US20210156631A1

US20210156631A1 - Corrugated rib structure

Info

Publication number: US20210156631A1
Application number: US17/104,674
Authority: US
Inventors: Juergen Barwig; Michael Schmidt
Original assignee: Mahle International GmbH
Current assignee: Mahle International GmbH
Priority date: 2019-11-26
Filing date: 2020-11-25
Publication date: 2021-05-27
Also published as: JP2021085655A; DE102019218266A1

Abstract

A corrugated rib structure for a heat exchanger may include wave-shaped wave crests and wave troughs running in a through-flow direction, and which may be connected with one another via wave-shaped walls running in the through-flow direction; and inwardly flared fins provided in at least one of: (i) the wave crests, and (ii) the wave troughs.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Patent Application No. DE 10 2019 218 266.6, filed on Nov. 26, 2019, the contents of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a corrugated rib structure for a heat exchanger, in particular for an internal combustion engine on a motor vehicle. The invention relates furthermore to a heat exchanger with such a corrugated rib structure.

BACKGROUND

Corrugated rib structures in heat exchangers are sufficiently known and are arranged for example between flat tubes of a heat exchanger block of the heat exchanger, in order to enlarge an area which is available for the exchange of heat. The performance of the heat exchanger can be increased via the size of the area available for the exchange of heat. The aim here is to transfer as much heat as possible with as small a pressure loss as possible. For this reason, various corrugated rib structures already exist, which are formed for example as deep-drawn stamped sheet metal parts. Known corrugated rib structures are, however, here either to be produced at a favourable cost or optimized with respect to their heat transfer capability, so that potential still exists for improvement in a ratio between performance and pressure loss of the heat exchanger.

