WO2018053584A1

WO2018053584A1 - A heat exchanger and a component therefor

Info

Publication number: WO2018053584A1
Application number: PCT/AU2017/051023
Authority: WO
Inventors: Nelson Thomas; Nikolce Simonovski; Carl Morley; Kevin James Baensch
Original assignee: Air-Radiators Pty Ltd
Priority date: 2016-09-20
Filing date: 2017-09-20
Publication date: 2018-03-29

Abstract

A component (10) for a heat exchanger (60) includes an elongate tube portion (12). At least a portion (18) of the elongate tube portion (12) has an external surface (38, 40) which is substantially lens shaped in transverse cross section. A peripheral portion (14) is attached to the external surface of the tube portion (12). The peripheral portion (14) is in the form of coiled wire (42) which is wound in coiled turns (54) about the external surface (38, 40) of the tube portion (12).

Description

A heat exchanger and a component therefor

Field of the invention

The present invention relates to a component for a heat exchanger. In particular, although not exclusively, the invention relates to a component for a heat exchanger such as a water jacket cooler or a charge air cooler, for heavy duty applications such as underground mining. The invention also relates to a heat exchanger.

Background of the invention

Heat exchangers (otherwise known as radiators) are required for transfer of thermal energy from one medium to another for the purpose of cooling and heating. Cooling systems are required in connection with any machinery having an internal combustion engine or heat producing motor. The most demanding of conditions is in connection with machinery used off highway. Examples include dump trucks, loaders and other machinery used in mining. There are various performance criteria which heat exchanges must meet to be suitable for these conditions. The first criterion is adequate heat rejection relative to air side pressure drop. This performance criteria is generally expressed as the equation:

Q [kW] / dPe [Pa]

Where Q is heat rejection and dP is air side pressure drop.

It will be understood that a reduction in the airside pressure drop will lead to an overall improvement in performance. Pressure drop is the "work done" to achieve the output "heat transfer". So higher dPe will normally yield higher Q. But dPe requires fan power to pull the air through the radiator. Therefore a higher Q/dPe ratio is desirable as it gives more heat rejection for less work.

Additionally, heat exchangers in such environments must be able to withstand the rigours of the conditions including high vibration and acceleration. Additionally, the harsh environments tend to generate airborne particles including dust, dirt and grit which are invariably drawn through the radiator core by the radiator fan. Thus the surface of the radiator components facing upstream in the airflow will be most exposed to the flow of these airborne particles. Additionally, the arrangement of the radiator components should be such that they reduce clogging, particularly across the front of the radiator i.e. that which faces upstream towards the airflow. As a consequence of inevitable clogging, the radiator cores are generally "washed" under pressurised air in order to clean the front of thereof.

It is therefore an object of the present invention to provide a heat exchanger and a component therefore which goes at least some way to meeting the above performance criteria and/or provides a useful choice in the market for currently available heat exchangers. 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

In accordance with a first aspect of the present invention, there is provided a component for a heat exchanger, the component including: an elongate tube portion, at least a portion of which has an external surface which is substantially lens shaped in transverse cross section; and a peripheral portion attached to the external surface of the tube portion, the peripheral portion being in the form of coiled wire which is wound in coiled turns about the external surface of the tube portion.

Preferably, the lens shaped external surface of the tube portion is comprised of two arcs, convexed outwardly, which meet at two spaced vertices each of which have a radiused profile, whereby a ratio of the width of the widest point between the two arcs to the radius of at least one of the vertices is in the range of 5.3 to 9.6 or more preferably 5.6 to 8. Preferably, the radius of said one vertex is in the range of 0.6mm to 0.75mm. Preferably the radius of the other vertex is the same as said one vertex. The width of the widest point between the two arcs is preferably in the range of 4.0 to 4.8 or 4.2 to 4.8mm.

Preferably, the coiled turns are arranged substantially continuously about the tube portion, although there may be joins. Preferably, the coiled turns extends for a substantial portion of the length of the tube portion. The turns per meter is preferably in the range of 250 to 285, most preferably 268.

Preferably the arcs defining the external surface of the tube portion have the same or substantially the same radius of curvature. In a variation of the lens shape, the transverse cross section may be comprised of two curves which meet at vertices at each end.

