FLAT HEAT EXCHANGER TUBE

Abstract

A flat heat exchanger tube is formed from a single metal strip and comprising two opposite spaced apart broad sides in a thickness direction of said tube and two opposite nose-forming narrow sides in a width direction of said tube. The strip has two longitudinal edges, the first longitudinal edge being contiguous to the first broad side and the second longitudinal edge being contiguous to the second broad side. The two longitudinal edges of the strip are joined together at a first one of the narrow sides, both longitudinal edges being convex-shaped so that the first edge forms an outer convex bend and the second edge forms an inner convex bend that fits in the outer convex bend and conforms to its internal curvature.

Claims

1-15. (canceled)

16. A flat heat exchanger tube formed from a single metal strip, comprising: two opposite spaced apart broad sides in a thickness direction of said tube and two opposite nose-forming narrow sides in a width direction of said tube; wherein the strip has two longitudinal edges, the first longitudinal edge being contiguous to the first broad side and the second longitudinal edge being contiguous to the second broad side; said two longitudinal edges of the strip are joined together at a first one of the narrow sides, both longitudinal edges being convex-shaped so that the first edge forms an outer convex bend and the second edge forms an inner convex bend that fits in the outer convex bend and conforms to its internal curvature; the second longitudinal edge has a terminal section that is bent to extend across the thickness of the tube to form a closed, edge channel delimited in the width direction by the inner convex bend and by the terminal section.

17. The flat heat exchanger tube according to claim 16, wherein the second broad side has a bend toward the tube interior connecting the second longitudinal edge.

18. The flat heat exchanger tube according to claim 17, wherein said bend toward the tube interior has a size corresponding roughly to the strip thickness, and the outer bend of the first longitudinal edge has its terminal edge in close fit with said bend, coming flush with the second broad surface.

19. The flat heat exchanger tube according to claim 16, wherein the inner convex bend is U-shaped and the terminal section comprises a leg that extends across the thickness of the tube and a foot that bears against the inner side of the U-shaped inner convex bend.

20. The flat heat exchanger tube according to claim 16, wherein the terminal section comprises a straight leg that is bent back to have its extremity in abutment against the inner side of the inner convex bend.

21. The flat heat exchanger tube according to claim 16, wherein the terminal section is substantially C-shaped, the interior of the C facing the inner side of inner bend, wherein the inner bent section has an essentially circular shape and the terminal section has a first straight section along the inner side of the first broad side, a leg extending in thickness direction and a foot extending along the inner side of the second broad side, towards the bend.

22. The flat heat exchanger tube according to claim 21, wherein the foot ends by the bend before the inner bent section.

23. The flat heat exchanger tube according to claim 16, wherein the inner bent section has a generally curved shape and the terminal section extends at the base of the inner bend; wherein the terminal section has a straight leg extending substantially in the thickness direction and a perpendicular foot (330.2) extending along the inner side of the second broad side, away from the inner convex bend; and wherein the leg is preferably positioned at the basis of the inner convex bend, against bend.

24. The flat heat exchanger tube according to claim 16, wherein the terminal section is sealingly bound to the inner convex bend or the second broad side.

25. The flat heat exchanger tube according to claim 16, wherein the strip is cladded on both sides with a thin layer of brazing material.

26. The flat heat exchanger tube according to claim 16, further comprising a fold formed in one of the broad sides and extending in thickness direction to the opposite broad side, the fold separating the inner tube volume into two chambers.

27. The flat heat exchanger tube according to claim 26, wherein the chamber adjacent the edge channel has a height-to-width ratio of less than 1.

28. The flat heat exchanger tube according to claim 16, wherein the terminal section comprises a leg that extends, preferably perpendicularly, across the thickness of the tube and a foot that bears against the inner side of the second broad side, the contact surface between the foot and the second broad side being superior to, preferably at least twice, the thickness of the leg, the foot being brazed against second broad side; and the tube comprising only two flow chambers, separated by a fold formed in one of the broad sides and extending in thickness direction to the opposite broad side.

29. The flat heat exchanger tube according to claim 28, wherein the tube inner volume does not comprise a corrugated inner fin.

30. A radiator, comprising: an exchanger core with a plurality of parallel flat heat exchanger tubes as recited in claim 16, the tubes in communication at one end with a first tank and the other end with a second tank.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[0030] FIG. 1: is a perspective view of a flat heat exchanger tube according to an embodiment of the invention;

[0031] FIG. 2: is a detail view of the front nose of the heat exchanger tube of FIG. 1;

[0032] FIG. 3 is a cross-sectional view of the front nose of heat exchanger tubes according to further embodiments of the invention.

[0033] FIG. 4 is a cross-sectional view of the front nose of heat exchanger tubes according to further embodiments of the invention.

