Flow channel for a heat exchanger, and heat exchanger comprising such flow channels
The invention relates to a flow channel of a heat exchanger with two parallel heat transfer areas that are arranged at a distance corresponding to a channel height 11. Each heat transfer area (F1, F2) is provided with a structure that is formed by a plurality of structural elements which are placed next to each other in rows running perpendicular to the direction of flow P and extend into the flow channel. Each structural element has awidth B, a length L, a height h, a flow-off angle a, and an overlap U while being provided with a longitudinal axis.
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The invention relates to a flow passage, through which a medium can flow in a direction of flow, of a heat exchanger in accordance with the preamble of patent claim 1. The invention also relates to a heat exchanger having flow passages in accordance with the preamble of patent claim 40.
A first medium, for example an exhaust gas or a liquid coolant, flows through flow passages for heat exchangers, and these flow passages delimit this first medium from a second medium, to which the heat of the first medium is to be transferred. Flow passages of this type may be tubes with a round cross section, rectangular tubes, flat tubes or also pairs of disks, in which case two plates or disks are connected at the edge sides. The media which exchange heat with one another are generally different; by way of example, a hot exhaust gas laden with particulates flows within the tubes, and a liquid coolant flows around the exhaust-gas tubes on the outer side, leading to different heat transfer conditions on the inner and outer sides of the tubes. It has therefore been proposed, in particular for exhaust-gas tubes, that turbulence generators arranged in a V-shape and in diffuser fashion be arranged on their inner side, these turbulence generators being responsible for swirling up the flow and improving the heat transfer on the exhaust-gas side while at the same time preventing deposition of particulates. Solutions of this type for exhaust-gas heat exchangers are known from the following documents in the name 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 exchangers have rectangular tubes made from stainless steel which are assembled from two half-shells welded together, into which the turbulence generators, known as winglets, are formed or stamped, arranged one behind the other. The winglet pairs of the two half-shells are offset with respect to one another either in the longitudinal direction of the tubes, i.e. in the direction of flow (DE 196 54 367, DE 196 54 368) or are arranged opposite one another (DE 195 40 683).
DE-A 101 27 084 in the name of 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 comprising structure elements. The structure elements are elongate in form, are arranged in a V shape in rows transversely with respect to the direction of flow of the coolant and/or transversely with respect to the longitudinal axis of the tubes and function as swirl generators in order to increase the heat transfer on the coolant side. The swirl generators are stamped into the two opposite tube walls and project inwardly into the coolant flow. The rows of swirl generators on a flat tube side are offset in the direction of flow with respect to the rows on the other flat tube side. It is therefore also possible for the inwardly projecting height of the swirl generators to be greater than half the clear width of the cross section of the flat tube.
EP-A 1 061 319 has disclosed a flat tube for a motor vehicle radiator which on its flat sides has a structure comprising individual elongate structure elements arranged in rows. Rows with differently oriented structure elements are arranged in the direction of flow, so that the flow in the interior of the flat tube is diverted approximately in a zigzag shape. In particular, however, the rows comprising structure elements on one flat tube side are arranged offset in the direction of flow with respect to the rows on the opposite flat tube side. Therefore, a smooth region of the flat tube inner wall in each case lies opposite a row of structure elements. The flow within the coolant tube is therefore alternately but not simultaneously influenced by the structure elements on one flat tube side and the other flat tube side. This is intended, inter alia, to prevent the tubes from becoming blocked. There is also potential in this respect with regard to the heat transfer capacity.
It is an object of the present invention to improve a flow passage and a heat exchanger of the type described in the introduction with regard to its heat transfer capacity, in particular to increase the formation of turbulence and swirl, while the pressure loss should only rise by an acceptable degree.
This object is achieved by the features of patent claim 1. According to the invention, it is provided that the structure elements arranged in particular in rows on one side and the other side of the flow passage are positioned substantially opposite one another, i.e. are in each case arranged at approximately the same level as seen in the direction of flow. The structure elements or rows lying opposite one another may also be offset with respect to one another in the direction of flow, although only to such an extent that an overlap still exists. Therefore, structure elements projecting into the flow passage from one heat exchanger surface and the other heat exchanger surface intervene simultaneously in the flow and swirl up the flow, which leads to an improvement in the heat transfer on the inner side of the flow passage. Furthermore—for example in the case of an exhaust-gas flow—under certain circumstances deposition of particulates is prevented. The pressure loss is kept within acceptable limits. The flow within the flow passage is therefore disturbed from both sides simultaneously, i.e. both boundary layers are detached simultaneously, which leads to particularly extensive swirling. The structure elements or rows of structure elements lying opposite one another may likewise be located on the outer side of the flow passage—in the case of an exhaust-gas cooler on the coolant side. Advantageous configurations of the invention will emerge from the subclaims.
In the context of the present invention, a row comprising structure elements is formed by one or more structure elements which are arranged substantially next to one another in the direction of flow P. In particular, therefore, a row may also be formed by a single structure element with, for example, no further structure elements arranged next to it.