The lens shaped cross sectional shape may be applied to the tube portion for the whole length and the tube portion may be of uniform cross section throughout its length. However, it is preferred that an intermediate portion between the end portions of the tube portion is of oblong shape in cross section, with the end portions of the tube portion being circular or round in cross section. This enables the round ends to engage with round holes in respective header plates in the heat exchanger. In a preferred form of the invention, the intermediate portion is formed by flattening a round tube to achieve the desired cross sectional shape.

Preferably, the tube is of metal such as copper or steel with desirable heat transfer properties. The central bore in the tube portion is to convey either water (in the case of a water jacket cooler) or air (in the case of a charge air cooler). Suitably, the tube portion has a substantially uniform wall thickness. Preferably the bore is an open lens shaped cross section without internal baffles or partitions.

The coiled wire is preferably copper. The coiled wire may be wound as repeating loops of substantially uniform shape. This uniform shape preferably has an inner flattened end for attachment to the tube portion. This flattened end is considered to be the inner extent of the coiled wire. Additionally, the shape of the repeating loops is substantially elongate from the flattened end to the outer extent of the coiled wire. In other words, the height of the loops above the tube portion is greater than the width of the loops. Additionally, the repeating loops are preferably curved on the outer extent. The loop height is in the range of 4.5 to 6 mm, preferably 5mm. The loop width is preferably in the range of 2.0 to 2.6mm, preferably 2.2 or 2.4mm.

The stacking of the loops is preferably closer on the flattened end (the inner extent) which is attached to the tube portion and more widely spaced at the outer extent. The stacking at the flattened end is preferably uniform as the coiled tube progresses around the tube portion and maximum stacking will ultimately depend upon the wire thickness. The preferred stacking is in the range of 74 to 140 loops per revolution around the tube portion, most preferably 102.

The attachment of the coiled wire to the tube portion is preferably achieved by means of a binding wire inserted through the repeating loops and engaging with the inside of the flattened end of the loops so that the flattened end is disposed between the external surface of the tube portion and the binding wire. The binding wire is suitably of substantially rectangular cross section.

The peripheral portion is arranged as repeated turns around the oblong shaped tube portion. Thus, the peripheral portion, i.e. the coiled wire, conforms to the oblong shape of the tube portion. Each turn around the tube portion may be spaced from the preceding turn. Preferably the spacing (gap) along the tube portion is uniform. During assembly, solder wire is arranged in the gap. The components are heated in an oven to melt the solder wire to secure the coiled wire onto the tube portion. The addition of solder assists heat transfer and mechanical strength. The solder used could have a melting point ranging from 180 degrees C to 330 degrees C. Alternately a form of brazing wire may be used with a melting point between 400 degrees C and 800 degrees C.

In accordance with a second aspect of the present invention, there is provided, a heat exchanger including a plurality of the components set out in the first aspect above.

Any of the features described above in accordance with the first aspect may be applied to the second aspect of the invention. The heat exchanger preferably includes upper and lower header tanks having upper and lower header plates respectively with each component having one end portion received in the upper header plate and the other end portion received in the lower header plate. Where the end portions of the tube portions are round then the holes in the header plate will suitably be round. At each interface between the end of the tube portion and the header plate, a grommet is preferably provided in the hole in the header plate. The grommet is inserted first into the hole, followed by the end of the tube.

In the heat exchanger, the plurality of the components are suitably arranged in rows which extend substantially perpendicularly to the intended direction of airflow through the heat exchanger. It is preferred that the smaller thickness dimension of the tube portion is substantially aligned with the row such that the tube portion presents its narrower dimension to the intended airflow direction. The rows of components are preferably spaced apart in the direction of intended airflow. Preferably, the placement of the components in each row is offset from the placement of the components in the adjacent rows. In other words, the placement of the components is a staggered array. For example, where there are two spaced components in the first row, a component in the second row will lie behind but in between the two components in the front row. Two components in the third row may lie substantially behind the two components in the front row and so on.

Preferably, support clips/brackets are provided to maintain the spacing of the components, to add stability to the core of components and reduce vibration of the core as a whole.