[0034] FIG. 5 is a cross-sectional view of the front nose of heat exchanger tubes according to further embodiments of the invention.

DETAILED DESCRIPTION

[0035] FIG. 1 is a perspective view of a first embodiment of the present flat heat exchanger tube 10. Such a tube 10 will be advantageously used in a heat exchanger, in particular a radiator, as is known by those skilled in the art. For example, a plurality of parallel such tubes 10 may be secured between two tanks equipped with header plates to convey a fluid (single or two-phase) between the tanks, which fluid may be cooled by a second fluid (such as air) passing over the outside of the tubes 10. Suitable fins (not shown), including louvered and plate fins, may be provided at the periphery of the tubes 10 to facilitate heat exchange between the fluid in the tubes 10 and the second fluid, as is generally well known.

[0036] The present tube 10 may be advantageously produced from a single deformable metal sheet strip 11 (or plate) of limited sheet thickness, e.g. made of aluminum sheet, through a number of forming steps, namely folding steps. The initial shape of the steel strip is normally rectangular or square. Any shape of the present folded tube's 10 cross-section can be produced by providing progressive form rollers of suitable shape. Apparatuses and processes for forming heat exchanger tubes by folding, and in particular tube mill equipment, are well known in the art and can be adapted by the skilled person to produce the present heat exchanger tubes.

[0037] Tube 10, in its final configuration after forming, has two opposite broad sides 12, 14 and two opposite narrow sides 16, 18, also referred to as nose.

[0038] The broad sides 12, 14 delimit the thickness of tube 10 and thus extend in thickness direction Z. The narrow sides 16, 18 delimit the width of the tube in width direction X. The narrow sides extend in the longitudinal direction of the tube 10, along direction Y. In FIG. 1, only part of the tube 10 is shown from one of its open ends, but it is clear that the length of the tube 10 will generally by substantially larger than its width. As can be seen, the strip 11 is folded so that the longitudinal edges 20, 22 of the strip 11 meet at one narrow side, namely nose 16, thereby peripherally closing the tube 10.

[0039] As will be understood, the term “longitudinal edge” is used herein to designate a longitudinally extending region or band at the edge of the strip, which may also be referred to as border region or margin region.

[0040] A connection 24 is arranged between the two broad sides 12, 14 and divides the heat exchanger tube 10 into two chambers 26, 28 having the same cross-sectional size when the connection 24 is situated roughly in the center of the tube, between the narrow sides 16, 18. It would be within the scope of the present invention, however, to locate the connection 24 outside of the center, in which case the chambers 26, 28 could have different cross-sectional sizes. The connection 24 is achieved by a fold of the strip 11 in the thickness direction.

[0041] In principle, additional folds may also be provided to variously subdivide the chambers 34, 36 as desired, whereby more than two chambers 34, 36 may be produced from the sheet strip 11.

[0042] However, the particular intention of the present design is to confer strength to a tube having large chambers. The tubes may have a width (direction X) greater than 4 mm, e.g. of 4 to 15 mm, and an internal height (direction Z) between 1.0 and 2.5 mm. The cross-sectional area of the chambers may typically be between 4.0 and 38 mm.sup.2.

[0043] In practice, when the heat exchanger is mounted in a car for example, the tube nose turned towards the front of the car is prone to damage due to road hazards (impacts by rocks and debris) and to corrosion, as explained above.

[0044] In the present embodiment, the narrow edge 16 is designed to be facing the front of the car, and may thus be referred to as front or leading nose. The other narrow edge 18 will then be the trailing nose.

[0045] The front nose 16 is reinforced by way of a multilayer design. The strip 11 has two longitudinal edges, each contiguous to a respective broad side. The longitudinal edges 20, 22 are joined together at the front nose 16, both longitudinal edges 20, 22 being convex-shaped so that a first edge 20 forms an outer convex bend 21 and the second edge 22 forms an inner convex bend 23 that fits therein and adopts the internal curvature of the first edge 20. The bends 21 and 23 may be curve or curvilinear shaped, in particular circular or U-shaped. The mating profiles of the inner and outer bends 21 and 23 provides an intimate contact between these that will allow soldering/brazing them together.

[0046] Referring to the orientation in FIG. 1, the top broad side 12 ends is contiguous the first longitudinal edge 20 that forms the outer convex bend 21, whereas the bottom broad side 14 is contiguous with the second longitudinal edge 22 forming the inner convex bend 23.

[0047] It will be appreciated that the second longitudinal edge 22 has a terminal section 30, after the inner convex bend 23, that bends back onto the inner side of the inner convex bend 23 to form a closed edge channel 32.

[0048] As will be understood, the term “terminal section” is used herein to designate a narrow end region (or end margin) within the longitudinal edge, contiguous to the very edge of the sheet.