SUMMARY

The present invention is therefore concerned with the problem of indicating, for a corrugated rib structure of the generic type, an improved or at least an alternative embodiment, which is distinguished in particular by an increased ratio of performance to pressure loss.
This problem is solved according to the invention by the subject matter of the independent claim(s). Advantageous embodiments are the subject matter of the dependent claim(s).
The present invention is based on the general idea, in a corrugated rib structure known per se, to provide a combination of deeply corrugated ribs with flared fins and thereby to improve the ratio between performance of the heat exchanger and pressure loss. For this, the corrugated rib structure has wave-shaped wave crests and wave troughs running in its through-flow direction, which are connected with one another via wave-shaped walls, likewise running in through-flow direction. The wave crests and wave troughs and the walls relate here to a horizontal alignment of the corrugated rib structure. In the wave crests and/or in the wave troughs, in addition, inwardly flared fins are provided here. An air stream which flows through the corrugated rib structure in the through-flow direction, therefore undergoes a redirection similar to a serpentine line with the wave-shaped walls as lateral delimitation. The serpentine through-flow corridors are delimited here above and below (viewed in the case of a horizontal corrugated rib structure) by the wave crests (above) or the waves (below). From these wave crests or respectively wave troughs, the inwardly flared fins according to the invention are now provided, which with such an arrangement in the wave crests project downward and with such an arrangement in the wave troughs project upward, i.e. into an interior of the corrugated rib structure. Hereby, the individual fins serve as turbulence elements which bring about an eddying of the air stream flowing through the corrugated rib structure and thereby improve the heat transfer. In the installed state, the corrugated rib structure according to the invention lies with its wave crests and wave troughs in a planar manner against tubes, for example flat tubes of a heat exchanger block, so that usually through the flared fins only a redirection of the air stream flowing through the corrugated rib structure is brought about in the corrugated rib structure itself, however a deflection of an air stream flowing in the corrugated rib structure over the flared or respectively stamped-out fins outwards, i.e. to outside the corrugated rib structure, does not take place, because the window produced by the stamping-out and flaring of the fins in the wave crest or respectively wave trough is closed by an adjacent flat tube in the installed state.
In a multi-stage heat exchanger with several flat tubes arranged one behind the other in through-flow direction, of course at least individual windows, produced through the flared fins, in the wave crests or respectively wave troughs, can also bring about a deflecting of the air stream flowing through the corrugated rib structure, whereby a further eddying of the air stream and thereby a further improved heat transfer can be created. Through the serpentine through-flow paths in the corrugated rib structure and the simultaneously inwardly flared fins, with the corrugated rib structure according to the invention a turbulent air flow can be created in the corrugated rib structure, which enables a high heat transfer. At the same time, however, the wave-shaped through-flow paths and the inwardly flared fins bring about only a small pressure loss, whereby with the corrugated rib structure according to the invention the ratio between heat exchanger performance and pressure loss can be distinctly improved. Through the increased ratio between heat exchanger performance and pressure loss, with respect to a through-flow length also with the same heat exchanger performance shorter heat exchangers can be built, whereby these can be formed not only with less material and therefore in a resource-conserving manner, but also can be formed smaller with respect to installation space and at a more favourable cost.
In an advantageous further development of the solution according to the invention, the fins are flared inwards about an angle Φ between 30°≤0≤80°, preferably about an angle Φ of ca. 55°. In particular with a flare angle Φ of ca. 55°, a particularly high ratio can be created between heat exchanger performance and pressure loss, wherein this ratio is able to be adapted in the previously mentioned angle range for the angle Φ according to the type, and in particular length, of the corrugated rib structure in through-flow direction.
In an advantageous further development of the solution according to the invention, a wave length L in through-flow direction is between 7 mm≤L≤12 mm. In the case of such a wave length, it has been shown that the ratio between the heat exchanger performance which is to be achieved and the pressure loss is optimal, in particular against the background of a wave amplified A in through-flow direction between 1 and 1.5 mm. In the case of such a wave form, a pressure loss can be kept as small as possible, yet high, through the heat exchanger performance which is able to be achieved through the redirection imposed by the wave form.
Expediently, the fin has a trapezoidal shape with one shorter base side, one longer base side and two legs. The fin is connected here via its longer base side with the respective wave crest or respectively with the respective wave trough. The shorter base side points here contrary to the through-flow direction, whereby with such a trapezoidal fin a fluidically optimized contour can be created which tapers conically contrary to the flow direction. Through such a trapezoidal fin therefore the flow resistance and thus the pressure loss can be kept low. Nevertheless, such a trapezoidal fin enables an eddying of the air stream flowing in the corrugated rib structure, and thereby an improved heat transfer. Furthermore, a trapezoidal fin enables a greater tool service life through the avoidance of a pointed fin end.
In an advantageous further development of the corrugated rib structure according to the invention, the shorter base side has a width B₁of ca. 0.88 mm and the longer base side has a width B₂of ca. 1.6 mm. In this case, the legs have a length Ls of ca. 0.95 mm. Together with the wave length L described in the previous paragraphs, and wave amplitude A, a corrugated rib structure with an optimized ratio of heat exchanger performance and pressure loss can be created.
Expediently, the walls of the respective through-flow paths form an angle β between 92°≤β≤94°, in particular an angle β of 93°, to the wave crest and wave trough connected thereto. The walls of the respective through-flow paths therefore do not run orthogonally to the respective wave crests or respectively wave troughs, which can respectively be formed as plateaus, but rather in a slightly inclined manner, i.e. by ca. 3°±1°, to a surface normal relative to the wave crest or respectively wave trough. Hereby, it is possible to enable a certain compression possibility of the corrugated rib structure transversely to the walls, which enables a compensation of manufacturing tolerances. At the same time, through the walls which are slightly inclined with respect to the surface normal of the wave crests or respectively wave troughs, a comparatively simple shaping of the corrugated rib structure from a sheet metal forming tool is possible, whereby the production process can be simplified and thereby the production costs can be reduced.
In a further advantageous embodiment of the solution according to the invention, a metal sheet of the corrugated rib structure has a thickness d of 0.08 mm to 0.2 mm, in particular 0.15 mm. Such a small thickness of the metal sheet which is used for the corrugated rib structure enables on the one hand a problem-free redirecting of the air stream flowing through the corrugated rib structure and, on the other hand, an optimized heat transfer between the corrugated rib structure and the adjacent flat tubes. At the same time, such thin metal sheets can be produced comparatively simply, i.e. with a small amount of force and thereby also with favourably priced shaping tools, and have in addition only a small weight, which helps not only to conserve resources, but at the same time also reduces a weight of a heat exchanger which is subsequently equipped therewith which, in particular in the case of a use of such a heat exchanger in a motor vehicle, entails advantages with regard to an energy consumption, for example a fuel consumption
The present invention is further based on the general idea of equipping a heat exchanger with at least one corrugated rib structure described in the previous paragraphs. Hereby, the advantages described in the previous paragraphs with regard to the corrugated rib structure can be transferred to the heat exchanger, so that the latter is able to be produced at a favourable cost with a comparatively low weight and, at the same time, has a large ratio between heat exchanger performance and pressure loss.
Further important features and advantages of the invention will emerge from the subclaims, from the drawings and from the associated figure description with the aid of the drawings.
It shall be understood that the features mentioned above and to be explained further below are able to be used not only in the respectively indicated combination, but also in other combinations or in isolation, without departing from the scope of the present invention.
Preferred example embodiments of the invention are illustrated in the drawings and are explained more closely in the following description, wherein the same reference numbers refer to identical or similar or functionally identical components.