In accordance with a third aspect of the present invention, there is provided, a component for a heat exchanger, the component including: an elongate tube portion, at least a portion of which has an external surface which is oblong in transverse cross section; and a peripheral portion attached to the external surface of the tube portion, the peripheral portion being in the form of coiled wire which is wound in coiled turns about the external surface of the tube portion, wherein the wire has surface roughness. The preferred surface roughness is 1 -5μιη.

The surface roughness of the wire may formed by sand blasting of the

component. Alternatively, wire having a surface roughness may be employed in fabricating the component. Methods of achieving surface roughness may include mechanical means such as sand blasting or chemical means.

The cross sectional shape of the portion of the tube portion is suitably oblong, meaning that the height dimension of the cross section is greater than the width dimension. The tube portion may have a flattened shape which may be oval. In a most preferred form of the invention, the cross sectional shape is substantially lens shaped, in other words cat's eye or almond shaped.

In another form of the flattened shape, the cross section may be elliptical.

However, the tube shape need not be completely curved. A rectangular cross section is also possible. Also a stadium shape is possible.

Any of the features described above in connection with the foregoing aspects of the invention may be applied to this aspect.

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. 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.

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, one embodiment will now be described, by way of example with reference to the figures in which:

Figure 1 is a perspective view of a component for a heat exchanger in accordance with a preferred embodiment of the present invention;

Figure 2 is a side view of the tube portion of the component of Figure 1 , shown without the peripheral portions;

Figure 3 is a transverse section through A-A of Figure 2;

Figure 4 is a perspective view of the tube portion of Figure 2; Figure 5 is a cut through the tube portion of Figure 4;

Figure 6 is a detail of B of Figure 5;

Figure 7 is a cut through the component of Figure 1 showing the tube portion and the peripheral portion in greater detail;

Figure 8 is a transverse section through the component of Figure 1 showing the shape of the tube portion and the arrangement of the peripheral portion about the periphery of the tube portion;

Figure 9 is a schematic view showing a loop of the coiled wire forming the peripheral portion;

Figure 10 is an alternative transverse sectional shape for the tube portion of the component;

Figure 11 is an alternative transverse sectional shape for the tube portion of the components;

Figure 12 is a side view of the component of Figure 1 , Figure 13 is a plan view of the component of Figure 1 ; Figure 14 is a side elevation of a radiator core according to a preferred embodiment of the present invention;

Figure 15 is a top view illustrating the placement of the components in the radiator core of Figure 14;

Figure 16 is a perspective view of the radiator core of Figure 14;

Figure 17 is a perspective view, partially cut away, of the radiator core of Figure

16;

Figure 18 is a perspective view similar to Figure 16 but from a different perspective;

Figure 19 is an end elevation of the radiator core;

Figure 20 is a perspective view showing the centre support assembly for supporting the tubes in the radiator core;

Figure 21 is a plan view showing the centre support assembly of Figure 20;

Figure 22 is a perspective view of a single centre support bracket in a closed configuration;

Figure 23 is a perspective view of the single centre support bracket in an open configuration;

Figure 24 is a plan view of the single centre support bracket in a closed configuration;

Figure 25 is a plan view of the single centre support bracket in an open configuration;

Figure 26 is a perspective view of a first terminal block forming part of the centre support assembly;

Figure 27 is a plan view of the first terminal block forming part of the centre support assembly; Figure 28 is a perspective view of a second terminal block forming part of the centre support assembly;

Figure 29 is a plan view of the second terminal block forming part of the centre support assembly; and Figure 30 is an indicative diagram of pressure drop relative to a target pressure drop against ratio of the width of the widest point between the two arcs in a lens shaped profile (crown) to the radius of at least one of the vertices of the lens shaped profile. Both the internal pressure drop (dPi) of the fluid within the tube and the external air side pressure drop (dPe) are plotted; and Figure 31 is a diagrammatic plot, plotting heat rejection (Q) against external air side pressure drop (dPe).

Detailed description of the embodiments

Figure 1 is a perspective view illustrating a first preferred component 10 for a radiator 60 (see Figure 14), especially intended for heavy duty applications. The component 10 includes a tube portion 12 and a peripheral portion 14 comprised of coiled wires arranged in a coil about the tube portion.

