GB2394037A

GB2394037A - Heat exchanger tube including tube inserts

Info

Publication number: GB2394037A
Application number: GB0305860A
Authority: GB
Inventors: William Machin; Toby Isenschmidt
Original assignee: Calsonic Kansei UK Ltd
Current assignee: Marelli Automotive Systems UK Ltd
Priority date: 2002-10-07
Filing date: 2003-03-14
Publication date: 2004-04-14
Anticipated expiration: 2023-03-14
Also published as: GB0223166D0; GB0305860D0; GB2394037B

Abstract

An insert 1 for a heat exchanger tube, has at least one limb dimensioned and shaped to extend into a tube (fig 3) adjacent to its longitudinal edge. The insert may comprise a pair of spaced apart limbs 2,3 extending in a common direction and connected by a connecting portion 8. The connecting portion may include a flow aperture 9 to permit fluid flow. The insert may include location means 6,7 for positioning within the tube at the required insert depth; such means may include indents or surface formations. The limb or limbs may include tapered, chamfered, or rounded portions 4,5 to aid insertion, and both the tube and insert may be of aluminium material. The insert may be bonded to the tube in the region of the tube open end, and the bonding process may be brazing. The insert may also be clad or coated with an aluminium brazing alloy, and may be press-formed from strip or sheet material. The insert may extend into the tube adjacent opposed longitudinal edges of the tube, and the connecting portion 8 may be positioned outside of the open end of the tube. The insert provides reinforcement for the tube, and both ends of the tube may be provided with the insert.

Description

Heat Exchangers 5 The present invention relates to heat exchangers, an in

particular, automotive heat exchangers, particularly (but not exclusively) heat exchangers of brazed aluminium construction. 10 A problem exists with certain automotive heat exchangers (radiators, condensers, eta) in that failure sometimes occurs on thermal shock testing. For certain heat exchangers, including aluminium brazed heat exchangers, this occurs as a result of fracture of the end heat 15 exchanger tubes (top and bottom in the tube array) at the region of bonding of the ends of the tubes at entry via a tube plate into the heat exchanger header tanks.

Known techniques to alleviate this problem have been to 20 increase the gauge of the tubes, use higher strength materials, or to cut the side casings of the heat exchanger assembly to reduce stresses induced by the side casings.

An improved arrangement has now been devised.

According to a first aspect, the present invention provides a heat exchange tube having opposed open ends, at least one of the open ends being provided with an insert having an insert limb extending into the tube adjacent a longitudinal 30 edge of the tube.

According to a second aspect, the invention provides a reinforcing insert for a heat exchanger tube, the insert having a limb shaped and dimensioned to extend into the

-2- tube adjacent a longitudinal edge of the tube.

It is preferred that the insert comprises a pair of spaced limbs extending in a generally common direction.

5 Beneficially the spaced limbs of the insert have terminal distal portions and the insert has a connecting bridge at a proximal end extending between the limbs. The connecting bridge portion may, in one embodiment, extend transversely to a substantially common plane in which the insert limbs 10 lie, the connecting bridge preferably including one or more flow apertures permitting fluid flow through the connecting bridge. In an alternative embodiment, the bridge portion may include a removable portion to be removed during or subsequent to fabrication of the heat exchanger, to leave 15 the tube end substantially unobstructed.

The insert beneficially includes one or more location formations or detents to aid in positioning the insert at the required insertion depth into the tube. Advantageously 20 one or both of the insert limbs includes a tapered, chamfered or rounded terminal portion to provide a 'lead in, aiding insertion into the heat exchanger tube.

It is preferred that the insert is bonded internally to the 25 tube, beneficially in a fusion bonding process (such as bracing for aluminium construction heat exchangers).

Advantageously a bonded connection is formed substantially along the entire length of the insert limbs extending in the tube.

It is preferred that the insert is of aluminium construction (preferably a pressed part from aluminium strip or sheet material). Beneficially the insert has a cladding or coating of an aluminium brazing alloy. The

-3 tube is also preferably of aluminium material (also preferably aluminium material clad with a brazing alloy).

According to a further aspect, the present invention 5 provides a method of manufacturing a heat exchanger using an insert as defined herein inserted into one or both open ends of a heat exchanger tube and subsequently bonded in place (typically in a fusion bonding process such as brazing for aluminium construction heat exchangers).

The invention will now be further described, by way of example only, and with reference to the accompanying drawings, in which: 15 Figure 1 is a perspective view of an insert in accordance with the invention; Figures 2a and 2b are side plan and end views of the insert of Figure 1; Figure 2c is a view on arrow A in Figure 2a; Figure 3 is a schematic view of the insert prior to insertion in a heat exchanger tube; Figure 4 is a schematic sectional view of the insert in position inserted in the tube; and Figure 5 is a plan view of an alternative embodiment of 30 insert in accordance with the invention.

Referring to the drawings, and initially to Figures 1 to 4, there is shown a tube insert 1 which is a pressed part formed from aluminium and having a brazing alloy cladding.

Brazing alloy clad aluminium components are known in the art of automotive heat exchanger manufacture. The insert 1 has a pair of spaced limbs 2, 3 extending in a generally common direction and includes terminal "lead in" tapered 5 ends 4, 5 to aid in insertion into the heat exchanger tube end. Each limb 2, 3 is formed having an outwardly projecting stop formations 6, 7 to aid in setting the insert at the required insert depth. The size of the stop formations 6, 7 is gauged to form an interference seating 10 fit with the open end of the tube into which the insert is inserted. A proximal bridge 8 interconnects the limbs 2, 3 which is formed to extend in a direction transverse to the general plane in which the limbs 2, 3 lie. In the embodiment shown, the bridge extends at an angle of 75 to 15 the general plane of the limbs 2, 3. The bridge 8 includes a central aperture 9.

