WO2008097405A1

WO2008097405A1 - Heat exchanger tube and method of forming the same

Info

Publication number: WO2008097405A1
Application number: PCT/US2007/085921
Authority: WO
Inventors: Martin Ploppa; Daniel Borst
Original assignee: Modine Manufacturing Company
Priority date: 2007-02-10
Filing date: 2007-11-29
Publication date: 2008-08-14
Also published as: BRPI0721313A2; CN101600931A; DE102007006664A1; CN101600931B

Abstract

The invention relates to flat heat exchanger tubes, having two narrow and two broad sides. The flat tubes can be manufactured from two continuous strips, having a relatively large curve on one longitudinal edge of the strips and having a relatively small curve on the other longitudinal edge of the strips. The two strips are arranged laterally transposed with respect to one another, to form the wall of the flat tubes, so that the relatively large curve of the longitudinal edge of one strip holds in itself the relatively small curve of the longitudinal edge of the other strip to form the narrow sides of the flat tubes. The strips are formed with at least one further contoured portion which extends in the longitudinal direction of the flat tubes and which improves the cohesion of the flat tube.

Description

HEAT EXCHANGER TUBE AND METHOD OF FORMING THE SAME

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Priority is hereby claimed to German Patent Application No. DE 10 2007 006664.5 filed February 10, 2007, the entire contents of which is incorporated herein by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a flat tube for heat exchangers, such as, for example, charge air coolers for motor vehicles. The heat exchanger tubes can have two narrow sides and two broad sides and can be manufactured from two contoured, continuous strips, having a relatively large curve on one longitudinal edge of the strips and having a relatively small curve on the other longitudinal edge of the strips. The two strips can be arranged with respect to one another, in order to form the wall of the flat tube, in such a way that the relatively large curve of the longitudinal edge of one strip holds in itself the relatively small curve of the longitudinal edge of the other strip (and vice versa) in order to form the narrow sides of the flat tube.

SUMMARY

[0003] Flat tubes are known from a number of relatively old applications. One of the applications has been given the file number DE 10 2006 006 670.7. Figure 1 shows a flat tube from the aforesaid application in cross section. This flat tube has a corrugated inner part z in addition to the features enumerated above. The flat tube is defined by an extremely thin wall thickness, for example in the range from 0.03 mm - 0.15 mm or slightly above. Such flat tubes have also already been manufactured by the applicant and installed on a trial basis in heat exchangers. Until now the heat exchangers have successfully passed all the validation phases so that they are expected to be made commercially available soon.

[0004] In some of the flat tubes, undesired changes in shape of the not yet soldered flat tubes occurred within the course of manufacture. The flat tubes arc soldered later after they have been pre-mounted on the heat exchanger mesh using ribs. The changes in shape are possibly due to material stresses which are present in the material (aluminum sheet steel) or are generated by the necessary shaping of the strips. The changes in shape can lead to unsatisfactory solder connections, but they can also, for example, impede the joining to the corrugated inner part z. The appended Figures 2a and 2b are intended to clarify the problem referred to here. One of the narrow sides of the flat tube has been illustrated on the left of Figure 2a. From the two illustrations on the right hand side in Figure 2a it is apparent that the curves in the narrow sides of the flat tube can spring apart from one another as a result of the effect of the shaping force during the manufacture of the flat tubes, for which reason, as stated, the soldering quality in the subsequent soldering process suffers. The arrows are intended to illustrate the forces which can lead to the aforementioned springing apart and which act on the flat tube in the course of its processing to form the heat exchanger. One of the narrow sides of the flat tube is also illustrated in Figure 2b. From the illustration on the right hand side in Figure 2b it is apparent that, as a result of unequal application of force during the shaping process of the flat tubes, the relatively large curve B does not remain in its provided position as a result of internal stresses.

[0005] In the already mentioned Figure 1 it is also apparent that the strips or the wall parts of the flat tube can be displaced in the direction of the arrows shown there, which ultimately could cause the strips to fall apart if the above-mentioned inner part z were not present. One independent object of the invention is to eliminate or alleviate the described disadvantages.

[0006] According to one aspect, there is provision for the strips to be embodied with corresponding contoured portions which extend in the longitudinal direction of the flat tubes and which improve the cohesion of the flat tube formed from the strips by virtue of the fact that the contoured portions interact with the respective other strip. This at least largely prevents the flat tubes from springing apart or being able to be pushed apart during their processing to form the heat exchanger, that is to say before the soldering process of the heat exchanger is carried out. The preconditions for better soldering quality have thus been provided.

[0007] The two strips are particularly preferably embodied in an identical way. The contoured portions are preferably embodied as beads or as a bend or the like. The contoured portions are preferably arranged at the start and/or at the end of the curves. [0008] In a specific case, which is preferred currently, there is provision for the contoured portions to be arranged approximately at the start of the large curve of one strip and to interact with the end of the small curve of the other strip. In another specific case there is provision for the contoured portions to be arranged approximately at the start of the large curve of one strip and to interact with a section of the small curve of the other strip. This case is currently also preferred because, in this context, the small curve can be embodied with multiple layers in an extremely favorable way, as a result of which even more stable narrow sides are produced.