Figures 2 and 3 illustrate the tube portion 12, without the peripheral portion. The tube portion 12 is comprised of a metal tube such as copper or steel. Suitably, the tube portion 12 has a bore 16 extending therethrough for flow of heat exchange fluid. In the case of a water jacket cooler, this fluid will be water. In the case of a charge air cooler, this fluid will be air.

The tube portion 12 has an intermediate flattened portion 18 that has been flattened by pressing to produce a flattened portion 18 which is flattened or oblong in transverse section. The round tube is preferably of 14.25mm diameter before being flattened. A second option is round tube with a 12.7mm diameter. With reference to Figures 10 and 1 1 , the meaning of "oblong" is that the height dimension H of the intermediate portion 18 of the tube portion 12 is greater than the width dimension W of the tube portion. Additionally, the tube portion 12 includes transition portions 20 defining transition zones between the flattened intermediate portion 18 and the outer end portions 22, 24 which are a circular transverse section. The end portion 24 is also provided with an annular rib 26. In the assembled radiator 60 shown in Figure 17, the components 10 are arranged in upright manner with the end portion 22 uppermost and the end portion 24 lowermost. Thus, the end portion 22 is received in the upper header plate 62, whereas the end portion 24 is received in the lower header plate 64. The annular rib 26 assists with locating the tube portion 12 in the lower header plate 64.

In Figure 5, a cut has been made through the tube portion 12 and the shape of the transverse section of the tube portion 12 is shown most clearly in Figure 6. The 2 dimensional external shape is approximately or substantially lens shaped defined by two arcs 30, 32 arranged with their convex surfaces disposed outwardly. The ends of the arcs 30, 32 meet at vertices 34, 36. However, these vertices 24, 26 are radiused. The tube portion is of substantially uniform wall thickness.

The preferred tube wall thickness is within the range of 0.3mm to 0.5mm and most preferably 0.4mm. The height H dimension is preferably in the range of 18 to 23mm or 18 to 20.5mm. The width W is preferably in the range of 4.0 to 4.8mm or 4.2 to 4.8mm. The radius at the vertices 34, 36 is preferably 0.6 to 0.75mm.

In 3 dimensions, the shape of the flattened portion 18 could be regarded as 2 partial cylinders 38, 40 which intersect, with the convex cylindrical surfaces 38, 40 disposed outwardly. Figures 7 and 8 illustrate the peripheral portion 14 in greater detail. The peripheral portion 14 is comprised of coiled wire 42. The coiled wire 42 is typically copper wire having a thickness/diameter in the range of 0.3 to 0.4mm. The coiled wire 42 is comprised of repeating loops 44 of uniform shape as shown in greater detail in Figure 9. Once formed, the coiled wire 42 is coiled or wrapped around the intermediate portion 18 of the tube portion 12 to form coiled turns. The technique of wrapping the coiled wire 42 around the lens shaped tube portion is similar to the known method of wrapping the coiled wire around a round tube as will be familiar to persons skilled in the field.

As shown in Figure 8 in particular, the individual loops 44 are closely stacked on the part-cylindrical sides of the flattened tube portion 18. Naturally, they are more closely spaced at the inner extent of the loops 44 and less closely spaced at the outer extent of the loops 44, as necessitated by the shape of the flattened tube portion 18. This is less obvious along the partial cylindrical portions 38, 40 and more exaggerated at the vertices 34, 36. While the loops per turn around the tube portion 12 will depend upon the wire diameter or thickness, it is preferred that the loops per turn will be in the range of 74 to 140.

Figure 9 illustrates the shape of the repeating loops 44. As already mentioned, the wire diameter or thickness WD is either 0.3 or 0.4mm, most preferably 0.355mm. The loop height, or in other words, the length between the inner extent and the outer extent FH, is preferably in the range of 4.5 - 6mm. This may vary according to application. The width of the loops is preferably in the range of 2.0 to 2.6mm.

It can be noted from Figure 9 that the outer extent of the loops extends in a curve 48. The sides of the loops are essentially straight as shown and the base of the loops (or the inner extent) 50 is also straight. The straight sided loops at the inner extent 50 facilitate with placement of the coiled wire 42 along the external surface of the flattened tube portion 18.

