HEAT EXCHANGER AND COMPONENTS AND METHODS THEREFOR

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.

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 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 claim 1 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 claim 1 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 claim 1 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.

11. The method of constructing discrete tubular components as claimed in claim 5 wherein the substrate of the metal strip is a heat treatable metal.

12. The method of constructing discrete tubular components as claimed in 11 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 claim 1 wherein the second material is AL 4343.

15. The method of constructing discrete tubular components as claimed in claim 1 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 claim 1 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 16 wherein the array is held in compression during heating or brazing.

18. A discrete tubular component when produced by the method of claim 1.

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 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 claim 19 wherein the fin portions are dimpled or louvred.

23. The discrete tubular component as claimed in claim 19 wherein the metal strip includes work hardenable metal as the substrate.

24. The discrete tubular component as claimed in claim 19 wherein the metal strip includes heat treatable metal as the substrate.

25. The discrete tubular component as claimed in claim 19 wherein the tube portion comprises heat treatable metal.

26. The method of forming the discrete tubular component of claim 19 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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0069] 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:

[0070] FIG. 1 is a perspective view of a tubular component according to a preferred embodiment of the present invention;

[0071] FIG. 2 is a perspective view from another angle of the component in FIG. 1;

[0072] FIG. 3 is a detailed view of the tubular component of FIG. 1;

[0073] FIG. 4 is a perspective view illustrating a tube portion forming part of the tubular component of FIG. 1;

[0074] FIG. 5 is a longitudinal section across the width of the tube portion of FIG. 4;

[0075] FIG. 6 is a detailed view of A of FIG. 5;

[0076] FIG. 7 is an end view of the tube portion of FIG. 4, showing the uniform transverse cross-section, across the width and thickness;

[0077] FIG. 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;

[0078] FIG. 9 is a detail of L from FIG. 8;

[0079] FIG. 10 is a detailed G from FIG. 9;

[0080] FIG. 11 is a view similar to FIG. 8;

[0081] FIG. 12 is a detailed view of K from FIG. 11;

[0082] FIG. 13 is a detailed view of G from FIG. 12;

[0083] FIG. 14 is a perspective view of the stacking arrangement illustrated in FIGS. 8 and 11;

[0084] FIG. 15 is a detailed view of F from FIG. 14;

[0085] FIG. 16 is a side view of the stacking arrangement of FIG. 14;

[0086] FIG. 17 is an end view of the stacking arrangement of FIG. 16;

[0087] FIG. 18 is an exploded view showing the parts required to assemble a radiator in accordance with a preferred embodiment of the present invention;

[0088] FIG. 19 is an assembled view of the radiator of FIG. 18, with a cutaway; and

[0089] FIG. 20 is a detailed view of A from FIG. 19; and

[0090] FIG. 21 is a perspective view of an alternative form of tubular component according to a second preferred embodiment of the present invention;

[0091] FIG. 22 is a detailed view of a portion of the tubular component of FIG. 21;

[0092] FIG. 23 is a side view of a portion of the tubular component of FIG. 21;

[0093] FIG. 24 is an end view of the tubular component of FIG. 21;

[0094] FIG. 25 is an output from a finite element analysis showing stress concentrations of a prior art grommet under simulated operating conditions;

[0095] FIG. 26 is an output from a finite element analysis showing stress concentrations of a preferred grommet under simulated operating conditions;

[0096] FIG. 27 is an isometric view of the preferred grommet;

[0097] FIG. 28 is a plan view of the grommet in FIG. 27;

[0098] FIG. 29 is a bottom view of the grommet in FIG. 27

[0099] FIG. 30 is a cross-sectional view of the grommet in FIG. 29 taken along line A-A;

[0100] FIG. 31 is a cross-sectional view of the grommet in FIG. 29 taken along line A-A after insertion into a header plate; and

[0101] FIG. 32 is a cross-sectional view of the grommet in FIG. 29 taken along line A-A after insertion into a header plate and the subsequent insertion of a heat exchanger tube into the grommet;

[0102] FIG. 33 is a perspective view showing the centre support assembly for supporting the tubes in the radiator core;

[0103] FIG. 34 is a plan view showing the centre support assembly of FIG. 20;

[0104] FIG. 35 is a perspective view of a single centre support bracket;

[0105] FIG. 36 is a plan view of the single centre support bracket;

[0106] FIG. 37 is a perspective view of a first terminal block forming part of the centre support assembly;

[0107] FIG. 38 is a plan view of the first terminal block forming part of the centre support assembly;

[0108] FIG. 39 is a perspective view of a second terminal block forming part of the centre support assembly;

[0109] FIG. 40 is a plan view of the second terminal block forming part of the centre support assembly;

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0110] FIGS. 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 FIG. 3 with 2 flat longitudinal sides 14. Fin portions 16 are bonded to respective flat sides 14. As shown most clearly in FIG. 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.

[0111] FIGS. 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 FIG. 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.

[0112] Component Assembly

[0113] The construction of the tubular components 10 will now be described with particular reference to FIGS. 8-20.

[0114] 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 FIG. 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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 50-100 mm as shown in FIG. 14.

[0119] 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.

[0120] 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.

[0121] After brazing, the wires 44 are cut and removed. The brazed tubular components 10 should then separate easily from the spacers 38.

[0122] The strongbacks 36 are typically constructed from stainless steel 304-316 and are typically 25252 SHS.

[0123] The spacers 38 are typically the same material as the strong backs, being stainless steel 304-316 and are typically 1.2 mm sheet.