[0009] In specific case, there is provision for the contoured portions to be arranged approximately at the start of the small curve and approximately at the end of the large curve of the two strips, in which case they interact in such a way that the contoured portions fit into one another approximately.

[0010] In one advantageous development there is provision for the large curves and/or the small curves to be embodied in multiple layers. The multiply layered structure is brought about by folds in the curves. In this way it is possible, as mentioned, to considerably strengthen the narrow sides of the flat tube.

[0011] The invention will be described in a plurality of exemplary embodiments by means of the appended sketches. Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The individual figures show the following:

[0013] Fig. 1 shows the cross section through a prior art flat tube.

[0014] Figs. 2a and 2b show a problem with the prior art flat tube.

[0015] Figs. 3a-d show a first exemplary embodiment for solving the problem shown in Fig. 2a,

[0016] Figs. 4a-d show a second exemplary embodiment for solving the problem shown in Fig. 2a, [0017] Figs. 5a-d show a third exemplary embodiment for solving the problem shown in Fig. 2a,

[0018] Figs. 6a-d show a fourth exemplary embodiment for solving the problem shown in Fig. 2b,

[0019] Figs. 7a-d show a fifth exemplary embodiment for solving the problems shown in Figs. 2a and 2b,

[0020] Fig. 8 shows a suitable additional measure for the third exemplary embodiment and thus a solution of the problems shown in Figs. 2a and 2b, and

[0021] Fig. 9 shows individual steps in the course of the manufacture of a strip.

DETAILED DESCRIPTION

[0022] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," or "having" and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms "mounted," "connected," "supported," and "coupled" and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, "connected" and "coupled" are not restricted to physical or mechanical connections or couplings.

[0023] The five exemplary embodiments have each been represented with four illustrations which have been designated by the letters a-d. The illustration a shows in each case an enlarged view of a large or small curve B, b of a contoured strip. The illustration b always shows one of the contoured strips. The illustration c shows a narrow side 1 of the flat tube formed from a large curve B of the one strip and a small curve b of the other strip. Finally, the illustration d shows the respective flat tube as a view which corresponds to a cross section through the flat tube.

[0024] In all the exemplary embodiments shown, an inner part z may be present, for example such an inner part is shown in Fig. 1. In all the exemplary embodiments shown, a step a, which is compensated by applying the large curves B, is located approximately at the start of the small curves b. The term "curve" should not be understood here in a restrictive fashion as a circle-like or parabola-like curve or the like. The term "curve" should also be understood to be an embodiment which has, for example, straight narrow sides 1 with two edge portions which constitute the transitions from the narrow side 1 into the two broad sides 2.

[0025] In all the exemplary embodiments the two strips x and y are substantially identical and are arranged in a laterally transposed fashion with respect to one another in order to form the flat tube. In addition, the strip thickness should be approximately in the range from 0.03 mm - 0.15 mm or slightly above that. In addition, the strip thickness for an inner part, if one is provided, should be in the range from 0.03 - 0.09 mm. In addition, the flat tubes should only preferably be flat tubes for charge air coolers which are used in motor vehicles. All other heat exchanger applications and fields of use are not excluded. The large or relatively large curve B has been referred to as such because it is suitable for holding in itself the other curve which has been referred to as the small or relatively small curve b. In fact, in view of the extremely thin sheet metal thicknesses there are no size differences between the curves B, b which can be perceived on first sight.

[0026] The first exemplary embodiment according to Fig. 3 shows as a contoured portion u a bead which is folded onto itself and which is located approximately at the start of the large curves B of the two strips x, y and which extends over the entire length of the flat tube. As is clarified by Fig. 3 c, the end of the small curve b of the other strip y bears against this bead, as a result of which the bead interacts with the other strip y. The end of the small curve b has been provided in this exemplary embodiment with a turnover v of the edge of the ribbon-shaped material in order to improve the interaction of the end of the small curve b with the bead u during the manufacturing process and rabbeting of the flat tube. The cohesion of the two strips of the flat tube is thus improved. [0027] The exemplary embodiment according to Fig. 4 gives rise to flat tubes whose narrow sides 1 are embodied with three layers. A simple bend is provided as a contoured portion u which is located at the end of the large curves B. The large curves B have a simple fold. In each case the end of the small curve b of the other strip bears against the aforesaid bend u, as a result of which the bend u interacts with the other strip. Here too, the strip with the relatively small curve b can be provided at the end with a turnover v of the edge of the ribbon-shaped material according to exemplary embodiment 3 (not illustrated in Figure 4 here).

