EP3515630A1

EP3515630A1 - Heat exchanger and components and methods therefor

Info

Publication number: EP3515630A1
Application number: EP17851987.2A
Authority: EP
Inventors: Carl Morley; Nikolce Simonovski; Shashikiran Vatnal
Original assignee: Air Radiators Pty Ltd; Air-Radiators Pty Ltd
Current assignee: Air Radiators Pty Ltd; Air-Radiators Pty Ltd
Priority date: 2016-09-21
Filing date: 2017-09-20
Publication date: 2019-07-31
Also published as: WO2018053585A1; EP3515630A4; US20190249925A1; AU2017329245A1

Abstract

A method of constructing discrete tubular components (10) for a heat exchanger (50) includes providing a tube portion (12) having substantially flat sides (14). Additionally, a metal strip is provided which includes a substrate material (32) and a second material (34) different than the substrate material forming a layer in the strip. The second material (34) is provided on only one side of the metal strip. The strip is configured in repeated folds of peaks and troughs to form fin portions (16). The tube and fin portions are assembled to form an array (37) of multiple bundles of one of the tube portions with the fin portions (16) arranged on the substantially flat sides (14) of the tube portion (12) and the second material (34) of the strip facing the tube portion (12), and one or more spacers (38) disposed between adjacent bundles. The array (37) is heated to bond the second material (34) to the tube portion (12) in the region of the troughs of the fin portions (16). The array (37) is separated into the discrete tubular components with, in each case, fin portions (16) bonded to the substantially flat sides (14) of each tube portion (12) with the peaks of the fin portions being exposed.

Description

Heat exchanger and components and methods therefor

Field of the invention

The present invention relates to heat exchangers. In particular, although not exclusively, the invention relates to a heat exchanger having separable tubular heat exchanger components extending between the tanks. The invention also relates to a discrete tubular component for a heat exchanger and a method of constructing a discrete tubular component.

In particular, although not exclusively, the specification is also directed to aluminium tubular components for heat exchangers, particularly for heavy duty on-road and off-road applications. The inventions described herein may have application to air- to-air heat exchangers (charge air coolers) or liquid-to-air heat exchangers (water jacket coolers).

Background of the invention

Heat exchangers, particularly those used in vehicles and industrial machinery, come in a large variety tubing configurations, extending between a pair of header plates, between an inlet tank and an outlet tank.

A radiator is a common form of heat exchanger. Radiators are generally designed to have a high temperature coolant flow from an inlet tank within the radiator, through a set of finned tubes, and then to an outlet tank within the radiator. The coolant at the outlet tank is at a lower temperature than it was at the inlet tank. This cooling is mainly achieved through convection, wherein a cooler fluid, such as ambient air, passes over the surface of the tubes containing the heated coolant, and transfers away the thermal energy of the tubes.

As a result, cyclic stresses are induced in the tubing by expansion and contraction of the tubing in response to the changing temperature of the coolant and external fluid. In particular, the tubing may expand lengthwise.

Radiator cores generally come in a number of different types and the various different types each have their drawbacks. In monoblock cores, the tubes and fins are consolidated, with each tube being joined to an adjacent fin which is adjoined to the next tube and so on. One particular form of monoblock core is the bar and plate monoblock core. These constructions have tubes defined by bar and plate with inner fins inside the tubes. Additionally, external fins extend between adjacent plates. The brazed joints between the inner fins and the plate are critical for maintaining the structural integrity and performance. There are many brazed joints between the inner fins and the adjacent plates and thus bar and plate monoblock cores are typically prone to failure through failure of these braze joints.

Extruded tube monoblock cores have extruded baffles or fins located internally of the tubes and are therefore less prone to failure at the baffle/tube junctions. External fins are disposed between adjacent tubes. The braze between the external fin and the tube wall is critical for thermal performance. However, these braze joints are prone to failure through corrosion and erosion (such as by grit blasting in the field).

Additionally, all monoblock cores are prone to external clogging, especially at the front of the core, at the upstream side of the airflow direction through the core. Servicing of monoblock cores requires the removal of the whole core in order to clean or replace which induces significant vehicle down times.

An alternative to the monoblock core is the individual tube type cores where individual tubular components extend between the inlet tank and the outlet tank. US patent 3,391 ,732 assigned to Mesabi Cores Inc. exemplifies a radiator of this type. The individual tubular components are typically constructed of copper which is heavy and has a high initial cost and so is prohibitive in some applications. Additionally, the cooling fins are usually connected to the tube portions through the use of lead solder. Given the safety concerns in dealing with lead, lead solder is expensive to use. Lead solder also has a relatively low strength, is prone to corrosion, relatively poor conductivity and has a limited temperature range of applications e.g. less than 200 degrees C. Furthermore, the Mesabi tubular components are formed from tubes which have been flattened from round tubing, thus the end of the tube portions are still round. The production of flattened tubes from round tubes necessitates an additional working step to produce the tubes of required configuration and additionally presents the risk that the tubes will not be correctly installed in the radiator core. The correct installed position is with the flattened sides aligned with the direction of intended air flow through the core. However, the rounded ends facilitate the prospect of misalignment and require additional steps in order to guarantee correct alignment.