The attachment of the coiled wire 42 to the flattened tube portion 18 is facilitated by a binding wire 52 which runs through the repeating loops 44. On assembly, the binding wire 52 is seated internally against the base 50 of the loops 44. The binding wire 52 is tensioned to hold the coiled wire 42 in position, at least until soldering and thus assists with attachment of the coiled wire 42 to the tube portion 12. The binding wire is initially 0.7mm in diameter and which is flattened to 0.35 x 1 .1 BW (WxL).

Figures 12 and 13 illustrate how the coiled wire 42 is coiled about the flattened tube portion 18. As can be seen, the coiled wire 42 is arranged in repeating turns 54 about the flattened tube portion 18. The turns 54 are spaced apart by a uniform gap 56.

The component 10 is assembled with the turns arranged around the flattened intermediate portion 18. The turns 54 are arranged in a helical fashion about a longitudinal axis of the tube portion 10. The coiled wire 42 lies with the base 50 of the loops 44 in contact with the external surface of the flattened portion 18. The binding wire 52 holds the loops 44 in place with tension until solder is melted to form a joint. Soldering wire (not shown) is placed between the turns 54 into the gaps 56.

On one type of assembly machine, the solder wire is wound on at the same time as the binding wire 52 and the coiled wire 42. There is a heater adjacent to the winding mechanism which melts and sets the solder. On another type of machine, the process is identical except there is no heating element. In that case the wire 42 is tied off at the ends and the components 10 are put into an oven to melt and set the solder.

During heat treatment, the solder melts and fuses the coiled wire 42 and the binding wire 52 onto the flattened portion 18. Additionally, it has been found that surface roughness of the wire enhances performance of the components. This may be achieved by sandblasting the components or using wire roughened by mechanical or chemical means.

The number of turns per metre along the tube in the longitudinal direction is in the range of 250 to 285, most preferably 268. Figures 14 to 19 are views of an assembled radiator core 60 including upper header plate 62 and lower header plate 64. The components 10 extend between the upper and lower header plates 62, 64. The header plates 62, 64 each have an array of holes 68 which receive respective end portions 22, 24 of the tube portions 12. Additionally, grommets 70, the form of which is well known to those skilled in the art are received in the holes 68 and interface between the header plates 62, 64 and the end portions 22, 24, of the tube portions 12. Typically, the grommets 70 are inserted onto the tube portions 12 before the assembly is inserted into the lower header plate 64. As the components 10 are assembled in the radiator core 60, support clips or brackets 80 are inserted between adjacent components 10 to maintain the spacing of the components 10 as discussed below in connection with Figures 20 to 29. An assembly jig (not shown) may also be used to aid with assembly of the radiator core 60. When the components 10 are in position with grommets, the upper header plate 62 is assembled with the upper end portions 22 of the components 10.

The arrow C in Figure 15 defines the airflow through the radiator core 60. It can be seen that the components 10 are arranged in rows, each of which extend perpendicularly to the airflow direction C. The components are spaced apart along the rows. The spacing between adjacent components in the rows is preferably 22.86mm from centre to centre of the components. The spacing between the rows, the row pitch is preferably 33.3mm. Additionally, the rows are staggered so that for two adjacent components 80, 82 in the first row, a component 84 in the second row behind the first row will be offset perpendicularly to the direction of airflow C. In other words, the component 84 will lie behind the components 80, 82 but between the two components 80, 82, relative to the airflow direction C through the radiator core 60. The components 86 and 88 are also behind components 80 and 82 but offset perpendicular to the direction of airflow from the component in the immediately preceding row. The number of rows before repeating the pattern of the first row may be 4 or more. The stagger may be 33% or 50%.

From a consideration of Figures 14 to 19, it will be understood that the components 10 are presented to the upstream direction of the airflow C with the narrow dimension of the tube portions aligned with the direction of airflow C. This reduces the pressure drop through the radiator core 60 and hence improves the overall performance of the radiator core 60. The spacing of the components also reduces clogging and build-up of debris on the front of the radiator core 60 and thereby improves performance and minimises down time for maintenance. Additionally, it will be appreciated that airborne particles (not shown) which are typically present in heavy duty applications will be drawn through the radiator core 60 by the fan (not shown). These particles have an erosive effect on the components 10, particularly in the front row and particularly on the exposed edge of the components 10.

