Header for heat exchanger   

Abstract: A header for a heat exchanger includes an elongate header plate having a pair of substantially parallel long edges. The header plate includes an elongate slot extending in a first direction across the header plate and a pair of ridges extending in a second direction along the header plate. The second direction is substantially perpendicular to the first direction. Edge regions of the header plate are formed on sides of the ridges adjacent the long edges. At least one of the edge regions lie in a first plane and crests of the ridges lie in a second plane. The first plane is substantially parallel to and offset from the second plane.

This application claims the benefit of United Kingdom Patent Application No. 1108977.8 filed May 27, 2011, the entire disclosure of which is hereby incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to heat exchangers, and more particularly to a header for a heat exchanger.

BACKGROUND OF THE INVENTION

Typically, automotive vehicles are provided with a cooling system for an engine including a heat exchanger such as a radiator, for example. When the engine is running, heat is transferred from the engine to a coolant that flows through the engine. The coolant then flows from the engine to the heat exchanger through a series of conduits. At the heat exchanger, heat is transferred from the coolant to cooler air that flows over the outside of the heat exchanger. This process repeats itself in a continuous cycle thereby cooling the engine.

A typical heat exchanger includes a series of tubes supported by two chambers or headers positioned at either end of the heat exchanger. One type of conventional header is a flat header. These are so named because, when these flat headers are joined to a respective tube, for example, by brazing, the joint between the header and the tube lies in a substantially flat plane.

During operation of the engine and cooling system, the tubes are subject to thermal cycling (rise and fall of the temperature of the heat exchanger components). The thermal cycling leads to stresses as adjacent tubes may expand to different degrees, imposing axial loads on adjacent tubes. These types of header/tube combinations are, therefore, prone to failure because of the stress concentrations that occur along the header/tube joint. In particular, these designs of header are prone to failure around a nose of the tubes.

A different header, designed to overcome these problems is disclosed in U.S. Pat. No. 7,426,958. However, when used in heat exchangers including folded tubes, or ‘B-tubes’, having a longitudinal seam separating two channels, the failure point is known to have moved from the nose of the tube to the intersection of the seam of the tube with the header.

It is, therefore, an object of the present invention to provide an improved heat exchanger header that overcomes the above problems.

SUMMARY

In concordance and agreement with the present invention, a header for a heat exchanger of the present invention, has been surprisingly invented.

In one embodiment, a header for a heat exchanger comprises: a header plate having a first surface, an opposing second surface, and substantially parallel edges, the header plate including: at least one slot formed in the header plate and extending in a first direction across the header plate; a plurality of ridges extending in a second direction along the header plate, the second direction being substantially perpendicular to the first direction; and a plurality of edge regions adjacent the edges, wherein the at least one slot extends across the ridges, and wherein at least one of the edge regions of the header plate lie in a first plane and at least one crest of at least one of the ridges lies in a second plane, and wherein the first plane is substantially parallel to and offset from the second plane, the second plane disposed further from the second surface of the header plate than the first plane.

In another embodiment, a heat exchanger comprises: at least one tube including a seam extending along a central region of the at least one tube; and a header including a header plate having a first surface, an opposing second surface, and substantially parallel edges, the header plate including: at least one slot having a first end and a second end, the slot extending in a first direction across the header plate; a plurality of ridges extending in a second direction along the header plate, the second direction being substantially perpendicular to the first direction; and a plurality of edge regions formed on sides of the ridges adjacent the edges of the header plate, wherein at least one of the ends of the at least one slot is located within the edge regions, and wherein the at least one slot extends across the ridges, and wherein the edge regions of the header plate lie in a first plane and at least one of a plurality of crests of the ridges lie in a second plane, and wherein the first plane is substantially parallel to and offset from the second plane, the second plane located further from the second surface of the header plate than the first plane, and wherein an end of the at least one tube is received within the at least one slot and the seam of the at least one tube is substantially aligned with a central region of the header plate, and wherein at least one of the crests of at least one of the ridges intersects the at least one tube further from the end of the at least one tube than the edge regions of the header plate.