BRIEF DESCRIPTION OF THE DRAWINGS

There are shown here, respectively schematically,

FIG. 1 shows a top view onto a corrugated rib structure according to the invention,

FIG. 2 shows a view onto a corrugated rib structure according to the invention,

FIG. 3 shows a sectional illustration along the section plane A-A,

FIG. 4 shows a detail illustration Z of FIG. 1,

FIG. 5 shows a schematized illustration of the wave-shaped pass-through paths,

FIG. 6 shows a sectional illustration through the corrugated rib structure according to the invention in the region of an inwardly flared fin.

DETAILED DESCRIPTION

According to FIGS. 1 to 3, a corrugated rib structure 1 according to the invention for a heat exchanger 2, in particular for an internal combustion engine in a motor vehicle 3, has wave-shaped wave crests 5 and wave troughs 6 running in its through-flow direction 4 (cf. in particular also FIGS. 3, 4 and 6, which are connected with one another via wave-shaped walls 7 also running in through-flow direction 4, wherein in the wave crests 5 and/or in the wave troughs 6 inwardly flared fins 8 are provided (cf. in particular FIGS. 1, 3, 4 and 6). Via the wave-shaped wave crests 5 and wave troughs 6 running in through-flow direction 4, which themselves are formed in a plateau-shaped manner, and the likewise wave-shaped walls 7 and the fins 8, a ratio between a heat exchanger performance and a pressure loss can be optimized, so that a heat exchanger 2, equipped with the corrugated rib structure 1 according to the invention, has an optimum heat exchanger performance with, at the same time, a minimized pressure loss.
The fins 8 can be flared inwards here about an angle Φ between 30°≤Φ≤80°, preferably about an angle Φ of ca. 55°, i.e. according to FIG. 3 with a fin 8 from the wave crest 5 downwards and with a fin 8 from the wave trough 6 upwards. In tests, it has been found here that the pressure loss with a flare angle Φ of the respective fin 8 of ca. 30° lies at ca. 1,750 Pa and with a flare angle Φ of ca. 70° rises to 2,250 Pa. In same range, the heat output in the test rises from 76.65 Watt to 77.1 Watt, wherein the curve of the heat output exceeds the curve of the pressure loss with a (bending) angle Φ between 45° and 65°, so that in this range of the angle or respectively flare angle Φ an optimum ratio between heat output and pressure loss exists.
A wave length L in through-flow direction 4 here is preferably between 7 mm≤L≤12 mm, while a wave amplitude A in through-flow direction 4 lies between 1 mm≤A≤1.5 mm.
Observing the fin 8, in particular according to FIG. 4, more closely, it can be seen that it has a trapezoidal shape with one shorter base side 9, one longer base side 10 and two legs 11. The fin 8 is connected here via the longer base side 10 to the respective wave crest 5 or respectively to the respective wave trough 6. As can be seen according to FIG. 4, the respective fin 8 is aligned here with its shorter base side 9 contrary to the through-flow direction 4, which offers fluidic advantages. The fin 8 is firstly stamped out here in the production method and is subsequently flared, i.e. shaped. In the region of the fin 8, which is stamped out from the wave crest 5 or respectively of the wave trough 6 and flared, a window 12 results (cf. in particular FIG. 6) via which, with a corrugated rib structure 1 installed in a heat exchanger 2, a direct contact exists of the air stream flowing through the corrugated rib structure 1 with, for example, a flat tube lying in a planar manner against the respective wave crest 5 or respectively wave trough 6. Hereby, in the window 12 a particularly direct and thereby efficient heat transfer can take place.
The shorter base side 9 of the fin 8 can have a width B₁of ca. 0.8 mm, while the longer base side 10 can have a width B₂of ca. 1.6 mm. A length Ls of the leg 11 can be for example 0.95 mm (cf. in particular FIG. 4). In addition, the longer base side 10 via which the fin 8 is connected to the respective wave trough 6 or respectively to the respective wave crest 5, can be inclined by an angle α of ca. 70° (cf. FIG. 4) to the through-flow direction 4.
Observing the walls 7, it can be seen that these form an angle β between 92°≤β≤94°, in particular an angle β of ca. 93° to the wave crest 5 or respectively wave trough 6 connected thereto (cf. FIG. 3). This serves in particular for the better demouldability from a sheet metal forming tool and thereby facilitates the production and makes this more favourably priced.
Basically, a wave crest 5 can have a saddle width B_Sof 2.0 mm to 4.0 mm, in particular of ca. ca. 2.5 mm (cf. FIG. 3), wherein a wave trough can have a trough width B_T, identical hereto, of likewise from 2.0 mm to 4.0 mm, in particular of ca.ca. 2.5 mm. The corrugated rib structure 1 can have in total a height H of 3.0 mm to 5.0 mm, in particular of ca. 4 mm, particularly preferably of 3.42 mm. For the corrugated rib structure 1 for example a metal sheet with a thickness d of 0.08 mm to 0.2 mm, in particular 0.15 mm, is used, whereby the corrugated rib structure according to the invention is not only to be shaped easily and thereby at a favourable cost, but at the same time also consumes few resources and has a low weight, which is of great advantage in particular in the case of a use in a heat exchanger 2 in an internal combustion engine of a motor vehicle 3.
All in all, with the corrugated rib structure 1 according to the invention, a heat exchanger performance can be increased and, at the same time, a pressure loss can be reduced, whereby for example heat exchangers 2 equipped with such a corrugated rib structure 1 can be constructed smaller, in particular shorter, or with the same overall size achieve a higher performance.