Prior art components (not shown) are arranged as a flattened tube with pleated fins on each of the wider longitudinal sides of the tubes, leaving the narrower longitudinal edge of the tube exposed to the erosive effect of the particles. In the arrangement illustrated in Figures 14 to 19, the upstream edge of the components 10 have an additional measure of protection by means of the peripheral portion 14 wrapping around the upstream edge of the tube portions 12. The peripheral portion 14 thus provides a measure of protection on the upstream edge and as a result the thickness of the tube portion 10 can be reduced. The thickness of the tube portion of 0.4 is less than the benchmark prior art product which is 0.635mm. The wrapping around the longitudinal upstream edge, the gathering of the loops 44 close to the external surface of the tube portion 10 and the presence of the binding wires 52 protects the upstream edge and also absorbs the energy of the particles impacting upon the upstream edge.

There are several considerations which need to be balanced to achieve optimum performance of the components. It was discovered that the lens profile could lead to improved performance over known profiles and in particular, certain dimensions of the lens shaped profile lead to optimum results. The shallow profiled upstream edge or "nose" reduces the air side pressure drop through the radiator core and hence brings about an overall increase in Q/dPe as a consequence of reduction of dPe and hence performance. Additionally, minimising the widest part of the lens shape will also reduce the air side pressure drop. This is desirable to decrease fan power since fan power is a cost factor. However, competing with this is the fact that minimising the widest part will lead to an unacceptable increase in internal pressure drop which may not be achievable with the given pump. Another factor to take into consideration is the amount of metal in the components. Sufficient metal is required to achieve the required thermal performance. Thus, the invention lies in determining the optimum profile characteristics in view of these and other competing factors. Figure 30 is an indicative diagram of normalised pressure drop against the ratio of the width of the widest point between the two arcs in a lens shaped profile (crown) to the radius of at least one of the vertices of the lens shaped profile. Both the internal pressure drop (dPi) of the fluid within the tube and the external air side pressure drop (dPe) are plotted. The plots were established by computational fluid dynamics. The plots show that for a pointed profile of the tube (meaning a small radius) you achieve minimum dPe (good) but a maximum dPi (bad). At the other end of the spectrum with a rounded profile (large radius) on an oblong tube with flat sides, you achieve maximum dPe (bad) and minimum dPi (good). Thus, to strike a balance between dPe and dPi, the ratio should be in the range of 5.3 to 9.6 and more preferably 5.6 to 8. For illustrative purposes, C was held constant in this plot. Figure 31 is a diagrammatic plot, plotting heat rejection (Q) against external air side pressure drop (dPe). This illustrates the effect of the varying the parameters on the overall key performance criteria of Q/dPe where being in the top left quadrant is the most desirable (good) and the bottom right quadrant is the least desirable (bad). Additionally, the shallow profile, particularly at or adjacent to the upstream vertex, means that less surface area is exposed to the airborne particles at or adjacent the upstream edge. This reduces damage to the tube portions and clogging of the components and radiators.

Figures 20 to 29 illustrate the form of the centre support assembly to support the core 60. Each component 10 has an associated centre support bracket 80 extending therearound. The brackets 80 are of the form shown in Figures 22 to 25 and are made of flexible plastic material to flex to an open configuration as shown in Figure 23 to extend around the component 10 and then clip closed around the component 10 as per Figure 22. The brackets 80 interconnect as shown in Figure 21 . Terminator blocks 82 and 84 as shown in Figures 26 to 29 are provided at the front and rear of the core 60 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 60 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 component for a heat exchanger, the component including: an elongate tube portion, at least a portion of which has an external surface which is substantially lens shaped in transverse cross section; and a peripheral portion attached to the external surface of the tube portion, the peripheral portion being in the form of coiled wire which is wound in coiled turns about the external surface of the tube portion.

2. The component as claimed in claim 1 wherein the lens shaped external surface of the tube portion is comprised of two arcs, convexed outwardly, which meet at two spaced vertices each of which have a radiused profile, whereby a ratio of the width of the widest point between the two arcs to the radius of at least one of the vertices is in the range of 5.3 to 9.6.