It is therefore an object of the present invention to provide a heat exchanger, components therefor and methods of constructing heat exchangers and components therefor which overcome or at least ameliorate at least one of the foregoing disadvantages. Another objective of the present invention is to provide the public with a useful choice over known products.

Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person in the art.

Summary of the invention Fins of single-sided metal strip

In accordance with a first aspect of the present invention, there is provided, a method of constructing discrete tubular components for a heat exchanger, the method including: providing a tube portion having substantially flat sides; providing metal strip which includes a substrate material and a second material different than the substrate material forming a layer on only one side of the metal strip; configuring the strip in repeated folds of peaks and troughs to form fin portions; assembling the tubes and fin portions to form an array of multiple bundles of one of the tube portions with fin portions arranged on the substantially flat sides of each tube portion and the second material of the strip facing the tube portion, with one or more spacers disposed between adjacent bundles; heating the array to bond the second material to the tube portion in the region of the troughs of the fin portions; and separating the array into the discrete tubular components with, in each case, fin portions bonded to the substantially flat sides of each tube portion with the peaks of the fin portions being exposed.

The second material is preferably in the form of a coating or cladding applied to the substrate material. The second material may be applied in a manner suitable for producing an adherent coating on the substrate material. For example, the metal strip may be rolled down from a composite billet of the substrate material and a sheet of the second material on one side.

The material for the substrate of the metal strip may be a work-hardenable alloy such as 3-series aluminium alloy, such as AL3003 with a melting point of approximately 660°C.

The tube portion preferably includes heat treatable metal and the method may further comprise a subsequent step of heat treating. The preferred material for the tube portion is heat treatable 6-series aluminium alloy, most preferably AL6063 with a melting point of approximately 660°C. The preferred metal for the substrate is also a 6- series aluminium allow, most preferably AL6063. Hence the same material could then be used for the substrate and the tube portion, enabling both the substrate and the tube portion to be heat treated.

Unlike monoblock cores which obtain their structural strength from being in a block, discrete tubular components need to be stronger individually to prevent damage during use and installation.

Preferably, the second material of the metal strip has a melting point range which is less than the melting point range of the substrate material and the tube portion. Preferably, the second material is a four series aluminium alloy, most preferably AL4343 having a melting point range of 577-600°C. AL4343 has been selected partly due to availability and partly because it has a high range of useful brazing temperatures. Alternatives include AL4045 and AL4047 and are possibly preferred where both the substrate and the tube portion are 6-series.

It is preferred that the heating of the second material is to a brazing temperature which exceeds the melting point of the second material. Where the melting point of AL 4343 is 577-600°C, then the range of suitable brazing temperatures is 590-610°C. Suitably, the brazing temperature is below the melting point of the tube portion and substrate material.

In a preferred form of the invention, a plurality of tubular components may be constructed by stacking the tubular components with one or more intervening spacer strips and then brazing the stack. Preferably the melting point of the spacer strips is higher than the brazing temperature. Preferably the spacers are stainless steel. Where the second material and the substrate material are aluminium, bonding to the stainless steel strip is prevented or at least unlikely or minimal. Furthermore, since the second material is only provided on the side of the metal strip contacting the tube portion, the metal strip should not bond to the spacer strip(s). In a most preferred form of the invention, the stacks are held in compression during brazing.

Thus, it will be understood that in using single-sided metal strip, heating of the array will only result in the metal strip being bonded to the tube portions in the region of the troughs. Accordingly, the peaks of the fin portions will be free or unconnected to the tube portion or any other part and will thus be exposed in the discrete tubular component.

The tubular components may be comprised of a tube portion and a fin portion. The tube portion is preferably an extruded section, most preferably aluminium. Preferably, the tube portion is not coated with brazing material, this being difficult to achieve given the extruded construction. Thus, it is preferred that the tube portion is of constant transverse section, throughout its length. Preferably, this transverse section is flat-sided with curved or arcuate ends. Preferably the height to width ratio is 7 or larger.

Additionally, the tube portion may be provided with internal baffles, more preferably two internal baffles. The internal baffles suitably extend longitudinally. Thus, the tube portion may be extruded with the integrally formed longitudinal baffles.

The or each fin portion may be arranged in any configuration relative to the flat sides of the tube portion. However, it is preferred that the fin portion extends longitudinally along the elongate tube portion. In particular, the tube portion may have a transverse section which is of oblong shape, defining two opposite substantially flat sides. It is preferred that there are two continuous fin portions which extend along respective flat sides.

The fin portion may be corrugated such as configured in serpentine or sinuous folds. Alternatively, concertina folds are also possible. Preferably, there is a regular pattern of peaks and troughs in the repeated folds and the peaks and troughs are of even height and spacing.

The fin portions may have a dimpled surface to improve heat transfer characteristics. Alternatively, the fin portions may include a series of louvred slots. In such louvred slots, the louvres are created from the planar material creating the fin portion. Creation of each louvre creates a consequent slot and the louvre lies out of the plane of the surrounding material. The louvres increase the air side pressure drop, enhance performance but lead to increased fouling of the core with debris. Alternatively, the fin portions may be plain with no dimples or louvres.