Claims

1. A corrugated rib structure for a heat exchanger comprising:

wave-shaped wave crests and wave troughs running in a through-flow direction, and which are connected with one another via wave-shaped walls running in the through-flow direction; and

inwardly flared fins provided in at least one of: (i) the wave crests, and (ii) the wave troughs.

2. The corrugated rib structure according to claim 1, wherein the fins are flared inwards about an angle Φ between 30°≤Φ≤80°.

3. The corrugated rib structure according to claim 1, wherein a wave length L in the through-flow direction is between 7 mm≤L≤12 mm.

4. The corrugated rib structure according to claim 1, wherein a wave height H in through-flow direction is between 1 mm≤H≤1.5 mm.

5. The corrugated rib structure according to claim 1, wherein the fin has a trapezoidal shape with one shorter base side, one longer base side and two legs.

6. The corrugated rib structure according to claim 5, wherein at least one of:

the shorter base side has a width of about 0.88 mm;

the longer base side has a width of about 1.6 mm; and

the legs have a length of about 0.95 mm.

7. The corrugated rib structure according to claim 5, wherein the longer base side of the trapezoidal fin is inclined about an angle α of about 70° to the through-flow direction.

8. The corrugated rib structure according to claim 1, wherein the walls form an angle β between 92°≤β≤94° to a corresponding wave crest and wave trough connected thereto.

9. The corrugated rib structure according to claim 1, wherein the corrugated rib structure is formed as a deep-drawn sheet metal stamped part.

10. The corrugated rib structure according to claim 1, wherein at least one of:

at least one wave crest has a saddle width of 2 mm to 4 mm;

at least one wave trough has a trough width of 2 mm to 4 mm; and

the corrugated rib structure has a height of 3 mm to 5 mm.

11. The corrugated rib structure according to claim 1, wherein a metal sheet of the corrugated rib structure has a thickness of 0.08 mm to 0.2 mm.

12. A heat exchanger comprising at least one corrugated rib structure having:

13. The heat exchanger according to claim 12, wherein at least one of:

the fins are flared inwards about an angle Φ between 30°≤Φ≤80°;

a wave length L in the through-flow direction is between 7 mm≤L≤12 mm;

a wave height H in through-flow direction is between 1 mm≤H≤1.5 mm; and

the walls form an angle β between 92°≤β≤94° to a corresponding wave crest and wave trough connected thereto.

14. The heat exchanger according to claim 12, wherein the fin has a trapezoidal shape with one shorter base side, one longer base side and two legs.

15. The heat exchanger according to claim 14, wherein at least one of:

the shorter base side has a width of about 0.88 mm;

the longer base side has a width of about 1.6 mm; and

the legs have a length of about 0.95 mm.

16. The heat exchanger according to claim 14, wherein the longer base side of the trapezoidal fin is inclined about an angle α of about 70° to the through-flow direction.

17. The heat exchanger according to claim 12, wherein at least one of:

at least one wave crest has a saddle width of 2 mm to 4 mm;

at least one wave trough has a trough width of 2 mm to 4 mm; and

the corrugated rib structure has a height of 3 mm to 5 mm.

18. The corrugated rib structure according to claim 2, wherein 1 is approximately 55°.

19. The corrugated rib structure according to claim 11, wherein the thickness of the metal sheet is 0.15 mm.

20. A corrugated rib structure for a heat exchanger comprising:

inwardly flared fins provided in at least one of: (i) the wave crests, and (ii) the wave troughs;

wherein:

the fins are flared inwards about an angle Φ between 30°≤Φ≤80°;

a wave length L in the through-flow direction is between 7 mm≤L≤12 mm;

a wave height H in through-flow direction is between 1 mm≤H≤1.5 mm; and