Advantageous configurations of the invention provide for different embodiments of the structure elements, which may be rectilinear or curved in form, i.e. may have a constant or variable flow-off angle with respect to the direction of flow. Changing the flow-off angle from a relatively large flow-on angle to the flow-off angle results in a “gentle” diversion of the flow and therefore a somewhat reduced pressure loss. According to a further advantageous configuration of the invention, the structure elements within a row may be arranged offset, i.e. the structure elements, although arranged in a row running transversely with respect to the direction of flow, are arranged staggered in the direction of flow. This likewise has the advantage of a lower pressure loss. Furthermore, opposite rows, i.e. on one flat tube side or the other, may be arranged offset with respect to one another in the direction of flow, in which case, however, an overlap is always retained between the two rows. This offset in the direction of flow also results in a lower pressure loss. If the structures lying opposite one another touch one another and if they are joined to one another by welding or soldering, it is possible to increase the strength. According to another variant, the structure I elements are not arranged at equal distances within a row, but rather these rows have voids, which in each case have structure elements lying opposite them on the opposite side, thereby “filling up” these voids, as seen in plan view. This likewise has the advantage of a lower pressure loss.
It is also possible for studs and/or webs to be stamped inward or outward (as seen in the direction of flow P) between or next to the structure elements and/or between or within the “structure rows” (rows comprising structure elements), in order thereby to achieve a “supporting” action and therefore an increase in strength. The swirl-generating structures may likewise be completely or partially responsible for this function.
According to an advantageous embodiment, the heat exchange surfaces which lie substantially opposite one another, and in particular the structure elements arranged thereon, are curved. The advantages according to the invention are achieved in particular with tubes having a circular or oval cross section.
According to an advantageous embodiment, the heat exchange surfaces which lie substantially opposite one another are heat-engineering primary surfaces. According to a variant, the heat exchange surfaces, by contrast, are heat-engineering secondary surfaces, which are formed in particular by fins, webs or the like which are preferably clamped, welded or soldered to the flow passage.
According to an advantageous embodiment, the height h of the structure elements 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.
According to an advantageous embodiment, 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.
According to an advantageous embodiment, 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.
According to an advantageous embodiment, at least one, in particular each row of structure elements, comprises in each case a plurality of structure elements.
The object of the invention is also achieved by the features of patent claim 40. According to the invention, the abovementioned flow passages are provided as flat, round, oval or rectangular tubes of a heat exchanger, advantageously an exhaust-gas heat exchanger. The arrangement of the structure elements according to the invention, i.e. the way they are advantageously stamped into the tube inner walls, improves the performance of the heat exchanger. The structure elements arranged in rows are particularly advantageous for exhaust-gas heat exchangers, since in this case deposition of particulates in the interior of the flat tubes is also avoided. A coolant which is taken from the coolant circuit of the internal combustion engine discharging the exhaust gases flows around the outer side of the exhaust-gas tubes. It is also possible for the structures to be stamped into plates or disks in order for heat exchangers to be produced therefrom.
Exemplary embodiments of the invention are illustrated in the drawings and described in more detail in the text which follows. In the drawings:
In a preferred exemplary embodiment, the width b of the flat tube is 40 mm or 20 mm, the total height of the flat tube is approximately 4.5 mm and the height h of the winglets is approximately 1.3 mm. As a result of the winglets projecting into the passage cross section from both sides, in each case to a height of 1.3 mm, given a clear passage height of 4.0 mm, a clear cross-sectional height of 1.4 mm remains for a core flow. The distance s between the rows is approx. 20 mm.
The flat tube 7 is preferably used for exhaust-gas heat exchangers (not shown) which are known per se, i.e. an exhaust gas from an internal combustion engine of a motor vehicle flows through it on its inner side, while coolant from a coolant circuit of the internal combustion engine cools it on its outer side. The outer side of the flat tubes 7—as known from the prior art—may be smooth and held at a distance from adjacent tubes for example by stamped-in studs. However, it is also possible for fins to be provided on the outer side of the flat tubes 7 in order to improve the heat transfer on the coolant side.
Furthermore,
It is in this context important that the structure elements of a row at the top and/or the bottom do not necessarily have to have the same geometric shape or dimensions, as shown by way of example on the basis of four structure elements in
In
The elements shown in
In principle, it is possible for all the structures described to be combined with one another in any desired way.
Claims
1. A flow passage through which a medium can flow in a direction of flow P, of a heat exchanger having two heat exchanger surfaces 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, wherein at least two rows comprising structure elements on substantially opposite heat exchanger surfaces have an overlap with one another.
2. The flow passage as claimed in claim 1, wherein the overlap is 100%.
3. The flow passage as claimed in claim 1, at least one structure element is elongate, in particular rectangular in form and has a straight longitudinal axis.
4. The flow passage as claimed in claim 1, wherein at least one structure element is elongate and angled in form and has an angled longitudinal axis 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, wherein at least one structure element is arcuate in form and has a longitudinal axis 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, wherein at least one structure element is approximately Z-shaped in form and has a doubly curved longitudinal axis with radii 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, at least one structure element is V-shaped in form and has straight V limbs.
8. The flow passage as claimed in claim 1, wherein at least one structure element is V-shaped in form and has V limbs which are curved away from the direction of flow.
