pressure drop - compared to a structural element according to Fig. 5a at the same outlet angle α. The length of the structural element 14 along the longitudinal axes 14a, 14b is denoted by L.

Fig. 5c shows an arcuate structural element 15 with a curved longitudinal axis 15a, which corresponds to a circular arc with the radius R. The upstream angle is referred to as the angle of attack β and the downstream located angle is referred to as the outflow angle α. Again, there is a gentle deflection of the flow around the angle (90 ° - β) and then a stronger deflection around the angle (90 ° - α). As a result of this continuously increasing deflection of the flow, a lower pressure loss is likewise achieved-in comparison to the structural element 13 according to FIG Fig. 5a , The length of the structural element 15 along the longitudinal axis 15a is denoted by L.

Fig. 5d shows a further embodiment of a structural element 16, which is approximately Z-shaped and also has a Z-shaped extending longitudinal axis 16a. The longitudinal axis 16a connects two circular arc pieces of different curvature, but with the same radius R1 = R2. The angle of attack is here denoted by β, the outflow angle by α, it corresponds to a flow deflection of (90 ° - α), which takes place in the central region of the structural element 16. The inflow and outflow of this structural element takes place practically in the flow direction P. This is a particularly low-pressure deflection of the flow given. The length of the structural element along the longitudinal axis 16a is denoted by L.

The Fig. 6a, 6b . 6c, 6d . 6e, 6f . 6g . 6h show arrangement patterns of the structural elements 13 according to FIG Fig. 5a , in rows on a section of a flow channel.

Fig. 6a shows the elongated structural elements 13 in a flow channel according to the invention, each arranged in two rows 17, 18, which have a distance s in the flow direction P. The structural elements 13 shown in solid lines are impressed in the upper side F1 of the flow channel. In the lower heat exchanger surface or side F2 of the flow channel broken structure elements 13 ', also in rows 19, 20 are arranged. The rows are shown by dashed lines. The structural elements 13 'on the lower surface F2 are opposite to the structural elements 13 on the upper surface F1 aligned opposite, ie they have an opposite outflow angle α (see. Fig. 5a ) on. In addition, the rows 19, 20 offset from the rows 17, 18 in the flow direction P, by the amount f. The structural elements 13 and 13 'and the associated rows 17, 18 19, 20 each have a depth T, ie a Erstrekkung in the flow direction P. The offset f is smaller than the depth T, so that between the rows 18, 20 and 17, 19 an overlap Ü remains, which results from the difference of T and f. An overlap Ü of 100% for rows of equal depth T means that the offset is zero (f = 0). In the case of rows with different depths T1 or T2, for example T1 <T2, an overlap of 100% means that the overlap Ü is equal to the smaller depth T1 (U = T1). By an offset of each opposing rows 17, 19 and 18, 20 results in a lower pressure loss advantageous than rows without offset.

Fig. 6b Figure 12 shows another pattern of in-line structural elements 13 in a row 21 and a row 22 with different outflow angles α (not shown) in a non-inventive flow channel. The structural elements 13 in solid lines are embossed in the upper side F1 of the flow channel. On the lower surface F2 of the flow channel are in the flow direction P, dashed at the same height illustrated structural elements 13 'arranged with opposite orientation, so that an upper structural element 13 and an opposite lower structural element 13' in the plan view in each case appear as a cross. The upper row with structural elements 13 is thus not offset from the lower row with structural elements 13 '; the overlap Ü is 100%.

Fig. 6c to Fig. 6h show further arrangement patterns of the structural elements 13, 13 'on the upper (shown in solid lines) and the lower (shown broken) side F1, F2 of the flow channel, in a flow channel according to the invention ( Fig. 6c . 6h ) or in a non-inventive flow channel ( Fig. 6d . 6e . 6f . 6g ).

Fig. 6h also shows on the outside of the flow channels support elements 13 ", which are arranged in this embodiment adjacent to the structural elements 13, 13 'and in particular within the rows formed by the structural elements 13, 13' Preferably, the support elements are embossed into the wall of the flow channel For a desired support of the respective flow channel, the support elements 13 "advantageously have a height that corresponds to the desired distance between two flow channels or between the respective flow channel and a housing wall of a heat exchanger.