In yet another embodiment, a heat exchanger comprises: at least one tube; and a header including a header plate having a first surface, an opposing second surface, and substantially parallel edges, the header plate including: at least one slot extending in a first direction across the header plate; a plurality of ridges extending in a second direction along the header plate, the second direction being substantially perpendicular to the first direction; a plurality of edge regions formed on sides of the ridges adjacent the edges of the header plate, wherein the edge regions of the header plate lie in a first plane and at least one of a plurality of crests of the ridges lie in a second plane, and wherein the first plane is substantially parallel to and offset from the second plane, the second plane located further from the second surface of the header plate than the first plane; and at least one trough formed between the ridges.

Preferably, the header plate includes a trough between the two ridges and the seam of the tube coincides with a base of the trough.

Typically, the header comprises more than one slot and the slots are arranged parallel to each other. Preferably, the first direction is perpendicular to the long edges of the header plate, such that when a tube is inserted in the one or more slots the width of the tube extends across the width of the header.

Preferably, the header has mirror symmetry along a longitudinal centre line of the header so that the two edge regions are of equal width. In this way, a first distance between the crest of a first ridge and a first long edge of the header plate, and a second distance between the crest of a second ridge and a second long edge of the header plate are equal.

In preferred embodiments, the thickness of the header plate is constant over the whole area of the header plate such that the stiffness of the header plate does not vary significantly over its area.

In some designs of heat exchanger it may be desirable if the depth of a trough formed between the two ridges in the header plate is equal to the height of the ridges. As such a base of the trough and the two edge regions of the header all lie in the first plane.

In other designs of heat exchanger it may be desirable if the depth of a trough formed between the two ridges in the header plate is less than the height of the ridges. As such, a base of the trough lies in a third plane, parallel to the first and second planes and located between the first and second planes.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiment when considered in the light of the accompanying drawings in which:

FIG. 1 is a schematic front elevational view of a heat exchanger, as is known in the prior art, including a header and a plurality of tubes;

FIG. 2a is a perspective view of a portion of the heat exchanger illustrated in FIG. 1 showing a connection between one of the tubes and the header, the header being of a geometry known in the prior art;

FIG. 2b is a cross-sectional view of the portion of the heat exchanger illustrated in FIG. 2a, taken along section line II-II of FIG. 2a;

FIG. 3a is a perspective view of a portion of a heat exchanger illustrated in FIG. 1 showing a connection between one of the tubes and the header, the header being of a geometry known in the prior art;

FIG. 3b is a cross-sectional view of the portion of the heat exchanger illustrated in FIG. 3a, taken along section line III-III of FIG. 3a;

FIG. 4a is a perspective view of a portion of a heat exchanger showing a connection between one of a plurality of tubes and a header according to an embodiment of the present invention;

FIG. 4b is a cross-sectional view of the portion of the heat exchanger illustrated in FIG. 4a, taken along section line IV-IV of FIG. 4a;

FIG. 5 is a cross-sectional view of a portion of a heat exchanger, having a header according to a further embodiment of the present invention; and

FIG. 6 is a cross-sectional view of a portion of a heat exchanger, having a header according to a yet another embodiment of the present invention.

DETAILED DESCRIPTION

The following detailed description and appended drawings describe and illustrate various embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner.

FIG. 1 illustrates a known heat exchanger 10, which in this example is part of an automotive radiator assembly. The heat exchanger 10 includes a plurality of tubes 12 extending between two headers 14, 16 connected to a first end 18 and a second end 20 of the tubes 12. The tubes 12 extend parallel to each other and are joined at the first or second ends 18, 20 to adjacent tubes such that a fluid flow path is established through the heat exchanger 10. A number of fins 22 are arranged to span the spaces between the adjacent tubes 12 in an orientation such that, in use, air is able to flow over the surface of the fins 22 and between the tubes 12.

During operation of an engine (not shown) connected to the heat exchanger 10, heated coolant from the engine flows through the tubes 12 and transfers heat energy from the coolant to walls of the tubes 12. The heat energy is, in turn, transferred to the fins 22 which radiate the heat energy, aided by a flow of cool air over and around the fins 22. Cooled coolant then flows back into the engine to complete the cycle.

FIGS. 2a and 2b show a prior art configuration of the tube 12 and the header 14 used in the heat exchanger 10. The configuration of the header 14 shown in FIGS. 2a and 2b is known as a flat header 14 because a joint 24 between the tube 12 and the header 14 lies in a substantially flat plane 26. Typically, the tube 12 and the header 14 are formed from an aluminium material and the joint 24 between the tube 12 and the header 14 is brazed.