Any of the features described below in accordance with other aspects of the invention may have application to this aspect.

In accordance with a second aspect of the present invention, there is provided a discrete tubular component for a heat exchanger, the component including: a tube portion having substantially flat sides; and fin portions arranged on the substantially flat sides of the tube portion, each fin portion comprised of metal strip configured in repeated folds of peaks and troughs with one side of the metal strip facing the tube portion, the metal strip being substantially uniformly provided as a substrate material and a second material different to the substrate material, the second material forming a layer in the strip on only on said one side of the metal strip, the second material bonding the fin portion to the tube portion at the region of the troughs, wherein the peaks of the fin portions on each side of the tube are substantially exposed.

The second aspect of the invention may have any of the features described above or below in connection with other aspects of the invention. The metal strip may be configured in sections or long lengths which are then cut, to be subsequently positioned on the tube portion and placed in a controlled atmosphere brazing (CAB) furnace to heat the second material. Alternatively, it is possible to configure the strip metal progressively and place the folds onto the tube portion with the second material being progressively melted. For example, as each trough in the strip metal is formed, the second material may be contemporaneously heated to bond the metal strip to the tube portion.

Uniform flat tubes in staggered array

In accordance with another aspect of the present invention, there is provided, a heat exchanger including: a plurality of separable, elongate, tubular heat exchanger components, each component having end portions which have an external surface, the external surface being of oblong shape in transverse cross-section; and first and second header plates, the header plates having aligned apertures for receipt of the heat exchanger components which extend from the first header plate to the second header plate, wherein, for each tubular component, the corresponding aligned apertures in the first and second header plates are complimentary in shape to the external surface of the corresponding end portion of the tubular component, and wherein the tubular components are arranged in an array across the direction of intended air flow, with the tubular components in the array being arranged in a staggered pattern relative to the direction of intended air flow.

Thus, some components will be arranged behind others in the direction of intended airflow, with each component disposed behind its immediate forward neighbour such that it is offset sideways (i.e. in a direction perpendicular to the intended airflow). Preferably, the tubes are arranged in rows, the rows being evenly spaced along the direction of intended airflow. Additionally, the spacing of the tubes along each row may also be evenly spaced. When the tubes are arranged in rows, then each row may be staggered relative to its neighbouring rows. The repeat pattern before a row is positioned directly behind a preceding row may be two rows or more.

Preferably, the arrangement of the components which are oblong in transverse section is such that the lengthwise dimension of the section is arranged substantially aligned with the direction of intended airflow.

The tubular components may be comprised of a tube portion and a fin portion. The tube portion is preferably an extruded section, most preferably aluminium. Thus, it is preferred that the tube portion is of constant transverse section, throughout its length. Preferably, this transverse section is flat-sided with curved or arcuate ends. Preferably the height to width ratio is 7 or larger.

Preferably, the tubular components are able to be assembled separately with at least one of the header plates. The tubular components may be removable individually from at least one of the header plates. This allows for maintenance of individual components.

Preferably, the apertures in the header plates are commensurate in shape with the end portions of the tubes. However, each aperture may also accommodate a grommet which interfaces between the header plate and the end portion of the associated tube portion. The grommet may have any of the features described in connection with our Australian patent application filed 21 September 2016, for "Heat exchanger grommet", the contents of which are incorporated herein by reference.

Any of the features described above or below in connection with further aspects of the invention may have application to the present aspect.

Heat treatment

In accordance with another aspect of the present invention, there is provided, a tubular component for a heat exchanger, the component including: a tube portion including heat treatable metal; and one or more fin portions attached to the tube portion, the or each fin portion comprised of metal strip configured in repeated folds, the metal strip including a work hardenable metal. Any of the features described above in connection with the forgoing aspects of the invention may be applied to this aspect. Preferably the heat treatable metal in the tube portion is 6 series aluminium alloy. Preferably the metal strip includes a 3 series work hardenable alloy. Preferably, the tubular component is artificially aged at 178°C for 8 hours after the brazing of the components. In accordance with a fifth aspect of the present invention, there is provided a method of heat treating a tubular component for a heat exchanger, the tubular component including a tube portion including heat treatable metal, and one or more fin portions brazed to the tube portion, the or each fin portion including metal strip configured in repeated folds, the method including: heat treating the brazed tubular component.

Preferably the tube portion is heat treatable 6-series aluminium alloy.

The metal strip may include a work hardenable metal such as 3-series aluminium alloy. However, the metal strip may also comprise heat treatable 6-series aluminium alloy. Any of the features described in foregoing aspects of the invention may have application to the present aspects.

Grommet

In accordance with yet another aspect of the present invention, there is provided, a grommet for a heat exchanger including an annulus of resiliently deformable material, said annulus defining a through bore having opposite first and second openings, a depth, and transverse and longitudinal inner dimensions, the through bore having inner wall surfaces which converge inwardly, such that one or both of the inner dimensions vary through the depth of the bore, from one opening to the other, one or both of the inner dimensions being smallest in an intermediate portion of the bore disposed at an intermediate depth between the first and second openings, wherein the annulus further includes first and second outwardly extending flanges arranged to surround the first and second openings respectively. The grommet may be used in assembly with the components described above in the foregoing aspects.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps. Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.