The FIGS. 7a and 7b show further variants of the arrangement of the structural elements 13 in rows, in a non-inventive flow channel.

Fig. 7a shows a section of a flow channel with two rows 23, 24 of V-shaped arranged structural elements 13 on the upper side F1. The structural elements 13 are not arranged at constant intervals next to each other, but instead have gaps 25, 26, 27, but are filled on the underside F 2 by structural elements 13 ', so that in the plan view a continuous uniform arrangement of structural elements 13 and 13 'results. This arrangement of "discontinuous" rows 23, 24 and the corresponding rows on the bottom results in a lower pressure drop for the flow in the direction P, because the structural elements - seen in the width direction - only alternately engage from above and below in the flow.

Fig. 7b shows a similar patchy arrangement of parallel aligned structural elements 13 on the top F1 in rows 28, 29. The gaps between the structural elements 13 are in turn filled by structural elements 13 'on the bottom F2, wherein the structural elements 13 on the top F1 and the structural elements 13 'on the bottom F2 to a zigzag-shaped arrangement in the plan view. This arrangement is relatively low pressure loss.

Fig. 8 shows a further embodiment for the arrangement of structural elements 13 and 13 'in two rows 30, 31 on the upper side F1, in a non-inventive flow channel. The structural elements 13 of the row 30 and the structural elements 13 'of the opposite row (on the bottom F2) are arranged parallel and equidistant from one another. The same applies analogously to the second row 31, wherein only the outflow angle is opposite, so that, as seen in the direction of flow P, a deflection of the flow results.

In the FIGS. 6a, 6b . 7a, 7b and 8th In each case, structures with the structural elements 13 were obtained according to FIG Fig. 5a shown. The structural elements 13 can also be replaced by structural elements 14 (in FIG Fig. 5b ), 15 ( Fig. 5c ) or 16 ( Fig. 5d ) be replaced. It would also be possible in a number of different structural elements, eg. B. 13 and 14 to use.

Fig. 9a, 9b, 9c, 9d show variants of the structural elements 13, 14, 15, 16 by mirroring, in an inventive flow channel: This results in so-called winglet pairs 32, 33, 34, 35, wherein in each case a minimum distance a is provided between two structural elements. The flow direction is usually in the direction of the arrow P, wherein the flow of the winglet pairs conventionally takes place at the narrowest point a. This results in decreasing pressure losses for the different winglet pairs 32 to 35 in this order. These winglet pairs can be arranged side by side in rows, e.g. B. as in the FIGS. 6 to 8 ,

10a, 10b, 10c, 10d show further variations of the structural elements 13, 14, 15, 16 by parallel displacement, in a non-inventive flow channel. This results in double elements 36, 37, 38, 39, each with equal distances a on the arrival and downstream side, the z. B. in the structures according to Fig. 6 to 8 can be integrated.

It is important that the structural elements of a series above and / or below not necessarily have the same geometric shape or dimensions, as exemplified by four structural elements in Fig. 11a will be shown. Rather, as in Fig. 11b shown, the structural elements are arranged with an offset f in the flow direction P.

In Fig. 11c vary the outflow angle of the structural elements 13, and in Fig. 11d vary the lengths L1, L2 of the structural elements 13. A combination (not shown) of the variants according to Fig. 11b, 11 c, 11 d is also possible. These variations can also occur in the upper and / or lower surface F1 or F2.

Fig. 12a shows another structural element 43, which is formed as an angle with two straight legs 43a, 43b, which are connected at their apex by an arc 43c. In this respect, this structural element 43 constitutes a modification of the winglet pair 32 Fig. 9a The flow is preferably in the direction of vertex 43c, according to the arrow P.

Fig. 12b shows a further modification of the structural element pair 34 according to Fig. 9c namely, a structural member 44 having two arcuate legs 44a, 44b joined at apex by a bend 44c. The structural element 44, which is likewise flown in the direction of the apex 44c in accordance with the arrow P, initially causes a small flow deflection, which then amplifies due to the legs 44a, 44b curved into the flow.