As the coolant flows through the heat exchanger 10 and transfers the heat energy to the tubes 12 and to the surrounding air, the components of the heat exchanger 10 undergo thermal cycling due to a rise and a fall of a temperature thereof. Furthermore, a difference in the temperature is often created across a width of the tube 12 and between adjacent tubes 12 because the coolant cools as it flows across the heat exchanger 10. The difference in the temperature causes the adjacent tubes 12 to expand and contract to different degrees, which in turn leads to axial stresses being imposed on the tubes 12.

The externally induced stresses typically act along a whole of the joint 24 between the tube 12 and the header 14 due to a restriction in a deformation of the tubes 12 in this region caused by the header 14. Furthermore, due to a geometry of the joint 24, stresses are concentrated at the ends 28 of the tube 12, known as a nose 28 of the tube 12. Stress concentration is a physical property and is related to the geometry of the tube /header joint 24. Stresses are, therefore, concentrated in a region of the nose 28 due to a change in the geometry and a small radius of curvature of this part of the tube 12. As such, failure of the heat exchangers 10 shown in FIGS. 2a and 2b usually occurs by radial fracture at or near an intersection of the nose 28 of the tube 12 with the header 14.

One design of the header 14 used to overcome the above problem is disclosed in U.S. Pat. No. 7,426,958. As shown in FIGS. 3a and 3b, the header 114 includes a raised central portion 102 so that the header 114 has a substantially trapezoidal cross sectional shape. The raised central portion 102 of the header 114 lies in a second plane 152 parallel to and offset from a plane 126 which includes edge regions 146 of the header 114. The geometry of header 114 distributes stresses more evenly over a joint 124 between a tube 112 and the header 114, thereby increasing a life of the header 114. In particular, the raised central portion 102 alters a distribution of stress along the joint 124. The stresses caused by a twisting of the header 114 and a bending of the tubes 112 during thermal cycling is now within the raised central portion 102 of the header 114, and therefore separated from regions of greatest stress concentration around a nose 128 of the tube 112.

Reference is now made to FIGS. 4a and 4b. In other designs of heat exchangers, it is increasingly desirable to use folded tubes 212 having a cross-section generally in the shape of a “B”. In certain embodiments, the tubes 212 are formed from sheet metal and folded to create a central seam 230 which is then brazed to seal the tube 212. The tube 212 increases the heat transfer surface area of the tube 212, thereby increasing an efficiency of the heat exchanger (not shown). In addition, the tubes 212 have increased strength while allowing a use of thinner and lighter materials in a construction thereof.

However, the seam 230 increases a rigidity of the tube 212 in a central region 232. The tube 212 is, therefore, less flexible to accommodate stresses caused by thermal cycling. When the tubes 212 are inserted into a flat header 14, as described above, an additional potential point of failure is then created at an intersection of the seam 230 of the tube 212 and the header 14. Furthermore, if the tube 212 is used in combination with a trapezoidal header 114 described above, the problem is exacerbated as a location of the seam 230 coincides with a region of greatest loading in the central portion 102.

FIGS. 4a and 4b show a part of the tube 212 and the header 214 according to an embodiment of the present invention. The tube 212 has a folded design provided with the central brazed seam 230, as described above. The header 214 includes a header plate 234 having a first face such as an upper face, for example. The header plate 234 has a substantially rectangular shape and includes two opposing longer edges 236a, 236b and two opposing shorter edges (not shown). A series of slots 238 for receiving a first end 218 (shown in FIG. 4b) of each of the tubes 212 is formed in the header plate 234. The slots 238 extend across almost a full width of the header 214. A length of the slots 238 is perpendicular to a longitudinal axis 240 of the header 214.

The header 214 may also include a second face (not shown), opposing the first face of the header plate 234. In certain embodiments, the second face forms a base of the header 214. Four side walls, portions of two of which 242a, 242b are shown, extend between the first face and the second face around a periphery of the first face 234 and the second face, thereby forming an enclosed volume within the header 214.

Typically, the header 214 is made from a suitable metal such as an aluminium or steel, for example. The header 214 may be provided with any number of the slots 238 for receiving the tubes 212. In certain embodiments, the header 214 includes between six and two hundred slots 238. As a non-limiting example, a spacing between the slots 238 is about 4 mm to 15 mm and each of the slots 238 is about 1 mm to 12 mm wide. A length of the slots 238 can vary from 10 mm to 110 mm, depending on an application of the heat exchanger. Once the tube 212 has been positioned in a respective one of the slots 238, the tube 212 can be fixed in position by brazing, soldering, or other suitable joining means as desired.