Brief description of the drawings

In order that the invention may be more fully understood, some embodiments will now be described, by way of example, with reference to the figures in which:

Figure 1 is a perspective view of a tubular component according to a preferred embodiment of the present invention;

Figure 2 is a perspective view from another angle of the component in Figure 1 ;

Figure 3 is a detailed view of the tubular component of Figure 1 ; Figure 4 is a perspective view illustrating a tube portion forming part of the tubular component of Figure 1 ;

Figure 5 is a longitudinal section across the width of the tube portion of Figure 4; Figure 6 is a detailed view of A of Figure 5;

Figure 7 is an end view of the tube portion of Figure 4, showing the uniform transverse cross-section, across the width and thickness;

Figure 8 is a view of a portion of the stacking arrangement to construct a plurality of tubular components in accordance with the preferred embodiment of the present invention;

Figure 9 is a detail of L from Figure 8;

Figure 10 is a detailed G from Figure 9;

Figure 1 1 is a view similar to Figure 8; Figure 12 is a detailed view of K from Figure 1 1 ;

Figure 13 is a detailed view of G from Figure 12;

Figure 14 is a perspective view of the stacking arrangement illustrated in Figures 8 and 1 1 ;

Figure 15 is a detailed view of F from Figure 14; Figure 16 is a side view of the stacking arrangement of Figure 14;

Figure 17 is an end view of the stacking arrangement of Figure 16;

Figure 18 is an exploded view showing the parts required to assemble a radiator in accordance with a preferred embodiment of the present invention;

Figure 19 is an assembled view of the radiator of Figure 18, with a cutaway; and Figure 20 is a detailed view of A from Figure 19; and

Figure 21 is a perspective view of an alternative form of tubular component according to a second preferred embodiment of the present invention;

Figure 22 is a detailed view of a portion of the tubular component of Figure 21 ; Figure 23 is a side view of a portion of the tubular component of Figure 21 ;

Figure 24 is an end view of the tubular component of Figure 21 ;

Figure 25 is an output from a finite element analysis showing stress concentrations of a prior art grommet under simulated operating conditions;

Figure 26 is an output from a finite element analysis showing stress concentrations of a preferred grommet under simulated operating conditions;

Figure 27 is an isometric view of the preferred grommet;

Figure 28 is a plan view of the grommet in Figure 27;

Figure 29 is a bottom view of the grommet in Figure 27

Figure 30 is a cross-sectional view of the grommet in Figure 29 taken along line

A-A;

Figure 31 is a cross-sectional view of the grommet in Figure 29 taken along line A-A after insertion into a header plate; and

Figure 32 is a cross-sectional view of the grommet in Figure 29 taken along line A-A after insertion into a header plate and the subsequent insertion of a heat exchanger tube into the grommet;

Figure 33 is a perspective view showing the centre support assembly for supporting the tubes in the radiator core;

Figure 34 is a plan view showing the centre support assembly of Figure 20;

Figure 35 is a perspective view of a single centre support bracket;

Figure 36 is a plan view of the single centre support bracket;

Figure 37 is a perspective view of a first terminal block forming part of the centre support assembly; Figure 38 is a plan view of the first terminal block forming part of the centre support assembly;

Figure 39 is a perspective view of a second terminal block forming part of the centre support assembly; Figure 40 is a plan view of the second terminal block forming part of the centre support assembly;

Detailed description of the embodiments

Figures 1 and 2 illustrate the form of the tubular component 10 according to a preferred embodiment of the present invention. The tubular component 10 includes a tube portion 12. The tube portion 12 is oblong in transverse section as shown in Figure 3 with 2 flat longitudinal sides 14. Fin portions 16 are bonded to respective flat sides 14. As shown most clearly in Figure 3, the fin portions 16 are in the form of metal strip which has been folded, bent, corrugated or otherwise shaped into repeated folds 18 of troughs and peak. The folds 18 are sinuous in shape and are of equal height and equal spacing between the folds. The fin portions 16 extend for a substantial portion of the length of the tube portion 12. However, the fin portions 16 fall short of the ends of the tube portion 12 and define end portions 20 which are free of the fin portions on both sides 14.

Figures 4-7 show the form of the tube portion 12 in greater detail. The tube portion 12 is extruded from a heat treatable alloy AL6063. The extruded transverse section is illustrated in Figure 7. The transverse sectional shape is oblong having two flat sides 14 as mentioned. Additionally, the longitudinal edges 22 have a radiused outer periphery 24 to define respective noses 24. The tube portion 12 also has 2 internal baffles 26, dividing the internal bore of the tube portion 12 into three longitudinal passages 28. The wall thicknesses along the flat sides 14 is the thinnest wall thickness of the transverse section, as shown. The wall thickness of the internal baffles 26 is slightly greater. On the other hand, the wall thickness between each outer longitudinal passage 28 and the corresponding nose 24 is the thickest. This provides suitable protection for the tube portions 12 against the harsh conditions. In particular, the extra thickness in the tube portion 12 around the nose 24 guards against debris puncturing the tube. In the assembled heat exchanger, one of the noses 24 will face upstream of airflow and will be the most exposed to airborne particles as they travel through the heat exchanger core. Additionally, the upstream nose 24 will be subjected to pressure washing.