The elements according to Fig. 12a and Fig. 12b can be used in all previously shown arrangements where two structures arranged in V-shape can be found again.

Claims (40)

1. A flow passage (1), through which a medium can flow in a direction of flow P, of a heat exchanger having two heat exchanger surfaces (F1, F2), which lie substantially opposite one another, are in particular arranged parallel and/or at a spacing of a passage height H and each have a structure formed from a multiplicity of structure elements that are arranged next to one another in rows transversely with respect to the direction of flow P and project into the flow passage, the structure elements each having a width B, a length L, a height h, a flow off angle α and a longitudinal axis, at least two rows (17, 18, 19, 20) comprising structure elements (13, 13') on substantially opposite heat exchanger surfaces (F1, F2) having an overlap (Ü) with one another, a row (17, 18, 19, 20) having in each case the same structural elements (13, 13'), and individual structural elements (13, 14, 15, 16) being arranged next to one another in pairs (32, 33, 34, 35) at a distance a and in mirror-image fashion with respect to one another, characterized in that in each case a structure element of a heat exchanger surface overlaps with a structure element of the opposite heat exchanger surface, and that all structure elements (13, 13') of rows (17, 18, 19, 20, 21, 22) lying opposite one another are oppositely oriented, in particular have an opposite flow-off angle α.
2. The flow passage as claimed in claim 1, characterized in that the overlap (Ü) is 100%.
3. The flow passage as claimed in claim 1, characterized in that the structure elements (13) are elongate, in particular rectangular in form and have a straight longitudinal axis (13a).
4. The flow passage as claimed in claim 1, characterized in that the structure elements (14) are elongate and angled in form and have an angled longitudinal axis (14a, 14b) which forms the flow off angle α and a flow on angle β with the direction of flow P.
5. The flow passage as claimed in claim 1, characterized in that the structure elements (15) are arcuate in form and have a longitudinal axis (15a) which is curved with a radius R and forms the flow off angle α and a flow on angle β with the direction of flow P.
6. The flow passage as claimed in claim 1, characterized in that the structure elements (16) are approximately Z shaped in form and have a doubly curved longitudinal axis (16a) with radii (R1, R2) which forms the flow off angle α and a flow on angle β with the direction of flow P.
7. The flow passage as claimed in claim 1, characterized in that the structure elements (43) are V shaped in form and have straight V limbs (43a, 43b).
8. The flow passage as claimed in claim 1, characterized in that the structure elements (44) are V shaped in form and have V limbs (44a, 44b) which are curved away from the direction of flow.
9. The flow passage as claimed in one of claims 1 to 8, characterized in that the height h of the structure elements (13, 14, 15, 16) is 20% to 50% of the passage height H.
10. The flow passage as claimed in claim 9, characterized in that the length L of the structure elements (13, 14, 15, 16) is from two to twelve times the height h of the structure elements.
11. The flow passage as claimed in one of claims 1 to 10, characterized in that the distance s between the rows amounts to 0.5 to eight times the depth T.
12. The flow passage as claimed in one of claims 1 to 11, characterized in that the distance s between in each case two rows varies in the direction of flow P.
13. The flow passage as claimed in one of claims 1 to 10, characterized in that the structure elements (13, 14, 15, 16) have a constant width B in the range from 0.1 to 60 mm, preferably in the range from 0.1 to 3.0 mm.
14. The flow passage as claimed in one of claims 1 to 10, characterized in that the structure elements (13, 14, 15, 16) have a width which increases in the direction of flow between a starting width B1 and a finishing width B2, the starting width B1 being in the range from 0.1 to 4 mm and the finishing width B2 being in the range from 0.1 to 6 mm.
15. The flow passage as claimed in one of the preceding claims, characterized in that the flow off angle α is in the range from 20 to 70°, preferably in the range from 40 to 65°, and in particular has a value of from 50 to 60°.
16. The flow passage as claimed in one of claims 4 to 6 and 15, characterized in that the flow on angle β is in each case larger than the flow off angle α.
17. The flow passage as claimed in claim 6, characterized in that the radius R is in the range from 1 to 10 mm, preferably in the range from 1 to 5 mm.
18. The flow passage as claimed in claims 5 and 17, characterized in that the radii R1 and R2 are equal to the radius R.