The header plate 234 of the header 214 includes two ridge portions 244 thereby forming a corrugated profile to the header plate 234. The ridges 244 extend longitudinally along a full length of the header plate 234. The slots 238 cut perpendicularly across the ridges 244 such that a line of intersection between the tube 212 inserted into the slot 238 and the header plate 234 do not lie in a single plane.

As shown most clearly in FIG. 4b, edge regions 246a, 246b of the header plate 234 lie in a first plane 248 and crests 250 of the ridges 244 lie in a second plane 252 parallel to and offset at a distance from the first plane 248. In a non-limiting example, the crests 250 of the ridges 244 are raised at a distance from the first plane 248 such that the crests 250 intersect the tube 212 further from the end 218 of the tube 212 which is located within the header 214.

In the embodiment shown, the ridges 244 are dimensioned and positioned such that the crests 250 intersect the tube 212 at points approximately one quarter and three quarters of the way across a width of the tube 212. A trough 254 formed between the two ridges 244 is aligned with the central portion 232 of the tube 212 so that a base 256 of the trough 254 coincides with the seam 230 of the tube 212. In certain embodiments, a depth of the trough 254 between the ridges 244 is such that the base 256 of the trough 254 lies at a point between the first plane 248 and the second plane 252. In other embodiments, the base 256 of the trough 254 may lie in the first plane 248.

The ridges 244 shown are formed from a number of substantially planar sections. In particular, the crests 250 of the ridges 244 and the base 256 of the trough 254 are formed by substantially planar sections extending parallel to the first plane 248 and perpendicular to the seam 230 of the tube 212. Sides of the ridges 244 are also formed from substantially planar sections. In a non-limiting example, the sides of the ridges 244 are at an angle of between 20° and 70° to the first plane 248.

FIGS. 5 and 6 show additional embodiments of the invention. In

FIG. 5, crests 450 of ridges 444 are formed from substantially planar or flat sections of a header plate 434 and lie in a second plane 452. Outer side portions 462 of the ridges 444, extending between one of opposing long edges 436a, 436b and the crest 450 of a respective one of the ridges 444, are formed from substantially curved sections of the header plate 434. In a non-limiting example, an upper surface 464 of the header plate 434 has a substantially concave curvature in respect to the second plane 452. A trough 454 between the two ridges 444 is formed from a continuously curved section of the header plate 434, with an upper surface 464 having a concave curvature in respect to the second plane 452.

In FIG. 6, edge regions 546a, 546b of a header plate 534 lie in a first plane 548, as in the embodiment of the invention shown in FIG. 4b. A base portion 556 of a trough 554 is formed from a substantially planar or flat section of the header plate 534 aligned with a central portion 532 of a tube 512. Ridges 544 in the header plate 534 are formed from continuously curved sections such that an upper surface 564 of the header plate 534 is convex in respect to the first plane 548.

In the embodiments of the invention described above, it is important that a point of intersection of the tube 212, 412, 512 with the respective header plate 234, 434, 534 is located closer to an end of the tube 212, 412, 512 in regions around a nose of the tube 212, 412, 512 and adjacent to the seam of the tube 212, 412, 512 than in regions therebetween.

Larger stresses, caused by twisting of the header and bending of the tubes 212, 412, 512 due to thermal cycling, are imparted to the joint between the header and the tube 212, 412, 512 at greater distances from the end of the tube 212, 412, 512 because the tube 212, 412, 512 is able to deform to a greater degree due to a difference in temperature further from the header. Closer to the header, deformation is restricted due to the fixed joint between the tube 212, 412, 512 and the header plate 234, 434, 534.

In this way, the ridged profile of the header plate 234, 434, 534 according to the present invention separates regions of higher loading, i.e. regions of intersection further from the end of the tube 212, 412, 512, from regions of higher stress concentration, i.e. regions of small radius of curvature around the nose of the tube 212, 412, 512, and regions of increased rigidity adjacent the seam of the tube 212, 412, 512.

The present invention, therefore, provides an improved header for use in folded-tube heat exchangers that maximizes life span as compared with current designs of the header.

From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, make various changes and modifications to the invention to adapt it to various usages and conditions.