Component Assembly The construction of the tubular components 10 will now be described with particular reference to Figures 8-20.

As a first step, the extruded material is cut to length to form the tube portion 10. Additionally, the folded fin portions are also cut to length. At this point, it is to be noted that the fin portions are formed from metal strip 30, a portion of which is illustrated in Figure 10. The metal strip 30 includes a substrate 32 comprised of a substrate material, aluminium AL 3003 having a melting point of approximately 660°C. A second material 34 is provided as a coating or cladding on the substrate 32. The second material is AL 4343 which has a melting point range of between 577 and 600°C. Only one side of the substrate 32 is clad with the second material 34. Once the corrugated fin portion 16 has been cut to the required length, one fin portion 16 is placed on each flat side 14 of the tube portion 12. The fin portion 16 is placed on the tube portion 12 so that the cladding of the second material 34 is in contact with the tube portion 12. The other unclad side of the metal strip 30 should not be placed in contact with the tube portion 12. Otherwise, the cladding 34 will not bond to the tube portion 12 and will instead bond to the spacers 38.

The assembly order is as follows. Initially, a strongback 36 is placed on the bottom of the stack 37. The stack may be assembled in a suitable assembly jig (not shown). A first spacer 38 is placed on top of the strongback 36. The spacer 38 is a longitudinal strip of stainless steel. Each end of the strip has cut outs defining a central projecting portion 40. On each side of the central projecting portion 40, the strip has upstands 42. Each pair of upstands 42 is provided towards each end of the spacer 38 and the pairs are spaced apart a suitable distance to accommodate the fin portion 16 therebetween.

A combination of fin portion 16, tube portion 12 and fin portion 16 is then stacked on top of the first spacer 38 (otherwise referred to as a bundle or sandwich of fin, tube, and fin portions). A second spacer 38 is then placed in the inverted orientation on top of the upper fin portion 16. The end of the fin portion 16 should contact the upstand 42 as shown in the case of the lower fin portion 16. As noted above, the cladding 34 on the fin portions 16 is placed in contact with the tube portion 10. The unclad side of the fin portion 16 should be in contact with the spacers 38. Another spacer 38 is placed on top of the current stack in an upright manner. Then the stacking continues.

Once all of the fin portions 16, tube portions 10 and spacers 38 have been stacked, another strongback 36 is placed on top of the stack 37. The stack 37 is then strapped with a series of wires 44 to provide compression during the brazing process. Typically, the wire spacing is 50-100mm as shown in Figure 14.

Once the stack 37 is fully strapped and tensioned, it is ready for fluxing and brazing. The brazing is controlled atmosphere brazing (CAB). The stack is laid on its side to pass through the brazing furnace. The brazing occurs at temperatures in the range of 590-610°C. As the cladding 34 has a melting point in the range of 577 to 600°C, the cladding 34 will bond the fin portion 16 onto the tube portion 12. The brazing temperature range is below the melting point of the substrate material 32 and the material of the tube portions 12, both of which have a melting point of approximately 660°C. Thus, the cladding 34 is melted but not the substrate 32, nor the tube portion 12. It is also pointed out that the unclad side of the substrate 32 is in contact with the spacers 38. Accordingly, there should be no bonding between the fin portion 16 and the spacers 38.

After brazing, the wires 44 are cut and removed. The brazed tubular components 10 should then separate easily from the spacers 38. The strongbacks 36 are typically constructed from stainless steel 304-316 and are typically 25 x 25 x 2 SHS.

The spacers 38 are typically the same material as the strong backs, being stainless steel 304-316 and are typically 1 .2mm sheet. The cladding 34 is typically 10% single side cladding with aluminium alloy AL 4343. The cladding thickness is 10% of the material thickness of the fin material. Typically the fin material is 0.1 mm thick. So 10% of that means that the cladding thickness is 0.01 mm thick. The above description relates to aluminium components 10 with stainless steel strongbacks 36 and spacers 38. This combination of materials is chosen because of the low susceptibility of bonding under brazing conditions. Another combination could be copper tubular components with graphite strongbacks and spacers.

Heat Treatment The tubular components 10 are then artificially aged at 178°C for 8 hours. This heat treatment is expected to increase the strength of the extruded tube portion 12 which is made from AL6063 by promoting precipitation of Mg₂Si in the tube portion alloy microstructure. The tubular components are air quenched after heat treatment until they return back to ambient temperature. The result of the heat treatment is an increase in strength observed in the order of 30%, an increase in the hardness observed in the order of 45%. This equates to a temper close to the T6 condition.

Heat exchanger assembly

Figure 18 is an exploded view illustrating the components required to assemble a heat exchanger 50 in accordance with a preferred embodiment of the present invention. The heat exchanger 50 includes first and second tanks 52, 54. One is an inlet tank 52 and the other is an outlet tank 54. Both tanks 52, 54 have header plates 56, 58, one of which is shown more clearly in figure 20. The tubular components 10 extend between the header plates 56, 54 as is known in the art. Each end portion 20 is received in a respective aperture in the header plate 56, 58 with a respective grommet 60 provided at the interface between the end portion 20 and the header plate 56, 58. The grommets 60 may be of any suitable form known in the art. One preferred form is similar to the known grommets used for the Mesabi radiator discussed above, except that the form would be oblong instead of round with the Mesabi grommets. Another preferred grommet 1 10 is in the form described below in connection with Figures 25 to 32. Side plates 62 are secured to the header tanks 52, 54 by means of fasteners 64.