3. The component as claimed in claim 1 wherein the lens shaped external surface of the tube portion is comprised of two arcs, convexed outwardly, which meet at two spaced vertices each of which have a radiused profile, whereby a ratio of the width of the widest point between the two arcs to the radius of at least one of the vertices is in the range of 5.6 to 8.

4. The component as claimed in claim 2 or claim 3 wherein the radius of said one vertex is in the range of 0.6mm to 0.75mm.

5. The component as claimed in any one of claims 2 to 4 wherein the radius of the other vertex is the same as said one vertex.

6. The component as claimed in claim 2 or 3 wherein the width of the widest point between the two arcs is 4.2 to 4.8mm.

7. The component as claimed in claim 2 or 3 wherein the width of the widest point between the two arcs is 4.0 to 4.8mm.

8. The component as claimed in any one of claims 2 to 7 wherein the radiused profile of said one vertex is continuous with the arcs.

9. The component as claimed in any one of the preceding claims wherein the tube portion is of substantially uniform thickness.

10. The component as claimed in any one of the preceding claims wherein the tube portion thickness is in the range of 0.3 to 0.5mm.

1 1 . The component as claimed in any one of the preceding wherein the distance between the two vertices is 18 to 23mm.

12. The component as claimed in any one of the preceding claims wherein the tube portion comprises an open bore cavity which is lens-shaped in cross section.

13. The component as claimed in any one of the preceding claims wherein the coiled turns are substantially continuous for a substantial portion of the length of the tube portion.

14. The component as claimed in any one of the preceding claims wherein the coiled turns are arranged with the number of turns per meter in the range of 250 to 285.

15. The component as claimed in any one of the preceding claims wherein the coiled wire has repeating loops of substantially uniform shape having a flattened end for attachment to the tube portion and an outer extent.

16. The component as claimed in claim 15 wherein the loop shape has straight sides and a curved outer extent.

17. The component as claimed in claim 16 wherein the loop width between the sides is in the range of 2.0 to 2.6mm, preferably 2.4 or most preferably 2.2mm.

18. The component as claimed in any one of claims 15 to 17 wherein the loop height from the flattened end to the outer extent is in the range of 4.5 to 6mm, preferably 5mm.

19. The component as claimed in any one of claims 15 to 18 wherein the stacking of the flattened end on the tube portion is substantially uniform.

20. The component as claimed in any one of claims 15 to 19 wherein the stacking of the flattened end on the tube portion is uniform and in the range of 74 to 140 loops per revolution around the tube portion.

21 . The component as claimed in any one of the preceding claims wherein the wire thickness or diameter is in the range of 0.3 to 0.4mm, preferably 0.355mm.

22. A heat exchanger including a plurality of the components claimed in any one of the preceding claims.

23. The heat exchanger as claimed in claim 22 wherein the components are arranged between upper and lower header tanks, each component being separately removable from the heat exchanger relative to the other components.

24. The heat exchanger as claimed in claim 22 or 23 wherein the components are arranged in rows between upper and lower header tanks, the rows extending

substantially perpendicularly to the intended direction of airflow through the heat exchanger.

25. The heat exchanger as claimed in any one of claims 22 to 24 wherein the thickness dimension of the tube portion is substantially aligned with the row such that the tube portion presents its narrower dimension to the intended airflow direction.

26. The heat exchanger as claimed in any one of claims 22 to 25 wherein the rows of components are spaced apart in the direction of intended airflow with the placement of the components in each row being offset from the placement of the components in the adjacent rows.

27. A component for a heat exchanger, the component including: an elongate tube portion, at least a portion of which has an external surface which is oblong in transverse cross section; and a peripheral portion attached to the external surface of the tube portion, the peripheral portion being in the form of coiled wire which is wound in coiled turns about the external surface of the tube portion, wherein the wire has surface roughness.

28. The component as claimed in claim 27 wherein the surface roughness of the wire is 1 to 5 μιη.

29. The component for a heat exchanger as claimed in claim 27 or 28 wherein the surface roughness of the wire is formed by sand or grit blasting of the component.

30. The component as claimed in any one of claims 1 to 21 or the heat exchanger as claimed in any one of claims 22 to 26 wherein the wire has surface roughness of 1 to 5 μιη.