9. The flow passage as claimed in claim 1, wherein the height h of at least one of the structure elements is 20% to 50% of the passage height H.
10. The flow passage as claimed in claim 9, wherein the length L of at least one structure element is from two to twelve times the height h of the structure element.
11. The flow passage as claimed in claim 1, wherein the distance s between the rows amounts to 0.5 to eight times the depth T.
12. The flow passage as claimed in claim 1, wherein the distance s between in each case two rows varies in the direction of flow P.
13. The flow passage as claimed in claim 1, wherein at least one structure element has a constant width B in the range from 0.1 to 6.0 mm, preferably in the range from 0.1 to 3.0 mm.
14. The flow passage as claimed in claim 1, wherein at least one structure element has 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 claim 1, wherein 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 claim 4, wherein 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, wherein 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 claim 5, wherein the radii R1 and R2 are equal to the radius R.
19. The flow passage as claimed in claim 1, wherein a row in each case has identical structure elements.
20. The flow passage as claimed in claim 1, wherein a row in each case has different structure elements.
21. The flow passage as claimed in claim 19, wherein individual structure elements are arranged next to one another in pairs at a distance a and in mirror-image fashion with respect to one another.
22. The flow passage as claimed in claim 19, wherein some or all the structure elements are parallel but offset with respect to one another and are arranged in pairs at a distance a transversely with respect to the direction of flow.
23. The flow passage as claimed in claim 21, wherein a distance a between two structure elements may vary within at least one row.
24. The flow passage as claimed in claim 21, wherein the distance a is in the range from 0 to 8 mm.
25. The flow passage as claimed in claim 19, wherein individual structure elements of a row 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 and T being the projection of the length L transversely with respect to the direction of flow P.
26. The flow passage as claimed in claim 22, wherein individual structure elements of a row are not arranged parallel and have a differing flow-off angle α.
27. The flow passage as claimed in claim 22, wherein individual structure elements of a row have different lengths L1, L2.
28. The flow passage as claimed in claim 1, wherein opposite rows have an offset f in the direction of flow P, f being less than the depth T of a row.
29. The flow passage as claimed in claim 1, wherein some or all the structure elements of rows lying opposite one another are oppositely oriented, in particular have an opposite flow-off angle α.
30. The flow passage as claimed in claim 1, wherein the rows lying opposite one another have voids between the structure elements with structure elements of the other row in each case lying opposite these voids.
31. The flow passage as claimed in claim 1, wherein the structure elements of opposite rows touch one another, in particular are joined to one another by welding or soldering.
32. The flow passage as claimed in claim 1, wherein opposite rows of structure elements have the same depth T in the direction of flow P.
33. The flow passage as claimed in claim 1, wherein opposite rows of structure elements have different depths T1, T2 in the direction of flow P.
34. The flow passage as claimed in claim 1, wherein the heat exchange surfaces which lie substantially opposite one another, and in particular the structure elements arranged thereon, are curved.
35. The flow passage as claimed in claim 1, wherein 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.
36. The flow passage as claimed in claim 1, wherein 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.
37. The flow passage as claimed in claim 1, wherein 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.
38. The flow passage as claimed in claim 1, wherein 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.
39. The flow passage as claimed in claim 1, wherein at least one, in particular each row of structure elements comprises in each case a plurality of structure elements.
40. A heat exchanger, in particular an exhaust-gas cooler, in particular for a motor vehicle, having flow passages for a fluid, wherein at least one flow passage is designed as described in claim 1.
41. The heat exchanger as claimed in claim 39, wherein the flow passages are formed as soldered or welded flat or rectangular tubes and the heat exchanger surfaces are formed as flat tube walls.
42. The heat exchanger as claimed in claim 1, wherein the flow passages are formed by stacking plates or disks which have structure elements on top of one another.
43. The heat exchanger as claimed in claim 1, wherein the structure elements are formed into the tube walls in particular by stamping.
44. The heat exchanger as claimed in claim 1, wherein exhaust gas can flow through the tubes and a liquid coolant can flow around the tubes.
45. The heat exchanger as claimed in claim 1, wherein the rows of structure elements are at a distance s from one another in the direction of flow which amounts to two to six times the length L of a structure element.
46. The heat exchanger as claimed in claim 1, wherein between the rows with structure elements there are further rows with structure elements which project outward into fluid 2.
47. The heat exchanger as claimed in claim 45, wherein the outwardly projecting structure elements are supporting studs, webs or elements and touch one another or are welded or soldered to one another.
48. The heat exchanger as claimed in claim 45, wherein the outwardly projecting structure elements contribute to improving the heat transfer.
Type: Application
Filed: Sep 20, 2004
Publication Date: May 17, 2007
Applicant: BEHR GMBH & CO. KG (Stuttgart)
Inventors: Peter Geskes (Stuttgart), Rainer Lutz (Steinheim), Ulrich Maucher (Korntal-Munchingen), Martin Schindler (Kurnach), Michael Schmidt (Bietigheim-Bissingen)
Application Number: 10/577,436
International Classification: F28F 13/12 (20060101);