Figures 19 and 20 illustrate the arrangement of the tubular components 10 in the header plate 56. It can be seen that the tubular portions 10 are arranged in rows which extend along the length of the heat exchanger 50. These rows lie perpendicular to the direction of intended airflow Y through the heat exchanger. Each row is staggered relative to the row immediately in front of it. Thus, each tube portion is offset from its immediately adjacent tube portion in the row in front of it, the offset direction being perpendicular to the direction of intended airflow Y. In the configuration shown, the repeat pattern is 2. Additionally, it can be seen that the tubular components 10 are arranged with the length dimension of their oblong cross-section aligned with the direction of intended airflow Y.

Figures 21 -24 illustrate another embodiment for the tubular components 10'. In the tubular component 10', the fin portions 16' have been cut, either post-assembly with the tube portion 12, or post brazing, to define bevelled profiles 70 on the fin portions 16'. This brings about improvements in performance.

Grommet

Reference is now made to Figures 27-29. Figure 27 shows an isometric view of a preferred embodiment of the heat exchanger grommet 1 10. The grommet 1 10 includes an annulus of resiliently deformable material, said annulus defining a through bore 1 1 1 . The bore 1 1 1 has first and second openings 1 12 and 1 13, with the bore 1 1 1 having a depth, and transverse and longitudinal inner dimensions. The bore is elongate, and in this embodiment is depicted as being of an oblong shape, in particular of approximately stadium shape, with opposite inner side wall surfaces 1 14 extending in the longitudinal direction, defining a linear central portion of the oblong to approximately suit the shape of the heat exchanger tube. Inner side wall surfaces 1 14 are connected by inner end wall surfaces 1 17 at opposing ends.

The overall shape of the grommet 1 10 in this embodiment is reflective of the shape of the bore, that is, the shape of the grommet is of an oblong annulus. At the first opening 1 12, the material surrounding the bore 1 1 1 is substantially equally distributed along the periphery of the bore 1 1 1 . Likewise, at the second opening 1 13, the material surrounding the bore 1 1 1 is substantially equally distributed along the periphery of the bore 1 1 1 .

Figure 30 is a cross-sectional view of the grommet taken along section A-A of Figure 29. Inner side wall surfaces 1 14 converge inwardly, in other words, are convex. The inner side wall surfaces 1 14 are illustrated as mirroring each other or being symmetrical about a central longitudinal plane of the grommet 1 10. In this embodiment, the smallest inner dimension is at a central depth between the first and second openings 1 12 and 1 13. However, the smallest inner dimension need not be at a central depth. It may be at any intermediate portion between the first and second openings 1 12 and 1 13. The inward convergence of inner side wall surfaces 1 14 are depicted as being pronounced for illustrative purposes. However the degree of this convergence may vary. In practice, considerations such as the size and shape of the tubing, and the expected loading conditions the grommet is expected to encounter may influence the degree of convergence of the inner side wall surfaces 1 14.

The inner side wall surfaces 1 14 may also be symmetrical about a plane at a central depth of the grommet 1 10. However, as shown in Figure 30, the inner transverse dimension is greater at the opening 1 12 than at the opening 1 13.

Figure 28 shows a plan view of the grommet 1 10. The inner end wall surfaces 1 17 may converge in the same manner as described above for the inner side wall surfaces 1 14 so that the cross-section is constant all the way around the periphery of the grommet 1 10. Alternatively, the inner end wall surfaces 1 17 may taper inwardly, such that the longitudinal dimension adjacent the first opening 1 12 is greater than the longitudinal dimension adjacent the second opening 1 13. Figure 29 shows a bottom view of the grommet 1 10.

First and second outwardly extending flanges 1 15 and 1 16 are shown, with first outwardly extending flange 1 15 being the tube-side flange of the grommet 1 10, and the second outwardly extending flange 1 16 being the header-side flange. In this embodiment, the tube side-flange 1 15 has a greater bulk of material than the header- side flange 1 16. Inner edges 1 19, located between the top surface of tube-side flange 1 15 and inner side wall surfaces 1 14 are radiused to facilitate the insertion of the heat exchanger tubing.

Header-side flange 1 16 includes bevelled edges 1 18, located between the surface adjacent the second opening 1 13 of the header-side flange 1 16 and the peripheral edge of the header-side flange 1 16. This allows for easier insertion of the grommet 10 into the header plate.

In use, a grommet 1 10 would be situated at or adjacent both ends of the tubular components 10, meaning the grommet 1 10 is intended to be used in both orientations. In the orientation of Figure 27 or 30, the grommet 1 10 would be inserted into a lower header plate 58, with a grommet 1 10 oriented in reverse orientation inserted in an upper header plate 56.