[0049] As better seen in FIG. 2, the second longitudinal edge 22 is the part of the strip 11 forming the bottom broad side 14 that ends at the front nose 16. The second longitudinal edge 22 comprises the convex bent section 23 connected on one side to the bottom broad side 14, via a short bent section 34. The convex bent section 23 describes a convex curve, here substantially U-shaped, matching the curvature of the outer bend 21, and extending from the bottom broad side 14 to the inner side of the top broad side 12. The second longitudinal edge 22 ends with the terminal section 30, that extends substantially in the tube thickness direction Z from the top broad side 12 to the bottom broad side 14, thus bending back onto itself. The terminal section 30 extends across the thickness direction to come against the inner side of the U-shaped bent section 23. Here the terminal section 30 has a leg 30.1 and a foot 30.2.

[0050] The terminal section 30 extending in the thickness direction, in particular via leg 30.1, brings additional mechanical resistance in the rearward region of the nose 16. There is thus three layers of material at the nose 16, the two superposed front layers formed by the bent sections 21 and 23, and one at the back, i.e. the leg 30.1. The channel 32 arranged between the two bend sections and the terminal section will allow for mechanical deformation of the bent sections 21, 23, without direct contact with the terminal section 30. As a matter of fact, the terminal section 30 extending in thickness direction and spaced from the bent sections 21, 23, permits absorbing part of the front nose deformation in case of shocks. The front nose is thus capable of absorbing more energy, without leading to leakage.

[0051] The front nose configuration of the present tube is of particular interest for tubes with coolant chambers of relatively large cross-section. This is the case in the shown embodiment where the tube has only two chambers 26 and 28, and thus has globally less transversal rigidity than a tube having a multiplicity of chambers divided by folds similar to fold 24.

[0052] Another embodiment of the present front nose configuration is shown in FIG. 3. Same or similar elements are indicated by same reference signs, augmented by 100 as compared to the embodiment of FIGS. 1 and 2. Similar to the front nose configuration of FIG. 2, the nose 116 is formed by the joining of the longitudinal edges 120, 122, both longitudinal edges 120, 122 being convex-shaped so that a first edge 120 forms an outer convex bend 121 and the second edge 122 forms an inner convex bend 123 that fits therein and adopts the internal curvature of the first edge 120. The terminal section 130 of the second longitudinal edge 122 is bent back to extend across the tube substantially in the thickness direction. Here the terminal section 130 has a straight section 130.1, the edge 131 of which is in abutment against the base of the convex bent section 123, just after bend 134. The gap between the convex bent section 123 and the terminal section 130 forms a closed edge channel 132.

[0053] Turning to FIG. 4, a further embodiment is illustrated. Same or similar elements are indicated by same reference signs, augmented by 200 as compared to the embodiment of FIGS. 1 and 2. The nose 216 is formed by the joining of the longitudinal edges 220, 222. Both longitudinal edges 220, 222 are convex-shaped so that a first edge 220 forms an outer convex bend 221 and the second edge 222 forms an inner convex bend 223 that fits therein and conforms to the internal curvature of the first edge 220. The terminal section 230 has a kind of C shape, where the interior of the C faces the inner side of inner bend 223. That is, the inner bent section 223 has an essentially circular shape and the terminal section 230 has a first straight section 230.3 along the inner side of the top broad side 212, a leg 230.1 extending in thickness direction and a foot 230.2 extending along the inner side of the bottom broad side 214, towards the bend 234. The foot ends by the bend 234 before the inner bent section 223.

[0054] A fourth embodiment of the present tube is shown in FIG. 5. Same or similar elements are indicated by same reference signs, augmented by 300 as compared to the embodiment of FIGS. 1 and 2. The nose 316 is formed by the joining of the longitudinal edges 320, 322. Both longitudinal edges 320, 322 are convex-shaped so that a first edge 320 forms an outer convex bend 321 and the second edge 322 forms an inner convex bend 323 that fits therein and conforms to the internal curvature of the first edge 320. The inner bent section 323 has a generally curved shape and the terminal section 330 extends at the base of the inner bend 323, forming a D-shaped edge channel 332. The terminal section 330 has a straight leg 330.1 extending substantially in the thickness direction and a perpendicular foot 330.2 extending along the inner side of the bottom broad side 314, away from the inner convex bend 323. The leg 330.1 is positioned at the basis of the inner convex bend, against bend 334.

[0055] It remains to be noted that to strengthen the tube, the regions where two parts of the strip 11 lie against one another are conventionally bound together. This is the case at the first nose at the interface between the outer and inner convex bent sections, or also at the interface between the terminal section with other sections of the strip, and also at the fold 24. The binding is typically obtained by brazing. Therefore, the strip is cladded on both sides with a thin layer of brazing material.