19. The flow passage as claimed in one of claims 1 to 18, characterized in that some or all the structure elements (13, 14, 15, 16) are parallel but offset with respect to one another and are arranged in pairs (36, 37, 38, 39) at a distance a transversely with respect to the direction of flow.
20. The flow passage as claimed in one of claims 1 to 19, characterized in that a distance a between two structure elements may vary within at least one row.
21. The flow passage as claimed in one of claims 1 to 19, characterized in that the distance a is in the range from 0 to 8 mm.
22. The flow passage as claimed in one of claims 1 to 21, characterized in that individual structure elements (13) of a row (40) are offset by an amount f with respect to one another in the direction of flow P, the amount f being less than the depth T of the structure elements (13), and T being the projection of the length L transversely with respect to the direction of flow P.
23. The flow passage as claimed in of claims 19 or 22, characterized in that individual structure elements (13) of a row (41) are not arranged parallel and have a differing flow off angle α.
24. The flow passage as claimed in one of the preceding claims, characterized in that the structure elements of opposite rows touch one another, in particular are joined to one another by welding or soldering.
25. The flow passage as claimed in one of the preceding claims, characterized in that opposite rows of structure elements have the same depth T in the direction of flow P.
26. The flow passage as claimed in one of the preceding claims, characterized in that opposite rows of structure elements have different depths T1, T2 in the direction of flow P.
27. The flow passage as claimed in one of the preceding claims, characterized in that the heat exchange surfaces which lie substantially opposite one another, and in particular the structure elements arranged thereon, are curved.
28. The flow passage as claimed in one of the preceding claims, characterized in that the heat exchange surfaces which lie substantially opposite one another are heat-engineering primary surfaces or secondary surfaces, the secondary surfaces being formed in particular by fins, webs or the like which are preferably clamped, welded or soldered to the flow passage.
29. The flow passage as claimed in one of the preceding claims, characterized in that the height h is in the range from 2 mm to 10 mm, in particular in the range from 3 mm to 4 mm, and is preferably around 3.7 mm.
30. The flow passage as claimed in one of the preceding claims, characterized in that the flow passage is rectangular and has a width b which is in particular in the range from 5 mm to 120 mm, preferably in the range from 10 mm to 50 mm.
31. The flow passage as claimed in one of the preceding claims, characterized in that a hydraulic diameter of the flow passage is in the range from 3 mm to 26 mm, in particular in the range from 3 mm to 10 mm.
32. A heat exchanger, in particular an exhaust-gas cooler, in particular for a motor vehicle, having flow passages for a fluid, characterized in that at least one flow passage is designed as described in one of the preceding claims.
33. The heat exchanger as claimed in claim 32, characterized in that the flow passages (1) are formed as soldered or welded flat or rectangular tubes (7) and the heat exchanger surfaces (F1, F2) are formed as flat tube walls.
34. The heat exchanger as claimed in one of the preceding claims, characterized in that the flow passages are formed by stacking plates or disks which have structure elements on top of one another.
35. The heat exchanger as claimed in one of the preceding claims, characterized in that the structure elements (10, 11) are formed into the tube walls (F1, F2), in particular by stamping.
36. The heat exchanger as claimed in one of the preceding claims, characterized in that exhaust gas can flow through the tubes (7) and a liquid coolant can flow around the tubes (7).
37. The heat exchanger as claimed in one of the preceding claims, characterized in that the rows (8, 9) of structure elements (10, 11) are at a distance s from one another in the direction of flow (7a) which amounts to two to six times the length L of a structure element.
38. The heat exchanger as claimed in one of the preceding claims, characterized in that between the rows with structure elements there are further rows with structure elements which project outwards.
39. The heat exchanger as claimed in claim 38, characterized in that the outwardly projecting structure elements are supporting studs, webs or elements and touch one another or are welded or soldered to one another.
40. The heat exchanger as claimed in claim 38 or 39, characterized in that the outwardly projecting structure elements contribute to improving the heat transfer.

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