As shown in Figures 3 and 4, the insert is inserted into the open end of the brazing alloy clad aluminium heat 20 exchanger tube 10 cleaning assembly prior to brazing. When inserted, the upper faces of the limbs 2, 3 lie contiguous with the upper internal will of the tube and the lower faces of the limbs 2, 3 lie contiguous with the lower internal wall of the tube 10. The outer edges of the 25 insert limbs 2, 3 lie contiguous with respective opposed internal longitudinal edges 11, 12 (nose edges) of the tube 10. In certain embodiments the outer edges of limbs 2, 3 may be rounded to correspond to the curvature of the internal longitudinal nose edges 11, 12 but in practice 30 adequate tube performance has been found to be achieved without this requirement.

The stop formations 6, 7 prevent over insertion of the insert and ensure a good enough mechanical fit for the

insert 1 to be securely positioned ready for the brazing process. When inserted, the bridge 8 is positioned outside the tube end and extends across the open end of the tube.

The aperture 9 permits fluid flow from the heat exchanger 5 header tank (not shown) into the tube via the aperture 9 in bridge 8.

Subsequently the heat exchanger assembly is brazed in a conventional manner.

In an alternative embodiment shown in Figure 5; the insert 101 is formed of flat strip or sheet and has a solid bridge 108 provided with a pair of break lines 121, 122 formed of perforations or reduced gauge lines. Subsequent to 15 brazing, the solid central piece 109 may be broken out (or alternatively burnt out during the brazing process) along the break lines 121, 122.

In either embodiment, the open ends of the heat exchanger 20 tube 10, 110 are not significantly obstructed in the finished, brazed heat exchanger product.

The invention provides that the tube longitudinal nose edges 11, 12 are locally reinforced in a region in which is 25 prone to fatigue failure on thermal shock cycling (in use) or testing. The use of higher gauge materials, or higher strength materials is therefore not required which has cost and weight savings, amongst other benefits.

Claims

-6 Claims:

1. A heat exchanger tube having opposed open ends, at 5 least one of the open ends being provided with an insert having an insert limb extending into the tube adjacent a longitudinal edge of the tube.

2. A heat exchanger tube according to claim 1, wherein 10 respective insert limbs extend into the tube through said open end adjacent opposed longitudinal edges of the tube.

3. A heat exchanger tube according to claim 2, wherein an 15 insert element comprises a pair of spaced limbs extending in a generally common direction, the spaced limbs extending adjacent opposed longitudinal edges of the tube in the region of the same open end of the tube, and a connecting portion extending transversely 20 between the spaced limbs.

4. A heat exchanger tube according to claim 3, wherein the connecting portion extends transversely to a common plane in which the insert limbs lie and 25 includes a flow aperture permitting fluid flow through the connecting portion.

5. A heat exchanger tube according to claim 3 or claim 4, wherein the connecting portion is positioned 30 outside of the open end of the tube.

6. A heat exchanger tube according to any preceding claim, wherein the insert includes locator means for positioning the insert correctly at the required

-7- insert depth into the tube.

7. A heat exchanger tube according to claim 6, wherein the locator means comprises a projection on one or 5 both of the insert limbs arranged to seat, abut or interference fit with the tube walls adjacent the open end of the tube.

8. A heat exchanger tube according to any preceding 10 claim, wherein one or both of the insert limbs includes a tapered, chamfered or rounded terminal portion to aid insertion of the insert into the open end of the tube.

15 9. A heat exchanger tube according to any preceding claim, wherein the insert is bonded to the tube in the region of the open end of the tube.

10. A heat exchanger tube according to any preceding claim 20 of generally aluminium construction, the tube insert being of aluminium and brazed to the tube in the region of the open end of the tube.

A heat exchanger tube according to any preceding 25 claim, wherein the or both limbs include opposed faces arranged to lie contiguously with upper and lower walls of the tube and an outer edge arranged to lie contiguously with the longitudinal internal nose edge of the tube.

12. A heat exchanger tube according to any preceding claim wherein the tube includes opposed open ends both provided with an insert having an insert limb extending into the tube adjacent a longitudinal edge

-8 of the tube.

A heat exchanger including one or more heat exchanger tubes according to any of claims 1 to 12.

14. A reinforcing insert for a heat exchanger tube, the insert having a limb shaped and dimensioned to extend into the tube adjacent a longitudinal edge of the tube. 15. A reinforcing insert according to claim 14 comprising a pair of spaced limbs extending in a generally common direction. 15 16. A reinforcing insert according to claim 15, wherein the spaced limbs of the insert have terminal distal portions and the insert has a connecting bridge at a proximal end extending between the limbs.

20 17. A reinforcing insert according to claim 16, wherein the connecting bridge extends transversely to a substantially common plane in which the insert limbs lie, the connecting bridge including one or more flow apertures permitting fluid flow through the connecting 25 bridge. 18. A reinforcing insert according to any of claims 14 to 17, wherein the insert includes one or more location formations or detents to aid in positioning the insert 30 at the required insertion depth into the tube.

19. A reinforcing insert according to any of claims 14 to 18, wherein one or both of the insert limbs includes a tapered, chamfered or rounded terminal portion.

-9- 20. A reinforcing insert according to any of claims 14 to 19, wherein the insert is generally of aluminium construction. 21. A reinforcing insert according to any of claims 14 to 20, wherein the insert has a cladding or coating of an aluminium brazing alloy.

10 22. A reinforcing insert according to any of claims 14 to 21, being an insert press formed from strip or sheet material. 23. A method of manufacturing a heat exchanger, including 15 inserting an insert according to any of claims 14 to 22 into the open end of a heat exchanger tube and bonding the insert in place in the tube.