The tube-side and header-side flanges 1 15 and 1 16 define an annular groove 120 in the outer wall surface of the grommet 1 10. The annular groove 20 is adapted to receive a header plate 58. Tube-side flange 1 15 has a substantially flat underside edge 121 . This surface is intended to be substantially parallel with an inner side 124 of the header plate 58 upon insertion. Similarly, header-side flange 1 16 has a substantially flat shoulder edge 122. This surface is intended to be substantially parallel with an outer side 125 of the header plate 58 upon insertion. Reference to 'inner' and Outer' in this context are references to the relationship with the radiator core being 'inner' and the header plates and tanks being 'outer'.

Figure 31 illustrates an embodiment of the grommet 1 10, after it has been inserted into a hole of a header plate 58. In this embodiment, the depth of the annular groove 120 is sized to accommodate the inner peripheral edge of the insertion hole 126, such that both the tube-side and the header-side flanges 1 15, 1 16 act as shoulders, and overlap the inner peripheral portion surrounding the insertion hole 126 of the header plate 58. There may be a greater overlap (i.e. greater footprint) from the flange over the inner peripheral portion in the case of the tube-side flange 1 15 compared to the header- side flange 1 16. This mitigates against pop-through of the grommet 1 10 on insertion of the tube 127. It is intended that the underside edge 121 of the tube-side flange 1 15 is in contact with the inner peripheral portion surrounding the insertion hole 126 of an inner side 124 of the header plate 58. Likewise, it is intended that shoulder edge 122 of the header-side flange 1 16 is in contact with the inner peripheral portion surrounding the insertion hole 126 of an outer side 125 of the header plate 58. In other words, preferably the depth of the annular groove 120 is substantially equal to the thickness of the header plate 58. The flat sides and sharp transition in the faces of the annular groove 120 provide positive insertion notification when the grommet 1 10 is accurately positioned in the header plate 58. This shape also increases the pop-out pressure by about 100kPa over prior art grommets to 600kPa.

Figure 32 shows the grommet 10 inserted into a hole of a header plate 58 with a tubular component 10 also inserted. The induced interference from the convex inner side wall surfaces 1 14 create a seal between the end portion 20 and the inner side wall surfaces 1 14 as well as a seal between the annular groove 120 and the header plate 58. Advantageously, the convex side wall surfaces 1 14 of the grommet 1 10 aids the material to absorb the cyclic loading experienced by the grommet 1 10 when in service. This occurs as the curved inner side wall surfaces 1 14 are compressed in the transverse direction of the grommet 1 10, leading to less displacement and/or flexure of the grommet material 1 10 at the flanges 1 15, 1 16. This results in the grommet 1 10 being in a substantially compressive loading state throughout service. This reduction or removal of large tensile loading in the grommet 1 10 is what allows it to withstand the loading conditions it experiences in service, without suffering from the same failure mode experienced by prior art grommets. It is noted from a comparison of Figure 31 and 32 that after the tube 10 is inserted into the grommet 1 10, the face 122 is no longer in contact with the outer side of the header plate 58 and is at a slight angle, as per Figure 32.

One suitable material for the grommet 1 10 is ELASTOSIL® R 756/50. It is a peroxide curing high consistency silicone rubber whose vulcanizates possess excellent resistance to hot air, good tear resistance, low compression set, resistance to hydrocarbon, and is highly elastic. The material is suitable for high temperature applications, as it is rated to withstand temperatures of 300°C for at least seven days when combined with a suitable stabiliser. The material is also able to withstand up to 270°C for extended periods of time up to the life of the radiator. Other materials possessing some or all of the above qualities may also be suitable for the grommet 1 10. Hydrocarbon, petrochemical and coolant resistance is also a desirable property of the material.

Suitably, the grommets 1 10 are injection moulded by compression or injection moulding. Figure 25 shows an example of a prior art heat exchanger grommet 1 of the kind shown in US patent 6,247,232. This grommet only has a tube side flange 3 in its natural unloaded configuration. In service, with the tube inserted into the header plate, a defacto flange 5 is created on the header side by deformation of the grommet material. Finite element analysis was carried out on this prior art grommet 1 , with simulated service conditions. Prior art grommets such as this suffer from the fact that under cyclic loading conditions experienced in service, forces transferred from the tubing to the grommet 1 lead to high tensile loaded areas, which the material of the grommet is not suitable for. This can be seen by the maximum stress concentration 7 in the defacto flange 5 on the header side. The loading leads to recurring displacement and/or flexure of the grommet material, outwardly and around the peripheral portion of the insertion hole of the header plate and to ultimate failure of the grommet 1 .

Figure 26 shows a finite element analysis carried out on the present heat exchanger grommet 1 10. The maximum stress 9 is a compressive load, which is absorbed by the material. The material the grommet is manufactured from is a material that performs well under compressive loading but relatively poor under tensile loading. This figure also shows that the grommet 1 10 can provide a more evenly distributed load along the sealing path of the grommet 1 10 and a heat exchanger tube 10 and the header plate 58.