[0124] 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.

[0125] 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.

[0126] Heat Treatment

[0127] 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 Mg.sub.2Si in the tube portion alloy microstructure. The tubular components are air quenched after heat treatment until they return back to ambient temperature.

[0128] 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.

[0129] Heat Exchanger Assembly

[0130] FIG. 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.

[0131] 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 FIG. 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 110 is in the form described below in connection with FIGS. 25 to 32.

[0132] Side plates 62 are secured to the header tanks 52, 54 by means of fasteners 64.

[0133] FIGS. 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.

[0134] 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.

[0135] FIGS. 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.

[0136] Grommet

[0137] Reference is now made to FIGS. 27-29. FIG. 27 shows an isometric view of a preferred embodiment of the heat exchanger grommet 110. The grommet 110 includes an annulus of resiliently deformable material, said annulus defining a through bore 111. The bore 111 has first and second openings 112 and 113, with the bore 111 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 114 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 114 are connected by inner end wall surfaces 117 at opposing ends.

[0138] The overall shape of the grommet 110 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 112, the material surrounding the bore 111 is substantially equally distributed along the periphery of the bore 111. Likewise, at the second opening 113, the material surrounding the bore 111 is substantially equally distributed along the periphery of the bore 111.

[0139] FIG. 30 is a cross-sectional view of the grommet taken along section A-A of FIG. 29. Inner side wall surfaces 114 converge inwardly, in other words, are convex. The inner side wall surfaces 114 are illustrated as mirroring each other or being symmetrical about a central longitudinal plane of the grommet 110. In this embodiment, the smallest inner dimension is at a central depth between the first and second openings 112 and 113. 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 112 and 113. The inward convergence of inner side wall surfaces 114 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 114.

[0140] The inner side wall surfaces 114 may also be symmetrical about a plane at a central depth of the grommet 110. However, as shown in FIG. 30, the inner transverse dimension is greater at the opening 112 than at the opening 113.

[0141] FIG. 28 shows a plan view of the grommet 110. The inner end wall surfaces 117 may converge in the same manner as described above for the inner side wall surfaces 114 so that the cross-section is constant all the way around the periphery of the grommet 110. Alternatively, the inner end wall surfaces 117 may taper inwardly, such that the longitudinal dimension adjacent the first opening 112 is greater than the longitudinal dimension adjacent the second opening 113. FIG. 29 shows a bottom view of the grommet 110.

[0142] First and second outwardly extending flanges 115 and 116 are shown, with first outwardly extending flange 115 being the tube-side flange of the grommet 110, and the second outwardly extending flange 116 being the header-side flange. In this embodiment, the tube side-flange 115 has a greater bulk of material than the header-side flange 116. Inner edges 119, located between the top surface of tube-side flange 115 and inner side wall surfaces 114 are radiused to facilitate the insertion of the heat exchanger tubing.

[0143] Header-side flange 116 includes bevelled edges 118, located between the surface adjacent the second opening 113 of the header-side flange 116 and the peripheral edge of the header-side flange 116. This allows for easier insertion of the grommet 10 into the header plate.

[0144] In use, a grommet 110 would be situated at or adjacent both ends of the tubular components 10, meaning the grommet 110 is intended to be used in both orientations. In the orientation of FIG. 27 or 30, the grommet 110 would be inserted into a lower header plate 58, with a grommet 110 oriented in reverse orientation inserted in an upper header plate 56.

[0145] The tube-side and header-side flanges 115 and 116 define an annular groove 120 in the outer wall surface of the grommet 110. The annular groove 20 is adapted to receive a header plate 58. Tube-side flange 115 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 116 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.

[0146] FIG. 31 illustrates an embodiment of the grommet 110, 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 115, 116 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 115 compared to the header-side flange 116. This mitigates against pop-through of the grommet 110 on insertion of the tube 127. It is intended that the underside edge 121 of the tube-side flange 115 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 116 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 110 is accurately positioned in the header plate 58. This shape also increases the pop-out pressure by about 100 kPa over prior art grommets to 600 kPa.

[0147] FIG. 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 114 create a seal between the end portion 20 and the inner side wall surfaces 114 as well as a seal between the annular groove 120 and the header plate 58. Advantageously, the convex side wall surfaces 114 of the grommet 110 aids the material to absorb the cyclic loading experienced by the grommet 110 when in service. This occurs as the curved inner side wall surfaces 114 are compressed in the transverse direction of the grommet 110, leading to less displacement and/or flexure of the grommet material 110 at the flanges 115, 116. This results in the grommet 110 being in a substantially compressive loading state throughout service. This reduction or removal of large tensile loading in the grommet 110 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 FIGS. 31 and 32 that after the tube 10 is inserted into the grommet 110, 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 FIG. 32.

[0148] One suitable material for the grommet 110 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 110. Hydrocarbon, petrochemical and coolant resistance is also a desirable property of the material.

[0149] Suitably, the grommets 110 are injection moulded by compression or injection moulding.

[0150] FIG. 25 shows an example of a prior art heat exchanger grommet 1 of the kind shown in U.S. Pat. No. 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.

[0151] FIG. 26 shows a finite element analysis carried out on the present heat exchanger grommet 110. 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 110 can provide a more evenly distributed load along the sealing path of the grommet 110 and a heat exchanger tube 10 and the header plate 58.

[0152] FIGS. 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 FIGS. 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 FIG. 34. Terminator blocks 82 and 84 as shown in FIGS. 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.

[0153] 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.