[0028] The exemplary embodiment according to Fig. 5 also gives rise to narrow sides 1 with three layers. As in the first exemplary embodiment, a bead as a contoured portion u is also arranged here at the start of the relatively large curve B. However, in contrast to the embodiments described hitherto the relatively small curve b of the other strip is provided with a fold f which results in doubling, a section vl of the doubled small curve b bearing against the aforementioned bead u, as a result of which the bead interacts with the other strip. Because, as a result of the fold f of the other strip, the end of the relatively small curve b, referred to here as vl, is embodied with a double layer, the end vl acts in a way corresponding to the turnover v of the edge of the ribbon-shaped material of the exemplary embodiments according to Figure 3 and Figure 4. An additional turnover of the edge of the ribbon-shaped material can be dispensed with here.

[0029] In the exemplary embodiment according to Fig. 6, the two strips x, y of the flat tube each have two contoured portions ul and u2. An "open" bead is provided as a contoured portion ul approximately at the start of the small curve b, and a bead which is folded onto itself is provided approximately at the end of the large curve B as a contoured portion u2. The beads ul, u2 are matched in terms of their dimensions so that the bead u2 at the end of the large curve B of the one strip fits into the open bead ul at the start of the small curve b of the other strip, as a result of which the bead interacts with the other strip.

[0030] In the exemplary embodiment according to Fig. 7, another flat tube with three-layered narrow sides 1 is presented. The relatively large curve B has been doubled here and a bend is provided at the end of the relatively large curve B as contoured portion ul. In a section of the doubled portion a bead which has been folded onto itself and which is referred to as contoured portion u2 is provided. Approximately at the start of the relatively small curve b an "open" bead which is referred to as contoured portion u3 has been provided. The contoured portion u3 at the start of the relatively small curve b of the one strip engages over the folded bead u2 in the doubled portion of the relatively large curve B of the other strip. In addition, the end of the relatively small curve b (just mentioned) of the one strip bears against the bend ul at the end of the relatively large curve B of the other strip, as a result of which the bend ul interacts with the other strip.

[0031] Fig. 8 shows in two illustrations a development of the exemplary embodiment according to Fig. 5 which consists in the fact that the end of the relatively large curve B of the one strip is provided with a slightly smaller bend angle w so that in a last step the aforementioned end can be pushed, with a certain degree of pre-stress, onto or against the start of the relatively small curve b, having the step a, of the other strip, as a result of which the dimensional stability is increased further.

[0032] In order to conclude the process, Fig. 9 shows a number of steps for manufacturing a single strip x or y. The manufacturing method for all the strips x, y and possibly z of the flat tube or for the flat tubes is carried out on a roller train or fabrication line which is shown and described in the above-mentioned applications with priority dates earlier than that of the present document. As can be discerned by comparison, this illustration relates to the manufacture of the strips x, y which are used in the first exemplary embodiment according to Fig. 3. The formation of the contoured portion u is begun starting from the continuous strip x or y which has not yet been shaped, after which the formation of the relatively large curve B is started. This is followed by the steps shown in the left-hand column which are continued in the right- hand column, at the top. The illustration at the bottom shows a strip x or y which has been completed. The two identical strips x and y are combined approximately in the state according to the eleventh step, in the right-hand column at the bottom, in a laterally transposed fashion to form the flat tube, the other strip x or y (not shown there) being placed from above, with its relatively small curve b, into the relatively large curve B, not yet completed, of the illustrated strip x or y, the relatively large curve B of the strip which is not illustrated engaging around the relatively small curve b of the illustrated strip from above. [0033] The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention as set forth in the appended claims.

Claims

CLAIMSWhat is claimed is:

1. A flat tube for heat exchangers, the flat tube comprising: two narrow sides and two broad sides, being manufactured from two continuous strips, having a relatively large curve on one longitudinal edge of the strips, and having a relatively small curve on an other longitudinal edge of the strips; wherein the two strips are arranged with respect to one another, in order to form a wall of the flat tube, in such a way that the relatively large curve of the longitudinal edge of one strip holds in itself the relatively small curve of the longitudinal edge of the other strip in order to form the narrow sides of the flat tube; wherein each of the two the strips includes at least one further contoured portion which extends in a longitudinal direction of the flat tube and which improves cohesion of the flat tube formed from the strips by virtue of the fact that the further contoured portion of one strip interacts with the respective other strip.

2. The flat tube according to claim 1, wherein the contoured portions are embodied as one of beads and bends.

3. The flat tube according to claim 1, wherein the contoured portions are arranged at one of the start and the end of the curves.

4. The flat tube according to claim 1, wherein the contoured portions are arranged approximately at the start of the large curves of one strip and interact with the end of the small curves of the other strip.

5. The flat tube according to claim 4, wherein the end of the small curve includes a turnover of the edge of the strip.

6. The flat tube according to claim 1 , wherein the contoured portions are arranged approximately at the start of the large curves of one strip and interact with a section of the small curves of the other strip.

7. The flat tube according to claim 1 , wherein the contoured portions are arranged approximately at the start of the small curves and approximately at the end of the large curves of the two strips, wherein the contoured portions fit into one another.

8. The flat tube according to claim 7, wherein the contoured portions are beads, one bead being embodied as an open bead into whose opening the other bead fits.

9. The flat tube according to claim 1 , wherein the large curves and/or the small curves are embodied in multiple layers formed at least in part by a fold.