Figures 33 to 40 illustrate the form of the centre support assembly to support the core 50. Each component 10 has an associated centre support bracket 80 extending therearound. The brackets 80 are of the form shown in Figures 35 and 36 and are made of flexible plastic material to flex to slide around the component 10. The brackets 80 interconnect as shown in Figure 34. Terminator blocks 82 and 84 as shown in Figures 37 to 40 are provided at the front and rear of the core 50 and interconnect with the front and rear rows of the brackets 80. The terminator blocks 82 and 84 are mounted to front and rear centre support bars (not shown). Hence the core 50 of components 10 are reinforced to increase rigidity and reduce vibration.

The forgoing describes only one embodiment of the present invention and modifications may be made thereto, without departing from the scope of the present invention.

Claims

1 . A method of constructing discrete tubular components for a heat exchanger, the method including: providing a tube portion having substantially flat sides; providing metal strip which includes a substrate material and a second material different than the substrate material forming a layer on only one side of the metal strip; configuring the strip in repeated folds of peaks and troughs to form fin portions; assembling the tubes and fin portions to form an array of multiple bundles of one of the tube portions with fin portions arranged on the substantially flat sides of the tube portion and the second material of the strip facing the tube portion, with one or more spacers disposed between adjacent bundles; heating the array to bond the second material to the tube portion in the region of the troughs of the fin portions; and separating the array into the discrete tubular components with, in each case, fin portions bonded to the substantially flat sides of each tube portion with the peaks of the fin portions being exposed.

2. The method of constructing discrete tubular components as claimed in claim 1 wherein the tube portions are extruded.

3. The method of constructing discrete tubular components as claimed in claim 1 or claim 2 wherein the metal strip is configured in lengths of troughs and peaks which are then cut and subsequently positioned in the array before the array is placed in a brazing furnace to heat the second material.

4. The method of constructing discrete tubular components as claimed in any one of the preceding claims wherein the heating is to a brazing temperature which exceeds the melting point of the second material and is below the melting point of the tube portion, the substrate material and the spacers.

5. The method of constructing discrete tubular components as claimed in any one of the preceding claims wherein the tube portion includes heat treatable metal and the method may further comprise a subsequent step of heat treating.

6. The method of constructing discrete tubular components as claimed in claim 5 wherein the tube portion is comprised of heat treatable 6-series aluminium alloy.

7. The method of constructing discrete tubular components as claimed in claim 6 wherein the tube portion is AL6063.

8. The method of constructing discrete tubular components as claimed in any one of the preceding claims wherein the substrate of the metal strip is a work- hardenable metal.

9. The method of constructing discrete tubular components as claimed in claim 8 wherein the substrate of the metal strip is a 3-series aluminium alloy.

10. The method of constructing discrete tubular components as claimed in claim 8 wherein the substrate of the metal strip is AL3003.

1 1 . The method of constructing discrete tubular components as claimed in any one of claims 5 to 7 wherein the substrate of the metal strip is a heat treatable metal.

12. The method of constructing discrete tubular components as claimed in 1 1 wherein the substrate of the metal strip is a 6-series aluminium alloy.

13. The method of constructing discrete tubular components as claimed in claim 12 wherein the substrate of the metal strip is AL6063.

14. The method of constructing discrete tubular components as claimed in any one of the preceding claims wherein the second material is AL 4343.

15. The method of constructing discrete tubular components as claimed in any one of the preceding claims wherein the spacers are arranged as elongate strips of stainless steel with upstands at each end to accommodate the adjacent fin portion(s) therebetween.

16. The method of constructing discrete tubular components as claimed in any one of the preceding claims wherein the array is initially arranged as a stacked arrangement of sandwiches of fin, tube and fin portions one atop the other, the sandwiches separated by one or more of the spacers.

17. The method of constructing discrete tubular components as claimed in claim

7 wherein the array is held in compression during heating or brazing.

18. A discrete tubular component when produced by the method of any one of the preceding claims.

19. A discrete tubular component for a heat exchanger, the component including: a tube portion having substantially flat sides; and fin portions arranged on the substantially flat sides of the tube portion, each fin portion comprised of metal strip configured in repeated folds of peaks and troughs with one side of the metal strip facing the tube portion, the metal strip being substantially uniformly provided as a substrate material and a second material different to the substrate material, the second material forming a layer in the strip on only on said one side of the metal strip, the second material bonding the fin portion to the tube portion at the region of the troughs, wherein the peaks of the fin portions on each side of the tube are substantially exposed.

20. The discrete tubular component as claimed in claim 19 wherein the tube is extruded.

21 . The discrete tubular component as claimed in claim 19 or 20 wherein there are 2 continuous fin portions extending along respective substantially flat sides of the tube portion.

22. The discrete tubular component as claimed in any one of claims 19 to 21 wherein the fin portions are dimpled or louvred.

23. The discrete tubular component as claimed in any one of claims 19 to 22 wherein the metal strip includes work hardenable metal as the substrate.

24. The discrete tubular component as claimed in any one of claims 19 to 22 wherein the metal strip includes heat treatable metal as the substrate.

25. The discrete tubular component as claimed in any one of claims 19 to 22 wherein the tube portion comprises heat treatable metal.

26. The method of forming the discrete tubular component of any one of claims 19 to 25 wherein the strip is configured progressively into peaks and troughs with the second material being progressively melted as the peaks and troughs are formed to bond the metal strip to the tube portion.